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  • 1
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    Acoustic and Elastic Wave Fields in Geophysics, II (2002)
    Elsevier
    In:  Amsterdam, 530 pp., Elsevier, vol. 37, no. XVI:, pp. 227-235, (ISBN 0231-12739-1 hb, 0231127383 pb)
    Details
    Publication Date: 2002
    Keywords: Seismics (controlled source seismology) ; Applied geophysics ; Wave propagation ; Waves ; Textbook of geophysics ; Acoustics ; Fluids ; High frequency ... ; Kirchoff ; seismic Migration ; Layers ; Channel waves
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    BIBLIOGRAPHY SEISMOLOGY
  • 2
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    Transient Reliability of Ceramic Structures For Heat Engine Applications (2002)
    In:  CASI
    Details
    Publication Date: 2004-12-03
    Description: The objectives of this report was to develop a methodology to predict the time-dependent reliability (probability of failure) of brittle material components subjected to transient thermomechanical loading, taking into account the change in material response with time. This methodology for computing the transient reliability in ceramic components subjected to fluctuation thermomechanical loading was developed, assuming SCG (Slow Crack Growth) as the delayed mode of failure. It takes into account the effect of varying Weibull modulus and materials with time. It was also coded into a beta version of NASA's CARES/Life code, and an example demonstrating its viability was presented.
    Keywords: Aircraft Propulsion and Power
    Type: Fifth Annual Workshop on the Application of Probabilistic Methods for Gas Turbine Engines; 555-586; NASA/CP-2002-211682
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  • 3
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    Measurement Of Trailing Edge Noise using Directional Array and Coherent Output Power Methods (2002)
    In:  CASI
    Details
    Publication Date: 2005-11-10
    Description: The use of a directional array of microphones for the measurement of trailing edge (TE) noise is described. The capabilities of this method are evaluated via measurements of TE noise from a NACA 63-215 airfoil model and from a cylindrical rod. This TE noise measurement approach is compared to one that is based on the cross spectral analysis of output signals from a pair of microphones (COP method). Advantages and limitations of both methods are examined. It is shown that the microphone array can accurately measures TE noise and captures its two-dimensional characteristic over a large frequency range for any TE configuration as long as noise contamination from extraneous sources is within bounds. The COP method is shown to also accurately measure TE noise but over a more limited frequency range that narrows for increased TE thickness. Finally, the applicability and generality of an airfoil self-noise prediction method was evaluated via comparison to the experimental data obtained using the COP and array measurement methods. The predicted and experimental results are shown to agree over large frequency ranges.
    Keywords: Acoustics
    Type: Aeroacoustics; Volume 1; No. 4; 329-353
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  • 4
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    Airbreathing Pulse Detonation Engine Performance (2002)
    In:  Other Sources
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    Publication Date: 2011-08-23
    Description: This paper presents performance results for pulse detonation engines taking into account the effects of dissociation and recombination. The amount of sensible heat recovered through recombination in the PDE chamber and exhaust process was found to be significant. These results have an impact on the specific thrust, impulse and fuel consumption of the PDE.
    Keywords: Aircraft Propulsion and Power
    Type: 26th JANNAF Airbreathing Propulsion Subcommittee Meeting; Volume 1; 337-349; CPIA-Publ-713-Vol-1
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  • 5
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    Probabilistic Life and Reliability Analysis of Model Gas Turbine Disk (2002)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: In 1939, W. Weibull developed what is now commonly known as the "Weibull Distribution Function" primarily to determine the cumulative strength distribution of small sample sizes of elemental fracture specimens. In 1947, G. Lundberg and A. Palmgren, using the Weibull Distribution Function developed a probabilistic lifing protocol for ball and roller bearings. In 1987, E. V. Zaretsky using the Weibull Distribution Function modified the Lundberg and Palmgren approach to life prediction. His method incorporates the results of coupon fatigue testing to compute the life of elemental stress volumes of a complex machine element to predict system life and reliability. This paper examines the Zaretsky method to determine the probabilistic life and reliability of a model gas turbine disk using experimental data from coupon specimens. The predicted results are compared to experimental disk endurance data.
    Keywords: Aircraft Propulsion and Power
    Type: Fifth Annual Workshop on the Application of Probabilistic Methods for Gas Turbine Engines; 603-625; NASA/CP-2002-211682
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  • 6
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    Acoustic Experiment to Measure the Bulk Viscosity of Near-Critical Xenon in Microgravity (2002)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: We plan a rigorous test of the theory of dynamic scaling by accurately measuring the bulk viscosity of xenon in microgravity 50 times closer to the critical temperature T(sub c) than previous experiments. The bulk viscosity zeta (or "second viscosity" or "dilational viscosity") will be determined by measuring the attenuation length of sound alpha lambda and also measuring the frequency-dependence of the speed of sound. For these measurements, we developed a unique Helmholtz resonator and specialized electro-acoustic transducers. We describe the resonator, the transducers, their performance on Earth, and their expected performance in microgravity.
    Keywords: Acoustics
    Type: Sixth Microgravity Fluid Physics and Transport Phenomena Conference: Exposition Topical Areas 1-6; Volume 2; 556-570; NASA/CP-2002-211212/VOL2
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  • 7
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    A New Time Domain Formulation for Broadband Noise Predictions (2002)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: A new analytic result in acoustics called "Formulation 1B," proposed by Farassat, is used to compute the loading noise from an unsteady surface pressure distribution on a thin airfoil in the time domain. This formulation is a new solution of the Ffowcs Williams-Hawkings equation with the loading source term. The formulation contains a far field surface integral that depends on the time derivative and the surface gradient of the pressure on the airfoil, as well as a contour integral on the boundary of the airfoil surface. As a first test case, the new formulation is used to compute the noise radiated from a flat plate, moving through a sinusoidal gust of constant frequency. The unsteady surface pressure for this test case is analytically specified from a result based on linear airfoil theory. This test case is used to examine the velocity scaling properties of Formulation 1B and to demonstrate its equivalence to Formulation 1A of Farassat. The new acoustic formulation, again with an analytic surface pressure, is then used to predict broadband noise radiated from an airfoil immersed in homogeneous, isotropic turbulence. The results are compared with experimental data previously reported by Paterson and Amiet. Good agreement between predictions and measurements is obtained. Finally, an alternative form of Formulation 1B is described for statistical analysis of broadband noise.
    Keywords: Acoustics
    Type: International Journal of Aeroacoustics; Volume 1; No. 3; 207-240
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  • 8
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    The Acoustic Analogy and Alternative Theories for Jet Noise Prediction (2002)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: This paper describes several methods for the prediction of jet noise. All but one of the noise prediction schemes are based on Lighthill's or Lilley's acoustic analogy while the other is the jet noise generation model recently proposed by Tam and Auriault. In all the approaches some assumptions must be made concerning the statistical properties of the turbulent sources. In each case the characteristic scales of the turbulence are obtained from a solution of the Reynolds-averaged Navier Stokes equation using a k - epsilon turbulence model. It is shown that, for the same level of empiricism, Tam and Auriault's model yields better agreement with experimental noise measurements than the acoustic analogy. It is then shown that this result is not because of some fundamental flaw in the acoustic analogy approach: but, is associated with the assumptions made in the approximation of the turbulent source statistics. If consistent assumptions are made, both the acoustic analogy and Tam and Auriault's model yield identical noise predictions. The paper concludes with a proposal for an acoustic analogy that provides a clearer identification of the equivalent source mechanisms and a discussion of noise prediction issues that remain to be resolved.
    Keywords: Acoustics
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  • 9
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    Risk-Based Probabilistic Approach to Aeropropulsion System Assessment (2002)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: In an era of shrinking development budgets and resources, where there is also an emphasis on reducing the product development cycle, the role of system assessment, performed in the early stages of an engine development program, becomes very critical to the successful development of new aeropropulsion systems. A reliable system assessment not only helps to identify the best propulsion system concept among several candidates, it can also identify which technologies are worth pursuing. This is particularly important for advanced aeropropulsion technology development programs, which require an enormous amount of resources. In the current practice of deterministic, or point-design, approaches, the uncertainties of design variables are either unaccounted for or accounted for by safety factors. This could often result in an assessment with unknown and unquantifiable reliability. Consequently, it would fail to provide additional insight into the risks associated with the new technologies, which are often needed by decision makers to determine the feasibility and return-on-investment of a new aircraft engine. In this work, an alternative approach based on the probabilistic method was described for a comprehensive assessment of an aeropropulsion system. The statistical approach quantifies the design uncertainties inherent in a new aeropropulsion system and their influences on engine performance. Because of this, it enhances the reliability of a system assessment. A technical assessment of a wave-rotor-enhanced gas turbine engine was performed to demonstrate the methodology. The assessment used probability distributions to account for the uncertainties that occur in component efficiencies and flows and in mechanical design variables. The approach taken in this effort was to integrate the thermodynamic cycle analysis embedded in the computer code NEPP (NASA Engine Performance Program) and the engine weight analysis embedded in the computer code WATE (Weight Analysis of Turbine Engines) with the fast probability integration technique (FPI). FPI was developed by Southwest Research Institute under contract with the NASA Glenn Research Center. The results were plotted in the form of cumulative distribution functions and sensitivity analyses and were compared with results from the traditional deterministic approach. The comparison showed that the probabilistic approach provides a more realistic and systematic way to assess an aeropropulsion system. The current work addressed the application of the probabilistic approach to assess specific fuel consumption, engine thrust, and weight. Similarly, the approach can be used to assess other aspects of aeropropulsion system performance, such as cost, acoustic noise, and emissions. Additional information is included in the original extended abstract.
    Keywords: Aircraft Propulsion and Power
    Type: Fifth Annual Workshop on the Application of Probabilistic Methods for Gas Turbine Engines; 139-164; NASA/CP-2002-211682
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  • 10
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    The Effect of Variable Chord Length on Transonic Axial Rotor Performance (2002)
    In:  Other Sources
    Details
    Publication Date: 2011-08-23
    Description: Aircraft fan and compressor blade leading edges suffer from atmospheric particulate erosion that reduces aerodynamic performance. Recontouring the blade leading edge region can restore blade performance. This process typically results in blades of varying chord length. The question therefore arises as to whether performance of refurbished fans and compressors could be further improved if blades of varying chord length are installed into the disk in a certain order. To investigate this issue the aerodynamic performance of a transonic compressor rotor operating with blades of varying chord length was measured in back-to-back compressor test rig entries. One half of the rotor blades were the full nominal chord length while the remaining half of the blades were cut back at the leading edge to 95% of chord length and recontoured. The rotor aerodynamic performance was measured at 100, 80, and 60% of design speed for three blade installation configurations: nominal-chord blades in half of the disk and short-chord blades in half of the disk; four alternating quadrants of nominal-chord and short-chord blades; nominal-chord and short-chord blades alternating around the disk. No significant difference in performance was found between configurations, indicating that blade chord variation is not important to aerodynamic performance above the stall chord limit if leading edges have the same shape. The stall chord limit for most civil aviation turbofan engines is between 94-96% of nominal (new) blade chord.
    Keywords: Aircraft Propulsion and Power
    Type: Journal of Turbomachinery; Volume 24; 351-357
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  • 11
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    Acoustic Analogy and Alternative Theories for Jet Noise Prediction (2002)
    In:  Other Sources
    Details
    Publication Date: 2011-08-23
    Description: Several methods for the prediction of jet noise are described. All but one of the noise prediction schemes are based on Lighthill's or Lilley's acoustic analogy, whereas the other is the jet noise generation model recently proposed by Tam and Auriault. In all of the approaches, some assumptions must be made concerning the statistical properties of the turbulent sources. In each case the characteristic scales of the turbulence are obtained from a solution of the Reynolds-averaged Navier-Stokes equation using a kappa-sigma turbulence model. It is shown that, for the same level of empiricism, Tam and Auriault's model yields better agreement with experimental noise measurements than the acoustic analogy. It is then shown that this result is not because of some fundamental flaw in the acoustic analogy approach, but instead is associated with the assumptions made in the approximation of the turbulent source statistics. If consistent assumptions are made, both the acoustic analogy and Tam and Auriault's model yield identical noise predictions. In conclusion, a proposal is presented for an acoustic analogy that provides a clearer identification of the equivalent source mechanisms, as is a discussion of noise prediction issues that remain to be resolved.
    Keywords: Acoustics
    Type: AIAA Journal; Volume 40; No. 4; 671- 680
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  • 12
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    Development of a Turbofan Engine Simulation in a Graphical Simulation Environment (2002)
    In:  Other Sources
    Details
    Publication Date: 2011-08-23
    Description: This paper presents progress on the development of a generic component level model of a turbofan engine simulation, with a digital controller, in an advanced graphical simulation environment. The goal of this effort is to develop and demonstrate a flexible simulation platform for future research in propulsion system control and diagnostic technology. A FORTRAN-based model of a modem, high performance, military-type turbofan engine is being used to validate the platform development. The implementation process required the development of various innovative procedures, which are discussed in the paper. Open-loop and closed-loop comparisons are made between the two simulations. Future enhancements that are to be made to the modular engine simulation are summarized.
    Keywords: Aircraft Propulsion and Power
    Type: 26th JANNAF Airbreathing Propulsion Subcommittee Meeting; Volume 1; 249-257; CPIA-Publ-713-Vol-1
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  • 13
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    Effects of Endwall Geometry and Stacking on Two-Stage Supersonic Turbine Performance (2002)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: Two methods are commonly used to control the secondary/separated flows (and associated losses) in supersonic turbines: endwall contouring and airfoil stacking. In the current investigation the flow path between the first-stage vanes and rotors, and the stacking of the first-stage vanes were varied in an effort to improve turbine performance. The geometric variations have been studied by performing a series of unsteady three-dimensional numerical simulations for the two-stage turbine.
    Keywords: Aircraft Propulsion and Power
    Type: 2002 AIAA Aerospace Sciences Meeting; Unknown
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  • 14
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    An Aeroacoustic Study of a Leading Edge Slat Configuration (2002)
    In:  CASI
    Details
    Publication Date: 2018-06-11
    Description: Aeroacoustic evaluations of high-lift devices have been carried out in the Quiet Flow Facility of the NASA Langley Research Center. The present paper describes detailed flow and acoustic measurements that have been made in order to better understand the noise generated from airflow over a wing leading edge slat configuration, and to possibly predict and reduce this noise source. The acoustic database is obtained by a moveable Small Aperture Directional Array of microphones designed to electronically steer to different portions of models under study. The slat is shown to be a uniform distributed noise source. The data was processed such that spectra and directivity were determined with respect to a one-foot span of slat. The spectra are normalized in various fashions to demonstrate slat noise character. In order to equate portions of the spectra to different slat noise components, trailing edge noise predictions using measured slat boundary layer parameters as inputs are compared to the measured slat noise spectra.
    Keywords: Acoustics
    Type: Aeroacoustics; Volume 1; No. 3; 241-274
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  • 15
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    One-Dimensional Spontaneous Raman Measurements of Temperature Made in a Gas Turbine Combustor (2002)
    In:  CASI
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    Publication Date: 2018-06-05
    Description: The NASA Glenn Research Center is working with the aeronautics industry to develop highly fuel-efficient and environmentally friendly gas turbine combustor technology. This effort includes testing new hardware designs at conditions that simulate the high-temperature, high-pressure environment expected in the next-generation of high-performance engines. Glenn has the only facilities in which such tests can be performed. One aspect of these tests is the use of nonintrusive optical and laser diagnostics to measure combustion species concentration, fuel/air ratio, fuel drop size, and velocity, and to visualize the fuel injector spray pattern and some combustion species distributions. These data not only help designers to determine the efficacy of specific designs, but provide a database for computer modelers and enhance our understanding of the many processes that take place within a combustor. Until recently, we lacked one critical capability, the ability to measure temperature. This article summarizes our latest developments in that area. Recently, we demonstrated the first-ever use of spontaneous Raman scattering to measure combustion temperatures within the Advanced Subsonics Combustion Rig (ASCR) sector rig. We also established the highest rig pressure ever achieved for a continuous-flow combustor facility, 54.4 bar. The ASCR facility can provide operating pressures from 1 to 60 bar (60 atm). This photograph shows the Raman system setup next to the ASCR rig. The test was performed using a NASA-concept fuel injector and Jet-A fuel over a range of air inlet temperatures, pressures, and fuel/air ratios.
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 2001; NASA/TM-2002-211333
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  • 16
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    Reply by the Authors to C. K. W. Tam (2002)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: The prediction of noise generation and radiation by turbulence has been the subject of continuous research for over fifty years. The essential problem is how to model the noise sources when one s knowledge of the detailed space-time properties of the turbulence is limited. We attempted to provide a comparison of models based on acoustic analogies and recent alternative models. Our goal was to demonstrate that the predictive capabilities of any model are based on the choice of the turbulence property that is modeled as a source of noise. Our general definition of an acoustic analogy is a rearrangement of the equations of motion into the form L(u) = Q, where L is a linear operator that reduces to an acoustic propagation operator outside a region upsilon; u is a variable that reduces to acoustic pressure (or a related linear acoustic variable) outside upsilon; and Q is a source term that can be meaningfully estimated without knowing u and tends to zero outside upsilon.
    Keywords: Acoustics
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  • 17
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    Modeling Aerodynamically Generated Sound of Helicopter Rotors (2002)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: A great deal of progress has been made in the modeling of aerodynamically generated sound of rotors over the past decade. Although the modeling effort has focused on helicopter main rotors, the theory is generally valid for a wide range of rotor configurations. The Ffowcs Williams Hawkings (FW-H) equation has been the foundation for much of the development. The monopole and dipole source terms of the FW-H equation account for the thickness and loading noise, respectively. Bladevortex-interaction noise and broadband noise are important types of loading noise, hence much research has been directed toward the accurate modeling of these noise mechanisms. Both subsonic and supersonic quadrupole noise formulations have been developed for the prediction of high-speed impulsive noise. In an effort to eliminate the need to compute the quadrupole contribution, the FW-H equation has also been utilized on permeable surfaces surrounding all physical noise sources. Comparisons of the Kirchhoff formulation for moving surfaces with the FW-H equation have shown that the Kirchhoff formulation for moving surfaces can give erroneous results for aeroacoustic problems. Finally, significant progress has been made incorporating the rotor noise models into full vehicle noise prediction tools.
    Keywords: Acoustics
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  • 18
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    Transonic Resonance Demonstrated To Be a Source of Internal Noise From Mixer-Ejector Nozzles (2002)
    In:  CASI
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    Publication Date: 2018-06-05
    Description: During noise field studies with mixer-ejector nozzles in NASA's High-Speed Research program, tones were often encountered. The tones would persist in the simulated "cutback" condition (shortly after takeoff). Unfortunately, we did not understand their origin and, thus, could not develop a logical approach for suppressing them. We naturally questioned whether or not some of those tones were due to the transonic resonance. This was studied with a 1/13th scale model of the High-Speed Civil Transport nozzle. The first objective was to determine if indeed tones could be detected in the radiated noise. The next objective was to diagnose if those tones were due to the transonic resonance. Agreement of the frequencies with the correlation equation and the effect of boundary layer tripping were to be used in the diagnosis.
    Keywords: Acoustics
    Type: Research and Technology 2001; NASA/TM-2002-211333
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  • 19
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    A Two-Dimensional Linear Bicharacteristic FDTD Method (2002)
    In:  CASI
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    Publication Date: 2018-06-05
    Description: The linear bicharacteristic scheme (LBS) was originally developed to improve unsteady solutions in computational acoustics and aeroacoustics. The LBS has previously been extended to treat lossy materials for one-dimensional problems. It is a classical leapfrog algorithm, but is combined with upwind bias in the spatial derivatives. This approach preserves the time-reversibility of the leapfrog algorithm, which results in no dissipation, and it permits more flexibility by the ability to adopt a characteristic based method. The use of characteristic variables allows the LBS to include the Perfectly Matched Layer boundary condition with no added storage or complexity. The LBS offers a central storage approach with lower dispersion than the Yee algorithm, plus it generalizes much easier to nonuniform grids. It has previously been applied to two and three-dimensional free-space electromagnetic propagation and scattering problems. This paper extends the LBS to the two-dimensional case. Results are presented for point source radiation problems, and the FDTD algorithm is chosen as a convenient reference for comparison.
    Keywords: Acoustics
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    Sonic Boom Testing Performed in NASA Glenn Research Center's 10- by 10-Foot Supersonic Wind Tunnel (2002)
    In:  CASI
    Details
    Publication Date: 2018-06-02
    Description: One of the current impediments to the establishment of supersonic transports as a viable part of the commercial aviation fleet is the sonic boom effect. This effect is created when a vehicle achieves supersonic speeds and creates a shock wave (an immediate pressure change) that impinges on the ground. The resulting sonic boom can be both heard and felt on the ground, and it traverses the ground along the flight path of the vehicle. The environmental impact of this sonic boom effect is currently regulated by only allowing supersonic flight on over-water flight paths. The ability to measure the pressure signature of an aircraft configuration would allow researchers to identify the sources and the relative magnitude of that source on the aircraft pressure signature. It would also allow for the development and validation of computer codes to predict the sonic boom effects of an aircraft configuration.
    Keywords: Acoustics
    Type: Research and Technology 2001; NASA/TM-2002-211333
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  • 21
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    International Space Station Power System Model Validated (2002)
    In:  CASI
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    Publication Date: 2018-06-02
    Description: System Power Analysis for Capability Evaluation (SPACE) is a computer model of the International Space Station's (ISS) Electric Power System (EPS) developed at the NASA Glenn Research Center. This uniquely integrated, detailed model can predict EPS capability, assess EPS performance during a given mission with a specified load demand, conduct what-if studies, and support on-orbit anomaly resolution.
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 2001; NASA/TM-2002-211333
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    Hybrid Neural-Network: Genetic Algorithm Technique for Aircraft Engine Performance Diagnostics Developed and Demonstrated (2002)
    In:  CASI
    Details
    Publication Date: 2018-06-02
    Description: As part of the NASA Aviation Safety Program, a unique model-based diagnostics method that employs neural networks and genetic algorithms for aircraft engine performance diagnostics has been developed and demonstrated at the NASA Glenn Research Center against a nonlinear gas turbine engine model. Neural networks are applied to estimate the internal health condition of the engine, and genetic algorithms are used for sensor fault detection, isolation, and quantification. This hybrid architecture combines the excellent nonlinear estimation capabilities of neural networks with the capability to rank the likelihood of various faults given a specific sensor suite signature. The method requires a significantly smaller data training set than a neural network approach alone does, and it performs the combined engine health monitoring objectives of performance diagnostics and sensor fault detection and isolation in the presence of nominal and degraded engine health conditions.
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 2001; NASA/TM-2002-211333
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  • 23
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    New Fan Engine Noise-Reduction Concept Using Trailing Edge Blowing of Fan Blades Demonstrated (2002)
    In:  CASI
    Details
    Publication Date: 2018-06-02
    Description: A major source of noise in commercial turbofan engines is the interaction of the fan blade wakes with the fan exit vanes (stators). These wakes can be greatly reduced by filling them with air blown out of the blade trailing edge. Extensive testing of this concept has demonstrated significant noise reductions. These tests were conducted on a low-speed, 4- ft-diameter fan using hollow blades at NASA Glenn Research Center's Aeroacoustic Propulsion Laboratory (AAPL).
    Keywords: Acoustics
    Type: Research and Technology 2001; NASA/TM-2002-211333
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  • 24
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    Numerical Propulsion System Simulation (NPSS): An Award Winning Propulsion System Simulation Tool (2002)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: The Numerical Propulsion System Simulation (NPSS) is a full propulsion system simulation tool used by aerospace engineers to predict and analyze the aerothermodynamic behavior of commercial jet aircraft, military applications, and space transportation. The NPSS framework was developed to support aerospace, but other applications are already leveraging the initial capabilities, such as aviation safety, ground-based power, and alternative energy conversion devices such as fuel cells. By using the framework and developing the necessary components, future applications that NPSS could support include nuclear power, water treatment, biomedicine, chemical processing, and marine propulsion. NPSS will dramatically reduce the time, effort, and expense necessary to design and test jet engines. It accomplishes that by generating sophisticated computer simulations of an aerospace object or system, thus enabling engineers to "test" various design options without having to conduct costly, time-consuming real-life tests. The ultimate goal of NPSS is to create a numerical "test cell" that enables engineers to create complete engine simulations overnight on cost-effective computing platforms. Using NPSS, engine designers will be able to analyze different parts of the engine simultaneously, perform different types of analysis simultaneously (e.g., aerodynamic and structural), and perform analysis in a more efficient and less costly manner. NPSS will cut the development time of a new engine in half, from 10 years to 5 years. And NPSS will have a similar effect on the cost of development: new jet engines will cost about a billion dollars to develop rather than two billion. NPSS is also being applied to the development of space transportation technologies, and it is expected that similar efficiencies and cost savings will result. Advancements of NPSS in fiscal year 2001 included enhancing the NPSS Developer's Kit to easily integrate external components of varying fidelities, providing the initial Visual-Based Syntax (VBS) capability, and developing additional capabilities to support space transportation. NPSS was supported under NASA's High Performance Computing and Communications Program. Through the NASA/Industry Cooperative Effort agreement, NASA Glenn and its industry and Government partners are developing NPSS. The NPSS team consists of propulsion experts and software engineers from GE Aircraft Engines, Pratt & Whitney, The Boeing Company, Honeywell, Rolls-Royce Corporation, Williams International, Teledyne Continental Motors, Arnold Engineering Development Center, Wright Patterson Air Force Base, and the NASA Glenn Research Center. Glenn is leading the way in developing NPSS--a method for solving complex design problems that's faster, better, and cheaper.
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 2001; NASA/TM-2002-211333
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    Mystery of Foil Air Bearings for Oil-free Turbomachinery Unlocked: Load Capacity Rule-of-thumb Allows Simple Estimation of Performance (2002)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: The Oil-Free Turbomachinery team at the NASA Glenn Research Center has unlocked one of the mysteries surrounding foil air bearing performance. Foil air bearings are self-acting hydrodynamic bearings that use ambient air, or any fluid, as their lubricant. In operation, the motion of the shaft's surface drags fluid into the bearing by viscous action, creating a pressurized lubricant film. This lubricating film separates the stationary foil bearing surface from the moving shaft and supports load. Foil bearings have been around for decades and are widely employed in the air cycle machines used for cabin pressurization and cooling aboard commercial jetliners. The Oil-Free Turbomachinery team is fostering the maturation of this technology for integration into advanced Oil-Free aircraft engines. Elimination of the engine oil system can significantly reduce weight and cost and could enable revolutionary new engine designs. Foil bearings, however, have complex elastic support structures (spring packs) that make the prediction of bearing performance, such as load capacity, difficult if not impossible. Researchers at Glenn recently found a link between foil bearing design and load capacity performance. The results have led to a simple rule-of-thumb that relates a bearing's size, speed, and design to its load capacity. Early simple designs (Generation I) had simple elastic (spring) support elements, and performance was limited. More advanced bearings (Generation III) with elastic supports, in which the stiffness is varied locally to optimize gas film pressures, exhibit load capacities that are more than double those of the best previous designs. This is shown graphically in the figure. These more advanced bearings have enabled industry to introduce commercial Oil-Free gas-turbine-based electrical generators and are allowing the aeropropulsion industry to incorporate the technology into aircraft engines. The rule-of-thumb enables engine and bearing designers to easily size and select bearing technology for a new application and determine the level of complexity required in the bearings. This new understanding enables industry to assess the feasibility of new engine designs and provides critical guidance toward the future development of Oil-Free turbomachinery propulsion systems.
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 2001; NASA/TM-2002-211333
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    Aeroacoustic Flow Phenomena Accurately Captured by New Computational Fluid Dynamics Method (2002)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: One of the challenges in the computational fluid dynamics area is the accurate calculation of aeroacoustic phenomena, especially in the presence of shock waves. One such phenomenon is "transonic resonance," where an unsteady shock wave at the throat of a convergent-divergent nozzle results in the emission of acoustic tones. The space-time Conservation-Element and Solution-Element (CE/SE) method developed at the NASA Glenn Research Center can faithfully capture the shock waves, their unsteady motion, and the generated acoustic tones. The CE/SE method is a revolutionary new approach to the numerical modeling of physical phenomena where features with steep gradients (e.g., shock waves, phase transition, etc.) must coexist with those having weaker variations. The CE/SE method does not require the complex interpolation procedures (that allow for the possibility of a shock between grid cells) used by many other methods to transfer information between grid cells. These interpolation procedures can add too much numerical dissipation to the solution process. Thus, while shocks are resolved, weaker waves, such as acoustic waves, are washed out.
    Keywords: Acoustics
    Type: Research and Technology 2001; NASA/TM-2002-211333
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    Turbopump Performance Improved by Evolutionary Algorithms (2002)
    In:  CASI
    Details
    Publication Date: 2018-06-05
    Description: The development of design optimization technology for turbomachinery has been initiated using the multiobjective evolutionary algorithm under NASA's Intelligent Synthesis Environment and Revolutionary Aeropropulsion Concepts programs. As an alternative to the traditional gradient-based methods, evolutionary algorithms (EA's) are emergent design-optimization algorithms modeled after the mechanisms found in natural evolution. EA's search from multiple points, instead of moving from a single point. In addition, they require no derivatives or gradients of the objective function, leading to robustness and simplicity in coupling any evaluation codes. Parallel efficiency also becomes very high by using a simple master-slave concept for function evaluations, since such evaluations often consume the most CPU time, such as computational fluid dynamics. Application of EA's to multiobjective design problems is also straightforward because EA's maintain a population of design candidates in parallel. Because of these advantages, EA's are a unique and attractive approach to real-world design optimization problems.
    Keywords: Aircraft Propulsion and Power
    Type: Research and Technology 2001; NASA/TM-2002-211333
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    Overview of NASA Glenn Research Center Programs in Aero-Heat Transfer and Future Needs (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This presentation concentrates on an overview of the NASA Glenn Research Center and the projects that are supporting Turbine Aero-Heat Transfer Research. The principal areas include the Ultra Efficient Engine Technology (UEET) Project, the Advanced Space Transportation Program (ASTP) Revolutionary Turbine Accelerator (RTA) Turbine Based Combined Cycle (TBCC) project, and the Propulsion & Power Base R&T - Smart Efficient Components (SEC), and Revolutionary Aeropropulsion Concepts (RAC) Projects. In addition, highlights are presented of the turbine aero-heat transfer work currently underway at NASA Glenn, focusing on the use of the Glenn-HT Navier- Stokes code as the vehicle for research in turbulence & transition modeling, grid topology generation, unsteady effects, and conjugate heat transfer.
    Keywords: Aircraft Propulsion and Power
    Type: Department of Energy, National Technology Lab. High Efficiency Engines and Turbines-University Turbine Systems Research (HEET-UTSR) Program: Aero-Heat Transfer workshop-V Program Review; Nov 11, 2002 - Nov 13, 2002; Baton Rouge, LA; United States
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    Compatibility Studies of Hydrogen Peroxide and a New Hypergolic Fuel Blend (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Several preliminary materials compatibility studies have been conducted to determine the practicality of a new hypergolic fuel system. Hypergolic fuel ignites spontaneously as the oxidizer decomposes and releases energy in the presence of the fuel. The bipropellant system tested consists of high-test hydrogen peroxide (HTP) and a liquid fuel blend consisting of a hydrocarbon fuel, an ignition enhancer and a transition metal catalyst. In order for further testing of the new fuel blend to take place, some basic materials compatibility and HTP decomposition studies must be accomplished. The thermal decomposition rate of HTP was tested using gas evolution and isothermal microcalorimetry (IMC). Materials were analyzed for compatibility with hydrogen peroxide including a study of the affect welding has on stainless steel elemental composition and its relation to HTP decomposition. Compatibility studies of valve materials in the fuel blend were performed to determine the corrosion resistance of the materials.
    Keywords: Aircraft Propulsion and Power
    Type: NASA-MSFC 2002 Undergraduate Student Research Program Technical Report Collection; Nov 01, 2002; Huntsville, AL; United States
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    A Comparison of Ffowcs Williams-Hawkings Solvers for Airframe Noise Applications (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper presents a comparison between two implementations of the Ffowcs Williams and Hawkings equation for airframe noise applications. Airframe systems are generally moving at constant speed and not rotating, so these conditions are used in the current investigation. Efficient and easily implemented forms of the equations applicable to subsonic, rectilinear motion of all acoustic sources are used. The assumptions allow the derivation of a simple form of the equations in the frequency-domain, and the time-domain method uses the restrictions on the motion to reduce the work required to find the emission time. The comparison between the frequency domain method and the retarded time formulation reveals some of the advantages of the different approaches. Both methods are still capable of predicting the far-field noise from nonlinear near-field flow quantities. Because of the large input data sets and potentially large numbers of observer positions of interest in three-dimensional problems, both codes utilize the message passing interface to divide the problem among different processors. Example problems are used to demonstrate the usefulness and efficiency of the two schemes.
    Keywords: Acoustics
    Type: AIAA Paper 2002-2580 , AIAA/CEAS Aeroacoustics Conference; Jun 17, 2002 - Jun 19, 2002; Breckenridge, CO; United States
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    WIND Validation Cases: Computational Study of Thermally-perfect Gases (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The ability of the WIND Navier-Stokes code to predict the physics of multi-species gases is investigated in support of future high-speed, high-temperature propulsion applications relevant to NASA's Space Transportation efforts. Three benchmark cases are investigated to evaluate the capability of the WIND chemistry model to accurately predict the aerodynamics of multi-species chemically non-reacting (frozen) gases. Case 1 represents turbulent mixing of sonic hydrogen and supersonic vitiated air. Case 2 consists of heated and unheated round supersonic jet exiting to ambient. Case 3 represents 2-D flow through a converging-diverging Mach 2 nozzle. For Case 1, the WIND results agree fairly well with experimental results and that significant mixing occurs downstream of the hydrogen injection point. For Case 2, the results show that the Wilke and Sutherland viscosity laws gave similar results, and the available SST turbulence model does not predict round supersonic nozzle flows accurately. For Case 3, results show that experimental, frozen, and 1-D gas results agree fairly well, and that frozen, homogeneous, multi-species gas calculations can be approximated by running in perfect gas mode while specifying the mixture gas constant and Ratio of Specific Heats.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2002-212015 , NAS 1.26:212015 , E-13704 , ICOMP-2002-07 , AIAA Paper 2003-0546 , 41st Aerospace Sciences Meeting and Exhibit; Jan 06, 2003 - Jan 09, 2003; Reno, NV; United States
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    Effects of Endwall Geometry and Stacking on Two-Stage Supersonic Turbine Performance (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The drive towards high-work turbines has led to designs which can be compact, transonic, supersonic, counter rotating, or use a dense drive gas. These aggressive designs can lead to strong secondary flows and airfoil flow separation. In many cases the secondary and separated flows can be minimized by contouring the hub/shroud endwalls and/or modifying the airfoil stacking. In this study, three-dimensional unsteady Navier-Stokes simulations were performed to study three different endwall shapes between the first-stage vanes and rotors, as well as two different stackings for the first-stage vanes. The predicted results indicate that changing the stacking of the first-stage vanes can significantly impact endwall separation (and turbine performance) in regions where the endwall profile changes.
    Keywords: Aircraft Propulsion and Power
    Type: AIAA Paper 2002-0078 , 40th AIAA Aerospace Sciences Meeting and Exhibit; Jan 14, 2002 - Jan 17, 2002; Reno, NV; United States
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    A Tool for Low Noise Procedures Design and Community Noise Impact Assessment: The Rotorcraft Noise Model (RNM) (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: To improve aircraft noise impact modeling capabilities and to provide a tool to aid in the development of low noise terminal area operations for rotorcraft and tiltrotors, the Rotorcraft Noise Model (RNM) was developed by the NASA Langley Research Center and Wyle Laboratories. RNM is a simulation program that predicts how sound will propagate through the atmosphere and accumulate at receiver locations located on flat ground or varying terrain, for single and multiple vehicle flight operations. At the core of RNM are the vehicle noise sources, input as sound hemispheres. As the vehicle "flies" along its prescribed flight trajectory, the source sound propagation is simulated and accumulated at the receiver locations (single points of interest or multiple grid points) in a systematic time-based manner. These sound signals at the receiver locations may then be analyzed to obtain single event footprints, integrated noise contours, time histories, or numerous other features. RNM may also be used to generate spectral time history data over a ground mesh for the creation of single event sound animation videos. Acoustic properties of the noise source(s) are defined in terms of sound hemispheres that may be obtained from theoretical predictions, wind tunnel experimental results, flight test measurements, or a combination of the three. The sound hemispheres may contain broadband data (source levels as a function of one-third octave band) and pure-tone data (in the form of specific frequency sound pressure levels and phase). A PC executable version of RNM is publicly available and has been adopted by a number of organizations for Environmental Impact Assessment studies of rotorcraft noise. This paper provides a review of the required input data, the theoretical framework of RNM's propagation model and the output results. Code validation results are provided from a NATO helicopter noise flight test as well as a tiltrotor flight test program that used the RNM as a tool to aid in the development of low noise approach profiles.
    Keywords: Acoustics
    Type: AHS International Technical Specialists'' Meeting on Advanced Rotorcraft Technology and Life Saving Activities; Nov 11, 2002 - Nov 13, 2002; Utsunomiya; Japan
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    Reduction of Wake-Stator Interaction Noise Using Passive Porosity (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The present study was conducted to assess the potential of Passive Porosity Technology as a mechanism to reduce interaction noise in turbomachinery by reducing the fluctuating forces acting on the vane surfaces. To do so, a typical fan stator airfoil was subjected to the effects of a transversely moving wake; time histories of the primitive aerodynamic variables, obtained from Computational Fluid Dynamics (CFD) solutions, were then input into an acoustic prediction code. This procedure was performed on the solid airfoil to obtain a baseline, and on a series of porous configurations in order to isolate those that yield maximum noise reductions without compromising the aerodynamic performance of the stator. It was found that communication between regions of high pressure differential - made possible by the use of passive porosity - is necessary to significantly alter the noise radiation pattern of the stator airfoil. In general, noise reductions were obtained for those configurations incorporating passive porosity in the region between x/c is approximately 0.15 on the suction side of the airfoil and x/c is approximately 0.20 on the pressure side. Reductions in overall radiated noise of approximately 1.0 dB were obtained. The noise benefit increased to about 2.5 dB when the effects of loading noise alone were considered.
    Keywords: Acoustics
    Type: AIAA Paper 2002-1036 , 40th AIAA Aerospace Sciences Meeting and Exhibit; Jan 14, 2002 - Jan 17, 2002; Reno, NV; United States
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    Acoustic Aspects of Active-Twist Rotor Control (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The use of an Active Twist Rotor system to provide both vibration reduction and performance enhancement has been explored in recent analytical and experimental studies. Effects of active-twist control on rotor noise, however, had not been determined. During a recent wind tunnel test of an active-twist rotor system, a set of acoustic measurements were obtained to assess the effects of active-twist control on noise produced by the rotor, especially blade-vortex interaction (BVI) noise. It was found that for rotor operating conditions where BVI noise is dominant, active-twist control provided a reduction in BVI noise level. This BVI noise reduction was almost, but not quite, as large as that obtained in a similar test using HHC. However, vibration levels were usually adversely affected at operating conditions favoring minimum BVI noise. Conversely, operating conditions favoring minimum vibration levels affected BVI noise levels, but not always adversely.
    Keywords: Acoustics
    Type: American Helicopter Society 58th Annual Forum; Jun 11, 2002 - Jun 13, 2002; Montreal; Canada
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    Low-Pressure Turbine Separation Control: Comparison With Experimental Data (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The present work details a computational study, using the Glenn HT code, that analyzes the use of vortex generator jets (VGJs) to control separation on a low-pressure turbine (LPT) blade at low Reynolds numbers. The computational results are also compared with the experimental data for steady VGJs. It is found that the code determines the proper location of the separation point on the suction surface of the baseline blade (without any VGJ) for Reynolds numbers of 50,000 or less. Also, the code finds that the separated region on the suction surface of the blade vanishes with the use of VGJs. However, the separated region and the wake characteristics are not well predicted. The wake width is generally over-predicted while the wake depth is under-predicted.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2002-211689 , NAS 1.26:211689 , E-13419 , GT-2002-30229 , Turbo Expo 2002; Jun 03, 2002 - Jun 06, 2002; Amsterdam; Netherlands
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    Heat Transfer in a Complex Trailing Edge Passage for a High Pressure Turbine Blade (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A combined experimental and numerical study to investigate the heat transfer distribution in a complex blade trailing edge passage was conducted. The geometry consists of a two pass serpentine passage with taper toward the trailing edge, as well as from hub to tip. The upflow channel has an average aspect ratio of roughly 14:1, while the exit passage aspect ratio is about 5:1. The upflow channel is split in an interrupted way and is smooth on the trailing edge side of the split and turbulated on the other side. A turning vane is placed near the tip of the upflow channel. Reynolds numbers in the range of 31,000 to 61,000, based on inlet conditions, were simulated numerically. The simulation was performed using the Glenn-HT code, a full three-dimensional Navier-Stokes solver using the Wilcox k-omega turbulence model. A structured multi-block grid is used with approximately 4.5 million cells and average y+ values on the order of unity. Pressure and heat transfer distributions are presented with comparison to the experimental data. While there are some regions with discrepancies, in general the agreement is very good for both pressure and heat transfer.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2002-211701 , NAS 1.26:211701 , ASME-2002-GT-30213 , E-13430 , Turbo Expo 2002; Jun 03, 2002 - Jun 06, 2002; Amsterdam; Netherlands
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    Initial Flight Tests of the NASA F-15B Propulsion Flight Test Fixture (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Flights of the F-15B/Propulsion Flight Test Fixture (PFTF) with a Cone Drag Experiment (CDE) attached have been accomplished at NASA Dryden Flight Research Center. Mounted underneath the fuselage of an F-15B airplane, the PFTF provides volume for experiment systems and attachment points for propulsion experiments. A unique feature of the PFTF is the incorporation of a six-degree-of-freedom force balance. The force balance mounts between the PFTF and experiment and measures three forces and moments. The CDE has been attached to the force balance for envelope expansion flights. This experiment spatially and inertially simulates a large propulsion test article. This report briefly describes the F-15B airplane, the PFTF, and the force balance. A detailed description of the CDE is provided. Force-balance ground testing and stiffness modifications are described. Flight profiles and selected flight data from the envelope expansion flights are provided and discussed, including force-balance data, the internal PFTF thermal and vibration environment, a handling qualities assessment, and performance capabilities of the F-15B airplane with the PFTF installed.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-210736 , NAS 1.15:210736 , H-2507 , 38th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit; Jul 07, 2002 - Jul 10, 2002; Indianapolis, IN; United States
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    Processing and Mechanical Properties of Various Zirconia/Alumina Composites for Fuel Cell Applications (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Various electrolyte materials for solid oxide fuel cells were fabricated by hot pressing 10 mol% yttria-stabilized zirconia (10-YSZ) reinforced with two different forms of alumina, particulates and platelets, each containing 0 to 30 mol% alumina. Flexure strength and fracture toughness of both particulate and platelet composites at ambient temperature increased with increasing alumina content, reaching a maximum at 30 mot% alumina. For a given alumina content, strength of particulate composites was greater than that of platelet composites, whereas, the difference in fracture toughness between the two composite systems was negligible. No virtual difference in elastic modulus and density was observed for a given alumina content between particulate and platelet composites. Thermal cycling up to 10 cycles between 200 to 1000 C did not show any effect on strength degradation of the 30 mol% platelet composites, indicative of negligible influence of CTE mismatches between YSZ matrix and alumina grains.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211580 , NAS 1.15:211580 , G-1:P03 , E-13365 , CIMTEC 2002, International Conferences on Modern Materials and Technologies; Jul 14, 2002 - Jul 19, 2002; Florence; Italy
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    Measurements of Turbulent Flow Field in Separate Flow Nozzles with Enhanced Mixing Devices - Test Report (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-12
    Description: As part of the Advanced Subsonic Technology Program, a series of experiments was conducted at NASA Glenn Research Center on the effect of mixing enhancement devices on the aeroacoustic performance of separate flow nozzles. Initial acoustic evaluations of the devices showed that they reduced jet noise significantly, while creating very little thrust loss. The explanation for the improvement required that turbulence measurements, namely single point mean and RMS statistics and two-point spatial correlations, be made to determine the change in the turbulence caused by the mixing enhancement devices that lead to the noise reduction. These measurements were made in the summer of 2000 in a test program called Separate Nozzle Flow Test 2000 (SFNT2K) supported by the Aeropropulsion Research Program at NASA Glenn Research Center. Given the hot high-speed flows representative of a contemporary bypass ratio 5 turbofan engine, unsteady flow field measurements required the use of an optical measurement method. To achieve the spatial correlations, the Particle Image Velocimetry technique was employed, acquiring high-density velocity maps of the flows from which the required statistics could be derived. This was the first successful use of this technique for such flows, and shows the utility of this technique for future experimental programs. The extensive statistics obtained were likewise unique and give great insight into the turbulence which produces noise and how the turbulence can be modified to reduce jet noise.
    Keywords: Acoustics
    Type: NASA/TM-2002-211366 , E-13188
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    High Temperature MEMS for Turbine Engine Applications (2002)
    In:  Other Sources
    Details
    Publication Date: 2019-07-18
    Description: The presentation will discuss Microelectromechanical Systems (MEMS) research and development activities and technologies being conducted at NASA Glenn Research Center to address the needs of harsh environment applications. The focus will be on silicon carbide based h4EMS for high temperature, high power and high radiation environment as well as high temperature sensor technologies which are made possible by MEMS processing techniques. These technologies can enable new measurements and capabilities for future turbine engines. All the presentation materials are publicly available and have been presented/published before.
    Keywords: Aircraft Propulsion and Power
    Type: Spring 2002 Meeting of RTO/AVT MEMS Task Group; Apr 22, 2002 - Apr 26, 2002; Paris; France
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    Aeoroacoustics Research Program in JIAFS (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: This document covers the following subjects related to an aeroacoustics research program: 1) Funding; 2) Personnel; 3) Theses and Dissertations; 4) Employment.
    Keywords: Acoustics
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    Performance of a Model Rich Burn-quick Mix-lean Burn Combustor at Elevated Temperature and Pressure (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: As interest in pollutant emission from stationary and aero-engine gas turbines increases, combustor engineers must consider various configurations. One configuration of increasing interest is the staged, rich burn - quick mix - lean burn (RQL) combustor. This report summarizes an investigation conducted in a recently developed high pressure gas turbine combustor facility. The model RQL combustor was plenum fed and modular in design. The fuel used for this study is Jet-A which was injected from a simplex atomizer. Emission (CO2, CO, O2, UHC, NOx) measurements were obtained using a stationary exit plane water-cooled probe and a traversing water-cooled probe which sampled from the rich zone exit and the lean zone entrance. The RQL combustor was operated at inlet temperatures ranging from 367 to 700 K, pressures ranging from 200 to 1000 kPa, and combustor reference velocities ranging from 10 to 20 m/s. Variations were also made in the rich zone and lean zone equivalence ratios. Several significant trends were observed. NOx production increased with reaction temperature, lean zone equivalence ratio and residence time and decreased with increased rich zone equivalence ratio. NOx production in the model RQL combustor increased to the 0.4 power with increased pressure. This correlation, compared to those obtained for non-staged combustors (0.5 to 0.7), suggests a reduced dependence on NOx on pressure for staged combustors. Emissions profiles suggest that rich zone mixing is not uniform and that the rich zone contributes on the order of 16 percent to the total NOx produced.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2002-211992 , NAS 1.26:211992 , E-13663
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    An Investigation of Surge in a High-Speed Centrifugal Compressor Using Digital PIV (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Compressor stall is a catastrophic breakdown of the flow in a compressor, which can lead to a loss of engine power, large pressure transients in the inlet/nacelle and engine flameout. The implementation of active or passive strategies for controlling rotating stall and surge can significantly extend the stable operating range of a compressor without substantially sacrificing performance. It is crucial to identify the dynamic changes occurring in the flow field prior to rotating stall and surge in order to successfully control these events. Generally, pressure transducer measurements are made to capture the transient response of a compressor prior to rotating stall. In this investigation, Digital Particle Imaging Velocimetry (DPIV) is used in conjunction with dynamic pressure transducers to simultaneously capture transient velocity and pressure measurements in the non-stationary flow field during compressor surge. DPIV is an instantaneous, planar measurement technique which is ideally suited for studying transient flow phenomena in high speed turbomachinery and has been used previously to successfully map the stable operating point flow field in the diffuser of a high speed centrifugal compressor. Through the acquisition of both DPIV images and transient pressure data, the time evolution of the unsteady flow during surge is revealed.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211832 , E-13281-1 , NAS 1.15:211832
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    Hydrogen Storage for Aircraft Applications Overview (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Advances in fuel cell technology have brought about their consideration as sources of power for aircraft. This power can be utilized to run aircraft systems or even provide propulsion power. One of the key obstacles to utilizing fuel cells on aircraft is the storage of hydrogen. An overview of the potential methods of hydrogen storage was compiled. This overview identifies various methods of hydrogen storage and points out their advantages and disadvantages relative to aircraft applications. Minimizing weight and volume are the key aspects to storing hydrogen within an aircraft. An analysis was performed to show how changes in certain parameters of a given storage system affect its mass and volume.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2002-211867 , E-13540 , NAS 1.26:211867
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    Foreign Object Damage Behavior of Two Gas-turbine Grade Silicon Nitrides by Steel Ball Projectiles at Ambient Temperature (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Foreign object damage (FOD) behavior of two commercial gas-turbine grade silicon nitrides, AS800 and SN282, was determined at ambient temperature through strength testing of flexure test specimens impacted by steel-ball projectiles with a diameter of 1.59 mm in a velocity range from 220 to 440 m/s. AS800 silicon nitride exhibited a greater FOD resistance than SN282, primarily due to its greater value of fracture toughness (K(sub IC)). Additionally, the FOD response of an equiaxed, fine-grained silicon nitride (NC132) was also investigated to provide further insight. The NC132 silicon nitride exhibited the lowest fracture toughness of the three materials tested, providing further evidence that K(sub IC) is a key material parameter affecting FOD resistance. The observed damage generated by projectile impact was typically in the forms of well- or ill-developed ring or cone cracks with little presence of radial cracks.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211821 , NAS 1.15:211821 , E-13513
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    APEX 3D Propeller Test Preliminary Design (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: A low Reynolds number, high subsonic mach number flight regime is fairly uncommon in aeronautics. Most flight vehicles do not fly under these aerodynamic conditions. However, recently there have been a number of proposed aircraft applications (such as high altitude observation platforms and Mars aircraft) that require flight within this regime. One of the main obstacles to flight under these conditions is the ability to reliably generate sufficient thrust for the aircraft. For a conventional propulsion system, the operation and design of the propeller is the key aspect to its operation. Due to the difficulty in experimentally modeling the flight conditions in ground-based facilities, it has been proposed to conduct propeller experiments from a high altitude gliding platform (APEX). A preliminary design of a propeller experiment under the low Reynolds number, high mach number flight conditions has been devised. The details of the design are described as well as the potential data that will be collected.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2002-211866 , NAS 1.26:211866 , E-13539
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    Effects of Fuel Distribution on Detonation Tube Performance (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: A pulse detonation engine (PDE) uses a series of high frequency intermittent detonation tubes to generate thrust. The process of filling the detonation tube with fuel and air for each cycle may yield non-uniform mixtures. Lack of mixture uniformity is commonly ignored when calculating detonation tube thrust performance. In this study, detonation cycles featuring idealized non-uniform H2/air mixtures were analyzed using the SPARK two-dimensional Navier-Stokes CFD code with 7-step H2/air reaction mechanism. Mixture non-uniformities examined included axial equivalence ratio gradients, transverse equivalence ratio gradients, and partially fueled tubes. Three different average test section equivalence ratios (phi), stoichiometric (phi = 1.00), fuel lean (phi = 0.90), and fuel rich (phi = 1.10), were studied. All mixtures were detonable throughout the detonation tube. It was found that various mixtures representing the same test section equivalence ratio had specific impulses within 1 percent of each other, indicating that good fuel/air mixing is not a prerequisite for optimal detonation tube performance.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211712 , E-13463 , NAS 1.15:211712
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    Characterization of the Temperature Capabilities of Advanced Disk Alloy ME3 (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The successful development of an advanced powder metallurgy disk alloy, ME3, was initiated in the NASA High Speed Research/Enabling Propulsion Materials (HSR/EPM) Compressor/Turbine Disk program in cooperation with General Electric Engine Company and Pratt & Whitney Aircraft Engines. This alloy was designed using statistical screening and optimization of composition and processing variables to have extended durability at 1200 F in large disks. Disks of this alloy were produced at the conclusion of the program using a realistic scaled-up disk shape and processing to enable demonstration of these properties. The objective of the Ultra-Efficient Engine Technologies disk program was to assess the mechanical properties of these ME3 disks as functions of temperature in order to estimate the maximum temperature capabilities of this advanced alloy. These disks were sectioned, machined into specimens, and extensively tested. Additional sub-scale disks and blanks were processed and selectively tested to explore the effects of several processing variations on mechanical properties. Results indicate the baseline ME3 alloy and process can produce 1300 to 1350 F temperature capabilities, dependent on detailed disk and engine design property requirements.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211796 , NAS 1.15:211796 , E-13491
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    An Interactive Excel Program for Tracking a Single Droplet in Crossflow Computation (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Spray jet in crossflow has been a subject of research because of its wide application in systems involving pollutant dispersion, jet mixing in the dilution zone of combustors, and fuel injection strategies. The focus of this work is to investigate dispersion of a 2-dimensional atomized spray jet into a 2-dimensional crossflow. A quick computational method is developed using available software. The spreadsheet can be used for any 2D droplet trajectory problem where the drop is injected into the free stream eventually coming to the free stream conditions. During the transverse injection of a spray into high velocity airflow, the droplets (carried along and deflected by a gaseous stream of co-flowing air) are subjected to forces that affect their motion in the flow field. Based on the Newton's Second Law of motion, four ordinary differential equations were used. These equations were then solved by a fourth-order Runge-Kutta method using Excel software. Visual basic programming and Excel macrocode to produce the data facilitate Excel software to plot graphs describing the droplet's motion in the flow field. This program computes and plots the data sequentially without forcing users to open other types of plotting programs. A user's manual on how to use the program is also included in this report.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211710 , E-13459 , NAS 1.15:211710
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    Computational Predictions of the Performance Wright 'Bent End' Propellers (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Computational analysis of two 1911 Wright brothers 'Bent End' wooden propeller reproductions have been performed and compared with experimental test results from the Langley Full Scale Wind Tunnel. The purpose of the analysis was to check the consistency of the experimental results and to validate the reliability of the tests. This report is one part of the project on the propeller performance research of the Wright 'Bent End' propellers, intend to document the Wright brothers' pioneering propeller design contributions. Two computer codes were used in the computational predictions. The FLO-MG Navier-Stokes code is a CFD (Computational Fluid Dynamics) code based on the Navier-Stokes Equations. It is mainly used to compute the lift coefficient and the drag coefficient at specified angles of attack at different radii. Those calculated data are the intermediate results of the computation and a part of the necessary input for the Propeller Design Analysis Code (based on Adkins and Libeck method), which is a propeller design code used to compute the propeller thrust coefficient, the propeller power coefficient and the propeller propulsive efficiency.
    Keywords: Aircraft Propulsion and Power
    Type: ODURF-101511
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    Advanced Nacelle Acoustic Lining Concepts Development (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The work reported in this document consisted of six distinct liner technology development subtasks: 1) Analysis of Model Scale ADP Fan Duct Lining Data (Boeing): An evaluation of an AST Milestone experiment to demonstrate 1995 liner technology superiority relative to that of 1992 was performed on 1:5.9 scale model fan rig (Advanced Ducted Propeller) test data acquired in the NASA Glenn 9 x 15 foot wind tunnel. The goal of 50% improvement was deemed satisfied. 2) Bias Flow Liner Investigation (Boeing, VCES): The ability to control liner impedance by low velocity bias flow through liner was demonstrated. An impedance prediction model to include bias flow was developed. 3) Grazing Flow Impedance Testing (Boeing): Grazing flow impedance tests were conducted for comparison with results achieved at four different laboratories. 4) Micro-Perforate Acoustic Liner Technology (BFG, HAE, NG): Proof of concept testing of a "linear liner." 5) Extended Reaction Liners (Boeing, NG): Bandwidth improvements for non-locally reacting liner were investigated with porous honeycomb core test liners. 6) Development of a Hybrid Active/Passive Lining Concept (HAE): Synergism between active and passive attenuation of noise radiated by a model inlet was demonstrated.
    Keywords: Acoustics
    Type: NASA/CR-2002-211672 , NAS 1.26:211672
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    Hearing Aid Assembly (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Progress in hearing aids has come a long way. Yet despite such progress hearing aids are not the perfect answer to many hearing problems. Some adult ears cannot accommodate tightly fitting hearing aids. Mouth movements such as chewing, talking, and athletic or other active endeavors also lead to loosely fitting ear molds. It is well accepted that loosely fitting hearing aids are the cause of feedback noise. Since feedback noise is the most common complaint of hearing aid wearers it has been the subject of various patents. Herein a hearing aid assembly is provided eliminating feedback noise. The assembly includes the combination of a hearing aid with a headset developed to constrict feedback noise.
    Keywords: Acoustics
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    Lobed Mixer Design for Noise Suppression: Plume, Aerodynamic and Acoustic Data (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: A comprehensive database for the acoustic and aerodynamic characteristics of several model-scale lobe mixers of bypass ratio 5 to 6 has been created for mixed jet speeds up to 1080 ft per s at typical take-off (TO) conditions of small-to-medium turbofan engines. The flight effect was simulated for Mach numbers up to 0.3. The static thrust performance and plume data were also obtained at typical TO and cruise conditions. The tests were done at NASA Lewis anechoic dome and ASE's FluiDyne Laboratories. The effect of several lobe mixer and nozzle parameters, such as, lobe scalloping, lobe count, lobe penetration and nozzle length was examined in terms of flyover noise at constant altitude and also noise in the reference frame of the nozzle. This volume is divided into three parts: in the first two parts, we collate the plume survey data in graphical form (line, contour and surface plots) and analyze it; in part 3, we tabulate the aerodynamic data for the acoustics tests and the acoustic data in one-third octave band levels.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2002-210823/VOL2 , E-12741/VOL2 , NAS 1.26:210823/VOL2 , EDR-18581/VOL2
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    Gust Acoustics Computation with a Space-Time CE/SE Parallel 3D Solver (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The benchmark Problem 2 in Category 3 of the Third Computational Aero-Acoustics (CAA) Workshop is solved using the space-time conservation element and solution element (CE/SE) method. This problem concerns the unsteady response of an isolated finite-span swept flat-plate airfoil bounded by two parallel walls to an incident gust. The acoustic field generated by the interaction of the gust with the flat-plate airfoil is computed by solving the 3D (three-dimensional) Euler equations in the time domain using a parallel version of a 3D CE/SE solver. The effect of the gust orientation on the far-field directivity is studied. Numerical solutions are presented and compared with analytical solutions, showing a reasonable agreement.
    Keywords: Acoustics
    Type: ICCFD: 2nd International Conference in Computational Fluid Dynamics; Unknown
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    Lobed Mixer Design for Noise Suppression Acoustic and Aerodynamic Test Data Analysis (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: A comprehensive database for the acoustic and aerodynamic characteristics of several model-scale lobe mixers of bypass ratio 5 to 6 has been created for mixed jet speeds up to 1080 ft/s at typical take-off (TO) conditions of small-to-medium turbofan engines. The flight effect was simulated for Mach numbers up to 0.3. The static thrust performance and plume data were also obtained at typical TO and cruise conditions. The tests were done at NASA Lewis anechoic dome and ASK's FluiDyne Laboratories. The effect of several lobe mixer and nozzle parameters, such as, lobe scalloping, lobe count, lobe penetration and nozzle length was examined in terms of flyover noise at constant altitude. Sound in the nozzle reference frame was analyzed to understand the source characteristics. Several new concepts, mechanisms and methods are reported for such lobed mixers, such as, "boomerang" scallops, "tongue" mixer, detection of "excess" internal noise sources, and extrapolation of flyover noise data from one flight speed to different flight speeds. Noise reduction of as much as 3 EPNdB was found with a deeply scalloped mixer compared to annular nozzle at net thrust levels of 9500 lb for a 29 in. diameter nozzle after optimizing the nozzle length.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2002-210823/VOL1 , NAS 1.26:210823/VOL1 , E-12741-1-VOL1 , EDR-18580/VOL1
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    High Speed Jet Noise Prediction Using Large Eddy Simulation (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Current methods for predicting the noise of high speed jets are largely empirical. These empirical methods are based on the jet noise data gathered by varying primarily the jet flow speed, and jet temperature for a fixed nozzle geometry. Efforts have been made to correlate the noise data of co-annular (multi-stream) jets and for the changes associated with the forward flight within these empirical correlations. But ultimately these emipirical methods fail to provide suitable guidance in the selection of new, low-noise nozzle designs. This motivates the development of a new class of prediction methods which are based on computational simulations, in an attempt to remove the empiricism of the present day noise predictions.
    Keywords: Acoustics
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    Recent Advances in Vibroacoustics (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Numerous vibroacoustics advances and impacts in the aerospace industry have occurred over the last 15 years. This article addresses some of these that developed from engineering programmatic task-work at the NASA Glenn Research Center at Lewis Field.
    Keywords: Acoustics
    Type: NASA/TM-2002-211697 , NAS 1.15:211697 , E-13429
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    Optimal Micro-Scale Secondary Flow Control for the Management of High Cycle Fatigue and Distortion in Compact Inlet Diffusers (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The purpose of this study on micro-scale secondary flow control (MSFC) is to study the aerodynamic behavior of micro-vane effectors through their factor (i.e., the design variable) interactions and to demonstrate how these statistical interactions, when brought together in an optimal manner, determine design robustness. The term micro-scale indicates the vane effectors are small in comparison to the local boundary layer height. Robustness in this situation means that it is possible to design fixed MSFC robust installation (i.e.. open loop) which operates well over the range of mission variables and is only marginally different from adaptive (i.e., closed loop) installation design, which would require a control system. The inherent robustness of MSFC micro-vane effector installation designs comes about because of their natural aerodynamic characteristics and the manner in which these characteristics are brought together in an optimal manner through a structured Response Surface Methodology design process.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211686 , NAS 1.15:211686 , E-13415
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    Aeroacoustic Experiments in the NASA Langley Low-Turbulence Pressure Tunnel (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: A phased microphone array was used in the NASA Langley Low-Turbulence Pressure Tunnel to obtain acoustic data radiating from high-lift wing configurations. The data included noise localization plots and acoustic spectra. The tests were performed at Reynolds numbers based on the cruise-wing chord, ranging from 3.6 x 10(exp 6) to 19.2 x 10(exp 6). The effects of Reynolds number were small and monotonic for Reynolds numbers above 7.2 x 10(exp 6).
    Keywords: Acoustics
    Type: NASA/TM-2002-211432 , L-18131
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    Design, Progressive Modeling, Manufacture, and Testing of Composite Shield for Turbine Engine Blade Containment (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: An effective design methodology was established for composite jet engine containment structures. The methodology included the development of the full and reduced size prototypes, and FEA models of the containment structure, experimental and numerical examination of the modes of failure clue to turbine blade out event, identification of materials and design candidates for future industrial applications, and design and building of prototypes for testing and evaluation purposes.
    Keywords: Aircraft Propulsion and Power
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    In situ testing of a satellite or other object prior to development (2002)
    In:  CASI
    Details
    Publication Date: 2019-08-17
    Description: A method and system for testing a test object, such as a satellite, is disclosed. High energy acoustic testing is performed on the object by assembling an acoustical system about the test object rather than transporting the test object to a specially configured acoustic chamber. The acoustic system of the present invention preferably provides and directs acoustic energy directly to the surfaces of the test object rather than providing the test object in a high energy acoustic environment where a substantial amount of the acoustic energy is randomly directed within a chamber having the test object. Additionally, the present invention further provides for mechanical vibration tests concurrently or serially with acoustic testing, wherein the object is not required to be transported.
    Keywords: Acoustics
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    Propulsion Controls and Health Management Research at NASA Glenn Research Center (2002)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: With the increased emphasis on aircraft safety, enhanced performance and affordability, and the need to reduce the environmental impact of aircraft, there are many new challenges being faced by the designers of aircraft propulsion systems. The Controls and Dynamics Technology Branch at NASA Glenn Research Center (GRC) in Cleveland, Ohio, is leading and participating in various projects in partnership with the U.S. aerospace industry and academia to develop advanced controls and health management technologies that will help meet these challenges. These technologies are being developed with a view towards making the concept of "Intelligent Engines" a reality. The major research activities of the Controls and Dynamics Technology Branch are described in the following.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211590 , E-13375 , NAS 1.15:211590 , Combustion, Airbreathing Propulsion, Propulsion Systems Hazards, and Modelling and Simulation Subcommittees Joint Meeting; Apr 08, 2002 - Apr 12, 2002; Destin, FL; United States
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    Airbreathing Pulse Detonation Engine Performance (2002)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: This paper presents performance results for pulse detonation engines (PDE) taking into account the effects of dissociation and recombination. The amount of sensible heat recovered through recombination in the PDE chamber and exhaust process was found to be significant. These results have an impact on the specific thrust, impulse and fuel consumption of the PDE.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211575 , NAS 1.15:211575 , E-13359 , ICOMP-2002-02 , Combustion, Airbreathing Propulsion, Propulsion Systems Hazards, and Modelling and Simulation Subcommittees Joint Meeting; 8-12 Apr. 202; Destin, FL; United States
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    Management of Total Pressure Recovery, Distortion and High Cycle Fatigue in Compact Air Vehicle Inlets (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: It is the purpose of this study to demonstrate the viability and economy of Response Surface Methods (RSM) and Robustness Design Concepts (RDC) to arrive at micro-secondary flow control installation designs that maintain optimal inlet performance over a range of the mission variables. These statistical design concepts were used to investigate the robustness properties of 'low unit strength' micro-effector installations. 'Low unit strength' micro-effectors are micro-vanes set at very low angles-of-incidence with very long chord lengths. They were designed to influence the near wall inlet flow over an extended streamwise distance, and their advantage lies in low total pressure loss and high effectiveness in managing engine face distortion.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-212000 , E-13672 , NAS 1.15:212000
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    CAD Services: an Industry Standard Interface for Mechanical CAD Interoperability (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Most organizations seek to design and develop new products in increasingly shorter time periods. At the same time, increased performance demands require a team-based multidisciplinary design process that may span several organizations. One approach to meet these demands is to use 'Geometry Centric' design. In this approach, design engineers team their efforts through one united representation of the design that is usually captured in a CAD system. Standards-based interfaces are critical to provide uniform, simple, distributed services that enable the 'Geometry Centric' design approach. This paper describes an industry-wide effort, under the Object Management Group's (OMG) Manufacturing Domain Task Force, to define interfaces that enable the interoperability of CAD, Computer Aided Manufacturing (CAM), and Computer Aided Engineering (CAE) tools. This critical link to enable 'Geometry Centric' design is called: Cad Services V1.0. This paper discusses the features of this standard and proposed application.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211902 , NAS 1.15:211902 , E-13590
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    Room Temperature Characterization of a Magnetic Bearing for Turbomachinery (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Open loop, experimental force and power measurements of a three-axis, radial, heteropolar magnetic bearing at room temperature for rotor speeds up to 20,000 RPM are presented in this paper. The bearing, NASA Glenn Research Center's and Texas A&M's third generation high temperature magnetic bearing, was designed to operate in a 1000 F (540 C) environment and was primarily optimized for maximum load capacity. The experimentally measured force produced by one C-core of this bearing was 630 lb. (2.8 kN) at 16 A, while a load of 650 lbs (2.89 kN) was predicted at 16 A using 1D circuit analysis. The maximum predicted radial load for one of the three axes is 1,440 lbs (6.41 kN) at room temperature. The maximum measured load of an axis was 1050 lbs. (4.73 kN). Results of test under rotating conditions showed that rotor speed has a negligible effect on the bearing's load capacity. A single C-core required approximately 70 W of power to generate 300 lb (1.34 kN) of magnetic force. The room temperature data presented was measured after three thermal cycles up to 1000 F (540 C), totaling six hours at elevated temperatures.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211904 , NAS 1.15:211904 , ARL-TR-2858 , E-13594
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    Small Engine Technology (SET). Task 33: Airframe, Integration, and Community Noise Study (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Task Order 33 had four primary objectives as follows: (1) Identify and prioritize the airframe noise reduction technologies needed to accomplish the NASA Pillar goals for business and regional aircraft. (2) Develop a model to estimate the effect of jet shear layer refraction and attenuation of internally generated source noise of a turbofan engine on the aircraft system noise. (3) Determine the effect on community noise of source noise changes of a generic turbofan engine operating from sea level to 15,000 feet. (4) Support lateral attenuation experiments conducted by NASA Langley at Wallops Island, VA, by coordinating opportunities for Contractor Aircraft to participate as a noise source during the noise measurements. Noise data and noise prediction tools, including airframe noise codes, from the NASA Advanced Subsonic Technology (AST) program were applied to assess the current status of noise reduction technologies relative to the NASA pillar goals for regional and small business jet aircraft. In addition, the noise prediction tools were applied to evaluate the effectiveness of airframe-related noise reduction concepts developed in the AST program on reducing the aircraft system noise. The AST noise data and acoustic prediction tools used in this study were furnished by NASA.
    Keywords: Acoustics
    Type: NASA/CR-2002-211670 , NAS 1.26:211670
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    Computation of High Speed Jet Noise (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The objective of this work was to use direct numerical simulation (DNS) techniques to study the physics of noise generation by a high-speed turbulent jet. A Mach 0.9, Reynolds number 3,600 jet was selected because of available experimental data. New numerical methods for generating disturbances at the nozzle and computing far-field sound were developed and reported in the course of this work. Over 25 million mesh points were used in the simulations which ran for over 50,000 timesteps and required over 50,000 processor hours on state-of-the-art parallel computer systems to complete. Figures show a visualization of the jet and sound field, a comparison of the mean flow development with the experiment, a directivity comparison with the experiment, and time spectrum comparison with the experiment. Agreement is seen to be excellent. These are fully document in the attached references. Full details of the work, detailed achievements and conclusions are discussed in appendices, which are copies of publications that resulted from this work. We have studied noise mechanisms in supersonic jets, the refraction of sound by turbulence in subsonic jets, and noise sources in conjunction with a DNS of a Mach 0.9 jet.
    Keywords: Acoustics
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    Numerical Simulations for Landing Gear Noise Generation and Radiation (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Aerodynamic noise from a landing gear in a uniform flow is computed using the Ffowcs Williams -Hawkings (FW-H) equation. The time accurate flow data on the surface is obtained using a finite volume flow solver on an unstructured and. The Ffowcs Williams-Hawkings equation is solved using surface integrals over the landing gear surface and over a permeable surface away from the landing gear. Two geometric configurations are tested in order to assess the impact of two lateral struts on the sound level and directivity in the far-field. Predictions from the Ffowcs Williams-Hawkings code are compared with direct calculations by the flow solver at several observer locations inside the computational domain. The permeable Ffowcs Williams-Hawkings surface predictions match those of the flow solver in the near-field. Far-field noise calculations coincide for both integration surfaces. The increase in drag observed between the two landing gear configurations is reflected in the sound pressure level and directivity mainly in the streamwise direction.
    Keywords: Acoustics
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    Activities of the Acoustical Society of America (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: During the period covered by this grant report, the following accomplishments were achieved: (1) 10 new American National Standards were adopted and published; (2) Five International Standards were adopted as dual-numbered American National Standards and published; (3) Six draft American National Standards were balloted (not yet adopted or published); (4) Other National Standards Ballots were processed by the Secretariat; (5) US Positions on International Standards Activities processed by the Secretariat; (6) Reporting was conducted at conferences.
    Keywords: Acoustics
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    Micro- and Macro-Fluid Dynamics and Acoustics of Resonant Liners (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: The objectives of this project are to perform direct numerical simulation of the micro-fluid and acoustic fields of a resonant acoustic liner and to investigate the physical processes by which incident sound waves are damped by the acoustic liner. We would like to report that our research work and results have fulfilled both objectives of the grant. The following is a summary of the important accomplishments: (1) Two dimensional direct numerical simulation of the flow and acoustic field around the cavity of resonant liner were successfully carried out; (2) The simulations of (1) were extended to include a laminar grazing flow; (3) The numerical simulations provided strong evidence that there are two principal mechanisms by which a resonant liner damps out an incident acoustic wave; (4) A validation test was performed by comparing the computed dissipation coefficients (not impedance) with impedance tube measurements done at GTRI; and (5) Some resources of this grant were used to support the development of new CAA methods. (Our work on numerical simulation of acoustic liners has benefited by the availability of these improved methods).
    Keywords: Acoustics
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    A Study of Standing Pressure Waves Within Open and Closed Acoustic Resonators (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The first section of the results presented herein was conducted on an axisymmetric resonator configured with open ventilation ports on either end of the resonator, but otherwise closed and free from obstruction. The remaining section presents the results of a similar resonator shape that was closed, but contained an axisymmetric blockage centrally located through the axis of the resonator. Ambient air was used as the working fluid. In each of the studies, the resonator was oscillated at the resonant frequency of the fluid contained within the cavity while the dynamic pressure, static pressure, and temperature of the fluid were recorded at both ends of the resonator. The baseline results showed a marked reduction in the amplitude of the dynamic pressure waveforms over previous studies due to the use of air instead of refrigerant as the working fluid. A sharp reduction in the amplitude of the acoustic pressure waves was expected and recorded when the configuration of the resonators was modified from closed to open. A change in the resonant frequency was recorded when blockages of differing geometries were used in the closed resonator, while acoustic pressure amplitudes varied little from baseline measurements.
    Keywords: Acoustics
    Type: 145th Acoustic Society of America Conference; Dec 02, 2002 - Dec 06, 2002; Cancun; Mexico
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    Power Measurement Errors on a Utility Aircraft (2002)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Extensive flight test data obtained from two recent performance tests of a UH 60A aircraft are reviewed. A power difference is calculated from the power balance equation and is used to examine power measurement errors. It is shown that the baseline measurement errors are highly non-Gaussian in their frequency distribution and are therefore influenced by additional, unquantified variables. Linear regression is used to examine the influence of other variables and it is shown that a substantial portion of the variance depends upon measurements of atmospheric parameters. Correcting for temperature dependence, although reducing the variance in the measurement errors, still leaves unquantified effects. Examination of the power difference over individual test runs indicates significant errors from drift, although it is unclear how these may be corrected. In an idealized case, where the drift is correctable, it is shown that the power measurement errors are significantly reduced and the error distribution is Gaussian. A new flight test program is recommended that will quantify the thermal environment for all torque measurements on the UH 60. Subsequently, the torque measurement systems will be recalibrated based on the measured thermal environment and a new power measurement assessment performed.
    Keywords: Aircraft Propulsion and Power
    Type: American Helicopter Society Aerodynamics, Acoustics and Test and Evaluation Technical Specialist Meeting; Jan 23, 2002 - Jan 25, 2002; San Francisco, CA; United States
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    Simultaneous Laser Raman-rayleigh-lif Measurements and Numerical Modeling Results of a Lifted Turbulent H2/N2 Jet Flame in a Vitiated Coflow (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An experiment and numerical investigation is presented of a lifted turbulent H2/N2 jet flame in a coflow of hot, vitiated gases. The vitiated coflow burner emulates the coupling of turbulent mixing and chemical kinetics exemplary of the reacting flow in the recirculation region of advanced combustors. It also simplifies numerical investigation of this coupled problem by removing the complexity of recirculating flow. Scalar measurements are reported for a lifted turbulent jet flame of H2/N2 (Re = 23,600, H/d = 10) in a coflow of hot combustion products from a lean H2/Air flame ((empty set) = 0.25, T = 1,045 K). The combination of Rayleigh scattering, Raman scattering, and laser-induced fluorescence is used to obtain simultaneous measurements of temperature and concentrations of the major species, OH, and NO. The data attest to the success of the experimental design in providing a uniform vitiated coflow throughout the entire test region. Two combustion models (PDF: joint scalar Probability Density Function and EDC: Eddy Dissipation Concept) are used in conjunction with various turbulence models to predict the lift-off height (H(sub PDF)/d = 7,H(sub EDC)/d = 8.5). Kalghatgi's classic phenomenological theory, which is based on scaling arguments, yields a reasonably accurate prediction (H(sub K)/d = 11.4) of the lift-off height for the present flame. The vitiated coflow admits the possibility of auto-ignition of mixed fluid, and the success of the present parabolic implementation of the PDF model in predicting a stable lifted flame is attributable to such ignition. The measurements indicate a thickened turbulent reaction zone at the flame base. Experimental results and numerical investigations support the plausibility of turbulent premixed flame propagation by small scale (on the order of the flame thickness) recirculation and mixing of hot products into reactants and subsequent rapid ignition of the mixture.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2002-212082 , NAS 1.26:212082 , E-13735 , 29th International Symposium on Combustion; Jul 21, 2002 - Jul 26, 2002; Sapporo; Japan
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    Thrust Augmentation with Mixer/Ejector Systems (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Older commercial aircraft often exceed FAA (Federal Aviation Administration) sideline noise regulations. The major problem is the jet noise associated with the high exhaust velocities of the low bypass ratio engines on such aircraft. Mixer/ejector exhaust systems can provide a simple means of reducing the jet noise on these aircraft by mixing cool ambient air with the high velocity engine gases before they are exhausted to ambient. This paper presents new information on thrust performance predictions, and thrust augmentation capabilities of mixer/ejectors. Results are presented from the recent development program of the patented Alternating Lobe Mixer Ejector Concept (ALMEC) suppressor system for the Gulfstream GII, GIIB and GIII aircraft. Mixer/ejector performance procedures are presented which include classical control volume analyses, compound compressible flow theory, lobed nozzle loss correlations and state of the art computational fluid dynamic predictions. The mixer/ejector thrust predictions are compared to subscale wind tunnel test model data and actual aircraft flight test measurements. The results demonstrate that a properly designed mixer/ejector noise suppressor can increase effective engine bypass ratio and generate large thrust gains at takeoff conditions with little or no thrust loss at cruise conditions. The cruise performance obtained for such noise suppressor systems is shown to be a strong function of installation effects on the aircraft.
    Keywords: Aircraft Propulsion and Power
    Type: AIAA Paper 2002-0230 , 40th AIAA Aerospace Sciences Meeting and Exhibit; Jan 14, 2002 - Jan 17, 2002; Reno, NV; United States
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    Unsteady Ejector Performance: An Experimental Investigation Using a Resonance Tube Driver (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A statistically designed experiment to characterize thrust augmentation for unsteady ejectors has been conducted at the NASA Glenn Research Center. The variable parameters included ejector diameter, length, and nose radius. The pulsed jet driving the ejectors was produced by a shrouded resonance (or Hartmann-Sprenger) tube. In contrast to steady ejectors, an optimum ejector diameter was found, which coincided with the diameter of the vortex ring created at the pulsed jet exit. Measurements of ejector exit velocity using a hot-wire permitted evaluation of the mass augmentation ratio, which was found to correlate to thrust augmentation following a formula derived for steady ejectors.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211474 , E-13239 , NAS 1.15:211474 , AIAA Paper 2002-3632 , 38th Joint Propulsion Conference and Exhibit; Jul 07, 2002 - Jul 10, 2002; Indianapolis, IN; United States
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    A Method for Optimizing Non-Axisymmetric Liners for Multimodal Sound Sources (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Central processor unit times and memory requirements for a commonly used solver are compared to that of a state-of-the-art, parallel, sparse solver. The sparse solver is then used in conjunction with three constrained optimization methodologies to assess the relative merits of non-axisymmetric versus axisymmetric liner concepts for improving liner acoustic suppression. This assessment is performed with a multimodal noise source (with equal mode amplitudes and phases) in a finite-length rectangular duct without flow. The sparse solver is found to reduce memory requirements by a factor of five and central processing time by a factor of eleven when compared with the commonly used solver. Results show that the optimum impedance of the uniform liner is dominated by the least attenuated mode, whose attenuation is maximized by the Cremer optimum impedance. An optimized, four-segmented liner with impedance segments in a checkerboard arrangement is found to be inferior to an optimized spanwise segmented liner. This optimized spanwise segmented liner is shown to attenuate substantially more sound than the optimized uniform liner and tends to be more effective at the higher frequencies. The most important result of this study is the discovery that when optimized, a spanwise segmented liner with two segments gives attenuations equal to or substantially greater than an optimized axially segmented liner with the same number of segments.
    Keywords: Acoustics
    Type: AIAA Paper 2002-2516 , 8th AIAA/CEAS Aeroacoustics Conference; Jun 17, 2002 - Jun 19, 2002; Breckenridge, CO; United States
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    Acoustic Bubble Removal from Boiling Surfaces (2002)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The object of the study was the investigation of the forces generated by standing acoustic waves on vapor bubbles, both far and near boundaries. In order to accomplish this objective, in view of the scarcity of publications on the topic, it has been necessary to build an edifice of knowledge about vapor bubbles in sound and flow fields from the ground up, as it were. We have addressed problems of gradually greater difficulty as follows: 1. In the first place, the physics of an stationary isolated bubble subject to a sound field in an unbounded liquid was addressed; 2. The case of bubbles translating in a stationary pressure field was then considered; 3. This was followed by a study of the combined effects of sound and translation, 4. And of a neighboring boundary 5. Finally, a new method to deal with nonspherical bubbles was developed- In addition to the work on vapor bubbles, some studies on gas bubbles were conducted in view of NASA's interest in the phenomenon of sonoluminescence.
    Keywords: Acoustics
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    Overview of High-Fidelity Modeling Activities in the Numerical Propulsion System Simulations (NPSS) Project (2002)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A high-fidelity simulation of a commercial turbofan engine has been created as part of the Numerical Propulsion System Simulation Project. The high-fidelity computer simulation utilizes computer models that were developed at NASA Glenn Research Center in cooperation with turbofan engine manufacturers. The average-passage (APNASA) Navier-Stokes based viscous flow computer code is used to simulate the 3D flow in the compressors and turbines of the advanced commercial turbofan engine. The 3D National Combustion Code (NCC) is used to simulate the flow and chemistry in the advanced aircraft combustor. The APNASA turbomachinery code and the NCC combustor code exchange boundary conditions at the interface planes at the combustor inlet and exit. This computer simulation technique can evaluate engine performance at steady operating conditions. The 3D flow models provide detailed knowledge of the airflow within the fan and compressor, the high and low pressure turbines, and the flow and chemistry within the combustor. The models simulate the performance of the engine at operating conditions that include sea level takeoff and the altitude cruise condition.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211351 , NAS 1:15:211351 , E-13169 , Aerospace Numerical Simulation Symposium; Jun 20, 2001 - Jun 22, 2001; Tokyo; Japan
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    Revolutionary/Unconventional Aeropropulsion Technology Evaluation through Thermodynamic Work Potential: A Revolutionary Aeropropulsion Concepts Program Research Initiative (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This report is intended as a status report for activities covered May through July 2002 under the auspices of NASA Glenn's Revolutionary Aeropropulsion Concepts (RAC) project. This is the first phase I quarterly report and as such, considerable focus will be given to defining the basic need and motivation driving this research effort. In addition, background research has been ongoing for the past several months and has culminated in considerable information pertaining to the state-of-the-art in work potential analysis methods. This work is described in detail herein. Finally, the proposed analysis approach is described, as are the various ancillary concepts required for its implementation.
    Keywords: Aircraft Propulsion and Power
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    Filtered Mass Density Function for Design Simulation of High Speed Airbreathing Propulsion Systems (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The objective of this research is to improve and implement the filtered mass density function (FDF) methodology for large eddy simulation (LES) of high speed reacting turbulent flows. NASA is interested in the design of various components involved in air breathing propulsion systems such as the scramjet. There is a demand for development of robust tools that can aid in the design procedure. The physics of high speed reactive flows is rich with many complexities. LES is regarded as one of the most promising means of simulating turbulent reacting flows.
    Keywords: Aircraft Propulsion and Power
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    Adaptive Instability Suppression Controls in a Liquid-fueled Combustor (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An adaptive control algorithm has been developed for the suppression of combustion thermo-acoustic instabilities. This technique involves modulating the fuel flow in the combustor with a control phase that continuously slides within the stable phase region, in a back and forth motion. The control method is referred to as Adaptive Sliding Phasor Averaged Control (ASPAC). The control method is evaluated against a simplified simulation of the combustion instability. Plans are to validate the control approach against a more physics-based model and an actual experimental combustor rig.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211805 , NAS 1.15:211805 , E-13500 , AIAA Paper 2002-4075 , 38th Joint Propulsion Conference and Exhibit; Jul 07, 2002 - Jul 10, 2002; Indianapolis, IN; United States
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    Conceptual Design of a Supersonic Business Jet Propulsion System (2002)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: NASA's Ultra-Efficient Engine Technology Program (UEETP) is developing a suite of technology to enhance the performance of future aircraft propulsion systems. Areas of focus for this suite of technology include: Highly Loaded Turbomachinery, Emissions Reduction, Materials and Structures, Controls, and Propulsion-Airframe Integration. The two major goals of the UEETP are emissions reduction of both landing and take-off nitrogen oxides (LTO-NO(x)) and mission carbon dioxide (CO2) through fuel burn reductions. The specific goals include a 70 percent reduction in the current LTO-NO(x) rule and an 8 percent reduction in mission CO2 emissions. In order to gain insight into the potential applications and benefits of these technologies on future aircraft, a set of representative flight vehicles was selected for systems level conceptual studies. The Supersonic Business Jet (SBJ) is one of these vehicles. The particular SBJ considered in this study has a capacity of 6 passengers, cruise Mach Number of 2.0, and a range of 4,000 nautical miles. Without the current existence of an SBJ the study of this vehicle requires a two-phased approach. Initially, a hypothetical baseline SBJ is designed which utilizes only current state of the art technology. Finally, an advanced SBJ propulsion system is designed and optimized which incorporates the advanced technologies under development within the UEETP. System benefits are then evaluated and compared to the program and design requirements. Although the program goals are only concerned with LTO-NO(x) and CO2 emissions, it is acknowledged that additional concerns for an SBJ include take-off noise, overland supersonic flight, and cruise NO(x) emissions at high altitudes. Propulsion system trade-offs in the conceptual design phase acknowledge these issues as well as the program goals. With the inclusion of UEETP technologies a propulsion system is designed which performs at 81% below the LTO-NO(x) rule, and reduces fuel burn by 23 percent compared to the current technology.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211797 , E-13492 , NAS 1.15:211797 , AIAA Paper 2002-3919 , 38th Joint Propulsion Conference and Exhibit; Jul 07, 2002 - Jul 10, 2002; Indianapolis, IN; United States
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    Fan Noise Source Diagnostic Test: Vane Unsteady Pressure Results (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: To investigate the nature of fan outlet guide vane pressure fluctuations and their link to rotor-stator interaction noise, time histories of vane fluctuating pressures were digitally acquired as part of the Fan Noise Source Diagnostic Test. Vane unsteady pressures were measured at seven fan tip speeds for both a radial and a swept vane configuration. Using time-domain averaging and spectral analysis, the blade passing frequency (BPF) harmonic and broadband contents of the vane pressures were individually analyzed. Significant Sound Pressure Level (SPL) reductions were observed for the swept vane relative to the radial vane for the BPF harmonics of vane pressure, but vane broadband reductions due to sweep turned out to be much smaller especially on an average basis. Cross-correlation analysis was used to establish the level of spatial coherence of broadband pressures between different locations on the vane and integral length scales of pressure fluctuations were estimated from these correlations. Two main results of this work are: (1) the average broadband level on the vane (in dB) increases linearly with the fan tip speed for both the radial and swept vanes, and (2) the broadband pressure distribution on the vane is nearly homogeneous and its integral length scale is a monotonically decreasing function of fan tip speed.
    Keywords: Acoustics
    Type: NASA/TM-2002-211808 , NAS 1.15:211808 , E-13503 , AIAA Paper 2002-2430 , Eighth Aeroacoustics Conference; Jun 17, 2002 - Jun 19, 2002; Breckenridge, CO; United States
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    Flutter Analysis of a Transonic Fan (2002)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: This paper describes the calculation of flutter stability characteristics for a transonic forward swept fan configuration using a viscous aeroelastic analysis program. Unsteady Navier-Stokes equations are solved on a dynamically deforming, body fitted, grid to obtain the aeroelastic characteristics using the energy exchange method. The non-zero inter-blade phase angle is modeled using phase-lagged boundary conditions. Results obtained show good correlation with measurements. It is found that the location of shock and variation of shock strength strongly influenced stability. Also, outboard stations primarily contributed to stability characteristics. Results demonstrate that changes in blade shape impact the calculated aerodynamic damping, indicating importance of using accurate blade operating shape under centrifugal and steady aerodynamic loading for flutter prediction. It was found that the calculated aerodynamic damping was relatively insensitive to variation in natural frequency.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211818 , E-13511 , NAS 1.15:211818 , Turbo Expo 2002; Jun 03, 2002 - Jun 06, 2002; Amsterdam; Netherlands
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    Low-Speed Fan Noise Reduction With Trailing Edge Blowing (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An experimental proof-of-concept test was conducted to demonstrate reduction of rotor-stator interaction noise through rotor-trailing edge blowing. The velocity deficit from the viscous wake of the rotor blades was reduced by injecting air into the wake from a trailing edge slot. Composite hollow rotor blades with internal flow passages were designed based on analytical codes modeling the internal flow. The hollow blade with interior guide vanes creates flow channels through which externally supplied air flows from the root of the blade to the trailing edge. The impact of the rotor wake-stator interaction on the acoustics was also predicted analytically. The Active Noise Control Fan, located at the NASA Glenn Research Center, was used as the proof- of-concept test bed. In-duct mode and farfield directivity acoustic data were acquired at blowing rates (defined as mass supplied to trailing edge blowing system divided by fan mass flow) ranging from 0.5 to 2.0 percent. The first three blade passing frequency harmonics at fan rotational speeds of 1700 to 1900 rpm were analyzed. The acoustic tone power levels (PWL) in the inlet and exhaust were reduced 11.5 and -0.1, 7.2 and 11.4, 11.8 and 19.4 PWL dB, respectively. The farfield tone power levels at the first three harmonics were reduced 5.4, 10.6, and 12.4 dB PWL. At selected conditions, two-component hotwire and stator vane unsteady surface pressures were acquired. These measurements illustrate the physics behind the noise reduction.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211559 , NAS 1.15:211559 , E-13339 , Eighth Aeroacoustics Conference; Jun 17, 2002 - Jun 19, 2002; Breckenridge, CO; United States
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    A Low NO(x) Lean-Direct Injection, Multipoint Integrated Module Combuster Concept for Advanced Aircraft Gas Turbines (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A low NO(x) emissions combustor has been demonstrated in flame-tube tests. A multipoint, lean-direct injection concept was used. Configurations were tested that had 25- and 36- fuel injectors in the size of a conventional single fuel injector. An integrated-module approach was used for the construction where chemically etched laminates, diffusion bonded together, combine the fuel injectors, air swirlers and fuel manifold into a single element. Test conditions were inlet temperatures up to 810 K, inlet pressures up to 2760 kPa, and flame temperatures up to 2100 K. A correlation was developed relating the NO(x) emissions with the inlet temperature, inlet pressure, fuel-air ratio and pressure drop. Assuming that 10 percent of the combustion air would be used for liner cooling and using a hypothetical engine cycle, the NO(x) emissions using the correlation from flame-tube tests were estimated to be less than 20 percent of the 1996 ICAO standard.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211347 , NAS 1.15:211347 , E-13163 , Conference on Technologies and Combustion for a Clean Environment; Jul 09, 2001 - Jul 12, 2001; Oporto; Portugal
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    Unsteady Pressures in a Transonic Fan Cascade Due to a Single Oscillating Airfoil (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An extensive set of unsteady pressure data was acquired along the midspan of a modern transonic fan blade for simulated flutter conditions. The data set was acquired in a nine-blade linear cascade with an oscillating middle blade to provide a database for the influence coefficient method to calculate instantaneous blade loadings. The cascade was set for an incidence of 10 dg. The data were acquired on three stationary blades on each side of the middle blade that was oscillated at an amplitude of 0.6 dg. The matrix of test conditions covered inlet Mach numbers of 0.5, 0.8, and 1.1 and the oscillation frequencies of 200, 300, 400, and 500 Hz. A simple quasiunsteady two-dimensional computer simulation was developed to aid in the running of the experimental program. For high Mach number subsonic inlet flows the blade pressures exhibit very strong, low-frequency, self-induced oscillations even without forced blade oscillations, while for low subsonic and supersonic inlet Mach numbers the blade pressure unsteadiness is quite low. The amplitude of forced pressure fluctuations on neighboring stationary blades strongly depends on the inlet Mach number and forcing frequency. The flowfield behavior is believed to be governed by strong nonlinear effects due to a combination of viscosity, compressibility, and unsteadiness. Therefore, the validity of the quasi-unsteady simplified computer simulation is limited to conditions when the flowfield is behaving in a linear, steady manner. Finally, an extensive set of unsteady pressure data was acquired to help development and verification of computer codes for blade flutter effects.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211723 , E-13474 , GT-2002-30312 , NAS 1.15:211723 , Turbo Expo 2002; Jun 03, 2002 - Jun 06, 2002; Amsterdam; Netherlands
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    Specialized Data Analysis and Enhanced Diagnostic System Development for Advanced Propulsion Systems (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The September 2002 activities are described. These encompassed multiple hardware, software, and computer system administration activities in support of the Space Transportation Directorate.
    Keywords: Aircraft Propulsion and Power
    Type: TR-4025-02-09
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    Effects of High-Temperature Exposures on the Fatigue Life of Superalloy Udimet(Registered Trademark) 720 (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The purpose of this study was to examine the effects of extended exposures on the near-surface fatigue resistance of a disk superalloy. Powder metallurgy processed, supersolvus heat-treated Udimet 720 (U720) fatigue specimens were exposed in air at temperatures from 650 to 705 C for 100 hr to over 1000 hr. They were then tested using conventional fatigue tests at 650 C to determine the effects of exposure on fatigue resistance. The exposures reduced life by up to 70% and increased the scatter in life, compared to unexposed levels. Fractographic evaluations indicated the failure mode was shifted by the exposures from internal to surface crack initiations. The increased scatter in life was related to the competition between internal crack initiations at inclusions or large grains producing longer lives, and surface crack initiations at an environmentally affected surface layer producing shorter lives.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211570 , NAS 1.15:211570 , E-13354 , 131st Annual Meeting and Exhibition; Feb 17, 2002 - Feb 21, 2002; Seattle, WA; United States
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    Initial Assessment of the Effects of Nonmetallic Inclusions on Fatigue Life of Powder-Metallurgy-Processed Udimet(TM) 720 (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The fatigue lives of modern powder metallurgy (PM) disk alloys are influenced by variabilities in alloy microstructure and mechanical properties. These properties can vary due to the different steps of materials/component processing and machining. One of these variables, the presence of nonmetallic inclusions, has been shown to significantly degrade low-cycle fatigue (LCF) life. Nonmetallic inclusions are inherent defects in powder alloys that are a by-product of powder-processing techniques. Contamination of the powder can occur in the melt, during powder atomization, or during any of the various handling processes through consolidation. In modern nickel disk powder processing facilities, the levels of inclusion contamination have been reduced to less than 1 part per million by weight. Despite the efforts of manufacturers to ensure the cleanliness of their powder production processes, the presence of inclusions remains a source of great concern for the designer. the objective of this study was to investigate the effects on fatigue life of these inclusions. Since natural inclusions occur so infrequently, elevated levels of inclusions were carefully introduced in a nickel-based disk superalloy, Udimet 720 (registered trademark of Special Metals Corporation), produced using PM processing. Multiple strain-controlled fatigue tests were then performed on this material at 650 C. Analyses were performed to compare the LCF lives and failure initiation sites as functions of inclusion content and fatigue conditions. A large majority of the failures in specimens with introduced inclusions occurred at cracks initiating from inclusions at the specimen surface. The inclusions could reduce fatigue life by up to 100 times. These effects were found to be dependent on strain range and strain ratio. Tests at lower strain ranges and higher strain ratios produced larger effects of inclusions on life.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211571 , E-13355 , NAS 1.15:211571 , ARL-TR-2804 , Advanced Materials and Processes for Gas Turbines Symposium; Sep 22, 2002 - Sep 26, 2002; Copper Mountain, CO; United States
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    Computational AeroAcoustics for Fan Noise Prediction (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An overview of the current state-of-the-art in computational aeroacoustics as applied to fan noise prediction at NASA Glenn is presented. Results from recent modeling efforts using three dimensional inviscid formulations in both frequency and time domains are summarized. In particular, the application of a frequency domain method, called LINFLUX, to the computation of rotor-stator interaction tone noise is reviewed and the influence of the background inviscid flow on the acoustic results is analyzed. It has been shown that the noise levels are very sensitive to the gradients of the mean flow near the surface and that the correct computation of these gradients for highly loaded airfoils is especially problematic using an inviscid formulation. The ongoing development of a finite difference time marching code that is based on a sixth order compact scheme is also reviewed. Preliminary results from the nonlinear computation of a gust-airfoil interaction model problem demonstrate the fidelity and accuracy of this approach. Spatial and temporal features of the code as well as its multi-block nature are discussed. Finally, latest results from an ongoing effort in the area of arbitrarily high order methods are reviewed and technical challenges associated with implementing correct high order boundary conditions are discussed and possible strategies for addressing these challenges ore outlined.
    Keywords: Acoustics
    Type: NONP-NASA-DK-2002123074 , Rolls-Royce Corporation; May 21, 2002; Indianapolis, IN; United States
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    Simultaneous Raman-Rayleigh-LIF Measurements and Numerical Modeling Results of a Lifted H2/N2 Turbulent Jet Flame in a Vitiated Coflow (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An experimental and numerical investigation is presented of a H2/N2 turbulent jet flame burner that has a novel vitiated coflow. The vitiated coflow emulates the recirculation region of most combustors, such as gas turbines or furnaces. Additionally, since the vitiated gases are coflowing, the burner allows for exploration of recirculation chemistry without the corresponding fluid mechanics of recirculation. Thus the vitiated coflow burner design facilitates the development of chemical kinetic combustion models without the added complexity of recirculation fluid mechanics. Scalar measurements are reported for a turbulent jet flame of H2/N2 in a coflow of combustion products from a lean ((empty set) = 0.25) H2/Air flame. The combination of laser-induced fluorescence, Rayleigh scattering, and Raman scattering is used to obtain simultaneous measurements of the temperature, major species, as well as OH and NO. Laminar flame calculation with equal diffusivity do agree when the premixing and preheating that occurs prior to flame stabilization is accounted for in the boundary conditions. Also presented is an exploratory pdf model that predicts the flame's axial profiles fairly well, but does not accurately predict the lift-off height.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/CR-2002-212081 , NAS 1.26:212081 , E-13734 , WSS/CI-2001-288 , 2001 Spring Joint Meeting; Mar 26, 2001 - Mar 28, 2001; Berkeley, CA; United States
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  • 95
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    Thermodynamic Cycle and CFD Analyses for Hydrogen Fueled Air-breathing Pulse Detonation Engines (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: This paper presents the results of a thermodynamic cycle analysis of a pulse detonation engine (PDE) using a hydrogen-air mixture at static conditions. The cycle performance results, namely the specific thrust, fuel consumption and impulse are compared to a single cycle CFD analysis for a detonation tube which considers finite rate chemistry. The differences in the impulse values were indicative of the additional performance potential attainable in a PDE.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211698 , NAS 1.15:211698 , E-13431 , ICOMP-2002-03 , AIAA Paper 2002-3629 , 38th Joint Propulsion Conference and Exhibit; Jul 07, 2002 - Jul 10, 2002; Indianapolis, IN; United States
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    Fan Noise Source Diagnostic Test Computation of Rotor Wake Turbulence Noise (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An important source mechanism of fan broadband noise is the interaction of rotor wake turbulence with the fan outlet guide vanes. A broadband noise model that utilizes computed rotor flow turbulence from a RANS code is used to predict fan broadband noise spectra. The noise model is employed to examine the broadband noise characteristics of the 22-inch Source Diagnostic Test fan rig for which broadband noise data were obtained in wind tunnel tests at the NASA Glenn Research Center. A 9-case matrix of three outlet guide vane configurations at three representative fan tip speeds are considered. For all cases inlet and exhaust acoustic power spectra are computed and compared with the measured spectra where possible. In general, the acoustic power levels and shape of the predicted spectra are in good agreement with the measured data. The predicted spectra show the experimentally observed trends with fan tip speed, vane count, and vane sweep. The results also demonstrate the validity of using CFD-based turbulence information for fan broadband noise calculations.
    Keywords: Acoustics
    Type: NASA/TM-2002-211798 , NAS 1.15:211798 , E-13493 , AIAA Paper 2002-2489 , Eighth Aeroacoustics Conference; Jun 17, 2002 - Jun 19, 2002; Breckenridge, CO; United States
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    High-Speed, High-Temperature Finger Seal Test Results (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Finger seals have significantly lower leakage rates than conventional labyrinth seals used in gas turbine engines and are expected to decrease specific fuel consumption by over 1 percent and to decrease direct operating cost by over 0.5 percent. Their compliant design accommodates shaft growth and motion due to thermal and dynamic loads with minimal wear. The cost to fabricate these finger seals is estimated to be about half the cost to fabricate brush seals. A finger seal has been tested in NASA's High Temperature, High Speed Turbine Seal Test Rig at operating conditions up to 1200 F, 1200 ft/s, and 75 psid. Static, performance and endurance test results are presented. While seal leakage and wear performance are acceptable, further design improvements are needed to reduce the seal power loss.
    Keywords: Aircraft Propulsion and Power
    Type: NASA/TM-2002-211589 , E-13374 , NAS 1.15:211589 , ARL-TR-2781 , AIAA Paper 2002-3793 , 38th Joint Propulsion Conference and Exhibit; Jul 07, 2002 - Jul 10, 2002; Indianapolis, IN; United States
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    Towards Arbitrary Accuracy Inviscid Surface Boundary Conditions (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Inviscid nonlinear surface boundary conditions are currently limited to third order accuracy in time for non-moving surfaces and actually reduce to first order in time when the surfaces move. For steady-state calculations it may be possible to achieve higher accuracy in space, but high accuracy in time is required for efficient simulation of multiscale unsteady phenomena. A surprisingly simple technique is shown here that can be used to correct the normal pressure derivatives of the flow at a surface on a Cartesian grid so that arbitrarily high order time accuracy is achieved in idealized cases. This work demonstrates that nonlinear high order time accuracy at a solid surface is possible and desirable, but it also shows that the current practice of only correcting the pressure is inadequate.
    Keywords: Acoustics
    Type: NASA/TM-2002-211583 , NAS 1.15:211583 , E-13368 , ICOMP-2002-04 , AIAA Paper 2002-2438 , Eight Aeroacoustics Conference; Jun 17, 2002 - Jun 19, 2002; Breckenridge, CO; United States
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    Measurement of Trailing Edge Noise Using Directional Array and Coherent Output Power Methods (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The use of a directional (or phased) array of microphones for the measurement of trailing edge (TE) noise is described and tested. The capabilities of this method arc evaluated via measurements of TE noise from a NACA 63-215 airfoil model and from a cylindrical rod. This TE noise measurement approach is compared to one that is based on thc cross spectral analysis of output signals from a pair of microphones placed on opposite sides of an airframe model (COP method). Advantages and limitations of both methods arc examined. It is shown that the microphone array can accurately measures TE noise and captures its two-dimensional characteristic over a large frequency range for any TE configuration as long as noise contamination from extraneous sources is within bounds. The COP method is shown to also accurately measure TE noise but over a more limited frequency range that narrows for increased TE thickness. Finally, the applicability and generality of an airfoil self-noise prediction method was evaluated via comparison to the experimental data obtained using the COP and array measurement methods. The predicted and experimental results are shown to agree over large frequency ranges.
    Keywords: Acoustics
    Type: AIAA Paper 2002-2472 , 8th AIAA/CEAS Aeroacoustics Conference; Jun 17, 2002 - Jun 19, 2002; Breckenridge, CO; United States
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    Aeroacoustic Measurements of a Wing/Slat Model (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Aeroacoustic evaluations of high-lift devices have been carried out in the Quiet Flow Facility of the NASA Langley Research Center. The present paper deals with detailed flow and acoustic measurements that have been made to understand, and to possibly predict and reduce, the noise from a wing leading edge slat configuration. The acoustic database is obtained by a moveable Small Aperture Directional Array (SADA) of microphones designed to electronically steer to different portions of models under study. The slat is shown to be a uniform distributed noise source. The data was processed such that spectra and directivity were determined with respect to a one-foot span of slat. The spectra are normalized in various fashions to demonstrate slat noise character. In order to equate portions of the spectra to different slat noise components, trailing edge noise predictions using measured slat boundary layer parameters as inputs are compared to the measured slat noise spectra.
    Keywords: Acoustics
    Type: AIAA Paper 2002-2604 , 8th AIAA/CEAS Aeroacoustics Conference; Jun 17, 2002 - Jun 19, 2002; Breckenridge, CO; United States
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