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  • 1
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    Validation of the Predicted Circumferential and Radial Mode Sound Power Levels in the Inlet and Exhaust Ducts of a Fan Ingesting Distorted Inflow (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Fan inflow distortion tone noise has been studied computationally and experimentally. Data from two experiments in the NASA Glenn Advanced Noise Control Fan rig have been used to validate acoustic predictions. The inflow to the fan was distorted by cylindrical rods inserted radially into the inlet duct one rotor chord length upstream of the fan. The rods were arranged in both symmetric and asymmetric circumferential patterns. In-duct and farfield sound pressure level measurements were recorded. It was discovered that for positive circumferential modes, measured circumferential mode sound power levels in the exhaust duct were greater than those in the inlet duct and for negative circumferential modes, measured total circumferential mode sound power levels in the exhaust were less than those in the inlet. Predicted trends in overall sound power level were proven to be useful in identifying circumferentially asymmetric distortion patterns that reduce overall inlet distortion tone noise, as compared to symmetric arrangements of rods. Detailed comparisons between the measured and predicted radial mode sound power in the inlet and exhaust duct indicate limitations of the theory.
    Keywords: Acoustics
    Type: NASA/TM-2012-217253 , AIAA Paper-2011-2808 , E-18008 , 17th Aeroacoustics Conference; Jun 05, 2011 - Jun 08, 2011; Portland, OR; United States
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  • 2
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    Tone Noise Predictions for a Spacecraft Cabin Ventilation Fan Ingesting Distorted Inflow and the Challenges of Validation (2011)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A fan tone noise prediction code has been developed at NASA Glenn Research Center that is capable of estimating duct mode sound power levels for a fan ingesting distorted inflow. This code was used to predict the circumferential and radial mode sound power levels in the inlet and exhaust duct of an axial spacecraft cabin ventilation fan. Noise predictions at fan design rotational speed were generated. Three fan inflow conditions were studied: an undistorted inflow, a circumferentially symmetric inflow distortion pattern (cylindrical rods inserted radially into the flowpath at 15deg, 135deg, and 255deg), and a circumferentially asymmetric inflow distortion pattern (rods located at 15deg, 52deg and 173deg). Noise predictions indicate that tones are produced for the distorted inflow cases that are not present when the fan operates with an undistorted inflow. Experimental data are needed to validate these acoustic predictions, as well as the aerodynamic performance predictions. Given the aerodynamic design of the spacecraft cabin ventilation fan, a mechanical and electrical conceptual design study was conducted. Design features of a fan suitable for obtaining detailed acoustic and aerodynamic measurements needed to validate predictions are discussed.
    Keywords: Acoustics
    Type: E-18071 , E-18071-1 , NOISE-CON 2011; Jul 25, 2011 - Jul 27, 2011; Portland, OR; United States
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  • 3
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    Acoustic Measurements of an Uninstalled Spacecraft Cabin Ventilation Fan Prototype (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Sound pressure measurements were recorded for a prototype of a spacecraft cabin ventilation fan in a test in the NASA Glenn Acoustical Testing Laboratory. The axial fan is approximately 0.089 m (3.50 in.) in diameter and 0.223 m (9.00 in.) long and has nine rotor blades and eleven stator vanes. At design point of 12,000 rpm, the fan was predicted to produce a flow rate of 0.709 cu m/s (150 cfm) and a total pressure rise of 925 Pa (3.72 in. of water) at 12,000 rpm. While the fan was designed to be part of a ducted atmospheric revitalization system, no attempt was made to throttle the flow or simulate the installed configuration during this test. The fan was operated at six speeds from 6,000 to 13,500 rpm. A 13-microphone traversing array was used to collect sound pressure measurements along two horizontal planes parallel to the flow direction, two vertical planes upstream of the fan inlet and two vertical planes downstream of the fan exhaust. Measurements indicate that sound at blade passing frequency harmonics contribute significantly to the overall audible noise produced by the fan at free delivery conditions.
    Keywords: Acoustics
    Type: NASA/TM-2012-217692 , E-18375 , 12_158 , Inter-Noise 2012, The 41st International Congress and Exposition on Noise Control Engineering; Aug 19, 2012 - Aug 22, 2012; New York, NY; United States
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  • 4
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    Predicting the Inflow Distortion Tone Noise of the NASA Glenn Advanced Noise Control Fan with a Combined Quadrupole-Dipole Model (2012)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A combined quadrupole-dipole model of fan inflow distortion tone noise has been extended to calculate tone sound power levels generated by obstructions arranged in circumferentially asymmetric locations upstream of a rotor. Trends in calculated sound power level agreed well with measurements from tests conducted in 2007 in the NASA Glenn Advanced Noise Control Fan. Calculated values of sound power levels radiated upstream were demonstrated to be sensitive to the accuracy of the modeled wakes from the cylindrical rods that were placed upstream of the fan to distort the inflow. Results indicate a continued need to obtain accurate aerodynamic predictions and measurements at the fan inlet plane as engineers work towards developing fan inflow distortion tone noise prediction tools.
    Keywords: Acoustics
    Type: E-18348-1 , 18th AIAA/CEAS Aeroacoustics Conference; Jun 04, 2012 - Jun 06, 2012; Colorado Springs, CO; United States
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  • 5
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    Numerical and Experimental Determination of the Geometric Far Field for Round Jets (2003)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: To reduce ambiguity in the reporting of far field jet noise, three round jets operating at subsonic conditions have recently been studied at the NASA Glenn Research Center. The goal of the investigation was to determine the location of the geometric far field both numerically and experimentally. The combination of the WIND Reynolds-Averaged Navier-Stokes solver and the MGBK jet noise prediction code was used for the computations, and the experimental data was collected in the Aeroacoustic Propulsion Laboratory. While noise sources are distributed throughout the jet plume, at great distances from the nozzle the noise will appear to be emanating from a point source and the assumption of linear propagation is valid. Closer to the jet, nonlinear propagation may be a problem, along with the known geometric issues. By comparing sound spectra at different distances from the jet, both from computational methods that assume linear propagation, and from experiments, the contributions of geometry and nonlinearity can be separately ascertained and the required measurement distance for valid experiments can be established. It is found that while the shortest arc considered here (approx. 8D) was already in the geometric far field for the high frequency sound (St greater than 2.0), the low frequency noise due to its extended source distribution reached the geometric far field at or about 50D. It is also found that sound spectra at far downstream angles does not strictly scale on Strouhal number, an observation that current modeling does not capture.
    Keywords: Acoustics
    Type: E-13956 , Noise-Con 2003; Jun 23, 2003 - Jun 25, 2003; Cleveland, OH; United States
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  • 6
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    Mean Flow and Noise Prediction for a Separate Flow Jet With Chevron Mixers (2004)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Experimental and numerical results are presented here for a separate flow nozzle employing chevrons arranged in an alternating pattern on the core nozzle. Comparisons of these results demonstrate that the combination of the WIND/MGBK suite of codes can predict the noise reduction trends measured between separate flow jets with and without chevrons on the core nozzle. Mean flow predictions were validated against Particle Image Velocimetry (PIV), pressure, and temperature data, and noise predictions were validated against acoustic measurements recorded in the NASA Glenn Aeroacoustic Propulsion Lab. Comparisons are also made to results from the CRAFT code. The work presented here is part of an on-going assessment of the WIND/MGBK suite for use in designing the next generation of quiet nozzles for turbofan engines.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: NASA/TM-2004-212906 , AIAA Paper 2004-0189 , E-14329 , 42nd Aerospace Sciences Meeting and Exhibit; Jan 05, 2004 - Jan 08, 2004; Reno, NV; United States
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  • 7
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    Flowfield Comparisons from Three Navier-Stokes Solvers for an Axisymmetric Separate Flow Jet (2002)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: To meet new noise reduction goals, many concepts to enhance mixing in the exhaust jets of turbofan engines are being studied. Accurate steady state flowfield predictions from state-of-the-art computational fluid dynamics (CFD) solvers are needed as input to the latest noise prediction codes. The main intent of this paper was to ascertain that similar Navier-Stokes solvers run at different sites would yield comparable results for an axisymmetric two-stream nozzle case. Predictions from the WIND and the NPARC codes are compared to previously reported experimental data and results from the CRAFT Navier-Stokes solver. Similar k-epsilon turbulence models were employed in each solver, and identical computational grids were used. Agreement between experimental data and predictions from each code was generally good for mean values. All three codes underpredict the maximum value of turbulent kinetic energy. The predicted locations of the maximum turbulent kinetic energy were farther downstream than seen in the data. A grid study was conducted using the WIND code, and comments about convergence criteria and grid requirements for CFD solutions to be used as input for noise prediction computations are given. Additionally, noise predictions from the MGBK code, using the CFD results from the CRAFT code, NPARC, and WIND as input are compared to data.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: NASA/TM-2002-211350 , AIAA Paper-2002-0672 , E-13167 , GRC-E-DAA-TN10116 , NAS 1.15:211350 , Aerospace Sciences Meeting and Exhibit; Jan 14, 2002 - Jan 17, 2002; Reno, NV; United States
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  • 8
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    NASA Clean-Sheet Fans: Design, Build Analyze, Test, and Report (2008)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A suggested topic in small fan research is presented. Presentation briefly describes the scope of an effort to design, build and test a ventilation class cooling fan. Comments are included for the following categories: information (available and needed), benefits and values, concerns, variations and alternatives, and interest.
    Keywords: Fluid Mechanics and Thermodynamics
    Type: E-16730 , Quiet, Efficient Fans for Spaceflight Workshop; Apr 02, 2008 - Apr 04, 2008; Cleveland, OH; United States
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  • 9
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    An Assessment of NASA Glenn's Aeroacoustic Experimental and Predictive Capabilities for Installed Cooling Fans (2006)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Driven by the need for low production costs, electronics cooling fans have evolved differently than the bladed components of gas turbine engines which incorporate multiple technologies to enhance performance and durability while reducing noise emissions. Drawing upon NASA Glenn's experience in the measurement and prediction of gas turbine engine aeroacoustic performance, tests have been conducted to determine if these tools and techniques can be extended for application to the aerodynamics and acoustics of electronics cooling fans. An automated fan plenum installed in NASA Glenn's Acoustical Testing Laboratory was used to map the overall aerodynamic and acoustic performance of a spaceflight qualified 80 mm diameter axial cooling fan. In order to more accurately identify noise sources, diagnose performance limiting aerodynamic deficiencies, and validate noise prediction codes, additional aerodynamic measurements were recorded for two operating points: free delivery and a mild stall condition. Non-uniformities in the fan s inlet and exhaust regions captured by Particle Image Velocimetry measurements, and rotor blade wakes characterized by hot wire anemometry measurements provide some assessment of the fan aerodynamic performance. The data can be used to identify fan installation/design changes which could enlarge the stable operating region for the fan and improve its aerodynamic performance and reduce noise emissions.
    Keywords: Acoustics
    Type: NASA/TM-2006-214448 , E-15711 , 35th International Congress and Exposition on Noise Control Engineering (INTER-NOISE 2006); Dec 03, 2006 - Dec 06, 2006; Honolulu, HI; United States
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  • 10
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    Evaluation of the Tone Fan Noise Design/Prediction System (TFaNS) at the NASA Glenn Research Center (1999)
    In:  CASI
    Details
    Publication Date: 2019-07-10
    Description: Version 1.4 of TFaNS, the Tone Fan Noise Design/Prediction System. has recently been evaluated at the NASA Glenn Research Center. Data from tests of the Allison Ultra High Bypass Fan (UHBF) were used to compare to predicted farfield directivities for the radial stator configuration. There was good agreement between measured and predicted directivities at low fan speeds when rotor effects were neglected in the TFaNS calculations. At higher fan speeds, TFaNS is shown to be useful in predicting overall trends rather than absolute sound pressure levels.
    Keywords: Acoustics
    Type: E-12011
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