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  • Organic Chemistry  (1,381)
  • AIRCRAFT PROPULSION AND POWER  (510)
  • 1975-1979  (1,891)
  • 1930-1934
  • 1977  (958)
  • 1976  (933)
Collection
Keywords
Publisher
Years
  • 1975-1979  (1,891)
  • 1930-1934
Year
  • 1
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    Summary of NASA aerodynamic and heat transfer studies in turbine vanes and blades (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: Aerodynamic effects of trailing edge geometry, hole size, angle, spacing, and shape have been studied in two- and three-dimensional cascades and in a warm turbine test series. Heat transfer studies have been carried out in various two- and three-dimensional test facilities in order to provide corresponding heat transfer data. Results are shown in terms of cooling effectiveness and aerodynamic efficiency for various coolant fractions, coolant-primary temperature ratios, and cooling configurations.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: SAE PAPER 760917
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    NASA TECHNICAL REPORTS
  • 2
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    New materials for high temperature turbines; ONERA's DS composites confronted with blade problems (1977)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: ONERA's refractory DS composites were cited as materials required for use in advanced aircraft turbines, operating at high temperatures. These materials were found to be reliable in the construction of turbine blades. Requirements for a blade material in aircraft turbines operating at higher temperatures were compared with the actual performance as found in COTAC DS composite testing. The structure and properties of the more fully developed 74 and 741 types were specified. High temperature structural stability, impact of thermal and mechanical fatigue, oxidation resistance and coating capability were thoroughly evaluated. The problem of cooling passages in DS eutectic blades is also outlined.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-75216 , High Temp. Probl. in Gas Turbine Eng.; 19-23 Sept. 1977; Ankara
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    NASA TECHNICAL REPORTS
  • 3
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    High temperature corrosion-resistant protective coatings in stationary gas turbines (1977)
    In:  CASI
    Details
    Publication Date: 2019-08-28
    Description: Methods currently used to deposit protective coatings in gas turbines are reviewed, and the structure of the respective coatings is examined. The corrosion behavior of such coatings is discussed on the basis of experimental data. General trends in the preparation of protective coatings are noted.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-75181 , Tagung in Verbundwerkstoffe; Mar 28, 1974 - Mar 29, 1974; Constance; Germany
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    NASA TECHNICAL REPORTS
  • 4
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    Aerodynamic investigation of an air-cooled axial-flow turbine. Part 2: Rotor blade tip-clearance effects on overall turbine performance and internal gas flow conditions: Experimental results and prediction methods (1977)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: Total turbine blade performance was investigated while changing the blade tip clearance in three ways. The internal flow at the moving blade outlet point was measured. Experimental results were compared with various theoretical methods. Increased blade clearance leads to decreased turbine efficiency.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-75138
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    NASA TECHNICAL REPORTS
  • 5
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    Eight-bladed propeller design could bring back turboprop airplanes (1977)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: P77-10204 , NASA-NEWS-RELEASE-77-206
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    NASA TECHNICAL REPORTS
  • 6
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    Protection of cooled blades of complex internal structure (1977)
    In:  CASI
    Details
    Publication Date: 2019-08-27
    Description: The problem of general protection of cooled blades of complex internal structure was solved by a method called SF technique which makes possible the protection of both external and internal surfaces, as well as those of the orifices of cooling air, whatever their diameter. The SF method is most often applied in the case of pack process, at controlled or high activity; it can be of use on previously uncoated parts, but also on pieces already coated by a thermochemical, chemical or PVD method. The respective thickness of external and internal coatings may be precisely predetermined, no parasitic particle being liable to remain inside the parts after application of the protecting treatment. Results obtained to date by application of this method are illustrated by the presentation and examination of a various selection of advanced turbo engines.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-75217 , AGARD-CP-229 , Conf. on High Temp. Probl. in Gas Turbine Engines; Sep 19, 1977 - Sep 23, 1977; Ankara
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  • 7
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    Effect of Flame Stabilizer Design on Performance and Exhaust Pollutants of a Two-Row Swirl-Can Combustor Operated to Near-Stoichiometric Conditions (1977)
    In:  CASI
    Details
    Publication Date: 2019-08-14
    Description: Emissions and performance characteristics were determined for two full annulus modular combustors operated to near stoichiometric fuel air ratios. The tests were conducted to obtain stoichiometric data at inlet air temperatures from 756 to 894 K and to determine the effects of a flat plate circular flame stabilizer with upstream fuel injection and a contraswirl flame stabilizer with downstream fuel injection. Levels of unburned hydrocarbons were below 0.50 gram per kilogram of fuel for both combustors and thus there was no detectable difference in the two methods of fuel injection. The contraswirl flame stabilizer did not produce the level of mixing obtained with a flat plate circular flame stabilizer. It did produce higher levels of oxides of nitrogen, which peaked at a fuel air ratio of 0.037. For the flat plate circular flame stabilizer, oxides of nitrogen emission levels were still increasing with fuel air ratio to the maximum tested value of 0.045.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-X-3495 , E-8317
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    NASA TECHNICAL REPORTS
  • 8
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    Alternatives for Jet Engine Control (1976)
    In:  CASI
    Details
    Publication Date: 2019-08-14
    Description: Approaches are developed as alternatives to current design methods which rely heavily on linear quadratic and Riccati equation methods. The main alternatives are discussed in two broad categories, local multivariable frequency domain methods and global nonlinear optimal methods.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-146531
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    NASA TECHNICAL REPORTS
  • 9
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    Reducing secondary losses by blowing cold air in a turbine (1977)
    In:  CASI
    Details
    Publication Date: 2019-08-13
    Description: Local blowing on the profile suction side of the turbine guide wheel blades can be effective in preventing the propagation of secondary flows that is, the transport of casing and hub boundary layers by pressure gradients. Some preliminary results on how the blowing should be accomplished in order to influence the secondary flows in the desired manner are given. The effectiveness of blowing is demonstrated. Blowing is also seen to be more effective than using boundary layer slots as far as diminishing losses in the rim zones is concerned.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-75185 , PAPER-76-164 , DGLR Jahrestagung; Sep 14, 1976 - Sep 16, 1976; Munich
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  • 10
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    Effects of film injection on performance of a cooled turbine (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-27
    Description: Some of the most dramatic increases in the performance of turbojet and turbofan aircraft engines have been obtained as a result of increased thermodynamic cycle temperatures made possible by the use of film cooling techniques. The realization of the potential performance gains, however, is only possible if the quantity of cooling air and the aerodynamic mixing losses resulting from the injection of coolant in the form of film on the flowpath surfaces are minimized. Such a minimization requires a more complete understanding of the relationship between cooling and aerodynamics. A review is conducted of tests which have been conducted to determine the effects of coolant injection on turbine performance. The results obtained in the tests are compared with an analytical technique developed for predicting coolant injection effects. Particular attention is given to the effects of turbine cooling on overall cycle thermodynamic efficiency, taking into account incremental changes in turbine thermodynamic efficiency for various incremental changes in coolant flow rate.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Propulsion and Energetics Panel Meeting; Sept. 19-23, 1977; Ankara; Turkey
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    NASA TECHNICAL REPORTS
  • 11
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    Quiet Clean Short-haul Experimental Engine (QCSEE) whirl test of cam/harmonic pitch change actuation system (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A variable pitch fan actuation system, which incorporates a remote nacelle mounted blade angle regulator, was tested. The regulator drives a rotating fan mounted mechanical actuator through a flexible shaft and differential gear train. The actuator incorporates a high ratio harmonic drive attached to a multitrack spherical cam which changes blade pitch through individual cam follower arms attached to each blade trunnion. Testing of the actuator on a whirl rig, is reported. Results of tests conducted to verify that the unit satisfied the design requirements and was structurally adequate for use in an engine test are presented.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-135140 , HSER-7002
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  • 12
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    State-of-the-art of turbofan engine noise control (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A description is presented of some of the recent advances in the technology of turbofan engine noise reduction, taking into account turbomachinery noise sources, new fans for low noise, fan and core noise suppression, and a new program for improving static noise testing of fans and engines. The problem of jet noise has been substantially reduced in connection with the lower jet velocities employed in the case of the high bypass turbofan engines. The dominant noise sources are now related to the turbomachinery with the fan stage, the compressor, and the turbine. Since the fan stage is the primary source of turbomachinery noise, it has been considered in a major part of the investigations designed to reduce turbofan engine noise.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: In: NOISE-CON 77; National Conference on Noise Control Engineering; Oct 17, 1977 - Oct 19, 1977; Hampton, VA
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    NASA TECHNICAL REPORTS
  • 13
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    Effect of airstream velocity on mean drop diameters of water sprays produced by pressure and air atomizing nozzles (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A scanning radiometer was used to determine the effect of airstream velocity on the mean drop diameter of water sprays produced by pressure atomizing and air atomizing fuel nozzles used in previous combustion studies. Increasing airstream velocity from 23 to 53.4 meters per second reduced the Sauter mean diameter by approximately 50 percent with both types of fuel nozzles. The use of a sonic cup attached to the tip of an air assist nozzle reduced the Sauter mean diameter by approximately 40 percent. Test conditions included airstream velocities of 23 to 53.4 meters per second at 293 K and atmospheric pressure.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Winter Annual Meeting; Nov 27, 1977 - Dec 02, 1977; Atlanta, GA
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    NASA TECHNICAL REPORTS
  • 14
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    General aviation energy-conservation research programs at NASA-Lewis Research Center (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A review is presented of non-turbine general aviation engine programs underway at the NASA-Lewis Research Center in Cleveland, Ohio. The program encompasses conventional, lightweight diesel and rotary engines. Its three major thrusts are, in order of priority: (1) reduced SFCs; (2) improved fuels tolerance; and (3) reducing emissions. Current and planned future programs in such areas as lean operation, improved fuel management, advanced cooling techniques and advanced engine concepts, are described. These are expected to lay the technology base, by the mid to latter 1980s, for engines whose total fuel costs are as much as 30% lower than today's conventional engines.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Conference on Energy Conservation in General Aviation; Oct 10, 1977 - Oct 11, 1977; Kalamazoo, MI
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  • 15
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    Output feedback regulator design for jet engine control systems (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A multivariable control design procedure based on the output feedback regulator formulation is described and applied to an F100 turbofan engine model. Full order model dynamics, are incorporated in the example design. The effect of actuator dynamics on closed loop performance is investigated. Also, the importance of turbine inlet temperature as an element of the dynamic feedback is studied. Step responses are given to indicate the improvement in system performance with this control. Calculation times for all experiments are given in CPU seconds for comparison purposes.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: National Electronics Conference; Oct 13, 1977 - Oct 14, 1977; Chicago, IL
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    NASA TECHNICAL REPORTS
  • 16
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    Effectiveness of an inlet flow turbulence control device to simulate flight fan noise in an anechoic chamber (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A hemispherical inlet flow control device was tested on a 50.8 cm. (20-inch) diameter fan stage in the NASA-Lewis Anechoic Chamber. The control device used honeycomb and wire mesh to reduce turbulence intensities entering the fan. Far field acoustic power level results showed about a 5 dB reduction in blade passing tone and about 10 dB reduction in multiple pure tone sound power at 90% design fan speed with the inlet device in place. Hot film cross probes were inserted in the inlet to obtain data for two components of the turbulence at 65 and 90% design fan speed. Without the flow control device the axial intensities were below 1.0%, while the circumferential intensities were almost twice this value. The inflow control device significantly reduced the circumferential turbulence intensities and also reduced the axial length scale.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Meeting of the Acoustical Society of America; Dec 13, 1977 - Dec 16, 1977; Miami Beach, FL
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    NASA TECHNICAL REPORTS
  • 17
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    Combustor fluctuating pressure measurements in-engine and in a component test facility - A preliminary comparison (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Combustor internal fluctuating pressure and far-field noise generated in a YF-102 turbofan engine are investigated; combustor internal measurements are also made in a duct-component test facility operating over a range of conditions encompassing those characteristic of the aircraft engine. Although directly measured spectra for the engine and the duct-component test facility show discrepancies, the results of coherence function, transfer function and phase relationship comparisons suggest that the internal dynamics of the combustor as an acoustic source may be preserved in a component test facility.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Meeting of the Acoustical Society of America; Dec 13, 1977 - Dec 16, 1977; Miami Beach, FL
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    NASA TECHNICAL REPORTS
  • 18
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    An empirical model for inverted-velocity-profile jet noise prediction (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: It is known that the noise generated by inverted-velocity-profile coaxial (without center plug) and coannular (with center plug) nozzles should be modeled as the combined contributions of various source regions and noise generation mechanisms. In this paper, an empirical noise-prediction model is described which considers the noise generated by two jet-mixing regions and two potential regions of shock/turbulence interaction. Results calculated from the empirical model are compared with model-scale experimental data for static and simulated flight conditions. These comparisons are made for cases where both streams are subsonic, where the outer stream is supersonic with the inner stream subsonic, and where both streams are supersonic. The cases considered cover a range of inner-to-outer-stream area ratios and include both coaxial and coannular nozzles. It is shown that the model gives reasonable predictions of absolute noise spectra and even better predictions of incremental changes.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Meeting of the Acoustical Society of America; Dec 13, 1977 - Dec 16, 1977; Miami Beach, FL
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    NASA TECHNICAL REPORTS
  • 19
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    Noise of deflectors used for flow attachment with STOL-OTW configurations (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Future STOL aircraft may utilize engine-over-the-wing (OTW) installations in which the exhaust nozzles are located above and separated from the upper surface of the wing. An external jet-flow deflector can be used with such installations to provide flow attachment to the wing/flap surfaces for lift augmentation. In the present work, the deflector noise in the flyover plane measured with several model-scale nozzle/deflector/wing configurations is examined. The deflector-associated noise is correlated in terms of velocity and geometry parameters. The data also indicate that the effective overall sound pressure level of the deflector-associated noise peaks in the forward quadrant near 40 deg from the inlet axis.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Meeting of the Acoustical Society of America; Dec 13, 1977 - Dec 16, 1977; Miami Beach, FL
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    NASA TECHNICAL REPORTS
  • 20
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    Failure detection and correction for turbofan engines (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: In this paper, a failure detection and correction strategy for turbofan engines is discussed. This strategy allows continuing control of the engines in the event of a sensor failure. An extended Kalman filter is used to provide the best estimate of the state of the engine based on currently available sensor outputs. Should a sensor failure occur the control is based on the best estimate rather than the sensor output. The extended Kalman filter consists of essentially two parts, a nonlinear model of the engine and up-date logic which causes the model to track the actual engine. Details on the model and up-date logic are presented. To allow implementation, approximations are made to the feedback gain matrix which result in a single feedback matrix which is suitable for use over the entire flight envelope. The effect of these approximations on stability and response is discussed. Results from a detailed nonlinear simulation indicate that good control can be maintained even under multiple failures.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Joint Automatic Control Conference; Jun 22, 1977 - Jun 24, 1977; San Francisco, CA; US
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    NASA TECHNICAL REPORTS
  • 21
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    Design of turbofan engine controls using output feedback regulator theory (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A multivariable control design procedure based on output feedback regulator (OFR) theory is applied to the F100 turbofan engine. Results for the OFR design are compared to a design based on linear quadratic regulator (LQR) theory. This LQR design was obtained as part of the F100 Multivariable Control Synthesis (MVCS) program. In the MVCS program the LQR feedback control was designed in a reduced dimension state space and then applied to the original system. However, the OFR feedback control is designed in the full order state space and thus eliminates any need for model reduction techniques. Using the performance measure and control structure of the MVCS program LQR design, an equivalent OFR feedback control is obtained. The flexibility of the OFR as a control design procedure is demonstrated and differing feedback control structures are evaluated.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Joint Automatic Control Conference; Jun 22, 1977 - Jun 24, 1977; San Francisco, CA
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    NASA TECHNICAL REPORTS
  • 22
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    Optimal controls for an advanced turbofan engine (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Linear optimal control theory is applied to the control synthesis of a high bypass ratio, variable pitch, turbofan engine. The basic control philosophy is to use only a low order dynamic model of the plant coupled with the concept of integral-output states so as to maintain control simplicity yet guarantee integral control of thrust, turbine temperature and other important engine outputs. Linear simulation results indicate that the control system developed provides rapid control of small thrust perturbations and quickly eliminates the effect of unmodelled thrust and temperature disturbances. Large thrust accelerations are obtained in about one half second while the control maintains negligible overshoot in temperature and stall margins.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Joint Automatic Control Conference; Jun 22, 1977 - Jun 24, 1977; San Francisco, CA
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  • 23
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    The application of the Routh approximation method to turbofan engine models (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The Routh approximation technique is applied in the frequency domain to a 16th order state variable turbofan engine model. The results obtained motivate the extension of the frequency domain formulation of the Routh method to the time domain to handle the state variable formulation directly. The time domain formulation is derived and a new characterization, which specifies all possible Routh similarity transformations, is given. This characterization is computed by the solution of two eigenvalue-eigenvector problems. The application of the time domain Routh technique to the state variable engine model is described and some results are given. Additional computational problems are discussed including an optimization procedure which can improve the approximation accuracy by taking advantage of the transformation characterization.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Joint Automatic Control Conference; Jun 22, 1977 - Jun 24, 1977; San Francisco, CA
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  • 24
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    Minimum-time acceleration of aircraft turbofan engines (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Minimum-time accelerations of the F100 turbofan engine are presented. A piecewise-linear engine model, having three state variables and four control variables, is used to obtain the minimum-time solutions. The linear model which applies at a given time in the trajectory is determined by calculating a normalized 'distance' from the current state to the equilibrium state associated with each linear model. The linear model associated with the closest equilibrium point is then used. The control histories for the minimum-time solutions are used as input to a nonlinear simulation of the F100 engine to verify the accuracy of the piecewise-linear solutions.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Joint Automatic Control Conference; Jun 22, 1977 - Jun 24, 1977; San Francisco, CA
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    NASA TECHNICAL REPORTS
  • 25
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    Frequency domain compensation of a DYNGEN turbofan engine model (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Following Rosenbrock's ideas regarding the advantages of dominance in linear multivariable control systems, a new graphical technique is used for the design of compensators that achieve dominance. The technique is illustrated with an application to the problem of designing compensators for a linear turbofan-engine model. The resulting design is put into perspective by examining it in the light of two other multivariable frequency-domain methods. One, MacFarlane's method of characteristic loci, is used to realize a final design for stability and low interaction. The other is a direct technique based upon the algebraic expansion of the determinant of the return difference in terms of it's elements. Results from simulations carried out on the NASA DYNGEN software are included.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Joint Automatic Control Conference; Jun 22, 1977 - Jun 24, 1977; San Francisco, CA
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    NASA TECHNICAL REPORTS
  • 26
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    Preliminary QCSEE program - Test results (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Preliminary results are reported for the Quiet Clean Short-haul Experimental Engine (QCSEE) program initiated by NASA in 1974 to develop propulsion system technology suitable for powered-lift short-range commercial aircraft. The QCSEE technology also has applications to the proposed U.S. Navy V/STOL aircraft. Emphasis in the QCSEE program is placed on developing engines with low noise characteristics; in addition, the power plants are required to conform to EPA 1979 pollutant emissions standards. Thrust performance, fan design, and thrust/weight ratio are discussed for both the over-the-wing and under-the-wing engine configurations under study.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: SAE PAPER 771008 , Aerospace Meeting; Nov 14, 1977 - Nov 17, 1977; Los Angeles, CA
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    NASA TECHNICAL REPORTS
  • 27
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    High temperature environmental effects on metals (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The gas turbine engine was used as an example to predict high temperature environmental attack on metals. Environmental attack in a gas turbine engine derives from high temperature, combustion products of the air and fuel burned, and impurities. Of all the modes of attack associated with impurity effects, hot corrosion was the most complicated mechanistically. Solutions to the hot corrosion problem were sought semi-empirically in: (1) improved alloys or ceramics; (2) protective surface coating; (3) use of additives to the engine environment; and (4) air/fuel cleanup to eliminate harmful impurities.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-73878 , Sagamore Army Materials Res., Conf. Risk and Failure Analysis for Reliability; Aug 22, 1977 - Aug 26, 1977; Bolton Landing, NY; United States
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    NASA TECHNICAL REPORTS
  • 28
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    Preliminary QCSEE program test results (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The QCSEE (Quiet, Clean, Short-Haul Experimental Engine) program has entered the engine test phase. Overall design and advanced technology incorporated into the two engines in the program were described. In addition, preliminary engine test results are presented and compared to the technical requirements the engines were designed to meet.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-73732 , 1977 Aerospace Meeting; Nov 14, 1977 - Nov 17, 1977; Los Angeles
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    NASA TECHNICAL REPORTS
  • 29
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    General aviation energy-conservation research programs at NASA-Lewis Research Center (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The major thrust of NASA's nonturbine general aviation engine programs is directed toward (1) reduced specific fuel consumption, (2) improved fuel tolerance; and (3) emission reduction. Current and planned future programs in such areas as lean operation, improved fuel management, advanced cooling techniques and advanced engine concepts, are described. These are expected to lay the technology base, by the mid to latter 1980's, for engines whose total fuel costs are as much as 30% lower than today's conventional engines.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-73884 , Conf. on Energy Conserv. in Gen. Aviation; Oct 10, 1977 - Oct 11, 1977; Kalamazoo, MI; United States
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    NASA TECHNICAL REPORTS
  • 30
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    Flight-Effects on Predicted Fan Fly-By Noise (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The impact on PNLT (Perceived Noise Level, Tone corrected) and Fly-by EPNL (Effective Perceived Noise Level) when forward motion reduces the noise generated by the bypass fan of an aircraft engine was studied. Calculated noise spectra for a typical subsonic tip speed fan designed for blade passage frequency (BPF) tone cutoff were translated in frequency by systematically varying the BPF from 0.5 to 8 kHz. Two cases of predicted flight-effects on fan source noises were considered: reduced BPF tone level of 8 db and reduced broadband noise level of about 2 db in addition to reduced tone level. The maximum reduction in PNLT of the noise as emitted from the fan occurred when the BPF was at 4 kHz where the reductions were 7.4 and 10.0 db. The maximum reduction in EPNL of the noise as received during a 500-foot altitude fly-by occurred when the BPF was at 2.5 kHz where the reductions were 5.0 and 7.8 db.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-73798 , Meeting of the Acoustical Soc. of Am.; Dec 13, 1977 - Dec 16, 1977; Miami, FL; United States
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  • 31
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    Aircraft Engine Emissions (1977)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: A conference on a aircraft engine emissions was held to present the results of recent and current work. Such diverse areas as components, controls, energy efficient engine designs, and noise and pollution reduction are discussed.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CP-2021 , E-9262 , May 18, 1977 - May 19, 1977; Cleveland
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  • 32
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    Evaluation of an F100 multivariable control using a real-time engine simulation (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A multivariable control design for the F100 turbofan engine was evaluated, as part of the F100 multivariable control synthesis (MVCS) program. The evaluation utilized a real-time, hybrid computer simulation of the engine and a digital computer implementation of the control. Significant results of the evaluation are presented and recommendations concerning future engine testing of the control are made.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-X-73648 , E-9155 , Propulsion Conf.; Jul 11, 1977 - Jul 13, 1977; Orlando, FL; United States
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  • 33
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    An Assessment of Technology for Turbojet Engine Rotor Failures (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Design considerations, objectives, and approaches used in containing rotor burst debris are discussed. Methods are given for determining the fracture resistance of various materials used in providing lightweight shielding from fragment impact.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CP-2017 , E-8305 , Mar 29, 1977 - Mar 31, 1977; Cambridge, MA; United States
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  • 34
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    The jet engine design that can drastically reduce oxides of nitrogen (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The NOx pollution problem of hydrogen fueled turbojets and supersonic combustion ramjets (scramjets) was investigated to determine means of substantially alleviating the problem. Since the NOx reaction rates are much slower than the energy producing reactions, the NOx production depends mainly on the maximum local temperatures in the combustor and the NOx concentration is far from equilibrium at the end of a typical combustor (L approximately 1 ft). In diffusion flames, as used in present turbojets and scramjets combustor designs, the maximum local temperature occurs at the flame and is equal to the stoichiometric value. Whereas, in the heat conduction flames, wherein the flame propagates due to a heat conduction process away from the flame to the cooler oncoming premixed unburnt gases, the maximum temperature is lower than in the diffusion flame. Hence the corresponding pollution index is also lower.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 74-160 , Selected Papers on Advanced Design of Air Vehicles; p 79-88|AIAA Aerospace Sci. Meeting; Jan 30, 1974 - Feb 01, 1974; Washington, DC; United States
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  • 35
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    Acoustic performance of inlet multiple-pure-tone suppressors installed on NASA Quiet Engine 'C' (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The purpose of the experimental program reported herein was to define the length of multiple pure tone (MPT) treatment required to reasonably suppress the MPT's produced by a supersonic tip speed fan and also determine what other suppression, broadband, and blade passing frequency (BPF), might be accomplished. The experimental results are presented in terms of both far-field and duct acoustic data. Front quadrant sound power level reduction in the far field is shown to agree with duct measurements over the range of treatment lengths. Detailed one-third octave and narrow band spectra at the maximum forward noise angle are presented. Some detailed analyses of one-third-octave band amplitudes are shown as a function of far-field angle. An approximate spinning mode duct propagation analysis is then introduced which predicts the acoustic suppression by the treatment on the multiple pure tones.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 77-1333 , Aeroacoustics Conference; Oct 03, 1977 - Oct 05, 1977; Atlanta, GA
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  • 36
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    Evaluation of a staged fuel combustor for turboprop engines (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Proposed EPA emission regulations require emission reduction by 1979 for various gas turbine engine classes. Extensive combustion technology advancements are required to meet the proposed regulations. The T56 turboprop engine requires CO, UHC, and smoke reduction. A staged fuel combustor design was tested on a combustion rig to evaluate emission reduction potential in turboprop engines from fuel zoning. The can-type combustor has separately fueled-pilot and main combustion zones in series. The main zone fueling system was arranged for potential incorporation into the T56 with minor or no modifications to the basic engine. Three combustor variable geometry systems were incorporated to evaluate various airflow distributions. Emission results with fixed geometry operation met all proposed EPA regulations over the EPA LTO cycle. CO reduction was 82 percent, UHC reduction was 96 percent, and smoke reduction was 84 percent. NOx increased 14 percent over the LTO cycle. At high power, NOx reduction was 40 to 55 percent. This NOx reduction has potential application to stationary gas turbine powerplants which have different EPA regulations.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: ASME PAPER 76-WA/GT-5 , Winter Annual Meeting on Pilot project in technology transfer to a developing nation; Dec 05, 1976 - Dec 10, 1976; New York, NY
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  • 37
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    Coherence between internal and external noise generated by gas turbine combustors (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Experiments and analysis on a gas turbine combustor unit are reported with a view in mind to separate propagated acoustic power from non-propagating 'pseudo-sound'. Analytically, it is suggested that a transition frequency will exist below which the interior pressure fluctuations are non-propagating, whereas above this frequency, of the order of 100 Hz, the noise is dominated by propagating acoustic waves. Coherence measurements are reported which show this concept to be borne out experimentally. Coherence between interior and exterior microphones is measured over a wide range of experimental conditions for a gas turbine combustor exhausting directly to the atmosphere. The purpose is to show that below a certain frequency, measurements of interior noise are not indicative of combustion noise ultimately propagating from an engine.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 77-20 , Aerospace Sciences Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles, CA
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  • 38
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    Supersonic combustion ramjet /scramjet/ engine development in the United States (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This survey of supersonic combustion ramjet (scramjet) engine development in the United States covers development of this unique engine cycle from its inception in the early 1960's through the various programs currently being pursued and, in some instances, describing the future direction of the programs. These include developmental efforts supported by the U.S. Navy, National Aeronautics and Space Administration, and U.S. Air Force. Results of inlet, combustor, and nozzle component tests, free-jet engine tests, analytical techniques developed to analyze and predict component and engine performance, and flight-weight hardware development are presented. These results show that efficient scramjet propulsion is attainable in a variety of flight configurations with a variety of fuels. Since the scramjet is the most efficient engine cycle for hypersonic flight within the atmosphere, it should be given serious consideration in future propulsion schemes
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: International Symposium on Air Breathing Engines; Mar 07, 1976 - Mar 12, 1976; Munich; Germany
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  • 39
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    A preliminary in-duct measurement of spinning modes in the inlet of a rotating vehicle (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Suppression of noise radiated from a jet engine duct is an important environmental problem. Results are presented for a study aimed at developing and evaluating an experimental method for measuring the complex acoustic pressure field at a plane in the inlet of a fan duct. The theory of modal propagation is outlined and related to the theory of measuring spinning modes in the duct. A spinning mode measurement apparatus is described, and preliminary test results of the modal measurement for several operating speeds are presented. The measurement of spinning modes is successfully carried out in the inlet of a rotating vehicle under conditions representative of an actual jet engine. Data repeatability and problems encountered in the measurement are examined. In particular, it is important to calibrate the probe systems for phase and level. Recommendations for future improvements in the method are made.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Annual Meeting of Acoustical Society of America; Apr 05, 1976 - Apr 09, 1976; Washington, DC
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  • 40
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    State-of-the-art of turbofan engine noise control (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The technology of turbofan engine noise reduction is surveyed. Specific topics discussed include: (1) new fans for low noise; (2) fan and core noise suppression; (3) turbomachinery noise sources; and (4) a new program for improving static noise testing of fans and engines.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-73734 , E-9254 , NOISE-CON 77; Oct 17, 1977 - Oct 19, 1977; Hampton, VA; United States
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  • 41
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    Measurement of far field combustion noise from a turbofan engine using coherence functions (1977)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Coherence measurements between fluctuating pressure in the combustor of a YF-102 turbofan engine and far-field acoustic pressure were made. The results indicated that a coherent relationship between the combustor pressure and far-field existed only at frequencies below 250 Hz, with the peak occurring near 125 Hz. The coherence functions and the far-field spectra were used to compute the combustor-associated far-field noise in terms of spectra, directivity, and acoustic power, over a range of engine operating conditions. The acoustic results so measured were compared with results obtained by conventional methods, as well as with various semiempirical predictions schemes. Examination of the directivity patterns indicated a peak in the combustion noise near 120 deg (relative to the inlet axis).
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-73748 , E-9320 , AIAA PAPER 77-1277 , Aeroacoustics Conf.; Oct 03, 1977 - Oct 05, 1977; Atlanta
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  • 42
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    Steady-state unbalance response of a three-disk flexible rotor on flexible, damped supports (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Experimental data are presented for the unbalance response of a flexible, ball bearing supported rotor to speeds above the third lateral bending critical. Values of squeeze film damping coefficients obtained from measured data are compared to theoretical values obtained from short bearing approximation over a frequency range from 5000 to 31 000 cycles/min. Experimental response for an undamped rotor is compared to that of one having oil squeeze film dampers at the bearings. Unbalance applied varied from 0.62 to 15.1 gm-cm.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-X-73666 , E-9091-1 , Vibrations Conf.; Sep 26, 1977 - Sep 29, 1977; Chicago
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  • 43
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    Multimodal far-field acoustic radiation pattern: An approximate equation (1977)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The far-field sound radiation theory for a circular duct was studied for both single mode and multimodal inputs. The investigation was intended to develop a method to determine the acoustic power produced by turbofans as a function of mode cut-off ratio. With reasonable simplifying assumptions the single mode radiation pattern was shown to be reducible to a function of mode cut-off ratio only. With modal cut-off ratio as the dominant variable, multimodal radiation patterns can be reduced to a simple explicit expression. This approximate expression provides excellent agreement with an exact calculation of the sound radiation pattern using equal acoustic power per mode.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-73721 , Aeroacoustics Conf.; Oct 03, 1977 - Oct 05, 1977; Atlanta
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  • 44
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    Output feedback regulator design for jet engine control systems (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A multivariable control design procedure based on the output feedback regulator formulation is described and applied to turbofan engine model. Full order model dynamics, were incorporated in the example design. The effect of actuator dynamics on closed loop performance was investigaged. Also, the importance of turbine inlet temperature as an element of the dynamic feedback was studied. Step responses were given to indicate the improvement in system performance with this control. Calculation times for all experiments are given in CPU seconds for comparison purposes.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-73776 , Intern. Forum on Alternatives for Linear Multivariable Control; Oct 13, 1977 - Oct 14, 1977; Chicago
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  • 45
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    Progress in advanced high temperature turbine materials, coatings, and technology (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Material categories as well as coatings and recent turbine cooling developments are reviewed. Current state of the art is identified, and as assessment, when appropriate, of progress, problems, and future directions is provided.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-X-73628 , Panel on Propulsion and Energetics; Sep 19, 1977 - Sep 23, 1977; Ankara
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  • 46
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    Advanced turboprop technology development (1977)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The efficiency of high-speed turboprop propulsion systems is considered with emphasis on fuel savings. Specific topics discussed include: (1) high efficiency and low noise of propeller design; (2) fuselage noise attenuation; (3) propeller and gear box maintenance; and (4) engine-airframe integration.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-73729 , E-9290 , Aircraft Systems and Technol. Meeting; Aug 22, 1977 - Aug 24, 1977; Seattle
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  • 47
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    Design of turbofan engine controls using output feedback regulator theory (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A multivariable control design procedure based on output feedback regulator (OFR) theory is applied to the F100 turbofan engine. Results for the OFR design are compared to a design based on linear quadratic regulator (LQR) theory. The OFR feedback control is designed in the full order state space and thus eliminates any need for model reduction techniques. Using the performance measure and control structure of the LQR design, an equivalent OFR feedback control is obtained. The flexibility of the OFR as a control design procedure is demonstrated, and differing feedback control structures are evaluated.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-X-73622 , E-9113 , Joint Automatic Control Conf.; Jun 22, 1977 - Jun 24, 1977; San Francisco
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  • 48
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    The application of the Routh approximation method to turbofan engine models (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The Routh approximation technique is applied in the frequency domain to a 16th order state variable turbofan engine model. The results obtained motivate the extension of the frequency domain formulation of the Routh method to the time domain to handle the state variable formulation directly. The time domain formulation is derived, and a characterization, which specifies all possible Routh similarity transformations, is given. The characterization is computed by the solution of two eigenvalue eigenvector problems. The application of the time domain Routh technique to the state variable engine model is described, and some results are given.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-X-73623 , E-9114 , Joint Autom. Control Conf.; Jun 22, 1977 - Jun 24, 1977; San Francisco
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  • 49
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    NASA Quiet Clean General Aviation Turbofan (QCGAT) program status (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The suitability of large engine technology to reduce noise, emissions, and fuel consumption of small turbine engines and develop new technology where required is determined. The design, fabrication, assembly, test, and delivery of the experimental engines to NASA are discussed.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-X-73564 , E-9008 , Intern. Gas Turbine Conf.; Mar 27, 1977 - Mar 31, 1977; Philadelphia, PA; United States
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  • 50
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    Effect of endwall cooling on secondary flows in turbine stator vanes (1977)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The effect of endwall cooling on the secondary flow behavior and the aerodynamic performance of a core turbine stator vane was determined. The investigation was conducted in a cold-air, full-annular cascade, where three-dimensional effects were obtained. Two endwall cooling configurations were tested. In the first configuration, the cooling holes were oriented so that the coolant was injected in line with the inviscid streamline direction. In the second configuration, the coolant was injected at an angle of 15 deg to the inviscid streamline direction and oriented towards the vane pressure stator. In both cases the stator vanes were solid and uncooled so that the effect of endwall cooling was obtained directly. Total-pressure surveys were taken downstream of the stator vanes over a range of cooling flows at the design, mean-radius, critical velocity ratio of 0.778. Changes in the total-pressure contours downstream of the vanes were used to obtain the effect of endwall cooling on the secondary flows in the stator.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-X-73568 , AGARD 49th Propulsion and Energetics Panel Conf.; Mar 28, 1977 - Apr 04, 1977; The Hague
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  • 51
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    Aircraft Piston Engine Exhaust Emission Symposium (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A 2-day symposium on the reduction of exhaust emissions from aircraft piston engines was held on September 14 and 15, 1976, at the Lewis Research Center in Cleveland, Ohio. Papers were presented by both government organizations and the general aviation industry on the status of government contracts, emission measurement problems, data reduction procedures, flight testing, and emission reduction techniques.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CP-2005 , E-9010 , Sep 14, 1976 - Sep 15, 1976; Cleveland
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  • 52
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    Core noise measurements on a YF-102 turbofan engine (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Core noise from a YF-102 high bypass ratio turbofan engine was investigated through the use of simultaneous measurements of internal fluctuating pressures and far field noise. Acoustic waveguide probes, located in the engine at the compressor exit, in the combustor, at the turbine exit, and in the core nozzle, were employed to measure internal fluctuating pressures. Spectra showed that the internal signals were free of tones, except at high frequency where machinery noise was present. Data obtained over a wide range of engine conditions suggest that below 60% of maximum fan speed the low frequency core noise contributes significantly to the far field noise.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-X-73587 , E-9050 , Aerospace Sci. Meeting; Jan 24, 1977 - Jan 26, 1977; Los Angeles
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  • 53
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    Flight effects on exhaust noise for turbojet and turbofan engines: Comparison of experimental data with prediction (1976)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: It was demonstrated that static and in flight jet engine exhaust noise can be predicted with reasonable accuracy when the multiple source nature of the problem is taken into account. Jet mixing noise was predicted from the interim prediction method. Provisional methods of estimating internally generated noise and shock noise flight effects were used, based partly on existing prediction methods and partly on recent reported engine data.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-X-73552 , E-8990 , Meeting of Acoustical Soc. of Am.; Nov 16, 1976 - Nov 19, 1976; San Diego, CA; United States
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  • 54
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    Advanced radial inflow turbine rotor program: Design and dynamic testing (1976)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: The advancement of small, cooled, radial inflow turbine technology in the area of operation at higher turbine inlet temperature is discussed. The first step was accomplished by designing, fabricating, and subjecting to limited mechanical testing an advanced gas generator rotating assembly comprising a radial inflow turbine and two-stage centrifugal compressor. The radial inflow turbine and second-stage compressor were designed as an integrally machined monorotor with turbine cooling taking place basically by conduction to the compressor. Design turbine inlet rotor gas temperature, rotational speed, and overall gas generator compressor pressure ratio were 1422 K (2560 R), 71,222 rpm, and 10/1 respectively. Mechanical testing on a fabricated rotating assembly and bearing system covered 1,000 cold start/stop cycles and three spins to 120 percent design speed (85,466 rpm).
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-135080 , SOLAR-ER-2519
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  • 55
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    Macroscopic study of time unsteady noise of an aircraft engine during static tests (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Static tests of aircraft engines can exhibit greater than 10 db random unsteadiness of tone noise levels because flow disturbances that prevail near test site facilities are ingested. Presumably such changes are related to installation and test site features. Some properties of unsteady noise observed during tests of a Lycoming YF-102 turbofan engine are presented. Time and spatial variations in tone noise obtained from closely spaced far field and inlet duct microphones are displayed. Long to extremely short intermittent tone bursts are observed. Unsteadiness of the tone, its harmonics, and the broadband noise show little similarity. In the far field, identity of tone bursts is retained over a directivity angle of less than 10 deg. In the inlet duct, tone bursts appear to propagate axially but exhibit little circumferential similarity. They show only slight relationship to tone bursts observed in the far field. The results imply an intermittent generation of random mixtures of propagating duct modes.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-X-73556 , E-8995 , Meeting of the Acoustical Soc. of Am.; Nov 16, 1976 - Nov 19, 1976; San Diego, CA; United States
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  • 56
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    Effects of forward velocity on noise for a J85 turbojet engine with multitube suppressor from wind tunnel and flight tests (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Flight and wind tunnel noise tests were conducted using a J85 turbojet engine as a part of comprehensive programs to obtain an understanding of forward velocity effects on jet exhaust noise. Nozzle configurations of primary interest were a 104-tube suppressor with and without an acoustically-treated shroud. The installed configuration of the engine was as similar as possible in the flight and wind tunnel tests. Exact simultaneous matching of engine speed, exhaust velocity, and exhaust temperature was not possible, and the wind tunnel maximum Mach number was approximately 0.27, while the flight Mach number was approximately 0.37. The nominal jet velocity range was 450 to 640 m/sec. For both experiments, background noise limited the jet velocity range for which significant data could be obtained. In the present tests the observed directivity and forward velocity effects for the suppressor are more similar to predicted trends for internally-generated noise than unsuppressed jet noise.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-X-73542 , E-8974 , Meeting of the Acoustical Soc. of Am.; Nov 16, 1976 - Nov 19, 1976; San Diego, CA; United States
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  • 57
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    Simulation of Flight-Type Engine Fan Noise in the NASA-Lewis 9X15 Anechoic Wind Tunnel (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Flight type noise as contrasted to the usual ground static test noise exhibits substantial reductions in the time unsteadiness of tone noise, and in the mean level of tones calculated to be nonpropagating or cut-off. A model fan designed with cuttoff of the fundamental tone was acoustically tested in the anechoic wind tunnel under both static and tunnel flow conditions. The properties that characterize flight type noise were progressively simulated with increasing tunnel flow. The distinctly lobed directivity pattern of propagating rotor/stator interaction modes was also observed. Excess noise attributed to the ingestion of the flow disturbances that prevail near most static test facilities is substantially reduced with tunnel flow.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-X-73540 , E-8972 , Meeting of the Acoust. Soc. of Am.; Nov 16, 1976 - Nov 19, 1976; San Diego, CA; United States
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  • 58
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    Advanced combustion techniques for controlling NO sub x emissions of high altitude cruise aircraft (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An array of experiments designed to explore the potential of advanced combustion techniques for controlling the emissions of aircraft into the upper atmosphere was discussed. Of particular concern are the oxides of nitrogen (NOx) emissions into the stratosphere. The experiments utilize a wide variety of approaches varying from advanced combustor concepts to fundamental flame tube experiments. Results are presented which indicate that substantial reductions in cruise NOx emissions should be achievable in future aircraft engines. A major NASA program is described which focuses the many fundamental experiments into a planned evolution and demonstration of the prevaporized-premixed combustion technique in a full-scale engine.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-X-73473 , E-8858 , Intern. Astronaut. Congr.; Oct 10, 1976 - Oct 16, 1976; Anaheim, CA; United States
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    Toward more environmentally resistant gas turbines: Progress in NASA-Lewis programs (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: A wide range of programs are being conducted for improving the environmental resistance to oxidation and hot corrosion of gas turbine and power system materials. They range from fundamental efforts to delineate attack mechanisms, allow attack modeling and permit life prediction, to more applied efforts to develop potentially more resistant alloys and coatings. Oxidation life prediction efforts have resulted in a computer program which provides an initial method for predicting long time metal loss using short time oxidation data by means of a paralinear attack model. Efforts in alloy development have centered on oxide-dispersion strengthened alloys based on the Ni-Cr-Al system. Compositions have been identified which are compromises between oxidation and thermal fatigue resistance. Fundamental studies of hot corrosion mechanisms include thermodynamic studies of sodium sulfate formation during turbine combustion. Information concerning species formed during the vaporization of Na2SO4 has been developed using high temperature mass spectrometry.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-X-73499 , Conf. on Gas Turbine Mater. in a Marine Environ.; Sep 20, 1976 - Sep 23, 1976; Bath
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  • 60
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    Advanced combustion techniques for controlling NO/x/ emissions of high altitude cruise aircraft (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: An array of experiments have been and continue to be sponsored and conducted by NASA to explore the potential of advanced combustion techniques for controlling the emissions of aircraft into the upper atmosphere. Of particular concern are the oxides of nitrogen (NO/x/) emissions into the stratosphere. The experiments utilize a wide variety of approaches varying from advanced combustor concepts to fundamental flame tube experiments. Results are presented which indicate that substantial reductions in cruise NO/x/ emissions should be achievable in future aircraft engines. A major NASA program is described which focuses the many fundamental experiments into a planned evolution and demonstration of the prevaporized-premixed combustion technique in a full-scale engine.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: IAF PAPER 76-108 , International Astronautical Congress; Oct 10, 1976 - Oct 16, 1976; Anaheim, CA
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  • 61
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    A report on the aerodynamic design and wind tunnel test of a Prop-Fan model (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Recent transport aircraft system studies have shown that the Prop-Fan propulsion system offers the potential for significant fuel savings over high bypass turbofans employing the same core engine technology for each. This important finding has encouraged more detailed study of the Prop-Fan aerodynamics and has led to NASA sponsorship of a wind tunnel research program to explore the projected high efficiency levels of advanced propeller configurations for 0.80 Mach number, high-altitude cruise operation. The aerodynamic design philosophy for the Prop-Fan model is discussed. The geometric characteristics and predicted performance of the wind tunnel model are presented. Finally, the preliminary test results are reviewed and compared to the performance goals originally projected.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-667 , Propulsion Conference; Jul 26, 1976 - Jul 29, 1976; Palo Alto, CA
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  • 62
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    Flight experience with a digital integrated propulsion control system on an F-111E airplane (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A digital integrated propulsion control system (IPCS) installed in the left side of an F-111 E aircraft was tested in flight. The F-111 aircraft was selected for the IPCS program because it incorporated a variable geometry inlet and an afterburning turbofan engine and had two engines, one of which could remain in the normal configuration to ensure flight safety. Flight data were compared with results of tests run in an altitude test chamber. The digital system was found to be capable of duplicating the standard engine and inlet control systems. Instabilities such as inlet buzz and afterburner rumble were detected and controlled. The usefulness of an altitude chamber for developing a software and testing hardware was proven. The flexibility of IPCS was demonstrated when an autothrottle, an in-flight thrust calculation, and a coannular noise study capability were added at the end of the flight tests.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-653 , Propulsion Conference; Jul 26, 1976 - Jul 29, 1976; Palo Alto, CA
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  • 63
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    Variable-cycle engines for supersonic cruising aircraft (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The paper reviews the evolution and current status of selected recent variable-cycle engine (VCE) studies and describes how the results are influenced by airplane requirements. The engine/airplane studies are intended to identify promising VCE concepts, simplify their designs and identify the potential benefits in terms of aircraft performance. This includes range, noise, emissions, and the time and effort it may require to ensure technical readiness of sufficient depth to satisfy reasonable economic, performance, and environmental constraints. A brief overview of closely-related, on-going technology programs in acoustics and exhaust emissions is presented. It is shown that realistic technology advancements in critical areas combined with well matched aircraft and selected VCE concepts can lead to significantly improved economic and environmental performance relative to first-generation SST predictions.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-759 , Propulsion Conference; Jul 26, 1976 - Jul 29, 1976; Palo Alto, CA
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  • 64
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    Boundary layer thickness effect on boattail drag (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A combined experimental and analytical program has been conducted at the NASA Lewis Research Center, to investigate the effects of boundary layer changes on the flow over high angle boattail nozzles. The tests were run on an isolated axisymmetric sting mounted model. Various boattail geometries were investigated at high subsonic speeds over a range of boundary layer thicknesses. In general, boundary layer effects were small at speeds up to Mach 0.8. However, at higher speeds significant regions of separated flow were present on the boattail. When separation was present large reductions in boattail drag resulted with increasing boundary layer thickness. The analysis predicts both of these trends.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-676 , Propulsion Conference; Jul 26, 1976 - Jul 29, 1976; Palo Alto, CA
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  • 65
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    Investigation of upper-surface-blowing nacelle integration at cruise speeds utilizing powered engine simulators (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Various overwing nacelle designs were investigated on a representative four-engine short-haul aircraft configuration during a combined analytical and experimental program. Design conditions were a Mach number of 0.7 and a lift coefficient of 0.4. All nacelles had D-shaped nozzle exits and included a streamline-contoured design, a low boattail angle reference configuration, and a high boattail angle powered lift design. Testing was done with the design four-engine airplane configuration as well as with only inboard nacelles installed. Turbopowered engine simulators were used to provide realistic representation of nacelle flows. Performance trends are compared for the various nacelle designs. In addition, comparisons are presented between analytical and experimental pressure distributions and between flow-through and powered simulator results.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-623 , Propulsion Conference; Jul 26, 1976 - Jul 29, 1976; Palo Alto, CA
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  • 66
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    Swirling-flow jet noise suppressors for aircraft engines (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Experimental investigations of the effects of swirling the jet exhausts of small turbofan and turbojet engines have indicated significant progress towards predicting and attaining substantial jet noise abatement with minimum thrust losses in large aircraft engines. Systematic variations of the important swirl vane and swirling flow parameters were conducted to determine their effects on jet noise reduction and engine performance. Since swirling flow becomes more effective in reducing jet noise as the density and temperature gradients increase, the significant trends in noise reduction and engine performance that were established by these parametric studies could be projected into potentially greater reductions of sound pressure levels with minimum thrust losses by controlled swirling of the jets of high thrust engines. The density and temperature gradients in the jet exhausts of high thrust engines are larger by comparison with gradients in small engines.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-508 , Aero-Acoustics Conference; Jul 20, 1976 - Jul 23, 1976; Palo Alto, CA
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  • 67
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    Potential improvements in turbofan engine fuel economy (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The method developed for initial evaluation of possible performance improvements in the NASA Aircraft Energy Efficiency Program, directed toward improving the fuel economy of turbofan engines, is outlined, and results of the evaluation of 100 candidate engine modifications are presented. The study indicates that fuel consumption improvements of as much as 5% may be possible in current JT3D, JT8D, and JT9D turbofan engines. Aerodynamic, thermodynamic, material, and structural advances are expected to yield fuel consumption improvements on the order of 10 to 15% in advanced turbofan engines, with the greatest improvement stemming from significantly higher cycle pressure ratios. Higher turbine temperature and fan bypass ratios are also expected to contribute to fuel conservation.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-666 , Propulsion Conference; Jul 26, 1976 - Jul 29, 1976; Palo Alto, CA
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  • 68
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    Results of the NASA/General Electric Experimental Clean Combustor Program (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The NASA/General Electric Experimental Clean Combustor Program is a multi-year, major contract effort. Primary program objectives are the generation of technology for development of advanced commercial CTOL engines with lower exhaust emissions than current aircraft and, demonstrations of this technology in a full-scale CF6-50C engine in 1976. This paper describes pollution and performance goals, Phase I and II test results and Phase III hardware, pollution sampling techniques and test plans. Pollution results are presented in emission index and Environmental Protection Agency 1979 Standard Parameters (EPAP). Best results were obtained with a double annular combustor concept. This concept, which incorporates multistage burning, produced EPAP values extrapolated to CF6-50C engine conditions for CO, HC, and NOx of 3.3, 0.3 and 4.5, respectively. These represent respective CO, HC and NOx percentage reductions of 69, 93 and 42%, compared to current CF6-50 engine values. The combustor also met development engine performance requirements.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-763 , Propulsion Conference; Jul 26, 1976 - Jul 29, 1976; Palo Alto, CA
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  • 69
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    Low pollution combustor designs for CTOL engines - Results of the Experimental Clean Combustor Program (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The NASA/Pratt & Whitney Aircraft Experimental Clean Combustor Program is a multi-year, major contract effort. Primary program objectives are the generation of combustor technology for development of advanced commercial CTOL engines with lower exhaust emissions than current aircraft and demonstration of this technology in a full-scale JT9D engine in 1976. This paper describes the pollution and performance goals, Phase I and II test results, and the Phase III combustor hardware, pollution sampling techniques, and test plans. Best results were obtained with the Vorbix concept which employs multiple burning zones and improved fuel preparation and distribution. Substantial reductions were achieved in all pollutant categories, meeting the 1979 EPA standards for NOx, THC, and smoke when extrapolated to JT9D cycle conditions. The Vorbix concept additionally demonstrated the capability for acceptable altitude relight and did not appear to have unsolvable durability or exit temperature distribution problems.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-762 , Propulsion Conference; Jul 26, 1976 - Jul 29, 1976; Palo Alto, CA
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  • 70
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    The pollution reduction technology program for can-annular combustor engines - Description and results (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Pollutant reduction and performance characteristics were determined for three successively more advanced combustor concepts. Program Element I consisted of minor modifications to the current production JT8D combustor and fuel system to evaluate means of improved fuel preparation and changes to the basic airflow distribution. Element II addressed versions of the two-staged Vorbix (vortex burning and mixing) combustor and represented a moderate increase in hardware complexity and difficulty of development. The concept selected for Element III employed vaporized fuel as a means of achieving minimum emission levels and represented the greatest difficulty of development and adaptation to the JT8D engine. Test results indicate that the Element I single-stage combustors were capable of dramatic improvement in idle pollutants. The multistage combustors evaluated in Program Elements II and III simultaneously reduced CO, THC and NOx emissions, but were unable to satisfy the current 1979 EPA standards.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-761 , Propulsion Conference; Jul 26, 1976 - Jul 29, 1976; Palo Alto, CA
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  • 71
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    Results of the pollution reduction technology program for turboprop engines (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A program was performed to evolve and demonstrate advanced combustor technology aimed at achieving the 1979 EPA standards for turboprop engines (Class P2). The engine selected for this program was the 501-D22A turboprop manufactured by Detroit Diesel Allison Division of General Motors Corporation. Three combustor concepts were designed and tested in a combustor rig at the exact combustor operating conditions of the 501-D22A engine over the EPA landing-takeoff cycle. Each combustor concept exhibited pollutant emissions well below the EPA standards, achieving substantial reductions in unburned hydrocarbons, carbon monoxide, and smoke emissions compared with emissions from the production combustor of this engine. Oxides of nitrogen emissions remained well below the EPA standards, also.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-760 , Propulsion Conference; Jul 26, 1976 - Jul 29, 1976; Palo Alto, CA
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  • 72
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    Stagnation region gas film cooling for turbine blade leading edge applications (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An experimental investigation was conducted to model the film-cooling performance for a turbine-vane leading edge using the stagnation region of a cylinder in cross flow. Experiments were conducted with a single row of spanwise-angled coolant holes for a range of the coolant blowing ratio with a freestream-to-wall temperature ratio of about 2.1 and a Reynolds number of 170,000, characteristic of the gas-turbine environment. Data from local heat-flux measurements are presented for coolant-hole injection angles of 25, 35, and 45 deg with the row of holes located at three positions relative to the stagnation line on the cylinder. Results show the spanwise (hole-to-hole) variation of heat-flux reduction due to film cooling and indicate conditions for the optimum film-cooling performance.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-728 , Propulsion Conference; Jul 26, 1976 - Jul 29, 1976; Palo Alto, CA
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  • 73
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    The NASA Pollution-Reduction Technology Program for small jet aircraft engines - A status report (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A three-phase experimental program is described which has the objective of enabling EPA Class T1 jet engines to meet the 1979 EPA emissions standards. In Phase I, three advanced combustor concepts, designed for the AiResearch TFE 731-2 turbofan engine, were evaluated in screening tests. Goals for carbon monoxide and unburned hydrocarbons were met or closely approached with two of the concepts with relatively modest departures from conventional combustor design practices. A more advanced premixing/prevaporizing combustor, while appearing to have the potential for meeting the oxides of nitrogen goal as well, will require extensive development to make it a practical combustion system. Smoke numbers for the two combustor concepts which will be carried forward into Phase II of the program were well within the EPA smoke standard. Phase II, Combustor-Engine Compatibility Testing, which is in its early stages, and planned Phase III, Combustor-Engine Demonstration Testing, are also described.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-616 , Propulsion Conference; Jul 26, 1976 - Jul 29, 1976; Palo Alto, CA
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  • 74
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    Design study of a gas turbine combustor with heat recirculation (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A means of avoiding stoichiometric combustion, reducing emissions, and yet providing stable burning for lean mixtures is based on the use of heat recirculation rather than flow recirculation. This paper is concerned with the calculations of the design parameters of a gas turbine combustor with heat exchanger to produce the desired preheat temperature. The combustor inlet temperature, maximum temperature, equivalence ratio and recirculated heat are determined by thermodynamic analysis. The heat transfer analysis then provides the dimensions of the system to produce the predetermined boundary conditions. It is indicated that practical combustor design may be feasible for reactant mixtures as low as equivalence ratio 0.2.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-611 , Propulsion Conference; Jul 26, 1976 - Jul 29, 1976; Palo Alto, CA
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  • 75
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    Mixing and combustion of an underexpanded H2 jet in supersonic flow (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Theoretical calculations are compared with experimental data in an investigation of the injection, mixing, and combustion of an underexpanded hydrogen jet in a supersonic test stream. The experimental tests in reacting and nonreacting flows were conducted by use of air and nitrogen as test media. Tests were conducted in a free jet and a ducted mode. Theoretical calculations were performed with a modified viscous characteristics analysis. The computer program employs finite rate chemistry and a turbulent viscosity model which varies radially and axially; it handles exit shock waves, expansion fans, and thermal compressions generated in the reacting flow fields. Comparison of the theory and experimental data indicates good agreement for the near flow field; this agreement is directly related to the explicit handling of the near-field shock and expansion waves. Less satisfactory agreement at downstream locations for both free jet and ducted flows is attributed to the lack of continued computation of the shocks and expansions in the far field.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-610 , Propulsion Conference; Jul 26, 1976 - Jul 29, 1976; Palo Alto, CA
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  • 76
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    An investigation of possible causes for the reduction of fan noise in flight (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An experimental investigation of the impact on fan tone-noise generation of several engine inflow distortions found in conventional static testing has been made. Inflow distortions examined included the ground vortex, atmospheric turbulence, and test-stand structure interference. This work was undertaken to help explain results from noise measurements made on modern turbofan engines which show lower fan tone levels in flight at the blade-passing frequency than are predicted from static measurements. The results indicate that the ground vortex can greatly increase noise at the blade-passing frequency. A special inlet was designed to examine the effects of atmospheric turbulence. Use of this inlet reduced the variability of the sound-pressure level at the blade-passing frequency, and the results were similar to those found in flight.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-585 , Aero-Acoustics Conference; Jul 20, 1976 - Jul 23, 1976; Palo Alto, CA
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  • 77
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    Noise reduction from the redesign of a fan stage to minimize stator lift fluctuations (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An existing fan stage, redesigned to reduce stator lift fluctuations, was acoustically tested for reduced noise generation. The lift fluctuations on the stator were reduced by increasing the stator chord, adjusting incidence angles, and by adjusting the rotor velocity diagrams. The experiments showed significantly reduced broadband noise levels in the middle to high frequencies. Blade passage tone power was not reduced, but decreases in the harmonics were observed. Aerodynamic improvements in both performance and efficiency were obtained.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-576 , Aero-Acoustics Conference; Jul 20, 1976 - Jul 23, 1976; Palo Alto, CA
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  • 78
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    Acoustic and aerodynamic effects of rotor pitch angle for a variable-pitch, 6-foot diameter fan stage (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: An externally driven, 1.2 pressure ratio full-scale fan stage with an adjustable pitch rotor was tested in an outdoor facility at the Lewis Research Center. Rotor pitch angles resulting in minimum sideline perceived noise levels are defined as a function of stage thrust. Thrust-corrected fan noise variations are examined for operation at constant thrust, rotor tip speed, and stage work coefficient. At constant stage thrust, reducing the rotor pitch angle below design values increased the fan noise with the greatest change occurring in the blade passing tone level. At constant fan speed the minimum noise occurred at a particular rotor pitch angle, which was not the minimum thrust condition. With constant stage work coefficient, rear quadrant noise increased at above-design speed conditions.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-573 , Aero-Acoustics Conference; Jul 20, 1976 - Jul 23, 1976; Palo Alto, CA
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  • 79
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    Influence of blade characteristics on axial flow compressor noise (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This experimental study was initiated as a result of earlier theoretical work which found that changes in the spanwise circulation distribution can have a significant influence on noise generation for the single rotor and for rotor-stator combinations. The experimental results presented here clearly show that the rotor noise, and especially the rotor-stator interaction noise, is affected by the type of radial loading, i.e., type of twist. Other blade parameters tested for their influence on far-field noise include rotor solidity, spacing between rotor and stator for twisted and untwisted blades, blade thickness, and stator chord length; radial effects on cutoff were also investigated.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-570 , Aero-Acoustics Conference; Jul 20, 1976 - Jul 23, 1976; Palo Alto, CA
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  • 80
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    Noise comparisons of single and two stage demonstrator fans for advanced technology aircraft (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A high-speed single-stage and a low-speed two-stage fan were designed, fabricated and tested to demonstrate their predicted low noise performance for an advanced 0.85-0.90 cruise Mach number aircraft requiring a 1.8-1.9 pressure ratio fan. Acoustic tests were made with both unsuppressed and suppressed configurations. The two-stage fan demonstrated that quiet fan technology developed for low-speed single-stage fan is applicable to two-stage designs. The unsuppressed two-stage fan was 3-5 dB quieter than the high-speed single-stage fan at the same pressure ratio. The unsuppressed high-speed single-stage fan demonstrated that significant reductions in inlet noise can be achieved from the sonic blockage caused by supersonic flow in the rotor blading. Both fans demonstrated suppressed inlet noise levels with treated sonic inlets that met advanced technology goals. Suppressed aft noise levels did not meet expectations for either fan. The aft noise problem is attributed to both excessive source noise and ineffective treatment performance.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-572 , Aero-Acoustics Conference; Jul 20, 1976 - Jul 23, 1976; Palo Alto, CA
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  • 81
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    Effect of loading and rotor wake characteristics on the acoustic field of stator blades (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The generation of blade passing frequency noise due to rotor wakes interaction with the downstream stator is examined using a recent model for the unsteady aerodynamic forces developed by Goldstein and Atassi. The effects of blade geometry and loading are investigated. It is shown that at low reduced frequencies loading significantly reduces the noise level while at high frequencies loading substantially increases the sound level radiated. It is also shown that for the same loading a higher angle of attack generates more noise particularly at higher reduced frequencies. The noise level shows a quasi-periodic pattern with pronounced minima and maxima as the frequency increases. These conclusions are valid for different wake models.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-566 , Aero-Acoustics Conference; Jul 20, 1976 - Jul 23, 1976; Palo Alto, CA
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  • 82
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    Flight effects on JT8D engine jet noise as measured in the NASA Ames 40-by 80-foot wind tunnel (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A JT8D-17 turbofan engine was tested in a 40 x 80 ft wind tunnel to determine flight effects on jet noise. The engine was configured as a baseline with conical nozzle, a quiet nacelle 20-lobe ejector/suppressor, and an internal mixer with conical nozzle. Tunnel-off and tunnel-on noise tests were conducted over a range of nozzle pressure ratios (1.2 to 2.1), primary jet velocities (275 to 550 m/s), and tunnel velocities up to 100 m/s. Aft quadrant noise data were measured by a pair of traversing microphones located on a 3-m sideline relative to the engine centerline. Unique correlations and analysis procedures were developed in order to define far-field flight effects from the relatively near-field noise measurements. The ejector/suppressor experienced a significant loss of suppression relative to static measurements during flight while the internal mixer indicated a slight gain in suppression. It is concluded that the wind tunnel is a viable method for studying flight effects on engine jet noise.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-556 , Aero-Acoustics Conference; Jul 20, 1976 - Jul 23, 1976; Palo Alto, CA
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  • 83
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    Wing shielding of high-velocity jet and shock-associated noise with cold and hot flow jets (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Jet exhaust noise shielding data are presented for cold and hot flows (ambient to 1100 K) and pressure ratios from 1.7 to 2.75. A nominal 9.5-cm diameter conical nozzle was used with simple shielding surfaces that were varied in length from 28.8 to 114.3 cm. The nozzle was located 8.8 cm above the surfaces. The acoustic data with the various shielding lengths are compared to each other and to that for the nozzle alone. In general, short shielding surfaces that provided shielding for subsonic jets did not provide as much shielding for jets with shock noise; however, long shielding surfaces did shield shock noise effectively.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-547 , Aero-Acoustics Conference; Jul 20, 1976 - Jul 23, 1976; Palo Alto, CA
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  • 84
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    Noise reduction as affected by the extent and distribution of acoustic treatment in a turbofan engine inlet (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: An inlet noise suppressor for a TF-34 engine designed to have three acoustically treated rings was tested with several different ring arrangements. The configurations included: all three rings; two outer rings; single outer ring; single intermediate ring, and finally no rings. It was expected that as rings were removed, the acoustic performance would be degraded considerably. While a degradation occurred, it was not as large as predictions indicated. In fact, the prediction showed good agreement with the data only for the full-ring inlet configuration. The under-predictions which occurred with ring removal were believed a result of ignoring the presence of spinning modes which are known to damp more rapidly in cylindrical ducts than would be predicted by least attenuated mode or plane wave analysis.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-541 , Aero-Acoustics Conference; Jul 20, 1976 - Jul 23, 1976; Palo Alto, CA
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  • 85
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    The aerodynamic and acoustic characteristics of an over-the-wing target-type thrust reverser model (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A static test of a large-scale, over-the-wing (OTW) powered-lift model was performed. The OTW propulsion system had been modified to incorporate a simple target-type thrust reverser as well as the normal rectangular OTW exhaust nozzle. Tests were performed in both the reverse thrust and approach configurations. The thrust reverser noise created by jet turbulence mixing and the OTW approach noise were both low frequency and broadband. When scaled to a 45,400-kg (100,000-lb) aircraft, the thrust reverser and approach configurations produced peak 152-m (500-ft) sideline perceived noise levels of 110 and 105 PNdB, respectively. The aerodynamic performance of the model showed that 50% or greater reverser effectiveness can be achieved without experiencing ingestion of exhaust gas or ground debris into the engine inlets.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-523 , Aero-Acoustics Conference; Jul 20, 1976 - Jul 23, 1976; Palo Alto, CA
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  • 86
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    Fuel conservative propulsion concepts for future air transports (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The results of a feasibility study of proposed fuel conservative propulsion concepts for air transports with an assumed Mach 0.8 cruise capability are summarized. All engines considered are based on projected 1985 technology. Operating fuel requirements, propulsion operating costs, and noise characteristics are compared with those of a present technology turbofan engine. The study indicates that an advanced Brayton cycle gas generator in a turbofan engine or geared to an advanced multibladed, small diameter propeller with a projected efficiency of 80% at Mach 0.8 offers the greatest potential for energy conservation.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: SAE PAPER 760535 , Air Transportation Meeting; May 18, 1976 - May 20, 1976; New York, NY
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  • 87
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    Progress report on propeller aircraft flyover noise research (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Initial results of a program to investigate the sources of noise in unshrouded propellers under forward flight conditions are reported. Tests were conducted using a three-blade full-scale instrumented propeller mounted on a twin-engine aircraft. Measurements included (1) far-field noise at fixed ground stations and at two aircraft wing tip locations, (2) blade surface pressures at seven locations on one of the propeller blades, (3) atmospheric turbulence encountered by the aircraft in flight, and (4) aircraft operating conditions. The results confirm that significantly lower levels of propeller noise are produced in forward flight than at static conditions. It is tentatively concluded that propeller noise generation in flight may be dominated by steady loading at blade passage frequency, but at higher frequencies unsteady loading due to interaction with natural atmospheric turbulence may be the dominant mechanism of noise generation. Under static conditions the total noise signature appears to be the result of interaction of the propeller with persistent turbulent eddies passing through the propeller disk.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: SAE PAPER 760454 , Business Aircraft Meeting; Apr 06, 1976 - Apr 09, 1976; Wichita, Kan.
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  • 88
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    Program plan for the design and spin test of ceramic blade-metal disk attachments (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: A current NASA-sponsored contract will develop attachment technology for hybrid turbine rotors having dovetailed ceramic blades and a wrought metal disk. The approach and sequence of activities are described in detail. The program scope includes design, fabrication, and spin testing of hot-pressed silicon nitride blades for operation at rotor inlet temperatures of 2192 F (1200 C) or greater.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: ASME PAPER 76-GT-37 , Gas Turbine Conference and Products Show; Mar 21, 1976 - Mar 25, 1976; New Orleans, LA
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  • 89
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    Advanced turbine disk designs to increase reliability of aircraft engines (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Results of analytical studies to improve the low cycle fatigue lives and reliability of turbine disks in high-performance gas turbine engines are presented. Advanced disk concepts were evaluated for the first-stage high pressure turbines of the CF6-50 and JT8D-17 engines. The advanced disk designs are compared to the existing disks on the bases of cycles to crack initiation and overspeed capability for initially unflawed disks, crack propagation cycles to failure for initially flawed disks, and available kinetic energy of disk burst fragments.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Gas Turbine Conference and Products Show; Mar 21, 1976 - Mar 25, 1976; New Orleans, LA
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  • 90
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    Advanced low NO/x/ combustors for supersonic high-altitude aircraft gas turbines (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A test rig program was conducted with the objective of evaluating and minimizing the exhaust emissions, in particular NO(x), of two advanced aircraft combustor concepts at a simulated, high-altitude cruise condition. The two combustor designs, both members of the lean-reaction, pre-mixed family, are known as the Jet Induced Circulation (JIC) combustor and the Vortex Air Blast (VAB) combustor and were rig tested in the form of reverse flow can combustors in the 0.127-m size range. Various configuration modifications were applied to each of the initial JIC and VAB combustor model designs in an effort to reduce the emissions levels. The VAB combustor demonstrated a NO(x) level of 1.1 gm NO2/kg fuel with essentially 100 percent combustion efficiency at the simulated cruise combustor condition of 507 kPa, 833 K inlet pressure and temperature, respectively and 1778 K outlet temperature on Jet-A1 fuel. In addition, emissions data were obtained at low combustor inlet pressure and temperatures that indicate the potential performance at engine off-design conditions.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: ASME PAPER 76-GT-12 , Gas Turbine Conference and Products Show; Mar 21, 1976 - Mar 25, 1976; New Orleans, LA
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  • 91
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    Jet noise characteristics of unsuppressed duct burning turbofan exhaust system (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: Recent aero-acoustic tests of model coannular nozzles have shown that less noise is generated if the higher-velocity jet is exhausted from the outer annular passage rather than from the primary nozzle. These findings are of particular significance to a duct-burning turbofan (DBTF) engine being studied for application to an advanced supersonic transport. Unlike conventional turbofan engines that have peak velocities from the primary nozzle, it is possible to design a DBTF engine to have a fan velocity higher than that of the primary flow. Results are presented for a NASA-sponsored model test program that covers a range of fan to primary-area ratios from 0.75 to 1.2, and a range of fan to primary-velocity ratios from 0.4 to 2.8. Correlations are given that relate radiated sound power to fan velocity, fan to primary-velocity ratio, and fan to primary-area ratio. Corresponding exhaust-plume velocity-traverse data are presented which suggest that the observed noise benefits may be due to the more rapid decay of the annular flow because of shear stresses on the inner surface that result from the lower-velocity primary flow.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: AIAA PAPER 76-149 , Aerospace Sciences Meeting; Jan 26, 1976 - Jan 28, 1976; Washington, DC
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  • 92
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    The NASA pollution-reduction technology program for small jet aircraft engines (1976)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Three advanced combustor concepts, designed for the AiResearch TFE 731-2 turbofan engine, were evaluated in screening tests. Goals for carbon monoxide and unburned hydrocarbons were met or closely approached with two of the concepts with relatively modest departures from conventional combustor design practices. A more advanced premixing/prevaporizing combustor, while appearing to have the potential for meeting the oxides of nitrogen goal as well, will require extensive development to make it a practical combustion system. Smoke numbers for the two combustor concepts were well within the EPA smoke standard. Phase 2, Combustor-Engine Compatibility Testing, which is in its early stages, and planned Phase 3, Combustor-Engine Demonstration Testing, are also described.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-X-73419 , E-8757 , Propulsion Conf.; Jul 26, 1976 - Jul 29, 1976; Palo Alto, CA; United States
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  • 93
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    Analysis and design of a high tip speed, low noise aircraft fan incorporating swept leading edge rotor and stator blades (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-135092 , BBN-3332
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  • 94
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    Application of polynomial techniques to multivariable control of jet engines (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: This paper describes a complete case study of the application of the theory of minimal design to multivariable control of jet engines. The minimal-design problem is approached from the viewpoint of polynomial modules, and computational experience with PL/I and FORMAC-PL/I software is discussed. The complete minimal-design solution exhibits flexibilities not apparent in early industry studies, and a matrix approach to pole assignment can be used to advantage in this situation.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: International Symposium on Multivariable technological systems; Jul 04, 1977 - Jul 08, 1977; New Brunswick; Canada
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  • 95
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    Direct-connect test of a hydrogen-fueled three-strut injector for an integrated modular scramjet engine (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The study aims at illustrating the effects of strut and injector interactions and strut wakes not totally simulated in previous, less complex, direct-connect hardware. In addition, the influence of the relative location of the injectors on opposite sides of each strut and the effect of injector spacing are evaluated. It is shown that better mixing efficiency is attained by locating the fuel injectors on opposite sides of a strut so that the jets come together, rather than being staggered, in the strut wake. It is not possible to determine the combustion efficiency by means of a one-dimensional analysis of the wall pressure.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Combustion Meeting; Aug 15, 1977 - Aug 17, 1977; Colorado Springs, CO
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  • 96
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    An empirical model for inverted-velocity-profile jet noise prediction (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An empirical model for predicting the noise from inverted-velocity-profile coaxial or coannular jets is presented and compared with small-scale static and simulated flight data. The model considered the combined contributions of as many as four uncorrelated constituent sources: the premerged-jet/ambient mixing region, the merged-jet/ambient mixing region, outer-stream shock/turbulence interaction, and inner-stream shock/turbulence interaction. The noise from the merged region occurs at relatively low frequency and is modeled as the contribution of a circular jet at merged conditions and total exhaust area, with the high frequencies attenuated. The noise from the premerged region occurs at high frequency and is modeled as the contribution of an equivalent plug nozzle at outer stream conditions, with the low frequencies attenuated.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-73838 , E-9425 , Meeting of the Acoustical Soc. of Am.; Dec 13, 1977 - Dec 16, 1977; Miami, FL; United States
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  • 97
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    The promise of eutectics for aircraft turbines (1977)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: The current status of the first generation eutectics, gamma/gamma transition - delta and NiTaC-13, is described in detail. Several second generation systems, such as gamma/gamma transition - alpha and NiTaC 3-116A, gamma - beta, and COTAC 74 are also reviewed with particular emphasis on their critical physical and mechanical properties, future research directions, and potential applications. Results of recent cost-benefit analyses of eutectic turbine blades are discussed.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-TM-73714 , E-9258 , Mater. Show and Conf.; Oct 25, 1977 - Oct 27, 1977; Chicago
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  • 98
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    Direct-connect tests of hydrogen-fueled supersonic combustors (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Direct-connect tests of hydrogen-fueled supersonic combustors were performed using arc-heated air at combustor inlet Mach numbers of 2.9 to 3.2. Various axisymmetric combustor geometries of 5.89 and 6.96 cm (inner diameter) inlet were investigated; the fuel was injected from the wall either from a ring of equally spaced holes normal to the air stream, or from a circumferential slot oriented 45 deg downstream. The hole-type injectors consistently gave better results. The effects of various parameters are examined, and the performance comparison procedure is described. A theoretical model of the supersonic combustion process which includes a precombustion shock-compression is used to explain the character of the observed pressure distributions and to assess the effects of the measured heat transfer rates, deduced wall shear, and combustor geometry on performance.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: International Symposium on Combustion; Aug 15, 1976 - Aug 20, 1976; Cambridge, MA
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  • 99
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    Composite hubs for low cost turbine engines (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: A detailed stress analysis is performed using NASTRAN to demonstrate theoretically the adequacy of composite hubs for low cost turbine engine applications. The results show that composite hubs are adequate for this application from the steady state stress viewpoint.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Annual Conference on Discover reinforced plastics; Feb 08, 1977 - Feb 11, 1977; Washington, DC
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  • 100
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    Flight effects on exhaust noise for turbojet and turbofan engines - Comparison of experimental data with prediction (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: Recent experiments on the effects of flight on jet engine exhaust noise have produced apparently conflicting results. Some of these results do not agree with projections based on classical jet noise theories nor with experimental results from model jet simulated flight tests. It has been shown that in some of the cases reported, the proper corrections were not made to account for the distributed nature of the jet noise sources. It is shown herein that the remaining discrepancies can be reconciled by considering the combined effects of jet-mixing noise, internally-generated engine exhaust noise, and shock noise. This paper demonstrates that static and in-flight jet engine exhaust noise can be predicted with reasonable accuracy when the multiple-source nature of the problem is taken into account. Jet-mixing noise is predicted from an improved version of the NASA interim prediction method. Provisional methods of estimating internally-generated noise and shock noise flight effects are used, based partly on existing prediction methods and partly on recently reported engine data.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: Meeting of the Acoustical Society of America; Nov 16, 1976 - Nov 19, 1976; San Diego, CA
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