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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 451 records · Page 25
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

EBF noise suppression and aerodynamic penalties

Acoustic tests were conducted at model scale to determine the noise produced in the flyover and sideline planes at reduced separation distances between the nozzle exhaust plane and the flaps of an under-the-wing (UTW) externally blown flap (EBF) configuration in its approach attitude. Tests were also made to determine the noise suppression effectiveness of two types of passive devices which were located on the jet impingement surfaces of the configuration. In addition, static aerodynamic performance data were obtained to evaluate the penalties produced by these suppression devices. Broadband low frequency noise reductions were achieved by reducing the separation distance between the nozzle and flaps. However, mid and high frequency noise was produced which exceeded that of the reference configuration. Two passive noise suppression devices located on the flaps produced moderate to large noise reductions at reduced separation distances. Consideration of the static aerodynamic performance data obtained for the configurations tested suggests that specific broadband noise suppression characteristics may be obtained through a trade-off with aerodynamic performance penalties by the careful selection of suppression devices.

Mckinzie, L. J., Jr.↗
NASA NTRS1972

Effect of nozzle lateral spacing on afterbody drag and performance of twin-jet afterbody models with convergent-divergent nozzles at Mach numbers up to 2.2

Twin-jet afterbody models were investigated by using two balances to measure the thrust-minus-total drag and the afterbody drag, separately, at static conditions and at Mach numbers up to 2.2 for an angle of attack of 0 deg. Hinged-flap convergent-divergent nozzles were tested at subsonic-cruise- and maximum-afterburning-power settings with a high-pressure air system used to provide jet-total-pressure ratios up to 20. Two nozzle lateral spacings were studied, using afterbodies with similar interfairing shapes but with different longitudinal cross-sectional area distributions. Alternate, blunter, interfairings with different shapes for the two spacings, which produced afterbodies having identical cross-sectional area progressions corresponding to an axisymmetric minimum wave-drag configuration, were also tested. The results indicate that the wide-spaced configurations improved the flow field around the nozzles, thereby reducing drag on the cruise nozzles; however, the increased surface and projected cross-sectional areas caused an increase in afterbody drag. Except for a slight advantage with cruise nozzles at subsonic speeds, the wide-spaced configurations had the higher total drag at all other test conditions.

Pendergraft, O. C., Jr.↗
NASA NTRS1973

A flight investigation of the trailing vortices generated by a jumbo jet transport

A flight investigation has been conducted to study the velocity and persistence characteristics of the trailing vortices generated by a jumbo jet transport. The investigation showed that the tangential velocities were initially higher for vortices generated with the flaps up and that they persisted for longer distances behind the aircraft than those generated with the flaps down. The core radii with flaps down appeared to be generally larger than those with flaps up. The vertical locations of the vortices behind the generating aircraft varied from several hundred meters below the generating aircraft flight path at long ranges up to, and occasionally above, the flight path at short and moderate ranges.

Verstynen, H. A., Jr.↗
NASA NTRS1976

Effect of external jet-flow deflector geometry on OTW aero-acoustic characteristics

The effect of geometry variations in the design of external deflectors for use with over-the-wing (OTW) configurations was studied at model scale and subsonic jet velocities. Included in the variations were deflector size and angle as well as wing size and flap setting. A conical nozzle (5.2-cm diameter) mounted at 0.1 chord above and downstream of the wing leading edges was used. The data indicate that external deflectors provide satisfactory takeoff and approach aerodynamic performance and acoustic characteristics for OTW configurations. These characteristics together with expected good cruise aerodynamics, since external deflectors are storable, may provide optimum OTW design configurations.

Vonglahn, U.↗
NASA NTRS1976

Effect of external jet-flow deflector geometry on OTW aero-acoustic characteristics

The effect of geometry variations in the design of external deflectors for use with OTW configurations was studied at model scale and subsonic jet velocities. Included in the variations were deflector size and angle as well as wing size and flap setting. A conical nozzle (5.2-cm diameter) mounted at 0.1 chord above and downstream of the wing leading edges was used. The data indicate that external deflectors provide satisfactory take-off and approach aerodynamic performance and acoustic characteristics for OTW configurations. These characteristics together with expected good cruise aerodynamics, since external deflectors are storable, may provide optimum OTW design configurations.

Von Glahn, U.↗
NASA NTRS1977

Airframe noise of component interactions on a large transport model

Airframe noise produced by aircraft components and their interactions on a model of a wide body transport was investigated in an open jet anechoic flow facility. The two-meter span model had leading edge and multigapped trailing edge flaps, undercarriage, and associated stowage compartments. Each of these components were extended and retracted so their individual and interactive contributions to the measured airframe noise could be determined. An analysis of variance was performed which revealed a statistical significance of the component interactions. Various airframe noise reduction techniques were tried to reduce airframe noise. The effects of these techniques on the model's lift and drag were also measured.

Shearin, J. G.↗
NASA NTRS1973

The Buffalo/Spey jet-STOL research aircraft

The program to design and build a Buffalo/Spey Augmentor-Wing research aircraft is presented. The development of an internally blown flap system for the generation of powered lift is discussed. Modification, development, and testing of the Rolls-Royce Spey engine are reported. The ground tests and first flights of the aircraft are described and the application of the internally blown flap concept for short takeoff military transport aircraft is proposed.

Whittley, D. C.↗
NASA NTRS1974

Airframe noise - The next aircraft noise barrier

Progress in quieting the commercial aviation fleet has been achieved by reducing the noise generated by jet engines. Recent tests have indicated that noise produced by airflow over aircraft surfaces (lifting surfaces, landing gear, flaps, and cavities) is only 8 to 10 EPNdB below certification requirements for current aircraft and will likely be a design consideration for aircraft of the future as engines become still quieter. This paper reviews the state of the art for understanding, predicting, and control of airframe noise. Levels and spectral content of the noise, correlation with important variables, and noise generation mechansims are discussed. The noise floors for future aircraft, the direction of research projects, and likely impact of this new technology on aircraft design are indicated.

Morgan, H. G.↗
NASA NTRS1975

Investigation of scrubbing and impingement noise

Tests were conducted in an acoustic wind tunnel to determine surface pressure spectra and far field noise caused by turbulence impinging on an airfoil and turbulence convected past a sharp trailing edge. Measured effects of flow velocity and turbulence intensity were compared with predictions from several theories. Also, tests were conducted in an anechoic chamber to determine surface pressure spectra and far field noise caused by a deflected airfoil scrubbed by a subsonic jet. This installation simulated both an under-the-wing and an upper-surface-blowing externally blown flap, depending on the deflection angle. Surface and far field spectra, and cross correlation coherence and delay time, were utilized to infer the major noise-producing mechanisms.

Fink, M. R.↗
NASA NTRS1975

Propulsion system noise reduction

The progress in propulsion system noise reduction is reviewed. The noise technology areas discussed include: fan noise; advances in suppression including conventional acoustic treatment, high Mach number inlets, and wing shielding; engine core noise; flap noise from both under-the-wing and over-the-wing powered-lift systems; supersonic jet noise suppression; and the NASA program in noise prediction.

Feiler, C. E.↗
NASA NTRS1979

Investigation of surface fluctuating pressures on a 1/4 scale YC-14 upper surface blown flap model

Fluctuating pressures were measured at 30 positions on the surface of a 1/4-scale YC-14 wing and fuselage model during an outdoor static testing program. These data were obtained as part of a NASA program to study the fluctuating loads imposed on STOL aircraft configurations and to further the understanding of the scaling laws of unsteady surface pressure fields. Fluctuating pressure data were recorded at several discrete engine thrust settings for each of 16 configurations of the model. These data were reduced using the technique of random data analysis to obtain auto-and cross-spectral density functions and coherence functions for frequencies from 0 to 10 kHz, and cross-correlation functions for time delays from 0 to 10.24 ms. Results of this program provide the following items of particular interest: (1) Good collapse of normalized PSD functions on the USB flap was found using a technique applied by Lilley and Hodgson to data from a laboratory wall-jet apparatus. (2) Results indicate that the fluctuating pressure loading on surfaces washed by the jet exhaust flow was dominated by hydrodynamic pressure variations, loading on surface well outside the flow region dominated by acoustic pressure variations, and loading near the flow boundaries from a mixture of the two.

Pappa, R. S.↗
NASA NTRS1981

Analysis of data from a wind tunnel investigation of a large-scale model of a highly maneuverable supersonic V/STOL fighter - STOL configuration

The surface pressure and thermal characteristics of a large-scale model of a highly maneuverable supersonic fighter with STOL capability are described. The 7.28 m span model is powered by two J-97 turbojets, operated at 9340 N thrust. It combines upper-surface and spanwise blowing to augment the lift characteristics over a wide angle-of-attack range. The most significant feature of the fighter's flow field is the leading edge vortex that forms at low alphas, grows stronger, and moves inboard as alpha is increased. Upper surface blowing enhanced the lift on the wing in both stalled and unstalled areas significantly, while generating only a modest aft shift in the center of pressure. Lift gains were greatest at high alphas and with the flap deflected. Spanwise blowing was most significant at angles-of-attack greater than 8 deg, when the jet strengthened the vortex. The 1100 F spanwise blowing jet mixed very rapidly with the wing flow field, creating a maximum temperature rise of only 300-350 F. A comparison of small-scale and large-scale model wing pressure characteristics showed similar trends created by upper surface blowing, while spanwise blowing characteristics differed considerably. Force data correlated well with semi-empirical predictions for gross thrust coefficients less than 1.0.

Falarski, M. D.↗
NASA NTRS2008

Preliminary Analysis of Acoustic Measurements from the NASA-Gulfstream Airframe Noise Flight Test

The NASA-Gulfstream joint Airframe Noise Flight Test program was conducted at the NASA Wallops Flight Facility during October, 2006. The primary objective of the AFN flight test was to acquire baseline airframe noise data on a regional jet class of transport in order to determine noise source strengths and distributions for model validation. To accomplish this task, two measuring systems were used: a ground-based microphone array and individual microphones. Acoustic data for a Gulfstream G550 aircraft were acquired over the course of ten days. Over twenty-four test conditions were flown. The test matrix was designed to provide an acoustic characterization of both the full aircraft and individual airframe components and included cruise to landing configurations. Noise sources were isolated by selectively deploying individual components (flaps, main landing gear, nose gear, spoilers, etc.) and altering the airspeed, glide path, and engine settings. The AFN flight test program confirmed that the airframe is a major contributor to the noise from regional jets during landing operations. Sound pressure levels from the individual microphones on the ground revealed the flap system to be the dominant airframe noise source for the G550 aircraft. The corresponding array beamform maps showed that most of the radiated sound from the flaps originates from the side edges. Using velocity to the sixth power and Strouhal scaling of the sound pressure spectra obtained at different speeds failed to collapse the data into a single spectrum. The best data collapse was obtained when the frequencies were left unscaled.

Khorrami, Mehdi R.↗
NASA NTRS1985

Discussion of the paper, Some Aspects of Propulsion for the Augmenter-Wing Concept, by D. C. Whittley

Many modern concepts for STOL and V/STOL aircraft rely on integration of the propulsion system with the wing to create favorable lift interactions, and are known as powered lift concepts. A study of powered lift, concerning management and control of the various propulsive streams or jets is presented, each concept having its own particular objectives and requirements. Some specific objectives of this kind are described which relate to the augmentor wing. Consideration is given to three aspects of the subject, namely the augmentor flap itself, the wind ducting and augmentor primary nozzle, and the choice of powerplant or engine cycle. More generally, comments are made regarding noise attenuation and the prospect for achieving a low overall noise level for jet STOL aircraft of the future.

Schmitt, H.↗
NASA NTRS2002

Thermal Protection System Evaluation Using Arc-jet Flows: Flight Simulation or Research Tool?

The arc-jet has been used to evaluate thermal protection systems (TPS) and materials for the past forty years. Systems that have been studied in this environmerd include ablators, active, and passive TPS concepts designed for vehicles entering planetary and Earth atmospheres. The question of whether arc-jet flow can simulate a flight environment or is it a research tool that provides an aero-thermodynamic heating environment to obtain critical material properties will be addressed. Stagnation point tests in arc-jets are commonly used to obtain material properties such as mass loss rates, thermal chemical stability data, optical properties, and surface catalytic efficiency. These properties are required in computational fluid dynamic codes to accurately predict the performance of a TPS during flight. Special facilities have been developed at NASA Ames Research Center to approximate the flow environment over the mid-fuselage and body flap regions of proposed space-planes type vehicles. This paper compares flow environments generated in flight over a vehicle with those created over an arc-jet test articles in terms of scale, chemistry, and fluid dynamic properties. Flight experiments are essential in order to validate the material properties obtained from arc-jet tests and used to predict flight performance of any TPS being considered for use on a vehicle entering the Earth atmosphere at hypersonic speed.

Stewart, David A.↗
NASA NTRS2006

Technologies for Aircraft Noise Reduction

Technologies for aircraft noise reduction have been developed by NASA over the past 15 years through the Advanced Subsonic Technology (AST) Noise Reduction Program and the Quiet Aircraft Technology (QAT) project. This presentation summarizes highlights from these programs and anticipated noise reduction benefits for communities surrounding airports. Historical progress in noise reduction and technologies available for future aircraft/engine development are identified. Technologies address aircraft/engine components including fans, exhaust nozzles, landing gear, and flap systems. New "chevron" nozzles have been developed and implemented on several aircraft in production today that provide significant jet noise reduction. New engines using Ultra-High Bypass (UHB) ratios are projected to provide about 10 EPNdB (Effective Perceived Noise Level in decibels) engine noise reduction relative to the average fleet that was flying in 1997. Audio files are embedded in the presentation that estimate the sound levels for a 35,000 pound thrust engine for takeoff and approach power conditions. The predictions are based on actual model scale data that was obtained by NASA. Finally, conceptual pictures are shown that look toward future aircraft/propulsion systems that might be used to obtain further noise reduction.

Huff, Dennis L.↗
NASA NTRS2012

Aeroacoustic Study of a High-Fidelity Aircraft Model: Part 1- Steady Aerodynamic Measurements

In this paper, we present steady aerodynamic measurements for an 18% scale model of a Gulfstream air-craft. The high fidelity and highly-instrumented semi-span model was developed to perform detailed aeroacoustic studies of airframe noise associated with main landing gear/flap components and gear-flap interaction noise, as well as to evaluate novel noise reduction concepts. The aeroacoustic tests, being conducted in the NASA Langley Research Center 14- by 22-Foot Subsonic Tunnel, are split into two entries. The first entry, completed November 2010, was entirely devoted to the detailed mapping of the aerodynamic characteristics of the fabricated model. Flap deflections of 39?, 20?, and 0? with the main landing gear on and off were tested at Mach numbers of 0.16, 0.20, and 0.24. Additionally, for each flap deflection, the model was tested with the tunnel both in the closed-wall and open-wall (jet) modes. During this first entry, global forces (lift and drag) and extensive steady and unsteady surface pressure measurements were obtained. Preliminary analysis of the measured forces indicates that lift, drag, and stall characteristics compare favorably with Gulfstream?s high Reynolds number flight data. The favorable comparison between wind-tunnel and flight data allows the semi-span model to be used as a test bed for developing/evaluating airframe noise reduction concepts under a relevant environment. Moreover, initial comparison of the aerodynamic measurements obtained with the tunnel in the closed- and open-wall configurations shows similar aerodynamic behavior. This permits the acoustic and off-surface flow measurements, planned for the second entry, to be conducted with the tunnel in the open-jet mode.

Khorrami, Mehdi R.↗
NASA NTRS1973

Noise tests of a high-aspect-ratio slot nozzle with various V-gutter target thrust reversers

The results of experiments on the noise generated by a 1.33- by 91.4 cm slot nozzle with various V-gutter reversers, and some thrust measurements are presented. The experiments were conducted with near-ambient temperature jets at nozzle pressure ratios of 1.25 to 3.0, yielding jet velocities of about 190 to 400 m/sec. At pressure ratios of 2 or less, the reversers, in addition to being noisier than the nozzle alone, also had a more uniform directional distribution and more high-frequency noise. At pressure ratios above 2, the nozzle alone generated enough shock noise that the levels were about the same as for the reversers. The maximum overall sound pressure level and the effective overall sound power level both varied with the sixth power of jet velocity over the range tested. The data were scaled up to a size suitable for reversing the wing-flap slot nozzle flow of a 45 400-kg augmentor-wing-type airplane on the ground, yielding perceived noise levels well above 95 PNdB on a 152-m sideline.

Stone, J. R.↗