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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Non-propulsive aerodynamic noise

In the first part of the paper, the contribution of airframe noise to total aircraft noise on approach is assessed for a large current technology transport and for the same airframe powered with bypass ratio 10 engines with an additional 5 dB noise suppression applied to the fan and turbine noise sources. The airframe noise of the envisioned advanced subsonic transport is 2 EPNdB less than the largest contributor to the total aircraft noise, the fan inlet. The noise impact of the airframe noise, as measured by noise contour area, is 1/4 that of fan noise. Further fan noise reduction efforts should not view airframe noise as an absolute noise floor. In the second part of the paper, the results from one recent cavity noise wind tunnel experiment is reported. A cavity of dimensions 11.25 in. (28.58 cm) long, 2.5 in. (6.35 cm) wide, and variable depth was tested in the Mach number range of .20 through .90. Reynolds number varied from 5 to 100 million per foot (16 to 328 million per meter). The 1/d ratio was varied from 4.4 to 20.0. The model was tested at yaw angles from 0 to 15 degrees. In general, the deeper the cavity, the greater the amplitude of the acoustic tones. Reynolds number appeared to have little effect on acoustic tone amplitudes. Tone amplitude and bandwidth changed with Mach number. The effect of yaw on acoustic tones varied with Reynolds number, Mach number, 1/h, and mode number. At Mach number 0.90, increased yaw shifted the tone frequencies of the higher modal frequencies to lower frequencies. As cavity depth decreased, the effect of yaw decreased.

Willshire, William L., Jr.↗
NASA NTRS1981

A theoretical approach to sound propagation and radiation for ducts with suppressors

The several phenomena involved in theoretical prediction of the far-field sound radiation attenuation from an acoustically lined duct were studied. These include absorption by the suppressor, termination reflections, and far-field radiation. Extensive parametric studies show that the suppressor absorption performance can be correlated with mode cut-off ratio or angle of propagation. The other phenomena can be shown to depend explicitly upon mode cut-off ratio. A complete system can thus be generated which can be used to evaluate aircraft sound suppressors and which can be related to the sound source through the cut-off ratio-acoustic power distribution. Although the method is most fully developed for inlet suppressors, several aft radiated noise phenomena are also discussed. This simplified suppressor design and evaluation method is summarized, the recent improvements in the technique are presented, and areas where further refinement is necessary are discussed. Noise suppressor data from engine experiments are compared with the theoretical calculations.

Rice, E. J.↗
NASA NTRS1981

A theoretical approach to sound propagation and radiation for ducts with suppressors

The several phenomena involved in theoretical prediction of the far-field sound radiation attenuation from an acoustically lined duct have been studied. These include absorption by the suppressor, termination reflection, and far-field radiation. Extensive parameteric studies have shown that the suppressor absorption performance can be correlated with mode cut-off ratio or angle of propagation. The other phenomena can be shown to depend explicitly upon mode cut-off ratio. A complete system can thus be generated which can be used to evaluate aircraft sound suppressors and which can be related to the sound source through the cut-off ratio-acoustic power distribution. Although the method is most fully developed for inlet suppressors, several aft radiated noise phenomena will also be discussed. This paper summarized this simplified suppressor design and evaluation method, presents the recent improvements in the technique and discusses areas where further refinement is necessary. Noise suppressor data from engine experiments are compared with the theoretical calculations.

Rice, E. J.↗
NASA NTRS1983

Predicting Aircraft Noise Levels

Computer program developed for predicting aircraft noise levels either in flight or in ground tests. Noise sources include fan inlet and exhaust jet flap (for powered lift), core (combustor), turbine and airframe. Program written in FORTRAN IV.

Clark, B. J.↗
NASA NTRS1972

On the role of the radiation directivity in noise reduction for STOL aircraft.

The radiation characteristics of distributed randomly fluctuating acoustic sources when shielded by finite surfaces are discussed briefly. A number of model tests using loudspeakers as artificial noise sources with a given broadband power density spectrum are used to demonstrate the effectiveness of reducing the radiated noise intensity in certain directions due to shielding. In the lateral direction of the source array noise reductions of 12 dB are observed with relatively small shields. The same shields reduce the backward radiation by approximately 20 dB. With the results obtained in these acoustic model tests the potentials of jet noise reduction of jet flap propulsion systems applicable in future STOL aircraft are discussed. The jet flap configuration as a complex aerodynamic noise source is described briefly.

Gruschka, H. D.↗
NASA NTRS2016

Acoustic Study of a Sweeping Jet Actuator for Active Flow Control Applications

Active flow control for aircraft has been demonstrated to improve aerodynamic performance but generally introduces additional noise sources. This study presents measurements of the acoustic fields of sweeping jet actuators at full- and half-scale compared to the configuration recently demonstrated in ground- and flight-tests of a full-scale rudder. The effects of scale, flow rate, forward speed, and actuator synchronization state on tone and broadband noise directional power spectral density (PSD) levels are presented. The sweeping jet actuator PSD levels in the audio range increases as the second power of actuator flow rate. A fourth power variation of PSD level with flow rate is observed for a comparable non-sweeping actuator. These measurements will be used to develop noise source models for new aircraft configurations utilizing active flow control.

Active Flow Control Noise↗
NASA NTRS1981

Computer program to predict aircraft noise levels

Methods developed at the NASA Lewis Research Center for predicting the noise contributions from various aircraft noise sources were programmed to predict aircraft noise levels either in flight or in ground tests. The noise sources include fan inlet and exhaust, jet, flap (for powered lift), core (combustor), turbine, and airframe. Noise propagation corrections are available for atmospheric attenuation, ground reflections, extra ground attenuation, and shielding. Outputs can include spectra, overall sound pressure level, perceived noise level, tone-weighted perceived noise level, and effective perceived noise level at locations specified by the user. Footprint contour coordinates and approximate footprint areas can also be calculated. Inputs and outputs can be in either System International or U.S. customary units. The subroutines for each noise source and propagation correction are described. A complete listing is given.

Clark, B. J.↗
NASA NTRS2018

A Review of Distributed Electric Propulsion Concepts for Air Vehicle Technology

The emergence of distributed electric propulsion (DEP) concepts for aircraft systems has enabled new capabilities in the overall efficiency, capabilities, and robustness of future air vehicles. Distributed electric propulsion systems feature the novel approach of utilizing electrically-driven propulsors which are only connected electrically to energy sources or power-generating devices. As a result, propulsors can be placed, sized, and operated with greater flexibility to leverage the synergistic benefits of aero-propulsive coupling and provide improved performance over more traditional designs. A number of conventional aircraft concepts that utilize distributed electric propulsion have been developed, along with various short and vertical takeoff and landing platforms. Careful integration of electrically-driven propulsors for boundary-layer ingestion can allow for improved propulsive efficiency and wake-filling benefits. The placement and configuration of propulsors can also be used to mitigate the trailing vortex system of a lifting surface or leverage increases in dynamic pressure across blown surfaces for increased lift performance. Additionally, the thrust stream of distributed electric propulsors can be utilized to enable new capabilities in vehicle control, including reducing requirements for traditional control surfaces and increasing tolerance of the vehicle control system to engine-out or propulsor-out scenarios. If one or more turboelectric generators and multiple electric fans are used, the increased effective bypass ratio of the whole propulsion system can also enable lower community noise during takeoff and landing segments of flight and higher propulsive efficiency at all conditions. Furthermore, the small propulsors of a DEP system can be installed to leverage an acoustic shielding effect by the airframe, which can further reduce noise signatures. The rapid growth in flight-weight electrical systems and power architectures has provided new enabling technologies for future DEP concepts, which provide flexible operational capabilities far beyond those of current systems. While a number of integration challenges exist, DEP is a disruptive concept that can lead to unprecedented improvements in future aircraft designs.

electric propulsion↗
NASA NTRSDate not supplied

Subsonic Single Aft Engine (SUSAN) Transport Aircraft Concept and Trade Space Exploration

A trade space exploration of a new NASA regional transport aircraft concept called the SUbsonic Single Aft eNgine (SUSAN) Electrofan is presented. The SUSAN concept uses a 20MW Electrified Aircraft Propulsion (EAP) system to enable advance Propulsion Airframe Integration (PAI) in transport category aircraft. Alternative fuels will be used to reduce the amount of emissions per energy used. By combining these features there is the potential to reduce aircraft emissions by 50% per passenger/mile while retaining the size, speed, and range of large regional jets. SUSAN is has a 750 mile economic mission, a 2500 mile design range and a maximum capacity of 180 passengers. The SUSAN configuration utilizes a single aft mounted engine and distributed electric wing-mounted thrusters on a tube and wing arrangement with a T-tail empennage. The SUSAN Electrofan employs a hybrid powertrain to enable: single turbofan operation on a large transport category aircraft; increased aerodynamic and propulsive efficiency through placement of electric engines; optimized turbofan sizing and efficiency through control and electric boosting, reduced control surface sizing through thrust augmentation. A single use battery is employed as the power source in case of turbofan failure. The design study also considers the constraints of operating within the current airport, airspace and economic constraints. This paper presents the status of the trade space exploration; however the concept definition is not finished. Forward work includes optimizing the overall aircraft configuration and including certain hard to model features like boundary layer ingestion or natural laminar flow across all appliable subsystems. Additional work forward work is a more extensive analysis of the configuration using alternative fuels.

Ralph H. Jansen↗
NASA NTRSDate not supplied

Refined Predictions Compared with the Propulsion Airframe Aeroacoustics and Aircraft System Noise Flight Research Test Data

In a collaboration between NASA and The Boeing Company, the Propulsion Airframe Aeroacoustics and Aircraft System Noise Flight Research Test was executed by the Boeing ecoDemonstrator Program in 2020 with an Etihad Airways Boeing 787-10 aircraft. This ambitious flight research successfully accomplished many objectives and constitutes the most comprehensive and highest quality acoustic flight data available to NASA for a modern commercial subsonic transport aircraft. One purpose of these data is to be the measure of accuracy for the aircraft system noise prediction capabilities of NASA. This research reviews the impact of the major improvements in prediction methods implemented up to this point and tested in the Research version of the NASA Aircraft Noise Prediction Program. The improvements have been to the prediction of jet source and jet-flap interaction, to both fan broadband and tone source prediction, and to the prediction of propulsion airframe aeroacoustic scattering effects. In general, over the engine power range, comparisons between prediction and flight data are within 2 EPNdB including for the intentional sideline-to-sideline asymmetries as implemented in the flight test by flying the aircraft with only one engine at power. Considerable progress has been shown here in the continuing effort to advance the fidelity of NASA aircraft noise prediction capabilities for subsonic aircraft flight acoustics, modern transport aircraft and future aircraft concepts.

aircraft system noise prediction↗
NASA NTRS2007

Solar Airplanes and Regenerative Fuel Cells

A solar electric aircraft with the potential to "fly forever" has captured NASA's interest, and the concept for such an aircraft was pursued under Aeronautics Environmental Research Aircraft and Sensor Technology (ERAST) project. Feasibility of this aircraft happens to depend on the successful development of solar power technologies critical to NASA's Exploration Initiatives; hence, there was widespread interest throughout NASA to bring these technologies to a flight demonstration. The most critical is an energy storage system to sustain mission power during night periods. For the solar airplane, whose flight capability is already limited by the diffuse nature of solar flux and subject to latitude and time of year constraints, the feasibility of long endurance flight depends on a storage density figure of merit better than 400-600 watt-hr per kilogram. This figure of merit is beyond the capability of present day storage technologies (other than nuclear) but may be achievable in the hydrogen-oxygen regenerative fuel cell (RFC). This potential has led NASA to undertake the practical development of a hydrogen-oxygen regenerative fuel cell, initially as solar energy storage for a high altitude UAV science platform but eventually to serve as the primary power source for NASAs lunar base and other planet surface installations. Potentially the highest storage capacity and lowest weight of any non-nuclear device, a flight-weight RFC aboard a solar-electric aircraft that is flown continuously through several successive day-night cycles will provide the most convincing demonstration that this technology's widespread potential has been realized. In 1998 NASA began development of a closed cycle hydrogen oxygen PEM RFC under the Aeronautics Environmental Research Aircraft and Sensor Technology (ERAST) project and continued its development, originally for a solar electric airplane flight, through FY2005 under the Low Emissions Alternative Power (LEAP) project. Construction of the closed loop system began in 2002 at the NASA Glenn Research Center in Cleveland, Ohio. System checkout was completed, and testing began, in July of 2003. The initial test sequences were done with only a fuel cell or electrolyzer in the test rig. Those tests were used to verify the test apparatus, procedures, and software. The first complete cycles of the fully closed loop, regenerative fuel cell system were successfully completed in the following September. Following some hardware upgrades to increase reactant recirculation flow, the test rig was operated at full power in December 2003 and again in January 2004. In March 2004 a newer generation of fuel cell and electrolyzer stacks was substituted for the original hardware and these stacks were successfully tested at full power under cyclic operation in June of 2004.

Bents, David J.↗
NASA NTRS1973

Comparison of aircraft noise measured in flight test and in the NASA Ames 40- by 80-foot wind tunnel.

A method to determine free-field aircraft noise spectra from wind-tunnel measurements has been developed. The crux of the method is the correction for reverberations. Calibrated loud speakers are used to simulate model sound sources in the wind tunnel. Corrections based on the difference between the direct and reverberant field levels are applied to wind-tunnel data for a wide range of aircraft noise sources. To establish the validity of the correction method, two research aircraft - one propeller-driven (YOV-10A) and one turbojet-powered (XV-5B) - were flown in free field and then tested in the wind tunnel. Corrected noise spectra from the two environments agree closely.

Atencio, A., Jr.↗
NASA NTRS1980

Infrared heterodyne radiometer for airborne atmospheric transmittance measurements

An infrared heterodyne radiometer (IHR) was used to measure atmospheric transmittance at selected hydrogen fluoride (2.7 micrometer) and deuterium fluoride (3.8 micrometer) laser transitions. The IHR was installed aboard a KC-135 aircraft for an airborne atmospheric measurements program that used the sun as a backlighting source for the transmission measurements. The critical components are: a wideband indium antimonide (1nSb) photomixer, a CW HF/DF laser L0, a radiometric processor, and a 1900 K blackbody reference source. The measured heterodyne receiver sensitivity (NEP) is 1.3 x 10 to the -19th power W/Hz, which yields a calculated IHR temperature resolution accuracy of delta I sub S/-3 sub S = 0.005 for a source temperature of 1000 K and a total transmittance of 0.5. Measured atmospheric transmittance at several wavelengths and aircraft altitudes from 9.14 km (30,000 ft) to 13.72 km (45,000 ft) were obtained during the measurements program and have been compared with values predicted by the AFGL Atmospheric Line Parameter Compilation.

Wolczok, J. M.↗
NASA NTRS1972

Optimization of fluid line sizes with pumping power penalty IBM-360 computer program

Computer program has been developed to calculate and total weights for tubing, fluid in tubing, and weight of fuel cell power source necessary to power pump based on flow rate and pressure drop. Program can be used for fluid systems used in any type of aircraft, spacecraft, trucks, ships, refineries, and chemical processing plants.

Jelinek, D.↗
NASA NTRS1988

The prediction of en route noise levels for a DC-9 aircraft

En route noise for advanced propfan powered aircraft has become an issue of concern for the Federal Aviation Administration. The NASA Aircraft Noise Prediction Program (ANOPP) is used to demonstrate the source noise and propagation effects for an aircraft in level flight up to 35,000 feet altitude. One-third octave band spectra of the source noise, atmospheric absorption loss, and received noise are presented. The predicted maximum A-weighted sound pressure level is compared to measured data from the Aeronautical Research Institute of Sweden. ANOPP is shown to be an effective tool in evaluating the en route noise characteristics of a DC-9 aircraft.

Weir, Donald S.↗
NASA NTRS1947

A Preliminary Study of Ram-Actuated Cooling Systems for Supersonic Aircraft

An analysis has been made of the characteristics of several cooling cycles suitable for cockpit cooling of supersonic aircraft. All the cycles considered utilize the difference between dynamic and ambient static pressure to actuate the cooling system and require no additional power source. The results of the study indicate that as flight speeds become greater, increasingly complex systems are required to reduce the altitudes above approximately 35,000 feet, a system composed of an externally loaded expansion turbine in conjunction with a supersonic diffuser would maintain tolerable ventilating air temperature, at least up to a flight Mach number of 2. The most complex system considered,composed of compressor, intercooler, and expansion turbine with the intercooler cooling air decreased in temperature by expansion through an auxiliary turbine is capable of maintaining a ventilation air temperature less than ambient temperature up to a flight Mach number of 3.7.

Stalder, Jackson R.↗
NASA NTRS2017

Implementation of a Battery Health Monitor and Vertical Lift Aircraft Testbed for the Application of an Electrochemisty-Based State of Charge Estimator

Prediction methods concerning remaining charge in lithium-ion batteries that power unmanned aerial vehicles are of critical concern for the safe fulfillment of mission objectives. In recent years, lithium-ion batteries have been the power source for both fixed wing and vertical lift electric vehicles. The purpose of this document is to describe in detail the implementation of a battery health monitor for estimating the state of charge of a lithium-ion battery and a lithium-ion polymer battery that is used to power a vertical lift aircraft test-bed. It will be demonstrated that an electro-chemistry based state of charge estimator effectively tracks battery discharge characteristics and may be employed as a useful tool in monitoring battery health.

Potteiger, Timothy R.↗