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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 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Comparison of axisymmetric and nonaxisymmetric nozzles installed on the F-15 configuration

An investigation has been conducted in the Langley 16-foot transonic tunnel to determine nozzle/afterbody performance of nonaxisymmetric nozzles installed in a 1/12-scale F-15 propulsion model. Tests were performed at Mach numbers from 0.60 to 1.20 at angles-of-attack from -2 to +9 deg and jet-total-pressure ratios from 1.0 (jet-off) to 5.0, depending on Mach number. The baseline F-15 afterbody was tested with axisymmetric nozzles, and two different two-dimensional wedge nozzle afterbody designs. Results of this investigation indicate that one of the two-dimensional afterbody designs had lower drag than the baseline at a Mach number of 1.20, and about the same drag for subsonic Mach numbers at scheduled nozzle pressure ratios. Thrust vectoring of the two-dimensional wedge nozzles produced significant induced lift on the afterbody and horizontal tails, while thrust reversing had little effect on horizontal tail effectiveness.

Pendergraft, O. C., Jr.↗
NASA NTRS1977

Two-dimensional nozzle/airframe integration technology - An overview

The paper reviews the objectives and some of the accomplishments of a number of programs to develop nonaxisymmetric nozzle technology for future tactical aircraft applications. Specific existing fighter aircraft model tests and preliminary studies are discussed which are designed to generate installed nozzle data, including the effects of thrust vectoring and reversal.

Richey, G. K.↗
NASA NTRS1977

Nonaxisymmetric nozzle technology program - An overview

Nonaxisymmetric nozzles, with in-flight thrust vectoring and/or reversing capabilities, provide the potential for substantial gains in fighter aircraft performance, maneuvering, survivability and ground handling. This paper presents an overview of some of the current programs to develop nonaxisymmetric nozzle technology for future aircraft applications. The initial phase of this program, which consists of a series of subscale model tests, engine/nozzle studies, system integration studies and simulation studies, has been initiated. Successful completion of this program will allow designers of future aircraft to consider, with high confidence, the integration of nonaxisymmetric nozzle concepts to improve aircraft mission performance effectiveness, survivability and cost.

Berrier, B. L.↗
NASA NTRS1977

Forward speed effects on blown flap noise

The effects of forward speed on the noise of under-the-wing (externally blown flaps, EBF) and over-the-wing (upper surface blown, USB) blown flap configurations were measured in wind tunnel model tests with cold jets. The results are presented without correction for the effects (e.g., signal convection, shear layer refraction) associated with flight simulation in a wind tunnel or free jet facility. Noise decreases were generally observed at microphones forward of the wing. The reductions were larger at the low frequencies (below peak SPL) than at the high (above peak SPL). Noise increases of 10 dB or more were observed at the aft microphones, especially in the high frequency range.

Pennock, A. P.↗
NASA NTRS1978

Subminiature hydraulic actuator

Subminiature, single-vane rotary actuator for wind-tunnel test-model control-surface actuation systems presents severe torque and system band-pass requirements with stringent space and weight limitations. Actuator has very low leakage of fluid from one side to other, permitting use in precision position servo-systems.

Sevart, F. D.↗
NASA NTRS1977

Aircraft Lightning Attachment Phenomena

An aircraft's influence on lightning-strike occurrence was investigated. The compression of an electric field around an aircraft was considered in mathematical calculations of an aircraft's ability to store charge. Model test results were used to predict lightning-strike attachment zones in an analysis of aircraft design.

Franklin A Fisher↗
NASA NTRS1977

Foster-Miller's development of dry coal feed systems

Dry coal feeder systems developed for pressurized conversion processes were carried through a laboratory scale development program. These concepts include: (1) a centrifugal solids feeder; (2) a fluidized piston feeder; (3) a linear pocket feeder; and (4) a compacted coal plug feeder. Results of laboratory model testing of all concepts are reviewed.

Harding, J. C.↗
NASA NTRS1978

Comparison of blade loads of fixed and free yawing wind turbine

The self regulating composite bearingless wind turbine utilizes an automatic pitch control concept and a completely unrestrained yawing degree of freedom. Aerodynamic moments caused by skewed flow provide the control to align the wind turbine with the wind. Model tests demonstrated the feasibility of the concept and analytical studies showed the free system to experience lower blade loads compared to the fixed system.

Cheney, M. C.↗
NASA NTRS1978

Heliogyro Preliminary Design, Phase 2

There are 12 blades in the Heliogyro design, and each blade is envisioned to be 8 meters in width and 7,500 meters in length. The blades are expected to be composed primarily of a thin membrane constructed of material such as Kapton film with an aluminum reflective coating on one side and an infrared emissive coating on the other. The present Phase 2 Final Report covers work done on the following six topics: (1) Design and analysis of a stowable circular lattice batten for the Heliogyro blade. (2) Design and analysis of a biaxially tensioned blade panel. (3) Definition of a research program for micrometeoroid damage to tendons. (4) A conceptual design for a flight test model of the Heliogyro. (5) Definition of modifications to the NASTRAN computer program required to provide improved analysis of the Heliogyro. (6) A User's Manual covering applications of NASTRAN to the Heliogyro.

Source record↗
NASA NTRS1978

Aerodynamic characteristics of a counter-rotating, coaxial, hingeless rotor helicopter model with auxiliary propulsion

A wind-tunnel model test at advance ratios from 0 to 0.3 with and without auxiliary jet engine thrust is reported. At each advance ratio and engine thrust, both the control power and the aircraft stability were measured. The results indicate that there is a cross-coupling for collective pitch and longitudinal cyclic pitch inputs. The control power for these inputs increased with advance ratio. There was also cross-coupling for differential collective pitch inputs. The airframe was longitudinally unstable, but the instability was less at the highest advance ratio tested. The airframe showed both positive effective dihedral and positive directional stability.

Phelps, A. E., III↗
NASA NTRS1978

Simulation and flight evaluation of a head-up landing aid for general aviation

A head-up general aviation landing aid called a landing site indicator (LASI) was tested in a fixed-base, visual simulator and in an airplane to determine the effectiveness of the LASI. The display, which had a simplified format and method of implementation, presented to the pilot in his line of sight through the windshield a graphic representation of the airplane's velocity vector. In each testing model (simulation of flight), each of 4 pilots made 20 landing approaches with the LASI and 20 approaches without it. The standard deviations of approach and touchdown parameters were considered an indication of pilot consistency. Use of the LASI improved consistency and also reduced elevator, aileron, and rudder control activity. Pilots' comments indicated that the LASI reduced work load. An appendix is included with a discussion of the simulator effectiveness for visual flight tasks.

Harris, R. L., Sr.↗
NASA NTRS1978

A distribution model for the aerial application of granular agricultural particles

A model is developed to predict the shape of the distribution of granular agricultural particles applied by aircraft. The particle is assumed to have a random size and shape and the model includes the effect of air resistance, distributor geometry and aircraft wake. General requirements for the maintenance of similarity of the distribution for scale model tests are derived and are addressed to the problem of a nongeneral drag law. It is shown that if the mean and variance of the particle diameter and density are scaled according to the scaling laws governing the system, the shape of the distribution will be preserved. Distributions are calculated numerically and show the effect of a random initial lateral position, particle size and drag coefficient. A listing of the computer code is included.

Fernandes, S. T.↗
NASA NTRS1978

Preliminary comparison of model and prototype wakes

Velocity and turbulence profiles previously measured in the wake of a long building 3.2 m high, located in the field, transverse to the wind and in an atmospheric boundary layer several hundred meters thick are compared with wake profiles at corresponding longitudinal stations for a scale model of the building located in a large meteorological wind tunnel having a boundary layer thickness of 0.61 m to assess the accuracy of full scale wake profile predictions based on model tests. Results are presented which show that disparities in nondimensional profiles result from differences in relative depth of logarithmic layers and in surface conditions.

Logan, E., Jr.↗
NASA NTRS1978

A simplified Mach number scaling law for helicopter rotor noise

Mach number scaling laws are derived for the rotational and the high-frequency broadband noise from helicopter rotors. The rotational scaling law is obtained directly from the theory of Lowson and Ollerhead (1969) by exploiting the properties of the dominant terms in the expression for the complex Fourier coefficients of sound radiation from a point source. The scaling law for the high-frequency broadband noise is obtained by assuming that the noise sources are acoustically compact and computing the instantaneous pressure due to an element on an airfoil where vortices are shed. Experimental results on the correlation lengths for stationary airfoils are extended to rotating airfoils. On the assumption that the correlation length varies as the boundary layer displacement thickness, it is found that the Mach number scaling law contains a factor of Mach number raised to the exponent 5.8. Both scaling laws were verified by model tests.

Aravamudan, K. S.↗
NASA NTRS1978

An evaluation of several compressible turbulent boundary-layer models Effects of pressure gradient and Reynolds number

Computations, employing several turbulence models, are compared with a series of attached supersonic turbulent boundary-layer experiments over an extensive range of Reynolds numbers (11.7 x 10 to the 6th to 314 x 10 to the 6th). These experiments included measurements of surface pressure and skin friction for adverse pressure gradients ranging in magnitude from those of previous investigations to an order of magnitude greater. The turbulence models evaluated include algebraic and two-equation eddy-viscosity models and two full Reynolds stress models. In general all the models tested performed well independently of the magnitude of the pressure gradient or Reynolds number and could predict the measured skin friction for most cases with sufficient accuracy for engineering purposes.

Horstman, C. C.↗
NASA NTRS1978

Interactions of simultaneous perturbations of stratospheric photochemistry

The combined effects of two specific ozone perturbation mechanisms are examined. The need to look back to predictions of the near past as well as the future as a means of testing model results is emphasized. The two perturbations examined are that due to chlorofluoromethane (CFM) release and that due to the air pollutants CO and nitrogen oxide. A steady-state model is used to investigate the characteristics of the stratospheric-tropospheric photochemical system for differing levels of CO and nitrogen oxide fluxes at the ground and for simultaneously changing the stratospheric from CFM release. Two basic scenarios chosen to illustrate the competing effects of the two types of perturbation use the time-dependence for chlorine radical buildup calculated for constant continued release of CFM's.

Butler, D. M.↗
NASA NTRS1979

Experimental study of coaxial nozzle exhaust noise

Experimental results are presented for static acoustic model tests of various geometrical configurations of coaxial nozzles operating over a range of flow conditions. The geometrical configurations consisted of nozzles with coplanar and non-coplanar exit planes and various exhaust area ratios. Primary and secondary nozzle flows were varied independently over a range of nozzle pressure ratios from 1.4 to 3.0 and gas temperatures from 280 to 1100 K. Acoustic data are presented for the conventional mode of coaxial nozzle operation as well as for the inverted velocity profile mode. Comparisons are presented to show the effect of configuration and flow changes on the acoustic characteristics of the nozzles.

Goodykoontz, J. H.↗
NASA NTRS1979

Preliminary noise tradeoff study of a Mach 2.7 cruise aircraft

NASA computer codes in the areas of preliminary sizing and enroute performance, takeoff and landing performance, aircraft noise prediction, and economics were used in a preliminary noise tradeoff study for a Mach 2.7 design supersonic cruise concept. Aerodynamic configuration data were based on wind-tunnel model tests and related analyses. Aircraft structural characteristics and weight were based on advanced structural design methodologies, assuming conventional titanium technology. The most advanced noise prediction techniques available were used, and aircraft operating costs were estimated using accepted industry methods. The 4-engines cycles included in the study were based on assumed 1985 technology levels. Propulsion data was provided by aircraft manufacturers. Additional empirical data is needed to define both noise reduction features and other operating characteristics of all engine cycles under study. Data on VCE design parameters, coannular nozzle inverted flow noise reduction and advanced mechanical suppressors are urgently needed to reduce the present uncertainties in studies of this type.

Mascitti, V. R.↗