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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 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Effect of rotor design tip speed on noise of a 1.21 pressure ratio model fan under static conditions

Preliminary results are presented for a reverberant-field noise investigation of three fan stages designed for the same overall total pressure ratio of 1.21 at different rotor tip speeds (750, 900, and 1050 ft/sec). The stages were tested statically in a 15-inch-diameter model lift fan installed in a wing pod located in the test section of a wind tunnel. Although the fan stages produced essentially the same design pressure ratio, marked differences were observed in the variation of fan noise with fan operating speed. At design speed, the forward-radiated sound power level was approximately the same for the 750 ft/sec and 900 ft/sec stages. For the 1050 ft/sec stage, the design-speed forward-radiated power level was about 7 db higher due to the generation of multiple pure tone noise.

Loeffler, I. J.↗
NASA NTRS1977

An investigation of induced drag reduction through over-the-wing blowing

An investigation has been conducted in the Langley 16-foot transonic tunnel to verify analytically predicted benefits in climb and cruise performance due to blowing the jet exhaust over the wing for a transport configuration. A wing-body model - powered-nacelle rig combination was tested at Mach numbers of 0.5 and 0.8 at angles of attack from -2 to 4 deg and jet total pressure ratios from jet off to 3 or 4 (depending on Mach number) for a variety of nacelle locations relative to the wing. Results from this investigation show that the induced drag for the wing-body (nacelles were nonmetric) was reduced for virtually all configurations. In addition to the experimental results, comparisons of the data with available prediction methods are included to show their validity and capabilities.

Reubush, D. E.↗
NASA NTRS1983

Supersonic aerodynamic characteristics of a tail-control cruciform maneuverable missile with and without wings

The aerodynamic characteristics for a winged and wingless cruciform missile configuration were examined. The configuration had an ogive-cylinder body with a 3.5 caliber forebody; an overall length-to-diameter ratio of 11.667; and had cruciform tails that were trapezoidal in planform. Tests were made both with and without 72.9 degree cruciform delta wings. The investigation was made for Mach numbers from 1.50 to 4.63, roll attitudes of 0 degrees and 45 degrees, angles of attack from -4 degrees to 22 degrees, and tail control deflections from 10 degrees to -40 degrees.

Spearman, M. L.↗
NASA NTRS1977

Experimental evaluation of nacelle-airframe interference forces and pressures at Mach numbers of 0.9 to 1.4

Detailed interference force-and-pressure data were obtained on a representative supersonic transport wing-body-nacelle combination at Mach numbers of 0.9 to 1.4. The basic model consisted of a delta wing-body aerodynamic model with a length of 158.0 cm (62.2 in.) and a wingspan of 103.6 cm (40.8 in.) and four independently supported nacelles positioned beneath the model. The experimental program was conducted in the Ames 11- by 11-Foot Wind Tunnel at a constant unit Reynolds number. The primary variables examined included Mach number, angle of attack, nacelle position, and nacelle mass-flow ratio. Under the most favorable conditions, the net interference drag was equal to 50 percent the drag of four isolated nacelles at M = 1.4, 75 percent at M = 1.15, and 144 percent at M = 0.90. The overall interference effects were found to be rather constant over the operating angle-of-attack range of the configuration. The effects of mass-flow ratio on the interference pressure distributions were limited to the lip region of the nacelle and the local wing surface in the immediate vicinity of the nacelle lip. The net change in the measured interference forces resulting from variations in the nacelle mass-flow ratio were found to be quite small.

Bencze, D. P.↗
NASA NTRS1961

Loads Induced on a Flat-Plate Wing by an Air Jet Exhausting Perpendicularly through the Wing and Normal to a Free-Stream Flow of Mach Number 2.0

Measurements were made of loads induced on a flat-plate wing by an air jet exhausting perpendicularly through the wing and normal to the free-stream flow.The investigation was conducted at a free-stream Mach number of 2.0 and a Reynolds number per foot of 14.4 x 10(exp 6). An axially symmetric sonic nozzle and two supersonic nozzles were employed for the jets. The supersonic nozzles consisted of an axially symmetric nozzle with exit Mach number of 3.44 and a two-dimensional nozzle with exit Mach number of 1.76. The ratio of nozzle total pressure to free-stream static pressure was varied from 20 to 110. Negative loads were induced on the flat-plate wing by all the jets. As the nozzle pressure ratio was increased the magnitude of interference loads due to jet thrust decreased. The chordwise center-of-pressure location generally moved toward the nozzle center line as the pressure ratio was increased.

Janos, Joseph J.↗
DOE OSTI2016

Predicting the Macroscopic Fracture Energy of Epoxy Resins from Atomistic Molecular Simulations

Predicting the macroscopic fracture energy of highly crosslinked glassy polymers from atomistic simulations is challenging due to the size of the process zone being large in these systems. Here, we present a scale-bridging approach that links atomistic molecular dynamics simulations to macroscopic fracture properties on the basis of a continuum fracture mechanics model for two different epoxy materials. Our approach reveals that the fracture energy of epoxy resins strongly depends on the functionality of epoxy resin and the component ratio between the curing agent (amine) and epoxide. The most intriguing part of our study is that we demonstrate that the fracture energy exhibits a maximum value within the range of conversion degrees considered (from 65% to 95%), which can be attributed to the combined effects of structural rigidity and post-yield deformability. Our study provides physical insight into the molecular mechanisms that govern the fracture characteristics of epoxy resins and demonstrates the success of utilizing atomistic molecular simulations towards predicting macroscopic material properties.

42 ENGINEERING↗
NASA NTRS1974

Transonic flow about lifting wing-body combinations

Calculations for transonic flow about wing-body combinations at angles of attack of the order of the body thickness-to-length ratio are presented. These calculations show that lift can alter the flow drastically at near-sonic speeds in this angle-of-attack range so that the area rule must be modified. This effect of lift is explained from simple physical considerations. The computational procedure is based on slender-wing theory and a two-variable method of relaxation solution. A small perturbation analysis is used to show that this simple procedure is adequate for these transonic wing-body flow fields.

Barnwell, R. W.↗
NASA NTRS1981

Effectiveness of leading-edge vortex flaps on 60 and 75 degree delta wings

A series of wind tunnel tests were run on 60 and 75 deg sweep delta wings to examine the effectiveness of leading-edge vortex flaps. Tests results showed that leading-edge vortex flaps are effective in giving large increases in lift-to-drag ratio and decreases in drag over a wide range of angle of attack. Tests on inverted flaps on the 60 deg delta wing showed substantial increases in lift and drag and may indicate a possibility of using inverted flaps on delta wings in the landing portion of flight. The 60 deg data were compared with that for a 75 deg sweep delta wing confirming that leading-edge vortex flap effectiveness is stronger as sweep is increased. Pitching moment effects due to vortex flaps use were also examined.

Marchman, J. F., III↗
NASA NTRS1989

Variable-mixture-ratio and other rocket engines for advanced shuttles

Previous computer models of rocket engines and single-stage-to-orbit vehicles have been extended to include variable-mixture-ratio engines. The model has been applied to study a vertical-takeoff, horizontal-landing, winged, manned, fully-reusable vehicle with a payload of 13.6 Mg and which is launched to low-earth orbit. Both single-stage and two-stage vehicles are considered, with special attention given to hydrogen, methane, and propane engines with staged-combustion cycles. Results are presented for the optimum nozzle exit pressure, thrust split between the booster and orbiter, chamber pressure, and mixture ratio.

Martin, James A.↗
NASA NTRS1994

Wing design for a civil tiltrotor transport aircraft

The goal of this research is the proper tailoring of the civil tiltrotor's composite wing-box structure leading to a minimum-weight wing design. With focus on the structural design, the wing's aerodynamic shape and the rotor-pylon system are held fixed. The initial design requirement on drag reduction set the airfoil maximum thickness-to-chord ratio to 18 percent. The airfoil section is the scaled down version of the 23 percent-thick airfoil used in V-22's wing. With the project goal in mind, the research activities began with an investigation of the structural dynamic and aeroelastic characteristics of the tiltrotor configuration, and the identification of proper procedures to analyze and account for these characteristics in the wing design. This investigation led to a collection of more than thirty technical papers on the subject, some of which have been referenced here. The review of literature on the tiltrotor revealed the complexity of the system in terms of wing-rotor-pylon interactions. The aeroelastic instability or whirl flutter stemming from wing-rotor-pylon interactions is found to be the most critical mode of instability demanding careful consideration in the preliminary wing design. The placement of wing fundamental natural frequencies in bending and torsion relative to each other and relative to the rotor 1/rev frequencies is found to have a strong influence on the whirl flutter. The frequency placement guide based on a Bell Helicopter Textron study is used in the formulation of frequency constraints. The analysis and design studies are based on two different finite-element computer codes: (1) MSC/NASATRAN and (2) WIDOWAC. These programs are used in parallel with the motivation to eventually, upon necessary modifications and validation, use the simpler WIDOWAC code in the structural tailoring of the tiltrotor wing. Several test cases were studied for the preliminary comparison of the two codes. The results obtained so far indicate a good overall agreement between the two codes.

Rais-Rohani, Masoud↗
NASA NTRS1979

An experimental and theoretical investigation of the effect of nonmetric over-the-wing nacelles on wing-body aerodynamics

Drag reduction benefits due to blowing the jet exhausts over the wing for a transport-type wing-body configuration were investigated in the Langley 16-foot transonic tunnel. A combination of a wing-body model and a powered-nacelle test rig was tested at Mach numbers of 0.50 and 0.80 at angles of attack from -2 degrees to 4 degrees and jet total-pressure ratios from jet off to 3 or 4 (depending on Mach number) for a variety of nacelle locations relative to the wing. The experimental results were compared with the predictions obtained from several theoretical techniques. It was concluded that positioning of the nacelles (nonmetric) can have large effects on the wing-body drag. Some positions yielded higher drag than the baseline position, whereas others yielded lower drag than the baseline position. The theoretical method which utilized a quasi-vortex-lattice for the wing and wing-jet interaction in combination with a jet entrainment model gave generally reasonable predictions of the drag increments.

Reubush, D. E.↗
NASA NTRS1971

Space shuttle: Heat transfer rate measurements on Convair booster (B-15B-2) at nominal Mach number of 8

Plotted and tabulated data on heat transfer from a thin-skin thermocouple are presented. The data is representative of the reentry event of the booster alone configuration. The data were generated during wind tunnel tests of the B-15B-2 delta wing booster at Mach 8. Thermocouple measurements are reduced to heat transfer coefficient ratio and the data are presented as plotted variations versus longitudinal, lateral, and vertical local model positions.

Warmbrod, J. D.↗
NASA NTRS1981

A Jet-diffuser ejector for a V/STOL fighter

A single ejector equipped with only one vector control jet and a diffuser flap was installed close to the leading edge of the strake of a one-fifth scale, semi-span model of the aircraft, without wing, canard, or tail surface. Tests of the system at a nozzle pressure ratio of 1.24 indicated a thrust augmentation of 1.92 and a thrust in the flight direction of about 12% of the total thrust under static conditions. An ejector stall occured at a ratio of tunnel dynamic pressure to nozzle gage pressure of about 0.008. Ejector stall speed can be delayed by using a boundary layer control jet at the front inlet lip of the ejector.

Alperin, M.↗
NASA NTRS1991

Engineering method for aero-propulsive characteristics at hypersonic Mach numbers

An engineering method has been developed for the rapid analysis of external aerodynamics and propulsive performance characteristics of airbreathing vehicles at hypersonic Mach numbers. This method, based on the theory of characteristics, has been developed to analyze fuselage-wing body combinations and body flaps with blunt or sharp leading/trailing edges. Arbitrary ratio of specific heat for the flowing medium can be specified in the program. Furthermore, the capability exists in the code to compute the inviscid inlet mass capture and momentum flux. The method is under development for computations of pressure distribution, and flow characteristics in the inlet, along with the effect of viscosity. Correlative studies have been performed for representative hypersonic configurations using the current method. The results of these correlations for various aerodynamics parameters are encouraging.

Goradia, Suresh↗
NASA NTRS1985

Comparison of advanced turboprop installation on swept and unswept supercritical wings at transonic speeds

A series of wind-tunnel investigations were conducted to determine the aerodynamic interference associated with the over wing and under wing installation of a turboprop nacelle on 20 deg swept and unswept supercritical wings. The purpose of the investigations was to increase the understanding of the flow interactions involved with the nacelle turboprop integration and to obtain experimental data for the verification of computational prediction techniques. The models were tested in the Langley 16-Foot Transonic Tunnel at Mach numbers from 0.50 to 0.80 and at angles-of-attack from 0 to 5 deg. In addition, data at several propeller pitch angles and advance ratio settings were obtained. This paper which presents only the results of the over-the-wing nacelle installations shows that wing sweep had considerable influence on the installation interference. Large scale flow separation was observed on the swept wing at M = 0.8. Less severe effects were observed at M = 0.7 on the swept wing and for both M = 0.7 and 0.8 on the unswept wing.

Carlson, J. R.↗
NASA NTRS2013

A Mission-Adaptive Variable Camber Flap Control System to Optimize High Lift and Cruise Lift-to-Drag Ratios of Future N+3 Transport Aircraft

Boeing and NASA are conducting a joint study program to design a wing flap system that will provide mission-adaptive lift and drag performance for future transport aircraft having light-weight, flexible wings. This Variable Camber Continuous Trailing Edge Flap (VCCTEF) system offers a lighter-weight lift control system having two performance objectives: (1) an efficient high lift capability for take-off and landing, and (2) reduction in cruise drag through control of the twist shape of the flexible wing. This control system during cruise will command varying flap settings along the span of the wing in order to establish an optimum wing twist for the current gross weight and cruise flight condition, and continue to change the wing twist as the aircraft changes gross weight and cruise conditions for each mission segment. Design weight of the flap control system is being minimized through use of light-weight shape memory alloy (SMA) actuation augmented with electric actuators. The VCCTEF program is developing better lift and drag performance of flexible wing transports with the further benefits of lighter-weight actuation and less drag using the variable camber shape of the flap.

Mission-Adaptive Wing↗
NASA NTRS1980

On the stability of three-dimensional compressible nonparallel boundary layers

A compressible linear stability theory is presented for three-dimensional nonuniform boundary layers. The amplitude, phase, and wavenumber equations which govern the motion of the disturbance are obtained by using the method of multiple scales. Group velocity trajectories are used to identify the disturbance growth direction. The spatial stability theory is applied to the flow on a laminar flow control supercritical sweptback wing of infinite span. Three different methods are used to calculate the absolute maximum logarithmic amplitude ratio N. In the front crossflow instability region, the method of maximum spatial growth rate predicts large difference in N compared with the method of fixed wavelength and the method of fixed spanwise component of wavelength. This difference decreases in the middle streamwise instability region, and almost vanishes in the rear crossflow instability region. Compressibility of the medium reduces N by about 15% in both the front and rear regions, and by about 40% in the middle region of the wing. Nonuniformity of the medium has large effects specially in the rear region.

El-Hady, N. M.↗