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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 1,009 records · Page 56

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NASA NTRS1946

Possibilities for drag reduction by boundary layer control

The mechanics of laminar boundary layer transition are reviewed. Drag possibilities for boundary layer control are analyzed using assumed conditions of transition Reynolds number, inlet loss, number of slots, blower efficiency, and duct losses. Although the results of such analysis are highly favorable, those obtained by experimental investigations yield conflicting results, showing only small gains, and sometimes losses. Reduction of this data indicates that there is a lower limit to the quantity of air which must be removed at the slot in order to stabilize the laminar flow. The removal of insufficient air permits transition to occur while the removal of excessive amounts of air results in high power costs, with a net drag increases. With the estimated value of flow coefficient and duct losses equal to half the dynamic pressure, drag reductions of 50% may be obtained; with twice this flow coefficient, the drag saving is reduced to 25%.

Naiman, I.↗

NASA NTRS1978

A method for calculating externally blown flap noise

Several basic noise components were described. These components are: (1) compact lift dipoles associated with the wing and flaps; (2) trailing edge noise associated with the last trailing edge; and (3) quadrupole noise associated with the undeflected exhaust jet and the free jet located downstream of the trailing edge. These noise components were combined to allow prediction of directivity and spectra for under the wing (UTW) slotted flaps with conventional or mixer nozzles, UTW slotless flaps, upper surface blowing (USB) slotless flaps, and engine in front of the wing slotted flaps. A digital computer program listing was given for this calculation method. Directivities and spectra calculated by this method were compared with free field data for UTW and USB configurations. The UTRC method best predicted the details of the measured noise emission, but the ANOP method best estimated the noise levels directly below these configurations.

Fink, M. R.↗

NASA NTRS1978

Stator rotor tools

An apparatus and method for removing and reinserting base member segments in an arcuate slot in an engine part are described. Each base member separately includes blades or stators, holding the engine part in place while manipulating fingers or an arm onto an interfitting abutting relationship with most of the blades. A torque force is applied to the base of the blades to move a base member relative to such an arcuate slot.

Diamond, D. D.↗

NASA NTRS1978

A study of test section configuration for shock tube testing of transonic airfoils

Two methods are investigated for alleviating wall interference effects in a shock tube test section intended for testing two-dimensional transonic airfoils. The first method involves contouring the test section walls to match approximate streamlines in the flow. Contours are matched to each airfoil tested to produce results close to those obtained in a conventional wind tunnel. Data from a previous study and the present study for two different airfoils demonstrate that useful results are obtained in a shock tube using a test section with contoured walls. The second method involves use of a fixed-geometry slotted-wall test section to provide automatic flow compensation for various airfoils. The slotted-wall test section developed exhibited the desired performance characteristics in the approximate Mach number range 0.82 to 0.89, as evidenced by good agreement obtained between shock tube and wind tunnel results for several airfoil flows.

Cook, W. J.↗

NASA NTRS1978

Moving ground simulation by tangential blowing

Belt-type moving ground equipment, used for ground-effect simulation in STOL and VTOL tests, can be inconvenient and costly, especially in larger tunnels. In most cases such difficulties may be avoided by employing tangential blowing at the ground surface, from a single slot. The paper reviews several powered model tests using both moving ground and tangential blowing and describes the slot configuration, and the test techniques which were developed. Ground skin friction is monitored to set blowing levels and no model-dependent calculations are needed. It is also shown that application to center-tunnel testing can delay tunnel flow breakdown very considerably.

Hackett, J. E.↗

NASA NTRS1979

Study of the application of superplastically formed and diffusion bonded (SPF/DB) titanium structure to laminar flow control (LFC) wing design

Eighteen design concepts for a LFC wing cover, using various SPF/DB approaches, were developed. After evaluation of producibility, compatibility with LFC requirements, structural efficiency and fatigue requirements, three candidates were selected for fabrication of demonstration panels. Included were both sandwich and stiffened semi-sandwich panels with slotted and perforated surfaces. Subsequent to the evaluation of the three demonstration panels, one concept was selected for fabrication of a 0.3 x 1.0 meter (12 x 42 inch) feasibility panel. It was a stiffened, semi-sandwich panel with a slotted surface, designed to meet the requirements of the upper wing cover at the maximum wing bending moment of the baseline configuration.

Mcquilkin, F. T.↗

NASA NTRS1979

Aircraft energy efficiency laminar flow control glove flight conceptual design study

A laminar flow control glove applied to the wing of a short to medium range jet transport with aft mounted engines was designed. A slotted aluminum glove concept and a woven stainless steel mesh porous glove concept suction surfaces were studied. The laminar flow control glove and a dummy glove with a modified supercritical airfoil, ducting, modified wing leading and trailing edges, modified flaps, and an LFC trim tab were applied to the wing after slot spacing suction parameters, and compression power were determined. The results show that a laminar flow control glove can be applied to the wing of a jet transport with an appropriate suction system installed.

Wright, A. S.↗

NASA NTRS1979

Assessment at full scale of nozzle/wing geometry effects on OTW aero-acoustic characteristics

The effects on acoustic characteristics of nozzle type and location on a wing for STOL engine over-the-wing configurations are assessed at full scale on the basis of model-scale data. Three types of nozzle configurations are evaluated: a circular nozzle with external deflector mounted above the wing, a slot nozzle with external deflector mounted on the wing and a slot nozzle mounted on the wing. Nozzle exhaust plane locations with respect to the wing leading edge are varied from 10 to 46 percent chord (flaps retracted) with flap angles of 20 (takeoff altitude) and 60 (approach attitude). Perceived noise levels (PNL) are calculated as a function of flyover distance at 152 m altitude. From these plots, static EPNL values, defined as flyover relative noise levels, are calculated and plotted as a function of lift and thrust ratios. From such plots the acoustic benefits attributable to variations in nozzle/deflector/wing geometry at full scale are assessed for equal aerodynamic performance.

Groesbeck, D.↗

NASA NTRS1979

Wing aerodynamic loading caused by jet-induced lift associated with STOL-OTW configurations

Surface pressure distributions were obtained with model-scale STOL-OTW configurations using various nozzles designed to promote flow attachment to the wing/flap surface. The nozzle configurations included slot-types and both circular and slot nozzles with external flow deflectors. The wing aerodynamic loading caused by the jet-induced lift is presented in conventional terms of delta p/q as a function of chordwise surface distance in the nozzle centerline plane as well as outboard of the nozzle centerline. Nozzle roof/deflector angle, chordwise location of the nozzle, wing size, and flap deflection angle are included in the geometric variables affecting the wing loading.

Vonglahn, U.↗

NASA NTRS1979

Aerodynamic characteristics of a large-scale semispan model with a swept wing and an augmented jet flap with hypermixing nozzles

The aerodynamic characteristics of the augmentor wing concept with hypermixing primary nozzles were investigated. A large-scale semispan model in the Ames 40- by 80-Foot Wind Tunnel and Static Test Facility was used. The trailing edge, augmentor flap system occupied 65% of the span and consisted of two fixed pivot flaps. The nozzle system consisted of hypermixing, lobe primary nozzles, and BLC slot nozzles at the forward inlet, both sides and ends of the throat, and at the aft flap. The entire wing leading edge was fitted with a 10% chord slat and a blowing slot. Outboard of the flap was a blown aileron. The model was tested statically and at forward speed. Primary parameters and their ranges included angle of attack from -12 to 32 degrees, flap angles of 20, 30, 45, 60 and 70 degrees, and deflection and diffuser area ratios from 1.16 to 2.22. Thrust coefficients ranged from 0 to 2.73, while nozzle pressure ratios varied from 1.0 to 2.34. Reynolds number per foot varied from 0 to 1.4 million. Analysis of the data indicated a maximum static, gross augmentation of 1.53 at a flap angle of 45 degrees. Analysis also indicated that the configuration was an efficient powered lift device and that the net thrust was comparable with augmentor wings of similar static performance. Performance at forward speed was best at a diffuser area ratio of 1.37.

Aiken, T. N.↗

NASA NTRS1979

Assessment at full scale of nozzle/wing geometry effects on OTW aeroacoustic characteristics

The effects on acoustic characteristics of nozzle type and location on a wing for STOL engine over-the-wing configurations are assessed at full scale on the basis of model-scale data. Three types of nozzle configurations are evaluated: a circular nozzle with external deflector mounted above the wing, a slot nozzle with external deflector mounted on the wing and a slot nozzle mounted on the wing. Nozzle exhaust plane locations with respect to the wing leading edge are varied from 10 to 46 percent chord (flaps retracted) with flap angles of 20 deg (take-off attitude) and 60 deg (approach attitude). Perceived noise levels (PNL) are calculated as a function of flyover distance at 152 m altitude. From these plots, static EPNL values, defined as flyover relative noise levels, are calculated and plotted as a function of lift and thrust ratios. From such plots the acoustic benefits attributable to variations in nozzle/deflector/wing geometry at full scale are assessed for equal aerodynamic performance.

Groesbeck, D.↗

NASA NTRS1978

Growth, evaluation and modeling of silicon-on-ceramic solar cells

The silicon-on-ceramic (SOC) process uses inexpensive ceramic substrates to provide supported growth of silicon from the melt. The conditions for unidirectional solidification, the grain structure and other properties are quite similar to those of EFG silicon ribbon. Solar cells with interdigital electrodes have demonstrated AMl conversion efficiencies (active area) of 7.8% without AR coatings and 10.1% efficiencies with an AR coating of SiO. Mathematical modeling of the series resistance of cells shows the feasibility of making electrical contact to the base layer of the cell through slots in the substrate. However, series resistance in the base layer sets an upper limit on slot spacing for efficient cell performance.

Zook, J. D.↗

NASA NTRS1979

Wing aerodynamic loading caused by jet-induced lift associated with STOL-OTW configurations

Surface pressure distributions were obtained with model-scale STOL-OTW configurations using various nozzles designed to promote flow attachment to the wing-flap surface. The nozzle configurations included slot-types and both circular and slot nozzles with external flow deflectors. The wing aerodynamic loading caused by the jet-induced lift is presented in conventional terms of delta p/q as a function of chordwise surface distance in the nozzle centerline plane as well as outboard of the nozzle centerline. Included in the geometric variables affecting the wing loading are nozzle roof/deflector angle, chordwise location of the nozzle, wing size, and flap deflection angle.

Von Glahn, U.↗

NASA NTRS1980

Bayonet plug with ramp-activated lock

Matched pair of washers with broad surface ramps is locking mechanism in bayonet plug. It can be used where threaded springs and fasteners are impractical because of extreme temperatures or other environmental incompatibility. Matched pair of ramped washers is placed on plug and bayonet inserted. Inner slot of one washer matches contour of plug; this washer is stationary. Inner slot of second washer is circular. When second washer is rotated, washers push against bayonet plug, locking it in place. Retaining wire secures plug.

Wood, K. E.↗

NASA NTRS1980

Design studies of Laminar Flow Control (LFC) wing concepts using superplastics forming and diffusion bonding (SPF/DB)

Alternate concepts and design approaches were developed for suction panels and techniques were defined for integrating these panel designs into a complete LFC 200R wing. The design concepts and approaches were analyzed to assure that they would meet the strength, stability, and internal volume requirements. Cost and weight comparisions of the concepts were also made. Problems of integrating the concepts into a complete aircraft system were addressed. Methods for making splices both chordwise and spanwise, fuel light joints, and internal duct installations were developed. Manufacturing problems such as slot aligment, tapered slot spacing, production methods, and repair techniques were addressed. An assessment of the program was used to developed recommendations for additional research in the development of SPF/DB for LFC structure.

Wilson, V. E.↗

NASA NTRS1980

Microwave beamed power technology improvement

The magnetron directional amplifier was tested for (1) phase shift and power output as a function of gain, anode current, and anode voltage, (2) background noise and harmonics in the output, (3) long life potential of the magnetron cathode, and (4) high operational efficiency. Examples of results were an adequate range of current and voltage over which 20 dB of amplification could be obtained, spectral noise density 155 dB below the carrier, 81.7% overall efficiency, and potential cathode life of 50 years in a design for solar power satellite use. A fabrication method was used to fabricate a 64 slot, 30 in square slotted waveguide array module from 0.020 in thick aluminum sheet. The test results on the array are discussed.

Brown, W. C.↗

NASA NTRS1980

Airframe Noise Reduction Studies and Clean-Airframe Noise Investigation

Acoustic wind tunnel tests were conducted of a wing model with modified leading edge slat and trailing edge flap. The modifications were intended to reduce the surface pressure response to convected turbulence and thereby reduce the airframe noise without changing the lift at constant incidence. Tests were conducted at 70.7 and 100 m/sec airspeeds, with Reynolds numbers 1.5 x 10 to the 6th power and 2.1 x 10 to the 6th power. Considerable reduction of noise radiation from the side edges of a 40 deflection single slotted flap was achieved by modification to the side edge regions or the leading edge region of the flap panel. Total far field noise was reduced 2 to 3 dB over several octaves of frequency. When these panels were installed as the aft panel of a 40 deg deflection double slotted flap, 2 dB noise reduction was achieved.

Fink, M. R.↗

NASA NTRS1980

Test section configuration for aerodynamic testing in shock tubes

This paper presents results of a study of the test section configuration required to minimize or alleviate interference effects on model flow produced by the presence of test section walls in the aerodynamic testing of two dimensional transonic airfoils in a shock tube. Tests at a nominal Mach number of 0.85 and a chord Reynolds number of 2,000,000 were carried out by means of schlieren photography and pressure measurements for several symmetric airfoil profiles using shock tube test sections with unmodified straight walls, contoured walls, and slotted walls with adjacent chambers. Results were compared with corresponding results from conventional wind tunnel tests of the airfoils. Results for the straight wall tests show major airfoil flow distortions. Results from contoured wall tests and those performed using a slotted wall test section developed in this study exhibit essential agreement with wind tunnel results. The collective results show that test sections for aerodynamic testing can be designed for shock tubes that will alleviate wall interference effects.

Cook, W. J.↗