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At least 487 records · Page 27

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NASA NTRS1972

Aerodynamic characteristics of a large-scale lift-engine fighter model with external swiveling lift-engines

The aerodynamic characteristics of a six-engine (four lift, two lift-cruise) lift-engine model obtained in the Ames 40- by 80-foot wind tunnel are presented. The model was an approximate one-half scale representation of a lift-engine VTOL fighter aircraft with a variable-sweep wing. The four lift-engines were housed in the aft fuselage with the inlets located above the wing. Longitudinal and lateral-directional force and moment data are presented for a range of exhaust gas momentum ratios (thrust coefficients). Wind tunnel forward speed was varied from 0 to 140 knots corresponding to a maximum Reynolds number of 6.7 million. The data are presented without analysis.

Barrack, J. P.↗

NASA NTRS1976

Results of static tests of a 1/4 scale model of the Boeing YC-14 powered-lift system

One quarter scale static ground tests of the Boeing YC-14 powered lift system were conducted for correlation with full scale test results. The 1/4 scale model utilized a JT-15D turbofan engine to represent the CF6-50D engine employed on the YC-14 advanced medium STOL transport prototype aircraft. The tests included evaluation of static turning performance, static surface pressure and temperature distributions, fluctuating loads, and accelerations of portions of the wing, flaps, and fuselage. Results are presented for the landing flap configuration over an appropriate range of fan pressure ratio as affected by several variables including ground height and vortex generator modifications. Static turning angles of the order of 60 deg were obtained. The highest surface pressures and temperatures were concentrated over the upper surface of the flaps in the region immediately aft of the upper surface blown nozzle.

Hassell, J. L., Jr.↗

NASA NTRS1980

Flow visualization study of the HiMAT RPRV

Water tunnel studies were performed to qualitatively define the flow field of the highly maneuverable aircraft technology remotely piloted research vehicle (HiMAT RPRV). Particular emphasis was placed on defining the vortex flows generated at high angles of attack. The flow visualization tests were conducted in the Northrop water tunnel using a 1/15 scale model of the HiMAT RPRV. Flow visualization photographs were obtained for angles of attack up to 40 deg and sideslip angles up to 5 deg. The HiMAT model was investigated in detail to determine the canard and wing vortex flow field development, vortex paths, and vortex breakdown characteristics as a function of angle of attack and sideslip. The presence of the canard caused the wing vortex to form further outboard and delayed the breakdown of the wing vortex to higher angles of attack. An increase in leading edge camber of the maneuver configuration delayed both the formation and the breakdown of the wing and canard vortices. Additional tests showed that the canard vortex was sensitive to variations in inlet mass flow ratio and canard flap deflection angle.

Lorincz, D. J.↗

NASA NTRS1984

An experimental and theoretical analysis of the aerodynamic characteristics of a biplane-winglet configuration

Improving the aerodynamic characteristics of an airplane with respect to maximizing lift and minimizing induced and parasite drag are of primary importance in designing lighter, faster, and more efficient aircraft. Previous research has shown that a properly designed biplane wing system can perform superiorly to an equivalent monoplane system with regard to maximizing the lift-to-drag ratio and efficiency factor. Biplanes offer several potential advantages over equivalent monoplanes, such as a 60-percent reduction in weight, greater structural integrity, and increased roll response. The purpose of this research is to examine, both theoretically and experimentally, the possibility of further improving the aerodynamic characteristics of the biplanes configuration by adding winglets. Theoretical predictions were carried out utilizing vortex-lattice theory, which is a numerical method based on potential flow theory. Experimental data were obtained by testing a model in the Pennsylvania State University's subsonic wind tunnel at a Reynolds number of 510,000. The results showed that the addition of winglets improved the performance of the biplane with respect to increasing the lift-curve slope, increasing the maximum lift coefficient, increasing the efficiency factor, and decreasing the induced drag. A listing of the program is included in the Appendix.

Gall, P. D.↗

NASA NTRS1995

Development of multiobjective optimization techniques for sonic boom minimization

An optimization procedure is developed for the simultaneous improvement of the aerodynamic and sonic boom characteristics of high speed aircraft. From a sonic boom perspective, it is desirable to minimize the first peak in the overpressure signal at a specified distance away from the aircraft. From aerodynamic point of view, the aerodynamic drag coefficient ratio must be minimized while maintaining the lift coefficient at desired level. The optimization procedure is applied to wing-body configurations related to high speed aircraft. The objectives of this current research are: (1) development of a multiobjective optimization procedure for aerospace vehicles with the integration of sonic boom and aerodynamic performance criteria; and (2) development of semi-analytical approach for calculating sonic boom design sensitivities.

Chattopadhyay, Aditi↗

NASA NTRS2013

Advanced Seal Sessions I and II

As aircraft operators continue to seek higher fuel efficiency, lower emissions, and longer on-wing performance, turbine engine designers are scrutinizing all components for areas of improvement. To achieve overall goals, turbine pressure ratios and by-pass ratios continue to climb. Also, designers are seeking to minimize parasitic and cooling flows to extract the most useful work out of the flow stream, placing a renewed interest on seal technology and secondary flow path management. In the area of future manned spacecraft, advancements are being examined for both habitat seals and re-entry thermal protection system thermal barrierseals. For long duration space craft, designers are continuing to look for savings in parasitic losses to reduce the amount of cabin re-supply air that needs to be brought along. This is placing greater demands on seal designs and materials to exhibit low leakage and be resistant to space environments. For future missions to and from distant planets, the re-entry heating will be higher than for low-earth orbit or lunar return motivating advanced thermal barrier development. This presentation will provide an overview of the seal challenges and opportunities in these diverse areas.

turbine engines↗

NASA NTRSDate not supplied

Flight Deck Design of a Hybrid Turbine/Electric Aircraft

The SUbsonic Single Aft eNgine (SUSAN) program is being developed as a sustainable subsonic regional aircraft. NASA is conducting trade studies for this future hybrid single aisle passenger aircraft. The goal of reducing emission levels by 50% will be enabled through an advanced design. An aft mounted single turbine engine provides thrust and electric power to drive 16 wing mounted electric engines. Using the 16 counter-rotating electric fans will create an efficient, very high bypass ratio, engine. Electric engines allow for distributed thrust, reducing control surfaces and provide a greater dynamic response. Batteries provide boost for takeoff and climb, allowing a smaller, more efficient, turbine engine. As part of the SUSAN effort, two pilot-in-the-loop studies were conducted at NASA Langley Research Center in Virginia to explore flight deck design issues. In particular: how many throttles are required/desired for a 17-engine aircraft, does the hybrid electric design change the answer, what are the requirements for electric engine displays, what system pages are required, and what information is required to monitor the batteries. Objective and subjective data were collected after each scenario and at the end of the day with a guided set of questionnaires from sixteen crews paired by airline. Data along with pilot comments were used to improve the throttle and engine displays between the studies and used to make the final recommendations on flight deck configurations. This paper provides final design recommendations for the SUSAN flight deck and justification for each recommendation.

PAI↗

NASA NTRS1995

Sensitivity of engine-integrated waverider performance to static margin constraint

The performance of an engine-integrated wedge caret-wing waverider is optimized with respect to a set of geometric and flight attitude variables with constraints for steady state flight and static margin. The optimization is done with different values for the constraint on the static margin, and the resulting performances and geometries compared. This comparison is done for three performance parameters: L/D ratio, range coefficient, and a parameter that measures energy height gain per unit weight of fuel. The vehicle model incorporates a one-dimensional calculation on the forebody, inlet and wings. Fuel injection is done prior to the combustor entrance and flow properties are calculated with a one-dimensional model using a correlation for the shock shape in front of a transverse jet. The combustor is modeled as a shock-induced-combustion scramjet, and the nozzle flow field is calculated using the method of characteristics.

Tarpley, C.↗

NASA NTRSDate not supplied

Fluidic Fence Flow Control on A 30° Swept Wing in Compressible Freestreams

A 30° swept wing with a NACA 64(3)-618 airfoil cross-section was evaluated in four different freestream conditions with Mach numbers increasing from 0.05 to 0.7 using computational fluid dynamics simulations. Active flow control (AFC) through a streamwise row of vortex generating jets was applied at 70% span, blowing inboard to obstruct the development of spanwise flow and increase lift outboard of the control location. The effectiveness of the AFC was evaluated at α = 5° and 10° as freestream Mach number increased and the AFC mass flow coefficient was held constant. Increases to lift coefficient were reduced at higher Mach numbers, but the ratio of change in lift coefficient and the AFC momentum coefficient remained roughly constant. The fluidic fence caused decreased pressure coefficients on the outboard wing sections, but this region of decreased pressure coefficient moved aft on the chord with increasing Mach number. Mach 0.7 is higher than the critical Mach number of the wing and produced interesting interplay with the AFC, as the suction surface shock moved forward on the inboard wing section but moved aft on the outboard wing section.

Evan J McFadden↗

NASA NTRSDate not supplied

Fluidic Fence Flow Control on A 30° Swept Wing in Compressible Freestreams

Evan J McFadden↗

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 NTRS1943

The Effect of Compressibility on the Growth of the Laminar Boundary Layer on Low-Drag Wings and Bodies

The development of the laminar boundary layer in a compressible fluid is considered. Formulas are given for determining the boundary-layer thickness and the ratio of the boundary-layer Reynolds number to the body Reynolds number for airfoils and bodies of revolution. It i s shown that the effect of compressibility will profoundly alter the Reynolds number corresponding to the upper limit of the range of the low-drag coefficients . The available data indicate that for low-drag and high critical compressibility speed airfoils and bodies of revolution, this effect is favorable.

Allen, H. Julian↗

NASA NTRSDate not supplied

Upgrades to the Single Stage Axial Compressor and Fan Facility For Low Pressure Ratio and Boundary Layer Ingesting Fan Research

Next generation aircraft engine efficiency goals will be met through high bypass ratio engines. To achieve these goals, a combination of small core and low pressure ratio fan technologies will be necessary. Additionally, advanced propulsion air-frame integration concepts, such as boundary layer propulsion, and distributed electrically driven fans with short inlets or wing integration strategies, are beginning to be investigated for their potential fuel burn savings. In order to realize the potential fuel savings from these technologies, it is necessary to have testing capabilities for the components. The NASA Glenn Research Center (GRC) Single StageAxial Fan and Compressor Facility (also called the GRC W-8Facility) has recently undergone several significant upgrades in order to effectively test low pressure ratio fans and various inlet distortions. This paper will outline various challenges to testing low pressure ratio fans and the methods implemented to ensure that the W-8 facility is capable of performing these tests and acquiring high quality data. The upgrades include significant pip-ing upgrades to reduce pressure loss and turbulence, capability for inlet total pressure and swirl distortion, increased test section length including a longer shaft, a two component balance, an up-graded rotating data system, and a new temperature characterization to reduce uncertainties in thermocouple measurements

W-8 Facility↗

NASA NTRS1993

Transitional flight characteristics of a geometrically simplified STOVL model

The transitional flight characteristics of a geometrically simplified Short Take-Off Vertical Landing (STOVL) aircraft configuration were measured in the NASA Ames 7- by 10-Foot Wind Tunnel. The experiment was designed to provide detailed data for evaluating the capability of computational fluid dynamics methods to predict the important powered lift flow parameters. The model consists of a 60 deg cropped delta wing planform; a blended fuselage; and tandem, circular, high pressure air jets that exit perpendicular to the flat lower surface. Freestream Mach number is limited to a maximum 0.2. Model angle of attack ranges from -10 deg to +20 deg. The nozzle pressure ratios of both jets are varied between 1 and 3, and the jet exit temperatures are maintained at near ambient conditions. Detailed surface pressure measurements show that suction pressure peaks located on the upper surface of the wing during conventional wingborne flight for angles of attack greater than 5 deg move to the wing lower surface at angles of attack less than 0 deg. A reduction in these suction pressure peaks is observed when the lift jets are operating. With sonic jet exit conditions, a freestream Mach number of 0.14, and 0 deg angle of attack, the jet-induced suckdown is equivalent to a 3.7 deg reduction in angle of attack. Schlieren, laser light sheet flow visualization and total pressure measurements in the jet plumes provide a description of the three-dimensional jet efflux flowfield.

Roth, Karlin R.↗

NASA NTRS1985

Diurnal CO variations in the Venus mesosphere from CO microwave spectra

Microwave spectra of CO in the Venus mesosphere were measured and analyzed in order to provide mixing profiles. The results indicate that there is a significant dependence of the observed spectra on the phase of Venus. This dependence is tied to a diurnal variation in the vertical profile of CO mixing ratios with the local solar zenith angle. Spectra of the nightside hemisphere are characterized by very little absorption in the wings of the spectra, yet very deep absorption in the line center. Dayside spectra exhibit considerably greater absorption in the line wings and less absorption in the line center. Solutions for the CO mixing profile derived from spectra show that the nightside atmosphere contains two to four times the CO abundance above about 95 km relative to the dayside atmosphere above 95 km. Conversely, the dayside atmosphere between 80 and 90 km shows two to four times the CO abundance for the same altitude region in the nightside atmosphere.

Clancy, R. T.↗

NASA NTRS1938

Wind-tunnel tests of a Clark Y wing having split flaps with gaps

Tests were made of the Clark Y wing having split flaps with a gap between the flap and the lower surface of the wing. Lift, drag, and pitching moments were measured for the wing with three different sizes of flap. It was found that any gap between the flap and the wing reduced the lift, the drag, and the pitching moments, but that the center-of-pressure movement and the ratio of lift to drag were little affected.

Wenzinger, Carl J↗

NASA NTRS1951

An Investigation at Mach Numbers of 1.40 and 1.59 of the Effects of Aileron Profile on the Aerodynamic Characteristics of a Complete Model of a Supersonic Aircraft Configuration

An investigation has been conducted in the Langley 4- by 4-foot supersonic tunnel at Mach numbers 1.40 and 1.59 to determine the effect of aileron profile on the aerodynamic characteristics of a complete model of a supersonic aircraft configuration. The model had a 40 degree sweptback tapered wing with 10-percent-thick circular-arc sections normal to the quarter-chord line. The ailerons were 20-percent chord and were located on the outboard 50 percent of the wing semispans. The various ailerons investigated included the basic circular-arc profile and three flat-sided ailerons having ratios of trailing-edge thickness to hinge-line thickness t of 0, 0.5, and 1.0. Low aileron effectiveness was obtained with the circular-arc and t = 0 profiles. Increasing the trailing-edge thickness (t = 0.5 and 1.0) resulted in increased effectiveness as well as increased hinge moments with only a slight increase in drag.

Spearman, M Leroy↗

NASA NTRS1952

Low-Speed Wind-Tunnel Investigation of the Drag of a Lockheed F-94C Airplane (A.F. No. 50-956)

The aerodynamic characteristics in pitch of an F-94C airplane, with the primary attention given to its drag characteristics, have been evaluated at low speed in the Ames 40- by 80-foot wind tunnel. The increments of drag due to various surface irregularities, ports, and component parts of the production airplane were determined. Wing-wake surveys were taken to determine the section drag coefficients at midsemispan for the smooth and the production wing. Base-pressure and internal drags of the air-induction system were measured at low inlet-velocity ratios. The characteristics of the airplane in the landing configuration are also included.

Maki, Ralph L.↗