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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 271 records · Page 15
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Wind tunnel tests of a zero length, slotted-lip engine air inlet for a fixed nacelle V/STOL aircraft

Zero length, slotted lip inlet performance and associated fan blade stresses were determined during model tests using a 20 inch diameter fan simulator in the NASA-LeRC 9 by 15 foot low speed wind tunnel. The model configuration variables consisted of inlet contraction ratio, slot width, circumferential extent of slot fillers, and length of a constant area section between the inlet throat and fan face. The inlet performance was dependent on slot gap width and relatively independent of inlet throat/fan face spacer length and slot flow blockage created by 90 degree slot fillers. Optimum performance was obtained at a slot gap width of 0.36 inch. The zero length, slotted lip inlet satisfied all critical low speed inlet operating requirements for fixed horizontal nacelles subsonic V/STOL aircraft.

Woollett, R. R.↗
NASA NTRS1982

A NASTRAN model of a large flexible swing-wing bomber. Volume 2: NASTRAN model development-horizontal stabilzer, vertical stabilizer and nacelle structures

The NASTRAN model plans for the horizontal stabilizer, vertical stabilizer, and nacelle structure were expanded in detail to generate the NASTRAN model for each of these substructures. The grid point coordinates were coded for each element. The material properties and sizing data for each element were specified. Each substructure model was thoroughly checked out for continuity, connectivity, and constraints. These substructures were processed for structural influence coefficients (SIC) point loadings and the deflections were compared to those computed for the aircraft detail models. Finally, a demonstration and validation processing of these substructures was accomplished using the NASTRAN finite element program installed at NASA/DFRC facility.

Mock, W. D.↗
NASA NTRS1984

An experimental investigation of nacelle-pylon installation on an unswept wing at subsonic and transonic speeds

A wind tunnel investigation was conducted to determine the aerodynamic interference associated with the installation of a long duct, flow-through nacelle on a straight unswept untapered supercritical wing. Experimental data was obtained for the verification of computational prediction techniques. The model was tested in the 16-Foot Transonic Tunnel at Mach numbers from 0.20 to 0.875 and at angles of attack from about 0 deg to 5 deg. The results of the investigation show that strong viscous and compressibility effects are present at the transonic Mach numbers. Numerical comparisons show that linear theory is adequate for subsonic Mach number flow prediction, but is inadequate for prediction of the extreme flow conditions that exist at the transonic Mach numbers.

Carlson, J. R.↗
NASA NTRS1984

Flow simulations for nacelle-propeller configurations using Euler equations

Euler codes for both axisymmetric and general three-dimensional nacelle-propeller flow analysis have been developed. Surface-fitted grids are generated either by a finite difference method or by an algebraic method. The propeller is represented by an actuator disk along a computational plane where proper boundary conditions are assigned to simulate the propeller power loading. Computed results for a NASA SR3 propeller as well as a NASA turboprop configuration are compared with test data. Good agreement has been achieved through the present simulation method.

Yu, N. J.↗
NASA NTRS1986

Integration effects of underwing forward- and rearward-mounted separate-flow, flow-through nacelles on a high-wing transport

An experimental investigation was conducted in the Langley 16-Foot Transonic Tunnel at free-stream Mach numbers from 0.70 to 0.82 and angles of attack from -2.5 to 4.0 degrees to determine the integration effects of pylon-mounted underwing forward and rearward separate-flow, flow-through nacelles on a high-wing transonic transport configuration. The results showed that the installed drag of the nacelle/pylon in the rearward location was slightly less than that of the nacelle/pylon in the forward location. This reduction was due to the reduction in calculated skin friction of the nacelle/pylon configuration. In all cases the combined value of form, wave, and interference drag was excessively high. However, the configuration with the nacelle/pylon in a rearward location produced an increase in lift over that of the basic wing-body configuration.

Lamb, M.↗
NASA NTRS1986

Hover in-ground-effect testing of a full-scale, tilt-nacelle V/STOL model

A full-scale, tilt-nacelle V/STOL aircraft model was tested in hover at the National Full Scale Aerodynamics Complex (NFAC), NASA Ames Research Center. The model was powered by two TF-34 turbofan engines. It was tested at several ground heights and control deflections. Test technique and test setup were documented. Limited results show that: (1) a small change in control power with ground height was measured, and control power was found to be good over + or - 20 deg of horizontal vane deflection; (2) integrated fuselage undersurface pressures, when compared with the total model loads and measured thrust, defined the effect of the fountain and its related flow field on model forces and moments; and (3) there was no indication of hot gas ingestion during simulated takeoff in calm winds from wheels on deck ground height.

Eshleman, J. E.↗
NASA NTRS1986

Hover in-ground-effect testing of a full-scale, tilt-nacelle V/STOL model

A full-scale, tilt-nacelle V/STOL aircraft model was tested in hover at the National Full Scale Aerodynamics Complex (NFAC), NASA Ames Research Center. The model was powered by two TF-34 turbofan engines. It was tested at several ground heights and control deflections. Test technique and test setup were documented. Limited results show that (1) a small change in control power with ground height was measured, and control power was found to be good over + or - 20 deg of horizontal vane deflection; (2) integrated fuselage undersurface pressures, when compared with the total model loads and measured thrust, defined the effect of the fountain and its related flow field on model forces and moments; and (3) there was no indication of hot gas ingestion during simulated takeoff in calm winds from wheels on deck ground height.

Eshleman, J. E.↗
NASA NTRS1987

Aerodynamic analysis for aircraft with nacelles, pylons, and winglets at transonic speeds

A computational method has been developed to provide an analysis for complex realistic aircraft configurations at transonic speeds. Wing-fuselage configurations with various combinations of pods, pylons, nacelles, and winglets can be analyzed along with simpler shapes such as airfoils, isolated wings, and isolated bodies. The flexibility required for the treatment of such diverse geometries is obtained by using a multiple nested grid approach in the finite-difference relaxation scheme. Aircraft components (and their grid systems) can be added or removed as required. As a result, the computational method can be used in the same manner as a wind tunnel to study high-speed aerodynamic interference effects. The multiple grid approach also provides high boundary point density/cost ratio. High resolution pressure distributions can be obtained. Computed results are correlated with wind tunnel and flight data using four different transport configurations. Experimental/computational component interference effects are included for cases where data are available. The computer code used for these comparisons is described in the appendices.

Boppe, Charles W.↗
NASA NTRS1987

Effect of variable inlet guide vanes on the operating characteristics of a tilt nacelle inlet/powered fan model

The effects of a variable inlet guide vane (VIGV) assembly on the operating characteristics of a V/STOL inlet and on the performance of a 20-in. (0.508-m) diameter fan engine were investigated. The data indicate that the VIGVs are effective thrust modulators over a wide range of free-stream velocities, nacelle angles of attack, and fan speeds. The thrust modulation ranges, including choking limits, fan stall limits, and inlet separation boundaries are presented. The presence of the VIGV assembly causes significant losses in inlet angle-of-attack capability and generally increases the blade stress levels at all limit conditions except at high angle of attack and high free-stream velocity. Reducing the fan nozzle exit area limited the positive VIGV actuation range and consequently decreased the range of thrust modulation at all limit conditions except at both high free-stream velocity and high angle of attack conditions.

Woollett, R. R.↗
NASA NTRS1986

Analysis of results from wind tunnel tests of inlets for an advanced turboprop nacelle installation

Inlets for tractor installations of advanced turboprop propulsion systems were tested in three phases, covering a period from November, 1982 to January, 1984. Nacelle inlet configuration types included single scoop, twin scoop, and annular arrangements. Tests were performed with and without boundary layer diverters and several different diverter heights were tested for the single scoop inlet. This same inlet was also tested at two different axial positions. Test Mach numbers ranged from Mach 0.20 to 0.80. Types of data taken were: (1) internal and external pressures, including inlet throat recoveries; (2) balance forces, including thrust-minus-drag; and (3) propellar blade stresses.

Hancock, J. P.↗
NASA NTRS1987

Nacelle aerodynamic performance

The boundary layer transition location was measured on a nacelle shape using the sublimating chemical flow visualization technique. This technique involves coating the surface with a thin film of volatile chemical solid, which, during exposure to a free stream airflow, rapidly sublimates in the turbulent boundary layer as a result of high shear stress and high mass transfer near the surface. Transition is indicated because the chemical coating remains relatively unaffected in the laminar region due to lower shear and low mass transfer. The slow response time of the chemical in a laminar boundary allowed for two test conditions during the same flight. The aircraft was first flown at the desired airspeed and altitude with the noise source off. Once a pattern had developed, the noise source was turned on to the desired setting and a new chemical pattern was sought. In this fashion a direct comparison of the effect of the noise could be determined.

Obara, Clifford J.↗
NASA NTRS1991

Effect of solidity and inclination on propeller-nacelle force coefficients

A series of wind tunnel experiments were conducted to study the effect of propeller solidity and thrust axis inclination on the propeller normal force coefficient. Experiments were conducted in the Langley 14 by 22 foot Subsonic Tunnel with a sting mounted, counterrotation, scale model propeller and nacelle. Configurations had two rows of blades with combinations of 4 and 8 blades per hub. The solidity was varied by changing the number of blades on both rows. Tests were conducted for blade pitch setting of 31.34 deg, 36.34 deg, and 41.34 deg over a range of angle of attack from -10 deg to 90 deg and range of advance ratio from 0.8 to 1.4. The increase in propeller normal force with angle of attack is greater for propellers with higher solidity.

Gentry, Garl L., Jr.↗
NASA NTRS1992

An installed nacelle design code using a multiblock Euler solver. Volume 2: User guide

This is a user manual for the general multiblock Euler design (GMBEDS) code. The code is for the design of a nacelle installed on a geometrically complex configuration such as a complete airplane with wing/body/nacelle/pylon. It consists of two major building blocks: a design module developed by LaRC using directive iterative surface curvature (DISC); and a general multiblock Euler (GMBE) flow solver. The flow field surrounding a complex configuration is divided into a number of topologically simple blocks to facilitate surface-fitted grid generation and improve flow solution efficiency. This user guide provides input data formats along with examples of input files and a Unix script for program execution in the UNICOS environment.

Chen, H. C.↗
NASA NTRS1992

Some considerations on the integration of engine nacelles into low-boom aircraft concepts

A study of wind-tunnel data has shown why unexpected strong shock waves appeared in wind tunnel pressure signatures of two low-boom models, and has indicated that changes to the current methods for analyzing and designing low-boom aircraft are needed. The discussion provided corrections for the interface lift code, and suggested methods of treatment for the equivalent areas of the aircraft, especially the nacelles and the interference lift, which were to be used in the aircraft design and the sonic boom analysis.

Mack, Robert J.↗
NASA NTRS1993

An installed nacelle design method using multiblock Euler solver

An efficient multiblock Euler design method was developed for designing a nacelle installed on geometrically complex airplane configurations. This approach employed a design module based on a direct iterative surface curvature method developed at NASA-Langley. A multiblock Euler flow solver was used for computing flow around complex geometries. The flow solver used a finite-volume formulation with explicit time-stepping to solve the Euler equations. It used a multiblock version of the multigrid method to accelerate the convergence of the calculations. The design module successively updated the surface geometry to reduce the difference between the computed and target pressure distributions. In the flow solver, the change in surface geometry was simulated by applying surface transpiration boundary conditions to avoid repeated grid generation during design iterations. Smoothness of the designed surface was ensured by alternate application of streamwise and circumferential smoothings.

Chen, H. C.↗
NASA NTRS1937

Tests of a Wing-nacelle-Propeller Combination at Several Pitch Settings up to 42 Degrees

This report presents the results of tests of a 4-foot model of Navy propeller No. 4412 in conjunction with an NACA cowled nacelle mounted ahead of a thick wing in the 20-foot propeller-research tunnel. A range of propeller pitches from 17 degrees to 42 degrees at 0.75r was covered, and for this propeller the efficiency reached a maximum at a pitch setting of 27 degrees; at high pitches the efficiencies were slightly lower. The corrected propulsive efficiency is shown to be independent of the angle of attack for the high-speed and the climbing ranges of flight. A working chart is presented for the selection of similar propellers over a wide range of airplane speed, engine power, and propeller revolution.

Windler, Ray↗
NASA NTRS1996

Finite Difference Time Marching in the Frequency Domain: A Parabolic Formulation for Aircraft Acoustic Nacelle Design

An explicit finite difference iteration scheme is developed to study harmonic sound propagation in aircraft engine nacelles. To reduce storage requirements for large 3D problems, the time dependent potential form of the acoustic wave equation is used. To insure that the finite difference scheme is both explicit and stable, time is introduced into the Fourier transformed (steady-state) acoustic potential field as a parameter. Under a suitable transformation, the time dependent governing equation in frequency space is simplified to yield a parabolic partial differential equation, which is then marched through time to attain the steady-state solution. The input to the system is the amplitude of an incident harmonic sound source entering a quiescent duct at the input boundary, with standard impedance boundary conditions on the duct walls and duct exit. The introduction of the time parameter eliminates the large matrix storage requirements normally associated with frequency domain solutions, and time marching attains the steady-state quickly enough to make the method favorable when compared to frequency domain methods. For validation, this transient-frequency domain method is applied to sound propagation in a 2D hard wall duct with plug flow.

Baumeister, Kenneth J.↗