Search NASA⌕ Search

SEARCH · Search NASA

Results for “Inlets”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 937 records · Page 52
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Prediction of Laminar and Turbulent Boundary Layer Flow Separation in V/STOL Engine Inlets

A description is presented of the development of the boundary layer on the lip and diffuser surface of a subsonic inlet at arbitrary operating conditions of mass flow rate, free stream velocity and incidence angle. Both laminar separation on the lip and turbulent separation in the diffuser are discussed. The agreement of the theoretical results with model experimental data illustrates the capability of the theory to predict separation. The effects of throat Mach number, inlet size, and surface roughness on boundary layer development and separation are illustrated.

Chou, D. C.↗
NASA NTRS1977

Low speed tests of a fixed geometry inlet for a tilt nacelle V/STOL airplane

Test data were obtained with a 1/4 scale cold flow model of the inlet at freestream velocities from 0 to 77 m/s (150 knots) and angles of attack from 45 deg to 120 deg. A large scale model was tested with a high bypass ratio turbofan in the NASA/ARC wind tunnel. A fixed geometry inlet is a viable concept for a tilt nacelle V/STOL application. Comparison of data obtained with the two models indicates that flow separation at high angles of attack and low airflow rates is strongly sensitive to Reynolds number and that the large scale model has a significantly improved range of separation-free operation.

Syberg, J.↗
NASA NTRS1977

Stalled and stall-free performance of axial-flow compressor stage with three inlet-guide-vane and stator-blade settings

The performance of the first stage of a transonic, multistage compressor was mapped over a range of inlet-guide-vane and stator-blade settings. Both stall-free and deep-stall performance data were obtained. For the settings tested, as stall was encountered and flow was further reduced, a relatively sharp drop in pressure ratio occurred and was followed by a continuing but more gradual reduction in pressure ratio with reduced flow. The position of the stall line on the map of pressure ratio against equivalent weight flow was essentially unaffected over the range of inlet-guide-vane and stator-blade settings.

Urasek, D. C.↗
NASA NTRS1977

Inlet Reynolds number and temperature effects on the steady-state performance of a TFE731-2 turbofan engine

Effects of varying engine inlet Reynolds number index (0.75, 0.50, 0.25, and 0.12) and temperature (289 and 244 K) on a TFE731-2 turbofan engine were evaluated. Results were classified as either compression system effects or effects on overall performance. Standard performance maps are used to present compression system performance. Overall performance parameters are presented as a function of low rotor speed corrected to engine inlet temperature.

Bobula, G. A.↗
NASA NTRS1977

Performance at Mach 3.52 of a Mach 2.5 all external-compression, two dimensional inlet

A quick-look test was conducted in the 10- by 10-foot supersonic wind tunnel to provide some qualitative information on operating a low Mach number design inlet in a highly oversped condition. The model which is a two-dimensional, three-ramp, all-external-compression inlet designed to match a J-85 turbojet engine at Mach 2.5 was run at Mach 3.52 and zero angle-of-attack and yaw. Results are presented showing the effect of external ramp angle combinations, diffuser ramp position, and amount of bleed.

Cubbison, R. W.↗
NASA NTRS1976

A preliminary in-duct measurement of spinning modes in the inlet of a rotating vehicle

Suppression of noise radiated from a jet engine duct is an important environmental problem. Results are presented for a study aimed at developing and evaluating an experimental method for measuring the complex acoustic pressure field at a plane in the inlet of a fan duct. The theory of modal propagation is outlined and related to the theory of measuring spinning modes in the duct. A spinning mode measurement apparatus is described, and preliminary test results of the modal measurement for several operating speeds are presented. The measurement of spinning modes is successfully carried out in the inlet of a rotating vehicle under conditions representative of an actual jet engine. Data repeatability and problems encountered in the measurement are examined. In particular, it is important to calibrate the probe systems for phase and level. Recommendations for future improvements in the method are made.

Kraft, R. E.↗
NASA NTRS1977

Prediction of laminar and turbulent boundary layer flow separation in V/STOL engine inlets

The paper provides a theoretical description of the development of the boundary layer on the lip and diffuser surface of a subsonic inlet at arbitrary operating conditions of mass flow rate, freestream velocity and incidence angle. Both laminar separation on the lip and turbulent separation in the diffuser are discussed. The agreement of the theoretical results with model experimental data illustrates the capability of the theory to predict separation. The effects of throat Mach number, inlet size, and surface roughness on boundary-layer development and separation are illustrated.

Chou, D. C.↗
NASA NTRS1976

Survey of inlet noise reduction concepts for gas turbine engines

This paper presents an overview of advanced concepts for the suppression of noise in the inlets of gas turbine engines. Noise suppression concepts are described, the directions of current research are reviewed, and problem areas requiring further work are indicated. The discussion focuses on acoustic liners, high Mach number inlets, active acoustic absorption, water vapor injection, and blade row reflection.

Lansing, D. L.↗
NASA NTRS1977

Mach 6 flowfield survey at the engine inlet of a research airplane

A flowfield survey was conducted to better define the nature of vehicle forebody flowfield at the inlet location of an airframe-integrated scramjet engine mounted on the lower surface of a high-speed research airplane to be air launched from a B-52 and rocket boosted to Mach 6. The tests were conducted on a 1/30-scale brass model in a Mach-6 20-in. wind tunnel at Reynolds number of 11,200,000 based on distance to engine inlet. Boundary layer profiles at five spanwise locations indicate that the boundary layer in the area of the forebody centerline is more than twice as thick as the boundary layer at three outboard stations. It is shown that the cold streak found in heating contours on the centerline of the forebody is caused by a thickening of the boundary layer on the centerline, and that this thickening decreases with angle of attack.

Johnson, C. B.↗
NASA NTRS1978

Predicted inlet gas temperatures for tungsten fiber reinforced superalloy turbine blades

Tungsten fiber reinforced superalloy composite (TFRS) impingement cooled turbine blade inlet gas temperatures were calculated taking into account material spanwise strength, thermal conductivity, material oxidation resistance, fiber-matrix interaction, and coolant flow. Measured values of TFRS thermal conductivities are presented. Calculations indicate that blades made of 30 volume percent fiber content TFRS having a 12,000 N-m/kg stress-to-density ratio while operating at 40 atmospheres and a 0.06 coolant flow ratio could permit a turbine blade inlet gas temperature of over 1900K. This is more than 150K greater than similar superalloy blades.

Winsa, E. A.↗
NASA NTRS1976

Inlet technology for powered-lift aircraft

The concepts, analytical tools, and experimental data available for designing inlets for powered lift aircraft are discussed. It is shown that inlets can be designed to meet noise, distortion, and cruise drag requirements at the flight and engine operating conditions of a powered lift aircraft. The penalty in pressure recovery for achieving the required noise suppression was 0.3 percent.

Luidens, R. W.↗
NASA NTRS1978

Design of an air ejector for boundary-layer bleed of an acoustically treated turbofan engine inlet during ground testing

An air ejector was designed and built to remove the boundary-layer air from the inlet a turbofan engine during an acoustic ground test program. This report describes; (1) how the ejector was sized; (2) how the ejector performed; and (3) the performance of a scale model ejector built and tested to verify the design. With proper acoustic insulation, the ejector was effective in reducing boundary layer thickness in the inlet of the turbofan engine while obtaining the desired acoustic test conditions.

Stakolich, E. G.↗
NASA NTRS1978

Some flow phenomena in a constant area duct with a Borda type inlet including the critical region

Mass limiting flow characteristics for a 55 L/D tube with a Borda type inlet were assessed over large ranges of temperature and pressure, using fluid nitrogen. Under certain conditions, separation and pressure drop at the inlet was sufficiently strong to permit partial vaporization and the remaining fluid flowed through the tube as if it were a free jet. An empirical relation was determined which defines conditions under which this type of flow can occur. A flow coefficient is presented which enables estimations of flow rates over the experimental range. A flow rate stagnation pressure map for selected stagnation isotherms and pressure profiles document these flow phenomena.

Hendricks, R. C.↗
NASA NTRS1978

Inlet boundary-layer shapes on four aircraft forebodies at Mach 6

Boundary-layer shape measurements at the engine inlet on four different hypersonic aircraft forebody designs (with no engine on the forebody) are reported. The measurements provide a qualitative assessment of the effectiveness of various forebody geometries as engine inlet precompression surfaces. The designs, tested in a hypersonic tunnel at Mach 6 and a nominal freestream Reynolds number of 30,500,000, included a semiconical forebody, a configuration similar to a slab delta wing, a conical nose blended into a flat surface, and a conical, complex forebody shape. Boundary layer height as a function of forebody compression is shown for each design.

Lawing, P. L.↗
NASA NTRS1978

Development and test of an inlet and duct to provide airflow for a wing boundary layer control system

The boundary layer control (BLC) system of the quiet short-haul research airplane (QSRA) requires significant amounts of pressurized airflow for successful operation. An inlet and duct were successfully developed which removed airflow from the engine fan duct for the BLC system at or above the required total pressure of 99% of the average fan duct total pressure. The design was constrained by the tight space limitations of the QSRA nacelle. Potential flow with boundary layer analysis techniques were used as an aid to select the inlet and duct geometries. Airflow and total pressure profile data were obtained during development tests.

Gunnarson, D. W.↗
NASA NTRS1978

Predicted inlet gas temperatures for tungsten fiber reinforced superalloy turbine blades

Tungsten fiber-reinforced superalloy composite (TFRS) impingement-cooled turbine blade inlet gas temperatures were calculated taking into account material spanwise strength, thermal conductivity, material oxidation resistance, fiber-matrix interaction, and coolant flow. Measured values of TFRS thermal conductivities are presented. Calculations indicate that blades made of 30 volume percent fiber content TFRS having a 12,000 N-m/kg stress-to-density ratio while operating at 40 atm and a 0.06 coolant flow ratio could permit a turbine blade inlet gas temperature of over 1900 K. This is more than 150 K greater than similar superalloy blades.

Winsa, E. A.↗
NASA NTRS1979

Flow fields in supersonic inlets

Flow fields in two- and three-dimensional axisymmetric supersonic inlets are calculated with computer program that uses method of characteristics to compute array of points in flow field. At each point, local pressure, local Mach number, local flow angle, and static pressure are calculated. Program can be used to design and analyze supersonic inlets by determining surface compression rates and throat flow properties.

Sorensen, V. L.↗
NASA NTRS1979

Applications of velocity potential function to acoustic duct propagation and radiation from inlets using finite element theory

A finite element velocity potential program was developed to study acoustic wave propagation in complex geometries. For irrotational flows, relatively low sound frequencies, and plane wave input, the finite element solutions showed significant effects of inlet curvature and flow gradients on the attenuation of a given acoustic liner in a realistic variable area turbofan inlet. The velocity potential approach can not be used to estimate the effects of rotational flow on acoustic propagation, since the potential acoustic disturbances propagate at the speed of the media in sheared flow. Approaches are discussed that are being considered for extending the finite element solution to include the far field, as well as the internal portion of the duct. A new matrix partitioning approach is presented that can be incorporated in previously developed programs to allow the finite element calculation to be marched into the far field. The partitioning approach provided a large reduction in computer storage and running times.

Baumeister, K. J.↗