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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Free jet phenomena in a 90 degree-sharp edge inlet geometry

Under certain conditions, inlets with a sharp edge or geometric corner were shown to exhibit sufficiently strong separation effects to permit the working fluid to flow through the duct as if it were a free jet. Mass limiting flow data and associated pressure profiles for tubes of 53, 64, 73, and 105 length/diameter with a 90 deg sharp edge or orifice type inlet were taken and compared to Borda type inlet data to determine bounds of the free jet phenomena. For smooth tubes the limits appear to be one dimensional and dependent only on inlet stagnation conditions. Similar free jet effects were found for fluid hydrogen indicating that fluid jetting may common to all fluids flowing through 90 deg sharp edge inlet geometries.

Hendricks, R. C.↗
NASA NTRS1979

An efficient user-oriented method for calculating compressible flow in an about three-dimensional inlets

A panel method is used to calculate incompressible flow about arbitrary three-dimensional inlets with or without centerbodies for four fundamental flow conditions: unit onset flows parallel to each of the coordinate axes plus static operation. The computing time is scarcely longer than for a single solution. A linear superposition of these solutions quite rigorously gives incompressible flow about the inlet for any angle of attack, angle of yaw, and mass flow rate. Compressibility is accounted for by applying a well-proven correction to the incompressible flow. Since the computing times for the combination and the compressibility correction are small, flows at a large number of inlet operating conditions are obtained rather cheaply. Geometric input is aided by an automatic generating program. A number of graphical output features are provided to aid the user, including surface streamline tracing and automatic generation of curves of curves of constant pressure, Mach number, and flow inclination at selected inlet cross sections. The inlet method and use of the program are described. Illustrative results are presented.

Hess, J. L.↗
NASA NTRS1979

Critical mass flux through short Borda type inlets of various cross sections

Mass flux measurements associated with choked flows through four Borda-type inlet geometries: circular, square, triangular, and rectangular (two-dimensional) and two sharp-edged geometries are discussed for a wide range of inlet stagnation conditions. The results obtained indicate that the mass flux is independent of the inlet cross-section geometry, while it is dependent on the inlet stagnation conditions. The results also suggest that parallel surfaces as found in seals, dampers, bearings, and heat exchanger tubes of rectangular cross section with Borda-type inlet configurations are subject to large forces. It is noted that the reduced mass flux is independent of working fluid.

Hendricks, R. C.↗
NASA NTRS1980

Aerodynamic and inlet flow characteristics of several hypersonic airbreathing missile concepts

Four conceptual hypersonic missile configurations were examined experimentally and theoretically. Two of the concepts employed twin module bottom-mounted engines and two were designed for upper surface inlets or engines with the intent of reducing the vehicle observables. The tests were conducted at Mach 6 and Reynolds numbers of 6 to 7.5 x 10 to the 6th per foot. Flow field surveys in the vicinity of the engine inlet were made on all configurations and force and moment tests were conducted on three of the vehicles. Stability and control characteristics of the bottom-mounted engine configurations which incorporated slender, low wings were dominated by strong vortices that promoted severe pitchup tendencies. The shock layer and flow quality in the vicinity of the bottom-mounted engine inlets were dependent on nose shape. The spatula-like upper surface engine concept demonstrated good performance and had uniform flow entering the engine inlet, while the upper surface inlet concept with a highly swept forebody incurred large gradients due to interactions with leading edge shocks.

Dillon, J. L.↗
NASA NTRS1980

Acoustic characteristics of two hybrid inlets at forward speed

A wind tunnel investigation of the acoustic and aerodynamic characteristics of two hybrid inlets installed on a JT15D-1 turbofan engine was performed. The hybrid inlets combined moderate throat Mach number and wall acoustic treatment to suppress the fan inlet noise. Acoustic and aerodynamic data were recorded over a range of flight and engine operating conditions. In a simulated flight environment, the hybrid inlets provided significant levels of suppression at both design and off-design throat Mach numbers with good aerodynamic performance. A comparison of inlet noise at quasi-static and forward-speed conditions in the wind tunnel showed a reduction in the fan tones, demonstrating the flight cleanup effect. High angles of attack produced slight increases in fan noise at the high acoustic directivity angles.

Falarski, M. D.↗
NASA NTRS1980

Inlet contour and flow effects on radiation

An experimental investigation of sound radiation from inlets with different contours with and without flow is being conducted to study the possibility of reducing noise radiated by aircraft engines. For each inlet configuration, complex directivity patterns and complex pressure reflection coefficients are measured as a function of a single space-time structure of the wave (up to a frequency of 4000Hz and an azimuthal wave number 6) and of flow velocity (up to Mach number 0.4) in a cylindrical duct located downstream the inlet. Experimental results of radiation from an unflanged duct are compared with theory. Effect of inlet contour and flow are deduced by comparing respectively unflanged duct and bellmouth measurements and, no flow and flow measurements with the bellmouth. Results are presented which indicate that the contour effect is significant near the cut-on frequency of a mode and emphasize the necessity for taking into account the inlet geometry in a radiation prediction. These results show also that internal flow has a weak effect on the amplitude of the directivity pattern

Ville, J. M.↗
NASA NTRS1980

Some effects of cruise speed and engine matching of supersonic inlet design

An analytical study was conducted to determine the impact of flight Mach number on inlet type selection for a supersonic cruise aircraft. External and mixed-compression axisymmetric and two-dimensional inlets were considered. The internal contraction of the mixed-compression inlets was limited to achieve self-starting. At Mach 2.0, the axisymmetric mixed-compression inlet provided the best aircraft range. At Mach 2.3, the two-dimensional mixed-compression inlet was the most attractive if enough variable geometry were incorporated to minimize spillage during subsonic cruise. Increases in takeoff-to-cruise air flow ratio gave lower aircraft range.

Bangert, L. H.↗
NASA NTRS1979

Quiet Clean Short-haul Experimental Engine (QCSEE); acoustic performance of a 50.8-cm (20 inch) diameter variable pitch fan and inlet, test results and analysis, volume 1

Tests were run both in forward and in reverse thrust modes with a bellmouth inlet, five accelerating inlets (one hard wall and four treated) with a design throat Mach number of 0.79 at the takeoff condition, and four low Mach inlets (one hard wall and three treated) with a design throat Mach number of 0.6 at the takeoff condition. Unsuppressed and suppressed inlet radiated noise levels were measured at conditions representative of QCSEE takeoff, approach, and reverse thrust operations. Measured aerodynamic performance of the accelerating inlet is also included. The test objectives, facility, configurations, are described as well as the data analysis, results, and comparisons.

Bilwakesh, K. R.↗
NASA NTRS1981

Aerodynamic and acoustic behavior of a YF-12 inlet at static conditions

An aeroacoustic test program was performed with a YF-12 aircraft at ground static conditions. The objective was to collect acoustic and aerodynamic data that could determine the cause of YF-12 inlet noise suppression observed earlier. The results showed that the far-field noise level was lower with the YF-12 inlet than with a bellmouth inlet at engine speeds above 5500 rpm. The differences were about 5 PNdB to 11 PNdB, depending on YF-12 inlet configuration and on engine speed. Measurements showed that YF-12 inlet noise suppression was not caused by flow choking. The spike support struts were probably responsible, as in that region the spectral peak near the blade passing frequency disappeared between 6000 and 6600 rpm, and multiple pure tones were greatly reduced.

Bangert, L. H.↗
NASA NTRS1982

A summary of V/STOL inlet analysis methods

The methods used to analyze the aerodynamic performance of V/STOL inlets at the NASA Lewis Research Center are briefly described. Recent extensions and applications of the method are emphasized. They include the specification of the Kutta condition for a slotted inlet, the calculation of suction and tangential blowing for boundary layer control, and the analysis of auxiliary inlet geometries. A comparison is made with experiment for the slotted inlet and also for tangential blowing. Finally, an optimum inlet diffuser velocity distribution is developed.

Hwang, D. P.↗
NASA NTRS1984

Inlet flow field investigation. Part 1: Transonic flow field survey

A wind tunnel investigation was conducted to determine the local inlet flow field characteristics of an advanced tactical supersonic cruise airplane. A data base for the development and validation of analytical codes directed at the analysis of inlet flow fields for advanced supersonic airplanes was established. Testing was conducted at the NASA-Langley 16-foot Transonic Tunnel at freestream Mach numbers of 0.6 to 1.20 and angles of attack from 0.0 to 10.0 degrees. Inlet flow field surveys were made at locations representative of wing (upper and lower surface) and forebody mounted inlet concepts. Results are presented in the form of local inlet flow field angle of attack, sideflow angle, and Mach number contours. Wing surface pressure distributions supplement the flow field data.

Yetter, J. A.↗
NASA NTRS1984

An experimental study of high contraction ratio, subsonic wind tunnel inlets

The inlet or contraction section has significant impact on the performance and operating characteristics of any subsonic wind tunnel. Previous experimental studies have been conducted to examine specific aspects of inlet performance and design. This work builds on this earlier experience by performing a comprehensive experimental analysis of a member of a family of high contraction ratio inlets used on indraft type wind tunnels. Quantitative flow field measurements were made using wall static ports, a five-hole pressure probe, and a hot wire anemometry system. Smoke flow visualization techniques were used to examine the inlet flow in a more qualitative manner and to correlate with quantitative measurements. This experimental investigation has provided insight into some of the many problems associated with inlet flows.

Caylor, M. J.↗
NASA NTRS1984

Numerical simulation of two-dimensional inlet flowfields

Inlet flowfields for airbreathing missiles are calculated by a two-dimensional computational method. A supersonic freestream is assumed to allow the forebody calculation to be uncoupled from the inlet calculation. The inlet calculation employs an implicit, time-marching, finite difference procedure to solve the Euler equations formulated in body-fitted coordinates. The method can be used for a flowfield with both subsonic and supersonic regions and is found to converge rapidly for supercritical inlet operation. For subcritical inlet operation, however, convergence to steady state is slow.

Biringen, S.↗
NASA NTRS1984

Inlet boundary layer effects in an axial compressor rotor. I - Blade-to-blade effects

This paper discusses experimental data measured on the blading and downstream of an isolated compressor rotor with thick inlet endwall boundary layers. The objective of the study was to compare these results with data acquired previously with thin inlet boundary layers and to assess the impact of inlet boundary layer thickness on the secondary flow. Flow visualization results showed the powerful impact of the hub corner stall and how at the same near stall flow coefficient where with thin inlet boundary layers the blade was separated at midspan, with thick inlet boundary layers it was attached. It was also shown that while secondary flow was very weak, it did produce sufficient radial redistribution to cause an apparent negative loss at the blade root.

Wagner, J. H.↗
NASA NTRS1985

Effects of inlet distortion on a static pressure probe mounted on the engine hub in an F-15 airplane

An inlet static pressure (PS2) probe was mounted on the hub of an F100 engine in an F-15 airplane. Flight test results showed that for low distortion conditions, the ratio of engine-face total pressure to static pressure agreed well with previous altitude facility data. Off-schedule operation of the inlet third ramp angle caused increased distortion of the inlet airflow during steady-state flight conditions. Data are shown for inlet third ramp excursions leading to engine stall. The relationships of inlet face total to static pressure ratio as a function of several distortion descriptors are also described.

Hughes, D. L.↗
NASA NTRS1985

Airflow calibration of a bellmouth inlet for measurement of compressor airflow in turbine-powered propulsion simulators

The development of turbine-powered propulsion simulators for high-speed wind tunnel models requires a bellmouth inlet which can accurately measure compressor-inlet airflow. A bellmouth inlet was instrumented with total pressure probes, static pressure probes, and thermocouples for airflow measurement. The bellmouth flowmeter against a critical venturi flowmeter was calibrated. The calibration was done at four inlet pressures ranging from 58 to 114 kPa. The bellmouth discharge coefficient varied as a function of bellmouth-throat Mach number. Over the range of Reynolds number and Mach number tested the Reynolds number was not a significant influence on the discharge coefficient. The overall accuracy of the bellmouth inlet as a flowmeter was estimated to be + or - 0.5% of the flowmeter reading.

Smith, S. C.↗
NASA NTRS1986

Particle trajectory computation on a 3-dimensional engine inlet

A 3-dimensional particle trajectory computer code was developed to compute the distribution of water droplet impingement efficiency on a 3-dimensional engine inlet. The computed results provide the essential droplet impingement data required for the engine inlet anti-icing system design and analysis. The droplet trajectories are obtained by solving the trajectory equation using the fourth order Runge-Kutta and Adams predictor-corrector schemes. A compressible 3-D full potential flow code is employed to obtain a cylindrical grid definition of the flowfield on and about the engine inlet. The inlet surface is defined mathematically through a system of bi-cubic parametric patches in order to compute the droplet impingement points accurately. Analysis results of the 3-D trajectory code obtained for an axisymmetric droplet impingement problem are in good agreement with NACA experimental data. Experimental data are not yet available for the engine inlet impingement problem analyzed. Applicability of the method to solid particle impingement problems, such as engine sand ingestion, is also demonstrated.

Kim, J. J.↗
NASA NTRS1987

Analytical and experimental evaluation of a 3-D hypersonic fixed-geometry, swept, mixed compression inlet

The performance of a fixed-geometry, swept, mixed compression hypersonic inlet is presented. The experimental evaluation was conducted for a Mach number of 6.0 and for several angles of attack. The measured surface pressures and pitot pressure surveys at the inlet throat are compared to computations using a three-dimensional Euler code and an integral boundary layer theory. Unique features of the intake design, including the boundary layer control, insure a high inlet performance. The experimental data show the inlet has a high mass averaged total pressure recovery, a high mass capture and nearly uniform flow diffusion. The swept inlet exhibits excellent starting characteristics, and high flow stability at angle of attack.

Agnone, Anthony M.↗