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At least 73 records · Page 4

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NASA NTRS1976

Modeling and analysis of the TF30-P-3 compressor system with inlet pressure distortion

Circumferential inlet distortion testing of a TF30-P-3 afterburning turbofan engine was conducted at NASA-Lewis Research Center. Pratt and Whitney Aircraft analyzed the data using its multiple segment parallel compressor model and classical compressor theory. Distortion attenuation analysis resulted in a detailed flow field calculation with good agreement between multiple segment model predictions and the test data. Sensitivity of the engine stall line to circumferential inlet distortion was calculated on the basis of parallel compressor theory to be more severe than indicated by the data. However, the calculated stall site location was in agreement with high response instrumentation measurements.

Mazzawy, R. S.↗

NASA NTRS1975

Estimating maximum instantaneous distortion from inlet total pressure rms and PSD measurements

An inexpensive method is developed to determine the extreme values of instantaneous inlet distortion. This method also provides insight into the basic mechanics of unsteady inlet flow and the associated engine reaction. The analysis is based on fundamental fluid dynamics and statistical methods to provide an understanding of the turbulent inlet flow and quantitatively relate the rms level and power spectral density (PSD) function of the measured time variant total pressure fluctuations to the strength and size of the low pressure regions. The most probable extreme value of the instantaneous distortion is then synthesized from this information in conjunction with the steady state distortion. Results of the analysis show the extreme values to be dependent upon the steady state distortion, the measured turbulence rms level and PSD function, the time on point, and the engine response characteristics. Analytical projections of instantaneous distortion are presented and compared with data obtained by a conventional, highly time correlated, 40 probe instantaneous pressure measurement system.

Melick, H. C., Jr.↗

NASA NTRS1986

Statistical prediction of dynamic distortion of inlet flow using minimum dynamic measurement. An application to the Melick statistical method and inlet flow dynamic distortion prediction without RMS measurements

The Melick method of inlet flow dynamic distortion prediction by statistical means is outlined. A hypothetic vortex model is used as the basis for the mathematical formulations. The main variables are identified by matching the theoretical total pressure rms ratio with the measured total pressure rms ratio. Data comparisons, using the HiMAT inlet test data set, indicate satisfactory prediction of the dynamic peak distortion for cases with boundary layer control device vortex generators. A method for the dynamic probe selection was developed. Validity of the probe selection criteria is demonstrated by comparing the reduced-probe predictions with the 40-probe predictions. It is indicated that the the number of dynamic probes can be reduced to as few as two and still retain good accuracy.

Schweikhard, W. G.↗

NASA NTRS1979

Reynolds number, scale and frequency content effects on F-15 inlet instantaneous distortion

An inlet instantaneous distortion study program sponsored by NASA was recently completed using an F-15 fighter aircraft. Peak distortion data from subscale inlet model wind tunnel tests are shown to be representative of full-scale flight test peak distortion. The effects on peak distortion are investigated for engine presence, Reynolds number, scale and frequency content. Data are presented which show that: (1) the effect of engine presence on total pressure recovery, peak distortion, and turbulence is small but favorable, (2) increasing the Reynolds number increases total pressure recovery, decreases peak distortion, and decreases turbulence, and (3) increasing the filter cutoff frequency increases the calculated values of both peak distortion and turbulence.

Stevens, C. H.↗

NASA NTRS1974

Some comparisons of the flow characteristics of a turbofan compressor system with and without inlet pressure distortion

The measured effects of a circumferential distortion in inlet total pressure on the fan, low, and high compressor of an afterburning turbofan engine are presented and discussed. Extensive inner-stage instrumentation, combined with a unique test technique offered an accurate means of measuring the shifts in flow, performance, and stall mechanisms within the compressor. These effects are compared at one speed to the corresponding effects measured with undistorted inlet flow. The results show the rate at which the distorted flow areas were attenuated and rotated as well as the change in flow velocities that occurred at various points in the compressor. High response pressure traces indicated the location of stalls including the sequence of dynamic events from the onset and propagation of various stall-recovery events, to compressor surge, to the resulting hammershock.

Evans, D. G.↗

NASA NTRS1974

Some comparisons of the flow characteristics of a turbofan compressor system with and without inlet pressure distortion

The measured effects of a circumferential distortion in inlet total pressure on the fan, low, and high compressor of an afterburning turbofan engine are presented and discussed. Extensive inner-stage instrumentation, combined with a unique test technique offered an accurate means of measuring the shifts in flow, performance, and stall mechanisms within the compressor. These effects are compared at one speed to the corresponding effects measured with undistorted inlet flow. The results show the rate at which the distorted flow areas were attenuated and rotated, as well as the change in flow velocities that occurred at various points in the compressor. High response pressure traces indicated the location of stalls including the sequence of dynamic events from the onset and propagation of various stall-recovery events, to compressor surge, to the resulting hammershock.

Evans, D. G.↗

NASA NTRS1985

Effect of Steady-State Temperature Distortion on Inlet Flow to a High-Bypass-Ratio Turbofan Engine

The effects of circumferential inlet temperature distortion on the flow characteristics between a distortion generator and a high bypass ratio turbofan engine and through its compression system were evaluated to support the effort to generate analytical models. The flow characteristics are defined by the inlet duct, the flow angles, and the total temperature, total pressure, and static pressure profiles in the inlet duct and through the fan and compressor. The effects of Reynolds number, rotor speed, and distortion extent are also considered.

Soeder, R. H.↗

NASA NTRS1982

Effect of steady-state pressure distortion on inlet flow to a high-bypass-ratio turbofan engine

Static pressure and total pressure distributions were measured in the inlet duct upstream of the engine inlet and within the fan and compressor of a YTF34 turbofan engine. In addition, the free stream flow angle was measured between the distortion generator and the engine inlet. Distortions were generated using three screen configurations with extents of 90 deg or 180 deg. The screens were mounted on a rotatable screen assembly. Reynolds number index upstream of the distortion device was maintained at 0.5 or 0.2, and engine fan speed corrected to station 2 temperature was maintained at 80 or 90 percent of rated condition (7005 rpm). Flow angle was nearly constant near the distortion device and increased as flow approached the engine inlet. The largest flow angle occurred in the hub region of the engine inlet. Static pressure distortion along the inlet duct increased exponentially as the flow approached the engine. Both static pressure and total pressure distortions were attenuated between engine inlet and compressor exit.

Soeder, R. H.↗

NASA NTRS1979

Effect of steady-state temperature distortion and combined distortion on inlet flow to a turbofan engine

Flow angle, static pressure, total temperature and total pressure were measured in the inlet duct upstream of a turbofan engine operating with temperature distortion or combined pressure-temperature distortion. Such measurements are useful in the evaluation of analytical models of inlet distortion. A rotating gaseous-hydrogen burner and a circumferential 180 degrees-extent screen configuration mounted on a rotatable assembly generated the distortions. Reynolds number index was maintained at 0.5 and engine corrected low-rotor speeds were held at 6000 and 8600 rpm. The measurements showed that at the entrance to the engine, flow angle was largest in the hub region. As flow approached the engine, yaw angle (circumferential variation) increased and pitch angle (radial variation) decreased. The magnitude of static-pressure distortion measured along the inlet-duct and extended bullet nose walls increased exponentially as flow approached the engine.

Soeder, R. H.↗

NASA NTRS1977

Internal flow characteristics of a multistage compressor with inlet pressure distortion

The measured distribution of compressor interstage pressures and temperatures resulting from a 180 deg inlet-total-pressure distortion for a J85-13 turbojet engine is reported. Extensive inner stage instrumentation combined with stepwise rotation of the inlet distortion gave data of high circumferential resolution. The steady-state pressures and temperatures along with the amplitude, extent, and location of the distorted areas are given. Data for 80, 90, and 100 percent of rotor design speed are compared with clean (undistorted) inlet flow conditions to show pressure and temperature behavior within the compressor. Both overall and stagewise compressor performances vary only slightly when clean and distorted inlet conditions are compared. Total and static pressure distortions increase in amplitude in the first few stages of the compressor and then attenuate fairly uniformly to zero at the discharge. Total-temperature distortion induced by the pressure distortion reached a maximum amplitude by the first two stages and decayed only a little through the rest of the compressor. Distortion amplitude tended to peak in line with the screen edges, and, except for total and static pressure in the tip zone, there was little swirl in the axial direction.

Debogdan, C. E.↗

NASA NTRS1955

Preliminary Results of the Determination of Inlet-Pressure Distortion Effects on Compressor Stall and Altitude Operating Limits of the J57-P-1 Turbojet Engine

During an investigation of the J57-P-1 turbojet engine in the Lewis altitude wind tunnel, effects of inlet-flow distortion on engine stall characteristics and operating limits were determined. In addition to a uniform inlet-flow profile, the inlet-pressure distortions imposed included two radial, two circumferential, and one combined radial-circumferential profile. Data were obtained over a range of compressor speeds at an altitude of 50,000 and a flight Mach number of 0.8; in addition, the high- and low-speed engine operating limits were investigated up to the maximum operable altitude. The effect of changing the compressor bleed position on the stall and operating limits was determined for one of the inlet distortions. The circumferential distortions lowered the compressor stall pressure ratios; this resulted in less fuel-flow margin between steady-state operation and compressor stall. Consequently, the altitude operating Limits with circumferential distortions were reduced compared with the uniform inlet profile. Radial inlet-pressure distortions increased the pressure ratio required for compressor stall over that obtained with uniform inlet flow; this resulted in higher altitude operating limits. Likewise, the stall-limit fuel flows required with the radial inlet-pressure distortions were considerably higher than those obtained with the uniform inlet-pressure profile. A combined radial-circumferential inlet distortion had effects on the engine similar to the circumferential distortion. Bleeding air between the two compressors eliminated the low-speed stall limit and thus permitted higher altitude operation than was possible without compressor bleed.

Wallner, L. E.↗

NASA NTRS1990

Sea level static calibration of a compact multimission aircraft propulsion simulator with inlet flow distortion

Wind tunnel tests of propulsion-integrated aircraft models have identified inlet flow distortion as a major source of compressor airflow measurement error in turbine-powered propulsion simulators. Consequently, two Compact Multimission Aircraft Propulsion Simulator (CMAPS) units were statically tested at sea level ambient conditions to establish simulator operating performance characteristics and to calibrate the compressor airflow against an accurate bellmouth flowmeter in the presence of inlet flow distortions. The distortions were generated using various-shaped wire mesh screens placed upstream of the compressor. CMAPS operating maps and performance envelopes were obtained for inlet total pressure distortions (ratio of the difference between the maximum and minimum total pressures to the average total pressure) up to 35 percent, and were compared to baseline simulator operating characteristics for a uniform inlet. Deviations from CMAPS baseline performance were attributed to the coupled variation of both compressor inlet-flow distortion and Reynolds number index throughout the simulator operating envelope for each screen configuration. Four independent methods were used to determine CMAPS compressor airflow; direct compressor inlet and discharge measurements, an entering/exiting flow-balance relationships, and a correlation between the mixer pressure and the corrected compressor airflow. Of the four methods, the last yielded the least scatter in the compressor flow coefficient, approximately + or - 3 percent over the range of flow distortions.

Won, Mark J.↗

NASA NTRS1973

Analysis of inlet flow distortion and turbulence effects on compressor stability

The effect of steady state circumferential total pressure distortion on the loss in compressor stall pressure ratio has been established by analytical techniques. Full scale engine and compressor/fan component test data were used to provide direct evaluation of the analysis. Specifically, since a circumferential total pressure distortion in an inlet system will result in unsteady flow in the coordinate system of the rotor blades, analysis of this type distortion must be performed from an unsteady aerodynamic point of view. By application of the fundamental aerothermodynamic laws to the inlet/compressor system, parameters important in the design of such a system for compatible operation have been identified. A time constant, directly related to the compressor rotor chord, was found to be significant, indicating compressor sensitivity to circumferential distortion is directly dependent on the rotor chord.

Melick, H. C., Jr.↗

NASA NTRS1948

Effect of Inlet Air Distortion on the Steady-State and Surge Characteristics of an Axial-Flow Turbojet Compressor

An investigation was conducted in an altitude test chamber to determine the effects of inlet airflow distortion on the compressor steady-state and surge characteristics of a high-pressure ratio, axial-flow turbojet engine. Circumferential-type inlet flow distortions were investigated, which covered a range of distortion sector angles from 20 deg to 168 deg and distortion levels up to 22 percent. The presence of inlet airflow distortions at the compressor face resulted in a substantial increase in the local pressure ratio in the distorted region, primarily for the inlet stages. The local pressure ratio in the distorted region for the inlet stages increased as either the distortion sector angle decreased or the percent distortion increased. The average compressor-surge pressure ratio was much more sensitive to inlet airflow distortions at lower engine speeds than at engine speeds near rated. Hence, compressor-surge margin reduction due to inlet airflow distortion was quite severe at the lower engine speeds. Although the average compressor-surge pressure ratio was generally reduced with inlet flow distortion, local pressure ratios across the distorted sector of the compressor were obtained during surge and were significantly greater than the normal compressor-surge pressure ratio. This was a result of increased loading of the inlet stages in the distorted region.

Ciepluch, Carl C.↗

NASA NTRS1999

Inlet Flow Distortion and Unsteady Blade Response in a Transonic Axial-Compressor Rotor

This paper describes the unsteady blade surface pressures on the first-stage rotor blades of a two-stage transonic axial flow compressor experiencing inlet flow distortion. This study was conducted to demonstrate the ability of a full annulus unsteady Reynolds-averaged Navier-Stokes numerical technique to predict unsteady pressures on the rotor blades operating in a distorted inflow. A total pressure distortion produced by a variable mesh screen mounted near the inlet was used to excite the unsteady blade loading on the rotor. On-blade pressure transducers were used to measure the unsteady blade surface pressure. These pressures and the resulting transient load on the rotor blades were compared to the numerical prediction. It is important to develop numerical techniques to predict these transient loads to better understand the response of compressor blades to forcing functions. With this enhanced understanding and ability to predict these transient forces, more robust compressors can be developed. In the study, a high definition of the inlet flow distortion was achieved by rotating the distortion screens. In this manner the inlet flow distortion and the distortion at the first stage stator leading edge were measured at approximately every 0.7 degrees. This full annulus high definition of the inlet flow distortion was used as the inlet boundary condition for the numerical technique. The experimental measurements and numerical analyses are highly complementary in this study. Detailed comparisons between the measurements and the numerical analyses indicate that the current numerical procedure calculates the unsteady aerodynamic pressure on the blade surfaces reasonably well. Further, the agreement of the measured and predicted rotor exit flow distortion at the first stage stator leading edge provides verification of the numerical technique.

Rabe, D. C.↗

NASA NTRS1983

Inlet flow distortion in turbomachinery - Comparison of theory and experiment in a transonic fan stage

Consideration is given to both velocity and temperature circumferential inlet distortions at upstream infinity (Seidel et al., 1980). The blade rows here are modeled as semiactuator disks, and losses and quasi-steady deviation angle correlations are included in the analysis. The governing equations are linearized, and the perturbations in stagnation pressure and stagnation temperature at upstream infinity are represented as Fourier series. The flow in the rotor is modeled as inviscid, one-dimensional, unsteady, and compressible. the flow is steady elsewhere. The deviation angles for the rotor and stator are taken to be functions of the relative inlet angle and Mach number, and use is made of the correlations contained in Johnson and Bullock (1965). It is assumed that the losses in relative stagnation pressure in the rotor and stator occur across the trailing edge. Boundary conditions applied at the various stations furnish the equations that make it possible to solve for the several quantities introduced in the linearization of the governing equations.

Seidel, B. S.↗

NASA NTRS1975

Effect of a 180 deg-extent inlet pressure distortion on the internal flow conditions of a TF30-P-3

The measured effects of inlet pressure distortion on the internal flow temperatures and pressures of a TF30-P-3 afterburning turbofan engine are reported. Extensive inner-stage instrumentation combined with stepwise rotation of pressure distortion provided a high degree of circumferential resolution in the data. The steady-state spatial variation in pressures, temperature, and calculated flow velocity and the amplitude and extent of the distorted sectors are given. Data are presented for runs of 77 and 90 percent of low-speed-rotor design speed at pressure distortion levels two-thirds of that required to stall the engine. These data are compared with data taken at clean-inlet conditions. Results indicate that the inlet pressure distortion was quickly attenuated within the compressor, except at the hub of the low-pressure compressor. The distorted sectors also swirled and varied in extent as they passed through the engine. Average velocities within the compressor were about equal to the clean-inlet values.

Debogdan, C. E.↗

NASA NTRS1983

Literature search of publications concerning the prediction of dynamic inlet flow distortion and related topics

Publications prior to March 1981 were surveyed to determine inlet flow dynamic distortion prediction methods and to catalog experimental and analytical information concerning inlet flow dynamic distortion prediction methods and to catalog experimental and analytical information concerning inlet flow dynamics at the engine-inlet interface of conventional aircraft (excluding V/STOL). The sixty-five publications found are briefly summarized and tabulated according to topic and are cross-referenced according to content and nature of the investigation (e.g., predictive, experimental, analytical and types of tests). Three appendices include lists of references, authors, organizations and agencies conducting the studies. Also, selected materials summaries, introductions and conclusions - from the reports are included. Few reports were found covering methods for predicting the probable maximum distortion. The three predictive methods found are those of Melick, Jacox and Motycka. The latter two require extensive high response pressure measurements at the compressor face, while the Melick Technique can function with as few as one or two measurements.

Schweikhhard, W. G.↗