The Influence of Transient Inlet Distortions on the Instability Inception of a Low-Pressure Compressor in a Turbofan Engine

2000 ◽  
Vol 123 (1) ◽  
pp. 1-8 ◽  
Author(s):  
Dirk C. Leinhos ◽  
Norbert R. Schmid ◽  
Leonhard Fottner
Keyword(s):  
Total Pressure ◽  
Delta Wing ◽  
Stability Limit ◽  
Stability Control ◽  
Control Device ◽  
Inlet Flow ◽  
Stall Inception ◽  
Hypersonic Aircraft ◽  
Surge Margin ◽  
Power Spectral

While studies on compressor flow instabilities under the presence of inlet distortions have been carried out with steady distortions in the past, the investigation presented here focuses on the influence of transient inlet distortions as generated by variable geometry engine intakes of super- and hypersonic aircraft on the characteristic and the nature of the instability inception of a LPC. The flow patterns (total pressure distortion with a superimposed co- or counterrotating swirl) of the distortions are adopted from a hypersonic concept aircraft. A LARZAC 04 twin-spool turbofan was operated with transient inlet distortions, generated by a moving delta wing, and steady total pressure distortions starting close to the LPC’s stability limit until it stalled. High-frequency pressure signals are recorded at different engine power settings. Instabilities are investigated with regard to the inception process and the early detection of stall precursors for providing data for a future stability control device. It turned out that the transient distortion does not have an influence on the surge margin of the LPC compared to the steady distortion, but that it changes the nature of stall inception. The pressure traces are analyzed in the time and frequency domain and also with tools like Spatial FFT, Power Spectral Density, and Traveling Wave Energy. A Wavelet Transformation algorithm is applied as well. While in the case of clean inlet flow, the compressor exhibits different types of stall inception depending on the engine speed, stall is always initiated by spike-type disturbances under the presence of steady or transient distortions. Modal disturbances are present in the mid-speed range that do not grow into stall, but rather interact with the inlet flow and produce short length scale disturbances. The obtained early warning times prior to stall are adversely affected by transient distortions in some cases. The problem of appropriate thresholding becomes evident. The best warning times have been acquired using a statistical evaluation of the Wavelet coefficients, which might be promising to apply in a staged active control system. This system could include different phases of detection and actuation depending on the current precursor.

The Influence of Transient Inlet Distortions on the Instability Inception of a Low Pressure Compressor in a Turbofan Engine

2000 ◽  
Author(s):  
Dirk C. Leinhos ◽  
Norbert R. Schmid ◽  
Leonhard Fottner
Keyword(s):  
Total Pressure ◽  
Delta Wing ◽  
Stability Limit ◽  
Travelling Wave ◽  
Stability Control ◽  
Control Device ◽  
Inlet Flow ◽  
Stall Inception ◽  
Surge Margin ◽  
Power Spectral

While studies on compressor flow instabilities under the presence of inlet distortions have been carried out with steady distortions in the past, the investigation presented here focuses on the influence of transient inlet distortions as generated by variable geometry engine intakes of super- and hypersonic aircrafts on the characteristic and the nature of the instability inception of a LPC. The flow patterns (total pressure distortion with a superimposed co- or counter-rotating swirl) of the distortions are adopted from a hypersonic concept aircraft. A LARZAC 04 twin-spool turbofan was operated with transient inlet distortions, generated by a moving delta-wing, and steady total pressure distortions starting close to the LPC’s stability limit until it stalled. High frequency pressure signals are recorded at different engine power settings. Instabilities are investigated with regard to the inception process and the early detection of stall precursors for providing data for a future stability control device. It turned out that the transient distortion does not have an influence on the surge margin of the LPC compared to the steady distortion, but that it changes the nature of stall inception. The pressure traces are analysed in the time and frequency domain and also with tools like Spatial FFT, Power Spectral Density and Travelling Wave Energy. A Wavelet Transformation algorithm is applied as well. While in the case of clean inlet flow the compressor exhibits different types of stall inception depending on the engine speed, stall is always initiated by spike-type disturbances under the presence of steady or transient distortions though modal disturbances are present in the mid speed range that do not grow into stall, but rather interact with the inlet flow and produce short lengthscale disturbances. The obtained early warning times prior to stall are adversely affected by transient distortions in some cases. The problem of appropriate threshholding becomes evident. The best warning times have been acquired using a statistical evaluation of the Wavelet coefficients which might be promising to apply in a staged active control system which could include different phases of detection and actuation depending on the current precursor.

The Effect of Inlet Distortion on the Performance Characteristics of a Centrifugal Compressor

1983 ◽  
Vol 105 (2) ◽  
pp. 223-230 ◽  
Author(s):  
I. Ariga ◽  
N. Kasai ◽  
S. Masuda ◽  
Y. Watanabe ◽  
I. Watanabe
Keyword(s):  
Centrifugal Compressor ◽  
Total Pressure ◽  
Performance Characteristics ◽  
Performance Tests ◽  
Velocity Measurements ◽  
Test Rig ◽  
Low Speed ◽  
Inlet Distortion ◽  
Surge Margin ◽  
The Given

The present paper concerns itself with the effects of total pressure (and thus velocity) distortion on performance characteristics and surge margin of centrifugal compressors. Both radial and circumferential distortions were investigated. The performance tests as well as the velocity measurements within the impeller passages were carried out with a low-speed compressor test rig with the inlet honeycomb as the distortion generators and compared with the case of “no distortion” as a datum. The results indicated that the inlet distortion exerted unfavorable influences on the efficiency and the surge margin of the given compressor, though the influence of the radial distortion was much stronger than that of the circumferential one. Various distortion indices were further examined in order to correlate the performance to the inlet distortion.

Effects of inlet radial distortion on the type of stall precursor in low-speed axial compressor

2016 ◽  
Vol 232 (1) ◽  
pp. 55-67 ◽  
Author(s):  
Ali Arshad ◽  
Qiushi Li ◽  
Simin Li ◽  
Tianyu Pan
Keyword(s):  
Pressure Fluctuations ◽  
Axial Compressor ◽  
Rotating Stall ◽  
Experimental Investigations ◽  
Inlet Flow ◽  
Blade Loading ◽  
Stall Inception ◽  
Low Speed ◽  
Modal Type ◽  
Stall Precursor

Experimental investigations of the effect of inlet blade loading on the rotating stall inception process are carried out on a single-stage low-speed axial compressor. Temporal pressure signals from the six high response pressure transducers are used for the analysis. Pressure variations at the hub are especially recorded during the stall inception process. Inlet blade loading is altered by installing metallic meshed distortion screens at the rotor upstream. Three sets of experiments are performed for the comparison of results, i.e. uniform inlet flow, tip, and hub distortions, respectively. Regardless of the type of distortion introduced to the inflow, the compressor undergoes a performance drop, which is more severe in the hub distortion case. Under the uniform inlet flow condition, stall inception is caused by the modal type disturbance while the stall precursor switched to spike type due to the highly loaded blade tip. In the presence of high blade loading at the hub, spike disappeared and the compressor once again witnessed a modal type disturbance. Hub pressure fluctuations are observed throughout the process when the stall is caused by a modal wave while no disturbance is noticed at the hub in spike type stall inception. It is believed that the hub flow separation contributes to the modal type of stall inception phenomenon. Results are also supported by the recently developed signal processing techniques for the stall inception study.

Increasing Inducer Stability and Suction Performance With a Stability Control Device

2018 ◽  
Vol 141 (1) ◽  
Author(s):  
R. Lundgreen ◽  
D. Maynes ◽  
S. Gorrell ◽  
K. Oliphant
Keyword(s):  
Fluid Dynamic ◽  
Leading Edge ◽  
High Energy ◽  
Stability Control ◽  
Control Device ◽  
Design Flow ◽  
Flow Coefficient ◽  
Blade Tip ◽  
Rotordynamic Forces ◽  
Suction Performance

An inducer is used as the first stage of high suction performance pump. It pressurizes the fluid to delay the onset of cavitation, which can adversely affect performance in a centrifugal pump. In this paper, the performance of a water pump inducer has been explored with and without the implementation of a stability control device (SCD). This device is an inlet cover bleed system that removes high-energy fluid near the blade leading edge and reinjects it back upstream. The research was conducted by running multiphase, time-accurate computational fluid dynamic (CFD) simulations at the design flow coefficient and at low, off-design flow coefficients. The suction performance and stability for the same inducer with and without the implementation of the SCD has been explored. An improvement in stability and suction performance was observed when the SCD was implemented. Without the SCD, the inducer developed backflow at the blade tip, which led to rotating cavitation and larger rotordynamic forces. With the SCD, no significant cavitation instabilities developed, and the rotordynamic forces remained small. The lack of cavitation instabilities also allowed the inducer to operate at lower inlet pressures, increasing the suction performance of the inducer.

Stall inception mechanisms in a contra-rotating fan operating at different speed combinations

2019 ◽  
Vol 234 (8) ◽  
pp. 1041-1052 ◽  
Author(s):  
MP Manas ◽  
AM Pradeep
Keyword(s):  
Pressure Ratio ◽  
Pressure Sensors ◽  
Stability Limit ◽  
Leading Edge ◽  
Axial Direction ◽  
Tip Leakage Flow ◽  
Stall Inception ◽  
Unsteady Pressure ◽  
Stall Cells ◽  
The Stability

Contra-rotating fan is a concept that can possibly replace the present-day conventional fans due to its several aerodynamic advantages. It has the potential to improve the stability limit and can achieve a higher pressure ratio per stage. One of the advantages of a contra-rotating fan is its capability to operate both the rotors at different speeds. In the present study, experiments are carried out at different speed combinations of the rotors and the stall inception phenomenon is captured using high-response unsteady pressure sensors placed on the casing upstream of the leading edge of rotor-1. The unsteady pressure data are investigated using wavelet and Fourier analysis techniques. It is observed that the mechanism of stall inception is different for different speed combinations. The pre-stall disturbances fall in different frequency ranges for different speed combinations. For the range of speed combinations investigated, the frequency of appearance of stall cells of rotor-1 does not depend on the speed of rotor-2. A higher speed of rotation of rotor-1 leads to a higher frequency of appearance of stall cells and a lower speed of rotation of rotor-1 leads to a lower frequency of appearance of stall cells. For all the speed combinations, there is a range of frequency where no disturbance is observed and this range is termed as the ‘no-disturbance zone’. Disturbances are observed at lower frequencies and at frequencies close to the blade passing frequency. In order to understand the flow physics in detail, computational analysis is carried out for different speed combinations of the rotors. For a higher speed of rotor-2, it is observed that the suction effect of rotor-2 is significant enough to pull the tip-leakage flow towards the axial direction. Thus, the suction effect of rotor-2 plays a significant role in determining the stall of the stage.

scholarly journals Experimental Investigation of Inlet Distortion Effect on Performance of a Micro Gas Turbine

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Alireza Naseri ◽  
Shervin Sammak ◽  
Masoud Boroomand ◽  
Alireza Alihosseini ◽  
Abolghasem M. Tousi
Keyword(s):  
Gas Turbine ◽  
Total Pressure ◽  
Nonuniform Flow ◽  
Inlet Flow ◽  
Micro Gas Turbine ◽  
Inlet Distortion ◽  
Air Jet ◽  
Measuring Devices ◽  
Turbine Performance ◽  
Distortion Effect

An experimental study has been carried out to determine how inlet total-pressure distortion affects the performance of a micro gas turbine. An inlet simulator is designed and developed to produce and measure distortion patterns at the inlet to the gas turbine. An air jet distortion generator (AJDG) is used to produce nonuniform flow patterns and total pressure probes are installed to measure steady-state total-pressure distribution at the inlet. A set of wind tunnel tests have been performed to confirm the fidelity of distortion generator and measuring devices. Tests are carried out with the gas turbine exposed to inlet flow with 60 deg, 120 deg, and 180 deg circumferential distortion patterns with different distortion intensities. The performance of the gas turbine has been measured and compared with that of clean inlet flow case. Results indicate that the gas turbine performance can be affected significantly facing with intense inlet distortions.

Sign in / Sign up

Export Citation Format

Share Document