The Effect of Speed Ratio on the First Rotating Stall Stage in Contra-Rotating Compressor

2012 ◽  
Author(s):  
Limin Gao ◽  
Xiaojun Li ◽  
Jian Xie ◽  
Bo Liu
Keyword(s):  
Weight Ratio ◽  
Aircraft Engine ◽  
Work Conditions ◽  
Rotating Stall ◽  
Speed Ratio ◽  
Stall Margin ◽  
Rotating Speed ◽  
Tip Leakage ◽  
Important Approach ◽  
The Impact

Since the structure and aerodynamic advantages of contra-rotating technology, it has been considered as an important approach to further improve the thrust-weight ratio of aircraft engine. In the present work, the impact of rotating speed ratio on the first rotating stall stage of a CRAC which consist of two counter-rotating rotors is investigated numerically. To detect the stall margin of CRAC exactly, the back pressure dichotomy method is developed, the grid indepence is verified and the performance is measured. A large number computation is carried out to explore the influence of rotating speed ratio on the performance of contra-rotating compressor. Finally the flow filed near blade tip is analyzed to find the relation between the rotating speed ratio and the first stall rotor. The result shows: (1) The work conditions of ROT1 have a significant impact on the aerodynamic performance of ROT2, while ROT2 play a little impact on the performance of ROT1. (2) At the condition of rotating speed ratio R2:R1≥0.9, the second rotor will be the first stall stage as the mass flow is decreased. (3) When the ROT2 rotating speed is slower than the ROT1, the intensity of tip leakage in ROT2 declines obviously with decreasing the rotating speed ratio, but the intensity of tip leakage in ROT1 has little changes. At the condition of R2:R1<0.9, the first rotor will be the first stall stage.

The Effect of Tip Clearance on the Performance of Contra-Rotating Compressor

2012 ◽  
Author(s):  
Limin Gao ◽  
Xiaojun Li ◽  
Xudong Feng ◽  
Bo Liu
Keyword(s):  
Pressure Ratio ◽  
Weight Ratio ◽  
Aircraft Engine ◽  
Back Pressure ◽  
Tip Clearance ◽  
Stall Margin ◽  
Operating Range ◽  
Important Approach ◽  
The Impact ◽  
Wide Operating

Contra-rotating technology has been considered as an important approach to further improve the thrust-weight ratio of aircraft engine because of its structure and aerodynamic superiority. In the present work, the impact of tip clearance on the performance of a CRAC which consist of two counter-rotating rotors is investigated numerically. To detect the stall margin of CRAC exactly, the back pressure dichotomy method is developed, the grid indepence is verified and the performance is measured. A large number computation is carried out to explore the influence of tip clearance on the operating range of contra-rotating compressor. Finally the flow filed near the tip clearance is analyzed to find the relation between the tip clearance and the first stall rotor. The result shows: (1) Efficiency and pressure ratio decrease with the tip clearance size increased, but there is an optimal tip clearance size corresponding to a relative wide operating range. (2) The first stall stage of contra-rotating compressor varies with the tip clearance size increases. For the present CRAC, ROT2 is the first stall stage with the tip clearance size no greater than 0.5mm, while the ROT1 is the first stall stage if the tip clearance size greater than 0.5mm.

Numerical analysis of the effects of circumferential groove casing suction in a counter-rotating axial flow compressor

2020 ◽  
pp. 095765092095169
Author(s):  
Tian Liang ◽  
Bo Liu ◽  
Stephen Spence ◽  
Liying Jiao
Keyword(s):  
Axial Flow ◽  
Main Flow ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Stall Margin ◽  
Tip Leakage ◽  
Axial Flow Compressor ◽  
Circumferential Groove ◽  
Flow Compressor ◽  
The Impact

To extend the current understanding of the circumferential groove casing suction applied to a counter-rotating axial flow compressor, the impact of different axial locations of the circumferential suction groove on the characteristics of the tip leakage flow (TLF) and the corresponding physical mechanisms producing the stability enhancement have been studied based on validated numerical simulations. The results show that the optimal location for the suction groove is at around 20% axial chord, which demonstrated a high potential for reducing additional stall mass flow coefficient with about 8.4% increment in the stall margin. After the casing suction groove was applied, the interface between the incoming main flow and TLF was pushed significantly downstream in the second rotor. The blade loading in the region below the groove, the tip leakage flow angle and the reversed axial momentum flux injected into main flow passage through the tip gap were all reduced, which contributed to the stall margin improvement. Detailed analysis of the tip leakage flow structures showed that the TLF originating from different chord locations played different roles in the stall inception process. It was found to be more effective to improve stall margin and adiabatic efficiency by controlling the front part of the TLF, which was most sensitive.

Active Compressor Stability Management via a Stall Margin Control Mode

2009 ◽  
Author(s):  
Yuan Liu ◽  
Manuj Dhingra ◽  
J. V. R. Prasad
Keyword(s):  
Pressure Fluctuations ◽  
Aircraft Engine ◽  
Rotating Stall ◽  
Control Mode ◽  
Engine Control ◽  
Correlation Measure ◽  
Stall Margin ◽  
Engine Control System ◽  
Compressor Rotor ◽  
Margin Control

An active engine control scheme for protection against compressor instabilities such as rotating stall and surge is presented. Compressor stability detection is accomplished via a parameter known as the correlation measure, which quantifies the repeatability of the pressure fluctuations in the tip region of a compressor rotor. This work investigates the integration of the correlation measure with an aircraft engine control system through the use of a stall margin control mode. The development and implementation of the stall margin mode is described. The effectiveness of the overall active control framework—an active compressor stability management system—is assessed using a computer simulation of a high-bypass, dual-spool, commercial-type turbofan engine.

Numerical Investigation on Slot Casing Treatment in a Transonic Axial Compressor Stage: Part 1 — Casing Treatment Design

2016 ◽  
Author(s):  
Mingmin Zhu ◽  
Xiaoqing Qiang ◽  
Jinfang Teng
Keyword(s):  
Axial Compressor ◽  
Leakage Flow ◽  
Compressor Stage ◽  
Tip Leakage Flow ◽  
Suction Surface ◽  
Stall Margin ◽  
Rotating Speed ◽  
Casing Treatment ◽  
Tip Leakage ◽  
Stall Margin Improvement

Slot-type casing treatment generally has a great potential of enhancing the operating range for tip-critical compressor rotors, however, with remarkable efficiency drop. Part I of this two-part paper was committed to develop a slot configuration with desired stall margin improvement and minimized efficiency loss. Steady simulation was carried out in a 1.5 transonic axial compressor stage at part design rotating speed. At this rotating speed this compressor stage operated at a subsonic condition and showed a rather narrow operating range, which needed to be improved badly. Flow fields analysis at peak efficiency and near stall point showed that the development of tip leakage vortex and resulting blockage near casing resulted in numerical stall. Three kinds of skewed slots with same rotor exposure and casing porosity were designed according to the tip flow field and some empirical strategies. Among three configurations, arc-curved skewed slot showed minimum peak efficiency drop with considerable stall margin improvement. Then rotor exposure and casing porosity were varied based on the original arc-curved skewed slot, with a special interest in detecting their impact on the compressor stability and overall efficiency. Result showed that smaller rotor exposure and casing porosity leaded to less efficiency drop. But meanwhile, effectiveness of improving compressor stability was weakened. The relation between efficiency drop and stall margin improvement fell on a smooth continuous curve throughout all slots configurations, indicating that the detrimental effect of casing treatment on compressor was inevitable. Flow analysis was carried out for cases of smooth casing and three arc-curved configurations at smooth casing near stall condition. The strength of suction/injection, tip leakage flow behavior and removal of blockage near casing were detailed examined. Larger rotor tip exposure and slots number contributed to stronger injection flow. The loss generated within the mixing process of injection flow with main flow and leakage flow is the largest source of entropy increase. Further loss mechanisms were interpreted at eight axial cuts, which were taken through the blade row and slots to show the increase in entropy near tip region. Entropy distributions manifested that loss generations with smooth casing were primarily ascribed to low-momentum tip leakage flow/vortex and suction surface separation at leading edge. CU0 slot, the arc-curved slots with 50% rotor tip exposure, was capable of suppressing the suction surface separation loss. Meanwhile, accelerated tip leakage flow brought about additional loss near casing and pressure surface. Upstream high entropy flow would be absorbed into the rear portion of slots repeatedly, resulting in further loss.

Investigation of Passage Flow Features in a Transonic Compressor Rotor With Casing Treatments

2011 ◽  
Author(s):  
M. W. Mu¨ller ◽  
H.-P. Schiffer ◽  
Melanie Voges ◽  
Chunill Hah
Keyword(s):  
Measurement Techniques ◽  
Stability Limit ◽  
Rotating Stall ◽  
Tip Leakage Flow ◽  
Stall Margin ◽  
Tip Leakage ◽  
Operating Range ◽  
Transonic Compressor ◽  
The Stability ◽  
Casing Treatments

An experimental investigation on casing treatments in a one-stage transonic compressor is presented. The reference case consists of a radially staggered blisk and six circumferential grooves. Speedlines show that this axisymmetric treatment already provided a substantial increase in operating range with relatively small losses in efficiency. Since the onset of rotating stall in tip-critical high-speed compressors is always linked to the tip-leakage flow and the build-up of blockage within the blade passage. High-resolution measurement techniques have been employed to investigate the corresponding effects. Results with Particle Image Velocimetry show that the interaction between the tip leakage vortex and the shock front cause a blockage area. When throttled further, the blockage increases. The shock structure changes similar to the phenomena of vortex breakdown described by different researchers in the past, but a stagnation point is not present. Before reaching the stability limit, the interface line between the incoming flow and the blocked area moves towards the inlet plane of the rotor indicating spike-type stall inception. Wall pressure measurements confirmed this theory for the smooth wall, but with circumferential grooves applied, a part span stall cell develops prior to the stability limit. In order to assess the performance of circumferential grooves, two additional configurations are presented. The corresponding measurements addressed the questions whether circumferential grooves also provide an operating range extension when applied to an optimized rotor design with higher initial stall margin. Therefore, an identical casing treatment is applied to a forward swept rotor. The second question is, how circumferential grooves perform in direct comparison to a non-axisymmetric endwall structure. Axial slots have been applied to the radially staggered rotor. While the stall margin exceeds all other configurations, detrimential effects in efficiency are observed. A detailed anaylsis of probe data shows the changes of the radial profile at the rotor outlet which allows recommendations for more efficient CT designs. Parameters allowing to evaluate the CT influence are presented.

The Impact of Forward Swept Rotors on Tip-Limited Low-Speed Axial Compressors

2003 ◽  
Author(s):  
G. Scott McNulty ◽  
John J. Decker ◽  
Brent F. Beacher ◽  
S. Arif Khalid
Keyword(s):  
Pressure Ratio ◽  
Pressure Coefficient ◽  
Aircraft Engine ◽  
Tip Clearance ◽  
Flow Measurements ◽  
Stall Margin ◽  
Tip Clearance Flow ◽  
Low Speed ◽  
Axial Compressors ◽  
The Impact

This paper presents an experimental and analytical study of the impact of forward swept rotors on tip-limited, low-speed, multi-stage axial compressors. Two different configurations were examined, one with strong tip-clearance flows and the other with more moderate levels. Evaluations were done at multiple rotor tip clearance levels to assess differences in clearance sensitivity. Both configurations are low-speed models of the rear stages of modern aircraft engine high pressure ratio compressors. Compared to conventionally stacked (radial) rotors, the forward swept blades demonstrated improvements in stall margin, efficiency and clearance sensitivity. The benefits were more pronounced for the configuration with stronger tip-clearance flows. Detailed flow measurements and 3-D viscous CFD analyses are used to investigate the responsible flow mechanisms. Forward sweep causes a spanwise redistribution of flow toward the blade tip and reduces the tip loading in terms of static pressure coefficient. This results in reduced tip-clearance flow blockage, a shallower (more axial) leakage/freestream interface angle and a smaller region of reversed flow in the clearance gap.

Active Compressor Stability Management Via a Stall Margin Control Mode

2010 ◽  
Vol 132 (5) ◽  
Author(s):  
Yuan Liu ◽  
Manuj Dhingra ◽  
J. V. R. Prasad
Keyword(s):  
Pressure Fluctuations ◽  
Aircraft Engine ◽  
Rotating Stall ◽  
Control Mode ◽  
Engine Control ◽  
Correlation Measure ◽  
Stall Margin ◽  
Engine Control System ◽  
Compressor Rotor ◽  
Margin Control

An active engine control scheme for protection against compressor instabilities such as rotating stall and surge is presented. Compressor stability detection is accomplished via a parameter known as the correlation measure, which quantifies the repeatability of the pressure fluctuations in the tip region of a compressor rotor. This work investigates the integration of the correlation measure with an aircraft engine control system through the use of a stall margin control mode. The development and implementation of the stall margin mode are described. The effectiveness of the overall active control framework—an active compressor stability management system—is assessed using a computer simulation of a high-bypass, dual-spool, commercial-type turbofan engine.

Experimental Investigation of Compressor Aerodynamic Instability Induced by Rotating Disturbance

2014 ◽  
Author(s):  
Wei Yan ◽  
Huan Zhang ◽  
Zhi-ming Mao ◽  
Chao Yin ◽  
Chen-kai Zhang ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Single Cell ◽  
Flow Separation ◽  
Rotating Stall ◽  
Aerodynamic Stability ◽  
Stall Inception ◽  
Stall Margin ◽  
Rotating Speed ◽  
Aerodynamic Instability ◽  
Circumferential Extent

In twin-spool engines, there will be a rotating disturbance at the inlet of the downstream compressor when rotating stall occurs in the upstream compressor. It will lead the downstream compressor to aerodynamic instability if the speed difference between the two spools is not designed reasonably. In order to investigate how the rotating disturbance affects, a two-stage compressor is operated with a newly designed rotating disturbance generator running upstream. The generator is able to produce disturbances with different circumferential extent. It can also produce a disturbance with more than one cell. The rotating speed of the generated disturbances is designed up to 100 percent of the compressor speed. The experiments show that the compressor experiences significant degradation in its stall margin when the disturbance rotates at the “dangerous speed”. The circumferential extent of the rotating disturbance also has an influence on the stall margin. Rotating disturbances with larger circumferential extent lead to severer loss of stall margin. However, it does not affect the “dangerous speed”. The twin-cell disturbance affects the stall boundary of the compressor in a similar manner as the single-cell disturbance does. It is the rotating speed of each cell acts on the stall boundary. Based on the analysis of stall inception under different rotating disturbances, an explanation is given to interpret the mechanism of the “dangerous speed”. The “dangerous speed” is associated with the propagating speed of stall inception. When the disturbance is rotating at this speed, it will intensify the flow separation and accelerate the growth of rotating stall, thus aggravates the compressor aerodynamic stability.

The impact of circumferential casing grooves on rotating instability in a transonic axial compressor

2018 ◽  
Vol 233 (8) ◽  
pp. 2868-2893 ◽  
Author(s):  
Shubo Ye ◽  
Qingjun Zhao ◽  
Xiaoyong Zhou ◽  
Guang Xi ◽  
Jianzhong Xu
Keyword(s):  
Axial Compressor ◽  
Passage Time ◽  
Suction Surface ◽  
Tip Leakage Vortex ◽  
Stall Margin ◽  
Tip Leakage ◽  
Operation Speed ◽  
Transonic Axial Compressor ◽  
Rotating Instability ◽  
The Impact

The impact of circumferential casing grooves on rotating instability is first assessed for both design and part speed operations in a transonic axial compressor, with the purpose of developing the next generation casing treatments for vibration control. Multi-passage time-resolved computations are performed to capture the origination and propagation behavior of the instability for cases with and without casing grooves. Probed pressure signals in different passages show a nonsynchronous fluctuation of tip flow. It proves tip leakage vortex and its self-excited oscillation is responsible for this type of inconsistence, regardless of the compressor operation speed. Although flow separation on blade suction surface and the consequent shedding vortex contributes to another origin of instability, the resulted flow appears to be consistent. Casing grooves are able to enhance the synchronization by greatly suppressing both tip leakage vortex oscillations and the intermittently shedding separation vortex, especially in the front part of blade passage. Both types of instability are constrained in several separated axial scope by casing grooves, which essentially increase the damping of flow oscillations. Thus, further improvement of casing treatment design can be expected if the axial transport of the instability in the tip region is restrained more efficiently, for both extending stall margin and enhancing aerodynamic stability.

scholarly journals Design and Development of a Nine Stage Axial Flow Compressor for Industrial Gas Turbines

1998 ◽  
Author(s):  
G. D. Stringham ◽  
B. N. Cassem ◽  
T. C. Prince ◽  
P. F. Yeung
Keyword(s):  
Gas Turbines ◽  
Pressure Ratio ◽  
Axial Flow ◽  
Leading Edge ◽  
Aircraft Engine ◽  
Modern Technology ◽  
Stall Margin ◽  
Axial Flow Compressor ◽  
Flow Compressor ◽  
The Impact

A nine stage industrial axial flow compressor with a pressure ratio of 9.1:1 was designed, built and rig tested. The modern technology and design tools developed by government/aircraft engine compressor technologists were used for an industrial gas turbine application. The compressor was designed with “arbitrary” airfoil blading including CFD analysis in all blade rows. Flowpath contouring in the hub region of the rotors was used to decrease losses. The compressor rig was tested at the Compressor Research Facility at Wright Patterson Air Force Base in Dayton, Ohio. Extensive testing included determining the impact of stator leading edge instrumentation on performance. The compressor demonstrated excellent efficiency and stall margin in its first build. This paper describes the aerodynamic design, test instrumentation and test results.

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