The Stability-Limiting Flow Mechanisms in a Subsonic Axial-Flow Compressor and Its Passive Control With Casing Treatment

2008 ◽  
Author(s):  
Xingen Lu ◽  
Junqiang Zhu ◽  
Chaoqun Nie ◽  
Weiguang Huang
Keyword(s):  
Flow Instability ◽  
State Of The Art ◽  
Axial Flow ◽  
Flow Mechanism ◽  
Blade Passage ◽  
Casing Treatment ◽  
Compressor Rotor ◽  
Flow Compressor ◽  
The Stability ◽  
End Wall

The phenomenon of flow instability in the compression system such as fan and compressor has been a long-standing “bottle-neck” problem for gas turbines/aircraft engines. With a vision of providing a state-of-the-art understanding of the flow field in axial-flow compressor in the perspective of enhancing their stability using passive means. Two topics are covered in this paper. The first topic is the stability-limiting flow mechanism close to stall, which is the basic knowledge needed to manipulate end-wall flow behavior for the stability improvement. The physical process occurring when approaching stall and the role of complex tip flow mechanism on flow instability in current high subsonic axial compressor rotor has been assessed using single blade passage computations. The second topic is flow instability manipulation with casing treatment. In order to advance the understanding of the fundamental mechanisms of casing treatment and determine the change in the flow field by which casing treatment improve compressor stability, systematic studies of the coupled flow through a subsonic compressor rotor and various end-wall treatments were carried out using a state-of-the-art multi-block flow solver. The numerically obtained flow fields were interrogated to identify complicated flow phenomenon around and within the end-wall treatments and describe the interaction between the rotor tip flow and end-wall treatments. Detailed analyses of the flow visualization at the rotor tip have exposed the different tip flow topologies between the cases with treatment casing and with untreated smooth wall. It was found that the primary stall margin enhancement afforded by end-wall treatments is a result of the tip flow manipulation. Compared to the smooth wall case, the treated casing significantly dampen or absorb the blockage near the upstream part of the blade passage caused by the upstream movement of tip clearance flow and weakens the roll-up of the core vortex. These mechanisms prevent an early spillage of low momentum fluid into the adjacent blade passage and delay the onset of flow instability.

Experimental and numerical investigation of a subsonic compressor with bend-skewed slot-casing treatment

2006 ◽  
Vol 220 (12) ◽  
pp. 1785-1796 ◽  
Author(s):  
X Lu ◽  
W Chu ◽  
Y Zhang ◽  
J Zhu
Keyword(s):  
Rotor Blade ◽  
Axial Flow ◽  
Efficiency Gain ◽  
Stall Margin ◽  
Blade Passage ◽  
Casing Treatment ◽  
Axial Flow Compressor ◽  
Compressor Rotor ◽  
Flow Compressor ◽  
Isentropic Efficiency

On the basis of the test results of discrete axial and blade angle slot casing treatment, a new type of casing treatment was designed for a subsonic axial flow compressor rotor by optimizing various geometry parameters. To obtain a wide operating range and to minimize penalties in terms of isentropic efficiency, seven compressor configurations incorporating casing treatments of 0, 16.6, 33.3, 50, 66.6, 83.3, and 100 per cent rotor exposures were experimentally investigated. The results showed that significant improvements in stall margin are possible in all exposures and insignificant isentropic efficiency sacrifices are recorded in some exposures. Nearly 21.43 per cent stall margin improvement in terms of the corrected mass flow-rate was achieved with 33.3 per cent rotor blade tip axial chord exposure. The compressor built with 16.6 per cent rotor exposure was the best configuration in terms of maximum isentropic efficiency gain. The second issue of the paper was to offer a contribution to the understanding of the physical mechanism by which bend-skewed slot-casing treatment improves stall margin under subsonic conditions. By applying a concept similar to ‘Domain scaling’ approach (as often used in multistage turbomachinery flow-fields) to the interface between the rotor blade passage and end-wall treatments, a time-dependent three-dimensional numerical simulation was performed for the subsonic axial-flow compressor rotor with bend-skewed slot-casing treatment. The numerical results agreed well with the available experimental results. Detailed analyses of the coupled flow through bend-skewed slot-casing treatment and rotor blade passage under subsonic conditions led to some preliminary conclusions as to the flow physics involved in the stall margin improvements afforded by the use of bend-skewed slot-casing treatment.

Experimental and Numerical Investigation of a Subsonic Compressor With Bend Skewed Slot Casing Treatment

2006 ◽  
Author(s):  
Xingen Lu ◽  
Wuli Chu ◽  
Junqiang Zhu ◽  
Yanhui Wu
Keyword(s):  
Rotor Blade ◽  
Axial Flow ◽  
Efficiency Gain ◽  
Stall Margin ◽  
Blade Passage ◽  
Casing Treatment ◽  
Axial Flow Compressor ◽  
Compressor Rotor ◽  
Flow Compressor ◽  
Isentropic Efficiency

Based on the test results of discrete axial and blade angle slot casing treatment, a new type of casing treatment was designed for a subsonic axial flow compressor rotor by optimising various geometry parameters. To obtain a wide operating range and to minimize penalties in terms of isentropic efficiency, seven compressor configurations incorporating casing treatments of 0%, 16.6%, 33.3%, 50%, 66.6%, 83.3% and 100% rotor exposure were experimentally investigated. The results showed that significant improvements in stall margin are possible in all exposures and insignificant isentropic efficiency sacrifices are recorded in some exposures. Nearly 21.43% stall margin improvement in terms of the corrected mass flow rate was achieved with 33.3% rotor blade tip axial chord exposure. The compressor build with 16.6% rotor exposure was the best configuration in terms of maximum isentropic efficiency gain. The second issue of the paper was to offer a contribution to the understanding of the physical mechanism by which bend skewed slot casing treatment improve stall margin under subsonic conditions. By applying a concept similar to “Domain Scaling” approach (as often used in multistage turbomachinery Flow-fields) to the interface between the rotor blade passage and end-wall treatments, a time-dependent 3-dimentional numerical simulation was performed for the subsonic axial-flow compressor rotor with bend skewed slot casing treatment. The numerical results agreed well with experimental results. Detailed analyses of the coupled flow through bend skewed slot casing treatment and rotor blade passage under subsonic conditions led to some preliminary conclusions as to the flow physics involved in the stall margin improvements afforded by the use of bend skewed slot casing treatment.

Aerodynamics of Compressor Casing Treatment: Part I—Experiment and Time-Accurate Numerical Simulation

2008 ◽  
Author(s):  
Fan Lin ◽  
Fangfei Ning ◽  
Huoxing Liu
Keyword(s):  
Axial Flow ◽  
Peak Efficiency ◽  
Flow Rates ◽  
Casing Treatment ◽  
Compressor Rotor ◽  
Rotor Design ◽  
Mass Flow Rates ◽  
Unsteady Rans ◽  
Flow Compressor ◽  
Operating Points

This paper presents both experimental and unsteady RANS investigations of a slot-type casing treatment at a transonic axial flow compressor rotor. Experimental results show that at 60% and 98% of rotor design wheel speeds, approximately 100% and 200% extra extensions of the rotor operation ranges are achieved, respectively. On the other hand, there are about 3.6% and 2.0% drops of efficiencies at 60% and 98% speeds respectively if comparisons are made at the same peak-efficiency mass flow rates of the solid casing case. If comparing the respective peak efficiencies for the solid casing case with those for the treated casing case, there are still about 3.4% and 0.7% drops at 60% and 98% speeds, respectively. As for the unsteady RANS study, an in-house unsteady RANS code has been used to study the casing treatment flow at several operating points, i.e., the peak efficiency and the near stall with regard to the solid casing case at 60% speed and 98% speed, respectively. It is shown that the interactions between the blade passage flow and the casing treatment flow exhibit different manner at two rotating speeds. The flow condition in which the rotor operates, i.e., either the subsonic condition at the 60% speed or the transonic condition with passage shock presented at the 98% speed, is one of the determinate factors that are responsible for the manner the casing treatment works. The loss production due to casing treatment is also particularly discussed.

Numerical Investigations of the Coupled Flow Through a Subsonic Compressor Rotor and Axial Skewed Slot

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Xingen Lu ◽  
Wuli Chu ◽  
Junqiang Zhu ◽  
Yangfeng Zhang
Keyword(s):  
Axial Flow ◽  
Tip Clearance ◽  
Stall Margin ◽  
Tip Clearance Flow ◽  
Casing Treatment ◽  
Axial Flow Compressor ◽  
Compressor Rotor ◽  
Clearance Flow ◽  
Flow Through ◽  
Flow Compressor

In order to advance the understanding of the fundamental mechanisms of axial skewed slot casing treatment and their effects on the subsonic axial-flow compressor flow field, the coupled unsteady flow through a subsonic compressor rotor and the axial skewed slot was simulated with a state-of-the-art multiblock flow solver. The computational results were first compared with available measured data, that showed the numerical procedure calculates the overall effect of the axial skewed slot correctly. Then, the numerically obtained flow fields were interrogated to identify the physical mechanism responsible for improvement in stall margin of a modern subsonic axial-flow compressor rotor due to the discrete skewed slots. It was found that the axial skewed slot casing treatment can increase the stall margin of subsonic compressor by repositioning of the tip clearance flow trajectory further toward the trailing of the blade passage and retarding the movement of the incoming∕tip clearance flow interface toward the rotor leading edge plane.

CFD Analysis to Investigate the Effect of Vortex Generators on a Transonic Axial Flow Compressor Stage

2015 ◽  
Author(s):  
Avinash Kumar Rajendran ◽  
M. T. Shobhavathy ◽  
R. Ajith Kumar
Keyword(s):  
Pressure Ratio ◽  
Cross Flow ◽  
Axial Flow ◽  
Vortex Generator ◽  
Leading Edge ◽  
Vortex Generators ◽  
Stall Margin ◽  
Compressor Rotor ◽  
Flow Compressor ◽  
End Wall

The performance of the compressor blade is considerably influenced by secondary flow effects, like the cross flow on the end wall as well as corner flow separation between the wall and the blade. Computational Fluid Dynamics (CFD) has been extensively used to analyze the flow through rotating machineries, in general and through axial compressors, in particular. The present work is focused on the studying the effects of Vortex Generator (VG) on test compressor at CSIR National Aerospace Laboratories, Bangalore, India using CFD. The compressor consists of NACA transonic rotor with 21 blades and subsonic stator with 18 vanes. The design pressure ratio is 1.35 at 12930 RPM with a mass flow rate of 22 kg/s. Three configurations of counter rotating VGs were selected for the analysis with 0.25δ, 0.5δ and δ height, where δ was equal to the physical thickness of boundary layer (8mm) at inlet to the compressor rotor [11]. The vortex generators were placed inside the casing at 18 percent of the chord ahead to the leading edge of the rotor. A total of 63 pairs of VGs were incorporated, with three pairs in one blade passage. Among the three configurations, the first configuration has greater impact on the end wall cross flow and flow deflection which resulted in enhanced numerical stall margin of 3.5% from baseline at design speed. The reasons for this numerical stall margin improvement are discussed in detail.

Study of Casing Treatment Effects in Axial Flow Compressors

1975 ◽  
Vol 97 (4) ◽  
pp. 477-483 ◽  
Author(s):  
M. P. Boyce ◽  
R. N. Schiller ◽  
A. R. Desai
Keyword(s):  
Axial Flow ◽  
Stability Margin ◽  
Stable Operation ◽  
Stability Margins ◽  
Casing Treatment ◽  
Blade Tip ◽  
Flow Compressor ◽  
The Stability ◽  
Casing Treatments ◽  
Axial Flow Compressors

The phenomenon of surge in an axial flow compressor has long eluded the analytical fluid dynamist. In the recent years, a growing degree of improvement and sophistication in the design of axial flow compressors to achieve higher pressure ratios has resulted in increasingly narrow domains of stable operation. A search for improving stability margins revealed the importance of the blade tip region and casing treatments. The authors have approached the problem by both experimental and analytical methods. The results are mutually confirming. Important new inroads have been made in understanding the flow in the blade tip region, operation of casing treatments and the mechanism of the onset of surge. Some significant conclusions in the selection and design of casing treatments and their effects on the stability margin are presented and explained on the basis of experimental and theoretical results.

End-Wall and Profile Losses in a Low-Speed Axial Flow Compressor Rotor

1986 ◽  
Vol 108 (1) ◽  
pp. 22-31 ◽  
Author(s):  
B. Lakshminarayana ◽  
N. Sitaram ◽  
J. Zhang
Keyword(s):  
Axial Flow ◽  
Pressure Rise ◽  
Tip Clearance ◽  
Blade Loading ◽  
Pressure Losses ◽  
Axial Flow Compressor ◽  
Compressor Rotor ◽  
Profile Losses ◽  
Flow Compressor ◽  
End Wall

The blade-to-blade variation of relative stagnation pressure losses in the tip region inside the rotor of a single-stage, axial-flow compressor is presented and interpreted in this paper. The losses are measured at two flow coefficients (one at the design point and the other at the near peak pressure rise point) to discern the effect of blade loading on the end-wall losses. The tip clearance losses are found to increase with an increase in the pressure rise coefficient. The losses away from the tip region and near the hub regions are measured downstream. The losses are integrated and interpreted in this paper.

Investigation into the flow mechanism of rotating instability in a subsonic axial flow compressor rotor

2018 ◽  
Vol 50 (6) ◽  
pp. 065509 ◽  
Author(s):  
Zhiyang Chen ◽  
Yanhui Wu ◽  
Guangyao An ◽  
Bo Wang ◽  
Yang Guowei
Keyword(s):  
Axial Flow ◽  
Flow Mechanism ◽  
Axial Flow Compressor ◽  
Compressor Rotor ◽  
Flow Compressor ◽  
Rotating Instability

An Experimental Investigation on the Mechanism of Stall Margin Improvement of Casing Treatment

1985 ◽  
Author(s):  
Zhuang Ping ◽  
Lu Ya-Jun ◽  
Li Bao-Ju ◽  
Feng Yu-Chen
Keyword(s):  
Good Reason ◽  
Three Dimensional ◽  
Axial Flow ◽  
Rotating Stall ◽  
Flow Mechanism ◽  
Three Dimensional Flow ◽  
Stall Margin ◽  
Casing Treatment ◽  
Stall Margin Improvement ◽  
Flow Compressor

A single-rotor axial flow compressor and a two-dimensional cascade have been tested with and without casing treatment. A three-dimensional flow mechanism of the onset of rotating stall is suggested. It gives good reason to explain the mechanism of stall-margin improvement of casing treatment.

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