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.

Experimental study of self-recirculating casing treatment in a subsonic axial flow compressor

2016 ◽  
Vol 230 (8) ◽  
pp. 805-818 ◽  
Author(s):  
Wei Wang ◽  
Wuli Chu ◽  
Haoguang Zhang ◽  
Yanhui Wu
Keyword(s):  
Axial Flow ◽  
Operating Conditions ◽  
Geometrical Parameters ◽  
Flow Angle ◽  
Casing Treatment ◽  
Axial Flow Compressor ◽  
Blade Tip ◽  
Overall Performance ◽  
Flow Compressor ◽  
Casing Treatments

Parametric studies of recirculating casing treatment were experimentally performed in a subsonic axial flow compressor. The recirculating casing treatment was parameterized with injector throat height, injection position, and circumferential coverage percentage. Eighteen recirculating casing treatments were tested to study the effects on compressor stability and on the compressor overall performance at three blade speeds. The profiles of recirculating casing treatment were optimized to minimize the losses generated by air recirculation. In the experiment, the stalling mass flow rate, total pressure ratio, and adiabatic efficiency of the compressor were measured to study the steady-state effects on the compressor performance of recirculating casing treatments, and static pressure disturbances on the casing wall were monitored to study the influence on stall dynamics. Results indicate that both the compressor stability and overall performance can be improved through recirculating casing treatment with appropriate geometrical parameters for all the test speeds. The influence on stall margin of one geometric parameter often depends on the choice of others, i.e. the interaction effects exist. In general, the recirculating casing treatment with a moderate injector throat and a large circumferential coverage is the optimal choice to enhance compressor stability. The injector of recirculating casing treatment should be placed upstream of the blade tip leading edge and the injector throat height should be lower than four times the rotor tip gap for the benefits of compressor efficiency. At 71% speed, the blade tip loading is decreased through recirculating casing treatment at the operating condition of near peak efficiency and increased near stall. Moreover, the outlet absolute flow angle is reduced in the tip region and enhanced at lower blade spans for both operating conditions. The stall inceptions are not changed with the implementation of recirculating casing treatment for all the test speeds, but the stall patterns are altered at 33% and 53% speeds, i.e. the stall with two cells is detected in the recirculating casing treatment compared with the solid casing with only one stall cell.

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.

scholarly journals Flow mechanism of affecting an axial flow compressor performance and stability with cross-blade slot casing treatments

2018 ◽  
Vol 233 (1) ◽  
pp. 17-36 ◽  
Author(s):  
HaoGuang Zhang ◽  
XuDong Zhang ◽  
YanHui Wu ◽  
WuLi Chu ◽  
HaiYang Kuang
Keyword(s):  
Axial Flow ◽  
Low Energy ◽  
Peak Efficiency ◽  
Stall Margin ◽  
Casing Treatment ◽  
Flow Loss ◽  
Stall Margin Improvement ◽  
And Performance ◽  
Flow Compressor ◽  
Casing Treatments

The objective of this study is to evaluate the effect of cross-blade slot casing treatment on the stability and performance of an axial flow compressor rotor. The experimental and unsteady calculated results both show that cross-blade slot casing treatment can generate about 22% stall margin improvement, and the compressor peak efficiency is reduced by about 13%. The detailed flow-field analyses indicate that the sucked and injected flow caused by the slots of cross-blade slot casing treatment can restrain the rotor tip passage blockage, which is made by the low energy tip clearance leakage vortex. When cross-blade slot casing treatment is applied, not only the rotor wheel flange work becomes lower in most of the rotor blade span, but also the flow loss in the blade tip passage becomes fairly large due to the strong interaction between the mainstream and the injected flows made by the slots. As a result, the compressor total pressure ratio and efficiency for cross-blade slot casing treatment are reduced obviously. Three kinds of new cross-blade slot casing treatment were designed according to the previous successful experience and investigated in this paper. The numerical results show that the new three cross-blade slot casing treatments both generate about 54% stall margin improvement at the cost of minor peak efficiency. For one new cross-blade slot casing treatment (CSCT2), the compressor peak efficiency is reduced by about 0.3%. The low energy TLV, which is present for cross-blade slot casing treatment, is removed by the strong sucked flow made by CSCT2. Moreover, the interaction between the mainstream and the injected flows caused by CSCT2 becomes weak obviously, and the corresponding flow loss is reduced greatly. Hence, the compressor stability and performance with CSCT2 are higher than those with cross-blade slot casing treatment.

Experimental Investigation on the Effect of Porosity of Bend Skewed Casing Treatment on a Single Stage Transonic Axial Flow Compressor

2014 ◽  
Author(s):  
Dilipkumar B. Alone ◽  
Subramani Satish Kumar ◽  
Shobhavathy Thimmaiah ◽  
Janaki Rami Reddy Mudipalli ◽  
A. M. Pradeep ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Axial Flow ◽  
Compressor Stage ◽  
Casing Treatment ◽  
Operating Range ◽  
Axial Flow Compressor ◽  
Transonic Compressor ◽  
Stable Operating ◽  
Flow Compressor ◽  
Casing Treatments

A bend skewed casing treatment was designed, to study the influence of one of its geometrical parameter porosity on the stable performance of single stage transonic axial flow compressor. The compressor was designed for the stage total-to-total pressure ratio of 1.35, corrected mass flow rate of 22 kg/s at corrected design speed of 12930 RPM. Bend skewed casing treatment has an axial inlet segment till 50% of the total length and rear segment that is skewed by 45° in the direction of the rotor tip section stagger. Both the sections were oriented at a skew angle of 45° to the radial plane such that the flow exiting the slot is in counter-clockwise direction to that of the rotor direction. The casing treatment slot width was equal to the maximum thickness of the rotor blades. Three casing treatment configurations were identified for the current experimental investigation. All the treatment geometries considered for the experimental research have lower porosities than reported in the open literatures. The effect of the porosity parameter on the performance of transonic compressor stage was evaluated at two axial coverages of 20% and 40% relative to the rotor tip axial chord. Performance maps were obtained for the solid casing and casing treatment with three different porosities. Comparative studies were carried out and experimental results showed a maximum of 65% improvement in the stable operating range of the compressor for one of the treatment configurations. It was also observed that the stable operating range of the compressor increases with an increase in the casing treatment porosity. All the casing treatment configurations showed that the compressor stall occurs at lower mass flows as compared to the solid casing. Compressor stage peak efficiency shows significant degradations with increase in the porosity as compared to solid casing. Detailed blade element performances were also obtained using calibrated multi-hole aerodynamic probe. Comparative variations of flow parameters like absolute flow angle, Mach number were studied at full flow and near stall conditions for the solid casing and casing treatment configurations. Hot wire measurements show very high fluctuation in the inlet axial velocity in the presence of solid casing as compared to casing treatments. Experimental investigation revealed that the porosity of the casing treatments has strong influence on the transonic compressor stage performance.

Study on the Influence of Self-Circulating and Slot Combined Casing Treatment on the Stability of Transonic Compressor

2020 ◽  
Author(s):  
Song Yan ◽  
WuLi Chu ◽  
Zhengjing Shen
Keyword(s):  
Axial Flow ◽  
Internal Flow ◽  
Simulation Method ◽  
Tip Clearance ◽  
Single Type ◽  
Casing Treatment ◽  
Transonic Compressor ◽  
Blade Tip ◽  
The Stability ◽  
Stability Effect

Abstract Casing treatment (CT) has proven to be an effective way to enhance stability, and has a very important role in enhancing the stability of the compressor. Researchers have made great achievements and progress in the study of single-type CT structure, but less research on combined-type CT structure. In this paper, the isolated rotor of a high-load axial-flow compressor is taken as the research object, and the numerical simulation method is used to study the enhancing stability mechanism of the combined-type casing treatment (ASCT) by combining the axial slot casing treatment (ASC) and the self-circulating casing treatment (SCT). The study found that the reasonable choice of the ASCT scheme can make the enhancing stability effect of the ASCT higher than that of the single-type CT structure scheme. Through detailed quantitative analysis of the rotor’s internal flow field, it was found that ASC and SCT can suction the airflow downstream of the rotor passage, and then spray it into the main flow from the upstream of the rotor passage, and the blade tip blockage is reduced, the flow capacity of the blade tip passage is improved, and the rotor stability is enhanced by suppressing tip clearance leakage flow. The ASCT has both the spraying effect of the ASC and the SCT, and has the best improvement effect on the flow blockage zone in the rotor passage, and the obtained enhancing stability effect is also best. In addition, the circulation and re-injection of the airflow after CT has aggravated the flow blending loss in the blade tip zone, which has reduced the rotor efficiency. The ASCT has both the characteristics of the effect of the ASC and the SCT on the rotor efficiency, resulting in a large reduction in the rotor efficiency after using the ASCT.

Numerical Investigation of Stall Mechanism of an Axial Compressor at Three Different Rotating Speeds

2017 ◽  
Author(s):  
HaoGuang Zhang ◽  
Feng Tan ◽  
Kang An ◽  
YanHui Wu ◽  
WuLi Chu
Keyword(s):  
Axial Flow ◽  
Leading Edge ◽  
Complex Flows ◽  
Tip Leakage Vortex ◽  
Rotating Speed ◽  
Tip Leakage ◽  
Blade Tip ◽  
Layer Flow ◽  
Flow Compressor ◽  
Axial Flow Compressors

For some axial flow compressors, the compressor stall is a result of the blade tip blockage caused by the complex flows, which include the boundary layer flow separation (BLFS), tip leakage flow (TLF), and shock wave. Owing to the difference of the design rotating speed and aerodynamic load in the axial flow compressor, these complex flows might exist in isolation or occur at the same time in practical application. Aiming at the stall mechanism in the axial flow compressors, a great deal of experimental and numerical investigations have been carried out at the design rotating speed. However, the investigation for off-design rotating speed in the axial flow compressors is seldom. Therefore, a transonic axial flow compressor rotor, which is NASA Rotor67, was chosen to investigate the stall mechanism at 100%, 80% and 60% design rotating speeds with the help of the numerical method. Moreover, the guiding suggestions for selecting the measures of increasing the transonic axial flow compressors stability are presented for the later investigation. The compared results show that the variation tendency of the experimental total performance lines are finely repeated by the numerical results at the three design rotating speeds. The fundamental flow mechanism of the rotor is obtained by analyzing the flow field in the blade passage in details. With the decrease of the rotor mass flow at the three design rotating speeds, the starting position of the tip leakage vortex (TLV) moves to the blade leading edge gradually, and the tip leakage vortex also deviates to the pressure surface of the adjacent blade. The deviated angle, which is the angle between the trajectory of the tip leakage vortex core and rotor rotating axis, for near stall point (NS) are about three degree, five degree and nine degree than that for near peak efficiency point (NPE) at 100%, 80% and 60% design rotating speeds respectively. The blockage resulted from the interaction between the tip leakage vortex and shock wave is the cause of the rotor stall at 100% and 80% design rotating speeds. Besides, the breakdown of the tip leakage vortex and leading edge spilled flow (LESF) occur at 80% design rotating speed. At 60% design rotating speed, the blockage caused by the leading edge spilled flow resulted from the tip leakage vortex is the main cause of bringing about the compressor stall, and the boundary layer flow separation (BLFS) in a small scope appears at the blade tip suction surface near the trailing edge.

Effects of a Vane-Recessed Tubular-Passage Passive Stall Control Technique on a Multistage, Axial-Flow Compressor: Results of Tests on the First Stage With the Rear Stages Removed

2003 ◽  
Author(s):  
M. Akhlaghi ◽  
R. L. Elder ◽  
K. W. Ramsden
Keyword(s):  
Rotor Blade ◽  
Axial Flow ◽  
Control Technique ◽  
Maximum Efficiency ◽  
Stall Margin ◽  
Casing Treatment ◽  
Axial Flow Compressor ◽  
Stall Margin Improvement ◽  
Blade Tip ◽  
Flow Compressor

The objective of the current study was to investigate the effect of casing treatment on a multistage axial flow compressor. The main purpose of the investigation was to extend the range and operability of multistage axial compressors. The study seeks to establish whether a vane-recessed tubular-passage casing-treatment could provide beneficial stall margin improvement, without sacrificing the efficiencies of the compressor with the restricted space available for the treatment. A casing treatment that consisted of three parts: an outer casing ring, with a tubular shaped passage on the inside, a set of 120 evenly spaced curved vanes, and then a shroud or inner ring was developed from two initial designs. The casing treatment, manufactured from high quality acrylic, was positioned upstream and partly covering the tip of the first stage rotor blades. The casing treatment was tested on the first stage of a three-stage low-speed compressor with inlet guide vanes with the rear two stages removed. The rotor blade tip axial chord exposure had a significant impact on the effectiveness of the casing treatment. Seven compressor configuration incorporating casing treatments of 23.2%, 33.3%, 43.4%, 53.5%, 63.6%, 73.7% and 83.8% rotor exposure were tested. The results showed significant improvements in stall margin in all exposures and insignificant efficiency sacrifices in some exposures. Nearly 29% of 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 53.5% rotor exposure was the best configuration in terms of maximum efficiency gain. In terms of peak pressure rise coefficients the compressor configuration with a casing treatment of 63.6% exposure was the best design. The results also suggest that the vane-recessed tubular-passage casing treatment designed as part of this research, in most instances enabled the stall conditions in the compressor to become progressive rather than abrupt.

Influencing Parameters of Tip Blowing Interacting With Rotor Tip Flow

2016 ◽  
Vol 139 (2) ◽  
Author(s):  
Cyril Guinet ◽  
André Inzenhofer ◽  
Volker Gümmer
Keyword(s):  
Geometric Model ◽  
Axial Compressor ◽  
Axial Flow ◽  
Navier Stokes ◽  
Axial Position ◽  
Design Parameters ◽  
Stall Margin ◽  
Casing Treatment ◽  
Transonic Compressor ◽  
Casing Treatments

The design space of axial-flow compressors is restricted by stability issues. Different axial-type casing treatments (CTs) have shown their ability to enhance compressor stability and to influence efficiency. Casing treatments have proven to be effective, but there still is need for more detailed investigations and gain of understanding for the underlying flow mechanism. Casing treatments are known to have a multitude of effects on the near-casing 3D flow field. For transonic compressor rotors, these are more complex, as super- and subsonic flow regions alternate while interacting with the casing treatment. To derive design rules, it is important to quantify the influence of the casing treatment on the different tip flow phenomena. Designing a casing treatment in a way that it antagonizes only the deteriorating secondary flow effects can be seen as a method to enhance stability while increasing efficiency. The numerical studies are carried out on a tip-critical rotor of a 1.5-stage transonic axial compressor. The examined recirculating tip blowing casing treatment (TBCT) consists of a recirculating channel with an air off-take above the rotor and an injection nozzle in front of the rotor. The design and functioning of the casing treatment are influenced by various parameters. A variation of the geometry of the tip blowing, more specifically the nozzle aspect ratio, the axial position, or the tangential orientation of the injection port, was carried out to identify key levers. The tip blowing casing treatment is defined as a parameterized geometric model and is automatically meshed. A sensitivity analysis of the respective design parameters of the tip blowing is carried out on a single rotor row. Their impact on overall efficiency and their ability to improve stall margin are evaluated. The study is carried out using unsteady Reynolds-averaged Navier–Stokes (URANS) simulations.

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.

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