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Journal ArticleDOI

Stall Inception in Axial Compressors

01 Jan 1990-Journal of Turbomachinery-transactions of The Asme (American Society of Mechanical Engineers)-Vol. 112, Iss: 1, pp 116-123
TL;DR: In this paper, detailed measurements have been made of the transient stalling process in an axial compressor stage, where the stage is of high hub-casing ratio and stall is initiated in the rotor.
Abstract: Detailed measurements have been made of the transient stalling process in an axial compressor stage. The stage is of high hub-casing ratio and stall is initiated in the rotor. If the rotor tip clearance is small stall inception occurs at the hub, but at clearances typical for a multistage compressor the inception is at the tip. The crucial quantity in both cases is the blockage caused by the endwall boundary layer. Prior to stall, disturbances rotate around the inlet flow in sympathy with rotating variations in the endwall blockage; these can persist for some time prior to stall, rising and falling in amplitude before the final increase, which occurs as the compressor stalls. © 1990 by ASME.
Citations
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Journal ArticleDOI
TL;DR: In this article, a study of stall inception mechanisms in a low-speed axial compressor is presented, where the authors show that the stability criteria for the two disturbances are different: long length scale disturbances are related to a two-dimensional instability of the whole compression system, while short length-scale disturbances indicate a three-dimensional breakdown of the flow-field associated with high rotor incidence angles.
Abstract: This paper presents a study of stall inception mechanisms in a low-speed axial compressor. Previous work has identified two common flow breakdown sequences, the first associated with a short length-scale disturbance known as a “spike,” and the second with a longer length-scale disturbance known as a “modal oscillation.” In this paper the physical differences between these two mechanisms are illustrated with detailed measurements. Experimental results are also presented that relate the occurrence of the two stalling mechanisms to the operating conditions of the compressor. It is shown that the stability criteria for the two disturbances are different: Long length-scale disturbances are related to a two-dimensional instability of the whole compression system, while short length-scale disturbances indicate a three-dimensional breakdown of the flow-field associated with high rotor incidence angles. Based on the experimental measurements, a simple model is proposed that explains the type of stall inception pattern observed in a particular compressor. Measurements from a single-stage low-speed compressor and from a multistage high-speed compressor are presented in support of the model.

277 citations

Journal ArticleDOI
TL;DR: In this article, a semi-historical look at some of these fields of study (stall, surge, active control, rotating instabilities etc.) and examine the ideas which underpin each topic are presented.
Abstract: Work on rotating stall and its related disturbances has been in progress since the Second World War. During this period, certain ‘hot topics’ have come to the fore — mostly in response to pressing problems associated with new engine designs. This paper will take a semi-historical look at some of these fields of study (stall, surge, active control, rotating instabilities etc.) and will examine the ideas which underpin each topic. Good progress can be reported, but the paper will not be an unrestricted celebration of our successes because, after 75 years of research, we are still unable to predict the stalling behaviour of a new compressor or to contribute much to the design a more stall resistant machine. Looking forward from where we are today, it is clear that future developments will come from CFD in the form of better performance predictions, better flow modelling and improved interpretation of experimental results. It is also clear that future experimental work will be most effective when focussed on real compressors with real problems — such as stage matching, large tip clearances, eccentricity and service life degradation. Today’s topics of interest are mostly associated with compressible effects and so further research will require more high speed testing.Copyright © 2015 by ASME

238 citations

Journal ArticleDOI
TL;DR: In this article, the role of the passage shock/leakage vortex interaction in generating endwall blockage is discussed, as a result of the shock/vortex interaction at design speed, the radial influence of the tip clearance flow extends to 20 times the physical tip clearance height.
Abstract: Experimental and computational techniques are used to investigate tip clearance flows in a transonic axial compressor rotor at design and part speed conditions. Laser anemometer data acquired in the endwall region are presented for operating conditions near peak efficiency and near stall at 100% design speed and at near peak efficiency at 60% design speed. The role of the passage shock/leakage vortex interaction in generating endwall blockage is discussed. As a result of the shock/vortex interaction at design speed, the radial influence of the tip clearance flow extends to 20 times the physical tip clearance height. At part speed, in the absence of the shock, the radial extent is only 5 times the tip clearance height. Both measurements and analysis indicate that under part-speed operating conditions a second vortex, which does not originate from the tip leakage flow, forms in the endwall region within the blade passage and exits the passage near midpitch. Mixing of the leakage vortex with primary flow downstream of the rotor at both design and part speed conditions is also discussed.

178 citations

Journal ArticleDOI
TL;DR: In this article, the authors examined measurements from both low-and high-speed compressors to explain the characteristic features of spike-type stall in axial compressors and found that tip-clearance backflow at the blade's trailing edge in combination with forward spillage of tip-leakage flow at the leading edge is a possible mechanism for spike formation.
Abstract: An aerodynamic instability known as stall occurs in axial compressors as the mass flow rate is reduced and the blade loading reaches its limit. At this limiting condition, an easily recognizable flow breakdown process, known as spike-type stall inception, is observed in most modern compressors. This article begins by examining measurements from both low- and high-speed compressors to explain the characteristic features of spike-type stall. This is followed by a review of past work on compressor stability and an assessment of recent advances in this field. Included here is a study of the three-dimensional flow features that typify spike formation and its eventual growth into a mature stall cell. We also consider the formation criteria for spike-type stall and the means for early detection and possible control. On the computational side, a possible mechanism for spike formation is identified from three-dimensional studies of the flow in the rotor tip region. This mechanism involves tip-clearance backflow at the blade's trailing edge in combination with forward spillage of tip-leakage flow at the leading edge. This flow pattern implies that a successful stall-control technology will have to rely on an effective means of suppressing tip-clearance backflow and forward spillage.

148 citations

Proceedings ArticleDOI
03 Jun 1991
TL;DR: In this paper, it was shown that modal perturbations are not always present prior to stall, and when present, sometimes have little direct effect on the formation of the stall cells.
Abstract: Studies have been conducted on two laboratory test compressors to investigate the process leading to the formation of finite amplitude rotating stall cells. The measurements were obtained from circumferential arrays of hot-wires and were spatially and temporarily analysed to show that modal perturbations are not always present prior to stall, and when present, sometimes have little direct effect on the formation of the stall cells. The measurements lead to the conclusion that the occurrence of modal perturbations, and the formation of finite amplitude stall cells, are two separate phenomena; both occurring under roughly the same conditions at the peak of the pressure rise characteristic. The measurements also underline the hitherto unsuspected importance of short length scale disturbances in the process of stall inception. Examples are given of different ways in which stall cells can develop and the conclusions are backed up with a summary of current test data from various machines around the world.Copyright © 1991 by ASME

143 citations