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

Stall, Surge, and 75 Years of Research

The breakdown of tip leakage vortex has been investigated on a low-speed axial compressor rotor with moderate blade loading. Effects of the breakdown on the rotor aerodynamics are elucidated by Navier-Stokes flow simulations and visualization techniques for identifying the breakdown. The simulations show that the leakage vortex breakdown occurs inside the rotor at a lower flow rate than the peak pressure rise operating condition. The breakdown is characterized by the existence of the stagnation point followed by a bubblelike recirculation region. The onset of breakdown causes significant changes in the nature of the tip leakage vortex: large expansion of the vortex and disappearance of the streamwise vorticity concentrated in the vortex. The expansion has an extremely large blockage effect extending upstream of the leading edge. The disappearance of the concentrated vorticity results in no rolling-up of the vortex downstream of the rotor and the disappearance of the pressure trough on the casing. The leakage flow field downstream of the rotor is dominated by the outward radial flow, resulting from the contraction of the bubblelike structure of the breakdown region. It is found that the leakage vortex breakdown plays a major role in characteristic of rotor performance at near-stall conditions. As the flow rate is decreased from the peak pressure rise operating condition, the breakdown region grows rapidly in the streamwise, spanwise, and pitchwise directions. The growth of the breakdown causes the blockage and the loss to increase drastically. Then, the interaction of the breakdown region with the blade suction surface gives rise to the three-dimensional separation of the suction surface boundary layer, thus leading to a sudden drop in the total pressure rise across the rotor.

The Role of Tip Leakage Vortex Breakdown in Compressor Rotor Aerodynamics

Newly revised, this new fifth edition includes a chapter on waste heat recovery and discusses this technology in detail including a the advantages and barriers to waste heat recovery, environmental restraints, thermodynamics of heat recovery, fluid properties, boiler, condensers, steam turbines, off design behavior and exhaust catalyst. This book shows how microturbine designs rely heavily on the centrifugal compressor and are, in many aspects, similar to the early flight engines and will illustrate how the approach of the microturbine designer is to minimize cost.

Gas Turbine Handbook: Principles and Practices

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.

Spike-Type Compressor Stall Inception, Detection, and Control

▪ Abstract The compression system instabilities known as surge and rotating stall are natural limits to the performance of all compressors and are especially troubling in gas turbine engines. In the last 15 years, rapid progress has been made in understanding this complex problem through the application of control technology; in particular, system identification techniques have proven to be useful. New findings include the roles of compressibility and nonlinearity in the stall-inception process. These findings have been used to implement feedback control schemes that have achieved increased stability in a variety of compressors and engines. Approaches fall into one of two categories: (a) operating range extension through active damping of linear disturbances, or (b) manipulation of the nonlinear system dynamics to maintain the operating point close to the instability boundary in the presence of disturbances seen in operation.

Compression system stability and active control

Statistical characteristics of pressure fluctuation on the casing wall of two axial flow compressor rotors have been investigated experimentally to find a precursor of rotating stall. Near stall, the casing wall pressure across a flow passage near the leading edge is characterized by a highly unsteady region where low-momentum fluid accumulates. The periodicity of the pressure fluctuation with blade spacing disappears and an alternative phenomenon comes into existence, which supports the disturbance propagating at a different speed from the rotor revolution. The precursor of rotating stall can be detected by monitoring collapse of the periodicity in the pressure fluctuation. To represent the periodicity qualitatively, a practical detection parameter has been proposed, which is easily obtained from signals of a single pressure sensor installed at an appropriate position on the casing wall during operation of a compressor.

Detection of a Rotating Stall Precursor in Isolated Axial Flow Compressor Rotors

Detection of a rotating stall precursor of isolated axial flow compressor rotors

Closure to “Discussion of ‘Detection of a Rotating Stall Precursor in Isolated Axial Flow Compressor Rotors’” (1991, ASME J. Turbomach., 113, pp. 288–289)

Takahito Iwamoto

Papers

Detection of a Rotating Stall Precursor in Isolated Axial Flow Compressor Rotors

Detection of a rotating stall precursor of isolated axial flow compressor rotors

Closure to “Discussion of ‘Detection of a Rotating Stall Precursor in Isolated Axial Flow Compressor Rotors’” (1991, ASME J. Turbomach., 113, pp. 288–289)