An Overview of Rotating Stall and Surge Control for Axial Flow Compressors
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paper_title: Active Control of Rotating Stall in a Low Speed Axial Compressor

paper_content:

The onset of rotating stall has been delayed in a low speed, single-stage, axial research compressor using active feedback control. Control was implemented using a circumferential array of hot wires to sense rotating waves of axial velocity upstream of the compressor. Circumferentially travelling waves were then generated with appropriate phase and amplitude by “wiggling” inlet guide vanes driven by individual actuators. The control scheme considered the wave pattern in terms of the individual spatial Fourier components. A simple proportional control law was implemented for each harmonic. Control of the first spatial harmonic yielded an 11% decrease in the stalling mass flow, while control of the first and second harmonics together reduced the stalling mass flow by 20%. The control system was also used to measure die sine wave response of the compressor, which behaved as would be expected for a second order system.Copyright © 1991 by ASME
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paper_title: Modeling for Control of Rotating Stall in High Speed Multi-Stage Axial Compressors

paper_content:

Using a two dimensional compressible flow representation of axial compressor dynamics, a control-theoretic input-output model is derived which is of general utility in rotating stall/surge active control studies. The derivation presented here begins with a review of the fluid dynamic model, which is a 2D stage stacking technique that accounts for blade row pressure rise, loss and deviation as well as blade row and inter-blade row compressible flow. This model is extended to include the effects of the upstream and downstream geometry and boundary conditions, and then manipulated into a transfer function form that dynamically relates actuator motion to sensor measurements. Key relationships in this input-output form are then approximated using rational polynomials. Further manipulation yields an approximate model which is in standard form for studying active control of rotating stall and surge. As an example of high current relevance, the transfer function from an array of jet actuators to an array of static pressure sensors is derived. Numerical examples are also presented, including a demonstration of the importance of proper choice of sensor and actuator locations, as well as a comparison between sensor types. Under a variety of conditions, it was found that sensor locations near the front of the compressor or in the downstream gap are consistently the best choices, based on a quadratic optimization criterion and a specific 3-stage compressor model. The modeling and evaluation procedures presented here are a first step toward a rigorous approach to the design of active control systems for high speed axial compressors.Copyright © 1994 by ASME
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paper_title: Active suppression of aerodynamic instabilities in turbomachines

paper_content:

In this paper, we advocate a strategy for controlling a class of turbomachine instabilities, whose primitive phases can be modeled by linear theory, but that eventually grow into a performance-limiting modification of the basic flow. The phenomena of rotating stall and surge are two very different practical examples in which small disturbances grow to magnitudes such that they limit machine performance. We develop a theory that shows how an additional disturbance, driven from real-time data measured within the turbomachine, can be generated so as to realize a device with characteristics fundamentally different than those of the machine without control. For the particular compressor analyzed, the control increases the stable operating range by 20% of the mean flow. We show that active control can also be used to destabilize a compressor in an undesirable state such as nonrecoverable stall. Examination of the energetics of the controlled system shows the required control power scales with the square of the ambient disturbance level, which can be several orders of magnitude below the power of the machine. Brief mention is also made of the use of structural dynamics, rather than active control, to enhance stability.
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paper_title: Bifurcation Analysis of Surge and Rotating Stall in Axial Flow Compressors

paper_content:

The surge and rotating stall post-instability behaviors of axial flow compressors are investigated from a bifurcation-theoretic perspective, using a model and system data presented by Greitzer (1976a). For this model, a sequence of local and global bifurcations of the nonlinear system dynamics is uncovered. This includes a global bifurcation of a pair of large-amplitude periodic solutions. Resulting from this bifurcation are a stable oscillation (surge) and an unstable oscillation (antisurge). The latter oscillation is found to have a deciding significance regarding the particular post-instability behavior experienced by the compressor. These results are used to reconstruct Greitzer's (1976b) findings regarding the manner in which post-instability behavior depends on system parameters. Although the model does not directly reflect non axisymmetric dynamics, use of a steady-state compressor characteristic approximating the measured characteristic of Greitzer (1976a) is found to result in conclusions that compare well with observation. Thus, the paper gives a convenient and simple explanation of the boundary between surge and rotating stall behaviors, without the use of more intricate models and analyses including non axisymmetric flow dynamics.
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paper_title: Bifurcation analysis and control for surge model via the projection method

paper_content:

A bifurcation approach is adopted to analyze and control the surge model for axial flow compressors. An explicit expression is obtained for the first nonzero coefficient of the characteristic exponents of the periodic solutions born from the Hopf bifurcation associated with surge. The sign of this coefficient determines stability of the surge model at the criticality. Local nonlinear feedback control laws are then developed to stabilize the Hopf bifurcation associated with surge. Both quadratic and cubic state feedback control laws are investigated. Feedback stabilization using output measurement such as pressure rise is also studied where stabilizing gains are characterized that can be used for synthesis of surge control laws.
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paper_title: Stall analysis of high-frequency data for three swept-blade compressor rotors

paper_content:

High frequency spectra of three single-stage, high-speed compressor rotors were analyzed for behavior indicative of rotating stall. The compressor rotors were straight, backward swept, and forward swept. Power integrated over time showed promise as a prestall warning pararmeter. For the straight and swept back rotors, stall warning times varied from several seconds to 0.5 seconds. The forward swept rotor however, was difficult to characterize since surge played an important role in the stalling characteristic and stall appeared to originate at the hub of the rotor, away from pressure transducers located on the casing.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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paper_title: Bifurcation based nonlinear feedback control for rotating stall in axial flow compressors

paper_content:

Classical bifurcation analysis for nonlinear dynamics is used to derive a nonlinear feedback control law that eliminates the hysteresis loop associated with rotating stall, and extends the stable operating range in axial flow compressors. The proposed control system employs pressure rise as output measurement and throttle position as the actuating signal for which both sensor and actuator exist in the current configuration of axial flow compressors. Thus, our results provide a practical solution to rotating stall control for axial flow compressors.
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paper_title: The Unstable Behavior of Low and High Speed Compressors

paper_content:

By far the greater part of our understanding about stall and surge in axial compressors comes from work on low-speed laboratory machines. As a general rule, these machines do not model the compressibility effects present in high-speed compressors and therefore doubt has always existed about the application of low-speed results to high-speed machines. In recent years interest in active control has led to a number of studies of compressor stability in engine type compressors. The instrumentation used in these experiments has been sufficiently detailed that, for the first time, adequate data is available to make direct comparisons between high-speed and low-speed compressors. This paper presents new data from an eight-stage fixed geometry engine compressor and compares this with low-speed laboratory data. The results show remarkable similarities in both the stalling and surging behaviour of the two machines, particularly when the engine compressor is run at intermediate speeds. The engine results also show that, as in the laboratory tests, surge is precipitated by the onset of rotating stall. This is true even at very high speeds where it had previously been thought that surge might be the result of a blast wave moving through the compressor. This paper therefore contains new information about high-speed compressors and confirms that low speed testing is an effective means of obtaining insight into the behaviour of high-speed machines.Copyright © 1993 by ASME
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paper_title: Integrated control of rotating stall and surge in aeroengines

paper_content:

Aeroengines operate in regimes for which both rotating stall and surge impose low flow operability limits. Thus, active control strategies designed to enhance operability of aeroengines must address both rotating stall and surge as well as their interaction. In this paper, a nonlinear control strategy is designed based on an analytical model to achieve simultaneous active control of rotating stall and surge in an axial flow compression system with relevant dynamics representative of modern aeroengines. The controller is experimentally validated on a 3-stage low-speed axial flow compression system. This rig is dynamically scaled to replicate the interaction between rotating stall and surge typical of modern aeroengines, and several experimental results are presented for this rig. For actuation, the control stategy utilizes a single plenum bleed valve with bandwidth on the order of the rotor frequency. For sensing, measurements of the circumferential asymmetry and annulus-averaged unsteadiness of the flow through the compressor are used. Experimental validation of simultaneous control of rotating stall and surge with minimal sensing and actuation requirements is viewed as an important step towards applying active control to enhance operability of compression systems in modern aeroengines.
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paper_title: Rotating Stall Control via Bifurcation Stabilization

paper_content:

Rotating stall is a fundamental aerodynamic instability in axial flow compressors, induced by nonlinear bifurcation. It effectively reduces the performance of aeroengines. In this paper classical bifurcation theory is used to derive output feedback control laws in which throttle position is employed as actuator and pressure rise as output measurement. The challenge to the proposed control system is that the critical mode of the linearized system corresponding to rotating stall is neither controllable nor observable. Using the projection method from Iooss and Joseph (1980), and Abed and Fu (1986), it is shown that linear output feedback controllers are adequate for bifurcation stabilization. Both linear and nonlinear feedback control laws are proposed and are shown to be effective in elimination of hysteresis loop associated with rotating stall, and in extending the stable operating range of axial flow compressors.
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paper_title: Modeling for control of rotating stall

paper_content:

Abstract An analytical model for control of rotating stall has been obtained from the basic fluid equations describing the process at inception. The model describes rotating stall as a traveling wave packet, sensed—in spatial components—via the Fourier decomposition of measurements obtained from a circumferential array of evenly distributed sensors (hot wires) upstream of the compressor. A set of “wiggly” inlet guide vanes (IGVs) equally spaced around the compressor annulus constitute the “forced” part of the model. Control is effected by launching waves at appropriate magnitude and phase, synthesized by spatial Fourier synthesis from individual IGV deflections. The effect of the IGV motion on the unsteady fluid process was quantified via identification experiments carried out on a low speed, single-stage axial research compressor. These experiments served to validate the theoretical model and refine key parameters in it. Further validation of the model was provided by the successful implementation of a complex-valued proportional control law, using a combination of first and second harmonic feedback; this resulted in an 18% reduction of stalling mass flow, at essentially the same pressure rise.
---
paper_title: Active Control of Rotating Stall in a Low Speed Axial Compressor

paper_content:

The onset of rotating stall has been delayed in a low speed, single-stage, axial research compressor using active feedback control. Control was implemented using a circumferential array of hot wires to sense rotating waves of axial velocity upstream of the compressor. Circumferentially travelling waves were then generated with appropriate phase and amplitude by “wiggling” inlet guide vanes driven by individual actuators. The control scheme considered the wave pattern in terms of the individual spatial Fourier components. A simple proportional control law was implemented for each harmonic. Control of the first spatial harmonic yielded an 11% decrease in the stalling mass flow, while control of the first and second harmonics together reduced the stalling mass flow by 20%. The control system was also used to measure die sine wave response of the compressor, which behaved as would be expected for a second order system.Copyright © 1991 by ASME
---
paper_title: Active suppression of aerodynamic instabilities in turbomachines

paper_content:

In this paper, we advocate a strategy for controlling a class of turbomachine instabilities, whose primitive phases can be modeled by linear theory, but that eventually grow into a performance-limiting modification of the basic flow. The phenomena of rotating stall and surge are two very different practical examples in which small disturbances grow to magnitudes such that they limit machine performance. We develop a theory that shows how an additional disturbance, driven from real-time data measured within the turbomachine, can be generated so as to realize a device with characteristics fundamentally different than those of the machine without control. For the particular compressor analyzed, the control increases the stable operating range by 20% of the mean flow. We show that active control can also be used to destabilize a compressor in an undesirable state such as nonrecoverable stall. Examination of the energetics of the controlled system shows the required control power scales with the square of the ambient disturbance level, which can be several orders of magnitude below the power of the machine. Brief mention is also made of the use of structural dynamics, rather than active control, to enhance stability.
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paper_title: Active Stabilization of Rotating Stall in a Three-Stage Axial Compressor

paper_content:

A three-stage, low speed axial research compressor has been actively stabilized by damping low amplitude circumferentially travelling waves which can grow into rotating stall. Using a circumferential array of hot wire sensors, and an array of high speed individually positioned control vanes as the actuator, the first and second spatial harmonics of the compressor were stabilized down to a characteristic slope of 0.9, yielding an 8% increase in operating flow range. Stabilization of the third spatial harmonic did not alter the stalling flow coefficient. The actuators were also used open loop to determine the forced response behavior of the compressor. A system identification procedure applied to the forced response data then yielded the compressor transfer function. The Moore-Greitzer, 2-D, stability model was modified as suggested by the measurements to include the effect of blade row time lags on the compressor dynamics. This modified Moore-Greitzer model was then used to predict both the open and closed loop dynamic response of the compressor. The model predictions agreed closely with the experimental results. In particular, the model predicted both the mass flow at stall without control and the design parameters needed by, and the range extension realized from, active control.Copyright © 1993 by ASME
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paper_title: Modeling for control of rotating stall

paper_content:

Abstract An analytical model for control of rotating stall has been obtained from the basic fluid equations describing the process at inception. The model describes rotating stall as a traveling wave packet, sensed—in spatial components—via the Fourier decomposition of measurements obtained from a circumferential array of evenly distributed sensors (hot wires) upstream of the compressor. A set of “wiggly” inlet guide vanes (IGVs) equally spaced around the compressor annulus constitute the “forced” part of the model. Control is effected by launching waves at appropriate magnitude and phase, synthesized by spatial Fourier synthesis from individual IGV deflections. The effect of the IGV motion on the unsteady fluid process was quantified via identification experiments carried out on a low speed, single-stage axial research compressor. These experiments served to validate the theoretical model and refine key parameters in it. Further validation of the model was provided by the successful implementation of a complex-valued proportional control law, using a combination of first and second harmonic feedback; this resulted in an 18% reduction of stalling mass flow, at essentially the same pressure rise.
---
paper_title: Active Control of Rotating Stall in a Low Speed Axial Compressor

paper_content:

The onset of rotating stall has been delayed in a low speed, single-stage, axial research compressor using active feedback control. Control was implemented using a circumferential array of hot wires to sense rotating waves of axial velocity upstream of the compressor. Circumferentially travelling waves were then generated with appropriate phase and amplitude by “wiggling” inlet guide vanes driven by individual actuators. The control scheme considered the wave pattern in terms of the individual spatial Fourier components. A simple proportional control law was implemented for each harmonic. Control of the first spatial harmonic yielded an 11% decrease in the stalling mass flow, while control of the first and second harmonics together reduced the stalling mass flow by 20%. The control system was also used to measure die sine wave response of the compressor, which behaved as would be expected for a second order system.Copyright © 1991 by ASME
---
paper_title: Modeling for Control of Rotating Stall in High Speed Multi-Stage Axial Compressors

paper_content:

Using a two dimensional compressible flow representation of axial compressor dynamics, a control-theoretic input-output model is derived which is of general utility in rotating stall/surge active control studies. The derivation presented here begins with a review of the fluid dynamic model, which is a 2D stage stacking technique that accounts for blade row pressure rise, loss and deviation as well as blade row and inter-blade row compressible flow. This model is extended to include the effects of the upstream and downstream geometry and boundary conditions, and then manipulated into a transfer function form that dynamically relates actuator motion to sensor measurements. Key relationships in this input-output form are then approximated using rational polynomials. Further manipulation yields an approximate model which is in standard form for studying active control of rotating stall and surge. As an example of high current relevance, the transfer function from an array of jet actuators to an array of static pressure sensors is derived. Numerical examples are also presented, including a demonstration of the importance of proper choice of sensor and actuator locations, as well as a comparison between sensor types. Under a variety of conditions, it was found that sensor locations near the front of the compressor or in the downstream gap are consistently the best choices, based on a quadratic optimization criterion and a specific 3-stage compressor model. The modeling and evaluation procedures presented here are a first step toward a rigorous approach to the design of active control systems for high speed axial compressors.Copyright © 1994 by ASME
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paper_title: Active Suppression of Rotating Stall and Surge in Axial Compressors

paper_content:

This paper reports on an experimental program in which active control was successfully applied to both rotating stall and surge in a multi-stage compressor. Two distinctly different methods were used to delay the onset of rotating stall in a four stage compressor using fast acting air injection valves. The amount of air injected was small compared to the machine mass flow, the maximum being less than 1.0%. In some compressor configurations modal perturbations were observed prior to stall. By using the air injection valves to damp out these perturbations an improvement of about 4.0% in stall margin was achieved. The second method of stall suppression was to remove emerging stall cells by injecting air in their immediate vicinity. Doing this repeatedly delayed the onset of stall, giving a stall margin improvement of about 6.0%. Further studies were conducted using a large plenum downstream of the compressor to induce the system to surge rather than stall. The resulting surge cycles were all found to be initiated by rotating stall and therefore the stall suppression systems mentioned above could also be used to suppress surge. In addition, it was possible to arrest the cyclical pulsing of a compressor already in surge.Copyright © 1991 by ASME
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paper_title: Evaluation of Approaches to Active Compressor Surge Stabilization

paper_content:

Recent work has shown that compression systems can be actively stabilized against the instability known as surge, thereby realizing a significant gain in system mass flow range. Ideally, this surge stabilization requires only a single sensor and a single actuator connected by a suitable control law. Almost all research to date has been aimed at proof of concept studies of this technique, using various actuators and sensor combinaltons. In contrast, the work reported here can be regarded as a step toward developing active control into a practical technique. In this context, the paper presents the first systematic definition of the influence of sensor and actuator selection on increasing the range of stabilized compressor performance
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paper_title: Theoretical study of sensor-actuator schemes for rotating stall control

paper_content:

A theoretical study has been conducted to determine the influence of actuator and sensor choice on active control of rotating stall in axial-flow compressors. The sensors are used to detect small amplitude traveling waves that have been observed at the inception of rotating stall in several different compressors. Control is achieved by feeding the sensed quantity back to the actuator with a suitable gain and spatial phase shift relative to the measured wave. Actuators using circumferential arrays of jets, intake ports, and movable inlet guide vanes upstream of the compressor, and valves downstream of the compressor were considered. The effect of axial velocity, static pressure, or total pressure measurement on control effectiveness was investigated. In addition, the influence of the actuator bandwidth on the performance of the controlled system was determined. The results of the study indicate that the potential for active control of rotating stall is greater than that achieved thus far with movable inlet guide vanes. Furthermore, axial velocity sensing was most effective. Actuator bandwidth affected the performance of the controlled compressors significantly, but certain actuators were affected less severely than others.
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paper_title: Experimental techniques for actuation, sensing, and measurement of rotating stall dynamics in high-speed compressors

paper_content:

This report describes the experiemental design and validation of sensing and actuation hardware to be incorporated into a NASA Lewis Research Center high-speed compressor test rig. The purpose of the control-augmented rig will be to investigate the dynamics of rotating stall in high-speed compressors, and to demonstrate stabilization of the perturbations which lead to rotating stall and surge. The overall experimental design is first described. Then the design of jet injection actuation is presented, including mechanical/fluid mechanical design rules, bandwidth limitations imposed by the electromagnetic valve, and by the fluid mechanics, and experimental validation of the actuation system. Specialized probes for 3D high-response flow measurements are then discussed, along with experimental validation of their performance. Finally, procedures for modeling and measurement of aerodynamic oscillation modes will be described.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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Title: An Overview of Rotating Stall and Surge Control for Axial Flow Compressors

Section 1: Introduction
Description 1: Introduce the topic of rotating stall and surge in axial flow compressors and the significance of controlling these phenomena to improve engine performance.

Section 2: Rotating Stall and Surge in Axial Flow Compressors
Description 2: Describe the aerodynamic instabilities known as rotating stall and surge, their characteristics, how they affect compressor performance, and the necessity for control measures.

Section 3: Moore-Greitzer Model
Description 3: Provide a review of the Moore-Greitzer model, its assumptions, derivation, and its importance in the study of nonlinear behavior of rotating stall and surge in axial flow compressors.

Section 4: Linear Perturbation Model and Feedback Control
Description 4: Discuss the development of linear control methods based on the Moore-Greitzer model, including the use of inlet guide vanes as actuators for damping rotating stall.

Section 5: Further Developments on Modeling and Control
Description 5: Summarize recent advancements in modeling and control techniques, including multi-mode models, Lyapunov stability procedures, and developments in control methods for high-speed compressors.

Section 6: Conclusion
Description 6: Summarize the findings of the survey, emphasizing the progress made and the challenges that remain in the control of rotating stall and surge in axial flow compressors.