scholarly journals Active Stabilization of Axial Compressors With Circumferential Inlet Distortion

1997 ◽  
Author(s):  
C. M. van Schalkwyk ◽  
J. D. Paduano ◽  
E. M. Greitzer ◽  
A. H. Epstein
Keyword(s):  
Transfer Function ◽  
Active Control ◽  
A Priori ◽  
Rotating Stall ◽  
Forced Response ◽  
Control Laws ◽  
Axial Compressors ◽  
Inlet Distortion ◽  
Dynamic Head ◽  
Active Stabilization

This paper describes the first experimental validation of transfer function modeling and active stabilization for axial compressors with circumferential inlet distortion. The inlet distortion experiments were carried out in a three stage low-speed compressor. Theory-experiment comparisons of steady performance, unsteady stall precursor, and forced response (transfer function) data were all used to assess a control-theoretic version of the Hynes-Greitzer distorted flow model. The tests showed good agreement between theory and data and demonstrated that a priori predictions, based on geometry and steady-state performance data, can be used to design control laws which stabilize rotating stall with inlet distortion. Based on these results, active feedback control has been used to stabilize the inlet distortion induced instability associated with rotating stall onset. The stabilization allowed stall free operation to be extended below the natural (distorted flow) stall point by up to 3.7% for a 0.8 dynamic head distortion. For a 1.9 dynamic head distortion, 40% of the mass flow range lost due to inlet distortion was regained through active control. The paper elucidates the difficulties associated with active control with distortion, and introduces a new control law that addresses many of these challenges.

Active Stabilization of Axial Compressors With Circumferential Inlet Distortion

1998 ◽  
Vol 120 (3) ◽  
pp. 431-439 ◽  
Author(s):  
C. M. van Schalkwyk ◽  
J. D. Paduano ◽  
E. M. Greitzer ◽  
A. H. Epstein
Keyword(s):  
Transfer Function ◽  
Active Control ◽  
A Priori ◽  
Rotating Stall ◽  
Forced Response ◽  
Control Laws ◽  
Axial Compressors ◽  
Inlet Distortion ◽  
Dynamic Head ◽  
Active Stabilization

This paper describes the first experimental validation of transfer function modeling and active stabilization for axial compressors with circumferential inlet distortion. The inlet distortion experiments were carried out in a three-stage low-speed compressor. Theory–experiment comparisons of steady performance, unsteady stall precursor, and forced response (transfer function) data were all used to assess a control-theoretic version of the Hynes–Greitzer distorted flow model. The tests showed good agreement between theory and data and demonstrated that a priori predictions, based on geometry and steady-state performance data, can be used to design control laws that stabilize rotating stall with inlet distortion. Based on these results, active feedback control has been used to stabilize the inlet distortion induced instability associated with rotating stall onset. The stabilization allowed stall-free operation to be extended below the natural (distorted flow) stall point by up to 3.7 percent for a 0.8 dynamic head distortion. For a 1.9 dynamic head distortion, 40 percent of the mass flow range lost due to inlet distortion was regained through active control. The paper elucidates the difficulties associated with active control with distortion, and introduces a new control law that addresses many of these challenges.

scholarly journals Modeling for Control of Rotating Stall in High Speed Multi-Stage Axial Compressors

1994 ◽  
Author(s):  
Matthew R. Feulner ◽  
Gavin J. Hendricks ◽  
James D. Paduano
Keyword(s):  
Transfer Function ◽  
Compressible Flow ◽  
Active Control ◽  
High Speed ◽  
Standard Form ◽  
Pressure Sensors ◽  
Rotating Stall ◽  
Input Output ◽  
Axial Compressors ◽  
Blade Row

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.

Rotating Stall Control in a High-Speed Stage With Inlet Distortion: Part II—Circumferential Distortion

1999 ◽  
Vol 121 (3) ◽  
pp. 517-524 ◽  
Author(s):  
Z. S. Spakovszky ◽  
C. M. van Schalkwyk ◽  
H. J. Weigl ◽  
J. D. Paduano ◽  
K. L. Suder ◽  
...  
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Axial Flow ◽  
Rotating Stall ◽  
Forced Response ◽  
Feedback Stabilization ◽  
Single Stage ◽  
Nasa Lewis Research ◽  
Control Laws ◽  
Inlet Distortion

This paper presents the first attempt to stabilize rotating stall in a single-stage transonic axial flow compressor with inlet distortion using active feedback control. The experiments were conducted at the NASA Lewis Research Center on a single-stage transonic core compressor inlet stage. An array of 12 jet injectors located upstream of the compressor was used for forced response testing and feedback stabilization. Results for a circumferential total pressure distortion of about one dynamic head and a 120 deg extent (DC(60) = 0.61) are reported in this paper. Part I (Spakovszky et al., 1999) reports results for radial distortion. Control laws were designed using empirical transfer function estimates determined from forced response results. Distortion introduces coupling between the harmonics of circumferential pressure perturbations, requiring multivariable identification and control design techniques. The compressor response displayed a strong first spatial harmonic, dominated by the well-known incompressible Moore–Greitzer mode. Steady axisymmetric injection of 4 percent of the compressor mass flow resulted in a 6.2 percent reduction of stalling mass flow. Constant gain feedback, using unsteady asymmetric injection, yielded a further range extension of 9 percent. A more sophisticated robust H∞ controller allowed a reduction in stalling mass flow of 10.2 percent relative to steady injection, yielding a total reduction in stalling mass flow of 16.4 percent.

Controls and Diagnostics Committee Best 1994 Paper Award: Modeling for Control of Rotating Stall in High-Speed Multistage Axial Compressors

1996 ◽  
Vol 118 (1) ◽  
pp. 1-10 ◽  
Author(s):  
M. R. Feulner ◽  
G. J. Hendricks ◽  
J. D. Paduano
Keyword(s):  
Transfer Function ◽  
Compressible Flow ◽  
Active Control ◽  
High Speed ◽  
Pressure Sensors ◽  
Rotating Stall ◽  
Two Dimensional ◽  
Input Output ◽  
Axial Compressors ◽  
Blade Row

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 two-dimensional stage stacking technique that accounts for blade row pressure rise, loss, and deviation as well as blade row and interblade 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 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 three-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.

scholarly journals Rotating Stall Control in a High-Speed Stage With Inlet Distortion: Part II — Circumferential Distortion

1998 ◽  
Author(s):  
Z. S. Spakovszky ◽  
C. M. van Schalkwyk ◽  
H. J. Weigl ◽  
J. D. Paduano ◽  
K. L. Suder ◽  
...  
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Axial Flow ◽  
Rotating Stall ◽  
Forced Response ◽  
Feedback Stabilization ◽  
Single Stage ◽  
Nasa Lewis Research ◽  
Control Laws ◽  
Inlet Distortion

This paper presents the first attempt to stabilize rotating stall in a single-stage transonic axial flow compressor with inlet distortion using active feedback control. The experiments were conducted at the NASA Lewis Research Center on a single-stage transonic core compressor inlet stage. An array of 12 jet injectors located upstream of the compressor was used for forced response testing and feedback stabilization. Results for a circumferential total pressure distortion of about one dynamic head and a 120° extent (DC(60) = 0.61) are reported in this paper. Part I (Spakovszky et al. (1998)) reports results for radial distortion. Control laws were designed using empirical transfer function estimates determined from forced response results. Distortion introduces coupling between the harmonics of circumferential pressure perturbations, requiring multi-variable identification and control design techniques. The compressor response displayed a strong first spatial harmonic, dominated by the well known incompressible Moore-Greitzer mode. Steady axisymmetric injection of 4% of the compressor mass flow resulted in a 6.2% reduction of stalling mass flow. Constant gain feedback, using unsteady asymmetric injection, yielded a further range extension of 9%. A more sophisticated robust controller allowed a reduction in stalling mass flow of 10.2% relative to steady injection, yielding a total reduction in stalling mass flow of 16.4%.

Active Stabilization of Rotating Stall in a Three-Stage Axial Compressor

1993 ◽  
Author(s):  
Joel M. Haynes ◽  
Gavin J. Hendricks ◽  
Alan H. Epstein
Keyword(s):  
High Speed ◽  
Travelling Waves ◽  
Axial Compressor ◽  
Open Loop ◽  
Rotating Stall ◽  
Forced Response ◽  
Flow Coefficient ◽  
Design Parameters ◽  
Time Lags ◽  
Active Stabilization

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.

Effects of Rotating Inlet Distortion on Multisage Compressor Stability

1994 ◽  
Author(s):  
J. P. Longley ◽  
H.-W. Shin ◽  
R. E. Plumley ◽  
P. D. Silkowski ◽  
I. J. Day ◽  
...  
Keyword(s):  
Theoretical Model ◽  
Stability Margin ◽  
Rotating Stall ◽  
Forced Response ◽  
Single Peak ◽  
Rotor Speed ◽  
Stall Inception ◽  
Stall Margin ◽  
Inlet Distortion ◽  
Two Peaks

In multi-spool engines, rotating stall in an upstream compressor will impose a rotating distortion on the downstream compressor, thereby affecting its stability margin. In this paper experiments are described in which this effect was simulated by a rotating screen upstream of several multistage low-speed compressors. The measurements are complemented by, and compared with, a theoretical model of multistage compressor response to speed and direction of rotation of an inlet distortion. For co-rotating distortions (i.e., distortions rotating in the same direction as rotor rotation), experiments show that the compressors exhibited significant loss in stability margin and that they could be divided into two groups according to their response. The first group exhibited a single peak in stall margin degradation when the distortion speed corresponded to roughly 50% of rotor speed. The second group showed two peaks in stall margin degradation corresponding to distortion speeds of approximately 25–35% and 70–75% of rotor speed. These new results demonstrate that multistage compressors can have more than a single resonant response. Detailed measurements suggest that the two types of behavior are linked to differences between the stall inception processes observed for the two groups of compressors and that a direct connection thus exists between the observed forced response and the unsteady flow phenomena at stall onset. For counter-rotational distortions, all the compressors tested showed minimal loss of stability margin. The results imply that counter-rotation of the fan and core compressor, or LP and HP compressors, could be a worthwhile design choice. Calculations based on the two-dimensional theoretical model show excellent agreement for the compressors which had a single peak for stall margin degradation. We take this first-of-a-kind comparison as showing that the model, though simplified, captures the essential fluid dynamic features of the phenomena. Agreement is not good for compressors which had two peaks in the curve of stall margin shift versus distortion rotation speed. The discrepancy is attributed to the three-dimensional and short length scale nature of the stall inception process in these machines; this includes phenomena that have not yet been addressed in any model.

scholarly journals Rotating Stall Control in a High-Speed Stage With Inlet Distortion: Part I — Radial Distortion

1998 ◽  
Author(s):  
Z. S. Spakovszky ◽  
H. J. Weigl ◽  
J. D. Paduano ◽  
C. M. van Schalkwyk ◽  
K. L. Suder ◽  
...  
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Transfer Functions ◽  
Axial Flow ◽  
Rotating Stall ◽  
Forced Response ◽  
Single Stage ◽  
Nasa Lewis Research ◽  
Radial Distortion ◽  
Inlet Distortion

This paper presents the first attempt to stabilize rotating stall in a single-stage transonic axial flow compressor with inlet distortion using active feedback control. The experiments were conducted at the NASA Lewis Research Center on a single-stage transonic core compressor inlet stage. An annular array of 12 jet-injectors located upstream of the rotor tip was used for forced response testing and to extend the compressor stable operating range. Results for radial distortion are reported in this paper. First, the effects of radial distortion on the compressor performance and the dynamic behavior were investigated. Control laws were designed using empirical transfer function estimates determined from forced response results. The transfer functions indicated that the compressor dynamics are decoupled with radial inlet distortion, as they are for the case of undistorted inlet flow. Single-input-single-output (SISO) control strategies were therefore used for the radial distortion controller designs. Steady axisymmetric injection of 4% of the compressor mass flow resulted in a reduction in stalling mass flow of 9.7% relative to the case with inlet distortion and no injection. Use of a robust H∞ controller with unsteady non-axisymmetric injection achieved a further reduction in stalling mass flow of 7.5%, resulting in a total reduction of 17.2%.

Rotating Stall Control in a High-Speed Stage With Inlet Distortion: Part I—Radial Distortion

1999 ◽  
Vol 121 (3) ◽  
pp. 510-516 ◽  
Author(s):  
Z. S. Spakovszky ◽  
H. J. Weigl ◽  
J. D. Paduano ◽  
C. M. van Schalkwyk ◽  
K. L. Suder ◽  
...  
Keyword(s):  
Mass Flow ◽  
High Speed ◽  
Transfer Functions ◽  
Axial Flow ◽  
Rotating Stall ◽  
Forced Response ◽  
Single Stage ◽  
Nasa Lewis Research ◽  
Radial Distortion ◽  
Inlet Distortion

This paper presents the first attempt to stabilize rotating stall in a single-stage transonic axial flow compressor with inlet distortion using active feedback control. The experiments were conducted at the NASA Lewis Research Center on a single-stage transonic core compressor inlet stage. An annular array of 12 jet-injectors located upstream of the rotor tip was used for forced response testing and to extend the compressor stable operating range. Results for radial distortion are reported in this paper. First, the effects of radial distortion on the compressor performance and the dynamic behavior were investigated. Control laws were designed using empirical transfer function estimates determined from forced response results. The transfer functions indicated that the compressor dynamics are decoupled with radial inlet distortion, as they are for the case of undistorted inlet flow. Single-input-single-output (SISO) control strategies were therefore used for the radial distortion controller designs. Steady axisymmetric injection of 4 percent of the compressor mass flow resulted in a reduction in stalling mass flow of 9.7 percent relative to the case with inlet distortion and no injection. Use of a robust H∞ controller with unsteady nonaxisymmetric injection achieved a further reduction in stalling mass flow of 7.5 percent, resulting in a total reduction of 17.2 percent.

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