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

1994 ◽  
Vol 116 (2) ◽  
pp. 226-239 ◽  
Author(s):  
J. M. Haynes ◽  
G. J. Hendricks ◽  
A. H. Epstein
Keyword(s):  
Axial Compressor ◽  
Open Loop ◽  
Rotating Stall ◽  
Forced Response ◽  
Flow Coefficient ◽  
Design Parameters ◽  
Time Lags ◽  
Response Data ◽  
Active Stabilization ◽  
Low Amplitude

A three-stage, low-speed axial research compressor has been actively stabilized by damping low-amplitude circumferentially traveling waves, which can grow into rotating stall. Using a circumferential array of hot-wire sensors, and an array of highspeed 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 percent 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 two-dimensional 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.

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.

Characteristics of Stable Rotating Stall Cells in an Axial Compressor

2017 ◽  
Author(s):  
Adam R. Hickman ◽  
Scott C. Morris
Keyword(s):  
Flow Field ◽  
High Speed ◽  
Pressure Ratio ◽  
Pressure Sensors ◽  
Axial Compressor ◽  
Field Measurements ◽  
Rotating Stall ◽  
Flow Coefficient ◽  
Stable Operation ◽  
Double Phase

Flow field measurements of a high-speed axial compressor are presented during pre-stall and post-stall conditions. The paper provides an analysis of measurements from a circumferential array of unsteady shroud static pressure sensors during stall cell development. At low-speed, the stall cell approached a stable size in approximately two rotor revolutions. At higher speeds, the stall cell developed within a short amount of time after stall inception, but then fluctuated in circumferential extent as the compressor transiently approached a stable post-stall operating point. The size of the stall cell was found to be related to the annulus average flow coefficient. A discussion of Phase-Locked Average (PLA) statistics on flow field measurements during stable operation is also included. In conditions where rotating stall is present, flow field measurements can be Double Phase-Locked Averaged (DPLA) using a once-per-revolution (1/Rev) pulse and the period of the stall cell. The DPLA method provides greater detail and understanding into the structure of the stall cell. DPLA data indicated that a stalled compressor annulus can be considered to contained three main regions: over-pressurized passages, stalled passages, and recovering passages. Within the over-pressured region, rotor passages exhibited increased blade loading and pressure ratio compared to pre-stall values.

1997 Best Paper Award—Controls and Diagnostics Committee: Active Stabilization of Rotating Stall and Surge in a Transonic Single-Stage Axial Compressor

1998 ◽  
Vol 120 (4) ◽  
pp. 625-636 ◽  
Author(s):  
H. J. Weigl ◽  
J. D. Paduano ◽  
L. G. Fre´chette ◽  
A. H. Epstein ◽  
E. M. Greitzer ◽  
...  
Keyword(s):  
Mass Flow ◽  
Control Strategies ◽  
Axial Compressor ◽  
Gain Control ◽  
Rotating Stall ◽  
Forced Response ◽  
Single Stage ◽  
Rotor Speed ◽  
Stall Inception ◽  
Spatial Harmonics

Rotating stall and surge have been stabilized in a transonic single-stage axial compressor using active feedback control. The control strategy is to sense upstream wall static pressure patterns and feed back the signal to an annular array of twelve separately modulated air injectors. At tip relative Mach numbers of 1.0 and 1.5 the control achieved 11 and 3.5 percent reductions in stalling mass flow, respectively, with injection adding 3.6 percent of the design compressor mass flow. The aerodynamic effects of the injection have also been examined. At a tip Mach number, Mtip, of 1.0, the stall inception dynamics and effective active control strategies are similar to results for low-speed axial compressors. The range extension was achieved by individually damping the first and second spatial harmonics of the prestall perturbations using constant gain feedback. At a Mtip of 1.5 (design rotor speed), the prestall dynamics are different than at the lower speed. Both one-dimensional (surge) and two-dimensional (rotating stall) perturbations needed to be stabilized to increase the compressor operating range. At design speed, the instability was initiated by approximately ten rotor revolutions of rotating stall followed by classic surge cycles. In accord with the results from a compressible stall inception analysis, the zeroth, first, and second spatial harmonics each include more than one lightly damped mode, which can grow into the large amplitude instability. Forced response testing identified several modes traveling up to 150 percent of rotor speed for the first three spatial harmonics; simple constant gain control cannot damp all of these modes and thus cannot stabilize the compressor at this speed. A dynamic, model-based robust controller was therefore used to stabilize the multiple modes that comprise the first three harmonic perturbations in this transonic region of operation.

Effect of the Stator Hub Configuration and Stage Design Parameters on Aerodynamic Loss in Axial Compressors

2014 ◽  
Author(s):  
Sungho Yoon ◽  
Rudolf Selmeier ◽  
Patricia Cargill ◽  
Peter Wood
Keyword(s):  
Pressure Loss ◽  
Axial Compressor ◽  
Flow Coefficient ◽  
Design Stage ◽  
Design Parameters ◽  
Leakage Flow ◽  
Design Decision ◽  
Leakage Loss ◽  
Stage Design ◽  
Degree Of Reaction

The choice of the stator hub configuration (i.e. cantilevered versus shrouded) is an important design decision in the preliminary design stage of an axial compressor. Therefore, it is important to understand the effect of the stator hub configuration on the aerodynamic performance. In particular, the stator hub configuration fundamentally affects the leakage flow across the stator. The effect of the stator hub configuration on the leakage flow and its consequent aerodynamic mixing loss with the main flow within the stator row is systematically investigated in this study. In the first part of the paper, a simple model is formulated to estimate the leakage loss across the stator hub as a function of fundamental stage design parameters, such as the flow coefficient, the degree of reaction and the work coefficient, in combination with some relevant geometric parameters including the clearance/span, the pitch-to-chord ratio and the number of seals for the shrouded geometry. The model is exercised in order to understand the effect of each of these design parameters on the leakage loss. It is found that, for a given flow coefficient and work coefficient, the leakage loss across the stator is substantially influenced by the degree of reaction. When a cantilevered stator is compared with a shrouded stator with a single seal at the same clearance, it is shown that a shrouded configuration is generally favored as a higher degree of reaction is selected, whereas a cantilevered configuration is desirable for a lower degree of reaction. Further to this, it is demonstrated that, for shrouded stators, an additional aerodynamic benefit can be achieved by using multiple seals. The second part of the paper investigates the effect of the rotating surfaces. Traditionally, only the pressure loss has been considered for stators. However, the current advanced CFD generally includes the leakage path with associated rotating surfaces, which impart energy to the flow. It is shown that the conventional loss coefficient, based on considering only the pressure loss, is misleading when hub leakage flows are modeled in detail, because there is energy addition due to the rotation of the hub or the shroud seals for the cantilevered stator and the shrouded stator, respectively. The calculation of the entropy generation across the stator is a better measure of relative performance when comparing two different stator hub configurations with detailed CFD.

scholarly journals Experimental Development of a Jet Injection Model for Rotating Stall Control

1998 ◽  
Author(s):  
Huu Duc Vo ◽  
James D. Paduano
Keyword(s):  
Rotating Stall ◽  
Forced Response ◽  
Flow Coefficient ◽  
Jet Injection ◽  
Experimental Development ◽  
Injection Model ◽  
Downstream Flow ◽  
The Right ◽  
Control Feedback ◽  
Stall Control

The effectiveness of jet actuation for active modal control of rotating stall is investigated experimentally. The dominant physical effects of injection, such as momentum and mass addition, are elucidated. The results indicate that several of the theoretical assumptions used in past studies of jet injection for rotating stall control must be revised. An updated model of the compression system with jet actuation which allows for the effect of control feedback dynamics to be adequately characterized is developed and verified with forced response measurements. It predicts the right trends of movement of the critical pole. Preliminary active control results are presented, among which is a 5.5% range extension in downstream flow coefficient.

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 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.

Effect of the Stator Hub Configuration and Stage Design Parameters on Aerodynamic Loss in Axial Compressors

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
Sungho Yoon ◽  
Rudolf Selmeier ◽  
Patricia Cargill ◽  
Peter Wood
Keyword(s):  
Pressure Loss ◽  
Axial Compressor ◽  
Flow Coefficient ◽  
Design Stage ◽  
Design Parameters ◽  
Leakage Flow ◽  
Design Decision ◽  
Leakage Loss ◽  
Stage Design ◽  
Degree Of Reaction

The choice of the stator hub configuration (i.e., cantilevered versus shrouded) is an important design decision in the preliminary design stage of an axial compressor. Therefore, it is important to understand the effect of the stator hub configuration on the aerodynamic performance. In particular, the stator hub configuration fundamentally affects the leakage flow across the stator. The effect of the stator hub configuration on the leakage flow and its consequent aerodynamic mixing loss with the main flow within the stator row is systematically investigated in this study. In the first part of the paper, a simple model is formulated to estimate the leakage loss across the stator hub as a function of fundamental stage design parameters, such as the flow coefficient, the degree of reaction, and the work coefficient, in combination with some relevant geometric parameters including the clearance/span, the pitch-to-chord ratio, and the number of seals for the shrouded geometry. The model is exercised in order to understand the effect of each of these design parameters on the leakage loss. It is found that, for a given flow coefficient and work coefficient, the leakage loss across the stator is substantially influenced by the degree of reaction. When a cantilevered stator is compared with a shrouded stator with a single seal at the same clearance, it is shown that a shrouded configuration is generally favored as a higher degree of reaction is selected, whereas a cantilevered configuration is desirable for a lower degree of reaction. Further to this, it is demonstrated that, for shrouded stators, an additional aerodynamic benefit can be achieved by using multiple seals. The second part of the paper investigates the effect of the rotating surfaces. Traditionally, only the pressure loss has been considered for stators. However, the current advanced computational fluid dynamics (CFD) generally includes the leakage path with associated rotating surfaces, which impart energy to the flow. It is shown that the conventional loss coefficient, based on considering only the pressure loss, is misleading when hub leakage flows are modeled in detail, because there is energy addition due to the rotation of the hub or the shroud seals for the cantilevered stator and the shrouded stator, respectively. The calculation of the entropy generation across the stator is a better measure of relative performance when comparing two different stator hub configurations with detailed CFD.

Experimental Investigation of the Unsteady Tip Clearance Flow in a Low-Speed Axial Contra-Rotating Compressor

2018 ◽  
Author(s):  
Shaoyuan Yue ◽  
Yangang Wang ◽  
Liguo Wei ◽  
Hao Wang ◽  
Shuanghou Deng
Keyword(s):  
Correlation Analysis ◽  
Dynamic Pressure ◽  
Axial Compressor ◽  
Rotating Stall ◽  
Tip Clearance ◽  
Flow Coefficient ◽  
Tip Clearance Flow ◽  
Cross Correlation Analysis ◽  
Clearance Flow ◽  
Tip Clearance Vortex

This paper experimentally investigated the evolution of the tip clearance flow of a CRAC (Contra-Rotating Axial Compressor) test rig by means of high-response dynamic pressure measurements. The unsteady pressure field along both chordwise and circumferential directions in the tip clearance is recorded. The tip clearance vortex trajectory is captured using RMS (Root-Mean Square) method. Pressure spectrum analysis indicates that the unsteadiness of tip clearance vortex occurred when the flow coefficient approaches low enough even in the stable operating point. The unsteadiness of tip clearance vortex gets stronger as the flow coefficient drops until rotating stall occurs. According to this feature, the auto-correlation analysis and the cross-correlation analysis combined probability statistics method are used to work as pre-stall warning methods. In addition to, rotating instability which is caused by disturbances propagating along circumferential direction occurred at some flow condition.

scholarly journals A Gas Turbine Dynamic Model for Simulation and Control

1998 ◽  
Author(s):  
Horacio Perez-Blanco ◽  
Todd B. Henricks
Keyword(s):  
Gas Turbine ◽  
Computer Model ◽  
Gas Turbines ◽  
Flow Coefficient ◽  
Design Parameters ◽  
Time Lags ◽  
Start Up ◽  
Combined Simulation ◽  
Electrical Generation ◽  
And Control

The useful life of gas turbines and the availability of power after start-up depend on their transient response. For this reason, several articles have been written on the dynamic simulation of gas turbine systems in electrical generation, cogeneration, and marine applications. The simulations typically rely on performance maps and time lags extracted from manufacturer’s specifications. This work was undertaken to increase the generality of turbine models over what can be obtained from performance maps. The paper describes a mathematical computer model developed to investigate the dynamic response of a simple single-shaft gas turbine system. The model uses design parameters normally incorporated in gas turbine design (e.g. load coefficient, flow coefficient, and deHaller Number) as well as compressor and turbine stage geometry and compressor and turbine material properties. A dynamic combustion chamber model is also incorporated. Other input parameters are included to enable the model to be adaptable to various system sizes and environments. The model was formulated in a graphical interface, and the results of several trials are displayed. The influence of important parameters (e.g. fuel-air ratio, IGVs, load, efficiencies) on turbine response from a “cold” start and from steady-state is studied. To gain further insights into the response, a start-up procedure similar to that reported in the literature for an industrial gas turbine system is simulated. Because of the approach used, the computer model is easily adaptable to further improvements and combined simulation of turbines and control systems.

Sign in / Sign up

Export Citation Format

Share Document