Prestall Behavior of Several High-Speed Compressors

1995 ◽  
Vol 117 (1) ◽  
pp. 62-80 ◽  
Author(s):  
M. Tryfonidis ◽  
O. Etchevers ◽  
J. D. Paduano ◽  
A. H. Epstein ◽  
G. J. Hendricks
Keyword(s):  
Wave Energy ◽  
Traveling Wave ◽  
Small Amplitude ◽  
High Speed ◽  
Rotating Stall ◽  
Shaft Speed ◽  
New Techniques ◽  
Rotating Waves ◽  
Strong Function ◽  
Stall Inception

High-speed compressor data immediately prior to rotating stall inception are analyzed and compared to stability theory. New techniques for the detection of small-amplitude rotating waves in the presence of noise are detailed, and experimental and signal processing pitfalls discussed. In all nine compressors examined, rotating stall precedes surge. Prior to rotating stall inception, all the machines support small-amplitude (< 1 percent of fully developed stall) waves traveling about the circumference. Traveling wave strength and structure are shown to be a strong function of corrected speed. At low speeds, a ∼0.5 times shaft speed wave is present for hundreds of rotor revolutions prior to stall initiation. At 100 percent speed, a shaft speed rotating wave dominates, growing as stall initiation is approached (fully developed rotating stall occurs at about 1/2 of shaft speed). A new, two-dimensional, compressible hydrodynamic stability analysis is applied to the geometry of two of the compressors and gives results in agreement with data. The calculations show that, at low corrected speeds, these compressors behave predominantly as incompressible machines. The wave that first goes unstable is the 1/2 shaft frequency mode predicted by the incompressible Moore–Greitzer analysis and previously observed in low-speed compressors. Compressibility becomes important at high corrected speeds and adds axial structure to the rotating waves. At 100 percent corrected speed, one of these hitherto unrecognized compressible modes goes unstable first. The rotating frequency of this mode is constant and predicted to be approximately coincident with shaft speed at design. Thus, it is susceptible to excitation by geometric nonuniformities in the compressor. This new understanding of compressor dynamics is used to introduce the concept of traveling wave energy as a real time measure of compressor stability. Such a wave energy-based scheme is shown consistently to give an indication of low stability for significant periods (100–200 rotor revolutions) before stall initiation, even at 100 percent corrected speed.

scholarly journals Pre-Stall Behavior of Several High-Speed Compressors

1994 ◽  
Author(s):  
M. Tryfonidis ◽  
O. Etchevers ◽  
J. D. Paduano ◽  
A. H. Epstein ◽  
G. J. Hendricks
Keyword(s):  
Wave Energy ◽  
Small Amplitude ◽  
High Speed ◽  
Travelling Wave ◽  
Rotating Stall ◽  
Shaft Speed ◽  
New Techniques ◽  
Rotating Waves ◽  
Strong Function ◽  
Stall Inception

High speed compressor data immediately prior to rotating stall inception are analyzed and compared to stability theory. New techniques for the detection of small amplitude rotating waves in the presence of noise are detailed and experimental and signal processing pitfalls discussed. In all nine compressors examined, rotating stall precedes surge. Prior to rotating stall inception, all the machines support small-amplitude (<1% of fully developed stall) waves travelling about the circumference. Travelling wave strength and structure are shown to be a strong function of corrected speed. At low speeds, a −0.5 times shaft speed wave is present for hundreds of rotor revolutions prior to stall initiation. At 100% speed, a shaft speed rotating wave dominates, growing as stall initiation is approached (fully developed rotating stall occurs at about 1/2 of shaft speed). A new, 2-D, compressible hydrodynamic stability analysis is applied to the geometry of two of the compressors and gives results in agreement with data. The calculations show that, at low corrected speeds, these compressors behave predominantly as incompressible machines. The wave which first goes unstable is the 1/2 shaft frequency mode predicted by the incompressible Moore-Greitzer analysis and previously observed in low speed compressors. Compressibility becomes important at high corrected speeds and adds axial structure to the rotating waves. At 100% corrected speed, it is one of these hitherto unrecognized compressible modes which goes unstable first. The rotating frequency of this mode is constant and predicted to be approximately coincident with shaft speed at design. Thus, it is susceptible to excitation by geometric nonuniformities in the compressor. This new understanding of compressor dynamics is used to introduce the concept of travelling wave energy as a measure of compressor stability. Such a wave energy-based scheme is shown to consistently give an indication of low stability for significant periods (100–200 rotor revolutions) before stall initiation, even at 100% corrected speed.

Stall Precursor Identification in High Speed Compressor Stages Using Chaotic Time Series Analysis Methods

1996 ◽  
Author(s):  
Michelle M. Bright ◽  
Helen K. Qammar ◽  
Harald J. Weigl ◽  
James D. Paduano
Keyword(s):  
Wave Energy ◽  
Energy Method ◽  
Traveling Wave ◽  
High Speed ◽  
Pressure Fluctuations ◽  
Correlation Method ◽  
Rotating Stall ◽  
Front Face ◽  
Stable Operation ◽  
Correlation Integral

This paper presents a new technique for precursor identification in high speed compressors. The technique is a pseudo-correlation integral method referred to as the correlation method. To provide a basis for comparison, the traveling wave energy technique, which has been used extensively to study pre-stall data, is also briefly presented and applied. The correlation method has a potential advantage over the traveling wave energy method because it uses a single sensor for detection. It also requires no predisposition about the expected behavior of the data to detect “changes” in the behavior of the compressor. Both methods are used in this study to identify stall procursive events in the pressure fluctuations measured from circumferential pressure transducers located at the front face of the compressor rig. The correlation method successfully identified stall formation or changes in the compressor dynamics from data captured from four different configurations of a NASA Lewis single stage high speed compressor while it was transitioned from stable operation into stall. This paper includes an exposition on the use of nonlinear methods to identify stall precursors, a description of the methodologies used for the study, information on the NASA high speed compressor rig and experimental data acquisition, and results from the four compressor configurations. The experimental results indicate that the correlation method provides ample warning of the onset of rotating stall at high speed, in some tests on the order of 2000 rotor revolutions. Complementary features of the correlation method and the traveling wave energy method are discussed, and suggestions for future developments are made.

Rotating Waves as a Stall inception Indication in Axial Compressors

1991 ◽  
Vol 113 (2) ◽  
pp. 290-301 ◽  
Author(s):  
V. H. Garnier ◽  
A. H. Epstein ◽  
E. M. Greitzer
Keyword(s):  
Growth Rate ◽  
Small Amplitude ◽  
High Speed ◽  
Rotating Stall ◽  
Analytical Models ◽  
Stall Inception ◽  
Axial Compressors ◽  
Spatially Resolved ◽  
Two Stages ◽  
The Waves

Stall inception has been studied in two low-speed compressors (a single-stage and a three-stage) and in a high-speed three-stage compressor, using temporally and spatially resolved measurements. In all three machines, rotating stall was preceded by a period in which small-amplitude waves were observed traveling around the circumference of the machine at a speed slightly less than the fully developed rotating stall cell speed. The waves evolved smoothly into rotating stall without sharp changes in phase or amplitude, implying that, in the machines tested, the prestall waves and the fully developed rotating stall are two stages of the same phenomenon. The growth rate of these disturbances was in accord with that predicted by current analytical models. The prestall waves were observed both with uniform and with distorted inflow, but were most readily discerned with uniform inflow. Engineering uses and limitations of these waves are discussed.

Stall Inception in a Vaneless Diffuser of a Centrifugal Compressor

2003 ◽  
Author(s):  
Jeong-Seek Kang ◽  
Shin-Hyoung Kang
Keyword(s):  
Fourier Coefficient ◽  
Centrifugal Compressor ◽  
Wave Energy ◽  
Traveling Wave ◽  
Analytical Investigation ◽  
Rotating Stall ◽  
Vaneless Diffuser ◽  
Stall Inception ◽  
Cell Structures ◽  
Warning Time

This paper presents an experimental and analytical investigation of a rotating stall inception in a vaneless diffuser of a centrifugal compressor. Eight fast-response pressure transducers are equally spaced around the circumference at the inlet and exit of a parallel vaneless diffuser. Instantaneous pressure data is measured near the stall inception point and characteristics of a rotating stall, a stall-initiating mechanism, a stall precursor and its warning schemes are discussed. It is found that one-cell, two-cell and three-cell structures of small amplitude wave grow and decay repeatedly before they are fully developed to a rotating stall, which is named as “pre-cell.” When it appears, the phase of spatial Fourier coefficient increases linearly and the traveling wave energy increases. The pre-cell travels at, or slightly lower than, the speed of the fully developed rotating stall. Its growing-decaying life span is about several decades of the impeller revolution. Pre-cells of one-cell, two-cell, and three-cell structures are found to interact frequently with their growing and decaying mechanism through transferring energy from one structure to another. Two stall warning schemes are used for the stall in the vaneless diffuser. The first scheme is to detect the linear increase region in the phase of the spatial Fourier coefficient from where the according warning time is about 0.3∼1.4 sec. (300∼700 impeller revs.) The second scheme is to detect the increase of traveling wave energy from where the according warning time is about 0.2∼2.3 sec. (200∼1200 impeller revs.) These warning schemes are useful because their warning time is long enough to be applied in active control of a compressor stall.

scholarly journals Rotating Waves as a Stall Inception Indication in Axial Compressors

1990 ◽  
Author(s):  
V. H. Garnier ◽  
A. H. Epstein ◽  
E. M. Greitzer
Keyword(s):  
Growth Rate ◽  
Small Amplitude ◽  
High Speed ◽  
Rotating Stall ◽  
Analytical Models ◽  
Stall Inception ◽  
Axial Compressors ◽  
Spatially Resolved ◽  
Two Stages ◽  
The Waves

Stall inception has been studied in two low speed compressors (a single-stage and a three-stage) and in a high speed three-stage compressor, using temporally and spatially resolved measurements. In all three machines, rotating stall was preceded by a period in which small amplitude waves were observed travelling around the circumference of the machine at a speed slightly less than the fully developed rotating stall cell speed. The waves evolved smoothly into rotating stall without sharp changes in phase or amplitude, implying that, in the machines tested, the prestall waves and the fully developed rotating stall are two stages of the same phenomenon. The growth rate of these disturbances was in accord with that predicted by current analytical models. The prestall waves were observed both with uniform and with distorted inflow, but were most readily discerned with uniform inflow. Engineering uses and limitations of these waves are discussed.

Stall Precursor Identification in High-Speed Compressor Stages Using Chaotic Time Series Analysis Methods

1997 ◽  
Vol 119 (3) ◽  
pp. 491-499 ◽  
Author(s):  
M. M. Bright ◽  
H. K. Qammar ◽  
H. J. Weigl ◽  
J. D. Paduano
Keyword(s):  
Wave Energy ◽  
Energy Method ◽  
Traveling Wave ◽  
High Speed ◽  
Pressure Fluctuations ◽  
Correlation Method ◽  
Rotating Stall ◽  
Front Face ◽  
Stable Operation ◽  
Correlation Integral

This paper presents a new technique for precursor identification in high-speed compressors. The technique is a pseudo-correlation integral method referred to as the correlation method. To provide a basis for comparison, the traveling wave energy technique, which has been used extensively to study prestall data, is also briefly presented and applied. The correlation method has a potential advantage over the traveling wave energy method because it uses a single sensor for detection. It also requires no predisposition about the expected behavior of the data to detect “changes” in the behavior of the compressor. Both methods are used in this study to identify stall precursive events in the pressure fluctuations measured from circumferential pressure transducers located at the front face of the compressor rig. The correlation method successfully identified stall formation or changes in the compressor dynamics from data captured from four different configurations of a NASA Lewis single-stage high-speed compressor while it was transitioned from stable operation into stall. This paper includes an exposition on the use of nonlinear methods to identify stall precursors, a description of the methodologies used for the study, information on the NASA high-speed compressor rig and experimental data acquisition, and results from the four compressor configurations. The experimental results indicate that the correlation method provides ample warning of the onset of rotating stall at high speed, in some tests on the order of 2000 rotor revolutions. Complementary features of the correlation method and the traveling wave energy method are discussed, and suggestions for future developments are made.

Stall Inception in a High Speed Centrifugal Compressor During Speed Transients

2017 ◽  
Author(s):  
Fangyuan Lou ◽  
John C. Fabian ◽  
Nicole L. Key
Keyword(s):  
Heat Transfer ◽  
Centrifugal Compressor ◽  
High Speed ◽  
Flow Instability ◽  
Leading Edge ◽  
Fast Response ◽  
Rotating Stall ◽  
Transient Performance ◽  
Stall Inception ◽  
Pressure Transducers

The inception and evolution of rotating stall in a high-speed centrifugal compressor are characterized during speed transients. Experiments were performed in the Single Stage Centrifugal Compressor (SSCC) facility at Purdue University and include speed transients from sub-idle to full speed at different throttle settings while collecting transient performance data. Results show a substantial difference in the compressor transient performance for accelerations versus decelerations. This difference is associated with the heat transfer between the flow and the hardware. The heat transfer from the hardware to the flow during the decelerations locates the compressor operating condition closer to the surge line and results in a significant reduction in surge margin during decelerations. Additionally, data were acquired from fast-response pressure transducers along the impeller shroud, in the vaneless space, and along the diffuser passages. Two different patterns of flow instabilities, including mild surge and short-length-scale rotating stall, are observed during the decelerations. The instability starts with a small pressure perturbation at the impeller leading edge and quickly develops into a single-lobe rotating stall burst. The stall cell propagates in the direction opposite of impeller rotation at approximately one third of the rotor speed. The rotating stall bursts are observed in both the impeller and diffuser, with the largest magnitudes near the diffuser throat. Furthermore, the flow instability develops into a continuous high frequency stall and remains in the fully developed stall condition.

Fan Stability With Leading Edge Damage: Blind Prediction and Validation

2021 ◽  
Author(s):  
E. J. Gunn ◽  
T. Brandvik ◽  
M. J. Wilson ◽  
R. Maxwell
Keyword(s):  
Supersonic Flow ◽  
High Speed ◽  
Leading Edge ◽  
Rotating Stall ◽  
Stall Inception ◽  
Blind Prediction ◽  
Edge Damage ◽  
The Impact ◽  
Operating Points ◽  
Relative Flow

Abstract This paper considers the impact of a damaged leading edge on the stall margin and stall inception mechanisms of a transonic, low pressure ratio fan. The damage takes the form of a squared-off leading edge over the upper half of the blade. Full-annulus, unsteady CFD simulations are used to explain the stall inception mechanisms for the fan at low- and high-speed operating points. A combination of steady and unsteady simulations show that the fan is predicted to be sensitive to leading edge damage at low speed, but insensitive at high speed. This blind prediction aligns well with rig test data. The difference in response is shown to be caused by the change between subsonic and supersonic flow regimes at the leading edge. Where the inlet relative flow is subsonic, rotating stall is initiated by growth and propagation of a subsonic leading edge flow separation. This separation is shown to be triggered at higher mass flow rates when the leading edge is damaged, reducing the stable flow range. Where the inlet relative flow is supersonic, the flow undergoes a supersonic expansion around the leading edge, creating a supersonic flow patch terminated by a shock on the suction surface. Rotating stall is triggered by growth of this separation, which is insensitive to leading edge shape. This creates a marked difference in sensitivity to damage at low- and high-speed operating points.

scholarly journals Stall Inception in a High-Speed Low Aspect Ratio Fan Including the Effects of Casing Treatments

1994 ◽  
Author(s):  
S. E. Gorrell ◽  
P. M. Russler
Keyword(s):  
Aspect Ratio ◽  
High Speed ◽  
Static Pressure ◽  
Pressure Ratio ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Stall Inception ◽  
Casing Treatment ◽  
Low Aspect Ratio ◽  
Casing Treatments

The stall inception process in high-speed compressor components is important to understand in order to increase stage loading while maintaining stall margin. This paper presents the results of an in depth experimental investigation on the stall inception of a two stage, high-speed, low aspect ratio fan that is representative of current operational commercial and military fan technology. High-response static pressure measurements are presented which detail the stall inception process of the fan under various operating conditions. These conditions include: varied corrected speeds, a smooth case, a circumferential groove casing treatment, and a recirculating cavity casing treatment. Stage pressure characteristics and radial pressure ratio profiles are presented for the different operating conditions. The stage performance data, together with the static pressure data, are analyzed to provide a clear and thorough understanding of the stall inception process and how the process may vary under different conditions. Experimental results show that a stage may stall on the positive, neutral, or negative sloped part of the pressure characteristic. The three casing treatments had a significant effect on the rotor tip flow and these variations changed the stall inception path of the fan. Stall inception was characterized by the formation of a stall inception cell which grew to fully developed rotating stall. Properties affected by the changing tip flow include the stall inception duration, stall inception cell frequency, existence of modal waves, duration of modal waves, and modal wave frequency. In some instances modal waves appear to play a role in stall inception, in others they do not.

Stall Inception and Development in an Axial Flow Aeroengine

1994 ◽  
Vol 116 (2) ◽  
pp. 216-225 ◽  
Author(s):  
A. G. Wilson ◽  
C. Freeman
Keyword(s):  
High Speed ◽  
Engine Speed ◽  
Static Pressure ◽  
Flow Instability ◽  
Axial Flow ◽  
Fast Response ◽  
Rotating Stall ◽  
Flow Disturbance ◽  
Stall Inception ◽  
Small Flow

This paper describes the phenomenon of stall and surge in an axial flow aeroengine using fast response static pressure measurements from the compressor of a Rolls-Royce VIPER engine. It details the growth of flow instability at various speeds, from a small zone of stalled fluid involving only a few blades into the violent surge motion of the entire machine. Various observations from earlier theoretical and compressor rig results are confirmed by these new engine measurements. The main findings are as follows: (1) The point of stall inception moves rearward as engine speed increases, and is shown to be simply related to the axial matching of the compressor. (2) The final unstable operation of the machine can be divided into rotating stall at low speed and surge or multiple surge at high speed. (3) The inception process is independent of whether the final unstable operation is rotating stall or multiple surge. (4) Stall/surge always starts as a circumferentially small flow disturbance, rotating around the annulus at some fraction of rotor speed.

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