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.

Experimental Investigation and Characterization of the Rotating Stall in a High Pressure Centrifugal Compressor: Part IV — Impeller Influence on Diffuser Stability

2003 ◽  
Author(s):  
A. Cellai ◽  
G. Ferrara ◽  
L. Ferrari ◽  
C. P. Mengoni ◽  
L. Baldassarre
Keyword(s):  
Experimental Investigation ◽  
High Pressure ◽  
Centrifugal Compressor ◽  
Rotating Stall ◽  
Radius Ratio ◽  
Vaneless Diffuser ◽  
Stall Inception ◽  
Last Stage ◽  
And Diffusion

Vaneless diffuser rotating stall is a major problem for centrifugal compressors since it is a limit to their working range. In particular the last stage seems to be the most critical. In the literature some good correlations for predicting stall inception can be found but they do not adequately cover the case of the last stage configuration, especially for very low blade-outlet-width-to-impeller-radius-ratio impellers typically used in high-pressure applications. Extensive research has been performed to define diffuser stall limits for this family of stages: three impellers characterized by different blade-outlet-width-to-impeller-radius-ratios are tested with different diffuser configurations (different pinch shapes, diffuser widths and diffusion ratios). Part I and II report the results of these geometry modifications on diffuser stability for the first impeller. Part III, those for the second impeller. In this part the comparison of these results in terms of impeller influence on diffuser stability is reported.

Experimental Investigation and Characterization of the Rotating Stall in a High Pressure Centrifugal Compressor: Part I — Influence of Diffuser Geometry on Stall Inception

2002 ◽  
Author(s):  
G. Ferrara ◽  
L. Ferrari ◽  
C. P. Mengoni ◽  
M. De Lucia ◽  
L. Baldassarre
Keyword(s):  
Centrifugal Compressor ◽  
Experimental Tests ◽  
Rotating Stall ◽  
Main Task ◽  
Test Results ◽  
Vaneless Diffuser ◽  
Stall Inception ◽  
Last Stage ◽  
Prediction Criteria

Extensive research on centrifugal compressors has been planned to define diffuser stall limits for a group of stages characterized by low blade-outlet-width-to-impeller-radius-ratio. Very little data is available on this centrifugal compressor family, especially for the last stage configuration. In addition, the most important stall diffuser prediction criteria barely cover this machine type. Many experimental tests have been planned to investigate several geometry variations. A simulated stage with a backward channel upstream, a 2D impeller with a vaneless diffuser and a constant cross section volute downstream constitute the basic geometry. Several diffuser geometries with different widths, pinch shapes, diffusion ratios were tested. Test results and conclusions are shown in the paper in terms of critical diffuser inlet flow angles, flow coefficients at stall inception and stage working ranges. The main task of the present work is to increase the knowledge and the amount of available data to characterize rotating stall phenomena, in particular for very narrow stages.

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.

Effects of Non-Axisymmetric Volute on Rotating Stall in the Vaneless Diffuser of a Centrifugal Compressor

2020 ◽  
Author(s):  
Zitian Niu ◽  
Zhenzhong Sun ◽  
Baotong Wang ◽  
Xinqian Zheng
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Centrifugal Compressor ◽  
Stability Boundary ◽  
Rotating Stall ◽  
Evolution Process ◽  
Vaneless Diffuser ◽  
Unstable Flow ◽  
Centrifugal Compressors ◽  
Specific Location

Abstract Rotating stall is an important unstable flow phenomenon that leads to performance degradation and limits the stability boundary in centrifugal compressors. The volute is one of the sources to induce the non-axisymmetric flow in a centrifugal compressor, which has an important effect on the performance of compressors. However, the influence of volute on rotating stall is not clear. Therefore, the effects of volute on rotating stall by experimental and numerical simulation have been explored in this paper. It’s shown that one rotating stall cell generates in a specific location and disappears in another specific location of the vaneless diffuser as a result of the distorted flow field caused by the volute. Also, the cells cannot stably rotate in a whole circle. The frequency related to rotating stall captured in the experiment is 43.9% of the impeller passing frequency (IPF), while it is 44.7% of IPF captured by three-dimensional unsteady numerical simulation, which proves the accuracy of the numerical method in this study. The numerical simulation further reveals that the stall cell initialized in a specific location can be split into several cells during the evolution process. The reason for this is that the blockage in the vaneless diffuser induced by rotating stall is weakened by the mainstream from the impeller exit to make one initialized cell disperse into several ones. The volute has an important influence on the generation and evolution process of the rotating stall cells of compressors. By optimizing volute geometry to reduce the distortion of the flow field, it is expected that rotating stall can be weakened or suppressed, which is helpful to widen the operating range of centrifugal compressors.

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.

Flow Behavior of a Centrifugal Compressor With Vaneless Diffuser at Design and Off Design Conditions

2012 ◽  
Author(s):  
Chuang Gao ◽  
Weiguang Huang ◽  
Haiqing Liu ◽  
Hongwu Zhang ◽  
Jundang Shi
Keyword(s):  
Centrifugal Compressor ◽  
Flow Behavior ◽  
Travelling Waves ◽  
Leading Edge ◽  
Pressure Oscillation ◽  
Rotating Stall ◽  
Vaneless Diffuser ◽  
Unstable Flow ◽  
Flow Recirculation ◽  
Static Performance

This paper concerns with the numerical and experimental aspects of both steady and unsteady flow behavior in a centrifugal compressor with vaneless diffuser and downstream collector. Specifically, the appearance of flow instabilities i.e., rotating stall and surge is investigated in great detail. As the first step, the static performance of both stage and component was analyzed and possible root cause of system surge was put forward based on the classic stability theory. Then the unsteady pressure data was utilized to find rotating stall and surge in frequency domain which could be classified as mild surge and deep surge. With the circumferentially installed transducers at impeller inlet, backward travelling waves during stall ramp could be observed. The modes of stall waves could be clearly identified which is caused by impeller leading edge flow recirculation at Mu = 0.96. However, for the unstable flow at Mu = 1.08, the system instability seems to be caused by reversal flow in vaneless diffuser where the pressure oscillation was strongest. Thus steady numerical simulation were performed and validated with the experimental performance data. With the help of numerical analysis, the conjectures are proved.

Experimental Characterization of Vaneless Diffuser Rotating Stall: Part VI — Reduction of Three Impeller Results

2006 ◽  
Author(s):  
E. A. Carnevale ◽  
G. Ferrara ◽  
L. Ferrari ◽  
L. Baldassarre
Keyword(s):  
Rotating Stall ◽  
Radius Ratio ◽  
Vaneless Diffuser ◽  
Cross Sectional ◽  
Stall Inception ◽  
Return Channel ◽  
Geometrical Scale ◽  
And Diffusion ◽  
Basic Configuration

Vaneless diffuser rotating stall is a major problem for centrifugal compressors since it is a limit to their working range. In the literature some good correlations for predicting stall inception can be found but they do not adequately cover the case of the last stage configuration, especially for very low blade-outlet-width-to-impeller-radius-ratio impellers typically used in high-pressure applications. Extensive research has been performed to define diffuser stall limits for this family of stages: three impellers characterized by different blade-outlet-width-to-impeller-radius-ratios have been tested with different diffuser configurations (different pinch shapes, diffuser widths and diffusion ratios). The basic configuration comprises a 1:1 geometrical scale stage with a return channel upstream, a 2D impeller with a vaneless diffuser and a volute with a constant cross sectional area downstream. Several diffuser types with different widths and diffusion ratios were tested. Detailed experimental results have been reported in previous works [1, 2, 3 and 4]. In this paper experimental data are reviewed in order to analyze impeller influence on diffuser stability and to develop some summarizing consideration on stall behavior of vaneless diffuser for impeller with low blade-outlet-width-to-impeller-radius-ratio.

scholarly journals Rotating Stall in Centrifugal Compressor Vaneless Diffuser: Experimental Analysis of Geometrical Parameters Influence on Phenomenon Evolution

2004 ◽  
Vol 10 (6) ◽  
pp. 433-442 ◽  
Author(s):  
Giovanni Ferrara ◽  
Lorenzo Ferrari ◽  
Leonardo Baldassarre
Keyword(s):  
Centrifugal Compressor ◽  
Dynamic Pressure ◽  
Pressure Sensors ◽  
Experimental Tests ◽  
Fast Response ◽  
Rotating Stall ◽  
Geometrical Parameters ◽  
Vaneless Diffuser ◽  
Response Dynamic ◽  
Frequency Domains

The rotating stall is a key problem for achieving a good working range of a centrifugal compressor and a detailed understanding of the phenomenon is very important to anticipate and avoid it. Many experimental tests have been planned by the authors to investigate the influence on stall behavior of different geometrical configurations. A stage with a backward channel upstream, a 2-D impeller with a vaneless diffuser and a constant cross-section volute downstream, constitute the basic configuration. Several diffuser types with different widths, pinch shapes, and diffusion ratios were tested. The stage was instrumented with many fast response dynamic pressure sensors so as to characterize inception and evolution of the rotating stall. This kind of analysis was carried out both in time and in frequency domains. The methodology used and the results on phenomenon evolution will be presented and discussed in this article.

scholarly journals Estimation of the Aerodynamic Force Induced by Vaneless Diffuser Rotating Stall in Centrifugal Compressor Stages

2016 ◽  
Vol 101 ◽  
pp. 734-741 ◽  
Author(s):  
Michele Marconcini ◽  
Alessandro Bianchini ◽  
Matteo Checcucci ◽  
Davide Biliotti ◽  
Marco Giachi ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Aerodynamic Force ◽  
Rotating Stall ◽  
Vaneless Diffuser

Geometric considerations in the capture of localized flow reversal in centrifugal compressor vaneless diffusers using steady state simulations

2016 ◽  
Vol 231 (21) ◽  
pp. 3959-3973
Author(s):  
Chris Clarke ◽  
Russell Marechale ◽  
Abraham Engeda ◽  
Michael Cave
Keyword(s):  
Experimental Data ◽  
Steady State ◽  
Centrifugal Compressor ◽  
Flow Characteristics ◽  
Rotating Stall ◽  
Flow Reversal ◽  
Contour Plot ◽  
Vaneless Diffuser ◽  
Impeller Blade ◽  
Steady State Simulation

A steady state simulation procedure is proposed to capture localized flow reversal inside of a centrifugal compressor vaneless diffuser. The procedure was performed on 12 compressor stages of varying geometry for speed lines of 13,100, 19,240, and 21,870 r/min. The simulations were run for all points from choke to surge including the experimentally determined rotating stall onset point. The experimental data and geometry were provided by Solar Turbines Inc. San Diego, CA. It was found possible to capture localized flow reversal inside of a vaneless diffuser using a steady state simulation. The results showed that using a geometric parameter, comparing the diffuser width, b4, to the impeller blade pitch distance, dpitch, it could be determined whether or not a steady state simulation could capture localized flow reversal. For values of b4/dpitch beneath 0.152 flow reversal could not be captured. But, for values of b4/dpitch above 0.177 localized flow reversal was captured. For values between 0.152 and 0.177, no conclusions could be drawn. Where possible, experimental data were compared against the diffuser inlet and outlet numerical profiles and the meridional contour plot. These comparisons served to validate the approach used in this article. These validations showed that the procedure defined herein is accurate and trustworthy within a specific range of geometric and flow characteristics. There are two other conclusions. First, the b4/dpitch parameter helps to define the type of flow breakdown. For b4/dpitch below 0.152, the flow breaks down in the circumferential direction, but for values of b4/dpitch above 0.177, the flow breaks down in the span-wise direction. Second, the simulations were able to capture instances of localized flow reversal before rotating stall onset. This concludes that localized flow reversal is not the determining factor in rotating stall onset as has been suggested by other investigators.

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