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

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.

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Detection of vaneless diffuser rotating stall by means of dynamic pressure sensors and acoustic measurements

E3S Web of Conferences ◽

10.1051/e3sconf/202131211007 ◽

2021 ◽

Vol 312 ◽

pp. 11007

Author(s):

Luca Romani ◽

Lorenzo Bosi ◽

Alberto Baroni ◽

Lorenzo Toni ◽

Davide Biliotti ◽

...

Keyword(s):

Dynamic Pressure ◽

Pressure Sensors ◽

Experimental Tests ◽

Rotating Stall ◽

Accurate Estimation ◽

Sufficient Information ◽

Acoustic Measurements ◽

Vaneless Diffuser ◽

Test Rig ◽

Ensemble Averaging

An accurate estimation of rotating stall is one of the key technologies for high-pressure centrifugal compressors. Several techniques have been proposed to detect the stall onset; inter alia, few dynamic pressure probes have been shown to not only properly detect the phenomenon, but also reconstruct the stall characteristics after an ensemble averaging approach. The massive use of this technique in the field is, however, not a common practice yet. In the present study, the use of dynamic pressure probes has been combined with that of an environmental microphone to evaluate the prospects of this latter for a possible stall onset detection. To this end, experimental tests have been carried out in the experimental test rig of the Department of Industrial Engineering (DIEF) of Università degli Studi di Firenze. Results show that the microphone was able to distinguish the onset of rotating stall accurately and promptly, even though – differently from dynamic pressure sensors - it does not provide sufficient information to determine the characteristics of the stall pattern. On this basis, the use of acoustic measurements could find room for automatic detection of rotating stall onset.

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

Volume 5: Turbo Expo 2002, Parts A and B ◽

10.1115/gt2002-30389 ◽

2002 ◽

Cited By ~ 10

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.

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

International Journal of Rotating Machinery ◽

10.1080/10236210490503950 ◽

2004 ◽

Vol 10 (6) ◽

pp. 433-442 ◽

Cited By ~ 1

Author(s):

Giovanni Ferrara ◽

Lorenzo Ferrari ◽

Leonardo Baldassarre

Keyword(s):

Centrifugal Compressor ◽

Experimental Analysis ◽

Rotating Stall ◽

Geometrical Parameters ◽

Vaneless Diffuser

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Rotating Stall Flow and Dangerous Blade Excitation of Centrifugal Compressor Impeller: Part 1 — Phenomenon of Large-Number Stall Cells

Volume 1: Turbomachinery ◽

10.1115/91-gt-102 ◽

1991 ◽

Cited By ~ 2

Author(s):

U. Seidel ◽

J. Chen ◽

U. Haupt ◽

H. Hasemann ◽

D. Jin ◽

...

Keyword(s):

Phase Analysis ◽

Centrifugal Compressor ◽

High Performance ◽

Fast Response ◽

Rotating Stall ◽

Blade Vibration ◽

Response Dynamic ◽

Compressor Impeller ◽

Stall Cells ◽

High Level

A new structure of rotating stall with unusual large-number stall cells (up to 7) has been detected experimentally in a high performance single stage centrifugal compressor system with backswept impeller and vaned diffusers. The number of stall cells is firstly identified by a phase analysis of pressure signals obtained from fast response dynamic transducers located at different circumferential positions on the shroud wall, and then verified by comparing the resulting frequencies of blade vibration with that measured from blade mounted strain gages. Up to 6 transducers in one radial position have been used for more certainty of the phase analysis. For the case of intermittent stall patterns, the frequency analysis of pressure and blade vibration signals is performed separately for sections with different characters of oscillation to avoid the smearing effect if signals of the whole pattern are averaged. As a result, the large-number stall cells, numbered 4–7, were determined in the speed range of 12000–14000 rpm, and in the higher speeds of 15000–16000 rpm right after the occurrence of normal stall cells of 2, when the flow rate is slightly reduced along the constant speed line. For the large-number stall cell case, the measured blade vibration strain has reached such a high level that is already beyond the tolerance of blade material. Moreover, frequencies of blade excitation are always in the vincinity of resonance. These two features, which are not observed for the normal stall cell case and for the excitation of broadband character, show a particular danger of this phenomenon to the compressor operation.

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Roles of vanes in diffuser on stability of centrifugal compressor

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1177/0954410019844433 ◽

2019 ◽

Vol 233 (14) ◽

pp. 5380-5392

Author(s):

Wangzhi Zou ◽

Xiao He ◽

Wenchao Zhang ◽

Zitian Niu ◽

Xinqian Zheng

Keyword(s):

High Pressure ◽

Centrifugal Compressor ◽

Dynamic Pressure ◽

Pressure Ratio ◽

Pressure Rise ◽

Rotating Stall ◽

Centrifugal Compressors ◽

Compression System ◽

The Stability ◽

Rotating Instability

The stability considerations of centrifugal compressors become increasingly severe with the high pressure ratios, especially in aero-engines. Diffuser is the major subcomponent of centrifugal compressor, and its performance greatly influences the stability of compressor. This paper experimentally investigates the roles of vanes in diffuser on component instability and compression system instability. High pressure ratio centrifugal compressors with and without vanes in diffuser are tested and analyzed. Rig tests are carried out to obtain the compressor performance map. Dynamic pressure measurements and relevant Fourier analysis are performed to identify complex instability phenomena in the time domain and frequency domain, including rotating instability, stall, and surge. For component instability, vanes in diffuser are capable of suppressing the emergence of rotating stall in the diffuser at full speeds, but barely affect the characteristics of rotating instability in the impeller at low and middle speeds. For compression system instability, it is shown that the use of vanes in diffuser can effectively postpone the occurrence of compression system surge at full speeds. According to the experimental results and the one-dimensional flow theory, vanes in diffuser turn the diffuser pressure rise slope more negative and thus improve the stability of compressor stage, which means lower surge mass flow rate.

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

Volume 2E: Turbomachinery ◽

10.1115/gt2020-14729 ◽

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.

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Stall Inception in a High Speed Centrifugal Compressor During Speed Transients

Volume 2C: Turbomachinery ◽

10.1115/gt2017-64499 ◽

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.

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

Volume 1: Advances in Aerospace Technology ◽

10.1115/imece2012-85397 ◽

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.

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An Investigation of Surge in a High-Speed Centrifugal Compressor Using Digital PIV

Journal of Turbomachinery ◽

10.1115/1.1343465 ◽

2000 ◽

Vol 123 (2) ◽

pp. 418-428 ◽

Cited By ~ 53

Author(s):

Mark P. Wernet ◽

Michelle M. Bright ◽

Gary J. Skoch

Keyword(s):

Flow Field ◽

Centrifugal Compressor ◽

High Speed ◽

Transient Flow ◽

Dynamic Pressure ◽

Rotating Stall ◽

Transient Pressure ◽

Pressure Transducers ◽

Stable Operating ◽

Particle Imaging

Compressor stall is a catastrophic breakdown of the flow in a compressor, which can lead to a loss of engine power, large pressure transients in the inlet/nacelle, and engine flameout. The implementation of active or passive strategies for controlling rotating stall and surge can significantly extend the stable operating range of a compressor without substantially sacrificing performance. It is crucial to identify the dynamic changes occurring in the flow field prior to rotating stall and surge in order to control these events successfully. Generally, pressure transducer measurements are made to capture the transient response of a compressor prior to rotating stall. In this investigation, Digital Particle Imaging Velocimetry (DPIV) is used in conjunction with dynamic pressure transducers to capture transient velocity and pressure measurements simultaneously in the nonstationary flow field during compressor surge. DPIV is an instantaneous, planar measurement technique that is ideally suited for studying transient flow phenomena in high-speed turbomachinery and has been used previously to map the stable operating point flow field in the diffuser of a high-speed centrifugal compressor. Through the acquisition of both DPIV images and transient pressure data, the time evolution of the unsteady flow during surge is revealed.

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