Experimental Investigation of Rotating Instabilities in a Two-Stage Centrifugal Compressor With Vaneless Diffuser

Mapping Intimacies ◽

10.1115/imece2001/fed-24938 ◽

2001 ◽

Author(s):

Vladimir V. Golubev

Keyword(s):

Experimental Investigation ◽

Centrifugal Compressor ◽

Pressure Fluctuations ◽

Rotating Stall ◽

Sensitive Area ◽

Flow Conditions ◽

Vaneless Diffuser ◽

Unstable Flow ◽

Two Stage ◽

Multi Stage

Abstract This paper examines unsteady response of an experimental two-stage centrifugal compressor with vaneless diffusers. A thorough investigation of pressure fluctuations along the compressor channel is carried out in order to examine the onset of unstable flow conditions. Rotating stall structures are localized, with special attention paid to identifying the most sensitive area of the multi-stage compressor channel which may serve as a precursor to unstable compressor operation. It is shown that both stages may develop rotating stall structures simultaneously, however the 2nd stage tends to destabilize first and reveals higher magnitudes of the unsteady response.

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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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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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Multistage Centrifugal Compressor Surge Analysis: Part I — Experimental Investigation

Volume 3: Coal, Biomass and Alternative Fuels; Combustion and Fuels; Oil and Gas Applications; Cycle Innovations ◽

10.1115/98-gt-068 ◽

1998 ◽

Author(s):

G. L. Arnulfi ◽

P. Giannattasio ◽

C. Giusto ◽

A. F. Massardo ◽

D. Micheli ◽

...

Keyword(s):

Experimental Investigation ◽

Centrifugal Compressor ◽

Reference Data ◽

Dynamic Control ◽

Rotating Stall ◽

Operating Conditions ◽

Multi Stage ◽

Compressor Surge ◽

Multistage Centrifugal Compressor ◽

Insight Into

This paper reports an experimental investigation on centrifugal compressor surge. The compression system consists of a four-stage blower with vaned diffusers and a large plenum discharging into the atmosphere through a throttle valve. Measurements of unsteady pressure and flow rate in the plant, and of instantaneous velocity in the diffusers of the first and fourth compressor stage are performed during deep surge, at several valve settings and three different rotation speeds. Additional tests have been carried out on a different system configuration, i.e., without plenum, in order to obtain the steady-state compressor characteristics and to collect reference data on stall in surge-free conditions. In this configuration, a fully developed rotating stall was detected in the compressor diffusers, while during surge it affects only a limited part of the surge cycle. The goal of the present experimental work was to get a deeper insight into unstable operating conditions of multi-stage centrifugal compressors and to validate a theoretical model of the system instability to be used for the design of dynamic control systems.

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Investigation of the instability mechanisms in a turbocharger centrifugal compressor with a vaneless diffuser by means of unsteady simulations

Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering ◽

10.1177/0954407016677435 ◽

2016 ◽

Vol 231 (11) ◽

pp. 1558-1567 ◽

Cited By ~ 6

Author(s):

Xinqian Zheng ◽

Anxiong Liu ◽

Zhenzhong Sun

Keyword(s):

Flow Field ◽

Centrifugal Compressor ◽

High Speed ◽

Simulation Method ◽

Great Accuracy ◽

Rotating Stall ◽

Tip Clearance ◽

Vaneless Diffuser ◽

Unstable Flow ◽

Low Velocity

The stable-flow range of a compressor is predominantly limited by surge and stall. In this paper, an unsteady simulation method was employed to investigate the instability mechanisms of a high-speed turbocharger centrifugal compressor with a vaneless diffuser. In comparison with the variation in the pressure obtained by dynamic experiments on the same compressor, unsteady simulations show a great accuracy in representing the stall behaviour. The predicted frequency of the rotating stall is 22.5% of the rotor frequency, which agrees with to the value for the high-frequency short-term rotating stall obtained experimentally. By investigating the instability of the flow field, it is found that the unstable flow of the turbocharger compressor at high rotational speeds is caused by the tip clearance leakage flow and the ‘backflow vortices’ originating from the interaction of the incoming flow and the backflow in the tip region of the passages. The asymmetric volute helps to induce the occurrence of stall in certain impeller passages because it generates an asymmetric flow field. The high-pressure low-velocity area from the 180° circumferential position to the 270° circumferential position is dominant and strengthens the backflow at the trailing edge of the impeller, finally triggering the stall.

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

Volume 6: Turbo Expo 2003, Parts A and B ◽

10.1115/gt2003-38394 ◽

2003 ◽

Cited By ~ 9

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.

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Distinction Between Different Types of Impeller and Diffuser Rotating Stall in a Centrifugal Compressor With Vaneless Diffuser

Journal of Engineering for Gas Turbines and Power ◽

10.1115/1.3239589 ◽

1984 ◽

Vol 106 (2) ◽

pp. 468-474 ◽

Cited By ~ 57

Author(s):

P. Frigne ◽

R. Van Den Braembussche

Keyword(s):

Experimental Data ◽

Experimental Investigation ◽

Centrifugal Compressor ◽

Rotating Stall ◽

Rotating Flow ◽

Hot Wire ◽

Vaneless Diffuser ◽

Velocity Fluctuations ◽

Different Types ◽

Induced Velocity

This paper describes the results of an experimental investigation of the sub-synchronous rotating flow patterns in a centrifugal compressor with vaneless diffuser. Several compressor configurations have been examined by means of hot wire anemometry, Fourier analysis allowed one to distinguish between the different modes of unstable operation. For both impeller and diffuser rotating stall, comparison is made between the amplitude, frequency, and periodicity of the induced velocity fluctuations. The results are further cross-checked with other experimental data.

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Numerical Simulation of Surge in Turbocharger Centrifugal Compressor: Influences of Downstream Plenum

Volume 7: Turbomachinery, Parts A, B, and C ◽

10.1115/gt2011-45163 ◽

2011 ◽

Cited By ~ 1

Author(s):

Strong Guo ◽

Hua Chen ◽

Xiaocheng Zhu ◽

Zhaohui Du

Keyword(s):

Numerical Simulation ◽

Flow Field ◽

Mass Flow ◽

Centrifugal Compressor ◽

Stokes Equations ◽

Numerical Technique ◽

Pressure Ratio ◽

Rotating Stall ◽

Vaneless Diffuser ◽

Unstable Flow

Surge is an important instability seriously affecting compression systems. This paper presents a numerical simulation of surge flow phenomenon inside a turbocharger centrifugal compressor with a vaneless diffuser. The compressor was discharged into a plenum and the effect of the plenum on surge behavior of the compressor system was investigated. The entire geometry of the compressor, including the impeller, vaneless diffuser, volute housing and downstream plenum, were included in the simulation. Three-dimensional Reynolds averaged compressible Navier–Stokes equations were solved with the k–ε turbulence model using commercial software CFX and two different sizes of plenum were studied. A new plenum model is proposed which allows temporal variation of temperature inside the plenum. The numerical technique employed to set up CFD (computational fluid dynamics) with such an unstable flow system are described. The results show that when the plenum volume was nearly doubled, the dominating frequency of the system suddenly dropped from 72Hz to 23Hz. During the surge cycle, the compressor characteristic (pressure ratio ν mass flow curve) showed distinct differences. With the smaller plenum, the characteristic showed random traces with little global backflow at the compressor inlet, while with the larger plenum, clear surge cycles are displayed with strong global backflow at the inlet. The flow fields of the two systems are presented as functions of time and show distinct differences. In the case of the smaller plenum, the circumferential flow field inside the impeller is non uniform, showing influences of rotating stall, while in the case of the large plenum, the circumferential uniformity returns and the flow field behaves quasi-steadily during the surge cycle. With the larger plenum, the volute flow synchronises with the inlet mass flow oscillation in time and a completed vortex break down occurs at every volute cross section, but with the smaller plenum the synchronisation disappears and vortex break down only occurs partially at the centers of some volute cross sections.

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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 ◽

10.1155/s1023621x04000430 ◽

2004 ◽

Vol 10 (6) ◽

pp. 433-442 ◽

Cited By ~ 22

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.

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