Experimental Study of Rotating Stall in Vaneless Diffuser of a Centrifugal Compressor

2013 ◽  
Author(s):  
S. Ohuchida ◽  
T. Kawakubo ◽  
H. Tamaki
Keyword(s):  
Flow Structure ◽  
Centrifugal Compressor ◽  
Phase Locking ◽  
Rotating Stall ◽  
Propagation Mechanism ◽  
Vaneless Diffuser ◽  
Cross Sectional ◽  
Present Measurement ◽  
Separation Pattern ◽  
Sectional Measurement

In this study, with a focus on the rotating stall phenomenon in the vaneless diffuser of a centrifugal compressor, 2D-PIV is conducted to better understand the flow structure. Although many studies have reported concerning this problem, most data is obtained through experiments under lower speed conditions, using a simplified model or equipment. Unlike such studies, a ship board turbocharger compressor with a higher impeller rotation speed is selected as an application for the present measurement. In the measurement, an ensemble-averaged phase locking technique is also selected to compensate for the lack of time resolution of the PIV system. Since rotating stall in vaneless diffuser results in a huge amplitude of pressure fluctuation, the trigger signal for the ensemble-averaged measurement was constructed from diffuser wall pressure. The equipment layout for PIV is set to a cross sectional measurement of constant span height in the diffuser passage. PIV is conducted through a sight glass mounted on the diffuser shroud wall, the field of view of which is limited by its size. To obtain the whole flow structure of the diffuser passage, the measurement is repeated for different cyclic phases of the phenomenon. Five different span heights ranging from diffuser hub to shroud were selected as velocity measurement planes. The result obtained at the mid span indicates a typical pattern of the flow field containing containing low and high-velocity regions mutually in a circumferential direction. Considering other results obtained at different span heights, the whole flow structure is visualized and utilizing this data, both a wall separation pattern and a stall propagation mechanism are considered.

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.

Stress Tensor Measurements within the Vaneless Diffuser of a Centrifugal Compressor

1989 ◽  
Vol 203 (1) ◽  
pp. 51-59 ◽  
Author(s):  
T M A Maksoud ◽  
M W Johnson
Keyword(s):  
Centrifugal Compressor ◽  
Sampling Technique ◽  
Phase Lock Loop ◽  
Tangential Component ◽  
Secondary Flows ◽  
Axial Component ◽  
Reynolds Stresses ◽  
Vaneless Diffuser ◽  
Cross Sectional ◽  
Impeller Outlet

Distributions of normal and shear (Reynolds) stresses inside the vaneless diffuser of a low-speed centrifugal compressor are presented. The measurements were made using a triple hot-wire system and a phase lock loop sampling technique. Results were obtained on cross-sectional planes at eight radial stations between the impeller outlet and the diffuser exit at three different flowrates. The turbulence was highly anisotropic and became more so as the flowrate was increased. The tangential component of turbulent intensity was found to be significantly smaller than either the radial or axial component. The blade wake observed at the diffuser inlet decays very rapidly due to the strong tangential Reynolds stresses generated by the opposed secondary flows on either side of the wake. The passage wake decays very much more slowly and is still identifiable at the diffuser discharge.

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

Non-Axisymmetric Flow Structure in Vaneless Diffuser of Centrifugal Compressor for Turbochargers

2012 ◽  
Author(s):  
Chuanjie Lan ◽  
Xinqian Zheng ◽  
Hideaki Tamaki
Keyword(s):  
Flow Field ◽  
Flow Structure ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Internal Combustion Engines ◽  
Combustion Engines ◽  
Vaneless Diffuser ◽  
Asymmetric Flow ◽  
Oil Flow ◽  
Flow Visualizations

Turbocharger technology is widely used in internal combustion engines. With the downsizing of internal combustion engines and the introduction of strict emission regulations, there is urgent demand for turbochargers featuring centrifugal compressors with a wide flow range. The flow in a centrifugal compressor of a turbocharger is non-axisymmetric due to the inherent asymmetry of the discharge volute. The asymmetric flow field inside the diffuser has great influence on the performance of centrifugal compressor. In order to develop a flow control method that facilitates a wider flow range of turbocharger compressors, further understanding of the asymmetric flow structure is very important. The main subject of this study is to reveal the asymmetrical characteristics of the flow field in the vaneless diffuser of a centrifugal compressor followed by a volute. Oil flow visualizations and numerical simulations were used. The results of the numerical simulations are consistent with that of the oil flow visualizations near choke and at designed flow rate. The results show that a “dual-zone mode” asymmetric flow structure exists near the shroud of the vaneless diffuser at near choke condition. A bifurcation point at the volute tongue that divides the flow and creates two distinct flow patterns was found. The asymmetry of the flow structure near the hub was much less significant than that near the shroud. At the design flow rate, asymmetric flow patterns are found neither near shroud nor near hub. At near surge condition, the pattern of the oil flow traces near the shroud is very different from those near choke.

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.

Unsteady Flow Within Centrifugal Compressor Channels Under Rotating Stall and Surge

1992 ◽  
Vol 114 (2) ◽  
pp. 312-320 ◽  
Author(s):  
S. Mizuki ◽  
Y. Oosawa
Keyword(s):  
Unsteady Flow ◽  
Flow Rate ◽  
Centrifugal Compressor ◽  
Rotating Stall ◽  
Experimental Results ◽  
Vaneless Diffuser ◽  
Lumped Parameter ◽  
Lumped Parameters ◽  
Parameter Theory ◽  
Unsteady Behavior

Unsteady flow patterns throughout a centrifugal compressor system during the rotating stall and the surge were measured experimentally. Various kinds of unsteady behavior of the flow appeared both continuously and suddenly as the flow rate decreased. The part-span stall, the full-span stall, the mild and deep stalls, and the deep surge appeared clearly. The fluctuations caused by the full-span stall were seen even during surge and affected the flow within the scroll through the vaneless diffuser. The experimental results were compared with those computed by the lumped parameter theory. Good agreements between them were obtained when appropriate values were selected for the lumped parameters.

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