Industrial centrifugal compressors for oil and gas industry are operated under high gas pressure conditions and are used in wide operation range. An accurate prediction of rotating stall and destabilizing aerodynamic force is one of the key technologies for those compressors, because rotating stall inception sometimes causes severe non-synchronous shaft vibration problems and limits its operation range. Thus the aim of this study is to establish an accurate method to predict the inception of rotating stall accurately and its effect for shaft vibration. To achieve this, numerical investigations are carried out using unsteady Reynolds Averaged Navier Stokes (RANS) simulation with a full annulus model of the compressor stage. Also, to assess the accuracy of the simulation qualitatively and quantitatively, a high pressure compressor test-rig which contains a shrouded impeller and a vaneless diffuser is built. To confirm the effect of shaft vibration associated with rotating stall, an experiment is carried out with relatively high gas pressure conditions as the inlet pressure level is over 30 barA.

In the first part of the study, prediction accuracy of compressor performance is studied by steady Computational Fluid Dynamics (CFD) simulation. And it is found that by taking the wall roughness effect into account, predicted performance shows good agreement with the experiment. Thus the following rotating stall study is also carried out by considering its effect.

In the second part of the study, prediction accuracy of rotating stall is studied. In the experiment, two types of rotating stall are measured. One is multiple cell stall whose rotation speed is relatively low induced in the vaneless diffuser and the other is one cell stall induced in the impeller region with high rotation speed. The properties of multiple cell stall agree with the previous experimental and numerical studies and it has the limited effect for shaft vibration. Conversely, the one cell stall shows severe non synchronous vibration. In this study both types of stall prediction are examined by unsteady CFD simulation. It is found that simulation can predict the inception of them with relatively high accuracy as the predicted results show good agreement with the experiments in terms of cell count, rotation speed, pressure fluctuation level and its effect for the shaft vibration.

Through this study, an effectiveness of unsteady CFD is confirmed for this kind of stall prediction. Even the RANS simulation with relatively coarse computational grid can predict the rotating stall inception and its effect for shaft vibration well.


Numerical and Experimental Study on Rotating Stall in Industrial Centrifugal Compressor

Division / Sponsor:
International Gas Turbine Institute (IGTI)

Paper Proceedings: https://asmedigitalcollection.asme.org/GT/GT2020/volume/84058

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