Centrifugal Stage Performance Prediction And Validation For High Mach Number Applications

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Kowalski, Steven C.; Pacheco, Jorge E.; Fakhri, Syed; Sorokes, James M.
Texas A&M University. Turbomachinery Laboratories
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Centrifugal compressors used for process applications like Liquefied Natural Gas (LNG) plants require operation at high machine Mach numbers (>1) due to the heavy gas and reduced footprint requirements. Performance guarantees are commonly specified as per API-617, but some end users are requiring tighter performance tolerances. This paper describes Computational Fluid Dynamics (CFD) performance predictions and their validation using test rig results. The experimental results presented in this paper were obtained using a heavily instrumented compressor test rig. The instrumentation used allows measurement of necessary stage performance parameters such as total and static pressure, total temperature and flow angle among others. Due to the target tolerances, CFD was used to predict the performance rather than alternative methods (mean-line codes, 2D prediction codes, etc.). The results of the CFD analyses are described in the paper, including flow field characteristics and performance parameters. The performance results from the tested stages matched well with the CFD prediction. The performance predicted using CFD was also well within API-617 tolerances. The comparison using the tighter end user tolerances showed that CFD predictions can meet the requirements for efficiency, head and overload margin. There is still more work to be done to meet the tighter tolerances regarding surge/stall margin. Overall, CFD analysis has been shown to have the necessary accuracy to predict performance within tight tolerances for challenging applications such as high machine Mach number.