Centrifugal compressor has widespread applications in areas such as aerospace, automotive, power and process industries and hence the prediction of its performance is crucial at the design stage. Traditional design, build and test are accelerated through numerical simulation as a virtual test bed for compressor development. In this work, a CFD methodology has been developed to predict the performance of a centrifugal compressor with its surge and choke limits. The transient, compressible flow in a moving domain with body-fitted unstructured mesh is solved in Simerics-MP. The distributed parallel solver of Simerics-MP enables to perform the complete performance map of a centrifugal compressor in a day.
The phenomena of surge and choke in a centrifugal compressor is of paramount importance as it determines the limiting points of operation for a particular speed of the compressor. Surge occurs at low flow rates, and it is characterized by instabilities causing undesirable noises that lead to drop in the operational efficiency. It can also result in wear and tear of the impeller blades. Whereas choke occurs at high flow rates with no further increase in pressure and it is accompanied by aberrant vibrations. The CFD simulation predicts the instabilities occurring at surge such as pressure oscillations and flow reversal accurately, which is used as a criterion for the prediction of surge point. The choke phenomenon is characterized by fluid attaining sonic velocity in the impeller or diffuser region of the compressor. The CFD predicted results showed a fair comparison with the experimental results of pressure ratio, power, and efficiency at different speeds.