Numerical Investigation of the Impact of Intake Pipelines on the Performance and Flow Characteristics of a Centrifugal Compressor

Due to the installation space constraints in practical applications, centrifugal compressors often utilize bent intake pipes. Quantifying the correlation between the centrifugal compressor’s operating performance and the flow dynamics within curved inlet tubes is essential. In this research, the accuracy of the numerical methodology was validated using the experimental outcomes. Subsequently, the centrifugal compressor’s performance was simulated for two intake curved ducts, i.e., Pc with a coplanar central axis and Pnc with a non-coplanar central axis, followed by the analysis of the flow characteristics for each intake configuration. The results indicated that Pc produced a symmetrical swirling flow field at the outlet, which was characterized by a lower plane superimposed distortion intensity (PSDI), while Pnc generated an asymmetrical offset swirling flow field with a higher PSDI. The PSDI increased with the flow rate, reaching maximum values of 0.137 for Pc and 0.386 for Pnc. Compared to the inlet straight tube, the performances of the centrifugal compressor connected to Pc and Pnc both decreased, while Pnc exhibited a more significant performance deterioration degree. Under high-speed conditions, the maximum degradation degrees of pressure ratio for Pc and Pnc reached approximately 5.7% and 9.8%, respectively, while the efficiency reduction degree reached approximately 5.3% and 8.7%, respectively. The performance reduction degree for both bent pipes increased with the rising PSDI, exhibiting an exponential correlation. The flow characteristics of the intake pipelines affected the flow behavior within the impeller, with the flow field variation locations closely resembling the distorted regions of the bent pipes.