Inlet bent torsional pipe effect on the performance and stability of a centrifugal compressor with volute

Inlet bent torsional (BT) pipes are applied to complex turbocharger systems and industrial centrifugal compressors owing to space and weight constraints. To determine the interaction mechanism between the inlet BT pipe and outlet volute, and its effect on the centrifugal compressor performance and stability, three compressor models (model with clean inlet (M0 model) and models with distorted inlets induced by BT pipes (M1 and M2 models)) were chosen to conduct a performance experiment and static pressure measurement of the casing wall. The results show that the M1 and M2 cause a 6.4% increment and 22% reduction in the stable operating range, respectively. At the near-choke and peak efficiency points, both M1 and M2 can change the casing static pressure distribution evidently and thus influence the compressor pressure ratio and efficiency significantly. At the near-stall point, the high static pressure at the inlet region induced by the BT pipe of M1 can weaken the pressure peak strip induced by the volute. Therefore, both the considerable increase in circumferential pressure uniformity and the positive pre-whirl distortion of M1 are responsible for the delay of compressor stall. Finally, the interaction relationship of the inlet/outlet distortions in the entire operating range was sketched.