DES analysis on effects of variable geometry inlet orifice on a centrifugal compressor

A variable geometry inlet configuration can improve the off-design aerodynamic performance of a turbocharger compressor by actively modulating the internal flow field. As the core part of the configuration, the variable geometry orifice is arranged in front of the compressor inducer. Its novelty is to actively regulate the compressor inlet flow area at an off-design point without causing significant impact at the design point. In this paper, the effects of the orifice on compressor performance and internal flow field are investigated using experiments and numerical simulations. The experimental and the numerical results confirm the variable inlet configuration to be a promising method for extending the compressor operation range. The DES calculations reveal incidence angle reduction at inducer inlet, shock wave migration to a lower radius from blade tip, formation of the aft-loaded impeller, reduced difference between jet and wake flows at impeller exit, and turbulent flow enhancement in the diffuser. Based on understanding the orifice's effects on the centrifugal compressor, a design suggestion is proposed for the variable geometry compressor of this sort.