Influence of the volute on the flow in a centrifugal compressor of a high-pressure ratio turbocharger

Abstract

The asymmetric influence of the volute on the flow in a transonic, high-pressure ratio centrifugal compressor at off-design conditions was investigated. Fully three-dimensional viscous steady-state computational fluid dynamics (CFD) was applied to simulate the flow in a 4.2:1 design pressure ratio compressor for automotive application. Computed performance characteristics are presented for low- and high-pressure ratio operating conditions, with and without an overhung volute. The volute was found to severely harm aerodynamic stability of the investigated compressor when operating at lower than design mass flow. The relative narrowing effect of the volute on compressor map width increases with pressure ratio up to a 42 per cent drop in stable flow range at design speed. The inter-passage variations in performance quantities and the influence of the volute tongue region are discussed in detail. The circumferential variations of incidence angle correlate with rotational speed, which, in combination with the higher sensitivity to incidence angle at transonic inflow conditions, seems to deteriorates stability when transonic inflow conditions are reached.