A comparative study of incompressible and compressible design approaches of radial inflow turbine volutes

Abstract

The one-dimensional design approaches of radial inflow turbine volutes can be catalogued into incompressible and compressible. This paper investigates the degree to which they differ from each other in terms of design parameters, such as the distribution of ratio of area to radius A/r and radius r, and in terms of flow deviation from the free vortex pattern. Theoretical analysis proves that the incompressible approaches failed to provide free vortex and uniform flow for the wheel in compressible flow regimes. A numerical simulation on a previously designed and tested volute shows that the wake flow of the tongue and the boundary layer on the wall cause the tangential velocity of the volute flow to deflect from the free vortex design downstream and upsteam respectively of the tongue. The radial velocity component is higher at first, then lower than the free vortex design, owing to the significant pressure gradient around the tongue.