Role of Tip Leakage in Stall of a Transonic Centrifugal Impeller

Abstract

The objective of the current paper is to employ numerical simulations to identify flow features, which could lead to the breakdown of stable operation in transonic centrifugal impellers at near-stall operating conditions. Steady state three-dimensional viscous flow calculations are used to investigate the flow inside a transonic impeller representative of state of the art automotive turbocharger technology. The detailed impeller flow field is compared at different operating conditions. It is observed that the interaction of the relative total pressure deficit coming from the main blade tip region and the adverse pressure gradient in the splitter passage results in a breakdown of the flow in the tip region. These low relative total pressure fluids originate from the main blade tip leakage flow and/or the transported boundary layers. Effects due to the splitter wall shear stress and the turbulence model on the flow are also investigated and addressed in the paper.