Flow Field Numerical Research in a Low-Pressure Centrifugal Compressor with Vaneless Diffuser

Abstract

This work demonstrates the results of the first phase of the problem that is aimed at the numerical investigation of such unsteady effects as the precursor stall and the rotating stall in the stage with a vaneless diffuser of a centrifugal compressor. This paper is focused on the capabilities and constraints of the steady-state numerical simulations for an accurate prediction of the flow through the compressor stage. Numerical simulations were carried out in NUMECA FINE/TURBO 8.9.1 for a single blade passage. The results were validated through a comparison with the experimental data at the diffuser inlet and outlet. The results of numerical simulations using different discretization schemes and turbulence models predicted different flow structure. The results obtained with the second order discretization agree with the experiments for the steady-state case in the region of high flows rates. In the area of low flow rates the unsteady effects significantly influence the flow leading to poor predictions. An analysis of an influence of the geometry model and the grid resolution on the convergence is required to predict the satisfactory agreement with experiment.