Numerical assessment of a very high pressure ratio centrifugal impeller

Abstract

Abstract The paper focuses on studying the influence of mesh size, numerical discretization schemes and different turbulence models on radial impeller performances. The chosen impeller is a 14:1 pressure ratio novel design for use in the TIDE pulse detonation engine architecture. In preparation for the experimental research, numerical studies were performed for five steady-state analysis and one unsteady, single passage with a fully structured solver. A grid sensitivity study was conducted over four grid resolutions, starting from a coarse to dense mesh (0.7 mil, 1.5 mil, 5 mil and 9 mil), in order to determine the influence of mesh points, numerical stability and reduce interpolation errors. Another problem in a CFD study is the selection of a proper turbulence model, thus six RANS models were investigated: k-ε, v2-f, k-ω Shear Stress Transport (both steady and unsteady), Spalart – Allmaras and an Explicit Algebraic Reynolds Stress Model. Results show that global parameters such as pressure ratio and efficiency predictions remain unchanged above 1.5 mil cells/passage, while above 5 mil cells/passage, RANS models become unstable and lead to poor convergence. The most conservative model proved to be the SST with minimalistic values for both pressure ratio and isentropic efficiency.