Numerical Investigation of Turning Diffuser Performance by Varying Geometric and Operating Parameters

Abstract

This paper presents a numerical investigation of pressure recovery and flow uniformity in turning diffusers with 90 o angle of turn by varying geometric and operating parameters. The geometric and operating parameters considered in this study are area ratio (AR= 1.6, 2.0 and 3.0) and inflow Reynolds number (Re in =23, 2.653E+04, 7.959E+04, 1.592E+05 and 2.123E+05). Three turbulence models, i.e. the standard k-e turbulence model (std k-e), the shear stress transport model (SST-k-W) and the Reynolds stress model (RSM) were assessed in terms of their applicability to simulate the actual cases. The standard k-e turbulence model appeared as the best validated model, with the percentage of deviation to the experimental being the least recorded. Results show that the outlet pressure recovery of a turning diffuser at specified Re in improves approximately 32% by varying the AR from 1.6 to 3.0. Whereas, by varying the Re in from 2.653E+04 to 2.123E+05, the outlet pressure recovery at specified AR turning diffuser improves of approximately 24%. The flow uniformity is considerably distorted with the increase of AR and Re in . Therefore, there should be a compromise between achieving the maximum pressure recovery and the maximum possible flow uniformity. The present work proposes the turning diffuser with AR=1.6 operated at Re in =2.653E+04 as the optimum set of parameters, producing pressure recovery of C p =0.320 and flow uniformity of su=1.62, with minimal flow separation occurring in the system.