Experimental Validation of Numerically Optimized Short Annular Diffusers

Abstract

Short annular diffusers with negative wall angles were evaluated numerically and experimentally with up to 40 deg inlet swirl at an inlet Reynolds number of Ret ≈ 1.4 أ— 105 and Mach number of Mt ≈ 0.16. The 80% experimental effectiveness of the 1.61 and 1.91 area ratio (AR) diffusers with 0–20 deg inlet swirl were on par with unswirled maximums reported in literature and computational fluid dynamics (CFD) predicted reasonable outlet axial velocity profiles and wall pressure distributions. The AR = 2.73 diffuser's effectiveness without swirl was 13% below the maximum for the given AR and larger discrepancies occurred in the CFD results due to the incorrect prediction of the recirculation zone strength. Preference was given to the realizable k–خµ model on coarse grids with wall functions that predicted performance of all cases with at least 20 deg inlet swirl to within 20%.