Effect of Swirl on the Performance of an Annular Diffuser

Abstract

Annular diffusers are primarily used to convert the kinetic energy of the exhaust flow into pressure energy. The performance of the diffusers are often measured using pressure recovery maps, that generally do not consider the distortion of flow at the inlet due to other upstream machine components. A high swirl velocity at the inlet could often account for large energy losses and hence it is necessary to curb the swirl component by appropriate design considerations. In this present work,it is desired to establish the swirl number range at the inlet of an annular diffuser for its effective and efficient performance and increased pressure recovery of the diffuser. “Swirl effect” on the fluid flow parameters with and without struts is compared, to give the idea of the numerical variation in the parameters.Computational fluid dynamics (CFD) analysis was performed to determine the maximum pressure recovery based on variations in the inlet swirl number. Thus, the flow was studied under varied conditions and a relation between the input parameters and the general pattern of flow for the specified input conditions was critically examined.