CFD ANALYSIS OF FLUID FLOW THROUGH EQUIANGULAR ANNULAR DIFFUSER

Abstract

Diffuser is the important feature of turbomachinery, which is used for the efficient conversion of kinetic energy into pressure energy. Among the various types of diffusers, least attention has been given to annular diffusers because of the number of geometric parameters that needed to be considered. The geometric limitations in aircraft applications where the diffusers need to be specially designed so as to achieve maximum pressure recovery within the shortest possible length led to the development of annular diffusers.

In the present study, the performance of a series of equiangular annular diffusers of various area ratio (2, 3, 4, and 5), lengths and divergence angle (10º, 15º, 20º and 25º) are determined with the help of FLOTRAN. The flow conditions at entrance are varied to evaluate how they affect the flow development in the passage. The value of Reynolds No at inlet is varied from 2.58×105 to 7.73×105. The result are present in the form of velocity diagram; pressure diagram; vector plot of velocity; static pressure distributaries and static pressure recovery coefficient along hub and casing wall; variation of Mach No at exit section of diffuser. The result indicates that pressure recovery increases with increases in area ratio. But pressure recovery is almost independent of Reynolds No. There was no separation on casing wall upto angle of 25º. The variation of Mach No is 0.15 to 0.46. In this range of Mach No, there is small change in pressure recovery upto cone angle of 15º. With further increases in angle, it reduces at somewhat higher rate.