EFFECT OF AREA RATIO AND CASING ANGLE ON THE PERFORMANCE OF AXIAL ANNULAR DIFFUSER

Abstract

A diffuser is a device for converting the kinetic energy of an incoming fluid into pressure. As the flow proceeds through the diffuser there is continuous retardation of the flow resulting in conversion of kinetic energy into pressure energy. Diffuser forms an important part in flow machinery and structures. The present study involves the CFD analysis of effect of area ratio and varying casing angle on axial annular diffuser performance using fluent and also the prediction of flow characteristics using various mathematical models. The axial annular diffuser considered in the present case has the hub angle keeping constant as 0° and casings are diverging with 6° and 8° angles. The geometries of the diffusers are calculated for different area ratio i.e. 2, 3, 4 and varying casing angle 6°, 8°. Swirl angle of 0°, 7.5°, 12°, 17°, 25° are introduced to predict the reversal of flow and separation of flow from the wall and to visualize the effect of area ratio, casing angle and inlet swirl. The variation in parameter i.e. longitudinal velocity, Swirl Velocity and Pressure Co-efficient along the various sections and flow patterns have been studying. In the present study RNG turbulence models are studied.