Effect of swirl on the flow characteristics of S-shaped diffusing duct

Abstract

The flow and performance characteristics of a S-shaped diffusing duct having an area ratio of 1.9, length of 300 mm and turning angle of 22.5º/22.5º have been experimentally investigated to establish the effect of swirl. The static pressure, total pressure, velocity and turbulence intensity are measured using a calibrated five-hole probe and constant-temperature hot-wire probe. The performance parameters are evaluated based on the mass-averaged quantities. A significant improvement in the pressure recovery coefficient is observed for swirl flow from 0.36 to 0.54. The improvement is observed for both, clockwise and anti-clockwise swirl, the improvement being higher for clockwise swirl. Flow uniformity at the exit is more uniform for clockwise swirl at the inlet.