Flow characteristics of s-shaped circular and rectangular diffusers

S-shaped diffusers fall under category of curved diffusers and commonly used as the intake ducts of the engines in the aircraft. Detailed investigations on these diffusers, if any have been conducted by leading R & D organizations, are confidential in nature and very few are reported in open literature. The flow and performance characteristics of these diffusers are very complicated because of the combined effect of geometrical curvature and flow diffusion. Though these diffusers have lower performance when compared with straight diffusers, they have a distinct advantage over the straight diffusers due to flexibility in the geometry in making it compatible with the space constraint. Based on the intensive literature review, it is observed that detailed investigations are needed to understand the flow and performance characteristics of S-shaped diffusers. The whole investigation program presented in the given work was carried out in two phases: first, experimental investigation and second, computational investigation. Further, the experimental investigation was divided into two parts: first, analysis on S-shaped rectangular diffuser and second analysis on S-shaped circular diffuser. For experimental investigation on rectangular diffuser, the test rig used by Majumdar [1994] has been adopted and modified to suit the present requirement. The experimental set-up consists of a single-stage centrifugal blower capable of delivering 0.6 m3/sec air at a gauge pressure of 500 mm of water column, settling chamber, diverging cone and contraction cone. The blower is directly coupled with an electric motor (5.5 kW and 2850 RPM) and its exit