Experimental Investigation of Flow Parameters in a Mild Curved S-shaped Diffusing Duct

Abstract

The paper presents a detailed study of the performance of fully developed subsonic turbulent flow in a circular cross-section S-shaped centerline-diffusing duct. A precalibrated 5-hole pressure probe was used for the measurements. The diffuser cross-section was expanded to 2.25 area ratio (Ar) at the exit. The duct was fabricated by joining two 22.5º bends of curvature ratio (βt) 11.46 in reverse direction with a centerline offset of 0.2 of the axial length of the diffuser. The test was carried out with inlet Re=8.4x105, calculated based on diffuser inlet diameter. The experimental results indicated the generation of secondary flow in the form of a pair of counter rotating vortices in the first half, which changes its senses of rotation in the second half. The overall static pressure recovery of the diffuser was 40%.