STUDY OF FLOW CHARACTERISTICS THROUGH ANNULAR DIFFUSERS

Abstract

This thesis deals with the experimental investigation of air flow through annular diffusers. This investigation is mainly concerned with the aerodynamic characteristics of the annular diffuser. Other aim of this investigation is to study the internal performance of the annular diffuser in terms of the boundary layer growth. Therefore, velocity profiles and radial static pressure distributions are measured in the presence of struts with different cross-sections. All the tested diffusers used in the present study have the same hub and casing radii at the inlet. Three straight walled annular diffusers were made with a constant half cone angle for the outer wall of 10 degrees, and half cone angle of 0, 5, and 10 degrees for the hub. All the measurements in the present experimental program were made in the incompressible flow regime at an average Reynolds number ranging from 1.3*105 to 2.71*105• The experimental program consists of two parts. The first part considers naturally developed inlet conditions, and the second part examines the influence of inlet turbulence intensity, using wall spoiler at the inlet of the annular diffuser. The objective of the present work is to obtain the effects of strut geometry and hub half cone angle on the performance of annular diffuser. The influence of increasing the level of inlet turbulence caused by flow spoilers of different thicknesses was also studied. The variation of the performance and flow characteristics within the annular diffusers would be expected to result from con•esponding changes in any or all of the inlet flow parameters, in addition to geometric parameters. The principal parameters are: a- The inlet flow blockage. b- The inlet turbulence intensity. c- The inlet velocity distortion. d- The diffuser cant angle.