The Design and Performance of Axially Symmetrical Contoured Wall Diffusers Employing Suction Boundary Layer Control

This paper presents a procedure for the design and the performance prediction of axially symmetrical contoured wall diffusers employing suction boundary layer control. An inverse problem approach was used in the potential flow design of the diffuser wall contours. Three short (L/l ≤ 5.15), high area ratio (2.5 and 3) diffusers were tested in the study and were found to have effectiveness values in excess of 90 percent (comparable straight wall diffusers have effectiveness <40 percent) while requiring suction flows of less than 10 percent of the inlet flow. The experimentally observed flow characteristics, the stability of flows within the diffusers, are also described. Because of their high effectiveness and short length these diffusers appear to be ideally suited for use as gas turbine combustor diffusers and as turbine discharge diffusers.