ABSTRACT
Gas-turbine exhaust diffusers play an important role in turbine power output by increasing the pressure ratio across the last stage of the turbine by making the turbine exit static pressure subambient. The main aerodynamic design goal of an exhaust diffuser is to obtain maximum recovery in static pressure given the various design constraints of intervening struts for bearing support and service lines and the duct length available for flow diffusion, in addition to the design-to-cost objective. The diffuser design focuses on realizing an efficient diffusion in the front section and midsection, but in the aft section, the design objective shifts to obtaining a more uniform velocity distribution to meet the requirements at the inlet to the heat recovery steam generator (HRSG) in a combined-cycle operation.
