Solid Oxide Fuel Cell Turbine Subsystem Performance, Test Program for High Efficiency Gas Turbine Exhaust Diffuser

This project will develop a new exhaust diffuser for a power-generation combustion turbine. The exhaust diffuser will be an aerodynamically-shaped duct section located just downstream of the last turbine wheel. The concept will be applicable to gas turbine exhausts that have struts in the diffuser, which includes nearly all large electric power turbines. The approach involves improving strut flow by guiding flow into the strut more directly, thereby reducing sideways flow. Aerodynamically speaking, the strut angle of attack is reduced. The flow is guided by one or more strutlets that are added next to and just ahead of the main strut. These strutlets will be studded with small vortex generator vanes, to further guide flow over the main strut. Phase I will test for flow efficiency and stability in a large scale model that includes the strutlet concept. In Phases II and III, other diffuser flow improvements will be added, and the complete diffuser will be demonstrated in an operating power plant. Commercial Applications and other Benefits as described by the awardee: The technology should enable a one-half percent increase in power and efficiency, averaged over the U. S. turbine fleet. A one-half percent reduction in natural gas fuel use would reduce fuel costs by $261 million annually, based on 2005 reported fuel use and prices.