A Numerical Study on Reducing the Stator Blade Surface Temperature in the Ultra-High Efficiency Gas Turbine Engine by Indexing Fuel Injectors and Using Film Cooling

Abstract

The Ultra-High Efficiency Gas Turbine technology, UHEGT, has been introduced in our previous publications [1]-[4]. In UHEGT, the combustion process is no longer contained in isolation between the compressor and turbine, rather distributed and integrated within the axial gaps before each stator row. As shown in the previous publications, this technology substantially increases the thermal efficiency of the engine to 45% and above. Since the combustion process is brought into the turbine stages in UHEGT, the stator blades are exposed to high temperature gases and are prone to be overheated. To address this issue, two different approaches are investigated in this paper in order to control and reduce the temperature on the stator blade surface. The first approach is indexing (clocking) of the fuel injectors (cylindrical tubes extended from hub to shroud), in which the positions of the injectors are adjusted relative to each other and the stator blades. The second approach is using film cooling, in which cooling holes are added on the blade surface to bring down the temperature via coolant injection. Four configurations are designed and studied via computational fluid dynamics (CFD) to evaluate the effectiveness of the two approaches. The objective functions in this evaluation are stator blade surface temperature, temperature non-uniformity at rotor inlet, total pressure loss over the injectors, and total power production by rotor. The results show that the second configuration, which uses the indexing approach, presents the most promising case in controlling the stator blade surface temperature. This configuration produces the lowest temperature distribution over the stator blade surface and the least amount of total pressure loss.