Effect of Diffuser Inhomogeneity on Full-Annulus Axial Turbine Performance

Abstract

Gas-turbine stacks are typically designed to be as short as possible, often featuring an aggressive diffuser and an exit plenum with a radial bend in order to reduce transmission shaft length. This can, however, cause flow inhomogeneity at the turbine outlet affecting performance. In this paper, the effect of such inhomogeneity is investigated utilizing experimentally supported full-annulus simulations of the turbine and exhaust sections. It is demonstrated that an inhomogeneous static pressure distribution can cause variation in upstream blade loading of up to 1.3 % in the Zweifel coefficient. This effect becomes stronger for higher diffuser inlet swirl angles, stressing the importance of interlocked turbine-exhaust section design.