The Effect of Geometry on the Aerodynamics of a Prototype Gas Turbine Combustor

Abstract

The method of admission of the swirling flow to the combustion chamber has a strong influence on the flow field structure in Gas Turbine Combustors (GTC). Two different exit configurations are studied. The first configuration is that of a swirl cup that ends only with a splash plate such that there is a sudden unguided expansion as the flow emanates from the swirl cup. The second is a swirl cup that ends with a splash plate and an asymmetric combustion dome. Laser Doppler Velocimetry (LDV) measurements are conducted in the horizontal plane (X-Y), for both configurations, 5mm from the flare exit. Also, LDV measurements are conducted in two vertical planes passing by the combustor centerline (X-Z and Y-Z). The results reveal a significant difference in the flow structure for both configurations. The combustion dome appears to reduce the turbulence activities close to the exit of the swirl cup. In addition, the presence of the combustion dome eliminates the corner recirculation zone and the low velocity region close to the combustor walls. It is interesting to see that the asymmetry of the combustion dome (9° difference in the expansion angle on both sides) results in a significant asymmetry in the velocity magnitude as well as the turbulence activities. Moreover, the asymmetry in the combustion dome results in a tilting of the CRZ toward the surface with the higher expansion angle. The results highlight the importance of the proper and careful design of the GTC front section. The experiments are conducted in a dump combustor (rectangular cross section). To study the effect of the chamber geometry on the flow field, the base configuration is installed in an annular combustor sector and LDV measurements are conducted in the axial radial plane (X-Z). The flow field as well as the shape of the CRZ are significantly different in both cases. The CRZ height reduced by 40% with the swirl cup installed to the SAC sector. The results emphasize the strong influence of the confinement on the flow structure.