Rotor Blade Heat Transfer of High Pressure Turbine Stage Under Inlet Hot Streak and Swirl

Abstract

A key consideration in high pressure (HP) turbine designs is the heat load experienced by rotor blades. Impact of turbine inlet nonuniformity of combined temperature and velocity traverses, typical for a leanburn combustor exit, has rarely been studied. For general turbine aerothermal designs, it is also of interest to understand how the behavior of leanburn combustor traverses (with both hotstreak and swirl) might contrast with those for a richburn combustor (largely hotstreak only). In the present work, a computational study has been carried out on the aerothermal performance of a HP turbine stage under nonuniform temperature and velocity inlet profiles. The analyses are primarily conducted for two combined hotstreak and swirl inlets, with opposite swirl directions. In addition, comparisons are made against a hotstreak only case and a uniform inlet. The effects of three nozzle guide vane (NGV) shape configurations are investigated: straight, compound lean (CL) and reverse CL (RCL). The present results reveal a qualitative change in the roles played by heat transfer coefficient (HTC) and fluid driving (“adiabatic wallâ€‌) temperature, Taw. It has been shown that the blade heat load for a uniform inlet is dominated by HTC, whilst a hotstreak only case is largely influenced by Taw. However, in contrast to the hotstreak only case, a combined hotstreak and swirl case shows a role reversal with the HTC being a dominant factor. Additionally, it is seen that the swirling flow redistributes radially the hot fluid within the NGV passage considerably, leading to a much â€کflatter’ rotor inlet temperature profile compared to its hotstreak only counterpart. Furthermore, the rotor heat transfer characteristics for the combined traverses are shown to be strongly dependent on the NGV shaping and the inlet swirl direction, indicating a potential for further design space exploration. The present findings underline the need to clearly define relevant combustor exit temperature and velocity profiles when designing and optimizing NGVs for HP turbine aerothermal performance.