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 lean-burn combustor exit, has rarely been studied. For general turbine aerothermal designs, it is also of interest to understand how the behavior of lean-burn combustor traverses (with both hot-streak and swirl) might contrast with those for a rich-burn combustor (largely hot-streak 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 hot-streak and swirl inlets, with opposite swirl directions. In addition, comparisons are made against a hot-streak 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 wall”) temperature, Taw. It has been shown that the blade heat load for a uniform inlet is dominated by HTC, whilst a hot-streak only case is largely influenced by Taw. However, in contrast to the hot-streak only case, a combined hot-streak 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 ‘flatter’ rotor inlet temperature profile compared to its hot-streak 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.

Effect of a Combined Hot-Streak and Swirl Profile on Cooled 1.5-Stage Turbine Aerodynamics: An Experimental and Computational Study

“…The first study, reported by Khanal et al [27], concluded that the effects of combined hot-streak and swirl profiles at turbine inlet were not well predicted by a simple superposition of their predicted effects when imposed separately. The second study, reported by Rahim and He [28], concluded that the hot-streak migration through the HP vane was significantly altered by the introduction of swirl and, as a result, the vane exit total temperature profile and blade heat transfer characteristics were significantly modified.…”

Turbine blade tip aero-thermal management: Some recent advances and research outlook

“…One of such aspects is the impact of incoming flow conditions, e.g., total pressure and temperature non-uniformities (e.g., Zhang et al, 2014;Coull and Atkins, 2015). It has also been shown that turbine stage inlet velocity and temperature profiles (swirl and hot streak) can have considerable impact on the rotor blade tip heat load (Rahim and He, 2015). Another factor pertinent to the present interest is the relative movement of casing.…”

Heat transfer characteristics of a high-pressure turbine under combined distorted hot-streak and residual swirl: an unsteady computational study

“…Many studies are now available in the literature [18][19][20][21][22][23][24] . However, works on combined residual swirl and hot-streak effects on rotating HPTs are rare in the literature [25][26][27][28][29][30] . The majority of these works are numerical and they adopt an idealized circular or elliptical hot-streak shapes, which are not representing realistic distorted shapes generated by aero-engine combustors.…”