Numerical Study on Aero-Thermal Performance of HP Turbine Endwalls Under Influence of Hot Streak and High Mainstream Turbulence

Abstract

In this paper, unsteady RANS simulations were performed at two hot streak (HS) circumferential positions with inlet turbulence intensity of 5% and 20%. The interacted HS and high mainstream turbulence effects on endwall heat transfer characteristics of a high-pressure (HP) turbine were discussed by analyzing the flow structures and presenting the endwall adiabatic wall temperature, heat transfer coefficient (HTC) and heat flux distributions. The results indicate that both the wall temperature and HTC increase with the turbulence intensity at most stator endwall regions. In addition, the increase of wall temperature plays a greater role than HTC of influencing the wall heat flux. However, higher turbulence intensity decreases the intensity of the stator passage horse-shoe vortex, also the corresponding region HTC and heat flux are reduced. In rotor passage, the variation of HS circumferential position would alter the hub and casing endwall temperature, however, the discrepancy is weakened at higher turbulence. The elevated HS attenuation at higher turbulence results in temperature augmentation at the leading edge of rotor hub and casing endwalls, while temperature decrease after 50% axial chord, thus obtains more uniform temperature distributions on the endwalls. However, the rotor endwall HTC is only augmented significantly at the leading edge on hub endwall, and pressure side and downstream of trailing edge on casing endwall. Variation of HTC and adiabatic wall temperature jointly determines the rotor hub and casing endwall heat flux, and the temperature variation has dominant effects in the most regions. In general, the variation of adiabatic wall temperature and HTC should be considered simultaneously when analyzing the turbine endwall heat transfer characteristics.