High Freestream Turbulence Effects on Endwall Heat Transfer for a Gas Turbine Stator Vane

Abstract

High freestream turbulence along a gas turbine airfoil and strong secondary flows along the endwall have both been reported to significantly increase convective heat transfer. This study superimposes high freestream turbulence on the naturally occurring secondary flow vortices to determine the effects on the flowfield and the endwall convective heat transfer. Measured flowfield and heat transfer data were compared between low freestream turbulence levels (0.6%) and combustor simulated turbulence levels (19.5%) that were generated using an active grid. These experiments were conducted using a scaled-up, first stage stator vane geometry. Infrared thermography was used to measure surface temperatures on a constant heat flux plate placed on the endwall surface. Laser Doppler velocimeter (LDV) measurements were performed of all three components of the mean and fluctuating velocities of the leading edge horse-shoe vortex. The results indicate that the mean flowfields for the leading edge horseshoe vortex were similar between the low and high freestream turbulence cases. High turbulence levels in the leading edge-endwall juncture were attributed to a vortex unsteadiness for both the low and high freestream tubulence cases. While, in general, the high freestream turbulence increased the endwall heat transfer, low augmentations were found to coincide with the regions having the most intense vortex motions.

Modelling of heat transfer and fluid flow in the hot section of gas turbines used in power generation: A comprehensive survey

“…There are numerous end wall flow field and heat transfer studies. Radomski et al investigated the effect of high turbulence on end wall heat transfer. They found that the highest heat transfer is at the junction between the leading edge and the end wall.…”

“…Radomski et al found that high free stream turbulence along a gas turbine aerofoil and strong secondary flows along the end wall significantly increased convective heat transfer. In this experiment, flow field and heat transfer data were measured and compared with low free stream turbulence levels of 0.6%.…”

Improving Purge Air Cooling Effectiveness by Engineered End-Wall Surface Structures—Part II: Turbine Cascade

“…Near the trailing edge, a significant increase in heat transfer exists mainly due to the strong mixing of two flows from both sides of the blade. The effect of free stream turbulence was considered in the study of Kang and Thole [10] and Radomsky and Thole [11]. It was found that the heat transfer increases as the turbulence intensity increases.…”