Experimental Investigations of the Film Cooling Performance of a Micro-Tangential-Jet Scheme on a Gas Turbine Vane: Part 2 — Heat Transfer Coefficient

Abstract

This paper presents experimental investigations of the Heat Transfer Coefficient (HTC) performance of a Micro-Tangential-Jet (MTJ) Film cooling scheme on a gas turbine vane using transient Thermochromic Liquid Crystal (TLC) technique. In part I of this paper, the film cooling effectiveness performance of the MTJ scheme was presented. The MTJ scheme is a micro-shaped scheme designed so that the secondary jet is supplied parallel to the vane surface. In order to supply the jet in a direction parallel to the vane surface, extra material was added on both pressure and suction sides. The added material is expected to produce more turbulence and hence increase the HTC values. The investigations showed that the increase in the HTC due to the presence of the MTJ scheme is very close to that resulting from the presence of normal traditional shaped schemes on the pressure side. Meanwhile, reduction in the HTC is recorded on the suction side. Such performance is attributed to the small overall height of the scheme which helped keeping the resulting turbulence at minimum. Moreover, the HTC distribution downstream the MTJ scheme is uniform in the lateral directions, which helps minimize the thermal stresses. To judge the overall performance of the MTJ scheme, the Net Heat Flux Reduction (NHFR) parameter is used. The NHFR represents a combination of the effects of both the cooling effectiveness and the HTC. Great enhancement in the NHFR performance of the MTJ was observed compared to traditional shaped schemes. The investigation showed that a blowing ratio close to unity, based on the scheme exit area, could be considered optimal for the MTJ scheme.