Experimental investigation of heat transfer characteristics on turbine endwall with full coverage film cooling

Transient heat transfer measurement by Thermochromic Liquid Crystal (TLC) is applied in this paper to investigate heat transfer characteristics of the nozzle endwall with full coverage film cooling. The endwall heat transfer coefficient (h) with different blowing ratios (M) ranging from 0.7 to 4.0 at a constant mainstream Reynolds Number 1.63×10⁵ is measured and analysed. The experiment results show that the heat transfer characteristics of the endwall are significantly affected by the film cooling. However, this effect changes with blowing ratio and varies in different regions of the endwall. At low M (M=0.7), coolant jets get into the boundary layer of the secondary flow, and enhance heat transfer, but lead to highly uneven h on the endwall. With the increase of M, coolant jets start to detach from the endwall while the turbulent mixing begins to enhance the heat transfer of the endwall downstream. Therefore h on the endwall first decreases and then increases with M. However, different turning points (the cases of M = 1 or M = 1.5) and increasing trends with M (staying constant or increasing monotonically) appear in different regions of the endwall.