Experimental and numerical investigations of overall cooling effectiveness on a vane endwall with jet impingement and film cooling

Abstract

In this paper, a conjugate heat transfer model for the endwall of a turbine four-vane linear cascade is developed to examine the conjugate cooling effects generated by internal jet impingement and external film cooling as well as heat conduction through the metal endwall. Aerodynamic and geometrical parameters are appropriately scaled to match engine conditions. The conjugate model with a maximum Biot number of 1.5 is tested in engine-like oncoming flows with a turbulence intensity of 9.8% and an integral length scale of 10 mm. The effects of varying passage inlet Reynolds numbers from 1.40 × 105 to 4.20 × 105 and coolant-to-mainstream mass flow ratios from 1.5% to 3.8% are investigated by using experimental measurements and numerical simulations in the presence of an upstream slot. Both experimental and numerical results reveal that overall cooling effectiveness on the endwall increases with the increase of coolant mass flow rate. The effects of passage flow inlet Reynolds number on endwall overall cooling performance are more complicated, that depends on competing effects of internal and external heat transfer. Overall cooling effectiveness is found to be significantly enhanced in the vicinity of the film cooling holes due to higher in-hole convective heat transfer levels. Computational results, which show good agreement with measurements, provide additional information of thermal behavior in the endwall and explain why there is improvement with coolant mass flow ratio.