Experimental Study on Overall Cooling Effectiveness of Turbine Nozzle Guide Vane with Impingement-Cutback Structure

The overall cooling performance of turbine nozzle guide vane, with the impingement-cutback structure, is experimentally studied in the actual-scale cascade. The gas with the high temperature is used to achieve the actual dynamic viscosity coefficient and the density ratios. The coolant-to-gas mass flow ratio (KG) varies between 0.034 and 0.050 and the gas-to-coolant temperature ratio (KT) varies between 1.5 and 2.4. The local Overall Cooling Effectiveness (OCE) on the middle cross-section of the vane is obtained. The experimental results reveal that the lowest value of the OCE achieves a 10% relative arc length on the suction side of the vane; however, the highest value appears at 40% relative arc length on the pressure side of the vane. The averaged values of the OCE are respectively enhanced by 19.45%, 24.22%, and 35.57% at temperature ratios equal to 1.7, 1.9, and 2.3, with an increase of the KG from 0.034 to 0.050. Added to that, it was identified that an increase of KT from 1.7 to 2.3 leads to the decrease of the OCE. The comparison results show that this characteristic becomes dramatical while KG is 0.034. The higher KT leads to a greater influence of KG, which is illustrated clearly by the compared results of the OCE.