Suction Side Film Cooling Under Near-Engine Conditions: Influence of Sequential Addition of Film Cooling Rows on Cooling Performance

Abstract This study examines the cooling performance of film-cooled turbine blades under hot gas conditions. Starting from a baseline blade without film cooling, the film cooling rows are sequentially added to the suction side. This approach allows for comparative analysis and separation between the effectiveness of film cooling and the internal convective cooling. Turbine blades derived from the mid-span section of an industrial high-pressure gas turbine are investigated experimentally in a high-temperature linear cascade at temperatures up to 1250 K. The hot gas flow is characterized by an inlet Reynolds number of Re = 120 000, an inlet temperature between 1050 K and 1250 K and an outlet Mach number of M = 0.7. Testing at high temperatures serves to better match coolant flow similarity parameters that cannot be simultaneously matched in a typical cold air test rig. Three cooling configurations were tested: a convectively cooled baseline blade, a blade with an addedfilm cooling row on the suction side near the leading edge, and a blade with two additional film cooling rows. This approach clearly demonstrates the cooling improvements that come from adding film cooling rows. The cooling performance of each configuration is evaluated based on the overall cooling effectiveness ϕ of the blade. Utilizing the measurements of the baseline geometry, the effects of internal cooling and film cooling are separated and their additive effects are shown. While the single-row configuration demonstrates only local effectiveness gains, the three-row configuration shows an improvement in cooling effectiveness Δϕ ≈ 0.2 compared to the baseline blade. In conclusion, we show how the addition of film cooling rows improves the overall cooling effectiveness in a near-engine environment. The data and analysis we present can serve to judge numerical models used for industry application with respect to their validity under hot gas conditions.