Session: 12-08: Film Cooling Under Engine Like Conditions

Paper Number: 151664

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

This study examines the cooling performance of film-cooled turbine blades. Starting from a baseline blade without film cooling, film cooling rows are sequentially added to the suction side. This approach allows for a 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 8 MW class 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, inlet temperatures between 1050 K and 1250 K and an outlet Mach number of Ma = 0.7. The use of high temperatures serves to better match coolant flow similarity parameters that cannot be simultaneously matched in a typical cold air test. For example, the specific heat ratio, the coolant-to-freestream Reynolds number ratio or the density ratio. A range of three different coolant temperatures and three coolant mass flows is used, resulting in coolant-to-freestream temperature ratios TR between 0.3 and 0.5 and blowing ratios BR between 0.7 and 3.0. Three different cooling configurations are investigated. First, a convectively cooled baseline blade was tested. Second, a film cooling row was added on the suction side near the leading edge of the blade. Finally, two additional film cooling rows were added. In this way, we can clearly show the improvements in cooling effectiveness of the different configurations due to the film cooling. The cooling performance of each configuration is evaluated based on the blade metal temperature measurements, resulting in the overall cooling effectiveness phi of the blade. Utilizing the measurements of the baseline geometry, the effects of the internal cooling and the film cooling are separated and additive effects are shown. While the single-row configuration demonstrates only local effectiveness gains, the three-row configuration shows an improvement in cooling effectiveness of Delta phi=0.2 compared to the baseline blade.

In summary, we show how the addition of film cooling rows improves the overall cooling effectiveness. This unique experiment, conducted under near-engine conditions, ensures a closer match of coolant similarity parameters and makes the results highly applicable to real engine cases. Consequently, the data we present can serve as a benchmark for validating both industrial tools and numerical calculations.

Presenting Author: Jan Lemmer RWTH Aachen University

Presenting Author Biography: Jan Lemmer received his Master's degree in Mechanical Engineering from the Technical University Darmstadt, Germany. He is currently pursuing his Ph.D. as a researcher at the Institute of Jet Propulsion and Turbomachinery, where he is conducting experimental research on film-cooled turbine blades. His areas of interest include turbine cooling, aerodynamics, high temperature flows and heat transfer.

Authors:

Jan Lemmer RWTH Aachen University
Yanik Kleine-Hollenhorst RWTH Aachen University
Michael Rabs MAN Energy Solutions SE
Peter Jeschke RWTH Aachen University