Comparative Investigation of HPT Blade Cooling Concepts in an Aerothermal Test Rig

Abstract This study presents a comparative investigation of complex high-pressure turbine blade cooling concepts, incorporating internal and external cooling features in upscaled realistic turbine blade models. The performance of various cooling configurations is evaluated in an annular cascade test rig under engine-representative aerothermal flow conditions. Two back-to-back investigations are carried out: one focused on variations in film-cooling configurations by adjusting cooling hole angles and fan-shaped hole designs and the other focused on internal cooling configurations by comparing a rearward and a forward-flowing multipass cooling concept. The total cooling effectiveness (TCE) of each cooling system is assessed using surface temperature measurements obtained via infrared thermography. Multiple optical accesses at the test rig enable temperature measurements across most of the blade surface. The results show that modifications to the film-cooling configuration, particularly the use of fan-shaped holes at the leading edge, lead to significant improvements in total cooling effectiveness with local enhancements of up to 20% near the holes and an improvement of around 10% on average at the leading edge. Regarding the variation in the multipass flow direction, a distinct shift in cooling effectiveness from the front to the rear part of the blade is demonstrated. Additionally, the forward-flowing multipass configuration results in a more uniform total cooling effectiveness along the blade profile. These findings emphasize the necessity of a holistic approach in testing and evaluating cooling systems for turbine blades, as individual design changes can have significant effects on the cooling effectiveness.