Quantifying Part-to-Part Flow Variations and Cooling Effectiveness in Engine-Run Blades

As turbine inlet temperatures continue to increase for modern gas turbine engines, the lifing of hot section components operating in a range of environments is becoming increasingly challenging. Engine operations in harsh environments can cause a reduction in cooling capability leading to reduced blade life relative to existing experience. This study analyzes the effects of harsh environments on the deterioration of blade flow and cooling effectiveness in turbine blades by comparing three commercially operated engines with varied operational times referenced against a baseline blade. Spatially resolved surface temperatures measured using infrared thermography at high-speed rotating conditions were evaluated to determine variations in cooling effectiveness as a function of engine operation and blade-to-blade variability from the different commercial applications. Engine-run blades were found to have reduced flow as well as greater part-to-part variation when compared to baseline blades. Blade surface temperature measurements on the deteriorated operational blades indicated film cooling traces dissipated closer to the hole exit relative to baseline blades. Furthermore, the cooling effectiveness varied significantly even between blades from the same engines. The reduction in cooling effectiveness in the engine-run blades led to higher blade temperatures and significantly shorter component life, with some exhibiting as much as an 18% reduction in life compared to baseline blades. This knowledge allows lifing models to be developed toward predicting blade operational effects in harsh environments.