Thermal performance degradation induced by transition piece wall thickening in gas turbine

With recent advancements, conventional gas turbines have been uprated to operate at higher turbine inlet temperatures than originally designed, incorporating technologies from newer-generation machines. As part of these upgrades, the thickness of critical components, such as the combustor, has been increased to withstand elevated thermal loads. This study investigates the effect of a thickened transition piece (T/P) on the thermal performance of the first-stage vane endwall. Experiments were performed in a linear cascade with secondary chambers supplying purge and film cooling flows at 1.50 % and 0.12 % of the mainstream flow, respectively. T/P wall thicknesses of 1.0, 1.5, and 2.0 times the baseline were tested. Heat transfer coefficients were obtained using the naphthalene sublimation method, while adiabatic film cooling effectiveness was measured with the pressure-sensitive paint technique. Cooling performance was evaluated through net heat flux reduction (NHFR) analysis. The results indicate that increasing T/P wall thickness considerably degrades cooling performance and increases the non-uniformity of cooling between passages. When the T/P wall thickness was doubled, the area-averaged NHFR in the pressure-side passage decreased by 41.1 %, compared to only 12.4 % in the suction-side passage. Key findings from this study provide practical guidance for future gas turbine cooling designs involving thickened transition piece wall.