Abstract
Thermal design for the trailing edge of a turbine vane is critically challenging because the thinnest trailing edge region has a low thermal capacity. The thermal mismatch can be further exacerbated by deposition of fine contaminant particulates resulting from the intake air. Changes of the surface conditions caused by deposition are able to affect film cooling and to enhance heat transfer substantially. However, the deposition layer has low thermal conductivity. The current study had uniqueness of evaluating deposition effects on vane trailing-edge film cooling by conducting deposition simulation experiments, where a scaled-up vane model featured cutback slots with a thick lip on the pressure surface. The coupling effects of deposition and the slot discharge coolant were investigated by examining the dynamic evolution of deposition and flow mixing. The film cooling performance was further assessed in adiabatic and conjugate heat transfer conditions to document the deposition-induced changes of heat/mass transfer and conduction. The thick slot lip and higher discharge ratios were found to reduce deposition, but simultaneously, to generate stronger mixing. Deposition on the pressure surface degraded adiabatic cooling effectiveness regardless of deposition thickness, whereas thicker deposition on the cutback surface was favorable to film cooling at the highest discharge ratio. The insulation effects of the deposition layer did not erase out the reduction in adiabatic effectiveness and potentially-increased heat transfer levels over the rough deposition surface, resulting in lower overall cooling effectiveness. The reduction in overall effectiveness, however, was alleviated by increasing the discharge ratio.
