Influence of Coolant Density on Turbine Blade Platform Film-Cooling

Abstract

Detailed parametric study of film-cooling effectiveness was carried out on a turbine blade platform of a five-blade linear cascade. The parameters chosen were — freestream turbulence intensity, upstream stator-rotor purge flow rate, discrete-hole film-cooling blowing ratio, and coolant-to-mainstream density ratio. The measurement technique adopted was temperature sensitive paint (TSP) technique. Two turbulence intensities of 4.2% and 10.5%; three purge flows between the range of 0.25% and 0.75% of mainstream flow rate; three blowing ratios between 1.0 and 2.0; and three density ratios between 1.1 and 2.1 were investigated. Purge flow was supplied via a typical double-toothed stator-rotor seal, whereas the discrete-hole film cooling was accomplished via two rows of cylindrical holes arranged along the length of the platform. The inlet and the exit Mach numbers were 0.27 and 0.44, respectively. Reynolds number of the mainstream flow was 7.5*105 based on the exit velocity and chord length of the blade. Results indicated that platform film-cooling effectiveness decreased with turbulence intensity, increased with purge flow rate and density ratio, and possessed an optimum blowing ratio value. The improved effectiveness with density ratio was further validated by the pressure sensitive paint (PSP) technique.

Influence of Unsteady Wake With Trailing Edge Coolant Ejection on Turbine Blade Film Cooling

“…The validity of the heat-mass transfer analogy for film cooling effectiveness measurement requires the reasonable approximation that the turbulent Lewis number be equal to unity, based on works by Nicoll and Whitelaw [30] and Jones [12]. More recently, the PSP analogy has made it possible to present high resolution conduction error free contours of film cooling effectiveness [31,32,33]. Therefore, we choose this method to obtain film cooling effectiveness and get high resolution results.…”