Research on Centrifugal Effects on Turbine Rotor Blade Film Cooling.

Film cooling has been studied on the rotor blade of a large scale (low speed) model of a high pressure turbine first stage. Film coolant was discharged from single holes on the pressure and suction surfaces on the airfoil. For each blowing site the coolant-to-free stream mass flux ratio and density ratio were varied from 0.5 to 1.5 and from 1.0 and 4.0 respectively. Both surface flow visualization and local film cooling effectiveness data were obtained. Film coolant effectiveness data is presented in the form of effectiveness profiles and contours downstream of each hole. The observation was made that although it can have a strong radial component, the trajectory of the film coolant was very insensitive to coolant flow conditions. The existence of the radial component of the film coolant trajectory was found to have a strong impact on the nature of the effectiveness distributions. The data have been compared with data taken by other investigators on flat surfaces and in plane cascades. Agreement between the flat plate data and the suction surface data was reasonably good. However, the pressure surface results showed a much faster decay of the effectiveness than did the flat plate data due to effects thought to be related to both curvature and radial flow. (Author)