Heat Transfer Over Non-Porous and Porous Smooth End Wall of a Linear Guide Vane in the Presence of Freestream Turbulence

Abstract

The end wall of a gas turbine guide vane is one of turbine components where cooling is extremely complex due to a three-dimensional fluid flow and heat transfer nature. Most existing end wall heat transfer data were obtained over a non-porous surface with no effect of freestream turbulence. In real situations the typical turbulence level in front of a guide vane varies widely and reaches 25–30 % in some modern gas turbine engines. No doubt, this factor should be taken into account in the design of end wall cooling systems. New experimental results are presented in this paper describing the effect of freestream turbulence on local heat transfer over non-porous and porous smooth end walls of the same configuration. A linear scaled-up model of a real gas turbine guide vane was employed in the experimental programme. Decay of the axial freestream turbulence in a space between adjacent blades was measured and two simplified versions of the experimental correction functions describing the effect of freestream turbulence on local end wall heat transfer were obtained. The derived correction functions include the axial component of freestream turbulence and should be envisaged as a first attempt to define quantitatively the effect of freestream turbulence over an end wall in different conditions. It was found that both correction functions are virtually identical and agree satisfactorily with the published experimental data, reflecting the effect of freestream turbulence over a flat plate. It confirms the approximately common character of freestream turbulence influence for different boundary conditions. It was concluded that further experimental studies of three-dimensional turbulent structure over an end wall for various boundary conditions are required to develop more exact correlations.