Novel Blade Cooling Engineering Solution

Abstract

The evolution of increasing turbine inlet temperature has led to the necessity of full-coverage film cooling for the first turbine vane and blade. In this paper a new approach using transonic wall film jets for blade and vane cooling is investigated to provide a first guideline for engineering design. The first part presents a Computation Fluid Dynamics (CFD) cooling efficiency investigation on a flat plate with varied injection angles, turbulence intensities and blowing ratios. The results show a strong tendency to bend towards the roundness at cooling slit outlet. Therefore the cooling efficiency isn’t hardly influenced by cooling supply angle. Further it has been noticed that high mainflow turbulence coupled with a high mainflow velocity leads to a high turbulent kinetic energy in the mainflow, affects the cooling efficiency. This investigation with different turbulence intensities shows further, that turbulence intensity rate Tu [%] isn’t a suitable dimension to rate the “destructive Power” of mainflow turbulence to cooling jets. With these results detailed 2D- and 3D-Navier-Stokes external flow calculations coupled with the appropriate solid heat conduction calculations for a cooled turbine blade were modelled. Therefore a blade with five cooling slit rows was used. Two slit rows for trailing edge cooling and one slit row for pressure and suction side respectively and one slit row for the leading edge were used to model a full preserved blade. On the basis of heat transfer and temperature distribution of the 3D-CFD calculation of the blade a Finite Element Analysis (FEA) was realised, showing the points of maximum stresses.