The Numerical Modelling Of Heat Transfer InTurbine Blades

Abstract

Advanced aircraft engines employ turbine entry temperatures so high that cooling of the turbine blades is crucial. This paper focuses on the ribs generally used to enhance the heat transfer in turbine blade cooling passages. Secondary flows associated with these ribs are responsible for significant local heat transfer variations. Furthermore, the ribs produce a complex flow structure so that there is continuing need for a better understanding of the flow physics in ribbed ducts. The flow in a channel with four consecutive ribs on two opposite walls and a blockage ratio equal to 0.063 were simulated for angles of 90° and 60° to the flow direction and a Reynolds number of 80000. An inlet condition approximating fully developed flow in a smooth duct were used. In the case of the 60° angled ribs, there is a strong sideways secondary flow component which produces both increased overall heat transfer as well as asymmetrical local heat transfer enhancement. The results show the pressure loss and heat transfer enhancement for both rib angles. In general the predicted heat transfer rates and pressure losses compared well with measured data in the stable area. NOMENCLATURE C^Cj Turbulence constants Ĉ E Turbulence constants k Turbulent kinetic energy p Pressure Pe Peclet number Pr Prandtl number q Heat flux Re Reynolds number St Stanton number v Velocity Vt Tangential velocity d Distance to the wall e Rate of dissipation p Density <7,,cTk Turbulence constants T Shear stress /A Viscosity INTRODUCTION Increased engine efficiency in modern aircraft engines requires a high turbine inlet temperature for a given pressure ratio. These high turbine inlet temperatures are only possible by proper cooling of the different turbine components. Of the components the rotor blades deserve special attention because they have to content with high Transactions on Engineering Sciences vol 5, © 1994 WIT Press, www.witpress.com, ISSN 1743-3533