Thermal Analysis of a Cooled Turbine Blade

Abstract

Using Computational Fluid Dynamic (CFD), a gas turbine with an air-cooled blade was analyzed thermally. In terms of design, the domain was divided into three regions. The first region is the blade to blade passage (external flow) governed by a quasi-3-D Euler equation in a conservative form. Mac-Cormack’s technique algorithm based on the finite differences, was used for this region. The second region involves the coolant passage (internal flow). This region involved the use of 2-D axi-symmetric Navier Stokes equations (Finite volume with staggered grids). A 3-D Laplace heat transfer equation was applied for the third region which involves a blade metal, where the solution algorithm was based on the finite difference technique. Consequently, to achieve temperature distribution through blade metal, the three regions have been coupled via the external and internal boundaries. Six different cases were examined in same blade geometry. The effect of gas heat transfer coefficient was analyzed in cases 1 and 2. With regards to cases 3, 4, 5, and 6, gas and coolant temperatures were changed. The computational results showed that the blade surface (metal) temperature is cooler than the surrounding gases (external hot gases) by about 100-500 °C, depending on boundary condition. An increase in gas temperature by 100 °C resulted in 50-100 °C increase in metal temperature, while, an increase in coolant temperature by 100 °C resulted in an average 50 °C increase in blade temperature. The results also show a temperature difference in blade metal of 250 - 450 °C between the leading and trailing edges.