Optimization of turbine blade cooling using combined cooling techniques

Abstract

This paper presents analysis and optimization of turbine bade cooling systems. Since the temperature of combustion gases is very high sometimes reaching 2400 K, the turbine blade cannot sustain the resulting thermal stress. Moreover, for higher efficiency for advanced gas turbines, increase of inlet temperature is needed. Common blade cooling methods are film cooling, convection cooling, impingement cooling and combined cooling. In this paper, a numerical solution of the thermal and flow fields in film cooling technique on the AGTB expand symmetrical turbine blade was obtained and the results were validated with experimental data. Then the turbine blade geometry was changed and two combined cooling (impingement/convection cooing and impingement/film cooling) techniques were evaluated. The low Reynolds number k-ε turbulence model (AKN) was used for the turbulent flow simulations at various blowing ratios for two blade thicknesses. Comparisons of the results between the available experimental and numerical data showed that the AKN model is capable of predicting the turbulent flow and heat transfer in turbine blade cooling. Combined techniques (impingement/convection cooling and impingement/film cooling) were also carried out and more cooling effectiveness and uniform temperature distribution were found than film cooling method only.