Through-flow calculation with a cooling model for cooled turbines

Abstract

Conjugate heat transfer is a key feature of modern gas turbine, as cooling technology is widely applied to improve the turbine inlet temperature for high efficiency. Impact of conjugate heat transfer on heat loads and thermodynamic efficiency is a key issue in gas turbine design. This paper proposes a through-flow method for the design of cooled turbines, taking into account the influence of the complicated interaction between the flow field and heat transfer in cooled turbines. The energy and continuity equations are rederived theoretically by considering the historical influence of cooling with the method that deals with viscous losses. A cooling model is introduced to the through-flow method to predict the coolant requirement. This paper applies the method in the design of a high-pressure turbine with convective cooling. With the prescribed blade temperature limitation and the knowledge of the flow variables of the mainstream at the turbine inlet, such as the total pressure, total temperature, and mass flow rate, the convergence of the calculation is then obtained and the properties of the flow field, velocity triangles, and coolant requirement are well predicted. Three-dimensional conjugate heat transfer analysis is performed for the validation of the through-flow method. By comparing these two calculations, it is shown that the through-flow method is a useful tool for flow analysis and coolant requirement prediction in the design of cooled turbines.