Numerical evaluation of the blade cooling for the supercritical steam turbine

Steam turbine systems for supercritical parameters are one of the most important directions of the development of conventional power plants. A steam turbine working in such cycles has to be adjusted to operation with higher and higher steam temperatures. The aim of this analysis is to determine the cooling conditions of the blades of the steam turbine first stage. The cooling is supposed to ensure that the same materials as those used for the live steam temperature of 873 K are used for the first blades operating with the live steam temperature of 923 K. In the calculations the Conjugate Heat Transfer (CHT) model is used to simulate the following phenomena: the fluid flow in the blade-to-blade cascade, the heat transfer in the blade and the coolant flow in the holes. Analyses of different cooling steam parameters and of different turbulence levels of the main flow are performed. The problem is analysed for the steam conditions corresponding to the first blade of High Pressure (HP) and Intermediate Pressure (IP) turbines, respectively. For the HP turbine the on-blade thermal barrier is considered as an additional mean to reduce the metal temperature to the limit required.