Flow and heat transfer characteristics in middle pressure turbine stage in supercritical steam turbines

The coupling of the flow field calculation and the conjugate heat transfer method was employed to investigate the cooling characteristics of the steam from the high pressure cylinder of a supercritical steam turbine to cool the solid parts of the first stage in the middle pressure cylinder and the influence of the cooling effect on aerodynamic performance of the first stage. The flow field and the temperature field in the first stage of the middle pressure cylinder with steam cooling were compared with those without steam cooling. The results show that the steam cooling technology can effectively reduce the temperature of the rotor blade, blade root, rotor and wheel disc of the first stage. The cooling steam flowing through the cooling holes by pumping action of the cooling holes has obvious cooling effect on the cooling holes and their surrounding area. The temperature of the rotor system of the first stage in the middle pressure cylinder decreases by up to 80 K. In addition, part of the cooling steam enters the main flow passage of the first stage and mixes with the main flow, leading to greater hub reaction and strength of the passage vortex.