ICOPE-15-C112 Design of Dewetting Slot Structure for A Nuclear Power Steam Turbine

Abstract

Steam turbine plays an important role in electrical power generation plant. The presence of water droplet in the steam turbine has adverse effects on turbine efficiency and mechanical performance of turbine components. For large capacity steam turbine, long rotor blade are used on the last stage. The wet-steam issue in nuclear steam turbines is far more severe than fossil turbines due to their saturated inlet main steam and longer blades. Taking a steam turbine of CAP 1400 unit as an example, the non-equilibrium condensation models were employed to investigate the condensing flow, the water droplet size distribution, and the dewetting capacity through the last stages of the low-pressure steam turbine. In order to investigate the deposition distribution of fog water droplets on the surface of blades, the small droplet model is used. And to capture the deposition distribution of coarse water droplets, the particle-tracking model is used. As the wet-steam flows in low-pressure steam turbines are highly three-dimensional and cannot be represented by one-dimensional or two-dimensional models accurately, this paper established a three-dimensional model for the last stage of the steam turbine with 1828mm length rotor blade at first. Then, based on numerical simulation results of the condensing flow and distribution of water droplet along the blade, the paper compared different schemes of suction slot on the stator blade. Finally, according to the slot suction ratio, stage efficiency, isentropic efficiency, it proposed an optimum dewetting structure for this stage, the dewetting slot should be set on the position at the 60% relative height, 80% width on pressure side, and 20% width on suction side.