关键词: 固体颗粒冲蚀, 数值模拟, 再热1+1/2级, 汽轮机

Abstract: Solid particle erosion in the reheat stage seriously affects the safe and economic operation of the steam turbine. Taking twisted blades in the 1+1/2 reheat stage (the first stage and the adjacent nozzle) of one supercritical steam turbine as the study object, the three-dimensional motion trajectory of particles with different particle diameters is calculated based on Lagrange method, and the erosion characteristics on the blades caused by the solid particles under the conditions of different axial clearances between the rotor blade and the stator blade and different loads are researched by using Finnie erosion model. The results show that due to the high-speed rotation of the rotor blade, if the particles impact the rotor blade, they will obtain the speed of the mainstream in the opposite direction, and then rebound to the stator blade. The erosion performance in the reheat stage is mainly caused by the ‘repeatedly rebound’ of the particles with larger size in the axial clearance between the rotor blade and the stator blade. Increasing the axial clearance between the rotor blade and the stator blade properly can effectively reduce the number of the particles rebounded to the stator blade. When the axial clearance is 5 mm between the rotor blade and the stator blade, there are 10% particles rebounding to the stator blade, when the axial clearance is 8 mm, no particles rebound to the stator blade. As decreasing the load of the turbine unit, the rebound angle of solid particles is increased after impacting the blades as well as the number of the particles rebounded to the stator blade, and only a few particles can flow out the stator blade after the particles’ rebound in the axial clearance between the rotor blade and the next stator blade.

Key words: 1+1/2 reheat stage, numerical simulation, solid particle erosion, steam turbine