Research On Characteristics Of Solid Particle Erosion Of Governing Stage In Steam Turbine

With the growth of power demand,steam turbines are developing towards the direction of high-parameters and large-capacity.The increase of initial temperature and initial pressure of steam is easier to cause the oxide scale to fall off in the boiler and steam pipeline.These iron oxide particles enter into the steam turbine with the high-temperature and high-pressure steam,and cause serious erosion damage to steam turbine components,which greatly reduces the economic advantage brought by the increase of the initial parameters of units.Therefore,it is of great significance to study the solid particle erosion(SPE)characteristics in steam turbine.Based on Euler-Lagrange method and Finnie erosion model,this paper takes a 600MW steam turbine as the research object,and the SPE characteristics in governing stage and governing valve are studied respectively by using the three-dimensional numerical simulation software ANSYS-CFX.The main work is as follows:First,the geometric model of whole-cycle governing stage was established,and the steam-particle flow characteristics in governing stage of steam turbine with four governing valves were simulated.The influence of two types of governing modes on SPE characteristics in the governing stage was studied in detail and the influence of SPE on steam turbine economy was analyzed by combining the change of governing stage efficiency caused by roughness.Results show that the erosion rate density of different circumferential nozzles changes greatly,and the erosion rate density of the most serious erosion nozzle is about 4×103 times that of the lightest erosion nozzle.The max erosion rate density of nozzle under sequential valve governing mode is higher than that under single valve governing mode,in which the particle impact velocity plays a decisive role.With the increase of roughness,the governing stage efficiency decreases under two types of governing modes.Moreover,the governing stage efficiency under sequential valve governing mode decreases more obviously than that under single valve governing mode.Second,the geometric models of governing valve with different opening were established.and the steam-particle flow characteristics in governing valve of steam turbine were simulated.The influence of different opening on the SPE characteristics in governing valve was studied in detail,and the erosion law under different particle size was analyzed.Results show that the serious erosion area is found mainly on the valve chest bottom and throat under the large and medium lift conditions,but on the valve diffuser under the small lift condition.With the decrease of valve opening,the erosion rate density increases.Compared with the L/D=28.8%opening condition,the erosion rate density increases by about 87%under the L/D--4.8%opening condition.The impact velocity is the main factor affecting the erosion rate density when the governing valve opening changes from large to medium lift,but the impact angle is the main factor when the governing valve opening changes from medium to small lift.With the increase of particle size,the erosion rate density increases first and then decreases under three valve opening conditions,and the max erosion rate density is found in the particle size range of 40?m-60?m.