Study On Salting Out Two-phase Flow Characteristics In Steam Turbine Stage

Salt deposition in steam turbine stage has been widely concerned by experts and scholars.When salt deposition occurs on the surface of steam turbine blade,it will reduce the efficiency of steam turbine and affect the safe and economic operation of power plant.In this paper,a group of moving and stationary blades of the IP cylinder of a 600 MW condensing steam turbine are taken as the research object by means of numerical calculation and fluent software.Taking steam and salt dissolved in steam as the flow medium,this paper studies the velocity distribution of salting out two-phase flow,salting out particle deposition rate,denudation rate and the flow characteristics of different kinds of salt in the stage under different working conditions.The main research work and results are as follows:Firstly,this paper expounds the complex micro behavior of particles in the process of salt deposition,the basic theory of population balance model and deposition denudation model,which provides a theoretical basis for compiling the UDF of the above model.The geometric model is established according to the actual power plant data,and then the grid is divided.By comparing the changes of particle number in different grid division methods,the independence of grid number is verified.We compare the simulation results of this paper with those of other scholars in the literature to verify the reliability and rationality of the calculation model.Secondly,the microscopic behavior of salting out particles in the steam turbine stage is studied and analyzed,and the variation laws of each order moment of particles in the nucleation growth process and coalescence crushing process at the same position in adjacent cycles are compared.This paper explores the distribution of the number of salting out particles on the surfaces of moving and stationary blades with time.Moreover,the variation laws of steam velocity,saturated salt content,salting out particle deposition rate and denudation rate are further analyzed.Finally,because the steam turbine rarely operates under rated conditions,and the types of salt deposition in the stage are not single,this paper simulates the flow characteristics of different types of salting out particles under different conditions.Through comparative analysis,it is found that with the increase of load,the density and flow rate of superheated steam increase,resulting in the increase of deposition rate and denudation rate,and the change of blade surface profile is more obvious.In addition,different types of salt only affect the supersaturation concentration of salt in steam,which mainly affects the deposition position of salting out particles,but has little effect on the changes of deposition rate,denudation rate and salting out layer thickness.