Research On Characteristics Of Iron Oxide Particle Erosion In Govering Stage Of A Supercritical Steam Turbine

The demand for electricity power has also increased with the rapid growth of Chinese industry.The thermal power unit of supercritical and ultra supercritical parameters have now become the development target of 600 MW and 1000 MW new unit because of its good economic advantages.With the improvement of the initial steam temperature of supercritical and ultra supercritical units,the high temperature oxidation process of the inner wall of the boiler superheater and reheater aggravates.Scales flaking away from the inner wall of boiler super-heater and reheater are carried to steam turbine by high-speed main steam caused serious erosion to the turbine governing stage and reheat first stage,and the economical efficiency of the supercritical and ultra supercritical units is reduced.Therefore,it is of great practical significance to improve the anti erosion performance of the blade by the study of the erosion of the solid particles of the blade.In this paper,by the CFD numerical simulation software ANSYS-CFX that the finite volume method based on finite element method is used to solve the time averaged Navier-Stokes equation.The trajectory tracking of solid particles in the blade passage used the solid particle transport model which is based on the Lagrange method which is only effective for the dilute phase flow.The erosion behavior of solid particles on the surface of the blade is calculated by Finnie erosion model.First and forefost,the particle motion characteristics and erosion characteristics in govering stage are analyzed in this paper.The study of the particle motion characteristics and erosion characteristics in govering stage shows that:with the increase of the particle size,the impact velocity declines gradually on stator and rotor pressure surface,while the impact angle increases gradually with the increase of the particle size on stator and rotor pressure surface.The critical size of particle in the nozzle is in the range of 15-25?m,while the critical size of particle in the rotor blade is in the range of 50-75?m.At the rotation speed 3000 rpm,the eroded area on the rotor pressure surface has obvious upward trend because of centrifugal force and the radial migration quantity is about 7% of blade height.Compared to nozzle,the maximum erosion rate density on rotor blade is 1.9 times of the rate on nozzle.Besides the particle motion characteristics and erosion characteristics in govering stage with oblique stator in different oblique angle of different loads such as 100%?75% and 50% are analyzed in this paper.Finally but not least the static pressure coefficient distribution of stator and rotor along blade and stage efficiency at 100% load are also analyzed in this paper.Thestudy of the particle motion characteristics and erosion characteristics in govering stage with oblique stator in different oblique angle of different loads such as 100%?75% and 50% shows that:in governing stage with oblique stator,with the increase of oblique angle,the impact velocity declines gradually on stator and rotor pressure surface.The maximum erosion rate density of stator pressure surface declines gradually with the increase of oblique angle.On the contrary,the maximum erosion rate density of rotor pressure surface increases gradually with the increase of oblique angle.On the same oblique angle,the impact velocity increases gradually with the decrease of load.The impact angle on rotor pressure surface declines gradually with the increase of oblique angle.The change in load has almost no effect on the impact angle.The stator is oblique or not has no effect on the static pressure coefficient distribution of stator androtor along blade profile.With the increase of oblique angle,reaction degree of stage increases,while the stage efficiency decreases.