Study On Dynamic Characteristics Of Droplet Impacting On Wall In Corrugated Plate Dryer

The corrugated plate dryer plays a vital role in the steam generator.Its main function is to remove the tiny liquid droplets in the steam and ensure the steam dryness at the outlet of the steam generator,to improve the efficiency and safety of the nuclear power plant.In the corrugated plate dryer,the droplets impact on the wall of the dryer,and the behavior affects the separation efficiency of the dryer.Therefore,the study of droplets impacting on the wall is helpful to understand the mechanism of the droplets impacting on wall of the corrugated plate dryer,which provides a theoretical basis for the optimization of the dryer.The problem of droplet impact on the wall in dryer is very complex,including the multiple droplets impacting,droplets impacting on inclined walls and impacting on curved walls,and the related research is not complete.Based on this,this paper uses a combination of numerical simulation and experiment to analyze the droplet impacting on the wall.This paper analyzes the velocity field and pressure field of the droplet impacting on the liquid film by two-dimensional numerical simulation,and studies the influence of the We number and Re number on the impacting outcomes.The velocity field and pressure field of two droplets successively impacting and simultaneously impacting are analyzed,and the factors affecting the results are studied through a large number of cases.The study found that when the two droplets successively impact on liquid film,increasing the impact velocity,decreasing the thickness of the liquid film and increasing the distance between droplets are conducive to the splashing of the internal crown;and when two droplets simultaneously impact on liquid film,increasing the impact velocity,decreasing the thickness of the liquid film and decreasing the distance between the droplets are conducive to the splashing.High-speed photography and pixel analysis methods are used to study the single droplet impacting on an inclined wall,and various experimental outcomes of a single droplet impacting on inclined wall are analyzed.The analysis shows that the front spreading factor increases as the inclined angle increases,the We number increases,and the Oh number decreases.The back spreading factor increases as the inclined angle decreases,the We number increases,and the Oh number decreases.Spreading factor on the wetted wall is always greater than that the dry wall.Outcomes of droplet impacting at low velocity is analyzed,and the critical parameters of droplet splash are obtained.Experimental study on droplets impacting on the cylindrical wall was carried out,and the results shows that the spreading factor in the generatrix direction decreased with the increase of the curvature ratio,and decreased with the increase of Oh number,but the We number had little effect on the spreading factor.The spreading factor in directrix direction increases with the increase of curvature ratio,decreases with the increase of oh number,and increases with the increase of We number.Through a large number of experimental data,the critical parameter formula for the splashing caused by the droplet impacting on the cylindrical wall is obtained.Three-dimensional numerical simulation is used to study two droplets impacting on the inclined wall and cylindrical wall.The pressure of the neck at the initial moment of impacting is analyzed,and the pressure at the center area of the two droplet is studied.The relevant parameters of the central sheet and the particle diameter distribution of the secondary droplets have been studied.The analysis shows that when the two droplets simultaneously impact on the inclined wetted wall in the longitudinal direction,the width of the central sheet decreases with the increase of the inclination angle,and when in the transverse direction.The width of the central sheet increases with the increase of the inclination angle.When the two droplets simultaneously impact on the wetted cylindrical wall,the width and height of the central sheet decrease with the increase of the curvature ratio.The secondary droplets generated by the simultaneous impacting of two droplets conform to the normal distribution.As the inclined angle and curvature ratio increase,the number of droplets decreases,and the proportion of droplets with smaller diameters decreases.