Migrating Behavior Of Droplets In The Spray Zone Of Gas-water Atomizing Cooling In The Second Cooling Zone Of Continuous Casting

In the secondary cooling zone of continuous casting,the cooling strength acted on the high-temperature slab is affected by the renewal rate of the water vapor film on the strand surface,which is directly related to whether the spray droplets can effectively penetrate the interface of vapor film,and it is affected by the droplet velocity,particle size,droplet momentum and so on.These influence factors are closely related to the migration behavior of droplets in the spray zone of the secondary cooling zone.According to the actual structure and process conditions of the gas-water atomizing nozzle used in the secondary cooling zone,a mathematical model for the migration behavior of spray droplets in the secondary cooling zone was established in this paper.The influence of the droplet size,the droplet velocity at nozzle outlet,the spray height of nozzle and the gaswater ratio on the migration behavior and critical cooling characteristics of water droplets have been investigated.The main conclusions can be concluded as follows:(1)Water droplets were injected to the spray zone through a fan-shaped 110 ° slit at the nozzle outlet.In the spray center,the velocity of droplet is high,while the edge velocity is low.The velocity of spray droplets is attenuated when it migrates from the nozzle outlet to the surface of the slab.Some droplets leave the strand surface for collision.(2)With increase of the particle size of the droplet,the droplet velocity leaving the nozzle outlet is reduced,the migration range of the central section in the spray zone becomes wider,and the liquid phase distribution in the width direction of the slab is uneven.The vertical velocity of droplet decreases and the number of droplets reaching the critical plane decreases,but the sum of the momentum of all droplets in unit area increases.(3)The greater the velocity of spray droplets at the nozzle outlet,the wider the spread range of spray droplets in the width direction of the slab,the more uneven the liquid phase distribution on the surface of the slab,and the lower the velocity attenuation during the droplet migration process.With increase of the droplet velocity at the nozzle outlet,the resultant velocity and the vertical velocity of the droplet increase,and the droplet number reaching the critical plane and the total momentum of all droplets in unit area increase also.(4)Increasing the spray height of the nozzle,the difference of the liquid phase distribution on the slab surface is not obvious,the droplet velocity,the droplets number and the total momentum in unit area decrease.With the increase of the nozzle gas-towater ratio,the maximum liquid phase velocity at the nozzle outlet increases,the liquid phase on the slab surface increases and its distribution become wider,and the droplet velocity on the critical surface increases,the number and total momentum of droplets in unit area on the critical plane increases,and the uniformity of momentum distribution becomes better.