Study On Characteristics Of Air-Mist Jets Of Secondary Cooling Of Continuous Casting

The continuous casting process plays an important role on the casting quality, thefirst step of research is to find a reasonable way of cooling. With the advantages ofuniform and adjustable cooling effect, spray cooling received more and more attentionthan other cooling modes and used in almost environments for high heat flux removal.In this article, we designed the secondary cooling test system and the purpose wasto get the characteristic of the water flow density, droplet size, impact velocity as wellas the relationship between the Sauter mean diameter and dimensionless numbers.These results can be used to correct water spraying system for the secondary coolingregion of slab continuous casting of heat transfer，and secondary cooling scheme，andnozzle array arrangement.In this study we found the change rule of the air flow and water flow with thepressure. When we keep the air pressure for a certain value, air flow decreased withincreasing water pressure, but the water flow is contrary. On the other hand, when wemake the water pressure unchanged, the air flow will increase with increasing airpressure, at the same time, water flow will reduce.We can get the velocity filed of the jet according to the particle image velocimetry(PIV). Velocity obtained different working conditions in the air pressure0.20~0.40MPaand the water pressure is0.40MPa. The result of the experiment is that the velocities ofjet droplet increase with invariant water pressure and increased air pressure. When theinjection pressure under the condition of a constant, the velocities of jet droplet willincrease firstly and then reduce with increasing spray distance.In this study we used the oil film method for measuring the droplet size. Byanalysis, the number of the droplet whose diameter smaller than60μm is more than55%. The value of droplet diameter in the jet center area is greater than the marginalzone, but the distribution of droplet at the optimum diameter is contrary. In same waterpressure, the Sauter mean diameter will decreases with the air pressure increase andmore Weber number of the nozzle orifice more Sauter mean diameter.We found the correlation between the Sauter mean diameter through dimensionalanalysis, the Weber number and Reynolds number of nozzle orifice and thedimensionless distance. Standard error is0.0016.