火焰清理过程中射流合并对板坯表面质量的影响

Effect of multi-jet merging on the slab surface quality in the scarfing process Compressible fluidity of gas

随着钢坯表面质量的要求日益严格,火焰清理板坯表面沟痕问题备受瞩目。本文发展了一种三维数学模型来研究火焰清理机的气体流动规律和冲击特性,采用标准k-ε模型来模拟气体的可压缩流动,计算了预热阶段和清理阶段下不同的流场结构,揭示了火焰清理沟痕的产生机理,探讨了不同烧嘴结构对沟痕的影响,分析了清理沟痕的优化方法。结果表明:火焰清理沟痕主要是由平行多孔射流康达效应引起的,射流合并现象导致钢坯表面射流冲击强度不均,从而产生"垄沟"状清理沟痕;烧嘴结构显著影响沟痕分布,射流方向应与喷嘴出口端面垂直,导流板角度要适当,不宜使射流任意掺混也不宜抑制射流发展;喷嘴台阶高度主要影响冲击沟痕深度,而对分布规律影响较小。

With the increasingly stringent requirements for the slab surface quality,the scarfing groove problems have attracted tremendous attentions. A three-dimensional mathematical model has been built to study the compressible gas flow pattern and impinging characteristic. The standard k-ε turbulence model was used to simulate the compressible fluidity of gas. The different flow field structures under the preheating stage and the cleaning stage were investigated,and the inherent mechanism of scarfing groove generation was revealed. The optimization methods of scarfing groove were proposed by analyzing different nozzle structures. The results indicated that the scarfing grooves were mainly caused because of the Coanda effect of the parallel multiple jets. The multi-jet merging leads to the uneven impinging strength on the slab surface. As a result,the distribution of shear stresses on the slab surface presented like peaks and valleys,and therefore formed the scarfing grooves. The nozzle structure significantly affects the groove distributions.The jet direction is supposed to be perpendicular to the nozzle outlet and the deflector angle should not inhibit the development of the jet flow. The nozzle height mainly affects the scarfing depth,but has negligible influence on the groove distributions.