非稳态浇铸对结晶器卷渣定量影响的大涡模拟

 基于实际板坯连铸结晶器建立了耦合大涡模拟(LES)湍流模型和VOF多相流模型的三维数值模拟模型,讨论了不同结晶器浸入水口(SEN)结瘤程度和SEN未对中分布对结晶器内瞬态多相流场及卷渣行为的影响。通过用户自定义程序成功实现了不同工况下结晶器内卷入渣滴数量、大小、空间分布等信息的定量化预测,并得到了弯月面不同位置处发生卷渣的概率分布。结果表明,水口顺时针旋转5°的未对中分布下由于钢液射流更多地撞击宽面,导致弯月面近窄面处液位分布有轻微降低,液位波动也从理想状态下的±(6~7) mm降低至±5 mm以内。SEN结瘤对弯月面液位波动有较大影响,SEN左侧完全堵塞、右侧未堵塞情况下液位波动增大至±11 mm左右,而SEN左侧堵塞2/3且右侧堵塞1/3情况下弯月面液位波动则增大至±15 mm左右。理想工况下净卷渣速率为0.0130 kg/s,卷渣主要发生在弯月面四周以及流股碰撞处。SEN未对中布置工况下净卷渣速率轻微降低至0.009 3 kg/s,但宽面附近卷渣概率明显增大。SEN左侧完全堵塞且右侧未堵塞和SEN左侧堵塞2/3且右侧堵塞1/3情况下净卷渣速率则分别增大至0.045 5 kg/s和0.0670 kg/s;卷渣主要由过大的钢液流速对弯月面的剪切作用造成,且主要位于水口至1/4结晶器宽度的范围内。水口结瘤后不对称流动造成的旋涡增加,由此引起的卷渣也相应增加。

Large eddy simulation on quantitative influence of unsteady casting on mold slag entrainment

A three-dimensional numerical model coupled with the large eddy simulation (LES) turbulence model and VOF multiphase model, was established based on an actual slab continuous casting mold to investigate the influence of clogging degree and misalignment distribution of submerged entry nozzle (SEN) on the transient multiphase flow field and slag entrainment. The quantitative prediction of number, size, and spatial distribution of the entrained slag droplet in the mold under different conditions were successfully realized using a user defined function,and the distribution of the probability of the slag entrainment at the meniscus was proposed. The results indicate that under the misalignment distribution of the SEN rotating 5° clockwise, the liquid steel jet hit the wide surface more, resulting in a slight decrease in the liquid level distribution near the narrow surface of the meniscus, and the liquid level fluctuation also decreases from the ±(6-7) mm to within ±5 mm compared with the normal conditions. The SEN clogging had a significant effect on the liquid level fluctuation. The liquid level fluctuation was increased to about ±11 mm when the SEN was completely clogging on the left side-without clogging on the right side, and the liquid level fluctuation was increased to ±15 mm when the SEN was 2/3 clogging on the left side-1/3 clogging on the right side. With the normal conditions, the net slag entrainment rate was 0.0130 kg/s and the slag entrainment was mainly occurred around the meniscus and where the stream collides. The net slag entrainment rate was slightly decreased to 0.009 3 kg/s and the probability of slag entrapment near the wide surface was increased under the SEN misalignment condition. The net slag entrainment rate was increased to 0.045 5 kg/s and 0.067 kg/s respectively when the SEN was completely clogging on the left side-without clogging on the right side and 2/3 clogging on the left side-1/3 clogging on the right side. The slag entrainment rate was mainly caused by the shearing effect of the excessive flow velocity of molten steel on the meniscus. The slag entrainment was mainly located within the range of the SEN to 1/4 the width of the mold. The vortex caused by the asymmetric flow was increased after the SEN was clogged, and the slag entrainment also increased accordingly.