保护气对切割弧特性影响的模拟研究

通过比较两种不同结构切割炬所产生的等离子体流场,发现保护气对等离子体的温度和速度分布影响很小.垂直保护气在切割炬喷口形成阻碍作用,造成切割炬内的压强有所升高,但是增加不大.两种结构保护气对切割弧的影响只是在炬喷口外的激波附近.加入保护气后激波的强度会减弱.相对于没有保护气的情况,保护气增加冷却作用,弧电压会略有升高.当改变保护气的成分时,发现弧柱区的氧气含量不受影响,所以保护气成分的改变不会影响到弧电压.计算发现轴线处氧气和周围气体的混合很少,在喷口下游10mm处,氧气的摩尔分数仍在90%以上. 关键词： 等离子体切割弧 保护气 数值模拟

Numerical simulation on the effect of shielding gas on the plasma cutting arc

By comparing two diffierent torch geometries, it was found that the shielding flow has no significant effect on plasma velocity and temperature,except in the shock wave region. The shielding flow decreases the shock wave, and increases the arc voltage due to cooling. In the impinging geometry, shielding flow will crash the plasma jet after the nozzle exit and slightly increase the pressure in the torch. It was also shown that the component of shielding gas has no significant effect on plasma cuttingarc. The mole fraction of oxygen decreases very slowly along the axis and is still more than 90% at 10 mm downstream the nozzle exit.