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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10mm处,氧气的摩尔分数仍在90%以上.
By comparing the plasma flow field generated by two different structural cutting torches, it was found that the shielding gas had little effect on the temperature and velocity distribution of the plasma. The vertical shielding gas obstructed the torch nozzle and caused a pressure build-up in the torch But the increase is insignificant.Effects of the two kinds of structure protective gas on the cutting arc are only near the shock wave outside the torch nozzle.The intensity of the shock wave will be weakened after the protective gas is added.As compared with the case of no protective gas, Cooling effect, the arc voltage will rise slightly.When changing the composition of the protective gas, it is found that the oxygen content in the arc column area is not affected, so the changes of the protective gas composition will not affect the arc voltage.It is found that the oxygen at the axis and the surrounding Mixture of gas is very small, 10mm downstream of the nozzle, the oxygen mole fraction is still above 90%.