大气感应耦合等离子体炬管的设计与仿真实验

Design and simulation experiment of an atmospheric inductively coupled plasma torch

为提高大气感应耦合等离子体射流加工装置的工作稳定性,设计一种依靠单一零件定位各层介质管的分体式炬管,并研究炬管内等离子体的传热与流动特性.利用COMSOL Multiphysics仿真分析发现,等离子体的环形加热和流体淤塞回流现象是导致炬管在使用后出现热损伤和刻蚀损伤的主要原因,选用陶瓷材料作为内管和中层管并调整感应线圈的位置,可有效延长炬管的使用寿命.使用CCD相机实时监控等离子体射流的形态,发现射频功率(Pw)、工作气流量(Q2)、冷却气流量(Q3)与射流的整体长度(L)和半高宽度(W)均呈线性递变关系,Pw、Q2与Q3的值过高或过低都会导致等离子体射流的形态波动增大.实验结果表明:当Pw、Q2与Q3分别设置为900~1 000 W、650 mL·min-1、16 L·min-1时,该分体式炬管可产生稳定性较高的等离子体射流,其L值与W值的波动可分别控制在0.50 mm与0.25 mm内,适用于熔石英等光学表面的加工.

To improve the stability of the atmospheric inductively coupled plasma(ICP)torch,a demountable ICP torch whose dielectric tubes were located by a special part was designed,and its heat transfer and flow characteristics were studied.Through the simulation by COMSOL Multiphysics,it is found that the annular heating and fluid backflow are the main reasons for thermal damage and etching damage of the torch.Therefore,the service life of the torch can be effectively improved by using ceramics as the material of the central and middle dielectric tubes and adjusting the position of the induction coil.In addition,the jet morphology was monitored by a CCD camera.It is found that the overall length(L)and the half-width(W)of the jet linearly changes with the radio frequency power(P w),the working gas flow(Q 2)and the cooling gas flow(Q 3).However,when the P w,Q 2 and Q 3 are too big or small,the fluctuation of the jet increases,the ICP jet will become unstable.The results show that when P w,Q 2 and Q 3 are set to 900-1000 W,650 mL·min-1 and 16 L·min-1 respectively,the demountable torch can generate stable ICP jet.The fluctuation of L and W can be controlled within 0.5 mm and 0.25 mm respectively,which is suitable for the processing of fused quartz and other optical surfaces.