直流电弧热喷涂等离子体偏离局域热力学平衡态分析

Analysis of deviations from local thermal equilibrium in thermal spray plasma jet generated by a DC torch

在大气压力下,利用直流电弧放电产生热喷涂等离子体,采用发射光谱和热焓探针对热等离子体的射流特性进行诊断.文中通过使用氩原子两条特征谱线的辐射强度,采用双谱线相对辐射强度比值法来计算等离子体的电子温度;同时使用焓探针测量等离子体射流的焓值来计算得到气体温度.研究不同氩气流量和电流强度下,热等离子体的气体温度与射流中电子温度的演变情况,并对两者温度差值出现的原因及变化情况进行分析.结果表明,相同条件下发射光谱法测量的电子温度始终高于焓探针测量的等离子体温度,热喷涂等离子体在一定程度上偏离局域热力学平衡态.

A direct current atmospheric plasma spray torch was operated at different power levels and flow rates of argon plasma gas. The characteristic of the plasma jet was studied by using optical emission spectroscopy and enthalpy probe. In this paper,the intensity ratio of Ar atom spectrum lines was used to estimate the electron excited temperature of the thermal plasma jets,at the same time the temperature of the thermal plasma jet was determined using enthalpy probe. The temperature difference between them was investigated with the changes of current intensity and Ar flow rate. The results show that the electron temperature from emission spectroscopy measurements is always higher than the temperature of the plasma jet from enthalpy probe measurements under the same condition,and deviations from local thermal equilibrium exist in the plasma spray jets. Finally,nonequilibrium characterization of such turbulent thermal plasma jets was analyzed.