基于背景纹影技术的长空气间隙放电通道温度场测量

长空气间隙放电发展过程中伴随有介质热电离现象,准确获取温度场有助于深度分析间隙放电特性,背景纹影技术突破了传统纹影技术中透镜组镜面尺寸的限制,可获得大尺寸放电通道的温度分布特性。文中搭建了背景纹影测量系统,采集了放电发展过程中的背景斑点图集,利用PIV粒子图像测速技术分析得到了穿过放电通道的光线偏移量;基于Abel逆变换计算得到了光线偏移量对应的折射率,再根据热力学方程和理想气体状态方程定量重构出密度场和温度场,并以酒精灯火焰为参照物进行了温度校验,分析结果与热电偶实测结果基本一致。以1m棒–板空气间隙为研究对象,通过搭建的背景纹影实体测量系统观测间隙正极性放电发展过程,分析了放电通道温度的时空变化规律,结果表明间隙中部横截面温度分布在1 200 K左右,温度场呈轴对称分布且离通道中心越近温度梯度越大,整个通道温度自棒极而下逐渐降低。

Temperature Field Measurement of Long Air Gap Discharge Channel Based on Background Oriented Schlieren Technology

The development process of long air gap discharge is accompanied by the phenomenon of dielectric thermal ionization. Accurate temperature field acquisition is conducive to the in-depth analysis of gap discharge characteristics. The background oriented schlieren(BOS) breaks through the limitation of lens size in traditional schlieren technology and can obtain the temperature distribution characteristics of large-scale discharge channels. In this paper, the background oriented schlieren measurement system is built, the background spot atlas in the development of discharge is collected, and the ray offset through the discharge channel is analyzed by PIV particle image velocimetry technology;the refractive index corresponding to the ray offset is calculated based on Abel inverse transformation, and then the density field and temperature field are reconstructed quantitatively according to the thermodynamic equation and ideal gas state equation. The temperature calibration of alcohol lamp flame is carried out, and the analysis results are basically consistent with the measured results of thermocouple. A 1 m rod plate air gap is taken as the research object, through the background schlieren measurement system, the development process of gap positive discharge is observed, and the temporal and spatial variation law of discharge channel temperature is analyzed. The results show that the temperature distribution of the cross section in the middle of the gap is about 1 200 K, and the temperature field is axisymmetric. The closer the channel is to the center, the greater the temperature gradient will be, and the temperature of the whole channel decreases gradually from the pole.