Observation And Research On Thermal And Spatial Characteristics Of Leader Discharge In Long Air Gap

The change of temperature in the leader discharge channel plays important role in the generation and development of the leader.At the same time,different curvature radius of electrode also has different influence on the discharge process of leader,so it is of great significance to carry out quantitative research on the thermal characteristics of leader under different curvature radius of electrode.On the other hand,the spatial characteristics of the leader discharge process can provide the basis for the study of its physical mechanism,which also has important significance.Based on these,this paper has done the following two aspects of research.Firstly,the thermal parameters of the leader are quantitatively measured.By constructing the Mach-Zehnder interference system,the thermal parameter model of the leader channel is established based on the phenomenon that the interference fringes will distort due to the change of refractive index when interfered by the flow field.Using this model,the thermal characteristics of the positive leader under different electrode terminals in 1m air gap are analyzed quantitatively.The results show that with the decrease of the curvature radius,the temperature of the leader increases,the gas density decreases,and the thermal diameter increases.But the difference of thermal diameter is small,only within 2 mm.In addition,an analysis method for the spatial characteristics of the leader based on the path extraction is proposed.Firstly,according to the characteristics of captured discharge image in long gap,a path extraction method for multi branch discharge channel image in complex background is proposed,which can accurately obtain the single pixel path of discharge channel.Secondly,the spatial characteristics of leader in long gap,such as length and speed,can be obtained only by counting the number of pixels in the extracted discharge path and calibrating the actual length of one pixel.It avoids the problem of time-consuming and large error caused by the traditional method of segmenting the leader channel,then manually measuring the length of each straight segment and adding them.