航空电磁超材料雷电冲击放电特性

Lightning Impulse Discharge Characteristics of Aeroelectromagnetic Metamaterials

随着航空电磁超材料在飞行器雷达天线罩的推广使用,其雷电防护问题亟待解决。针对方框型电磁超材料,使用冲击电压发生器、高速摄像机、普通摄像机,针对电磁超材料板的U50%冲击电压及放电路径开展试验,研究不同接地方式、不同电压极性的组合间隙及沿面放电特性。试验结果表明:方框型超材料沿面放电形貌受正、负极性电压的影响不大,表现为不规则的折线形放电路径,放电主通道并不唯一,同时存在流向另一接地位置的次级放电通道,越靠近放电附着点区域,次级放电通道越多,整个沿面放电形貌呈网状分布;雷电冲击电压下存在多条沿面主放电通路,组合间隙击穿前电磁超材料表面会产生沿面自放电通路,其沿面自放电通路为最终沿面主放电通路之一;组合间隙冲击放电流注发展过程的放电特性主要与电压极性相关,正极性冲击电压下由高压棒电极产生向下发展的下行流注,电磁超材料表面只有较弱的起晕;负极性冲击电压下分别产生对向发展的上、下行流注;雷电冲击电压下电磁超材料表面大量金属微结构单元阵列会产生上行流注和沿面自放电通路,其容易将雷电主放电通道引向超材料天线罩,导致分流条屏蔽失效。

With the popularization and application of aeronautical electromagnetic metamaterials in aircraft radome,the problem of lightning protection needs to be solved urgently.In this paper,the impulse voltage generator,high-speed video and ordinary camera were used to test the U50%impulse voltage and discharge path of the block-shaped electromagnetic metamaterial plate,and the combined gap and surface discharge characteristics of different grounding modes and voltage polarities are studied.The experimental results show that the surface discharge morphology of the block-shaped met-amaterials is not affected by the polarity of the voltages,which shows an irregular broken line discharge path,and the main discharge channel is not unique.There are secondary discharge channels flowing to another grounding position.More secondary discharge channels are generated when it is closer to the discharge attachment point,and the whole sur-face discharge morphology is distributed in a network.There are many main discharge paths along the surface under lightning impulse voltage.Before combined gap breakdown,the surface of electromagnetic metamaterial will produce self-discharge path along the surface,which is one of the final main discharge paths along the surface.The lightning im-pulse discharge characteristics of the development process of combined gap are mainly related to the voltage polarity.Under the positive impulse voltage,the downward streamer is generated by the high voltage rod electrode,and there is only weak corona discharge on the surface of electromagnetic metamaterial.Under the negative impulse voltage,there are opposite upward and downward streamers,respectively.Under lightning impulse voltage,lots of metal microstructure unit arrays on the surface of electromagnetic metamaterials will produce up-streamers and surface self-discharge paths,which is easy to lead the main lightning discharge channel to the metamaterial radome,resulting in the shielding failure of splitter bar.