直流升压条件下频率选择超材料流注放电特性

Analysis of Streamer Discharge Characteristics of a Frequency Selective Metamaterial under DC Step-up Condition

频率选择超材料是一种理想的雷达罩材料,但其雷电屏蔽失效率较高,制约了这种材料的工程化应用。本文制备两种典型结构频率选择超材料,基于雷击放电过程中目标物附近的电场变化,设计直流升压条件下的超材料流注放电试验方法,从放电形貌、击穿电压和电荷沉积三个方面,对比研究两种超材料的放电特性,分析两种超材料的电场分布情况。结果表明,谐振环型超材料的击穿电压最高,细丝状放电较暗且密集,靠近接地位置的细丝状放电较多;耶路撒冷型超材料的击穿电压最低,细丝状放电较亮且稀疏。进一步分析发现,细丝状放电导致带电粒子积累到蒙皮表面形成表面电荷,表面电荷密度达上百μC/m2,在蒙皮内部产生与外加电场同向的电场,数值达几十kV/cm,显著提高了蒙皮内部电场强度,蒙皮在外加电场和表面电荷的双重作用下发生击穿。希望研究结果能够为超材料的雷电防护提供参考。

Frequency selective metamaterial is an ideal radome material,but its lightning shield failure rate is high,which restricts the engineering application of this material.In this paper,two typical frequency selective metamaterials were prepared.Based on the change of electric field near the target during lightning discharge process,the test method of streamer discharge for metamaterials under DC step-up process was designed.Then,the discharge characteristics of these two metamaterials were studied from three aspects of discharge morphology,breakdown voltage and charge deposition.Furthermore,the electric field distributions of these two metamaterials were analyzed.The results show that,the ring resonator-type metamaterial has the highest breakdown voltage,the discharge filaments are darker and denser,and the discharge filaments near the ground are more.Meanwhile,Jerusalem-type metamaterial has the lowest breakdown voltage,the discharge filaments are brighter and sparser.Further analysis shows that the discharge filaments cause the charged particles accumulating on the skin surface to form surface charge.The surface charge density is hundreds ofμC/m2,and the electric field of several tens of kV/cm is generated inside the skin in the same direction as the applied electric field.Thus,the electric field strength inside the skin significantly increases,resulting in the breakdown of the skin under double effect of applied voltage and surface charge.The results provide theoretical reference for lightning protection on metamaterials.