声脉冲法空间电荷测量系统的研究

气体中空间电荷的分布与电晕放电的机理紧密相关, 获取电晕放电过程中空间电荷分布对深入研究电晕放电起始、自持过程有着重要作用, 但是如何准确获得电晕放电过程中的空间电荷分布一直是国际上尚未解决的难题. 本文基于声脉冲法提出一种电场信号解耦算法, 推导了空间电荷在声场中被调制产生的电场信号与声脉冲信号和空间电荷密度之间的数值关系, 讨论了不同测量情况下声发射系统的设计要求; 搭建了一套可用于实时测量针板电极电晕放电空间电荷分布的非接触式测量系统, 该系统主要包括声脉冲发生模块、空间电荷模块及电场信号解耦算法模块. 运用该系统实现了声脉冲激发作用下电场信号的测量, 通过提出的电场信号解耦算法得到了空间电荷密度, 对其测量结果与电晕电流法测量结果进行比较, 验证了电场信号解耦算法的有效性. 该算法可以应用于空间电荷一维、二维和三维测量系统中.

Measurement of space charges in air based on sound pulse method

The space charge in air is closely related to the mechanism of corona discharge. In order to study the onset and sustainability of corona discharge, acquiring the distribution of space charge is necessary but there still exists a puzzle which has not been settled. According to the sound pulse method, in this paper we present a kind of signal processing algorithm to analyze the electric field which is generated by modulating the space charge in the sound field. The electric filed is dependent on the form of sound emission and space charge density. The waveform of electric field is related to space charge density. Through the proposed algorithm, the space charge density can be obtained by analyzing electric field signal. The area in which the space charges need to be measured, is divided into elements. Each element is small enough so that the space charge quantity in each element is assumed to be the same. The following assumption is accepted during numerical simulation: space charge densities in the wave fronts are the same. The curve of electric field produced, received by electric field antenna, is the vector sum of electric filed produced by each element, and then calculated by numerical simulation. In order to satisfy the assumption in each measurement case, the requirements for sound emission system under different cases are discussed. In different cases, different sound emission systems are required. For space charges which are distributed uniformly, plane wave or spherical wave is suitable; for one-dimensional space charge distribution, plane wave is necessary; for space charge two-dimensional or three-dimensional space charge distribution, plane wave array is availed. What is more, a corresponding measuring system is developed which can be used for measuring the space charge density. This system mainly contains the producing of sound pulse, producing of space charges and the receiving of electric field signal. The producing of sound pulse is designed according to the measurement requirement for multi-needle-to-plate geometry which is assumed that space charge is distributed uniformly in the gap. With the experimental model, the space charge density in multi-needle-to-plate geometry is calculated according to the algorithm proposed in this paper. The result is compared with the calculated one by the method of corona currents, verifying the proposed method.