Study On Corona Discharge Characteristics Of Short Air Gap Based On Plasma Chemistry Model

Natural thunderstorm activity generates strong electromagnetic field changes near the ground,which can cause corona discharge phenomena at high tip targets.The corona discharge process on the surface of the tip target generates a large amount of space charge around it,which affects the onset process of the upward piloting of the tip target.In order to study the microscopic physical process of corona discharge at the tip of lightning rod under the environment of thundercloud electric field and the influence of environmental factors on the corona discharge,this paper analyzes the change law of transport parameters of the discharge process,builds a mixed model of plasma chemistry and fluid dynamics of the air corona discharge process,simulates the head of the grounding electrode in the"plate-rod"air gap The physical process of corona discharge in the air gap of"plate-rod"is simulated,the influence of different factors on the corona discharge process of the head of the grounding rod is analyzed,and the shielding effect between the grounding electrodes is analyzed by the"plate-double rod"gap corona discharge test.The main research work of this paper is as follows:（1）The electron collision source term of Boltzmann equation is obtained by using two approximate theory and combining the available cross-sectional data of electron collision reactions.The electron energy distribution function is obtained and the electron transport parameters are calculated.The reasonableness of the considered electron collision reaction is verified by comparing the relevant literature.The effects of pressure and temperature on the electron transport parameters are also analyzed.The results show that the effect of pressure on the reduced ionization coefficient and reduced attachment coefficient is large,while the effect of temperature is small.（2）Numerical calculation model of"plate-rod"corona discharge is built.The spatial distribution of electric field strength,electron concentration,electron temperature and important heavy particle density during the corona discharge process,as well as the influence of air pressure,temperature and voltage on the corona discharge process were analyzed.With the development of the discharge,the electron concentration peaks are all at the head of the rod electrode,and the electric field strength,electron temperature,N₂⁺concentration and O₂⁺concentration peaks gradually move toward the plate electrode.The influence of air pressure and voltage on corona discharge is greater,and the discharge speed is gradually accelerated as the air pressure decreases and the voltage increases.The influence of temperature on corona discharge is smaller.（3）Three"plate-rod"and two"plate-double rods"grounding electrode corona discharge characteristics tests were conducted.Using a combined electric-optical observation test platform,the influence of head shape on the corona discharge characteristics and the shielding effect between the two ground electrodes in the"plate-double rods"gap.In the"plate-rod"gap,the voltage difference|U_smax-U_smin|of the streamer discharge phase of the conical ground electrode is significantly larger than that of the spherical（r=0.75cm）;for the glow corona of the conical ground electrode,the voltage difference|U_gmax-U_gmin|decreases with the increase of the gap distance,while that of the spherical（r=0.75cm）is basically the same.The voltage difference is basically the same at the spherical（r=0.75cm）,indicating that the streamer corona and glow corona phases are easy to occur at the grounding electrode with small curvature radius.In the"plate-double rods"gap,the corona onset voltage of the spherical（r=0.75cm）grounding electrode increased by about-30k V compared with the"plate-rod"gap,while the corona onset voltage of the conical grounding electrode remained the same.The pulse current amplitude decreases with increasing curvature radius;the photon number of each grounding electrode is obtained by image processing,and the photon number increases approximately linearly after corona onset,and the closer the grounding electrode is,the stronger the shielding effect.