Experimental And Simulation Study On The Characteristic Of Streamer Discharge For Air-GFRP Dielectric Laminate Combined Gap

The puncture damage of wind turbine blades is the most common damage pattern due to the lightning direct stricke.The breakdown of the wind turbine blade composite laminate depends on the combined effect of the environmental electric field and the electric field induced by the streamer discharge space charge.When linghtning strikes the wind turbine blade,in order to clarify the breakdown mechanism and physical process of the blade composites,and explain the formation of the lightning puncture damage,it is first necessary to study and grasp the discharge breakdown mechanism of the air-GFRP composite laminate combined gap.This research first established an observation platform for the development of streamer discharge in the air-GFRP dielectric laminate combined gap.The experimental research on the streamer discharge characteristics of the combined gap was carried out,and the discharge optical images and experimental waveforms of the "surface streamer discharge" and "penetrate streamer discharge" were obtained.The influence of the voltage amplitude and the thickness of the dielectric laminate on the discharge length of the surface streamer,the initial voltage of the first streamer on the needle electrode and the formation delay of the streamer below the dielectric laminate were analyzed.The results show that the larger the applied voltage amplitude is,the longer the surface streamer distance along the surface is.The thicker the dielectric laminate is,the longer the formation time of the streamer below the dielectric laminate is.Then,a numerical simulation model for the streamer discharge of the air-GFRP dielectric laminate combined gap was established considering the particle transport process inside the air and composite materials and the continuous current at the gas-solid interface,in which the Helmoholtz partial differential equation method is used to solve the photoionization source term in the particle continuity equation fast and efficiently.The coupling solution relationship of the control equations in the simulation calculation model was clarified,and the appropriate meshing strategy and solver settings are adopted to solve the tightly coupled multiphysics problem.The observed phenomenon of the combined gap discharge experiment is basically consistent with the simulation results of the model in this research.The experimental measurement value of the surface streamer length along the surface are compared with the simulation results,which verifies the Accuracy and applicability of the model established in this research for analyzing the streamer discharge process in the air-GFRP dielectric laminate combined gap.Finally,the simulation model is used to explain the experimental phenomena and conclusions of streamer discharge in combined gap.Through the simulation model,the discharge characteristics of the " surface streamer discharge " and " penetrate streamer discharge " in the combined gap were studied,and the distribution characteristics and evolution laws of the space charge and the space electric field during the streamer discharge process were obtained.The evolution process of the electric field inside the dielectric laminate and its relationship with the streamer discharge stage were obtained.The reason of electric field variation inside the dielectric laminate was explained.The influence of the voltage amplitude,the dielectric constant of the composite and the thickness of the dielectric laminate on the change of the electric field inside the dielectric laminate during the discharge process of the "through streamer" was acquired.