Research On The Characteristics Of Corona Discharge And Its Application To Heat Transfer Enhancement At Atmospheric Pressure

Corona discharge is a stable discharge phenomenon formed by ionization of gas molecules in non-uniform electric field.As an interdiscipline of fluid mechanics and classical electromagnetic field theory,electrohydrodynamics(EHD)mainly studies the coupling of electric field and other physical fields,such as flow field and temperature field.The flow and heat transfer problems generated from corona discharge are important research topics of EHD.In this paper,the corona discharge characteristics of pin-to-ring electrode structure and its application of heat transfer enhancement are studied.First,a set of experimental system was built to measure the volt-ampere characteristics,flow characteristics,and temperature distribution measurement respectively.The reliability of the experimental system was verified by measuring the electrical characteristics and the flow field structure of the classical pin-to-plate electrode structure.The current-voltage relationship and the flow characteristics of ionic wind as well as its heat transfer enhancement characteristics of pin-to-ring electrode were studied,and the heat transfer enhancement performance of ionic wind system was also evaluated.The experimental results show that the electrode distance has little effect on the volt-ampere characteristics of the pin-to-ring structure.In addition,the ionic wind generated by the positive corona discharge is more effective than the negative corona discharge,which leads to a better heat transfer enhancement effect.For example,when the electrode distance is 25 mm,the maximum velocity of ionic wind is 2.47 m/s with+15 k V,while the velocity at–15 k V is 2.03 m/s.It was found that the average Nusselt number on the surface of copper plate was significantly increased by the introduction of ionic wind,indicating that the heat transfer enhancement ability was significantly improved.At the same time,the whole ionic wind system has very low power consumption,showing great economic performance.Secondly,a fast numerical simulation model for ionic wind based on single charge coupled with experimental measurement of current-voltage data was established.The correctness of the established model is verified by comparing the numerical simulation results with the experimental results.In addition,the influence of different heat flux on the heat transfer enhancement effect of ionic wind was studied based on the numerical model.The simulation results show that the effect of ionic wind on the heat dissipation of the heated copper plate with high heat flux is more significant.For example,the temperature distribution on the surface of heated copper plate decreases from 495 K to 380 K with+15 k V when the heat flux is2.0W/m~2.Finally,the structure of the ionic wind generator was designed and optimized to improve the heat transfer effect and reduce the energy consumption.The experimental results show that the auxiliary electrode can effectively reduce the input voltage without reducing the ionic wind action range.In addition,the combination of the ionic wind and the fins can greatly improve the h eat transfer enhancement effect of the whole system without increasing the power consumption.Furthermore,using needle array and reducing the curvature of the needle tip can also effectively improve the heat transfer effect.These innovative designs provi de optimization ideas for further improving the efficiency of the ionic wind generator.