Research On Electro-hydrodynamics And Heat And Mass Transportation Characteristics Of Multi-needle Electrode Ionic Wind Generator

The directional migration of gas media over solid walls and their participation in energy exchange are important processes for maintaining the proper functioning of equipment in industry and commerce as well as in the chemical industry.However,due to the large molecular spacing and small intermolecular forces of gases,the enhancement of their thermal mass transportation capacity during flow has always been a hot spot in academic research,and it is important to explore highly efficient heat and mass transfer controllable enhancement techniques based on gas media.Among the many techniques for enhanced heat and mass transfer,the multi-needle electrode ionic wind technology has received a lot of attention from researchers for its advantages of low energy consumption,high efficiency and without of moving parts.However,the diversity of electrode combinations and the single performance evaluation index of the ionic wind generator,as well as the fact that the overall performance of the generator and its influencing factors have not been clearly analyzed,have a negative impact on the application of ionic wind-based heat and mass transfer enhancement technology.Based on this,this paper investigates the electro-hydrodynamics and thermal mass transportation characteristics of the multi-needle electrode ionic wind generator from both experimental and numerical simulations,examines the heat and mass transfer performance and the multi-needle interference characteristics of the developed generator,and explores the generator optimization scheme.Firstly,to study the thermal mass transportation performance of the generator,an electric/thermal/flow physical field experimental platform has been built,and an attempt is made to measure the ionic wind mass flow rate using the heat transfer method,while the theoretical mass flow rate prediction equations is derived to compare with the experimental results.The results show that the needle electrode embedded structure of the generator can provide good heat transfer performance,and the maximum functional surface convection heat transfer coefficient can be improved by nearly 50% compared to the natural convection condition.Meanwhile,the generator gas transportation performance is strongest at the heat source condition of 40°C,which indicates that the temperature also affects the ionization excitation process of the device.In addition,due to the effect of the multi-needle arrangement,the generator mass flow rate remains consistent with the theoretical predictions under the one-row electrode arrangement,is enhanced under the two-row electrode arrangement,and decays under the three-row electrode arrangement.Secondly,to study the interference characteristics of multi-needle arrangement,a multineedle coupled discharging model is constructed and the EHD(Electro-hydrodynamics)force is proposed as a simulation indicator parameter.The results show that the multi-needle arrangement reduces the average electric field per needle,but increases the net negative charge in the discharging space.However,due to the interference among needles,the increment of net negative charge is not proportional to the increase in the number of needles.As a result,the EHD force per needle increases by about 45.8% for the two-needle arrangement and decays by about 38.1% for the three-needle arrangement under simulated conditions.This is also in contrast to the experimental ionic wind mass flow rate that is enhanced with a two-row arrangement and decays with a three-row arrangement.Finally,in order to attenuate the electrode interference and explore the electrode parameter optimization characteristics,a multi-needle discharging optimization model is developed and the EHD force is used as the objective function.The results show that optimization of electrode parameters helps to improve the generator transportation performance.Appropriate needle electrode spacing,plate electrode width,and needle electrode curvature radius result in less discharge interference,larger discharging space,and more uniform distribution of the discharging plasma jet,respectively,thus ensuring better performance of the generator.In summary,this paper has carried out corresponding experimental and simulation studies on ionic wind generator development,transportation performance testing methods and generator interference factors investigation and optimization,providing a theoretical basis and analytical means to clarify the factors that affecting the comprehensive performance of the generator as well as the evaluation index,which is conducive to promoting the application of enhanced heat and mass transfer technology based on ionic wind.