Needle-Matrix Bipolar Corona Discharge And Particulates Trapping Using The Novel Corona Discharge

This thesis has proposed a novel corona discharge,i.e.,the needle matrix bipolar corona discharge.The current-voltage characteristics of the multi-needle bipolar corona discharge have been obtained through detailed experiment and analysis,and the optimum electrode structure has been determined.Using optical emission spectrometry. the outline of the multi-needle bipolar corona discharge has been determined,and some important roles between the microscopic characteristics and the discharge current and the applied voltage have been obtained.The efficiency of particles trapping by the needle matrix bipolar corona discharge has been studied experimentally,and the reasons why this kind of corona discharge has a high efficiency of charging and trapping particles have been analyzed.Using this technology in cooking fume purification, high-temperature precipitation and soot trapping,the results of the tests show that this technology has advantages of high trapping efficiency and running reliability.Firstly,summarize all the normal methods for producing corona discharge,and point out that the injecting discharge energy in DC corona discharges is low.while pulse corona discharge has shortages of low power efficiency,negative magnifying effects and short lifetime of pulse elements.Then,introduce the status of researching corona discharge using OES.It is concluded that main researches focus on uniform corona discharge,there is few research on morphology determination of ionization region and the relationship with macro parameters,and especially there is no study of bipoplar corona discharge.Finally,summarize the main application research status of corona discharge in environmental pollution treatment,including particle trapping. desulfurization and denitrification,and VOCs degradation.All results show that the removal efficiency needs to be improved. and the main problems are low trapping efficiency of micro-particles,low denitrification efficiency and low degradation efficiency of some VOCs.Thus,it is necessary to combine with other purification technologies,and it is believed that both the discharge intensity and the running reliability should be improved in purification of polluted gases using corona discharge. A method for producing bipolar corona discharge in needle matrix electrode configuration is proposed.It is thought that this kind of discharge produce positive and negative discharges simultaneously;has large discharge current and high power density; and has long running stability,e.i..resolve the problem of dust accumulation on the discharge electrodes in unipolar corona discharge.The current-voltage characteristics of the multi-needle bipolar corona discharge are studied in detail.Through regulating the space between needles s,the space between electrodes d and the needle radius a,the curves of current-voltage have been analyzed experimentally.The reasons why this kind of corona discharge has larger discharge current and higher electron and ion densities are obtained.It is concluded that there exist positive ions and negative ions in the migration area simultaneously,and the combination between positive ions and negative ions is ignored.Through comparing the relationships between the discharge power density and s.d, or a,it is gotten to increase discharge power effectively.Meanwhile,considering the discharge stability,the optimum electrode structure of the bipolar corona discharge is determined.Based on the study of multi-needle to plate corona discharge using optical emission spectrum,the morphology of multi-needle bipolar corona discharge is determined.According to the distribution of N₂ second positive band's intensity I_SPB,the outline of the two ionization regions are drawn and the distribution of energetic electrons is obtained too.There is linear relationship between the sum of I_SPB and the discharge current I.Combined with the study of the current-voltage characteristics,the energetic electrons in the ionization regions and the ions in migration area are to form the discharge current in the multi-needle bipolar corona discharge respectively.According to the former conclusions,using the needle matrix bipolar corona discharge as a core technology,two sets of air cleaning devices are made.The experiments of particles trapping in one way and the test of air cleaning in a closed room have been conducted respectively.The effects of the wind velocity,the applied voltage and the diameters of particles on the trapping efficiency are studied experimentally.Comparing the efficiencies of trapping particles using needle matrix to plate discharge and needle matrix bipolar corona discharge,the fact is despited that these two discharges both have high efficiencies of trapping particles with large diameter,and the needle matrix bipolar corona has a higher efficiency of trapping particles with small diameter.Combined with the theory of particle charge,the reasons why the needle matrix bipolar corona discharge has high charge capacity and trapping efficiency is analyzed.Finally,using the needle matrix bipolar corona discharge as a core technology, several purification devices are made for applying in cooking fume purification. high-temperature precipitation and soot trapping.The removal efficiencies are investigated experimentally.The purification devices are characterized by high trapping efficiency of micro-particles,high running stability,simple structure and low manufacture cost.