Research On Diagnosis Of OH Radical Produced By Pin-to-Water Atmospheric Plasma In Air

OH is one of the important products of gas-liquid plasma.It is also a very important oxidant with extremely high oxidation potential.It plays an irreplaceable role in biological medicine,sewage treatment,material preparation and so on.But the generation mechanism of OH in gas-liquid discharge is not clear.In order to efficiently and selectively utilize the high activity of OH and realize some novel plasma applications,it is important to quantitatively study the production of OH and their key generation mechanisms Due to the short life span of OH(ns to ?s)and the complicated gas-liquid discharge process,stringent requirements are put forward for both experimental diagnosis and simulation.This paper takes the pin-to-water electrode atmospheric pressure air glow discharge as the research object,based on broadband ultraviolet absorption spectroscopy(BB-UVAS)and laser-induced fluorescence spectroscopy(LIF),a novel and accurate diagnosis method for OH is developed,and the OH produced in the area where close to the liquid surface is determined.The absolute density of OH in the area close to liquid surface and its spatial distribution trend,and the influence of discharge parameters on OH production and the internal mechanism are studied.The main achievements of this paper are as follows:(1)Based on the Beer-Lambert's law,a simulation model of the broadband(306-312nm)absorption spectrum of OH was constructed.The OH density,gas temperature,and the spatial distribution profile of the two were used as input parameters,then the simulation can calculate the OH(AX,0-0)band;(2)The absorption spectra of OH are obtained by BB-UVAS measurement;the spatial distribution of the relative density of OH are determined by LIF measurement;the gas temperature spatial distribution in the discharge area is determined by the Rayleigh scattering method,based on these key information,the BB-UVAS band is simulated and fitted with the experimental results,and the absolute density of OH is determined by the iterative method.(3)The production of OH at different discharge current,different discharge interval,different solution conductivity,different power source polarity,and different regions of the plasma are studied;the results shows that under the same conditions,the peak density of OH generated by discharge when the pin electrode is negative is about 40%-60% of that of the positive polarity.,but its spatial distribution is wider;the OH density in the positive column area of the positive discharge is about 20%-25% of the area immediately adjacent to the liquid surface.The amount of OH produced is sensitive to the discharge current and distance;when the pin electrode is negative,the output of OH gradually increases with the increase of conductivity;under discharge with the negative pin electrode,the effect of solution conductivity on OH production is not obvious when the conductivity is greater than 200?S/cm.The work in this paper provides a reliable method for accurately diagnosing the absolute density of OH and their spatial distribution behavior in a complex gas composition environment.Based on this,the influence of different working parameters on the OH generation in the typical gas-liquid two-phase discharge region is obtained,which is important for further study.The study provides a new method for the gas-liquid two-phase discharge interaction process.