Study On The Change Of Plasma Composition In Gas-liquid Mixed Phase

Plasma has attracted more and more attention from researchers in the fields of public health and environmental protection because of its rich constituent particles and strong chemical activity.Plasma devices and equipment using air,oxygen,etc.as carrier gases are beginning to show their heads in medical sterilization and disinfection and industrial wastewater treatment.However,in most of the practical applications of plasma in sterilization and pollution control,the effective chemical active species of plasma are single and the reaction efficiency is not high,which greatly limits the actual effect of plasma sterilization and pollution control.Therefore,the thin active ingredients and low effective concentration have become the main problems affecting their efficient application.In view of the above problems,the method and process of producing gas-liquid two-phase mixture and the effect of introducing plasma on the composition and state of plasma are studied in this paper.Aiming at this research idea,Dielectric Barrier Discharge(DBD)plasma excitation is combined with the saturated sodium bicarbonate boiling tube to produce the gas-liquid two-phase mixture in the boiling process.The phase transition process of the gas-liquid two-phase mixture and its influence on the plasma state are studied.First,the saturated sodium bicarbonate boiling process under the excitation of atmospheric pressure plasma is studied,focusing on the DBD discharge and bubble evolution in the boiling tube and the influence of its critical state on the generation of gas-liquid mixture.Second,the influence of the injection of gas-liquid two-phase mixture on the target plasma is studied,focusing on the types of plasma active species and the changes of plasma density and production ranges in the process of introduction.finally,for the discharge capacitive loads and needle-like capacitive loads,a matching differential power supply was designed to provide solutions for the generation of target plasma.Aiming at the generation of effective components such as hydroxyl radical(OH),highly active N and O in the target plasma,a simple dual-electrode DBD plasma heating and gas-liquid introduction device is designed in this paper.Compared with the way in which the target plasma directly contacts the liquid,this combined plasma excitation structure is more flexible and simple in control,and the reaction efficiency is higher.In the study on the heating and vaporization of saturated Na HCO₃in the boiling tube,we found that:the heat transfer involved in the bubble dominance and the positive feedback effect of DBD in the boiling process accelerate the gas-liquid mixture process of generation and injection,and the maximum injection speed can reach 4000 mm/s;The spectral diagnosis and schlieren diagnosis methods were used to characterize the change of the target plasma density,range and composition of highly active species after the introduction of the gas-liquid two-phase mixture.The diagnosis results show that the electron density of the target plasma center decreases by about 38%compared with that before the introduction,and the maximum width of the target plasma center is about 4 times the original;the intensity of the OH emission spectrum with a wavelength of 306-312 nm reaches twice the level before the introduction,There are two significant growth peaks in the N₂Second positive(C-B)system(N₂SPS)region at 320-360 nm.At the active O position of 777.2 nm,the spectral emission intensity is 8times before the introduction.The above research results validate the assumption that the introduction of the target plasma into the gas-liquid two-phase mixture can change the species and intensity of its chemically active species.This provides ideas and references for the problem of single chemically active species in the plasma and low reaction efficiency.