Study On The Kinetic Of Dissociation And Oxidation Of Methane Activated By Non-equilibrium Plasma

Plasma-assisted combustion is a new combustion mode with good application prospects,it will be widely used in energy,transportation,environmental protection in the future.Reducing ignition delay time,improving flame stability,increasing flame propagation speed,low temperature combustion,extending ignition and extinction limit are all important issues of plasma-assisted combustion research.Researchers have done large amount of relevant work,and achieved fruitful results.However,due to the complexity of the interaction between plasma and flame,the detailed reaction kinetics is still not well understood.In particular,there is little research on the dissociation and oxidation process of gas mixture before plasma ignition,which is the accumulation stage of energy and active particles for ignition,so it is very important to the ignition process.The paper mainly studied this process.This paper used the method of simulation supplemented with experiment to study on the kinetic process of dissociation and oxidation of the mixture CH4/O2/He activated by non-equilibrium plasma produced in nanosecond pulse discharge(NSD)and radio frequency(RF)discharge.The main contents were as follows:(1)The reaction mechanism and electron collision cross section of CH4/O2/He were collected to calculate the electron energy distribution function(EEDF).Furthermore,the reaction rates were calculated.The thermodynamic data was collected and fitted to calculate energy and temperature in the reaction process.Using and improving chemical kinetics mechanism HP-Mech.(2)Dynamic model of nanosecond pulse discharge plasma was built.Plasma dynamics package ZDPlaskin and chemical reaction dynamics package Chemkin-?were used to calculate temperature,species concentrations and the rates of the elementary reaction.Drawing and analyzing the reaction path diagram.The effects of gas pressure,temperature and reduced electric field on the oxidation products and active particles were studied.(3)Dynamic model of RF discharge plasma was established,and the RF discharge experimental platform was built.Species concentrations and the rates of the elementary reaction in 30 w discharge power were calculated.Drawing and analyzing the reaction path diagram.The concentrations of important species produced in 30-100 w discharge power were measured by GC,which were then compared with the simulation results.The accuracy of the model was verified.(4)The two kind of discharge modes and their characteristics were compared and analyzed.The reaction paths in the two kinds of discharge modes were also compared,and the conclusion was drawn:In NSD,It was more focused on the oxidation process of methane,which had less reaction routes.And in RF discharge,it was easier to produce C2 species,which had more reaction routes.