Study On The Combustion Characteristics Of Methane Laminar Flow Diffusion Under The Different Atmospheres

Energy,as a medium to promote the rapid development of society,is gradually optimized in the face of opportunities and challenges,in order to obtain as much energy and as possible while emitting less controllable pollutants.Natural gas,as an easy-to-obtain,low-polluting clean energy source,is mainly composed of methane,so the combustion characteristics of methane can represent the properties of natural gas.In this paper,we use laminar diffusion combustion,with the help of ANSYS Fluent simulation software,using the laminar finite rate model and GRI-Mech 3.0 mechanism to simulate our flames,and the simulation model used is compared with the experimental and numerical simulation results of Bennett et al.The combustion of CH₄under the different ratios of O₂/N₂,O₂/CO₂ and O₂/H₂O atmospheres was studied,and the flame shape,the emission characteristics of gaseous pollutants and solid pollutants produced were explored of CH₄ combustion under the different atmospheres.The results show that with the increase of the contents of N_2,CO₂ and H₂O under the atmosphere,the flame temperature gradually decreases,the thermal decomposition time of CH₄ and the flame height becomes shorter,and the radial velocity of the flame decreases.The generation of OH and H radicals is reduced.In the O₂/N₂ combustion atmosphere,with the increase of O₂ content in the atmosphere,the amount of NOx pollutants first increased and then decreased.The soot precursor C₂H₂ in the flame is consumed by OH,which promotes the oxidation of soot particles and reduces soot pollution.The increase of O₂ content under the combustion atmosphere is beneficial to improve the combustion efficiency of CH₄ and reduce the controllable pollutants.In the O₂/CO₂ combustion atmosphere,CO₂ has a certain inhibitory effect on the cracking of CH₄,reducing the emission of CO₂ in the combustion process and inhibiting the greenhouse phenomenon.At the same time,because CO₂ consumes a large amount of H radicals,the production of C₂H₂ in the flame is reduced,and the amount of soot generation is reduced.Under the O₂/H₂O combustion atmosphere,the enrichment of H₂O promotes the generation of OH radicals,and has a certain inhibitory effect on the generation of H radicals.As a result,the combustion rate of CH₄ is slowed down,the formation of C₂H₂ components is limited,the oxidation rate of soot particles is accelerated,and the overall emission of soot particles is reduced.Comprehensive comparison of the effects of different ratios of O₂/N₂,O₂/CO₂ and O₂/H₂O atmospheres on the combustion characteristics of CH₄.The effects of different ratios of O₂/N₂,O₂/CO₂ and O₂/H₂O atmospheres on the combustion characteristics of CH₄ were comprehensively compared.The flame temperature of CH₄ decreased the fastest with the increase of H₂O content under the combustion atmosphere,followed by the CO₂/O₂atmosphere,and the slowest under the O₂/N₂ atmosphere.As the proportion of O₂ under the combustion atmosphere decreases,the CO₂ emissions in the flame all decrease.The specific decreasing amplitudes are ranked from high to low in the order of O₂/CO₂,O₂/N₂ and O₂/H₂O atmosphere groups.The variation range of soot emissions is ranked as O₂/CO₂,O₂/H₂O and O₂/N₂ atmosphere groups from high to low.