The Inhibition Effect Of CH₄/CH₃OH On DME Cool Flames

As the proportion of oil and coal in the energy structure decreases year by year,the development of clean alternative energy has become the focus of current energy research.As the main component of natural gas,CH₄ has the advantages of abundant reserves,good economy and high calorific value,but in the actual use process,it shows some shortcomings such as high ignition delay time and slow flame propagation speed.DME has the advantages of excellent ignition performance and low particle emission.Adding DME to CH₄ can effectively improve the defects of CH₄.However,DME has the phenomenon of cool flame.If it is used in gas turbine or internal combustion engine,the cool flame will affect the hot flame ignition process.In recent years,some studies have found that CH₄ can inhibit the cool flame of DME,but further research is needed.In this paper,CH₃OH/DME as the contrast fuel,was used to compare with CH₄/DME to find the reason why DME cool flame was inhibited.First,the flame combustion characteristics of CH₄/DME blended fuel and CH₃OH/DME blended fuel,including extinction limits,flame temperature and combustion products distribution,were studied by means of a diffusion counterflow system.All these combustion characteristics show that CH₃OH and CH₄ promote the hot flame of blended fuel.When analyzing the reaction path,it was found that CH₄ and CH₃OH inhibited the flame reaction process of dimethyl ether to a certain extent because of the competition of H and OH radicals.Then,the cool flame combustion characteristics of CH₄/DME blended fuel and CH₃OH/DME blended fuel were studied,including extinction limits,flame temperature and combustion products distribution.These combustion characteristics all show the inhibitory effect of CH₄ and CH₃OH on DME cool flame.Chemical reaction path analysis was carried out to obtain the detailed mechanism of CH₄ and CH₃OH inhibiting DME cool flame combustion process.The results showed that the addition of the two fuels would lead to competition with DME for O and OH radicals throughout the reaction,thus reducing the reaction rate of DME and the formation rate of intermediate products.CH₃OH is several times stronger than CH₄ in the competitiveness of O and OH radicals.Another important difference is that the incorporation of CH₃OH will lead to more CH₂O generated by the reaction,thus changing the chemical balance of the DME chemical reaction path,and the DME will react more in the direction that does not produce CH₂O.