Experimental And Numerical Simulation Of Free Radical Distribution Of Methane Premixed Flame In Micro-Channels

With the development of MEMS technology,the development of efficient,durable,miniaturized energy supply system has become the primary goal in this field.Compared with chemical batteries,hydrocarbon fuel has the advantages of high energy density,low cost and environmental protection.In order to improve the combustion utilization rate,the mechanism and detailed situation of the combustion process in-depth study and research is essential.Although the chemical deactivation caused by free radical inactivation has aroused the concern of everyone,but the mechanism of free radicals near the wall and the mechanism of flame propagation and flameout,there is still insufficient evidence in the experiment,and the work of numerical analysis is less.This article will be in this regard to make in-depth study.In this paper,the behavior of OH radicals in methane/air premixed combustion flame near the near wall was studied by plane laser induced fluorescence.The distribution of OH radicals in wall material,outlet gas flow rate,excess air coefficient and wall spacing was investigated.Maximum fluorescence intensity and quenching distance.The results show that the maximum fluorescence intensity of OH radicals in the channel is 304 steel,the lowest is magnesium alloy AZ31B;the quenching distance is the smallest material of 304 steel,the largest is magnesium alloy AZ31B;the maximum OH radical fluorescence intensity is bigger The smaller the fluorescence intensity will increase the maximum fluorescence intensity of the flame,so that the OH radicals are more easily quenched,resulting in a greater quenching distance;reduce the excess air coefficient,the maximum fluorescence intensity will increase;when the wall When the distance is 7 mm,there are two independent OH regions,and there is almost no OH radical in the middle.This phenomenon is free radical ignition and ignition.The main reason is the hot flame in the heat dissipation condition and the area where the upper wall heat dissipation is small Reignite.In order to explore the influence of wall reaction on OH radicals in methane/air premixed flame,the effects of wall activity,inlet velocity,pressure and equivalent ratio on the temperature distribution and the free radicals such as OH were investigated by numerical simulation.The influence of distribution characteristics.It was found that with the increase of reaction pressure,the number of free radical collisions per unit time in micro-channels increased and the reaction temperature increased.OH radicals participate in the reaction near the wall,so that the OH free radical mass fraction of the active wall micro-channels is less than that of the inert wall.As the equivalent ratio increases from 0.6 to 1.2,the reaction and high temperature regions increase,but the maximum temperature decreases.The mass fraction of OH radical in the micro-channel increases with the increase of the equivalent ratio,and the increase of OH radical near the inert wall is larger than that of the active wall.Increasing the flow rate,increasing the disturbance in the micro-channel,intensifying the combustion reaction,leading to the increase of the temperature in the micro-channel and the increase of the OH radical mass fraction.The H,O,OH and CH3 radicals in the micro-channel show that the mass fraction of the inert wall is slightly higher than that of the active wall.The peak of mass fraction of CH3 radical appears at the nearest axial position,and the other three free radical mass fraction The peak is about the same axial position.