Experimental Studv On Catalytic Combustion Characteristics Of Dimethvl Ether In Quartz Microchannels

In recent years,the development of micro fabrication?micro electronics and information technology has promoted the development of portable devices.Microscale combustion systems are becoming more and more widely used in the fields of aerospace,military,and life because of its small size,high energy density and long service time.How to improve combustion stability and efficiency is the difficult and hot issue in micro energy power system.This paper focused on this scientific problem,experiments on dimethyl ether/air catalytic combustion were carried out in quartz microchannels.The effects of different flow rate,equivalence ratios,catalyst layouts,size and heating temperature on the combustion characteristics?stable combustion limits,flame shapes,wall temperature distributions,conversion rates?of fuels were analyzed.Pt/ZSM-5 was adopted as catalyst to carry out the catalytic combustion experiment of dimethyl ether under fixed wall temperature.At ? = 1,v = 0.1m/s,the ignition point of dimethyl ether is 143?.When the dimethyl ether reacted,the wall temperature distribution of the combustor had obvious high temperature region,and it was located at the catalyst.When there was no reaction,the wall temperature distribution is more uniform without high temperature zone.With the increase of v,the conversion of dimethyl ether decreased monotonously.With the increase of ?,the conversion of dimethyl ether increased first and then decreased,and reached the maximum value at ? = 1.2.The combustion products of dimethyl ether were CO₂ and H₂O.Methane and ethane are detected in the combustion products at high equivalence ratios.Catalytic combustion experiments were performed in quartz microchannels with different gap h.The experimental results show that the reaction temperature of dimethyl ether decreases about 110? in the combustor with gap h=2mm with the catalyst.The conversion rate in the combustor with h = 2mm is higher than the combustor with h = 4mm;the exhaust temperature in the combustor with h = 4mm is higher than the combustor with h = 2mm;the wall temperature in the combustor with h = 2mm is higher than the combustor with h = 4mm.Experiments on dimethyl ether/air catalytic combustion were carried out in quartz microchannels.The experimental results show that the stable combustion range is significantly higher after adding quartz wool in the combustors.When there is no quartz wool,the flame could be stable only in the condition of that the equivalence ratio ? varied from 1.2 to 1.4,and the flame is asymmetric.If ?>1.4,the flame would oscillate and the oscillation cycle could be divided into three main stages;?<1.2,there is no flame.Flame stations at the quartz wool after adding quartz wool and the height of the flame increases with the increase of flow rate v.The wall temperature distribution along the centerline of the wall is symmetrical and it increases with the increase of v.Simultaneously,the location of the peak temperature moves to the outlet of the combustor with the increase of v.The mole fraction of CO₂ of the exhaust gas first increases and then decreases with an increasing ?,and reaches a maximum value 13.44%when ? =1.The mole fraction of CO and H₂ of the exhaust gas increases with the increase of ?.When ?<1,there is little CO and H₂ in the exhaust gas.In contrast,some CO and H₂ exists in the exhaust gas at the rich-fuel conditions.