添加H_(2)对生物质气层流燃烧特性的影响

Effect of adding H_(2)on laminar combustion characteristics of biomass gas

为研究H_(2)对生物质气层流燃烧特性的影响,在内径和长度均为200 mm,点火位置为正中央的圆柱形定容燃烧弹内进行当量比为0.6~1.4、H_(2)体积分数为7.15%~33.15%的掺氢生物质气/空气燃烧试验。利用高速摄像仪采集火焰传播图片,并通过计算分析软件Chemkin-Pro进行化学反应路径分析。研究结果表明:添加H_(2)对生物质气/空气的层流燃烧速度起促进作用,在贫燃侧增长效应平稳而在富燃侧增长效应显著,使火焰的不稳定性增强;火焰结构中主要自由基浓度的增大是引起层流燃烧速度增大的主要化学动力学原因;H_(2)主要通过参与HCO基团氧化加快反应速率,富燃侧层流燃烧速度显著增大的原因是H_(2)作用的路径多为有O_(2)参与的反应。

To study the effect of H_(2)on laminar combustion characteristics of biomass gas,hydrogen-doped biomass gas/air combustion experiments were carried out with volume fractions 7.15%-33.15%hydrogen at an equivalent ratio equal to 0.6-1.4.These experiments were in a constant volume burning bomb with an inner diameter and length of 200 mm and the ignition position was in the center.Ignition electrodes were modified by welding 0.45 mm tungsten wire with two ceramic single-stage ignition rods,which is the main component of a high-energy pulse electronic igniter.Premixed gas was obtained by partial pressure method and kept still for 10 minutes,and trigger the high-speed camera a split second before ignition to obtain pictures of the flame propagation process.Analyzed the changes of chemical reaction paths at adding hydrogen through Chemkin-Pro.The results show that the addition of H_(2)promotes the laminar burning velocity of biomass gas/air,lean combustion side smooth growth while rich side significantly,and the instability of the flame with the increase of H_(2)volume fraction increased;The increase of main free radicals in the flame structure is main chemical kinetics reason for the growth in laminar burning velocity;The oxidation of CH4determines the speed of the overall combustion reaction,the increase of H_(2)mainly promotes the oxidation of CH4and CO in three routes.One is the process of promoting the oxidation of CO into CO_(2),which belongs to the termination reaction.The other is to promote the oxidation process of the CH group,and the CH group and O_(2)together to form the HCO group.The third is the further oxidation of the HCO group from HO_(2),and it is also the most important process;The frequent participation of O_(2)in the oxidation path is the reason for the significant increase in the laminar burning velocity on the fuel-rich side.