稀释对射流扩散火焰抬举及吹熄特性影响的实验研究

以低热值气体燃料的燃烧利用为背景，以N2或CO2稀释的甲烷或丙烷及内径2mm或3mm的喷管作为多重变量，实验研究了射流扩散火焰的抬举速度及吹熄速度随燃料稀释比的变化规律.结果发现，随着稀释比的增大，火焰抬举速度近似呈线性缓慢减小，吹熄速度近似呈指数快速衰减.分析表明，这主要归因于稀释导致了当量混合层流火焰速度、初始燃料质量分数及燃烧放热的减小，并对低热值气体燃料的燃烧器设计提出了建议.此外，大于临界稀释比时，附着火焰随射流速度的增大不能转变为稳定的抬举火焰而会发生直接吹熄，依据甲烷和丙烷临界稀释比对应的射流雷诺数推测出二者的临界稀释比可能受不同机理的控制.
Abstract：On the background of combustion utilization of low calorific value gas fuel, methane or propane diluted by N2 or CO2 and nozzles of 2mm or 3mm inner diameter are set as multiple experimental variables. The liftoff and blowout velocities of jet diffusion flame varying with the diluent concentration were experimentally investigated. With the increase of the diluent concentration, the liftoff velocities slowly decline almost linearly, while the blowout velocities quickly decrease nearly exponentially. The analysis shows that the tendencies may be attributed to the decreases in the stoichiometric laminar burning velocity, the original fuel mass fraction and heat release. Suggestions on the design of burner utilizing low calorific value gas fuel are proposed. In addition, exceeding the critical diluent concentration, the attached flame is directly quenched instead of being a stable lifted flame with the increase of the jet velocity. According to the Reynolds numbers of methane and propane at each critical diluent concentration, it can be inferred that the two critical diluent concentrations of methane and propane are controlled by different mechanisms.