一次氧化剂O2体积分数对富氧燃烧煤粉着火距离影响的数值模拟

摘要

Numerical simulation was carried out to a 40 kW coaxial jet oxy-coal combustion tacility,so as to analyze the effect of O2 volumetric fraction in primary oxidant on the ignition standoff distance under given overall O2 volumetric fraction and excess oxidant ratio,and to study the ignition mechanism and flame stability of the oxy-coal combustion under low O2 volumetric fractions in primary oxidant.Results show that the ignition standoff distance of oxy-coal combustion is found to be small with an attached flame for an O2 volumetric fraction of 20.9 ％ in primary oxidant,an overall O2 volumetric fraction of 40 ％ and an excess oxidant ratio of 1.15.However,the ignition is delayed with an increased standoff distance and a detached flame when the O2 volumetric fraction in primary oxidant drops to 14.6％,10.0％ and 5.5％,respectively.Higher preheat temperature of secondary oxidant is helpful to the formation of stable flames under low O2 volumetric fraction in primary oxidant for oxy-coal combustion system.%对40 kW同轴射流富氧煤粉燃烧试验系统进行数值模拟,研究了在总体O2体积分数和氧化剂过量系数一定的条件下,不同一次氧化剂O2体积分数对同轴射流富氧燃烧煤粉着火距离的影响,分析了低一次氧化剂O2体积分数下富氧燃烧煤粉着火及火焰稳定性.结果表明:在总体O2体积分数为40％和氧化剂过量系数为1.15的条件下,当一次氧化剂O2体积分数为20.9％时,着火距离较小,为附着火焰；当一次氧化剂O2体积分数减小至14.6％、10.0％和5.5％时,着火距离明显增大,着火延迟,为分离火焰；适当提高二次氧化剂预热温度有利于低一次氧化剂O2体积分数下富氧燃烧的煤粉着火及火焰稳定.