燃空当量比对液体燃料无焰燃烧影响的研究

Effect of fuel air equivalence ratio on the flameless combustion of liquid hydrocarbon

以微型燃气轮机为应用背景,设计了基于液雾无焰燃烧的模型燃烧室,以实验为主、数值模拟为辅的手段研究了0#柴油/空气的燃空当量比对模型燃烧室的流场结构、燃烧模式、无焰燃烧范围、燃烧温度及分布和污染物排放的影响.结果表明:燃烧室流场呈现明显的环形回流涡,为高温烟气循环提供了流体动力学基础;燃料喷孔附近的混合情况对整个燃烧模式的转变具有重要影响;该燃烧室工作在无焰燃烧模式的燃空当量比Φ范围为0.25～0.50,无焰状态下燃烧室内温度分布均匀;燃烧室平均温度Tavg和污染排放受到Φ和输入功率的影响,在实验范围内,输入功率相同时,随Φ减小,燃烧室平均温度降低,CO和NOx排放浓度增加,另外,Φ相同时,输入功率越低,Tavg越低,CO排放浓度越大,且输入功率越低CO排放浓度增长越快,NOx受输入功率的影响相对小得多.从实验结果分析,适当提高空气预热温度是增强低燃烧室热密度时的贫燃稳定性、拓展贫燃极限和强化燃烧的有效措施.

Abstract： A laboratory scale model combustor was designed based on flameless combustion of liquid spray in a microturbine atmosphere. The effects of fuel （0 # diesel） /air equivalence ratio q~ on the flow field, combustion regime, range of flameless mode, temperature and pollution emissions of the model combustor were studied mainly through experiments and supplementally numerical computation. The results indicate that there is an obvious ring vortex in the flow field, which provides a basis of fluid dynamics for the recirculation of high temperature exhaust gases. The mixture of species around the fuel nozzle is significant to the conversion ot the comDusrlon regime The average combustor is 0. 25≤Ф≤0. 50, and in which the combustion temperature is homogeneous. chamber temperature Tavg and pollutant emissions are impacted by Ф and the thermal input. At the same thermal input conditions, Tavg increases and the emissions o{ CO and NO~ drop with increasing @ in the experimental range. At the same @ condition, Tavg drops and the emissions o~ CO and NO~ increase with the decrease in thermal input. The ~ower the thermal input, the faster the growth in CO emission amount, while NO~ is a~~ected much less. It can be concluded {rum the analysis that appropriate preheating o~ combustion air is an dfective way to enhance the lean combustion stability with low chamber heat density and expand lean flammability.