柴油在甲醇/空气高温热氛围中的着火和燃烧特性

在定容燃烧弹上进行了柴油分别在空气和在甲醇/空气预混均质混合气中着火燃烧的实验研究.结果表明,与空气热氛围相比,甲醇混合气热氛围延长了柴油的滞燃期和加长了火焰浮起高度.采用正庚烷-甲醇的详细化学反应机理,利用数值模拟的方法计算了零维模型中正庚烷及正庚烷加甲醇的燃烧反应过程和中间产物历程.其结果表明,甲醇的加入使得正庚烷的高低温放热反应开始时刻后移,滞燃期延长,低温放热反应峰值明显下降,且无明显的负温度系数区,高温反应放热峰值高于其在空气氛围中,归其原因在于甲醇大量消耗着火的OH自由基,并将其转化为低温氧化中不活跃的H2O2,使得系统着火前反应活性减弱.实验和计算结果均表现出甲醇具有抑制柴油及其参比燃料着火的作用.

Ignition and Combustion Characteristics of Diesel Spray in Premixed Methanol/Air Mixture with High Temperature

This paper reported the research on the ignition and combustion characteristics of diesel fuel in pure air premixed and methanol/air mixture in a constant volume combustion bomb,respectively.The experimental results showed that the ignition delay of diesel fuel was prolonged and the lift-off length of diesel fuel flame was extended in the premixed methanol ambient.Combustion of n-heptane and n-heptane mixed with methanol in zero-dimension model was simulated according to the reaction theory of n-heptane and methanol.The results showed that,with the addition of methanol,high temperature and low temperature exothermic reaction are delayed,ignition delay is prolonged,the peak value of low temperature exothermic reaction declined markedly without obvious negative temperature coefficient district,and the peak value of high temperature exothermic reaction is higher than that in the pure air.These phenomena are attributed to the effect of methanol which consumes hydroxyl radical and converts this active radical to inactive H2O2.So the reaction activity of the system before ignition is decreased.Both experiments and calculation illustrated that methanol plays a great important role in delaying the ignition of diesel.