汽车加热器内燃烧的数值模拟

利用AVL公司开发的FIRE软件,对一典型结构蒸发混合式汽车加热器燃烧室内的燃烧过程进行了数值模拟.其中,蒸发和燃烧分别采用Wall Film模型、Coherent Flame模型,氮氧化物(NOx)采用Zeldovich不平衡原理建模,碳烟(Soot)模型为FIRE模型.计算结果及分析表明,一层进气孔布置对燃油蒸汽浓度分布影响很大.加大进气孔直径使进气中心涡流增强,燃油在一级燃烧室中蒸发量增加.主要燃烧发生在二级燃烧室.进气孔切向进气能形成较强的中心涡流,使燃烧高温区主要集中在二级燃烧室的纵向轴心附近.一级燃烧室的周向涡区和二级燃烧室上半部的高温区是Soot生成速率最大的部位;最高燃烧温度未达NOx的生成温度条件,其生成量极少.

Numerical simulation of combustion in vehicle air heater

Numerical simulation of combustion process in vaporized/mixed fuel vehicle air heater combustion chambers was conducted with software "FIRE" developed by AVL company.The simulation models adopted were: Wall Film model for fuel evaporation,Coherent Flame model for combustion,Zeldovich model for NO_x and FIRE model for soot formation.Simulation results show that the air inlets of the first ring are crucial to vaporized fuel concentration field.As the air inlet diameters increase,the intake central swirl is intensified and thus fuel evaporation in the first combustion chamber is improved.Combustion mostly happens in the second combustion chamber.Tangential intake results in intensified central swirl,which causes the high temperature zone to concentrate around the longitudinal axis of the second combustion chamber.The highest soot formation rate appears at the circumferential swirl zone in the first combustion chamber and the high temperature zone in the upper half of the second combustion chamber.As the peak temperature in the combustion chambers is below the NO_x formation criteria, only very few NO_x is formed.