某型农用柴油机NO_x生成的模拟计算

应用商用FLUENT软件建立了柴油机工作过程的计算模型,计算得到了不同曲轴转角下缸内温度场和NOx浓度场的分布情况。分析结果表明:压缩过程中,缸内温度在壁面处有较大梯度。在燃油喷出后燃烧开始前,油束外部与内部的温差较大,在喷油嘴附近形成高温区域。在急速燃烧阶段,燃烧区域主要集中在柴油油束的外围;燃烧后期,主要燃烧区域是近壁面区域。NOx浓度高的区域集中在高温富氧的区域;NOx总量的变化规律先是持续增加,然后下降,最后保持不变。

Simulation of NOx Emissions for Agricultural Diesel Engine

The calculation model was carried out by commercially software FLUENT.The distribution of temperature and NOx concentration field under different crank angle were calculated.The results of the analysis show that there was a greater temperature gradient near the cylinder wall.The temperature difference between external and internal oil-beam was larger,and then a high-temperature region formated near the nozzle after the fuel spray and before the start of combustion.In the rapid combustion phase,combustion region was mainly focused on the oil-spray periphery.During later combustion period,the main combustion zone was near the wall,the areas of high concentration for NOx were concentrated in high-temperature and oxygen-rich regions.Total NOx emissions increased at first,then declined,and finally remained unchanged.