缸内燃油喷射发动机碳烟生成机理特征分析

摘要

为精确计算压燃式缸内燃油喷射发动机中的碳烟生成,提出了新的计算模型.不同的燃烧室区域应用不同的计算模型,当区域温度T〈1 500 K,只计算气体状态下生成的碳烟前驱物PAHs;当区域温度T≥1 500 K,碳烟前驱物PAHs和源项均进行计算。计算前驱物PAHs利用修改的F-M模型,碳烟源项的生成包括碳烟的起始、生长、氧化以及聚合。同时认为温度和过量空气系数是影响碳烟生成的最主要因素,即在温度T〉1 500 K,过量空气系数Ф〈0.6才能产生碳烟.新的计算模型移植在KIVA-3V源代码中,计算了直喷式发动机在不同喷射时间、不同轨压下的碳烟瞬态值,并用试验验证了该模型.给计算直喷式柴油机生成的碳烟提供了新的方法.%To calculate soot source terms the new model is presented according to recent literature data.Different models are used in deferent temperature zones in combustion chamber.When zone temperature T1 500 K,gas-phase kinetics is considered and the soot precursors-PAHs（Polycyclic aromatic hydrocarbons） is calculated.When zone temperature T ≥1500 K,the gas-phase chemistry and soot source terms are calculated.PAHs model is the modified Frenklach-Ma model which includes formation and oxidation of PAHs.The formation of soot can be subdivided into the process of particle inception,surface growth and oxidation,particle coagulation.Temperature and excess air coefficient are the most important parameters in the new model.The soot is created only when temperature T≥1 500 K and excess air coefficient Ф0.6.The new model is implemented into the KIVA-3V code and the results of soot with variation of injection time and variation of rail pressure between simulation and experimental data are analyzed.It gives a new way to predict soot for direct-injection diesel engine.