柴油机富氧燃烧的粒径分布及多环芳香烃的演化历程研究  

Study on Particle Size Distribution and PAHs Formation History in Oxygen-Enriched Combustion Process of Diesel Engine

作　　者：张韦[1,2] 舒歌群[1] 徐彪[1] 赵伟[1] 沈颖刚[2] 翁家庆[2] 

机构地区：[1]天津大学内燃机燃烧学国家重点实验室,天津300072 [2]昆明理工大学交通工程学院,昆明650500

出　　处：《内燃机工程》2013年第3期1-8,共8页Chinese Internal Combustion Engine Engineering

基　　金：国家自然科学基金资助项目(50976077)

摘　　要：利用正庚烷的简化模型、Wang[1]的多环芳香烃(PAHs)详细机理及泽尔多维奇氮氧(NOx)模型,建立适用于描述柴油机富氧燃烧并能预测PAHs与NOx的化学动力学模型。使用CHEMKIN对组合模型与拉莫斯利佛尔(LLNL)正庚烷详细模型的缸内压力及温度计算结果进行对比,验证了化学模型的准确性。将化学模型与燃烧室计算流体力学(CFD)模型耦合,进行氧浓度为21%～24%的直喷式柴油机富氧燃烧的缸内数值模拟。开展与模拟计算相对应的发动机台架试验研究,用粒径分析仪测量不同进气氧浓度下颗粒物的数量与大小分布。研究结果表明:耦合计算可以准确预测富氧燃烧的缸内着火时刻及燃烧状况,NO及PAHs的变化趋势与试验测量值近似。分析5.5°CA ATDC时刻燃烧室内PAHs的质量分数分布切片可知,与21%进气氧体积分数的空气助燃相比,24%进气氧体积分数的富氧燃烧对PAHs形成具有明显的抑制作用。A combined chemical kinetics model was developed based on reduced n-heptane mechanism, Wang＇s detailed PAHs mechanism and Zeldovich NOx mechanism to study the oxygen enriched combustion of diesel engine. The combined model was validated by comparing in-cylinder pressures and temperatures calculated by it and LLNL detailed n-heptane model using softwar.e package CHEMKIN. The model was coupled with CFD model to simulate the combustion process in a DI diesel engine when oxygen density reached 21%-24%. Related engine bench tests were also conducted to measure the particle number and size distributions under various oxygen density. The results indicate that the in-cylinder ignition timing and combustion can be predicted well by the coupled model, and the calculated NO and PAHs formation trend are very close to experiment results. The result of the in-cylinder PAHs mass fraction distribution at 5. 5℃A ATDC shows that 24% oxygen density has obvious suppression effect on PAHs formation compared with 21% condition.

关 键 词：内燃机 直喷式柴油机 富氧进气 多环芳香烃 富氧燃烧 耦合计算 燃烧特性 

分 类 号：TK421.2[动力工程及工程热物理—动力机械及工程]