进气组分耦合预喷对柴油机燃烧过程影响模拟  

Influence Mechanism of Pilot Injection Coupled with Intake Components on the Working Process of Diesel Engine

作　　者：沈颖刚[1] 朱文霞[1] 肖仁鑫[1] 陈贵升[1] 陈春林[1] Shen Yinggang Zhu Wenxia Xiao Renxin Chen Guisheng Chen Chunlin(Yunnan key Laboratory of Internal Combustion Engine, Kunming University of Science and Technology, Kunming 650500, Chin)

机构地区：[1]昆明理工大学云南省内燃机重点实验室,云南昆明650500

出　　处：《内燃机学报》2017年第1期16-24,共9页Transactions of Csice

基　　金：国家自然科学基金资助项目(51366007);云南省应用基础研究面上资助项目(2013FB019);云南省院省校科技合作资助项目(2013ID001)

摘　　要：通过高压共轨柴油机,基于正庚烷/甲苯/正己烯混合物简化动力学机理耦合三维CFD模型,模拟研究不同进气组分(O_2、H_2和CO_2)耦合策略对发动机燃烧过程的影响.研究表明:当预-主喷间隔为4°,CA时,相比单次喷射,预喷使主喷滞燃期明显缩短(尤其掺H_2时),瞬时放热率峰值与最大压力升高率(MPRR)均降低;但随预-主喷间隔增大,预喷对主喷燃烧影响减弱.进气掺O_2时,富氧氛围使燃油充分燃烧,预-主喷间隔对NO和碳烟(soot)影响均较小.进气掺H_2和CO_2时,预喷使乙炔(C2H,2)和多环芳香烃芘(A4)生成增多,导致soot排放较单次喷射显著升高(尤其掺CO_2).但随预-主喷间隔增大,soot因主喷滞燃期延长而逐渐降低;对于进气掺H_2,预喷油量为10%,时,随主喷定时推迟,MPRR降低,soot升高;当预喷量增至20%,时,预喷燃烧会引起大量H_2早燃放热,削弱主喷定时对主喷燃烧的影响,MPRR因燃烧重心前移仍较高.因而进气掺H_2,预喷比例不宜过高,且喷油定时应适当推迟.In a common-rail diesel engine, the effects of different intake components （O2, CO2 and H2）and pilot- injection strategy on engine combustion process were studied by coupling three-dimensional CFD model with the sim- plified kinetic mechanism of the mixture （n-heptaneshortens/toluene/1-hexene）. Results showed that, as compared with single injection, ignition delay for the main injection shortens remarkably （especially for H2 addition） when pilot- main injection interval was kept at 4° CA. As a result, the peak of heat release rate and rate of maximum pressure rise （MPRR） reduce simultaneously. However, the effects of pilot-injection strategy on the main-injection combustion become weaker with increased pilot-main injection interval. When O2 is added into the intake charge, pilot-main in- jection interval has a little effect on NO and soot because of oxygen-rich combustion. As H2 and CO2 are added into the intake charge create more C2H2 and A4, soot increases sharply （especially for CO2）. Soot reduces gradually due to the prolonged ignition delay with increased pilot-main injection interval. For H2 addition, MPRR decreases while soot increases with retarding the main-injection timing when pilot-injection fuel mass is kept at 10% of total mass. When pilot-injection fuel mass increases up to 20%, pilot-injection combustion leads to large amount of heat release by H2 premature combustion, which will weaken the influence of main-injection timing on main-injection combus- tion. Meanwhile, MPRR still remains much high owing to the advancement of the heat center. Therefore, for H2 addition, pilot-injection proportion should be controlled and main-injection timing should be retarded appropriately.

关 键 词：共轨柴油机 预喷策略 进气组分 压力升高率 碳烟 

分 类 号：TK421.2[动力工程及工程热物理—动力机械及工程]