双燃料直喷发动机喷孔几何位置对燃烧排放的影响

Influence of the Position of Nozzle Holes on Combustion and Emissions for a Direct Injection Dual Fuel Engine

基于柴油引燃天然气缸内直喷发动机,采用AVL-Fire软件研究了天然气和柴油喷孔相对交角、相对距离和相对夹角这3个重要几何参数对燃烧排放的影响.结果表明:两喷孔相对交角影响NOx和碳烟(soot)排放,NO最小生成量比最大生成量少36%,,通过改变相对交角可以同时降低NO和soot排放,但对缸内平均压力的影响较小;两喷孔相对距离会影响污染物生成,并且相对距离越小,温度场分布越均匀,发动机缸内平均压力越高;两喷孔相对夹角减小时,发动机缸内平均压力升高,NO_x排放增加.研究结果对双燃料直喷发动机的两喷孔相对位置的优化有一定的指导作用.

The combustion process and toxic emissions of a dual fuel engine fueled with directly injected natural gas and pilot diesel was researched by using the AVL-Fire software. This simulation work is mainly focus on the effects of three important geometric position parameters on combustion and emissions： relative crossing angles, distances and included angles of the diesel nozzle hole and natural gas nozzle hole. The results show that different crossing angles of the two holes can affect the NO, and soot emissions. The minimum NO emission is 36% lower than the maximum NO emission. By changing the crossing angle, NO emissions and soot emissions can be reduced at the same time, while the crossing angle has little effects on the average cylinder pressure. The relative distances of the two holes have effect on the pollution formation, and the smaller nozzle hole distance will result in more uniform temperature distribution and higher average cylinder pressure. With the decrease of the relative included angle, both average pressure and NOx emission increase. These results provide a useful guidance for the relative position design between the dual fuel nozzles.