靴形喷油速率耦合预喷射对超高压共轨柴油机性能的影响

Effect of saddle-shaped fuel injection rate coupled with pilot injection on the performance of ultra-high pressure common-rail diesel engine

在介绍超高压共轨系统工作原理的基础上,基于GT-Power软件建立单缸超高压共轨柴油机的仿真模型,并利用试验验证模型的准确性,而后通过模型分析不同喷油速率、靴形喷油速率耦合不同预喷油量和靴形喷油速率耦合不同预喷提前角对超高压共轨柴油机动力性、经济性以及燃烧排放特性的影响。结果表明:通过调整超高压共轨系统中电控增压器电磁阀和喷油器电磁阀的开启时间,能够实现喷油速率的柔性可调。随着喷油速率从矩形变化到靴形,柴油机缸内压力、温度以及NO_x排放量均逐渐降低,而soot排放量逐渐升高,且靴形喷油速率可使柴油机获得最大的功率(扭矩)和最低的油耗率。靴形喷油速率耦合较小的预喷油量可以使柴油机获得更好的动力性、经济性和燃烧特性,但同时也会导致NO_x排放量的升高。靴形喷油速率耦合较大的预喷提前角有助于改善柴油机排放特性,但受到预喷油量的限制,效果并不明显。

On the basis of introducing the working principle of ultrahigh pressure common-rail system,the simulation model of ultrahigh pressure common-rail diesel engine of single cylinder was built by using GT-Power software,and the accuracy of this model was verified via experiment,then the effects of different fuel injection rate,saddle-shaped fuel injection rate coupled with different pilot injection fuel mass and different pilot injection advance angle on the power,economy,combustion and emission characteristics of ultrahigh pressure commonrail-diesel engine were analyzed by this model.The results show that the variable fuel injection rate can be realized by adjusting the opening time of the electric-controlled pressure amplifier solenoid valve and the injector solenoid valve in ultra-high pressure commonrail system.With the fuel injection rate varying from rectangular to saddle-shaped,the cylinder pressure,temperature and NOxemissions of diesel engine decrease gradually,while the soot emissions rise gradually.The saddle-shaped fuel injection rate can make the diesel engine acquire the maximum power(torque)and the lowest fuel consumption rate.The saddle-shaped fuel injection rate coupled with lesser pilot injection fuel mass can make the diesel engine power,economy and combustion characteristics better,but it also leads to the rise of NOxemissions.The saddle-shaped fuel injection rate coupled with larger pilot injection advance angle can improve the emission characteristics of diesel engine,but the effect is not obvious due to the limit of pilot injection fuel mass.