甲醇-柴油双燃料发动机微粒数量排放特性

Particle emission characteristics of methanol-diesel dual-fuel engine

【目的】为减小甲醇-柴油双燃料发动机排放微粒中核模态粒子的数量(nucleation mode particle number,PNN).【方法】在1台由电控高压共轨柴油机改装的甲醇-柴油双燃料发动机上分别进行了甲醇掺烧比(co-combustion ratio,CCR)、引燃柴油喷射正时与负荷率特性试验.【结果】随着掺烧比的增大,核模态与积聚态微粒数量(accumulation mode particle number,PNA)均明显减小,生成微粒几何平均直径减小;引燃柴油喷射正时提前可减小生成微粒的总数量(total particle number,PNT),但掺烧比较大时提前柴油喷射正时粒径分布出现"双峰"现象,PNN大幅增加;增大发动机负荷率,PNN与PNA均有所增加,粒子几何平均直径增加,小负荷时生成的PNN明显高于中大负荷.【结论】提高掺烧比与提前引燃柴油喷射正时有利于减小PNN的生成,但当掺烧比较大时应注重柴油喷射正时的调节以防止PNN显著增加.

【Objective】To reduce the exhaust nucleation mode particle number of methanol-diesel dualfuel（DMDF）engines.【Method】Tests on the effects of the co-combustion ratio（CCR）,pilot diesel injection timing and load ratio have been conducted on a DMDF engine modified by an electrically controlled common-rail diesel engine.【Result】Both PNA and PNN decrease significantly with the increase of CCR while the geometric mean diameter shows opposite trend.As the injection timing is advanced,the PNT decreases,but when CCR is relatively high the particle distribution is bimodal and the PNN increases obviously.PNN,PNA and the geometric mean diameter all increase with the increasing load ratio.PNN at low loads is much higher than that of medium and high loads.【Conclusion】Both the increasing of CCR and advancing of diesel injection timing are beneficial for the decrease of PNN,and when the CCR is large the adjusting of injection timing is important in order to prevent the sharp increase of PNN.