生物柴油混合比对柴油机排放颗粒特性的影响

Effects of proportions of biodiesel/diesel blends on structures of diesel engine particulates

为研究负荷和生物柴油对柴油机排放颗粒的影响,该文利用高分辨率透射电镜研究了电控高压共轨增压中冷柴油机在转速2000r/min、扭矩75和225N·m2种负荷下,燃用混合比为0、10%、50%和100%4种掺混比例(分别记做B0、B10、B50和B100)的黄连木籽生物柴油/柴油混合燃料时,产生排放颗粒的微观形貌和结构。结果表明,除B100产生排放颗粒中基本粒子的形状和粒径分布呈现出不规则性外,其余燃料的排放颗粒均由球形的基本粒子构成且粒径具有单分散特性;基本粒子具有多层类石墨微晶结构,碳层之间受到扭转和平移,存在无序内核区;B100在转速2000r/min、扭矩225N·m工况时的基本粒子平均粒径为45.57nm,与其余3种混合燃料排放颗粒的粒径相差很大。负荷和掺混比例在50%以内的生物柴油/柴油混合燃料对基本粒子的平均粒径影响不大。研究结果可为柴油机颗粒生成机理和后处理系统的设计提供参考。

In order to study the effects of engine loads and proportions of biodiesel/diesel blends on the particulate emissions,morphology and microstructure of particulates emitted from an electronic controlled high pressure common rail diesel engine were investigated by using HRTEM under the two operating conditions of rotation speed at 2 000 r/min and torque at 75 N·m and 2 000 r/min and 225 N·m,and four kinds of proportions of biodiesel/diesel blends（B0,B10,B50 and B100）.The results indicated that the primary particles generated only by B100 present irregular shape and very different particle sizes.However,the spherical primary particles consisting of the soot generated by the other fuels are typically monodisperse.The primary particles have multilayer graphite-like microcrystal structure.There exists torsion and translation between the carbon lamella.Disordered core zone is inside the primary particle.Under the operating condition of 2 000 r/min and 225N·m,the mean diameter of primary particle for B100 was 45.57 nm and very different from the other three fuels.Engine loads and proportions of biodiesel/diesel in the blends which were lower than 50% have little influence on the mean diameter of primary particle.The results can provide references for the formation mechanisms of diesel particulates and the design of after-treatment system.