The combustion and emission characteristics of State Ⅴ diesel engine fueled with BD20 blended fuel (80% volume fraction of State Ⅴ diesel and 20% volume fraction of waste cooking oil biodiesel ) were researched under different pilot-injec-tion conditions .The results show that the ignition delay period and the combustion duration becomes shorter and longer respec-tively after pilot-injection .Compared with pilot-injection interval ,the pilot-injection quantity has more significant influence on ignition delay period and combustion duration .The pilot-injection decreases the pressure rise rate of main combustion remark-ably and improves the intensity of combustion with better effect when configuring a shorter pilot-injection interval in low load and a larger pilot-injection interval in high load .After applying the pilot-injection ,NOx emission decreases ,but PM emission in-creases in most conditions .For each load ,there is a better pilot-injection scheme which can improve NO x and PM emission sim-ultaneously .%研究了不同预喷条件下满足国Ⅴ排放的高压共轨柴油机燃用混合燃料BD20（含80％体积分数的国Ⅴ柴油和20％体积分数的餐饮废油制生物柴油）的燃烧及排放特性。结果表明：采用预喷射后滞燃期有所缩短，燃烧持续期有所增大。相比于预喷间隔，预喷油量对滞燃期及燃烧持续期的影响更为显著；预喷射显著减小了主燃烧的压力升高率，改善了燃烧的剧烈程度，且低负荷取较小预喷间隔、高负荷取较大预喷间隔效果较优；采用预喷射后NO x 排放均有所降低，大部分预喷射条件下PM 排放有所增加，各负荷均存在着较佳预喷射方案，可以同时改善NO x 及PM 排放。
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