【作者】 韩斌；

【导师】 陈昊；

【作者基本信息】 长安大学 ， 动力工程（专业学位）， 2019， 硕士

【摘要】 面对汽车行业蓬勃发展所带来的环境与能源的双重压力,内燃机的发展正面临着巨大挑战。在这种严峻的形势下,寻找新型可再生清洁能源缓解石油压力、改善汽车排放显得尤为重要。棕榈油是生物柴油的主要生产原料,作为全球产量最大的植物油,棕榈油以其较高的十六烷值和含氧量,可作为柴油机替代燃料应用于发动机中。但是,棕榈油粘度极大,常温下为固态,无法直接在柴油机上使用。汽油的运动粘度和馏出温度低,在柴油/棕榈油基础燃料中添加汽油可以使混合燃料理化性质达到柴油的水平,既可以有效替代化石柴油,又可以改善燃料蒸发雾化效果,形成更加均匀的可燃混合气,对改善发动机排放具有较高的期望。本文在一台四缸高压共轨柴油机上进行试验,以体积比7:3制备的柴油/棕榈油混合燃料(D70Z30)为基础燃料。选用汽油作为掺混燃料,按照20%和40%的体积比加入基础燃料中,制备柴油/棕榈油/汽油混合燃料,分别以D70Z30G20和D70Z30G40表示。首先,研究不同掺混比例的柴油/棕榈油/汽油混合燃料对发动机燃烧性能和排放性能的影响。其次,引入EGR,研究不同EGR率对发动机燃烧性能和排放性能的影响。试验结果表明:(1)随着汽油掺混比例的增加,D70Z30G20和D70Z30G40混合燃料的十六烷值、运动粘度、冷滤点和凝点等都降低,D70Z30G40混合燃料50%馏出温度最低。(2)随着发动机负荷的增加,D100、D70Z30G20和D70Z30G40三种燃料的滞燃期缩短,缸内燃烧压力增加,瞬时放热率增大,缸内平均温度升高。随着汽油掺混比例的增加,混合燃料滞燃期延长,峰值燃烧温度升高。(3)随着发动机负荷的增加,D100、D70Z30G20和D70Z30G40三种燃料的NOx排放增加,超细颗粒物数浓度峰值逐渐由小粒径向大粒径转移。随着汽油掺混比例的增加,混合燃料的NOx排放量增加,颗粒物数量浓度峰值逐渐向小粒径方向转移。(4)随着EGR率的增加,D100、D70Z30G20和D70Z30G40三种燃料的滞燃期延长,峰值燃烧压力和峰值放热率降低,燃烧温度降低。(5)随着EGR率的增加,D100、D70Z30G20和D70Z30G40三种燃料的NOx排放量均减少,颗粒物排放逐渐由小粒径向大粒径方向转移。更多还原

【Abstract】 Faced with the dual pressure of environment and energy brought by the vigorous development of automobile industry,the development of internal combustion engine is facing enormous challenges.In this severe situation,it is particularly important to find new renewable clean energy to alleviate oil pressure and improve vehicle emissions.Palm oil is the main raw material for biodiesel production.As the largest vegetable oil in the world,palm oil can be used as an alternative fuel for diesel engines because of its high cetane number and oxygen content.However,the viscosity of palm oil is very high,and it is solid at room temperature,so it can not be directly used in diesel engines.The kinematic viscosity of gasoline and the temperature of distillation are low.Adding gasoline to diesel/palm oil base fuel can make the physical and chemical properties of the blend reach the level of diesel oil.It can not only effectively replace fossil diesel oil,but also improve the evaporation and atomization effect of fuel,and form a more uniform combustible mixture.It has high expectations for improving engine emissions.In this paper,a four-cylinder high pressure common rail diesel engine was tested.The diesel/palm oil blend(D70Z30)with a volume ratio of 7:3 was used as the basic fuel.Choosing gasoline as blending fuel,adding 20% and 40% volume ratio into the base fuel to prepare diesel/palm oil/gasoline blends,expressed in D70Z30G20 and D70Z30G40 respectively.Firstly,the effects of diesel/palm oil/gasoline blends with different blending ratios on engine combustion performance and emission performance were studied.Secondly,EGR was introduced to study the effects of different EGR rates on engine combustion performance and emission performance.The results show that:(1)With the increase of gasoline blending ratio,the cetane number,kinematic viscosity,cold filter point,condensation point and calorific value of D70Z30G20 and D70Z30G40 blends decreased,and the 50% distillation temperature of D70Z30G40 blends was the lowest.(2)With the increase of engine load,the ignition delay of D100,D70Z30G20 and D70Z30G40 is shortened,the combustion pressure in cylinder increases,the instantaneous heat release rate increases,and the average temperature in cylinder increases.With theincrease of gasoline blending ratio,the ignition delay and peak combustion temperature of blended fuel increase.(3)With the increase of engine load,NOx emissions of D100,D70Z30G20 and D70Z30G40 fuels increase,and the peak concentration of ultrafine particles gradually shifts from small particle size to large particle size.With the increase of gasoline blending ratio,the NOx emission of blended fuel increases and the peak concentration of particulate matter gradually shifts to the direction of small particle size.(4)With the increase of EGR rate,the ignition delay of D100,D70Z30G20 and D70Z30G40 fuels prolongs,the peak combustion pressure and peak heat release rate decrease,and the combustion temperature decreases.(5)With the increase of EGR rate,NOx emissions of D100,D70Z30G20 and D70Z30G40 fuels decreased and the peak values of particle concentration and volume concentration gradually shifted from small particle size to large particle size.更多还原