部分加氢生物柴油改善柴油机的燃烧与排放

Improving Combustion and Emission Performances of a Diesel Engine Fueled with Partially Hydrogenated Biodiesel

部分加氢工艺可显著提升生物柴油的氧化安定性,同时改善燃料的着火性能,是提高生物柴油品质的有效途径。以Raney-Ni为催化剂,异丙醇为供氢体,在85℃的水环境下对大豆生物柴油进行催化转移加氢试验,得到部分加氢生物柴油,并以传统柴油作为参照,分别制备B20(80%传统柴油+20%生物柴油)和PHB20(80%传统柴油+20%加氢生物柴油),在186FA型柴油机上进行发动机性能试验,并使用燃烧分析仪、尾气分析仪和烟度计等仪器探究加氢生物柴油对柴油机燃烧过程及排放性能的影响。研究结果表明:柴油机燃用柴油、B20及PHB20的当量燃油消耗率基本相当;在标定工况下,尽管加氢生物柴油运动黏度略有升高而不利于燃油雾化,但其十六烷值较高更易于燃烧,在燃料特性的综合影响下,与柴油机燃用柴油相比,B20和PHB20的着火时刻依次提前了0.8°曲轴转角和1.4°曲轴转角,瞬时放热峰及最大爆发压力亦随之提前,但最大放热率和最大爆发压力依次略有降低;在标定工况下,与燃用柴油相比, B20的HC,CO和烟度排放分别下降了9.9%、9.3%和15.2%,NO_x排放上升了8.5%;而PHB20的HC,CO和烟度排放分别下降了12.4%、13.5%和17.1%,NO_x排放上升了6.7%;综合可见,PHB20改善柴油机燃烧及排放的效果优于B20。

The oxidation stability and ignitability of biodiesel can be significantly raised by partial hydrogenation, which is an effective approach to upgrade the biodiesel quality. With isopropanol as hydrogen donor, partial hydrogenation of soybean methyl ester(SME) was conducted by catalysis of Raney-Ni under water at the temperature of 85 ℃ to obtain partially hydrogenated soybean methyl ester(PHSME). To explore the effects of hydrogenated biodiesel on combustion and emissions, a comparative experiment of engine performance was conducted on a one-cylinder 186 FA diesel engine with equipments comprising a combustion analyzer, exhaust gas analyzer and smoke meter. The experiment was conducted when the engine was individually fueled with the reference diesel, B20(80% diesel+20% SME) and PHB20(80% diesel+20% PHSME). The results show that diesel, B20 and PHB20 roughly share identical equivalent fuel consumptions. Although an increase in the kinematic viscosity for the partially hydrogenated biodiesel may lead to weak atomization, however, the partially hydrogenated biodiesel can combust better owing to its higher cetane number. Compared with the reference diesel, at the rated power mode, the ignition timing was advanced by 0.8 ° crank angle and 1.4 ° crank angle respectively for B20 and PHB20;the pressure peaks and heat release peaks were advanced accordingly, while their values were slightly reduced successively. Compared with the reference diesel, the HC, CO and PM emissions of B20 were reduced by 9.9%, 9.3% and 15.2% individually, whereas the NO_x emission was increased by 8.5%;while the HC, CO and PM emissions of PHB20 were reduced by 12.4%, 13.5% and 17.1% respectively, and the NO_x emission was increased by 6.7%. As a total, PHB20 presents better combustion and emission performances than B20.