柴油/正戊醇/甲醇三元微乳化燃料柴油机燃烧与排放特性研究

Analysis of Combustion and Emission Characteristics of a Diesel Engine Fueled with Ternary Micro-Emulsion Blends

为了使柴油与甲醇互溶,提高燃料氧含量以控制碳烟排放,以正戊醇作为助溶剂,形成柴油/正戊醇/甲醇三元微乳化燃料,对三元燃料在不同温度下的互溶性进行了研究。在一台电控高压共轨柴油机上测试了1 400r/min转速下柴油/正戊醇/甲醇三元微乳化燃料的燃烧压力和排放特性;计算了瞬时燃烧放热率与燃烧温度,并与柴油进行对比。研究结果表明:甲醇能够以一定比例与柴油/正戊醇互溶,且互溶比例随温度升高而增大。与纯柴油相比,随氧含量的增加,混合燃料的滞燃期延长,燃烧持续期缩短,峰值燃烧温度升高;在中低负荷,峰值燃烧放热率上升;在高负荷,三元微乳化燃料的峰值燃烧放热率下降,但其扩散燃烧强度增加;混合燃料的有效燃油消耗率增加,但是其热值逐渐降低,有效热效率上升;3种含氧燃料的CO排放在低负荷时增加,高负荷时降低;HC及NOx排放升高,NO2在NOx中的比例下降;碳烟排放明显减少。

In order to make diesel and methanol miscible,and to increase fuel oxygen content to control soot emissions,n-pentanol was used as a co-solvent to prepare the ternary micro-emulsion fuels blended with diesel,n-pentanol and methanol.The combustion pressure and emission characteristics were tested at 1 400 r/min on an electronically controlled high pressure common rail diesel engine.The instantaneous that release rate and combustion temperature were calculated and compared with the straight diesel operation.Results show that methanol can be miscible with diesel and n-pentanol at a certain ratio,and the ratio of mutual solubility increases with the rise of temperature.Compared with the straight diesel operation,the increase of the oxygen content of the blended fuels prolongs the ignition delay and shortens the combustion duration,thus increasing the park combustion temperature.At low and medium loads,the peak combustion heat release rate rises and then decreased at high loads coupled to the increase of diffusion combustion intensity.The fuel consumption of the blended fuel increases with the rise of methanol content,but will improve with thermal efficiency at high loads.The use of three oxygenated fuels results in increased CO emissions at low loads and decreased CO emissions at high loads besides increased HC and NO x emissions and significantly reduced soot emissions.