柴油机燃用菜籽油-柴油混合燃料的试验研究

Experimental investigations of diesel engine fueled with rapeseed oil-diesel blends

文章在一台双缸直喷柴油机上开展了燃用菜籽油-柴油混合燃料时的发动机性能、燃烧和排放特性研究,并与燃用柴油时相比较。研究结果表明:当菜籽油的掺混比(体积分数)不大于20%时,混合燃料的运动粘度和密度接近于柴油;在低负荷工况下,燃用混合燃料时的燃烧开始时间与柴油几乎相同,但缸内压力峰值和放热率相对较高;在高负荷工况下,燃用混合燃料时的燃烧开始时间略早于柴油,特别是VD50;在低负荷工况下,燃用VD50时的燃油消耗率最高,有效热效率最低;随着发动机负荷的逐渐增加,燃用混合燃料与柴油时的燃油油耗率差异逐渐减小,有效热效率也不断提高;在低负荷工况下,燃用混合燃料时的碳烟排放量较高,高负荷时则与之相反;在低负荷工况下,燃用混合燃料时的NOx排放量略低于柴油,高负荷时则几乎相同;在整个负荷范围内,燃用混合燃料时的CO和HC排放量均较高。

The main objective of this paper was to study the performance,combustion and emission characteristics of a two-cylinder direct injection diesel engine using rapeseed oil-diesel blends and compared with that of diesel.The experimental results showed that the viscosity and density of the blends were decreased and approached to that of diesel oil when the volume fraction of rapeseed oil was less than 20%.At low engine loads,the start of combustion for the blends was almost the same as that of diesel,but the peak cylinder pressure and heat release rate were higher.At high engine loads,the the start of combustion for the blends was slightly earlier than that of diesel,especially VD50.At low engine loads,the brake specific fuel consumption of VD50 was the highest and the corresponding thermal efficiency was the lowest.With the increase of engine load,the difference of fuel consumption between the blends and diesel was gradually reduced,and the effective thermal efficiency was also continuously improved.Smoke emission of the blends was higher at low engine loads,but lower at high engine loads.NOx emission of the blends was observed slightly lower at low engine loads and almost identical at high engine loads.CO and HC emission were higher under all range of engine loads for the blends.