Application study of vegatable oil in DI diesel engine

“生物柴油”（酯交换植物油）作为柴油机的替代燃料已被广泛采用。为了提高油的粘度和蒸馏特性，本研究使用较轻的燃料（汽油或含氧有机化合物）与菜籽油混合。实验旨在阐明混合燃料对喷雾特性、喷射特性、柴油燃烧与排放以及单液滴燃烧的影响。得到的主要结果如下：(1)利用高压和室温下单次注射照片的喷雾图像，分析了气、菜籽油混合物的喷雾形态。因此，使用相同比例的气油和菜籽油，或者使用更高气油比的燃料，喷射角度和穿透度非常接近气油。研究发现，纯菜籽油延长了注油周期，降低了平均注油速率，而50-50气混合菜籽油表现出更接近气混合油的特征。(2)采用悬浮液滴燃烧技术，利用高速摄像机拍摄的图像，分析了气、菜籽油混合物的蒸发和燃烧行为。结果表明，添加25%的气油可显著改善菜籽油的可燃性。烟灰在玻璃纤维过滤器上收集，并用微天平称重。结果表明，生物柴油的烟灰质量约为汽油油滴的三分之一。(3)以2-乙氧基乙醇、2-丁氧基乙醇或二丁基醚（添加量为20 ~ 50 vol%）作为菜籽油的燃料改性添加剂时，高负荷工况下的制动比能耗与汽油相当。结果表明，烟气密度随燃料含氧量的增加呈线性下降。

As an alternative fuel for diesel engines, "biodiesel fuel" (transesterified vegetable oil) has been widely adopted. To improve the oil viscosity and distillation characteristics, the present study used lighter fuels (gas oil or oxygenated Organic compounds) blended with rapeseed oil. The experiments aimed to clarify how the blended fuels influence spray characteristics, injection characteristics, diesel combustion and emissions, and single droplet combustion. The main results obtained are as follows :(1)The spray configurations of gas oil rapeseed oil mixtures were analyzed using spray images in photos taken with single injections at high pressure and room temperature. As a result, equal proportions of gas oil and rapeseed oil or fuels with higher gas oil ratios gave spray angles and penetration very close to gas oil. It was found that neat rapeseed oil prolongs the injection period and decreases the average injection rate while 50-50 gas oil rapeseed oil blend shows characteristics closer to gas oil.(2)With a suspended droplet combustion technique, the evaporation and combustion behaviors of gas oil rapeseed oil blends were analyzed with images taken by a high speed video camera. The results showed that a 25% gas oil addition significantly improves the poor ignitability with rapeseed oil. Soot was collected on a glass fiber filter and the mass was weighed by a micro balance. The results showed that the mass of soot with biodiesel is about one third that of gas oil droplets.(3)When 2-Ethoxyethanol, 2-Butoxyethanol, or Dibutyl ether (20〜50 vol% addition) were used as fuel improving additives for rapeseed oil the brake specific energy consumption were quite similar to gas oil operation at high loads. It was found that the smoke density decreases linearly with increasing oxygen content of the fuel.