Combustion Characteristics of Biodiesel Fuel Derived from Waste Edible Oil

本报告研究了纯FAME燃料单液滴对柴油喷射、发动机性能、燃烧特性、排放和其他燃烧特性的影响。实验使用化学试剂、油酸甲酯（OME，C18：1）、月桂酸甲酯（LME，C12：0）以及棕榈酸甲酯（PME，C16：0）与OME或LME的混合物作为基础燃料。（1）在低燃料压力（>40MPa）条件下，通过声速法测定了OME的体积弹性模量，结果表明OME的体积弹性模量比柴油高7%左右。通过测量喷射管中压力上升开始与喷射开始之间的时间差来检查喷射延迟。使用OME和LME时，注入延迟比使用普通瓦斯油时短。(2)发动机实验进行了生物柴油燃料来自未使用的菜籽油，大豆油，棕榈油。阐述了三种原料对发动机性能、燃烧特性和排放的影响。与柴油相比，FAME燃料在高负荷下表现出相似的制动热效率，并且在全负荷条件下烟密度显著降低。PME与LME或OME混合后，着火性能得到明显改善。(3)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FAME液滴的燃烧特性。结果表明，当PME与OME混合时，着火延迟期缩短，燃烧速度增加。在燃烧过程中，在玻璃纤维过滤器上收集形成的烟灰，并通过微量天平称量质量。结果表明，OME的碳烟生成率（定义为碳烟与液滴的质量比）低于柴油液滴的15%。

This report investigated the influence on diesel injection, engine performance, combustion characteristics, emissions, and other characteristics of combustion of single droplets of neat FAME fuels. The experiments used chemical reagents, methyl oleate (OME, C18:1), methyl Laurate (LME, C12:0), and mixtures of methyl palmitate (PME, C16:0) and OME or LME as the base fuels. Notable results obtained are as follows:(1) The bulk modulus was determined by measurements of the speed of sound under low fuel pressure conditions (>40MPa), and the results showed that the bulk modulus of OME was about 7% higher than gas oil. The delay in injection was examined by measuring the time difference between the start of the pressure rise in the injection pipe and the start of injection. With OME and LME there were shorter injection delays than with ordinary gas oil.(2) Engine experiments were carried out with biodiesel fuels derived from unused rapeseed oil, soybean oil, and palm oil. This elucidated the influence on engine performance, combustion characteristics and emissions of the three kinds of raw materials. Compared with gas oil, the FAME fuels showed similar brake thermal efficiencies at high loads, and the smoke densities were significantly lower under whole load conditions. The ignition characteristics were considerably improved when PME was blended with LME or OME.(3) With a suspended droplet combustion technique, the combustion characteristics of FAME droplets were analyzed with images taken by a high speed video camera. It was found that when PME is blended with OME the ignition delay shortens and the speed of combustion increases. During the combustion process, the formed soot was collected on a glass fiber filter and the mass was weighed by a micro balance. The results showed that the soot formation rate(defined as the mass ratio of soot to droplet) with OME is below 15% of that of gas oil droplets.