生物柴油发动机燃烧火焰与放热过程特性研究

为研究生物柴油与柴油燃烧及放热过程的差异,应用高速摄影采集了柴油机燃用豆油甲酯和柴油的缸内燃烧火焰图像,实测了缸内压力示功图.以直接的火焰辉度图像结合放热规律分析,揭示了生物柴油和柴油缸内燃烧的历程.在未调整发动机燃烧系统参数的前提下,生物柴油因弹性模量大和十六烷值高的综合贡献,使着火时刻较柴油提前1.5°CA,其中生物柴油开始喷油时刻较柴油提前0.7°CA;在速燃期生物柴油燃烧火焰最亮辉度和持续时间均低于柴油.在燃烧的最后阶段,没有明显火焰的化学反应释放出的热量仅占2％ ～3％.

Features of Burning Flames and Heat Release Process of Biodiesel Engine

With the aim to reveal the difference of combustion and heat release process in cylinder of engine fueled with soya methyl ester and petroleum diesel, high speed photography was used to catch combustion flame images in cylinder and thereafter the pressure indicator diagram was collected to compute the heat release rate. The combustion processes of biodiesel and petrolic diesel were illustrated in the crank angle coordinate with the direct flame images combined with analysis of heat release. Due to the contribution of bigger bulk modulus and higher cetane number of biodiesel, the beginning of injection for biodiesel was 0.7°CA earlier than that for diesel, and the ignition time of biodiesel occurred earlier 1.5°CA than that of diesel, under the unimproved conditions of fuel supply system. During the rapid combustion period, both the brightness and its lasting time of biodiesel were less than that of diesel. The heat released by the chemical reactions without obvious flame at the end of combustion only accounted for 2%~3% of the total cycle heat energy released by fuel.