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The sources of polycyclic aromatic compounds in diesel engine emissions

机译：柴油机废气中多环芳烃化合物的来源

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The application of a radiotracer technique to investigate the sources of polycyclic aromatic hydrocarbons (PAH) in diesel exhaust emissions is described. In separate experiments, ~(14)C radiolabelled naphthalene, fluorene, fluoranthene and pyrene were each added to diesel fuel which was combusted in a 2L direct injection Perkins Prima diesel engine run at steady state under a series of speed (1000-3200 rpm) and load (20-80 N m) conditions. Each PAH was recovered in the exhaust emissions, using a novel sampling system, and its specific activity used to reveal the extent of its survival and pyrosynthesis of the PAH from other fuel fragments. Survival of the PAH varied from below detection limit for fluoranthene at low speed and load to 1.25% for fluorene at high speed and low load. For mid-speed and mid-load conditions, a linear relationship was observed between the extent to which individual PAH survived combustion and the energy level of the lowest unoccupied molecular orbital (LUMO) of the molecule calculated from Hueckel molecular orbital theory. LUMO is an indirect parameter related to gas phase oxidation rates of PAH. Linearity was not so apparent at other speeds and loads. Resynthesis of the PAH varied from less than 0.1% for pyrene at mid-speed and mid-load to 4.93% for naphthalene at high-speed and high-load. Probable mechanisms for the production of some of the pyrosynthetic PAH were discussed.
机译：描述了放射性示踪技术在研究柴油机废气排放中多环芳烃（PAH）来源方面的应用。在单独的实验中，将〜（14）C放射性标记的萘，芴，荧蒽和pyr分别添加到柴油中，该柴油在2L直喷Perkins Prima柴油机中燃烧，该柴油机在一系列速度（1000-3200 rpm）下稳定运行。和负载（20-80 N m）条件。使用新颖的采样系统，从废气中回收了每种PAH，其比活用于揭示PAH的存活程度和从其他燃料碎片中热合成。 PAH的存活率从低速和低负荷荧蒽的检出限以下到高和低负荷的芴检出限的1.25％之间变化。在中速和中等负载条件下，观察到了单个PAH在燃烧中存活的程度与根据Hueckel分子轨道理论计算的分子的最低未占据分子轨道（LUMO）的能级之间的线性关系。 LUMO是与PAH气相氧化速率有关的间接参数。在其他速度和负载下，线性并不是那么明显。 PAH的再合成范围从中速和中等负载的pyr不到0.1％到高速和高负载的萘的4.93％不等。讨论了产生某些焦合成PAH的可能机理。

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