柴油引擎為現代重型運輸工具與工業機具設備之主要動力來源；然而，柴油引擎尾氣對人體健康與環境衛生有顯著之不良效應。有鑑於此，本研究旨在探討重型柴油引擎尾氣中之次微米(10-1000 nm)懸浮微粒數量濃度及粒徑分布特性，並評估不同引擎操作條件與控制技術之微粒數量減量效率。受測之條件與技術包括不同負載(扭力)與轉速、油品及尾氣處理設備，而動力計模擬之引擎運轉型態包括惰轉、低、中與高負載等四種穩態及美國暫態循環。採樣系統乃於旋轉盤熱稀釋系統與定容積稀釋系統中，使用掃描式電移動度分徑儀與凝結核計數器(SMPS+C)，量測引擎尾氣中之次微米微粒數量濃度粒徑分布。結果顯示，惰轉受揮發性物質影響最大，故其數量濃度粒徑分布與其它條件相當不同。其餘引擎操作條件，數量濃度隨著負載與轉速增加而增高；波峰眾數粒徑隨扭力增加而增大，但隨轉速增加而減小，且此趨勢不受油品種類影響。相較於市售低硫柴油，無論何種負載之數量濃度隨生質柴油中廢食用油添加比例增加或含硫量減少而降低，但其粒徑分布則受油品影響甚小。不論何種油品與負載，氧化觸媒濾煙器對微粒數量具99%以上之減量效率，且不改變原始粒徑分布。本研究成果預期有助重型柴油引擎尾氣排放之管制策略擬定，及柴油引擎尾氣中微粒數量檢測之技術規範建立。
Diesel engine has been widely used in modern heavy-duty vehicles and nonroad equipments; however, diesel engine exhaust has significant impact on human and environmental health. With that in mind, the objectives of this study are to characterize the submicrometer particle (10-1000 nm) number size distributions in heavy-duty engine exhaust, and to examine the number reduction efficiency with various engine operations and control technologies. Test conditions include various fuel types, aftertreatments and driving conditions. A dynamometer was used to simulate various driving conditions, such as the US transient cycle and steady-state idle, low, medium, and high engine load (torque) and speed. A sequential mobility particle sizer and condensation particle counter (SMPS+C) system was used to measure the number-size distributions of submicrometer particles with a rotating disk thermodiluter and a constant volume sampling system. The results show that the number emission characteristics at idle are strongly affected by semivolatile materials, and hence differ from other engine operations. For each fuel, the particle number concentration increases with increasing load and speed, whereas the mode diameter increases with increasing load and decreasing speed. For each engine load and with respect to regular diesel, the particle number concentration decreases with increasing waste cooking oil biodiesel blends or decreasing sulfur content. The test fuels have negligible effects on the size distribution. For all test operations and fuels, the diesel oxidation catalyst with diesel particulate filter (DOC+DPF) shows number reduction efficiencies of over 99%, and the resulting size distribution is similar to that without the aftertreatment. The outputs of the present study are expected to contribute to the development of diesel engine control strategy and particle number measurement techniques.
