在用国Ⅳ公交车燃用B5生物柴油的排放特性

Emission Characteristics of an In-use China Four Diesel Bus Fueled with B5

以一辆满足国Ⅳ排放的柴油公交车为试验样车,在重型底盘测功机上分别进行燃用柴油和B5生物柴油的中国典型城市公交车循环（CCBC）排放特性试验,分析了该车燃用B5生物柴油CCBC循环的气态物和颗粒物排放特性.结果表明：CCBC循环的发动机工况主要集中在900~1 100r·min-1和200~500N·m,呈明显的低速、中低负荷特征;该车燃用柴油和B5低速行驶的总碳氢（THC）和NO_X、颗粒质量（PM）和颗粒数量（PN）单位里程排放因子较高,高速行驶的CO单位里程排放因子较高.与柴油比较,该车燃用B5的THC和NOX排放增加,CO和PM排放降低,PN排放基本相当.其中,车辆怠速、中低速加速行驶的THC排放率较高,中低速加速行驶的NO_X排放率相对较高,中高速加速、高速匀速行驶的PN较多是导致该车燃用B5的THC,NO_X和PN增加的主要原因.除低、中速加速CO排放较高,低速加速/减速/匀速PM排放率较高之外,其他工况的CO和PM排放降低是导致该车燃用B5的CO和PM降低的主要原因.

The characteristics of particulate matter and gaseous emission from a China-IV diesel bus burning diesel and biodiesel with 5% blend ratio were tested on heavy chassis dynamometer under China City Bus Driving Cycle （CCBC）. The results indicated that the bus working condition under CCBC is mainly during 900～1 100 r · min-1 and 200～500 N · m, which shows the characteristics of low speed and middle-low load. The total hydrocarbon （ THe ）, NOx, particulate matter（PM） and particulate number（PN） emission factor of diesel and biodiesel is higher at low speed, while the CO emission factor is higher at high speed. Compared with diesel, the THC and NOx emission of biodiesel is increasing, while the CO and PM emission is decreasing, and the PN emission of B5 is almost the same with diesel. On the working conditions of idle and middle-low speed acceleration the THC emission rate becomes higher, while the NOx emission rate is higher on the working conditions of middle-low speed acceleration. PN emission rate is much higher on the working conditions of middle-high speed acceleration and high uniform speed. That＇s the reason why THC, NOx, PN emission rates of B5 increase. Except for the higher CO emission rate during middle-low speed acceleration and higher PM emission during low-speed acceleration, deceleration and uniform speed, CO and PM emission on the other working conditions is lower. That＇s the main reason why CO and PM emission of B5 decreases under CCBC.