Emission reduction characteristics of a catalyzed continuously regenerating trap after-treatment system and its durability performance

The primary purpose of this study was to investigate the effect of a catalyzed continuously regenerating trap(CCRT)system composed of a diesel oxidation catalyst(DOC)and a catalyzed diesel particulate filter(CDPF)on the main gaseous and particulate emissions from an urban diesel bus,as well as the durability performance of the CCRT system.Experiments were conducted based on a heavy chassis dynamometer,and a laboratory activity test as well as X-ray photoelectron spectroscopy(XPS)test were applied to evaluate the changes of the aged CCRT catalyst.Results showed that the CCRT could reduce the CO by 71.5%and the total hydrocarbons(THC)by 88.9%,and meanwhile promote the oxidation of NO.However,the conversion rates for CO and THC dropped to 25.1%and 55.1%,respectively,after the CCRT was used for one year(～60,000 km),and the NO oxidation was also weakened.For particulate emissions,the CCRT could reduce 97.4%of the particle mass(PM)and almost 100%of the particle number(PN).The aging of the CCRT resulted in a reduced PM trapping efficiency but had no observable effect on the PN;however,it increased the proportion of nucleation mode particles.The activity test results indicated that the deterioration of the CCRT was directly relevant to the increase in the light-off temperatures of the catalyst for CO,C_3H_8 and NO_2.In addition,the decreased concentrations of the active components Pt~(2+) and Pt~(4+) in the catalyst are also important factors in the CCRT deterioration.     

Occupational safety conditions of bus drivers in Metro Manila,the Philippines

The study looks into the occupational safety and working conditions among bus drivers in Metro Manila, the Philippines. Quantitative data were collected through survey interviews of 95 bus drivers using the stratified sampling technique. Results showed that bus drivers worked an average of 16?h/day and were engaged in risky driving behaviors such as over-speeding and road racing in order to reach their quota for the day. Fifty-nine percent experienced work-related accidents, with a mean of three accidents. The most common accident was hitting another vehicle followed by side swipe. The accidents were blamed on other drivers, followed by vehicle defect, inattentiveness and tiredness/micro-sleep or sudden involuntary sleep while driving. The most common health symptoms experienced by the bus drivers were fatigue, back pain, and cough and colds. This study underlines the need for an occupational health and safety program for bus drivers in the Philippines.     

基于PEMS的柴油公交车排放测试分析

使用车载尾气检测技术PEMS对一辆在用国Ⅲ柴油公交车进行了实际公交线路运行时的气态污染物排放测试,统计得出了车辆运行速度、加速度、气态污染物排放速率、排放因子特性。分析结果表明公交车平均速度为18 km/h,96.9%的速度点落在0~40 km/h的区间段,99%的加速度点落在-1.5~1.5 m/s2的区间段。随着车速的增加,排气污染物排放速率增大,其中NOX排放速率增大显著。车速增大,污染物排放因子降低;低于30 km/h时,车速增大,排放因子降低显著,高于30 km/h时,排放因子随车速增大变化变缓。排放因子受排放速率和车速共同影响。污染物排放速率随加速度增大而增大,加速时的排放速率显著高于减速时的排放速率。研究结果说明,提高车辆运行速度、减少急加速,可以有效降低公交车尾气排放。     

公交车燃用生物柴油的颗粒物排放特性

采用美国TSI公司的EEPS颗粒数量及粒径分析仪,对国Ⅳ排放柴油公交车燃用纯国Ⅳ柴油BD0,纯餐饮废油制生物柴油BD100及国Ⅳ柴油和生物柴油掺混体积比分别为5%、10%、20%、50%的混合燃料(BD5、BD10、BD20、BD50)的颗粒物排放特性进行了试验研究.结果表明,颗粒物数量及质量排放随车速加速度的增加均呈逐渐增加趋势,而随生物柴油掺混比例的增加而降低;不同车速区间下,颗粒物数量排放的粒径分布均呈双峰分布;不同加速度区间下,颗粒物数量排放的粒径分布由减速时的双峰分布逐渐过渡到加速时的单峰分布;随生物柴油掺混比例的增加,聚集态颗粒物数量下降显著,且峰值向小粒径方向移动,核态颗粒物数量变化不大,颗粒物几何平均粒径Dg变小.     

DOC和CDPF对柴油公交车颗粒物组分影响

以一辆柴油公交车为试验样车,在重型底盘测功机上运行中国典型城市公交循环(CCBC),收集尾气颗粒物以分析柴油车安装不同后处理装置的颗粒物组分排放特性.结果表明,原机颗粒物总碳组分中元素碳(EC)比有机碳(OC)多,测得有机组分中,脂肪酸占60.9%,直链烷烃占32.4%,藿烷和PAHs较少.脂肪酸主要是C16:0,C18、C14和C18:1也较多,直链烷烃主要分布于C18~C24,C21H44和C22H46最多.PAHs质量排放以中小分子量为主,Pyr最多,FL和PA也较多,毒性则以中高分子量为主,Ba P毒性最强,B(b+k)F、Ba A以及Icd P也是主要毒性组分.DOC后PAHs总毒性降低2.7%,不同CDPF后总毒性进一步降低89.6%~93.8%.DOC和CDPF对总碳组分的减排率分别为18.9%和70.5%~72.5%,但对不同组分的减排效果差别较大,不同贵金属负载量的CDPF对各组分减排效果无明显影响.