【摘要】 满足国Ⅳ标准的公交车已被广泛用于北京等大城市,为了评价其相对于国Ⅲ公交车的实际减排效果,使用PEMS(车载排放测试系统)测试了4辆装有SCR(选择性催化还原)系统的国Ⅳ公交车和1辆国Ⅲ公交车在实际运行条件下的污染物排放并进行对比.结果表明:相对于国Ⅲ公交车,装有SCR系统的国Ⅳ公交车在实际运行工况下有效降低了污染物排放,CO、THC和PM分别比国Ⅲ限值降低了60.8%、94.2%和86.2%;但由于实际运行工况中排气温度较低,致使SCR系统效率偏低,只有一辆国Ⅳ公交车NOx排放低于国Ⅲ限值,其他3辆车的NOx排放分别比国Ⅲ限值高187.3%、228.7%和157.3%.国Ⅳ混合动力车的CO2、CO和PM排放比常规动力车分别降低了42.9%、48.8%和89.5%,但NOx排放反而增加了112.1%.实际运行工况下,测试车辆只有12.7%的工况点分布在A转速(1 478 rmin)以上;而ETC工况中在A转速以上的工况点占整个循环的80.5%,造成了满足ETC等型式认证的车辆在实际工况下NOx排放偏高.因此,需要对公交车的实际排放进行有效监督.更多还原

【Abstract】 To reduce urban air pollution,more and more low-emission transit buses have been deployed in cities in China. To assess the effectiveness of the adoption of China Ⅳ buses on emissions reductions,real-world pollutant emissions of four China Ⅳ buses with SCR( selective catalytic reduction) technology,together with one China Ⅲ bus,were measured and analyzed in this study. PEMS( portable emission measurement system) was used for the measurement. The results demonstrate that China Ⅳ buses with SCR had 60. 8% lower CO emissions,94. 2% lower THC emissions,and 86. 2% lower PM emissions compared with the China Ⅲ bus. However,because of the lower conversion efficiency of the SCR systems as a result of a low exhaust temperatures in real-world operating conditions,three of the China Ⅳ buses emitted higher NOxthan the China Ⅲ bus; their NOxemissions were 187. 3%,229. 7% and 157. 3% greater than the limit value of the current China Ⅳ standard. Among the China Ⅳ buses,the hybrid bus emitted 42. 9% less CO2,48. 8% less CO,and 89. 5% less PM. The hybrid bus encountered higher NOxissues as well. Monitoring of the real-world operating conditions showed that the buses were operating at an engine speed higher than A-speed( 1478 r / min) only 12. 7% of the time. However,the percentage is as high as 80. 5% in the ETC testing procedure. The discrepancy between certification cycles like the ETC and real-world operation leads to high NOxemissions under real-world operating conditions. It was concluded that more effective supervision of heavy-duty vehicle emissions should take more real-world operating conditions into consideration.更多还原