Experimental Study on Particulate Emission Characteristics of an Urban Bus Equipped with CCRT After-Treatment System Fuelled with Biodiesel Blend

Biodiesel as a renewable energy is becoming increasingly attractive due to the growing scarcity of conventional fossil fuels. Meanwhile, the development of after-treatment technologies for the diesel engine brings new insight concerning emissions especially the particulate matter pollutants. In order to study the coupling effects of biodiesel blend and CCRT (Catalyzed Continuously Regeneration Trap) on the particulate matter emissions, the particulate matter emissions from an urban bus with and without CCRT burning BD0 and BD10 respectively was tested and analyzed using electrical low pressure impactor (ELPI). The operation conditions included steady state conditions and transient conditions. Results showed that the particulate number-size distribution of BD10 and BD0 both had two peaks in nuclei mode and accumulation mode at the conditions of idle, low speed and medium speed while at high speed condition the particulate number-size distribution only had one peak. In addition, under steady state condition, the average PN (particulate number) emission rate decreased approximately 17.8% and average PM (particulate mass) emission rate decreased about 26.3% after the bus was fuelled with BD10. While under transient condition, PN and PM average emission rates of BD10 were less than that of BD0 by about 20.0% and 17.9% respectively. When the bus was equipped with CCRT, its tail-pipe PN concentration decreased substantially both for BD0 and BD10 and the peaks in accumulation mode disappeared. Meanwhile, PN and PM average emission rates decreased more than 94.0% for BD10 and BD0 under both steady and transient conditions and the filtration efficiency was slightly higher for BD10.