Characterization of Particulate Emissions Propagating in the Exhaust Line for Spark Ignited Engines 2009-01-2654
Upcoming post Euro V legislation suggests particle number regulation not only for diesel engines, but also for other fuels and combustion systems. It is known that particle number emissions from direct injected gasoline engines are higher than diesel engines equipped with diesel particulate filter, therefore it is believed that some particulate reduction aftertreatment will be needed also for these engines to meet the legal requirements. The pioneering objectives here are to characterize particle emissions from two commercially available engine types and understand how they reform during the propagation down the exhaust line.
Particle number and size distribution have been measured at different locations of the exhaust line with a Cambustion DMS500 in the European test cycle. The test series included two four cylinder spark ignited gasoline engines with 2L displacement and power output of approximately 150 hp. One engine was port fuel injected and the other direct injected.
The results show that the choice of injection strategy significantly affects the particulate formation in the combustion chamber. At engine out, a distinct division between nucleation and accumulation mode particles is seen for the Dl engine meanwhile the size distribution curve for the PFI engine has more of a single mode characteristic. The three-way catalytic converter shows good particulate reduction skills. In the size range of 5-1000nm, up to 94% reduction can be seen, most likely related to oxidization of hydrocarbon based volatiles. Hence, nano sized volatiles have a high reduction tendency compared to particles in the accumulation mode.