Sub-23nm Particle Emissions from China6 Gasoline Vehicles over Various Driving Cycles

Sub-23nm particles emission from the light-duty vehicle is widely discussed now and possible to be counted into the next stage emission legislation, such as Euro7. In this article, 16 China6 gasoline vehicles were tested over the WLTC and two surrogate RDE lab cycles for particulate number (PN) emission, the difference between PN23 (particle size >23nm) and PN10 (particle size>10nm) emission was analyzed. Testing results showed that the average PN10 emission increased 59% compared to PN23, which will bring great challenges for those vehicles to meet the future regulation requirement if sub-23nm particle is counted. The sub-23nm particles emission was proportional to the PN23 particles emission and generated mostly from the cold start or the transient engine conditions with rich combustion. Compared to the proposal of Euro 7, PN10 emission from some tested vehicles will need further two orders of magnitude reduction. With the adoption of an advanced gasoline particulate filter (GPF) sample, the most challenging vehicle achieved the PN10 emission level of 3.3E10 #/km over the surrogate RDE cycle with GPF filtration efficiency above 99% and fulfilled the potential EU7 requirement.