Soot Emission Behavior from Diverse Vehicles and Catalytic Technologies Measured by a Solid Particle Counting System

A Solid Particle Counting System (SPCS) has been developed according to the ECE draft regulation proposed by the particle measurement program (PMP). In the previous report the basic performance of the SPCS has been mentioned in detail [1, 2, 3, 4, 5 and 6]. It has been reported that the SPCS demonstrates very stable dilution of sample with air and the error of real time dilution factor is less than 6% up to the total dilution factor of 1000. Penetration of solid particles through the SPCS is over 95% and volatile particles removal efficiency is over 99%.

In this study the SPCS has been used to investigate the soot emission behavior from different vehicles with different after-treatment technologies. Direct injection (DI) diesel vehicles without diesel particulate filter (DPF), and with different DPFs (catalyzed and non-catalyzed) have been tested. Direct injection gasoline (DIG) vehicle with oxidation and NOx reduction catalysts have also been tested. Tests were performed in different chassis dynamometer test cells under New European Driving Cycle (NEDC), for both hot and cold start conditions. Exhaust gas was diluted via full flow dilution tunnels. A cyclonic classifier with 2500 nm (D₅₀) cut point was used to eliminate the coarse mode particles.

It was found that all the tested DI diesel vehicles with DPF emit about 90% of the total soot particles within initial 200 seconds of the driving cycle when driven under NEDC in cold start condition. Similar trend can be seen in some other driving cycles (Japanese JC08). Once the vehicle and the DPF system becomes warmed-up, soot emission decreases drastically. Compared to a DI diesel vehicle fitted with DPF, a DI gasoline vehicle without DPF tested in this study emits higher number of particles. In this case soot particle emission occurs continuously during the entire driving cycle rather than emitting at a particular time independent of the driving cycle.