Effect of Ageing Catalyzed Continuously Regenerating Trap on Particulate Emissions from Urban Diesel Bus Based on On-road Test 2014-01-2802

Durability and performance evaluation of the ageing catalyzed continuously regenerating trap (CCRT) on solid and volatile particles from diesel bus were studied through a set of transient TSI engine exhaust particle sizer spectrometer based on on-road test. Particle characteristics under stepped steady conditions and during regeneration were discussed in detail.

Under idle and stepped steady conditions, total particle number and mass Emission Rate (ER) of each test presented rising trends as speed increase. Total number ERs of all tests showed downtrend as the CCRT aging. The particle number size distributions at different ageing stage showed changing characteristics due to developing filter mechanism. Compared with baseline data, the total number reduction rates at idle condition were incremental, from 91.4% to 98.9% as the CCRT ageing. Percentages of nuclei mode concentrations took higher range from 66.6% to 89.9% compared with the baseline data, 43.2-43.7%.

Obvious uncontrolled regenerations were monitored at sudden shift from high-speed to idle, which were dangerous to passengers who were waiting for the bus and should be taken special attention. The particles within the size of 6.04-52.3 nm sharply increased 1-2 order of magnitudes during regeneration. As the CCRT aging, the nuclei mode particles during regeneration made up higher percentage, 90-99%. During regeneration, the average outlet temperatures were about 50°C higher than those before regeneration. As decrease of the filter interspace, it may accumulate less and less soot before next obvious regeneration. Less soot loading resulted in lower temperature gradient, which can promote faster soot oxidation during regeneration. Therefore, the ageing filter needs to endure more frequent and intense thermal shock.