With the use of the Engine Exhaust Particle Sizer (EEPS) developed by TSI, particle size distribution characteristics of China-IV diesel bus fueled biodiesel are studied under real operating condition. Four mixtures of volume ratio between restaurant waste oil and China-IV diesel 5%, 10%, 20%, 50% respectively (marked separately by BD5, BD10, BD20, BD50), pure biodiesel (BD100) and pure diesel (BD0) were tested. The results indicated that the average velocity of diesel bus is 18km/h. Of the entire operating time, idle operating period accounts for 30%, low and medium velocity 58%, and acceleration and deceleration 89%. In different velocity ranges, the size distribution of particulate number emissions (PNSD) is bimodal; in different acceleration ranges, PNSD shows a gradual transition from bimodal shape to unimodal when bus operation switches from decelerating to accelerating status. Biodiesel blended with higher mixture ratios show significant reduction in PN emissions for accumulated modes, and particulate number emission peaks move towards smaller sizes; but little change was obtained in PN emissions for nuclei modes with its particulate size of peak sustains around 10nm.
