Abstract: Particle number emission from a vehicle diesel engine during transient operating conditions (Increasing torque at constant speeds) is studied. Test fuels are petroleum diesel fuel, pure biodiesel fuel, B20 and B50 biodiesel blend fuels. The results show the number of nucleation mode particles from the engine increases when using petroleum diesel during the transient operating condition. The number of accumulation mode particles increases at the initial stage of transient process, and then descends with increasing torque. The total particle number increases continuously during the transient operating condition, and accumulation mode particles play an important role in the beginning, and nucleation mode particles dominate the later stage of the transient operating condition. Dynamic characteristics of particle number using B20 biodiesel during the transient process is similar with the petroleum diesel, but B50 and pure biodiesel fuels show distinct difference, and the total particle number and nucleation mode particle number are obviously higher than pure diesel from beginning to end, and the accumulation mode particle number is lower. For the pure biodiesel fuel, the nucleation mode particle number ascends to the end of the transient process, and accumulation mode particle continuously descends.

Key words: Biodiesel, Diesel engine, Emission, Particle number, Transient operating condition