Particle number emissions from a light-duty diesel engine with biodiesel fuels under transient-state operating conditions

Exhaust particle numbers from a light-duty vehicle diesel engine for transient-state operating conditions were studied. The test fuels were petroleum diesel, pure Jatropha biodiesel (B100), 20% and 50% biodiesel blends with diesel fuel (B20 and B50). The results show that the number of accumulation-mode particles decreases with the biodiesel blend ratio, but the number of nucleation-mode particles increases. The accumulation-mode particle size at peak value decreases with increasing biodiesel blend ratio. The total particle number concentration increases with the biodiesel blend ratio, and the total particle numbers for B20, B50 and B100 biodiesel fuels are approximately 3-4 times that of pure diesel, with the nucleation-mode particle concentration dominating the total particle number. The number of nucleation-mode particles increases when using petroleum diesel during transient operating conditions (increasing torque at constant speeds). The mass of the accumulation-mode particles of the engine with the four kinds of fuels are larger than the nucleation-mode particles under the six operating conditions. The number of accumulation-mode particles increases at the initial stage of transient process and then decreases with increasing torque. The total particle number increases steadily with torque during transient operating conditions, and the accumulation-mode particles dominate the total particle number in the beginning, while nucleation-mode particles dominate the latter stages of transient operating conditions. The change characteristics in particle number during the transient process for lower biodiesel blends are similar to those of petroleum diesel, whereas higher biodiesel blends show distinct differences, and the total particle number and nucleation-mode particle number for B50 and B100 fuels are obviously larger from beginning to end than those for pure diesel, while the accumulation-mode particle number remains smaller. For B100 fuel, the nucleation-mode particle number increases rapidly until the end of the transient process, and the accumulation-mode particle number decreases steadily.