| The charging mechanism of submicron diesel particles has been studied experimentally and theoretically. Actual charge levels of diesel particles were measured. Three different diesel engines were used: a light-duty VW Rabbit and medium-duty John Deere and Oliver engines.; The volatile and charged fraction were measured as a function of engine load. The charged fractions varied from 20 to 80% by volume, depending on engine load and type. Generally, a higher load gave low volatile fractions and high charged fractions.; Average charge levels of diesel particles were measured at several particle sizes. The measured average charge per particle varied from 1 to 4 elementary charge units as particle diameter varied from 0.047 to 0.266 (mu)m. Essentially, equal concentrations of positively and negatively charged particles were observed for all sizes of particles.; Charged distributions were also measured at several different particle sizes. Charge distributions for particles smaller than 0.133 (mu)m diameter were in good agreement with a Boltzmann equilibrium distribution for a temperature in the 1300-1400K range. However, the larger particles gave progressively broader distributions than Boltzmann equilibrium. |
