Fig.9 Histories of soot formation and oxidation analyzed by the two zone model (θinj = TDC)
Tb (K) is the gas temperature in the burned zone estimated by the present two-zone model analysis. ρs ( = 9,000 kg/m3) is the density of soot particles and ds (m) is the diameter of soot particles, which is assumed to be constant during combustion. P02 (kg/m2) is the partial pressure of oxygen in the burned zone. Trad (K) is the radiation temperature of the burned gas defined in Ref. [10]. Several constants in the above equations are set as follows: A1 = 0.3, A2 = 3,000, B1 = 0.054, B2 = 10,000, where B1 was determined so that the calculated cumulative soot-formation becomes to be equal to the experimental one assuming ds = 0.05 μm under the specified experimental condition of Pme = 0.83 MPa and θinj = TDC in the present experiment.
In the two-zone model analysis, in accordance with the flow charts shown in Figs. 6 and 7, the time history of burned-zone gas temperature and the excess air ratio "λb0" of the burned zone are determined in the first iterative procedure so as to be identical between the calculated NO concentration and the measured one. In the second iterative procedure, the soot particle size "ds" in Eq. (2) is determined under the condition that the calculated cumulative soot-formation is identical to the measured smoke.
