Axis-Symmetric Diesel Spray Flame Model Coupled with Momentum Flux Distribution Measurement

抄録

An axis-symmetrical diesel spray flame model coupled with momentum flux distribution measurement was developed as a tool for nozzle orifice development. Momentum flux distributions at several distances from the nozzle orifice exit are measured by a force sensor with a small-diameter aperture which traverses a cross-section, a set distance from the nozzle exit. A theoretical momentum flux profile is determined by fitting with the measured momentum flux profile at the cross-section. The spray velocity profile and equivalence ratio profiles are quantified from the theoretical momentum flux profile. By interpolating the profiles of the measured cross-sections, the axis-symmetrical diesel spray flame model can calculate the equivalence ratio and other physical values as a function of the distance from the nozzle exit (x) and the radius from the spray axis (r). The equivalence ratio distribution in a cross-section involving the spray axis is converted into soot formation and oxidation distribution by coupling with the improved soot φ -T map, which consists of contours of the soot particle diameter and OH mole fraction and shows the border between the soot formation and soot oxidation. The converted soot formation and oxidation regions in the axis-symmetric spray flame model exhibit a strong correlation with the measured soot (KL value) distributions, as determined by two-color pyrometry in a quasi-steady diesel spray flame in an optically accessible engine. The shear-stress, which is an important factor affecting soot formation/oxidation, is also quantified from the velocity distribution.