Abstract
The authors have applied flash boiling spray of mixed fuel into premixed charge compression ignition engine to achieve low soot and NO_x emissions while keeping high thermal efficiency because it allows early fuel injection timings without suffering from wall-wetting of fuel or poor mixture preparation. In this case, however, the homogeneous mixture formed causes rapid combustion, leading to combustion noise and knocking issue. To control the heterogeneity of air-fuel mixture and to mitigate the steep heat release, this paper employed a partially premixed charge operation using multiple fuel injections. Through engine tests, better mixture preparation of flashing spray was demonstrated for early injection. Furthermore, the combustion and emissions characteristics of a partially premixed charge operation were evaluated for several combinations of secondary injection timings and the percentages of secondary injection quantity.
