The Effects of Injection Timing and Duration on Jet Penetration and Mixing in Multiple-Injection Schedules

Advanced injection schedules involving multiple injections have been utilized for reducing the peak cylinder pressure, phasing heat release rate, and reducing emissions in diesel engines. The timing and duration of the injections determine the injection schedule efficacy at achieving these effects. The goal of this work is to develop tools to track multiple injections to develop a better understanding of interaction mechanisms between subsequent injections. Both timing and duration effects are captured by using three different dwell times and seven injection durations. Experimental gas jet studies are conducted using schlieren. The jet-tip penetration rate, S, results do not reveal significant differences in jet-tip penetration with variations in the first-injection duration and dwell between injections. However, it was found that the jet spreading angles between the first and second injections differed, with the first injection having a higher average angle during the quasi-steady portion of the injection. This is indicative of differences in jet mixing and entrainment between the first and second injection.