Effects of exhaust gas recirculation and load on soot in a heavy-duty optical diesel engine with close-coupled post injections for high-efficiency combustion phasing

Abstract

In-cylinder strategies to reduce soot emissions have demonstrated the potential to lessen the burden on, and likely the size and cost of, exhaust aftertreatment systems for diesel engines. One in-cylinder strategy for soot abatement is the use of close-coupled post injections. These short injections closely following the end of the main injection can alter soot-formation and/or oxidation characteristics enough to significantly reduce engine-out soot. Despite the large body of literature on post injections for soot reduction, a clear consensus has not yet been achieved regarding either the detailed mechanisms that affect the soot reduction, or even the sensitivity of the post-injection efficacy to several important engine operating parameters. We report that post injections reduce soot at a range of close-coupled post-injection durations, intake-oxygen levels, and loads in an optical, heavy-duty diesel research engine. Maximum soot reductions by post injections at the loads and conditions tested range from 40% at 21% intake oxygen (by volume) to 62% at 12.6% intake oxygen. From a more fundamental fluid-mechanical perspective, adding a post injection to a constant main-injection for conditions with low dilution (21% and 18% intake oxygen) decreases soot relative to the original main injection, even though the load is increased by the post injection. High-speed visualization of natural combustion luminosity and laser-induced incandescence of soot suggest that as the post-injection duration increases and the post injection becomes more effective at reducing soot, it interacts more strongly with soot remaining from the main injection.

Assessment of improvement of ecological safety of power plants by arranging the system of pollutant neutralization

“…Thus, paper [24] describes the features of operation of DPF with ceramic FE of the cellular structure with longitudinal channels with gas-permiable walls with catalytic coating that are plugged in staggered order at decreased temperature of EG. Article [25] studies the effect of temperature of EG on efficiency of a selective absorber of nitrogen oxides; while article [26] explores its influence on efficiency of application of EG recirculation. Research [27] is devoted to the influence of EG temperature on operation processes in a catalytic oxidizing agent of uncombusted hydrocarbons with netlike-steel FE as parts of DPF.…”

Effect of Load on Close-Coupled Post-Injection Efficacy for Soot Reduction in an Optical Heavy-Duty Diesel Research Engine

“…In this study, post-injection efficacy is measured as a function of load at four intake-oxygen levels. [46]. Although emissions results for four intake-oxygen levels are pre sented, the detailed analysis in this work focuses on the load sweep for the 18% intake-oxygen conditions.…”

“…[46]). 6 and 7 for the single injection baseline, the main-injection soot distribution without a post injection is different for the three load cases; in particular, the spatial extent of the recirculation regions on either side of the jet centerline grows as the load increases.…”

“…[46] may not be the only important interaction mechanisms between the post jet and the main-injection mixture. [46] may not be the only important interaction mechanisms between the post jet and the main-injection mixture.…”

“…In general, post injections are less effective at reducing soot at higher loads for a range of injection schedules and intake conditions [18,28,46]. In general, post injections are less effective at reducing soot at higher loads for a range of injection schedules and intake conditions [18,28,46].…”