An Experimental Investigation of In-Cylinder Processes Under Dual-Injection Conditions in a DI Diesel Engine 2004-01-1843
Fuel-injection schedules that use two injection events per cycle (“dual-injection” approaches) have the potential to simultaneously attenuate engine-out soot and NOx emissions. The extent to which these benefits are due to enhanced mixing, low-temperature combustion modes, altered combustion phasing, or other factors is not fully understood. A traditional single-injection, an early-injection-only, and two dual-injection cases are studied using a suite of imaging diagnostics including spray visualization, natural luminosity imaging, and planar laser-induced fluorescence (PLIF) imaging of nitric oxide (NO). These data, coupled with heat-release and efficiency analyses, are used to enhance understanding of the in-cylinder processes that lead to the observed emissions reductions.
Results show that combustion of the early-injected fuel occurs in two phases: a cool-flame phase characterized by very weak chemiluminescence, followed by a premixed-burn phase characterized by localized regions of bright soot incandescence. Combustion of the early-injected fuel liberates only a fraction of its chemical energy. Spray visualization images show that this low combustion efficiency could be due at least in part to liquid fuel penetrating to and wetting in-cylinder surfaces, but NO PLIF images of the early-injection-only case also show strong interferences from unburned fuel vapor and/or condensed fuel droplets, suggesting that incomplete bulk-gas combustion and quenching in crevices also may play roles. The traditional single-injection case produced the highest NO PLIF signal levels. Both dual-injection cases reduced NO PLIF signal levels, with the reduction being most dramatic for the retarded-main-injection case.
Citation: Mueller, C., Martin, G., Briggs, T., and Duffy, K., "An Experimental Investigation of In-Cylinder Processes Under Dual-Injection Conditions in a DI Diesel Engine," SAE Technical Paper 2004-01-1843, 2004, https://doi.org/10.4271/2004-01-1843. Download Citation
Author(s):
Charles J. Mueller, Glen C. Martin, Thomas E. Briggs, Kevin P. Duffy
Affiliated:
Sandia National Laboratories, University of Illinois at Urbana-Champaign, University of Wisconsin - Madison, Caterpillar Inc.
Also in:
New Combustion Systems in Si and Diesel Engines, and Combustion and Emission Formation Processes in Diesel Engines-SP-1890, SAE 2004 Transactions Journal of Engines-V113-3
Related Topics:
Combustion and combustion processes
Imaging and visualization
Particulate matter (PM)
Emissions
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