Spray–combustion interaction mechanism of multiple-injection under diesel engine conditions

• Published in: Proceedings of the Combustion Institute Vol. 35; no. 3; pp. 3061 - 3068
• Main Authors: Cung, Khanh, Moiz, Abdul, Johnson, Jaclyn, Lee, Seong-Young, Kweon, Chol-Bum, Montanaro, Alessandro
• Format: Journal Article
• Language: English
• Published: United States Elsevier 01-01-2015
• Subjects: Combustion; Density; Dwell; Formations; Ignition; Pilots; Soot; Sprayers; Sprays
• ISSN: 1540-7489; 1873-2704
• DOI: 10.1016/j.proci.2014.07.054

Multiple-injection has shown significant benefits in the reduction of combustion emissions and soot formation. However, there is a need to understand the secondary flow-induced air-fuel mixture formation and subsequent combustion mechanism under multiple-injection. An experiment was performed by changing the dwell time between the pilot and main injections under the conditions of 23kg/m3 ambient density with 0% O2 (non-combusting) and 15% O2 (combusting) ambient conditions, at an injection pressure of 120MPa. The mass ratios of pilot and main injections in the study were 15/85% and 20/80%. A hybrid shadowgraph and Mie scattering imaging technique in a nearly simultaneous mode along the same line of sight was used to visualize the spray and flame luminosity. Pilot-main spray flame properties including ignition delay, ignition location, and lift-off length were characterized from experimental images. CFD simulation of pilot-main spray combustion was performed under the same experimental conditions to provide additional insights into the combustion process. The air-fuel mixing field and ignition process followed by main injection flame structure are significantly altered at different dwells. The spray-to-flame interaction mechanism model has been established for the development of an optimal multiple-injection scheme for, possibly, low soot formation and emissions.