Journal
PROCEEDINGS OF THE COMBUSTION INSTITUTE
Volume 34, Issue -, Pages 3031-3038Publisher
ELSEVIER SCIENCE INC
DOI: 10.1016/j.proci.2012.06.111
Keywords
Jet-jet interaction; Flame stabilization mechanism; Auto-ignition; Flame propagation; Optical engine
Funding
- Competence Center for Combustion Progress (KC-FP) at Lund University
- Swedish National Research Council (VR)
- Swedish National Infrastructure for Computing (SNIC)
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This paper presents a joint numerical and experimental investigation of flame lift-off and stabilization mechanisms in heavy-duty diesel engines. The injection strategy, employing different nozzle configurations, allows for quantification of the impact of varying inter-jet angle spacing in the presence of swirl. For this purpose, three different inter-jet angles are chosen in this study; 45 degrees, 90 degrees and 135 degrees. Large-eddy simulations are performed utilizing a detailed chemical kinetic mechanism for n-heptane to resolve the turbulent fuel and air mixing and to capture the important species surrounding the ignition and flame-fronts to describe the flame stabilization process. Measurements are carried out for OH chemiluminescence to identify the flame lift-off position in an optical accessible engine. In general, the swirl flow in the ambient air shows a great impact on the lift-off, with a 15% difference in the lift-off lengths on the upwind and downwind side of the jet. The LES results show that important ignition reactions undergo in a broad region in front of the lift-off position. With decreasing inter-jet angle, it is shown that the impact of transportation of hot products from adjacent jets becomes more prominent. Hot reservoirs surrounding the lift-off length increase the local ambient temperature and augment the auto-ignition process by mixing of the cold injected fuel and hot air. (C) 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
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