Multi-zone modelling of partially premixed low-temperature combustion in pilot-ignited natural-gas engines

Journal Article · Tue Sep 14 04:00:00 EDT 2010 · Proceedings of the Institution of Mechanical Engineers. Part D, Journal of Automobile Engineering

DOI:https://doi.org/10.1243/09544070JAUTO1472· OSTI ID:1079584

Krishnan, S. R. ^[1]; inivasan, K. K.

---

1. Mississippi State University

Detailed results from a multi-zone phenomenological simulation of partially premixed advanced-injection low-pilot-ignited natural-gas low-temperature combustion are presented with a focus on early injection timings (the beginning of (pilot) injection (BOI)) and very small diesel quantities (2-3 per cent of total fuel energy). Combining several aspects of diesel and spark ignition engine combustion models, the closed-cycle simulation accounted for diesel autoignition, diesel spray combustion, and natural-gas combustion by premixed turbulent flame propagation. The cylinder contents were divided into an unburned zone, several pilot fuel zones (or 'packets') that modelled diesel evaporation and ignition, a flame zone for natural-gas combustion, and a burned zone. The simulation predicted the onset of ignition, cylinder pressures, and heat release rate profiles satisfactorily over a wide range of BOIs (20-60° before top dead centre (before TDC)) but especially well at early BOIs. Strong coupling was observed between pilot spray combustion in the packets and premixed turbulent combustion in the flame zone and, therefore, the number of ignition centres (packets) profoundly affected flame combustion. The highest local peak temperatures (greater than 2000 K) were observed in the packets, while the flame zone was much cooler (about 1650 K), indicating that pilot diesel spray combustion is probably the dominant source of engine-out emissions of nitrogen oxide (NO_x). Further, the 60° before TDC BOI yielded the lowest average peak packet temperatures (about 1720 K) compared with the 20° before TDC BOI (about 2480 K) and 40° before TDC BOI (about 2700 K). These trends support experimental NO_x trends, which showed the lowest NO_x emissions for the 60°, 20°, and 40° before TDC BOIs in that order. Parametric studies showed that increasing the intake charge temperature, pilot quantity, and natural-gas equivalence ratio all led to higher peak heat release rates and hotter packets but the pilot quantity and intake temperature affected the potential for NO_x formation to a greater extent.

• Research Organization: Mississippi State Univ., Mississippi State, MS (United States)
• Sponsoring Organization: USDOE Office of Energy Efficiency and Renewable Energy (EERE)
• DOE Contract Number: FG36-06GO86025
• OSTI ID: 1079584
• Report Number(s): DOE/GO--8602562
• Journal Information: Proceedings of the Institution of Mechanical Engineers. Part D, Journal of Automobile Engineering, Journal Name: Proceedings of the Institution of Mechanical Engineers. Part D, Journal of Automobile Engineering Journal Issue: 12 Vol. 224; ISSN 0954-4070; ISSN J. Aut
• Publisher: SAGE
• Country of Publication: United States
• Language: English

Related Subjects

33 ADVANCED PROPULSION SYSTEMS
Shell ignition model
dual-fuel engines
low-temperature combustion
micropilot
natural gas
phenomenological model
pilot ignition