A computational study and correlation of premixed isooctane–air laminar reaction front properties under spark ignited and spark assisted compression ignition engine conditions

• Published in: Combustion and flame 2011-06, Vol.158 (6), p.1089-1096
• Main Authors: Martz, J.B., Middleton, R.J., Lavoie, G.A., Babajimopoulos, A., Assanis, D.N.
• Format: Article
• Language: English
• Subjects: Applied sciences; Combustion. Flame; Energy; Energy. Thermal use of fuels; Exact sciences and technology; HCCI; Isooctane; Laminar burning velocity; Low temperature combustion; Spark assisted compression ignition; Spark ignition; Theoretical studies. Data and constants. Metering
• ISSN: 0010-2180; 1556-2921
• DOI: 10.1016/j.combustflame.2010.09.014

To address the need for reliable premixed laminar burning velocity and thickness information within the spark assisted compression ignition (SACI) combustion regime, a large dataset of simulated reaction fronts has been generated in this work. A transient one dimensional premixed laminar flame simulation was applied to isooctane–air mixtures using a 215 species chemical kinetic mechanism. The simulation was exercised over fuel–air equivalence ratios, unburned gas temperatures and pressures ranging from 0.1 to 1.0, 298 to 1000 K and 1 to 250 bar, respectively, a range that extends beyond that of previous researchers. Steady reaction fronts with burning velocities in excess of 5 cm/s could not be established under all of these conditions, especially when burned gas temperatures were below 1500 K and/or when characteristic reaction front times were on the order of the unburned gas ignition delay. Steady premixed laminar burning velocities were correlated using a modified two-equation form based upon the asymptotic structure of a laminar flame, which produced an average error of 2.5% between the simulated and correlated laminar burning velocities, with a standard deviation of 3.0%. Additional correlations were constructed for reaction front thickness and adiabatic flame temperature. The resulting premixed laminar burning velocity correlation showed good agreement with experiments and existing correlations within the spark-ignited (SI) regime. Analysis of the simulated characteristic reaction front times and ignition delays suggests that homogeneous SACI combustion is most useful under medium and high load operating conditions.