Lawrence Livermore National Laboratory



Iso-cetane (2,2,4,4,6,8,8-heptamethylnonane, C16H34) is a highly branched alkane reference compound for determining cetane ratings. It is also a candidate branched alkane representative in surrogate mixtures for diesel and jet fuels. The kinetic reaction mechanism for iso-cetane was built in the same modular fashion as in previous studies of large straight-chain and branched alkane fuels using the same 25 reaction types and associated rate expressions as first introduced by Curran et al. 1998. The reaction rate rules were updated for iso-octane, and further reaction pathways and reaction rate rules have been proposed, but the present mechanism for iso-cetane is nearly identical to those already tested extensively for other fuel molecules. The model includes both low and high temperature chemical kinetic pathways so that predictions can be made in the negative temperature coefficient region, important for low temperature combustion.

The model has been validated by comparing predicted ignition delay times to measurements made in reflected shock experiments in a heated shock tube for Φ = 0.5, 1.0, and 1.5 iso-cetane/air mixtures at temperatures ranging from 879 to 1347 K and pressures from 8 to 47 atm. These experiments were performed by Oehlschlaeger et al. (2009) at Rensselaer Polytechnic Institute. Computed results from the mechanism are found in good agreement with the experimental measurements.

Reference

M. A. Oehlschlaeger, J. Steinberg, C. K. Westbrook and W. J. Pitz, "The autoignition of iso-cetane at high to moderate temperatures and elevated pressures: Shock tube experiments and kinetic modeling," Combust. Flame, 156 (11) 2165-2172.
http://dx.doi.org/10.1016/j.combustflame.2009.05.007