(315e) Focusing on What Is Important in Low-Temperature Ignition

Low-temperature ignition delay is an important fuel quality parameter, e.g. it is the basis of the octane number for gasoline and the cetane number for diesel fuel. The autocatalytic chemistry that leads to ignition is rather complicated, often modeled using mechanisms involving more than 1,000 reactions of various peroxy intermediates. Here we analyze what is happening in the various stages of pre-ignition chemistry, and find an underlying simplicity. This provides a better way to look at this important phenomenon. In at least some cases rather simple algebraic formulas are sufficient to predict the ignition delays, given just a few rate and branching coefficients. The possibility of using this simple approach to handle very complicated real fuels with imperfectly known compositions is discussed.