Detailed chemical kinetic reaction mechanisms are developed for combustion of all nine isomers of heptane (C7H16), and these mechanisms are tested by simulating autoignition of each isomer under rapid compression machine conditions. The reaction mechanisms focus on the manner in which the molecular structure of each isomer determines the rates and product distributions

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Experiments in a rapid compression machine have examined the influences of variations in pressure, temperature, and equivalence ratio on the au toigni tion of n-pentane.Equivalence ratios included values from 0.5 to ' 2.0, compressed gas initial temperatures were varied between 675K and 980K, and compresed gas initial pressures varied from 8 to 20 bar. Numerical simulations of the same experiments were carried out using a detailed chemical kinetic reaction mechanism.The results are interpreted in terms of a low temperature oxidation mechanism involving addition of molecular oxygen to alkyl and hydroperoxyalkyl radicals. Idealized calculations are reported which identify the major reaction paths at each temperature. Results indicate that in most cases, the reactive gases experience a two-stage autoigni tion. The first stage follows a low temperature alkylperoxy radical isomerization pathway that is effectively quenched when the temperature reaches a level where dissociation reactions of alkylperoxy and hydroperoxyalkylperoxy radicals are more rapid than the reverse addition steps. The second stage is controlled by the onset of dissociation of hydrogen peroxide. Results also show that in some cases, the first stage ignition takes place during the compression stroke in the rapid compression machine, making the interpretation of the experiments somewhat more complex than generally assumed. At the highest compression temperatures achieved, little or no first stage ignition is observed.

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