Promotion of the high-temperature autoignition of hydrogen-air and methane-air mixtures by normal alkanes

Abstract

Numerical simulations are performed to examine the effect of small additives of heavy hydrocarbons on the high-temperature autoignition of homogeneous hydrogen-air and methane-air mixtures. The kinetic calculations are carried out using a previously developed detailed mechanism of the oxidation and combustion of normal alkanes. It is shown that the behavior of hydrogen-hydrocarbon-air ternary mixtures is ambiguous. Large hydrocarbon additives of n-heptane and n-hexadecane to a hydrogen-air mixture promote its autoignition at low temperatures and inhibits it at high temperatures, whereas in a definite high-temperature range, small additives of hydrocarbons can promote rather than inhibit the autoignition. The autoignition of methane-air mixtures is promoted by additives of heavy hydrocarbons in all cases.