Oxidation and combustion mechanisms of paraffin hydrocarbons: Transfer from C1-C7 to C8H18, C9H20, and C10H22

Abstract

At the present time, detailed kinetic mechanisms (DKMs) for higher hydrocarbons, which include hundreds of particles and thousands of reactions, are proposed. These DKMs have a number of undoubted advantages because they aspire to description of a wide class of phenomena. However, their application, e.g., for modeling of turbulent combustion, is difficult due to their extreme inconvenience. In addition, they are limited to a certain degree and cannot be considered to be comprehensive. As an alternative to such DKMs, we construct no maximum mechanism in this work, but an optimum mechanism of high- and low-temperature oxidation and combustion of normal paraffin hydrocarbons. This mechanism, in accordance with the previously proposed algorithm, contains only general processes that govern the reaction rate and the formation of basic intermediate and final products. A such mechanism has the status of an nonempirical DKM because all parts, including elementary reactions, have kinetic substantiation. The mechanism itself has two features: (i) Reactions of so-called double addition of oxygen (first, to the alkyl radical, then to the isomerized form of the formed peroxide radical) are lacking because the first addition is considered to be sufficient; (ii) Isomeric compounds and their derivative substances as intermediate particles are not considered, because this means of oxidation is slower than through molecules and radicals of the normal structure. The application of the algorithm results in sufficiently compact mechanisms that are important for modeling chemical processes with the participation of paraffin hydrocarbons C n with large n. Previously, this was done for propane, n-butane, n-pentane, n-hexane, and n-heptane; in the present article, it was done for n-octane, n-nonane, and n-decane. The major feature of all the mechanisms is the appearance of stages, viz., cold and blue flames during low-temperature spontaneous ignition. The direct comparison of the calculation and experiment results is carried out.