A turbulent flow reactor has been constructed for kinetic studies of homogeneous gas-phase hydrocarbon oxidation in the low to intermediate temperature regimes (T<1000 K). A unique feature of the test facility is that its design provides the ability to study gas-phase kinetics while minimizing complications from transport effects and temperature gradients at pressures up to 20 atm. A novel experimental procedure designed to map the reactivity of hydrocarbon/air mixtures in the low to intermediate temperature regimes using carbon monoxide measurements as an indicator of the degree of oxidation has been developed.
A pressure dependent kinetic mechanism for propane oxidation is developed and compared to experimental data from a high pressure flow reactor. The . experiment conditions range from 10-15 aim, 650-800 K, and were performed at a residence time of .200 p for propaneair mixtures at an equivalence ratio of 0.4. The experimental results include data on negative temperature coefficient (NTC) behavior, where the chemistry describing this phenomena is considered critical in understanding automotive engine knock and cool flame oscillations. Results of the numerical model are compared.-to a spectrum of stable species profiles sampled . from the flow reactor.Rate constants and product channels for the reaction of propyl radicals, hydroperoxy-propyl radicals and important isomers with 0, were estimated using thermodynamic properties, with multifrequency quantum Kassel Theory for k(E) coupled with modified strong collision analysis for fall-off.Results of the chemical kinetic model show an NTC region over nearly the same temperature regime as observed in the experiments. The model simulates properly,the production of many of the major and minor species observed in the experiments. radicals are in partial equilibrium at 10-15 atm. This indicates that their relative concentrations are controlled by a combination of thermochemistry and rate of minor reaction channels (bleed reactions) rather than primary reaction rates. Major reactions in partial equilibrium include &H7 + 0, = C3H70,, C.,H6o0H = C,H6 + HO, and C.,I&OOH + 0, = O,C,H,OOH. This suggests that thermodynamic parameters of the oxygenated species, which govern equilibrium concentrations, are important. The modeling results show propyl radical and hydroperoxy-propyl Numerical simulations show many of the key reactions involving propylperoxy 2 radicals reaction with 0, proceeds, primarily, through thermalized adducts, not chemically activated channels.
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