Small Skeletal Kinetic Reaction Mechanism for Ethylene–Air Combustion

Abstract

Ethylene is a fuel considered for high-speed ram- and scramjet combustion applications, mainly because of the short ignition delay time resulting from its high reactivity. Further research and development on these combustion systems would benefit from simulations of large eddy (LES) type, which allow some chemical detail to accurately predict combustion characteristics and pollutant formation. In the present work, a chemical kinetic mechanism suitable for LES is presented, consisting of 66 irreversible reactions between 23 species. The mechanism is extensively validated for combustion characteristics related to ignition and flame propagation over a wide range of pressure, temperature, and equivalence ratios that previously published mechanism of this size have not covered. Agreement with a detailed reference mechanism is good for ignition delay, flame temperature, and laminar burning velocities. In addition, overall concentration profiles of major stable products are in overall good agreement with a reference mechanism. The skeletal mechanism shows an overall good performance in combination with a numerical stability and short computation time, making it highly suitable for combustion LES.

Reduced Chemical Kinetic Reaction Mechanism for Dimethyl Ether-Air Combustion

“…The reactions in the H/C 1 /O submechanism are the same 42 irreversible reactions (reactions 28-69 in Table 3) as in previously presented work by Larsson et al [35], and then later by Zettervall et al [36,41,43,[49][50][51], but with tuning of some rate constants, as noted in Table 3. These adjustments, applied on ten reactions, are mainly made in order to adjust the production and consumption of the radical pool (O, H, OH).…”

“…The reduced reaction mechanism presented here builds on the well-proven mechanism build-up concept used by Zettervall et al [36] on hydrogen (H 2 ), Larsson et al [35] on methane (CH 4 ), and Zettervall et al [49] on ethylene (C 2 H 4 ), propane (C 3 H 8 ) [43] and kerosene (C 12 H 23 ) [41,50,51].…”

“…The reduced mechanism can be sectioned into three subsets: fuel breakdown, intermediate hydrocarbon oxidation and base mechanism. The previous ethylene [49], propane [43] and kerosene mechanisms [41,50,51] and the DME reaction mechanism presented here all use the same set of reactions in their respective H/C 1 /O base mechanism. The intermediate hydrocarbon oxidation submechanism presented here however differs to previous work on the C 2 -C 12 species fuels [43,[49][50][51].…”

“…The previous ethylene [49], propane [43] and kerosene mechanisms [41,50,51] and the DME reaction mechanism presented here all use the same set of reactions in their respective H/C 1 /O base mechanism. The intermediate hydrocarbon oxidation submechanism presented here however differs to previous work on the C 2 -C 12 species fuels [43,[49][50][51]. The intermediate hydrocarbon oxidation section is radically different in order to facilitate the important low-and medium-temperature kinetics that accompany oxygenated biofuels in general and DME in particular.…”

“…The second development target is the ignition delay time, with the specific target conditions summarized in Table 2. The definition of when ignition has occurred is when the temperature has increased by 300 K, matching the rise in pressure and the peak of OH* as explained by Zettervall et al [49]. The complex low-and medium-temperature ignition characteristics of DME compared to short chained alkanes and alkenes mean that even reduced reaction mechanisms must include a considerable number of reactions for describing the low-and medium-temperature process.…”