Towards Surrogate Reaction Model Development

Abstract

The present paper describes the proposed strategy of fuel model design based on identification of chemical and physical criteria for the selection of initial formula of the reference fuel. The first 8 criteria established and studied in previous papers so far are combustion enthalpy, formation enthalpy, molecular weight, C/H-ratio, sooting tendency index, critical point, two-phase diagram, and distillation curve. With these criteria established, the following candidate formula of the kerosene surrogate blend is defined and optimized to adequately mimic the properties of the real fuel: 10% n-propylcyclohexane, 13% iso-octane, 20% n-dodecane, 23% 1-methylnaphthalene, and 32% n-hexadecane. In this work, the ignition delay time has been studied as the next optimization criterion. To keep the model size small, the core reaction mechanism — the skeletal kinetics of n-heptane and iso-octane combustion including aromatics formation, developed earlier — is extended by n-propylcyclohexane, 1-methylnaphthalene, n-dodecane, and n-hexadecane sub-models. The lumped mechanisms for larger n-alkanes are constructed in a similar way to that for n-decane. The n-propylcyclohexane oxidation sub-model is derived from a skeletal mechanism for the low and high temperature cyclohexane oxidation. Reactions for 1-methylnaphthlene oxidation are included in the sub-mechanism for the formation of aromatics up to 5 ringed molecules. The mechanism includes 189 species and 1125 reactions. The proposed sub-models and overall mechanism are validated against experimental data obtained in shock tubes and in jet stirred reactor.s The simulations of ignition delay data for all hydrocarbons and their mixtures, i.e. for kerosene, are in good agreement with the measured data.

Surrogate Model Design for GtL Kerosene

“…Furthermore, lumping techniques has been applied [17] to isomers with equivalent components and to a cascading decomposition chemistry of olefins and alkyl radicals. Details to model validation for ignition delays can be found in [7,16].…”

“…The core detailed reaction model consists of C1-C2 mechanism with poly-aromatic hydrocarbon (PAH) formation reaction model [13,14], nheptane (n-C 7 H 16 ), and iso-octane [15] reaction mechanisms. Further this model include toluene (C 7 H 8 ) oxidation and 1-methylnaphthalene (A2CH 3 ) oxidation, and n-decane (n-C 10 H 22 ), propylcyclohexane (cyC 9 H 18 ), n-dodecane and (n-C 12 H 26 ), and n-hexadecane (n-C 16 H 34 ) oxidation sub-mechanisms [7,16]. The iso-octane (i-C 8 H 18 ) detailed mechanism [15] has been updated with a C 1 -C 4 sub-mechanism [14] and reduced to the skeletal model applying the RedMaster code [16].…”

“…Please note that: two phase diagram is especially important for atomization and evaporation modeling of the fuel spray and definitely has to be included in the set of reference properties for surrogate model design [6,7].…”

“…Previously [6,7] we defined this set of criteria: formation enthalpy, density, C/H ratio, viscosity, sooting tendency index, critical point, distillation curve, laminar flame speeds, and ignition delays. In this paper, the influence of the iso-paraffins to /-normal paraffins ratio will be further considered, see Table 1, to reflect the influence of variations in fuel molecular structure on autoignition.…”

Kinetic Surrogate Model for GTL Kerosene

“…Previously [3,4] we defined this set of criteria to be: formation enthalpy, density, C/H ratio, viscosity, sooting tendency index, critical point, distillation curve, laminar flame speeds, and ignition delays. Recently [2], the Cetane Number (CN) was introduced in the list of criteria to account the ratio of the mono-branched to multi-branched paraffines and to n-paraffins in the IFS optimisation loop.…”