1-Methylnaphthalene is a critical component for constructing fuel surrogates of diesel and aviation kerosene. However, the reaction pathways of 1-methylnaphthalene included in existing detailed chemical kinetic models vary from each other, leading to discrepancies in the simulation of ignition and oxidation processes. In the present study, reaction classes and pathways involved in the combustion of 1-methylnaphthalene were analyzed, and effects of rate constants of reactions related to 1-methylnaphthalene and its significant intermediates on ignition delay times and species concentration profiles were discussed, involving hydrogen abstraction and substitution reactions of 1-methylnaphthalene, oxidation, isomerization, and addition reactions of 1-naphthylmethyl, hydrogen abstraction and oxidation reactions of indene, as well as the oxidation of indenyl and naphthalene. On this basis, a new detailed chemical kinetic model for 1-methylnaphthalene was developed, which includes 1389 species and 7185 reactions. The validation of this mechanism shows that it can predict accurately the available experimental ignition delay times, species concentration profiles, and laminar flame speeds of 1-methylnaphthalene. Finally, reaction paths and sensitivity analysis of ignition delay times were performed using the proposed reaction mechanism, and the result shows that the conversion of 1-methylnaphthalene to 1-naphthaldehyde plays an important role in its ignition.

A surrogate fuel model named as T425 was constructed for diesel with 57.5% n-heptane and 42.5% toluene by mole fraction, and then ignition characteristics of stoichiometric methane–T425 mixtures with various methane contents at elevated initial temperatures were investigated at initial pressures up to 30 atm via a shock tube facility. The result shows that behaviors of two reaction mechanisms studied in accurate prediction of ignition of methane–T425 mixture depend on initial pressure and temperature. At higher methane content, more significant change will occur in ignition delay time of the mixture if continually increasing the methane content. In the ignition process, methane is consumed through reactions with radicals in a short time near the ignition time point. Attacks from radicals to n-heptane dominate its consumption, but at initial stage of ignition period the decomposition reaction plays the major role for the consumption of n-heptane. Radicals including H and OH show the control over the consumption of toluene, and such consumption lasts for a relatively longer time compared to methane. When elevating the methane content, decomposition reactions for consumption of n-heptane are promoted, and reactions involving CH₃ are enhanced in oxidation processes of methane and toluene.

Considering that natural gas is the key transition fuel towards the carbon-neutral future, the objective of the present study is to gain insight into evolution features of natural gas-diesel dual fuel during ignition process. Firstly, new experimental data of ignition delay times for the stoichiometric methane/ethane/propane-n-heptane mixtures, which is of significance for validating and optimizing chemical kinetic models of the dual fuel at engine-relevant conditions, were acquired through a shock-tube facility at pressure of 40 atm within temperature range of 1200 to 1600 K, and quantitative influences of components of the fuel mixtures on ignition were determined. Then importance of species including typical radicals and alkenes during ignition processes were identified. Besides, stage characteristics of the fuel mixtures during ignition processes were analyzed. The result shows that the ignition of real natural gas which contains some ethane and propane is greatly different from that of methane. It can be seen that the C2 substances are significant to control ignition of the mixtures. For methane-n-heptane and methane/ethane-n-heptane mixtures, the whole ignition process can be divided into decomposition and oxidation stages. While for the fuel mixtures containing propane and n-heptane, it seems to be more reasonable to divide the whole ignition process into three stages, i.e., decomposition, mixed and oxidation stages.

Iso-cetane serves as an ideal component representing branched-chain alkanes in surrogate fuels for diesel. However, the predictive accuracy of existing detailed chemical kinetic models for iso-cetane requires improvement. In this study, focusing on the reaction processes of iso-cetane and its key intermediates, we first updated the thermodynamic data of iso-cetane and some of its intermediates, systematically analyzed the effects of various reactions on ignition delay time (IDT), and made targeted modifications to the relevant reaction rate constants. The reaction types involved include fuel cracking reactions of iso-cetane, hydrogen abstraction reactions, cracking reactions of fuel radicals, as well as the oxidation of fuel radicals, isomerization of alkylperoxy radicals ($\mathrm{R}{\dot{\mathrm{O}}}_2$), concerted elimination reactions, formation of cyclic ethers, and the formation and decomposition of ketohydroperoxides (KHP). Additionally, reactions related to the formation and consumption of p-alkyl-dihydroperoxides ($\dot{\mathrm{P}}{(\mathrm{OOH})}_2$) were supplemented. Based on the above work, we developed a detailed chemical kinetic model for iso-cetane, comprising 4541 species and 18,359 elementary reactions. Through systematic validation against experimental data on ignition delay time and concentration variations of key species during oxidation, the improved predictive performance of the proposed model was demonstrated. Furthermore, using sensitivity analysis and reaction pathway analysis for the ignition process, we revealed that the formation of the low-temperature negative temperature coefficient (NTC) region for iso-cetane is intrinsically associated with the competition between chain-branching and chain-propagating pathways.