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Hydrogen can be blended with other surrogate fuels to avoid its hazard as a highly flammable and explosive gas. The effect of hydrogen addition on the ignition delay times of n -pentane, 3-pentanone, and 1-pentene was investigated by measuring the ignition delay times in a rapid compression machine. The experiments were performed at pressures of 10, 15, and 20 bar, equivalence ratios 0.5 and 1 and for temperatures ranging from 650 to 970 K. The molar ratios of hydrogen in the fuel mixtures were 0, 25 and 50%. The experimental data were simulated using recent models from literature, yielding good agreement. The overall observations conclude to a minor effect of hydrogen addition in the case of n- pentane and 3-pentanone, resulting in a decrease of the reactivity when the mole fraction of hydrogen increases. Hydrogen does however not impact the ignition delay times of 1-pentene significantly. Kinetic analysis is performed to shed light into the processes responsible for this phenomenon. [ABSTRACT FROM AUTHOR]

Cool flames of diethyl ether were stabilized and extensively studied in a stagnation plate burner. Two conditions were selected, enabling the assessment of the impact of ozone-seeding on the cool flame: In the first case, ozone was seeded to stabilize a lean cool flame with an equivalence ratio of 0.5, and in a second case a stoichiometric flame was stabilized without O 3 addition. Excited formaldehyde chemiluminescence (CH 2 O*) was used to measure the cool flame position in the burner. Detailed temperature and mole fraction profiles of stable intermediates of the oxidation of diethyl ether were measured for both conditions. Relevant detailed kinetic models issued from the literature, respectively developed by Tran et al. [Tran et al., Proc. Comb. Inst. 2019, 37, 511–519] and Serinyel et al. [Serinyel et al., Combust. Flame 2018, 193, 453–462] were used in order to improve the understanding of the low temperature kinetics of this ether, as well as the effect of ozone on the species distribution after the cool flame. The Tran et al. model is able to correctly predict the cool flame position as well as its heat release in the lean case, but shows high discrepancy in the prediction of products formation, while the Serinyel et al. model shows a fair prediction of the cool flame products distribution. A numerical comparison between a stoichiometric flame, with and without ozone-seeding, was also performed in order to gain some insight into the ozone influence on the low temperature products distribution. Main results show that the R O ˙ radical decomposition is of particular importance in our conditions, which formation is directly linked to R O ˙ 2 bimolecular reactions, reinforcing the link between atmospheric chemistry and low temperature combustion. [ABSTRACT FROM AUTHOR]

The modern catalytic or enzymatic advances allow the production of novel biofuel. Among them, 1,3-dioxolane can be produced from formaldehyde and ethylene glycol, both can be obtained from biomass. In this study, the oxidation of 1,3-dioxolane is studied at stoichiometric conditions. The ignition delay times of 1,3-dioxolane/O 2 /inert mixtures were measured in a shock tube and in a rapid compression machine at pressures of 20 to 40 bar and temperatures ranging from 630 to 1300 K. The pressure profiles recorded in the rapid compression machine show a first stage of ignition enlightening the influence of the low temperature chemistry of combustion. Furthermore, mole fraction profiles of the stable intermediates produced during the oxidation of 1,3-dioxolane were measured in a jet-stirred reactor at 10 bar. Following these observations, a detailed kinetic model was developed with reaction rate coefficients and thermochemical data calculated by theoretical calculations or estimated by analogies to suitable molecules. In order to get an insight into the most important reaction pathways brute force sensitivity analysis and reaction pathway analysis were performed with the proposed model and discussed. It became clear that in the fuel-in-air case for the alkylhydroperoxide of 1,3-dioxolane the ring opening beta-scission pathway is favored against the further alkane-like second addition to molecular oxygen, which leads to a limited negative temperature coefficient. [ABSTRACT FROM AUTHOR]

As ketene is a crucial intermediate for the high-temperature combustion of oxygenated hydrocarbons in general, an in-depth understanding of its chemistry is a fundamental requirement for the kinetic modeling of bio-based fuels. To gain a profound insight into the decomposition of ketene and subsequent reaction pathways high level ab initio methods were used. DSD-PBEP86/cc-pVTZ level of theory was applied for the geometries and frequencies, while single-point energies were determined at the CCSDT-1a level of theory extrapolated to the basis set limit. The reaction rate parameters for 38 reactions involved in the ketene chemistry including C1 to C4 species like acetylene, ethylene, propyne and allene were computed. For a total of 16 species, the thermochemistry were updated. The calculated rate parameters and the two new species cyclopropenone and 1,4-dioxo-1,3-butadiene were used to update the AramcoMech 3.0 base mechanism, which was then validated against speciation measurements during ketene pyrolysis. A reaction pathway analysis was performed to find the most prominent reactions at the investigated conditions and to discuss the simulation results. A significant improvement in the model's prediction capability was found when applying the newly calculated reaction rate parameter and thermochemical data. [ABSTRACT FROM AUTHOR]

Cyclic ethers are important intermediates in the oxidation of hydrocarbons and biofuels. Studying the oxidation and pyrolysis of cyclic ethers will help in improving our understanding of this functional group and provide consistency to the base mechanism where they play an important role. In this aspect, propylene oxide has been investigated in this study by obtaining ignition delay time measurements in the rapid compression machine and shock tube. The experiments were performed in a range of pressures varying from 10 to 40 bar at different equivalence ratios (0.5–2.0) and dilution percentages. Additionally, speciation measurements in the shock tube at pyrolysis conditions have been performed at a pressure of 40 bar to explore the isomerization pathways. A detailed kinetic mechanism was developed to describe both the oxidation and pyrolysis chemistry of propylene oxide. The mechanism is not only able to predict the data obtained from this study but also reproduces the data from the literature in a consistent trend. For a better understanding of the oxidation and pyrolysis chemistry of propylene oxide, the kinetic analyses were performed using the developed mechanism to comprehend the important reaction pathways and sensitive reactions. At the investigated regime, the consumption of propylene oxide through its isomerization channels is the critical pathway that controls the reactivity of the fuel. [ABSTRACT FROM AUTHOR]