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Co-firing ammonia (NH 3) and hydrogen (H 2) or H 2 -rich fuel and partially cracking NH 3 are promising non-carbon combustion techniques for gas turbines and marine engines, raising a growing need to understand the interactions of H 2 and nitric oxide (NO) as well as the non-hydrocarbon nitrogen oxides (NO X) reduction mechanism under flame conditions. In this work, the outwardly propagating spherical flame method was used to investigate the laminar flame propagation of H 2 /NO and H 2 /NO/nitrogen (N 2) mixtures at initial pressure (P u) of 2 atm, initial temperature (T u) of 298 K and equivalence ratios of 0.2-1.4. The laminar burning velocities (LBVs) of H 2 /NO mixtures are generally 5-10 times lower than those of H 2 /air mixtures, while the dilution of N 2 can dramatically inhibit the laminar flame propagation. A kinetic model of H 2 /NO combustion was constructed and validated against the new data in this work and other types of experimental data in literature. The modeling analyses reveal that NO+H=N+OH becomes the most important chain-branching reaction in H 2 /NO reaction system, while the LBV data of H 2 /NO mixtures in this work can provide highly sensitive validation targets for the kinetics in H 2 and NO interactions. Furthermore, the NO reduction to N 2 mainly proceeds through NO+N=N 2 +O under various H 2 /NO ratios, and NO+O=N+O 2 is found to have a significant contribution to NO reduction under NO-rich conditions. [ABSTRACT FROM AUTHOR]

Laminar flame propagation of branched hexene isomers/air mixtures including 3,3-dimethyl-1-butene (NEC 6 D3), 2,3-dimethyl-1-butene (XC 6 D1) and 2,3-dimethyl-2-butene (XC 6 D2) was investigated using a high-pressure constant-volume cylindrical combustion vessel at 1–10 atm, 373 K and equivalence ratios of 0.7–1.5. The measured laminar burning velocity (LBV) decreases in the order of NEC 6 D3, XC 6 D1 and XC 6 D2, which indicates distinct fuel molecular structure effects. A kinetic model was constructed and examined using the new experimental data. Modeling analyses were performed to reveal fuel-specific flame chemistry of branched hexene isomers. In the NEC 6 D3 and XC 6 D1 flames, the allylic C C bond dissociation reaction plays the most crucial role in fuel decomposition under rich conditions, while its dominance is replaced by H-abstraction reactions under lean conditions. The H-abstraction and H-assisted isomerization reactions are concluded to govern fuel consumption in the XC 6 D2 flame under all investigated conditions. Both C 0 C 3 reactions and fuel-specific reactions are found to be influential to the laminar flame propagation of the three branched hexene isomers. Fuel molecular structure effects were analyzed with special attentions on key intermediates distributions and fuel-specific reactions in all flames. Due to the formation selectivity of key intermediates such as 2-methyl-1,3-butadiene and 2,3-dimethyl-1,3-butadiene, the production of reactive radicals especially H follows the order of NEC 6 D3 > XC 6 D1 > XC 6 D2, which results in the same order of fuel reactivities and LBVs. [ABSTRACT FROM AUTHOR]

Co-firing methane (CH 4) and ammonia (NH 3) has attracted growing concerns as a feasible greenhouse gas reduction strategy in gas turbine-based power generation, which raises the need to better understand the interaction of methane and nitric oxide (NO) under flame conditions. In this work, laminar flame propagation of CH 4 /NO mixtures at initial pressure (P u) of 1 atm, initial temperature (T u) of 298 K and equivalence ratios of 0.4–1.8 was experimentally investigated using a constant-volume combustion vessel. Laminar burning velocities (LBVs) and Markstein lengths were experimentally determined. A kinetic model of CH 4 /NO combustion was developed with rate constants of several important reactions updated, presenting reasonable predictions on the measured LBVs of CH 4 /NO mixtures. The modeling analyses reveal that the reduction of NO can proceed through two mechanisms, i.e. the hydrocarbon NO reduction mechanism and non-hydrocarbon NO reduction mechanism. Among the two mechanisms, the non-hydrocarbon NO reduction mechanism which includes reactions NO+H = N+OH, NO+O = N + O 2 and NO+N = N 2 +O has a higher contribution to NO reduction at the equivalence ratio of 0.6, while the hydrocarbon NO reduction mechanism with hydrocyanic acid (HCN) as the key intermediate plays a more important role at the equivalence ratio of 1.8. NO+ H = N+OH and CH 3 +NO HCN+H 2 O are found to be the two most sensitive reactions to promote the flame propagation, while the LBVs measured in this work are demonstrated to provide strong constraint for these reactions. Furthermore, previous CH 4 /O 2 /NO oxidation data measured in flow reactor and rapid compression machine were also simulated, which provides extended validation of the present model over wider conditions. [ABSTRACT FROM AUTHOR]

In this work, the spherically propagating flame method was applied to the measurements of laminar flame propagation for the flame synthesis precursors. The laminar burning velocities of a typical precursor of silica nanoparticles, i.e. tetramethylsilane (TMS, Si(CH 3) 4), were measured, and a comparative study was carried out on its hydrocarbon counterpart, neopentane. The laminar burning velocities of the two fuels were measured at the initial pressure of 1 atm, initial temperature of 323 K and equivalence ratios of 0.7–1.5. The results show that the laminar burning velocities of TMS are much higher than those of neopentane, showing remarkable fuel molecular structure effects. Kinetic models of TMS and neopentane combustion were constructed and validated against the new experimental data in this work. Based on the rate of production analysis and sensitivity analysis, the critical pathways in the flames of TMS and neopentane were revealed. The fictitious diluent gas method was adopted to provide insight into the fuel molecular structure effects on the laminar burning velocities of TMS and neopentane. It is concluded that the relatively high adiabatic flame temperature of TMS is the driven force of the rapid laminar flame propagation of TMS compared with neopentane, while the chemical effect also promotes the laminar flame propagation of TMS, especially under near stoichiometric conditions. [ABSTRACT FROM AUTHOR]

This work reports an experimental and kinetic modeling investigation on the laminar flame propagation of acetone and 2-butanone at normal to high pressures. The experiments were performed in a high-pressure constant-volume cylindrical combustion vessel at 1–10 atm, 423 K and equivalence ratios of 0.7–1.5. A kinetic model of acetone and 2-butanone combustion was developed from our recent pentanone model [Li et al., Proc. Combust. Inst. 38 (2021) 2135–2142] and validated against experimental data in this work and in literature. Together with our recently reported data of 3-pentanone, remarkable fuel molecular structure effects were observed in the laminar flame propagation of the three C 3 C 5 ketones. The laminar burning velocity increases in the order of acetone, 2-butanone and 3-pentanone, while the pressure effects in laminar burning velocity reduces in the same order. Modeling analysis was performed to provide insight into the key pathways in flames of acetone and 2-butanone. The differences in radical pools are concluded to be responsible for the observed fuel molecular structure effects on laminar burning velocity. The favored formation of methyl in acetone flames inhibits its reactivity and leads to the slowest laminar flame propagation, while the easiest formation of ethyl in 3-pentanone flames results in the highest reactivity and fastest laminar flame propagation. Furthermore, the LBVs of acetone and 3-pentanone exhibit the strongest and weakest pressure effects respectively, which can be attributed to the influence of fuel molecular structures through two crucial pressure-dependent reactions CH 3 + H (+M) = CH 4 (+M) and C 2 H 4 + H (+M) = C 2 H 5 (+M). [ABSTRACT FROM AUTHOR]