Kinetic modeling and experimental investigation of laminar burning velocity in 2- and 3-pentanone/ammonia premixed flames

In recent years, pentanone, a biomass-derived fuel, has attracted significant attention in the field of combustion due to its excellent anti-knock properties and high energy density. To address the low reactivity inherent in ammonia (NH₃) combustion, blending pentanone with NH₃ has emerged as a promising strategy. This study investigates laminar burning velocities (LBVs) of 2-pentanone (nPMK)/NH₃ mixtures at pressures of 1 atm and 3 atm, with a temperature of 448 K and nPMK mole fractions ranging from 0.1 to 1.0. Additionally, building upon the authors’ previous research on 3-pentanone (DEK)/NH₃ mixtures, a comparative analysis was conducted to evaluate the effects of both linear pentanone isomers on NH₃ flame propagation. The kinetic model utilized is an extension of an earlier pentanone-NH₃ model, which has been further refined using the latest experimental data and prior research findings. The results show that blending 50 % DEK with NH₃ can increase LBV by up to 350 % compared to pure NH₃-air mixtures, while nPMK achieves a maximum LBV increase of 300 %, underscoring pentanone's potential to enhance NH₃ combustion performance. Under stoichiometric conditions, the LBV of DEK/NH₃-air mixtures is consistently 3–4 cm/s higher than that of nPMK/NH₃-air mixtures, suggesting that DEK is more effective in improving NH₃ combustion characteristics. Kinetic analysis reveals the difference in LBV is primarily attributable to variations in radical concentrations. Specifically, the position of the carbonyl group in each isomer results in different oxidation intermediates (i.e., CH₃ for nPMK and C₂H₅ for DEK). In nPMK/NH₃-air flames, CH₃ primarily participates in the chain-terminating reaction CH₃ + H(+M) = CH₄(+M), consuming significant quantities of H radicals and suppressing flame propagation. In contrast, C₂H₅ in DEK undergo β-C–H bond scission, generating H radicals that promote flame propagation. Consequently, DEK/NH₃-air mixtures exhibit higher reactivity and faster LBVs.