Comprehensive analysis of toluene/ammonia-air premixed flame: Experimental and kinetic perspectives on laminar burning velocity

Abstract

This study measured the laminar burning velocity (SL) of a toluene/ammonia (A1CH3/NH3) mixture at an initial temperature (Ti) of 400 K, NH3 mole fraction (XNH3) ranging from 0 % to 70 %, and equivalence ratio (ϕ) ranging from 0.8 in to 1.4 in an atmospheric environment. The chemical mechanism of A1CH3/NH3 has been revised and developed using the authors' previous toluene reference fuel (TRF)/NH3 mechanism. The reaction rate of the unimolecular decomposition reaction of A1CH3 and phenol (A1OH) has been modified based on research data. Furthermore, the present model incorporates C-N cross reaction (H-abstraction reaction) of A1CH3 and benzene (C6H6) when attacked by amine (NH2). The new mechanism demonstrates strong agreement with the measured SL of A1CH3/NH3 mixture in this study and in previous researches. Additionally, to enhance the application of NH3 with various hydrocarbon fuels, the effect of NH3 on isooctane (IC8H18) and A1CH3 was compared. The results revealed a greater effect on A1CH3 compared to IC8H18. To further elucidate the disparity between IC8H18 and A1CH3 blends, a sensitivity analysis and reaction pathway analysis were also carried out. The results indicate that H-abstraction reaction of A1CH3 has a more significant effect than IC8H18. Meanwhile, the reaction pathway indicates that the addition of NH3 can promote H-abstraction of IC8H18 and A1CH3. However, the effect on A1CH3 was significantly greater than on IC8H18. The study also examined the effect of H-abstraction reaction on SL. Numerous prior studies have demonstrated that H-abstraction reaction has a minimal effect on flame velocity. Nevertheless, this study has determined that H-abstraction reaction can have a significant effect on the flame velocity of an A1CH3/NH3 mixture, indicating that it should not be disregarded in the chemical kinetic model.