Effects of endothermic chain-branching reaction on spherical flame initiation and propagation

Li, Haiyue; Zhang, Huangwei; Chen, Zheng

doi:10.1080/13647830.2018.1555338

Cited by 8 publications

(4 citation statements)

References 40 publications

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“…This assumption has been extensively validated by transient numerical simulations for gaseous spherical flames [32,[38][39][40]44], in which the unsteady effects are found to have a negligible influence based on the budget analysis of diffusion, reaction and convection terms in stably propagating spherical flames. Moreover, due to relatively dilute fuel droplet concentration, their influences on the reaction zone thickness are small and therefore gaseous combustion still dominates [24,27].…”

Section: Governing Equationmentioning

confidence: 94%

“…Large activation energy of the gas phase reaction is assumed in this study. This assumption has been successfully used for theoretical analysis of both gaseous [32,38,39,44,47,48] and particle-or droplet-laden [23,24,29,[33][34][35][36] flames. It has been shown to be adequate to predict the main flame dynamics, such as ignition and propagation.…”

Section: Jump and Boundary Conditionsmentioning

confidence: 99%

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Propagation of weakly stretched premixed spherical spray flames in localized homogeneous and heterogeneous reactants

Zhang

Chen

2020

Physics of Fluids

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Propagation of weakly stretched spherical flames in partially pre-vaporized fuel sprays is theoretically investigated in this work. A general theory is developed to describe flame propagation speed, flame temperature, droplet evaporation onset and completion locations. The influences of liquid fuel and gas mixture properties on spherical spray flame propagation are studied. The results indicate that the spray flame propagation speed is enhanced with increased droplet mass loading and/or evaporation heat exchange coefficient (or evaporation rate). Opposite trends are found when the latent heat is high, due to strong evaporation heat absorption. Fuel vapor and temperature gradients are observed in the post-flame evaporation zone of heterogeneous flames. Evaporation completion front location considerably changes with flame radius, but the evaporation onset location varies little relative to the flame front when the flame propagates. For larger droplet loading and smaller evaporation rate, the fuel droplet tends to complete evaporation behind the flame front. Flame bifurcation occurs with high droplet mass loading under large latent heat, leading to multiplicity of flame propagation speed, droplet evaporation onset and completion fronts. The flame enhancement or weakening effects by the fuel droplet sprays are revealed by enhanced or suppressed heat and mass diffusion process in the pre-flame zone. Besides, for heterogeneous flames, heat and mass diffusion in the post-flame zone also exists. The mass diffusion for both homogeneous and heterogeneous flames is enhanced with decreased Lewis number. The magnitude of Markstein length is considerably reduced with increased droplet loading. Moreover, post-flame droplet burning behind heterogeneous flame influences the flame propagation speed and Markstein length when the liquid fuel loading is relatively low.

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Section: Governing Equationmentioning

confidence: 94%

Section: Jump and Boundary Conditionsmentioning

confidence: 99%

Propagation of weakly stretched premixed spherical spray flames in localized homogeneous and heterogeneous reactants

Zhang

Chen

2020

Physics of Fluids

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“…Large activation energy of the gas phase reaction is assumed [22]. Its validity has been confirmed in numerous theoretical analysis of both gaseous [24,32,33,38,40,41] and particle-or droplet-laden [14,15,21,[25][26][27][28] flames. It is adequate to predict the main flame dynamics, such as ignition and propagation.…”

Section: Jump and Boundary Conditionsmentioning

confidence: 85%

“…𝜂 = 𝑟 − 𝑅 𝑓 (𝑡). This assumption has been extensively validated by transient numerical simulations for gaseous spherical flames [24,[32][33][34]38], in which the unsteady effects are found to have a limited influence based on the budget analysis of diffusion, reaction and convection terms in propagating spherical flames. Moreover, due to relatively dilute fuel droplet concentration, their effects on the reaction zone thickness are small and therefore gaseous combustion still dominates [15,19].…”

Section: Governing Equationmentioning

confidence: 96%

On the evolution of fuel droplet evaporation zone and its interaction with flame front in ignition of spray flames

Chen

Zhang

2021

Combustion Theory and Modelling

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Evolution of fuel droplet evaporation zone and its interaction with the propagating flame front are studied in this work. A general theory is developed to describe the evolutions of flame propagation speed, flame temperature, droplet evaporation onset and completion locations in ignition and propagation of spherical flames. The influences of liquid droplet mass loading, heat exchange coefficient (or evaporation rate) and Lewis number on spherical spray flame ignition are studied. Two flame regimes are considered, i.e., heterogeneous and homogeneous flames, based on the mixture condition near the flame front. The results indicate that the spray flame trajectories are considerably affected by the ignition energy addition. The critical condition for successful ignition for the fuel-rich mixture is coincidence of inner and outer flame balls from igniting kernel and propagating flame. The flame balls always exist in homogeneous mixtures, indicating that ignition failure and critical successful events occur only in purely gaseous mixture. The fuel droplets have limited effects on minimum ignition energy, which however increases monotonically with the Lewis number. Moreover, flame kernel originates from heterogeneous mixtures due to the initially dispersed droplets near the spark. The evaporative heat loss in the burned and unburned zones of homogeneous and heterogeneous spray flames is also evaluated, and the results show that for the failed flame kernels, evaporative heat loss behind and before the flame front first increases and then decreases. The evaporative heat loss before the flame front generally increases, although nonmonotonicity exists, when the flame is successfully ignited and propagate outwardly. For heterogeneous flames, the ratio of the heat loss from the burned zone to the total one decreases as the flame expands. Moreover, droplet mass loading and heat exchange coefficient considerably affect the evaporating heat loss from burned and unburned zones.

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Numerical evaluation of the influence of initial pressure/temperature on the explosion properties and soot formation of methane/coal volatiles mixtures

et al. 2023

Fuel

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Effects of endothermic chain-branching reaction on spherical flame initiation and propagation

Cited by 8 publications

References 40 publications

Propagation of weakly stretched premixed spherical spray flames in localized homogeneous and heterogeneous reactants

Propagation of weakly stretched premixed spherical spray flames in localized homogeneous and heterogeneous reactants

On the evolution of fuel droplet evaporation zone and its interaction with flame front in ignition of spray flames

Numerical evaluation of the influence of initial pressure/temperature on the explosion properties and soot formation of methane/coal volatiles mixtures

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