On flame bifurcation and multiplicity in consistently propagating spherical flame and droplet evaporation fronts

Zhuang, Yijie; Zhang, Huangwei

doi:10.1016/j.ijmultiphaseflow.2020.103220

Cited by 9 publications

(24 citation statements)

References 48 publications

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“…𝑅 𝑣 corresponds to the location where the droplets are just heated up to boiling temperature and hence start to evaporate. For 𝑅 < 𝑅 𝑣 , the droplet temperature remains constant and evaporation continues [15,[18][19][20][21]. The evaporation onset front 𝑅 𝑣 is always before the flame front 𝑅 𝑓 , indicating that onset of droplet vaporization spatially precedes the gaseous combustion.…”

Section: Physical Modelmentioning

confidence: 99%

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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Section: Physical Modelmentioning

confidence: 99%

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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“…The non-dimensional boundary conditions for both gas phase ( and ) and liquid phase ( ) at the left boundary (spherical centre, = − ) and the right boundary ( → +∞ ) are [2,3,8,11,12] = − : ( + ) 2 = − , = 0, = 0 (5)…”

Section: = ( − ) ( − )mentioning

confidence: 99%

“…In this paper, the fuel droplet is treated as adding to the gaseous mixture, and the overall fuel mass fraction 1+ is still under fuel-lean condition. At the evaporation onset front, = , the gas temperature ( ), fuel mass fraction ( ), and fuel droplet mass loading ( ) satisfy the following jump conditions [2,3,8,11,12]…”

Section: = ( − ) ( − )mentioning

confidence: 99%

“…For the gaseous flames, the well-known diffusive-thermal model [7,8] is adopted. This model has been used in numerous studies on gaseous and two-phase flames [2,[4][5][6]9,10]. One-step chemistry is considered, i.e., 𝐹 + 𝑂 → 𝑃, with F, O and P being fuel vapour, oxidizer and product, respectively.…”

Section: Governing Equation and Boundary Conditionmentioning

confidence: 99%

“…For the latter two, 𝑅 𝑣 corresponds to the location where the droplets are just heated up to boiling temperature and hence start to evaporate. For 𝑅 < 𝑅 𝑣 , the droplet temperature remains constant and evaporation continues [2][3][4][5][6]. The evaporation onset front 𝑅 𝑣 is always before the flame front 𝑅 𝑓 , indicating that onset of droplet vaporization spatially precedes the gaseous combustion.…”

Section: Introduction and Physical Modelmentioning

confidence: 99%

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Forced ignition of laminar premixed spherical flames in evaporating fuel droplet mists

Zhang

2021

ICLASS

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This study aims to build a theoretical model to describe the ignition process of spherical spray flame laden with fuel droplets under overall fuel-lean condition. Two characteristic fronts are introduced to reveal where the evaporation starts and ends in the ignition process. The results demonstrate that the flame has been strengthened with extra fuel droplet adding while the minimum ignition energy (MIE) is decreased. The evolution of the two evaporation fronts in the flame kernel and propagating branches has also be revealed coupled with the evaporation zone length.

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Pulsating propagation and extinction of hydrogen detonations in ultrafine water sprays

Zhang

2022

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On flame bifurcation and multiplicity in consistently propagating spherical flame and droplet evaporation fronts

Cited by 9 publications

References 48 publications

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

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

Forced ignition of laminar premixed spherical flames in evaporating fuel droplet mists

Pulsating propagation and extinction of hydrogen detonations in ultrafine water sprays

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