Numerical simulation of fuel droplet extinction due to forced convection

Pope, Daniel N.; Gogos, George

doi:10.1016/j.combustflame.2005.02.010

Cited by 35 publications

(25 citation statements)

References 46 publications

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“…Quasi-steady theoretical and numerical models to simulate steady droplet evaporation or combustion are applicable for the low pressure burning of fuel particles, after the initial ignition and internal heating transients are over. Such studies have been reported in the past by researchers [9][10][11][12]. Over the years, detailed kinetics studies on ethanol oxidation have also been reported [13][14][15][16][17].…”

Section: Introductionmentioning

confidence: 62%

“…(6) and converted to mass based value by multiplying it with the molar mass of ethanol. By expressing the concentrations of fuel and oxygen as the respective ratios of the density to the molecular mass, the Da can be calculated following Pope and Gogos [11] …”

Section: Resultsmentioning

confidence: 99%

“…The domain is in polar spherical coordinate system with r and h as the radial and angular coordinates. The details of the governing equations, multicomponent diffusion formulation, implicit time marching solution procedure, and evaluation of variable thermophysical properties are available elsewhere [11]. The fuel has been changed to ethanol.…”

Section: Numerical Modelmentioning

confidence: 99%

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Numerical Modeling of Steady Burning Characteristics of Spherical Ethanol Particles in a Spray Environment

Sahu

Raghavan

Pope

et al. 2011

Journal of Heat Transfer

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A numerical study of steady burning of spherical ethanol particles in a spray environment is presented. A spray environment is modeled as a high temperature oxidizer stream where the major products of combustion such as carbon dioxide and water vapor will be present along with reduced amounts of oxygen and nitrogen. The numerical model, which employs variable thermophysical properties, a global single-step reaction mechanism, and an optically thin radiation model, has been first validated against published experimental results for quasi-steady combustion of spherical ethanol particles. The validated model has been employed to predict the burning behavior of the ethanol particle in high temperature modified oxidizer environment. Results show that based on the amount of oxygen present in the oxidizer the burning rate constant is affected. The ambient temperature affects the burning rate constant only after a sufficient decrease in the oxygen content occurs. In pure air stream, ambient temperature variation does not affect the evaporation constant. Results in terms of burning rates, maximum temperature around the particle, and the evaporation rate constants are presented for all the cases. The variation of normalized Damköhler number is also presented to show the cases where combustion or pure evaporation would occur.

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Section: Introductionmentioning

confidence: 62%

Section: Resultsmentioning

confidence: 99%

Section: Numerical Modelmentioning

confidence: 99%

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Numerical Modeling of Steady Burning Characteristics of Spherical Ethanol Particles in a Spray Environment

Sahu

Raghavan

Pope

et al. 2011

Journal of Heat Transfer

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“…Thus, to achieve more reliable modeling of spray ignition and combustion, the influence of convective gas flow and relative acceleration of droplet and gas phase on the ignition and combustion of fuel droplets has to be investigated. A smaller number of studies deal with the influence of a convective air flow on the ignition or combustion behavior of fuel droplets [16][17][18][19][20][21][22][23][24][25][26][27], although in practical spray combustion devices, droplets are sub-jected to a convective environment. Tsai and Sterling [16] have studied the combustion of linear droplet arrays numerically by a quasi-steady approach with a one-step, finite-rate kinetic model.…”

Section: Introductionmentioning

confidence: 99%

“…Tsai and Sterling [16] have studied the combustion of linear droplet arrays numerically by a quasi-steady approach with a one-step, finite-rate kinetic model. A quasi-steady approach with a one-step overall reaction, including a detailed multicomponent transport model, is also used by Pope and Gogos to study the influence of Lewis number and thermal diffusion effects on the modeling of the combustion behavior [23] as well as to investigate the extinction of n-heptane droplets due to forced convection [24]. The condensation of water during the combustion process and its influence on the evolution of the droplet diameter is studied experimentally in the case of freely falling methanol and ethanol droplets by Lee and Law [17].…”

Section: Introductionmentioning

confidence: 99%

The ignition of methanol droplets in a laminar convective environment

Stauch

Maas

2008

Combustion and Flame

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Numerical simulations of the ignition of methanol droplets in a laminar convective environment are performed using detailed reaction mechanisms and detailed transport models. The flow velocities of the forced convection ranges from 0.01 up to 5 m/s, whereas the ambient gas temperature is varied between 1300 and 1500 K. The ignition delay time of a single droplet is found to decrease with increasing velocity of the convective gas flow. This decrease is attributed to the steepening of the spatial gradients of the profiles of physical variables, such as species mass fractions or temperature. This steepening is originated by a stronger gas flow and leads to a speed-up of the physical transport processes. For the studied flow conditions, an acceleration of the gas flow on the order of the gravitational acceleration does not show a significant influence on the ignition delay time. A downstream movement of the local ignition point with increasing flow velocity is observed. For higher flow velocities, an ignition in the wake of the droplet followed by an upstream flame propagation is found. After ignition, the formation of an envelope flame is detected. The structure of this envelope flame is studied.

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Numerical Investigation of the Time Scales of Single Droplet Burning

Beck

Koch

Bauer

2008

Flow Turbulence Combust

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The effect of gas phase velocity fluctuations on single droplet burning is investigated numerically. The main objective of this study is to understand the effect of gas phase turbulence on nitric oxide formation in single droplet flames. Since the interaction of gas phase velocity fluctuations with droplet burning is of sequential character, a separate investigation of droplet momentum coupling and droplet burning is performed. Momentum coupling controls droplet relaxation against changes of the gas phase velocity along the droplet trajectory and, thereby, determines to what extend gas phase velocity fluctuations translate into droplet slip velocity fluctuations. This coupling effect acts as a high pass filter with a cutoff frequency determined by the droplet Reynolds number and diameter. In the simulation of single droplet burning detailed models for chemical reaction, diffusive species transport and evaporation are used. A significant effect of slip velocity fluctuations on the mean values of NO formation rate is observed. The effect of slip velocity fluctuations on the mean NO formation rate is frequency dependent. The frequency response of the droplet flame is similar to that of a low pass filter. The droplet flame time scale characterizing the response to slip velocity fluctuations is found to correlate with chemical time scales. This time scale is not affected by droplet diameter.

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Numerical simulation of fuel droplet extinction due to forced convection

Cited by 35 publications

References 46 publications

Numerical Modeling of Steady Burning Characteristics of Spherical Ethanol Particles in a Spray Environment

Numerical Modeling of Steady Burning Characteristics of Spherical Ethanol Particles in a Spray Environment

The ignition of methanol droplets in a laminar convective environment

Numerical Investigation of the Time Scales of Single Droplet Burning

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