Modelling of heating and evaporation of n-Heptane droplets: Towards a generic model for fuel droplet/particle conversion

Yin, Chungen

doi:10.1016/j.fuel.2014.10.031

Cited by 21 publications

(10 citation statements)

References 29 publications

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“…When the surface temperature of the droplet reaches the vaporization temperature, T vap , and continues until the boiling point, T bP , the instantaneous mass vaporization rate from the droplet surface can be calculated using following equation [16,[20][21][22][23].…”

Section: Droplet Vaporizingmentioning

confidence: 99%

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Dynamic response of vaporizing droplet to pressure oscillation

2016

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inertia of the droplet also plays a considerable role in determining the phase lag. List of symbols A PSurface area of the droplet (m 2 ) B M Spalding mass transfer number B T Spalding heat transfer number C D Drag coefficient C P,F Specific heat of droplet vapor evaluated at the reference conditions in the gas film (J/kg K) C P,g Gas specific heat evaluated at the reference conditions (J/kg K) C P,l Droplet specific heat (J/kg K) D i,m Binary diffusion coefficient evaluated at the reference conditions (m 2 /s)Frequency of fluctuation (Hz) F M Diffusion film thickness correction factor F T Thermal film thickness correction factorGas conductivity valuated at the reference conditions in the gas film (W/m K) k l Droplet conductivity (W/m K) LeLewis numbeṙ mMass vaporization rate (kg/s) m P Droplet mass (kg) M w,i Molecular weight of droplet vapor (kg/kmol) M w,j Molecular weight of ambient gas (kg/kmol) Nu Actual Nusselt number Nu * Modified Nusselt number Nu 0 Nusselt number for the non-vaporizing droplet Abstract Combustion instability is a major challenge in the development of the liquid propellant engines, and droplet vaporization is viewed as a potential mechanism for driving instabilities. Based on the previous work, an unsteady droplet heating and vaporization model was developed. The model and numerical method are validated by experimental data available in literature, and then the oscillatory vaporization of n-Heptane droplet exposed to unsteady harmonic nitrogen atmosphere was numerically investigated over a wide range of amplitudes and frequencies. Also, temperature variations inside the droplet were demonstrated under oscillation environments. It was found that the thermal wave is attenuated with significantly reduced wave intensities as it penetrates deep into droplet from the ambient gas. Droplet surface temperature exhibits smaller fluctuation than that of the ambient gas, and it exhibits a time lag with regard to the pressure variation. Furthermore, the mechanism leading to phase lag of vaporization rate with respect to pressure oscillation was unraveled. Results show that this phase lag varies during the droplet lifetime and it is strongly influenced by oscillation frequency, indicating droplet vaporization is only capable of driving combustion instability in some certain frequency domains. Instead, the amplitude of the oscillation does not have very significant effects. It is noteworthy that thermal

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Section: Droplet Vaporizingmentioning

confidence: 99%

“…Droplet and vapor properties were extracted from the various sources and approximated as a function of the temperature and pressure [23,27].…”

Section: Appendixmentioning

confidence: 99%

Dynamic response of vaporizing droplet to pressure oscillation

2016

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“…The instantaneous energy equations for char combustion are numerically solved by the finite difference method. Gas properties are generally evaluated based on reference conditions . The reference temperature for the computations of gas properties is taken as T ref = (2 T g + T p ) / 3.…”

Section: Solution Procedures and Calculation Conditionsmentioning

confidence: 99%

Char combustion of ellipsoidal particles in a hot gas with fluctuating temperature

Zhang

2016

Can J Chem Eng

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Char combustion of biomass particles is a significant thermo‐chemical conversion process. The char combustion process of biomass particles with gas temperature fluctuation is numerically investigated. Considering the non‐spherical shape of biomass particles, a fully algebraic expression of burning enhancement factor is theoretically derived to modify the char combustion rate of ellipsoidal particles. Four solid biofuel samples (cynara, pinewood, willow, and cardoon) are chosen for the calculations. The instantaneous mass variations and char combustion rates of biomass particles are calculated under different particle sphericities. Different kinetic parameters of biomass samples lead to various effects of gas temperature fluctuation on char combustion. The gas temperature fluctuation generally enhances the char combustion rate. Increasing the fluctuation frequency of gas temperature has no effect on char combustion. Under the same particle surface area, the char combustion rate is enhanced with decreasing particle sphericity.

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“…This represents one of the most severe obstacles for a direct use of pyrolysis oils in furnaces or diesel engines. Different models have been proposed for the evaporation of biooil droplets (Hallett and Clark, 2006;Brett et al, 2007;Zhang and Kong, 2012;Saha et al, 2012;Sazhin et al, 2014;Yin, 2015). Hallett and Clark (2006) presented a numerical model based on a continuous thermodynamics theory to calculate the evaporation of biomass pyrolysis oil droplets.…”

Section: Introductionmentioning

confidence: 99%

“…Hence, the presence of bio-oil in the fuel mixture extends the drop lifetime. Yin (2015) proposed a 2D axisymmetric model to study evaporation of bio-oil droplets. Yin used a finite volume method to numerically solve the flow, heat and mass transfer within the droplet and validated the model against analytical solutions and experimental data of inglecomponent droplet evaporation.…”

Section: Introductionmentioning

confidence: 99%

Effect of char on the combustion process of multicomponent bio-fuel

Mahmoudi

Pozarlik

Weide

et al. 2018

Chemical Engineering Science

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h i g h l i g h t sThe model predicts effect of the solid char on the combustion characteristics of multi-component fuel. An Euler-Lagrange model of three phase gas/liquid/solid combustion has been developed. Gas phase reaches higher temperatures as a result of char combustion. a r t i c l e i n f o b s t r a c tCombustion of pyrolysis oil has attracted many attention in recent years as a renewable and environmental friendly fuel. However, pyrolysis oil as an multi-component fuel has some differences compared to conventional fossil fuels. One of the main differences is the formation of solid char in the droplet during evaporation. The goal of this work is to study the effect of the solid char on the combustion characteristics of multi-component fuel. An Euler-Lagrange model of three phase gas/liquid/solid combustion is developed to study the detailed information about every phenomena in the process such as: heat, mass and momentum transfer between droplet and gas phase, droplet evaporation, homogeneous and heterogeneous reactions. The results indicate that the presence of the solid char and consequently its combustion elongates significantly the combustion region in a typical spray injection chamber/burner. Moreover, the gas phase reaches higher temperatures as a result of char combustion that creates more heat by heterogeneous oxidation as a kind of afterburner.

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Modelling of heating and evaporation of n-Heptane droplets: Towards a generic model for fuel droplet/particle conversion

Cited by 21 publications

References 29 publications

Dynamic response of vaporizing droplet to pressure oscillation

Dynamic response of vaporizing droplet to pressure oscillation

Char combustion of ellipsoidal particles in a hot gas with fluctuating temperature

Effect of char on the combustion process of multicomponent bio-fuel

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