Isolated n-decane droplet combustion – Dual stage and single stage transition to “Cool Flame” droplet burning

Farouk, Tanvir; Dietrich, Daniel L.; Alam, Fahd E.; Dryer, Frederick L.

doi:10.1016/j.proci.2016.07.015

Cited by 35 publications

(9 citation statements)

References 17 publications

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“…Due to these current practices, an "experimental blind spot" is present in the study of low-temperature oxidation in systems with strong coupling between chemistry, heat release, and transport. However, an unexplored solution exists in the direct measurement of cool flames, which have been found in quasi-steady form under microgravity conditions [69][70][71][72][73][74] and in steady form under the assistance of ozone [14,[75][76][77]. Cool flames possess maximum flame temperatures of 600-1000 K, a range commonly associated with the negative temperature coefficient (NTC) region of hydrocarbon oxidation [78].…”

Section: Introductionmentioning

confidence: 99%

Study of the low-temperature reactivity of large n-alkanes through cool diffusion flame extinction

Reuter

Lee

Won

et al. 2017

Combustion and Flame

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The low-temperature oxidation of hydrocarbon fuels has received increasing attention as advanced engines seek to operate in less conventional combustion regimes. Large n-alkanes are a notable component of many real transportation fuels and possess strong reactivity in this important low-temperature range. These n-alkanes have been studied extensively in various canonical kinetic experiments but seldom in systems with strong coupling between lowtemperature chemistry, transport, and heat release. To address this issue, the present study investigates self-sustaining n-alkane cool diffusion flames in a counterflow burner. The extinction limits of both hot diffusion flames and cool diffusion flames are measured at atmospheric pressure for a range of n-alkanes from n-heptane to n-tetradecane. It is observed that while these fuels behave similarly for hot flames, the larger n-alkanes are substantially more reactive in the low-temperature cool flame regime. Moreover, ozone addition strongly enhances the low-temperature chemistry to the point where the differences in fuel reactivity are nearly suppressed.The experimental measurements are compared with numerical simulations employing both detailed and reduced chemical kinetic models of various sizes. Although the different kinetic models adequately predict the extinction limits of the hot flames, a large scatter is present in the model results for cool flames, and a general overprediction of the measured cool flame extinction limit is observed for all of the fuels studied. This implies that the cool flame heat release is not well agreed upon by the current chemical kinetic models, despite their capability to reproduce many homogeneous reactor experiments at low temperatures. Furthermore, it is observed that the cool flame heat release is spread over a substantial number of reactions involving large molecules, a trait that makes it particularly difficult to create reduced kinetic models that can accurately describe cool flame behavior. The results of this study suggest that the cool flame platform can provide crucial validation of the coupling between chemistry, transport, and heat release in flames at low temperatures. 2 3 4 5 6 7 8

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Section: Introductionmentioning

confidence: 99%

Study of the low-temperature reactivity of large n-alkanes through cool diffusion flame extinction

Reuter

Lee

Won

et al. 2017

Combustion and Flame

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“…The atomization and evaporation of cold fuel provide an ignitable mixture that may undergo a multistage ignition process. Split injection strategies involve a strong spray-combustion interaction, which affects the ignition [121,125], flame structure [126], and soot formation [121,127].…”

Section: Effect Of Spray On Combustionmentioning

confidence: 99%

Spray–turbulence–chemistry interactions under engine-like conditions

Zhou

Zhao

Luo

et al. 2021

Progress in Energy and Combustion Science

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“…The absence of gravity allows to adopt a simple 1D mathematical description and to focus on physical aspects such as differential species diffusion, non-ideal thermodynamics and combustion kinetics. In particular, the implementation of detailed mechanisms for gas-phase chemistry in 1D models has paved the way for a better understanding of low-T chemistry [18,19,20] , ignition and extinction phenomena [21,22].…”

Section: Introductionmentioning

confidence: 99%

DropletSMOKE++: A comprehensive multiphase CFD framework for the evaporation of multidimensional fuel droplets

Saufi¹,

Frassoldati²,

Faravelli³

et al. 2019

International Journal of Heat and Mass Transfer

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This paper aims at presenting the DropletSMOKE++ solver, a comprehensive multidimensional computational framework for the evaporation of fuel droplets, under the influence of a gravity field and an external fluid flow. The Volume Of Fluid (VOF) methodology is adopted to dynamically track the interface, coupled with the solution of energy and species equations. The evaporation rate is directly evaluated based on the vapor concentration gradient at the phase boundary, with no need of semi-empirical evaporation sub-models.The strong surface tension forces often prevent to model small droplets evaporation, because of the presence of parasitic currents. In this work we by-pass the problem, eliminating surface tension and introducing a centripetal force toward the center of the droplet. This expedient represents a major novelty of this work, which allows to numerically hang a droplet on a fiber in normal gravity conditions without modeling surface tension. Parasitic currents are completely suppressed, allowing to accurately model the evaporation process whatever the droplet size. DropletSMOKE++ shows an excellent agreement with the experimental data in a wide range of operating conditions, for various fuels and initial droplet diameters, both in natural and forced convection. The comparison with the same cases modeled in microgravity conditions highlights the impact of an external fluid flow on the evaporation mechanism, especially at high pressures.Non-ideal thermodynamics for phase-equilibrium is included to correctly capture evaporation rates at high pressures, otherwise not well predicted by an ideal gas assumption. Finally, the presence of flow circulation in the liquid phase is discussed, as well as its influence on the internal temperature field. DropletSMOKE++ will be released as an open-source code, open to contributions from the sci-

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Isolated n-decane droplet combustion – Dual stage and single stage transition to “Cool Flame” droplet burning

Cited by 35 publications

References 17 publications

Study of the low-temperature reactivity of large n-alkanes through cool diffusion flame extinction

Study of the low-temperature reactivity of large n-alkanes through cool diffusion flame extinction

Spray–turbulence–chemistry interactions under engine-like conditions

DropletSMOKE++: A comprehensive multiphase CFD framework for the evaporation of multidimensional fuel droplets

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