New Observations of Isolated Ethanol Droplet Flames in Microgravity Conditions

Park, Seul-Hyun; Choi, Seung-Hyun; Choi, Mijin; Yozgatlıgil, Ahmet

doi:10.1080/00102200701839022

Cited by 12 publications

(24 citation statements)

References 32 publications

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“…Both experiments were performed at an atmospheric pressure of 0.24 MPa. For diffusion flames, inert additions to the oxidizer side (Guo et al, 2004;McLintock, 1968) or inert substitutions (Park et al, 2008;Yozgatligil et al, 2007) were found to produce distinct burning characteristics in terms of the flame temperature, which is an important parameter that controls soot nanostructure (Ruiz et al, 2007;. For example, the Ar inert experiments produced much higher maximum flame temperature at 2301 K compared to 1850 K measured for the He inert experiments.…”

Section: Influences Of the Flame Temperature On Soot Nanostructurementioning

confidence: 89%

“…The increase in carbon atoms (which results in more graphitic structure) may contribute to the enhanced radiative heat loss for isolated droplet diffusion flames. In previous isolated ethanol droplet combustion experiments in microgravity (Park et al, 2008), the radiative heat loss was found to increase with the initial droplet diameter. In that study, it was believed that the enhanced radiative heat loss attendant with the increase in the initial droplet diameter was due to the large increase in sooting coupled with the increase in the volume of the flame.…”

Section: Soot Nanostructure Of Ethanol Droplet Flames 1179mentioning

confidence: 90%

“…For example, the Ar inert experiments produced much higher maximum flame temperature at 2301 K compared to 1850 K measured for the He inert experiments. The differences in the flame temperature were attributed to the large differences in the heat and species transport properties of each inert gas (Glassman, 1998;Guo et al, 2004;Park et al, 2008). …”

Section: Influences Of the Flame Temperature On Soot Nanostructurementioning

confidence: 99%

“…For these measurements, the package is equipped with the full field light extinction apparatus (which consisted of various optical devices and a high resolution CCD camera), soot sampling assembly, two Kanthal hotwire igniters, fuel delivery system (which consisted of two hypodermic needles, a fuel reservoir and a syringe pump), and radiometer. More details on these experimental apparatuses can be found in other references (Park et al, 2008;Yozgatligil et al, 2004Yozgatligil et al, , 2007. Before the drop sequence, ethanol was pumped by a solenoid-activated microsyringe from a fuel reservoir and delivered through each hypodermic needle.…”

Section: Experimental Descriptionsmentioning

confidence: 99%

“…In the spherically symmetric configuration, the Stefan and fuel mass diffusion velocities are defined as (Park et al, 2008):…”

Section: Influences Of the Residence Time On Soot Nanostructurementioning

confidence: 99%

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Nanostructure of Soot Collected from Ethanol Droplet Flames in Microgravity

Park

Choi

Yozgatlıgil

2009

Combustion Science and Technology

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The nanostructure of soot particles collected from spherically symmetric ethanol droplet flames were analyzed using a high resolution transmission electron microscopy (HRTEM). Nanostructure properties, including fringe length and curvature of carbon lamellae, were measured for soot particles collected in various inert environments. The sampling experiments were performed in the reduced gravity environments produced in the NASA 2.2 sec Droptower at the Glenn Research Center in Cleveland, Ohio. Microgravity droplet combustion experiments provide unique opportunities to vary the residence times over a large range and to independently vary the temperature. In this study, the time-temperature histories experienced by the soot particles were adjusted by means of inert substitutions (argon vs. helium) and variations in the initial droplet diameters (ranging from 1.6 to 2.2 mm). The variations in the initial droplet diameter were found to affect only the residence time necessary for soot inception and growth, whereas inert substitutions modified both residence time and temperature. The measurements of soot nanostructure properties indicated that the higher temperatures produced in the argon inert environment produced more graphitic nanostructures, while the lower temperatures produced in the helium inert environment produced more amorphous nanostructures at the inner core of the soot primary particle. The variations in the initial droplet diameter produced distinct soot nanostructures on the periphery of the soot particle. The higher residence times experienced for the largest initial droplet diameter experiments produced longer carbon lamellae with negligible curvature, while the lower residence times for the smallest initial droplet diameter experiments produced shorter carbon lamellae with higher degrees of curvature. These experimental results provide important foundational understanding of the influence of residence time and temperature on the soot nanostructure that has not been studied previously.

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Section: Influences Of the Flame Temperature On Soot Nanostructurementioning

confidence: 89%

Section: Soot Nanostructure Of Ethanol Droplet Flames 1179mentioning

confidence: 90%

Section: Influences Of the Flame Temperature On Soot Nanostructurementioning

confidence: 99%

Section: Experimental Descriptionsmentioning

confidence: 99%

“…In the spherically symmetric configuration, the Stefan and fuel mass diffusion velocities are defined as (Park et al, 2008):…”

Section: Influences Of the Residence Time On Soot Nanostructurementioning

confidence: 99%

See 3 more Smart Citations

Nanostructure of Soot Collected from Ethanol Droplet Flames in Microgravity

Park

Choi

Yozgatlıgil

2009

Combustion Science and Technology

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Disruptive burning of precursor/solvent droplets in flame‐spray synthesis of nanoparticles

et al. 2013

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Flame spray pyrolysis is an established technique for synthesizing nanoparticles in the gas phase through aerosol combustion of precursor/solvent droplets. The combustion characteristics of isolated micron-sized precursor/solvent droplets are investigated experimentally. Pure solvent droplets burn uniformly and classically quasisteady, whereas precursor/ solvent droplets manifest disruptive combustion behavior. The fast onset of droplet disruption, which occurs only for solutions with dissolved metal precursors, is not due to solid-particle precipitation within the droplet. Instead, the mechanism of disruptive droplet burning is similar to that of slurry droplets, consisting of three main steps: (1) diffusioncontrolled burning of the high-volatile solvent, (2) viscous-shell formation due to decomposition of the low-volatile metal precursor, and (3) subsequent disruption due to heterogeneous nucleation. The time sequence of the three steps depends on the concentration and decomposition characteristics of the metal precursor, shortening with increased concentration and higher incremental decomposition temperature.

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Influences of Residence time of Fuel Vapor Transport on Sooting Behavior of Ethanol Droplet Flames in Microgravity

Park

Choi

2015

Microgravity Sci. Technol.

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New Observations of Isolated Ethanol Droplet Flames in Microgravity Conditions

Cited by 12 publications

References 32 publications

Nanostructure of Soot Collected from Ethanol Droplet Flames in Microgravity

Nanostructure of Soot Collected from Ethanol Droplet Flames in Microgravity

Disruptive burning of precursor/solvent droplets in flame‐spray synthesis of nanoparticles

Influences of Residence time of Fuel Vapor Transport on Sooting Behavior of Ethanol Droplet Flames in Microgravity

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