Microgravity n-Heptane Droplet Combustion in Oxygen-Helium Mixtures at Atmospheric Pressure

Nayagam, Vedha; Haggard, John B.; Colantonio, Renato O.; Marchese, Anthony J.; Dryer, Frederick L.; Zhang, B. L.; Williams, Forman A.

doi:10.2514/2.557

Cited by 78 publications

(6 citation statements)

References 49 publications

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“…Previous studies [19] have shown that the burning of ethanol droplets in microgravity produces soot when higher ambient pressure is combined with higher oxygen concentrations. Once sooting begins at the higher flame temperature (afforded by the oxygen concentration variations) and ambient pressure, the observed sooting trends of ethanol are similar to those observed for n-alkane fuels such as n-heptane [20] and n-decane [21].…”

Section: Introductionsupporting

confidence: 64%

New Insight into the Effects of Gaseous CO2 on Spherically Symmetric Droplet Flames

Hong,

Park

2023

Fire

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This study investigated the effect of CO2 on the burning behavior and radiative properties of a single ethanol droplet flame in microgravity. Measurements of the droplet burning rate, the flame size and temperature, and the radiative emissions were performed, under microgravity conditions for ethanol droplets burning in N2 and CO2 environments, using the 1.5 s drop tower facilities at the Korea Maritime and Ocean University (KMOU). The non-monotonic sooting behaviors (caused by the elevated O2 concentrations) were found to have a significant influence on radiative heat losses in N2 environments, resulting in non-linear droplet burning behaviors with O2 concentrations. Due to the unique nature of CO2 in microgravity, which absorbs radiative energy from the flame and raises the temperatures of the surrounding gases, the CO2 environments suppressed the radiative heat losses from the flame, regardless of the non-monotonic sooting behavior observed at the higher O2 concentrations. These experimental findings highlight the complicated physics of CO2 gas radiation in microgravity, which has not been quantitatively explored.

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Section: Introductionsupporting

confidence: 64%

New Insight into the Effects of Gaseous CO2 on Spherically Symmetric Droplet Flames

Hong,

Park

2023

Fire

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“…This study showed that the initial diameter seemingly has a large e¬ect on the amount of soot produced. Nayagam et al (1999) presented results of experiments on the combustion of freely ®oated n-heptane droplets in 300 K helium{oxygen environments conducted in the Spacelab onboard the Space Shuttle Columbia during the rst launch (STS-83) of the Microgravity Science Laboratory mission in April 1997. These results demonstrated both radiative and di¬usive ®ame extinction during burning, whereas droplet-surface regression followed a d-square-law.…”

Section: Introductionmentioning

confidence: 99%

“…These results demonstrated both radiative and di¬usive ®ame extinction during burning, whereas droplet-surface regression followed a d-square-law. Nayagam et al (1999) also determined soot stand-o¬ ratios as a function of time.…”

Section: Introductionmentioning

confidence: 99%

Effect of thermo– and diffusiophoretic forces on the motion of flame-generated particles in the neighbourhood of burning droplets in microgravity conditions

Ben‐Dor

Elperin

Krasovitov

2003

Proc. R. Soc. Lond. A

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Numerical analysis of the e¬ect of thermo-and di¬usiophoretic forces on the motion of moderately large (0:01 . Kn . 0:3) combustion-generated (soot) particles and on the formation of soot-shell structure in the buoyancy-free spherical droplet ®ames is performed. Transient evaporation, ignition and combustion of a single sootingfuel droplet immersed into a quiescent hot environment are considered, taking into account the e¬ects of radiative heat losses, variable transport properties and the dependence of the droplet surface temperature on time. Results of numerical calculations are compared with available experimental data and recent theoretical models. We calculated thermo-and di¬usiophoretic and total velocities of combustiongenerated particles and showed that soot particles form a size-segregated soot-shell structure. Within a soot shell the particles with smaller radii are located closer to the droplet surface, while larger particles are located closer to the ®ame front. Numerical calculations performed for moderately large soot particles showed that there are two equilibrium locations, where the total velocity is equal to zero, between the droplet and the ®ame front. It is found that one of the equilibrium locations is the point of unstable equilibrium and the other position is the point of stable equilibrium. We numerically determined the dependence of soot-shell-to-droplet-diameter ratios on the particle radius.

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“…Fourth, as soot is prone to appear on the fuel side [17,18], it forms inside the normal SDF and outside the inverse SDF (see Figure 1a,c) [19][20][21]. According to [21], soot forms in the region where the local C/O atomic ratio and local temperature satisfy the conditions 0.32 < C/O < 0.44 and 𝑇 > 1300-1500 K. The phenomenon of radiative flame extinction was also studied for droplet flames [22][23][24][25][26]. Contrary to the SDFs with controlled steady-state fluid supply to the PB, the fuel supply in droplet flames is determined by the rate of liquid vaporization, which is a function of time as well as the properties of liquid and surrounding gas.…”

Section: Introductionmentioning

confidence: 99%

“…The phenomenon of radiative flame extinction was also studied for droplet flames [22][23][24][25][26]. Contrary to the SDFs with controlled steady-state fluid supply to the PB, the fuel supply in droplet flames is determined by the rate of liquid vaporization, which is a function of time as well as the properties of liquid and surrounding gas.…”

Section: Introductionmentioning

confidence: 99%

Spherical Diffusion Flames of Ethylene in Microgravity: Multidimensional Effects

Фролов

Иванов

Фролов

et al. 2023

Fire

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The joint American–Russian Space Experiment Flame Design (Adamant) was implemented on the International Space Station (ISS) in the period from 2019 to 2022. The objectives of the experiment were to study the radiative extinction of spherical diffusion flames (SDF) around a porous burner (PB) under microgravity conditions, as well as the mechanisms of control of soot formation in the SDF. The objects of the study were the normal and inverse SDFs of gaseous ethylene in an oxygen atmosphere with nitrogen dilution at room temperature and pressures ranging from 0.5 to 2 atm. The paper presents the results of transient 1D and 2D calculations of 24 normal and 13 inverse SDFs with and without radiative extinction. The 1D calculations revealed some generalities in the evolution of SDFs with different values of the stoichiometric mixture fraction. The unambiguous dependences of the ratio of flame radius to fluid mass flow rate through the PB on the stoichiometric mixture fraction were shown to exist for normal and inverse SDFs. These dependences allowed important conclusions to be made on the comparative flame growth rates, flame lifetime, and flame radius at extinction for normal and inverse SDFs. The 2D calculations were performed for a better understanding of the various observed non-1D effects like flame asymmetry with respect to the center of the PB, flame quenching near the gas supply tube, asymmetrical flame luminosity, etc. The local mass flow rate of fluid through the PB was shown to be nonuniform with the maximum flow rate attained in the PB hemisphere with the attached fluid supply tube, which could be a reason for the flame asymmetry observed in the space experiment. The evolution of 2D ethylene SDFs at zero gravity was shown to be oscillatory with slow alterations in flame shape and temperature caused by the incepience of torroidal vortices in the surrounding gas. Introduction of the directional microgravity, on the level of 0.01g , led to the complete suppression of flame oscillations.

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Microgravity n-Heptane Droplet Combustion in Oxygen-Helium Mixtures at Atmospheric Pressure

Cited by 78 publications

References 49 publications

New Insight into the Effects of Gaseous CO2 on Spherically Symmetric Droplet Flames

New Insight into the Effects of Gaseous CO2 on Spherically Symmetric Droplet Flames

Effect of thermo– and diffusiophoretic forces on the motion of flame-generated particles in the neighbourhood of burning droplets in microgravity conditions

Spherical Diffusion Flames of Ethylene in Microgravity: Multidimensional Effects

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