Spontaneous ignition of liquid droplets from a view of non-homogeneous mixture formation and transient chemical reactions

Tanabe, Mitsuaki; Bolik, T.; Eigenbrod, Christian; Rath, H. J.; Sato, Junichi; Kono, Michikata

doi:10.1016/s0082-0784(96)80387-0

Cited by 73 publications

(47 citation statements)

References 5 publications

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“…Large droplets (typically about 1 mm in diameter) are studied in most experimental researches [1][2][3][4][5][6][7][8] to ensure high spatial and temporal resolutions in observation. Such large droplets are strongly affected by natural convection, while fine droplets (typically several-decade m in diameter) are little affected.…”

Section: Introductionmentioning

confidence: 99%

“…It is well known that the low-temperature oxidation reactions, which induce cool flame, are the dominant reactions for spontaneous ignition of most hydrocarbon fuels. 9) Tanabe et al 1) revealed the role of cool flame in the two-stage ignition process (cool-and hot-flame appearances) of n-alkane droplets experimentally through interferometry.…”

Section: Introductionmentioning

confidence: 99%

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Spontaneous Ignition of a Droplet Pair in Microgravity

Moriue

Yamaguchi

Eto

et al. 2010

AEROSPACE TECHNOLOGY JAPAN

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As a fundamental study on the droplet-interaction effect in the fuel-spray ignition, spontaneous ignition of an n-decane droplet pair in hot air was experimentally studied. Two droplets initially at room temperature were brought into a hot furnace at atmospheric pressure. Droplet diameter was 1 mm. Three hot junctions of K-type thermocouples with a diameter of 25 m were located near the droplet pair, and the cool-flame appearance was detected. The experiments were performed in microgravity in order to get rid of the effects of natural convection.Ignition delays and temperatures of cool flame were evaluated from the thermocouple outputs. Backlit droplet images were also recorded, and the vaporization rate was evaluated. Inter-droplet distance was varied, and ambient temperature (hot-air temperature) was fixed at either 600 K or 720 K, where only cool flame appears for n-decane droplets. Generally both cool-flame ignition delay and cool-flame temperature increased with decreasing inter-droplet distance, while cool-flame ignition delay took a minimal value at a certain inter-droplet distance.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Spontaneous Ignition of a Droplet Pair in Microgravity

Moriue

Yamaguchi

Eto

et al. 2010

AEROSPACE TECHNOLOGY JAPAN

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“…Especially, a detailed understanding of the basic physical and chemical processes, such as vaporization, transport, and chemical kinetics, and their interaction is of interest. The ignition or combustion of single droplets in a quiescent atmosphere has been investigated in detail both experimentally and numerically for different fuels, e.g., methanol [1][2][3] and n-heptane [4][5][6][7][8][9][10][11][12][13][14][15], by a large number of research groups. However, in all technical applications, fuel droplets are exposed to a convective environment and to accelerating or decelerating forces.…”

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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“…Many experiments, theoretical analyses and numerical simulations have been done on the ignition of single fuel droplets in ambience with infinite volume as the simplest model of spray ignition. [1][2][3][4][5][6][7][8][9] From studies on ignition of premixed gas, it is well known that certain fuels (often n-alkanes) burn to yield a cool flame under certain conditions with a flame temperature typically lower than 1000 K and with almost no light emission. 10) Countless elementary reactions for the oxidation of such fuels can be divided into two groups: high-temperature reactions, and low-temperature reactions.…”

Section: Introductionmentioning

confidence: 99%

“…Consequently, a stepwise temperature rise occurs. Tanabe et al [4][5][6] observed two-stage ignition even for n-heptane and n-dodecane droplets, showing the importance of the chemical characteristics of fuels, which was previously often ignored for droplet ignition. They visualized the density field around the droplet by Michelson interferometry to observe cool and hot flames, and classified the ignition into three types: only hot-flame ignition, only cool-flame ignition, and two-stage ignition, depending on ambient temperature and pressure.…”

Section: Introductionmentioning

confidence: 99%

Spontaneous Ignition of n-Alkane Droplets with Various Volatility

Moriue

Eigenbrod

Rath

et al. 2004

Trans. Japan Soc. Aero. S Sci.

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Ignition delays of a cool flame ( 1 ) and a hot flame ( t ) were measured experimentally for single n-decane, n-dodecane, n-tetradecane and n-hexadecane droplets, which have similar volatilities to common commercial hydrocarbon fuels, in hot air. Droplet diameter was 0.7 mm. Ambient pressure was 0.3 and 1.0 MPa. Ambient temperature was 550 K to 1000 K. Results show the similarity of the examined fuels in terms of reactivity of the low-and high-temperature reactions. Values of 1 and t were longer for fuels with lower volatility. Values of 2 (¼ t À 1 ) were similar for examined fuels. Both the ignition limits of cool and hot flames were similar between fuels, but were slightly lower for less-volatile fuels.

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Spontaneous ignition of liquid droplets from a view of non-homogeneous mixture formation and transient chemical reactions

Cited by 73 publications

References 5 publications

Spontaneous Ignition of a Droplet Pair in Microgravity

Spontaneous Ignition of a Droplet Pair in Microgravity

The ignition of methanol droplets in a laminar convective environment

Spontaneous Ignition of n-Alkane Droplets with Various Volatility

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