The temporal development of OH-concentration profiles in ignition kernels studied by single-pulse laser induced fluorescence

Berglind, Thomas; Sunner, Jan

doi:10.1016/0010-2180(86)90127-6

Cited by 12 publications

(4 citation statements)

References 22 publications

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“…In this temperature region, the temperature-sensitive hydrogen abstraction from the collision of CH 4 molecules with atomic oxygen fragments becomes efficient (ref. 22 ), producing OH radicals through the reaction: …”

Section: Discussionmentioning

confidence: 99%

“…Associating with OH radical formation, chain-branching oxidation reactions start, and finally, combustion occurs, resulting in a flame. It should be noted that there is another reaction routine producing OH radicals by methane pyrolysis 22 . However, this path is not efficient until the gas temperature exceeds 2500 K. Therefore, the contribution of thermal decomposition to producing OH radicals in ultrashort LI can be neglected.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, inside the fs laser filament, although the initial temperature of gas molecules determined through various energy deposition pathways, such as multiphoton/tunnel ionization, dissociation, Raman excitation, and collision excitation [16][17][18][19][20][21] , is only~1400 K (ref. 16 ), the lowtemperature oxidation reaction of methane molecules can still occur 22 , which may allow for the initiation of combustible chemical reactions.…”

Section: Introductionmentioning

confidence: 99%

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Robust and ultralow-energy-threshold ignition of a lean mixture by an ultrashort-pulsed laser in the filamentation regime

Zang

Zhang

et al. 2021

Light Sci Appl

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Laser ignition (LI) allows for precise manipulation of ignition timing and location and is promising for green combustion of automobile and rocket engines and aero-turbines under lean-fuel conditions with improved emission efficiency; however, achieving completely effective and reliable ignition is still a challenge. Here, we report the realization of igniting a lean methane/air mixture with a 100% success rate by an ultrashort femtosecond laser, which has long been regarded as an unsuitable fuel ignition source. We demonstrate that the minimum ignition energy can decrease to the sub-mJ level depending on the laser filamentation formation, and reveal that the resultant early OH radical yield significantly increases as the laser energy reaches the ignition threshold, showing a clear boundary for misfire and fire cases. Potential mechanisms for robust ultrashort LI are the filamentation-induced heating effect followed by exothermal chemical reactions, in combination with the line ignition effect along the filament. Our results pave the way toward robust and efficient ignition of lean-fuel engines by ultrashort-pulsed lasers.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Robust and ultralow-energy-threshold ignition of a lean mixture by an ultrashort-pulsed laser in the filamentation regime

Zang

Zhang

et al. 2021

Light Sci Appl

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“…Although the ignition process by the capacitance spark has been intensively studied for some flammable mixtures [1], [4]- [7], two important parameters, the density of radicals and the gas temperature, have not been sufficiently measured in the ignition process of the mixtures. Only a few researchers have measured the relative density of radicals in the incipient flame [8]- [10], in which other types of discharges than the capacitance spark were used for ignition. As a result, the ignition process by the capacitance spark is not fully understood yet.…”

Section: Introductionmentioning

confidence: 99%

Measurement of OH Density and Gas Temperature in Incipient Spark-Ignited Hydrogen-Air Flame

Ono¹,

Saito²,

Maekawa³

et al. 2007

2007 IEEE Industry Applications Annual Meeting

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For investigating the spark ignition process of hydrogen-air mixture, density of OH radicals and gas temperature are measured in the incipient spark-ignited hydrogen-air flame using laser-induced predissociation fluorescence (LIPF). The spark discharge occurs between a 2-mm gap with approximately 10 ns pulse duration. Hydrogen-air mixture is ignited by spark discharge of E = 1.2 ∼ 1.4E min, where E is the spark energy and E min is the minimum ignition energy. In hydrogen(50%)-air mixture ignited with E = 1.35E min, OH density decreases after the spark discharge from 2 × 10 16 cm −3 (t = 0 µs) to 2 × 10 15 cm −3 (t = 100 µs), where t is the postdischarge time. On the other hand, the gas temperature is 900 K at t = 30 µs and 1400 K at t = 200 µs. Hydrogen(15%)-air mixture ignited with E = 1.40E min also shows the similar tendency to the hydrogen(50%)-air mixture. In stoichiometric (hydrogen(30%)-air) mixture (E = 1.25E min), OH density is approximately constant at 2 × 10 16 cm −3 for 150 µs after the spark discharge, and the gas temperature increases from 1100 K (t = 0 µs) to 1800 K (t = 150 µs). They are higher than those of other mixtures (15% and 50% hydrogen). It indicates that the reaction in the stoichiometric flame proceeds faster than other flame.

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Goldilocks focal zone in femtosecond laser ignition of lean fuels

Zang

Liang

et al. 2022

Sci. China Technol. Sci.

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The temporal development of OH-concentration profiles in ignition kernels studied by single-pulse laser induced fluorescence

Cited by 12 publications

References 22 publications

Robust and ultralow-energy-threshold ignition of a lean mixture by an ultrashort-pulsed laser in the filamentation regime

Robust and ultralow-energy-threshold ignition of a lean mixture by an ultrashort-pulsed laser in the filamentation regime

Measurement of OH Density and Gas Temperature in Incipient Spark-Ignited Hydrogen-Air Flame

Goldilocks focal zone in femtosecond laser ignition of lean fuels

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