Reaction propagation modes in millimeter-scale tubes for ethylene/oxygen mixtures

Wu, Mei‐Feng; Wang, Chan Yu

doi:10.1016/j.proci.2010.07.081

Cited by 96 publications

(36 citation statements)

References 34 publications

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“…In the present analyses, the time from the first autoignition (not always easy to identify) to a steady detonation front, largely owing to the influence of the secondary shock wave in inducing further autoignition, was as low as approximately 0.1 ms. This compares with a similar time observed in the study of Babkin & Kozachenko [31] and of 0.04 ms in the study of Wu & Wang [32], all of which are less than might have been anticipated for a uniform, homogeneous, autoignition.…”

Section: Flame Propagation Along a Duct And The Transition To Detonationsupporting

confidence: 86%

“…Wu & Wang [32] have reported DDTs in stoichiometric ethylene-oxygen mixtures, under initially atmospheric conditions. Contrary to what is suggested by equations (5.4) and (6.4), the CJ speed was more rapidly attained in the smaller diameter tubes.…”

Section: Values Of the Turbulent Burning Velocitymentioning

confidence: 99%

“…In equation ( Comparisons of the computed values of u t , in this case a laminar burning velocity, in table 3 were hindered by the lack of data on stoichiometric ethylene-oxygen laminar burning velocities, particularly at high temperatures and pressures. In the study of Wu & Wang [32], u l was taken to be 5.5 m s −1 under atmospheric conditions. Some data on the variations of u l for ethylene-air with temperature are given by Kumar et al [49] and with pressure by Egolfopoulos et al [50] and Jomaas et al [51].…”

Section: Values Of the Turbulent Burning Velocitymentioning

confidence: 99%

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Autoignitions and detonations in engines and ducts

Bradley

2012

Phil. Trans. R. Soc. A.

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The origins of autoignition at hot spots are analysed and the pressure pulses that arise from them are related to knock in gasoline engines and to developing detonations in ducts. In controlled autoignition engines, autoignition is benign with little knock. There are several modes of autoignition and the existence of an operational peninsula, within which detonations can develop at a hot spot, helps to explain the performance of various engines. Earlier studies by Urtiew and Oppenheim of the development of autoignitions and detonations ahead of a deflagration in ducts are interpreted further, using a simple one-dimensional theory of the generation of shock waves ahead of a turbulent flame. The theory is able to indicate entry into the domain of autoignition in an 'explosion in the explosion'. Importantly, it shows the influence of the turbulent burning velocity, and particularly its maximum attainable value, upon autoignition. This value is governed by localized flame extinctions for both turbulent and laminar flames. The theory cannot show any details of the transition to a detonation, but regimes of eventually stable or unstable detonations can be identified on the operational peninsula. Both regimes exhibit transverse waves, triple points and a cellular structure. In the case of unstable detonations, transverse waves are essential to the continuing propagation. For hazard assessment, more needs to be known about the survival, or otherwise, of detonations that emerge from a duct into the same mixture at atmospheric pressure.

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Section: Flame Propagation Along a Duct And The Transition To Detonationsupporting

confidence: 86%

Section: Values Of the Turbulent Burning Velocitymentioning

confidence: 99%

Section: Values Of the Turbulent Burning Velocitymentioning

confidence: 99%

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Autoignitions and detonations in engines and ducts

Bradley

2012

Phil. Trans. R. Soc. A.

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“…The pertinent numerical simulations showed that even extremely narrow (10 flamewidth wide) channels are perfectly capable of capturing both the incipient flame acceleration [36] as well as the transition [37][38][39][40][41] (figure 4). These predictions have recently been corroborated experimentally by Wu and co-workers in their studies on the transition in capillary tubes [42,43]. 2 The idea of extending the concept of detonation is not new.…”

Section: Overviewmentioning

confidence: 76%

Combustion waves in hydraulically resisted systems

Brailovsky

Kagan

Sivashinsky

2012

Phil. Trans. R. Soc. A.

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The effects of hydraulic resistance on the burning of confined/obstacle-laden gaseous and gas-permeable solid explosives are discussed on the basis of recent research. Hydraulic resistance is found to induce a new powerful mechanism for the reaction spread (diffusion of pressure) allowing for both fast subsonic as well as supersonic propagation. Hydraulic resistance appears to be of relevance also for the multiplicity of detonation regimes as well as for the transitions from slow conductive to fast convective, choked or detonative burning. A quasi-one-dimensional Fanno-type model for premixed gas combustion in an obstructed channel open at the ignition end is discussed. It is shown that, similar to the closed-end case studied earlier, the hydraulic resistance causes a gradual precompression and preheating of the unburned gas adjacent to the advancing deflagration, which leads (after an extended induction period) to a localized autoignition that triggers an abrupt transition from deflagrative to detonative combustion. In line with the experimental observations, the ignition at the open end greatly encumbers the transition (compared with the closed-end case), and the deflagration practically does not accelerate up to the very transition point. Shchelkin's effect, that ignition at a small distance from the closed end of a tube facilitates the transition, is described.

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“…The above mentioned characteristics are typical near-limit phenomena. Different detonable mixtures and tube geometries exhibit slightly different nearlimit behavior [7][8][9][10][11][12][13][14]. To understand the limit phenomena, an extensive study covering a spectrum of mixture properties and tube geometries is required.…”

Section: Introductionmentioning

confidence: 99%

Near-limit propagation of gaseous detonations in narrow annular channels

Gao

Lee

2016

Shock Waves

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New results on the near-limit behaviors of gaseous detonations in thin annular channels are reported in this paper. The annular channels of thicknesses 3.2 mm and 5.9 mm are made by inserting smaller diameter tubes of 44.4 mm and 39.0 mm into a larger 50.8-mm diameter outer tube. The length of each annular channel is 2.0 m. Detonations are initiated in a steel driver tube where a small volume of a sensitive C2H2 + 2.5O2 mixture is used to facilitate detonation initiation. A 2-m length of circular tube with 50.8-mm diameter precedes the annular channel so that a steady Chapman-Jouguet (CJ) detonation is established prior to entering the annular channel. Four detonable mixtures of C2H2 + 2.5O2 + 85%Ar, C2H2 + 2.5O2 + 70%Ar, C3H8 + 5O2 and CH4 + 2O2 are used in the present study. Photodiodes spaced at 10 cm throughout the length of both annular channel and circular tube are used to measure the detonation velocity. In addition, smoked foils are inserted into the annular channel to monitor the cellular structure of the detonation wave. The results show that well within the limits the detonation wave propagates along the channel with a small local velocity fluctuation and an averaged global velocity can be deduced. The averaged detonation velocity has a small deficit of 5 -15% far from the limits and rapidly drops to 0.7VCJ -0.8VCJ when the onset of limit occurs. Subsequently, the fluctuation of local velocity also increases with decreasing initial pressure approaching the limit. No galloping detonations are observed for both stable and unstable mixtures in annular channels. The present study also confirms that single-headed spinning detonation occurs at the limit as in circular tube rather than the up and down "zig zag" mode in a two-dimensional rectangular channel.

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Reaction propagation modes in millimeter-scale tubes for ethylene/oxygen mixtures

Cited by 96 publications

References 34 publications

Autoignitions and detonations in engines and ducts

Autoignitions and detonations in engines and ducts

Combustion waves in hydraulically resisted systems

Near-limit propagation of gaseous detonations in narrow annular channels

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