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Relationship of flame propagation and combustion mode transition of end-gas based on pressure wave in confined space

Relationship of flame propagation and combustion mode transition of end-gas based on pressure wave in confined space
Relationship of flame propagation and combustion mode transition of end-gas based on pressure wave in confined space
The main objective of this work is to identify the end-gas combustion mode transition under different initial thermodynamic conditions and to focus on the role of pressure waves in autoignition formation and detonation development in the confined space by a group of two-dimensional (2D) numerical simulations with detailed chemistry of H2/air mixture. Pressure waves with different strengths are obtained by the flame acceleration in closed chambers with and without obstacles under three different initial temperatures. The results indicate that with the increase of initial temperature, there exist three different end-gas autoignition transition modes: autoignition promoted by strong flame acceleration, autoignition suppressed by weak flame acceleration and autoignition independent of flame acceleration. It is also shown that there are three types of end-gas autoignition-induced detonation initiation: (1) detonation initiated directly by the pressure wave generated from the flame propagation; (2) detonation initiated directly by the pressure wave generated from other hot-spot autoignition; (3) autoignition to detonation transition based on the reactivity gradient theory. Meanwhile, to further identify the autoignition transition mode under continuous variation of pressure wave intensity and initial temperature, an idealized physical model, with the Mach number of the pressure wave as the link between the flame propagation duration and autoignition time of the end-gas, is proposed. It is shown that the autoignition can be suppressed by the elevated flame speed when the pressure wave is weak, while it cannot be prevented intrinsically when the temperature of the end-gas is high or the pressure wave is strong enough. Moreover, different autoignition propagation modes are identified from Bradley’s diagram, including deflagration, developing detonation and thermal explosion, and the combined effects of reactivity and pressure wave strength are discussed as well.
Detonation, End-gas autoignition, Flame propagation, Pressure wave
0010-2180
371-386
Zhang, Xiaojun
aed8849c-3c3a-40ae-b579-f984fa369e8b
Wei, Haiqiao
357376b6-ab52-4a4c-a4e3-f4d6be35abbd
Zhou, Lei
29311185-e1e4-417f-9fb9-ddc1d3f16d09
Cai, Xiaodong
293bf621-f0e1-48ba-abaa-b41da81ea244
Deiterding, Ralf
ce02244b-6651-47e3-8325-2c0a0c9c6314
Zhang, Xiaojun
aed8849c-3c3a-40ae-b579-f984fa369e8b
Wei, Haiqiao
357376b6-ab52-4a4c-a4e3-f4d6be35abbd
Zhou, Lei
29311185-e1e4-417f-9fb9-ddc1d3f16d09
Cai, Xiaodong
293bf621-f0e1-48ba-abaa-b41da81ea244
Deiterding, Ralf
ce02244b-6651-47e3-8325-2c0a0c9c6314

Zhang, Xiaojun, Wei, Haiqiao, Zhou, Lei, Cai, Xiaodong and Deiterding, Ralf (2020) Relationship of flame propagation and combustion mode transition of end-gas based on pressure wave in confined space. Combustion and Flame, 214, 371-386. (doi:10.1016/j.combustflame.2020.01.006).

Record type: Article

Abstract

The main objective of this work is to identify the end-gas combustion mode transition under different initial thermodynamic conditions and to focus on the role of pressure waves in autoignition formation and detonation development in the confined space by a group of two-dimensional (2D) numerical simulations with detailed chemistry of H2/air mixture. Pressure waves with different strengths are obtained by the flame acceleration in closed chambers with and without obstacles under three different initial temperatures. The results indicate that with the increase of initial temperature, there exist three different end-gas autoignition transition modes: autoignition promoted by strong flame acceleration, autoignition suppressed by weak flame acceleration and autoignition independent of flame acceleration. It is also shown that there are three types of end-gas autoignition-induced detonation initiation: (1) detonation initiated directly by the pressure wave generated from the flame propagation; (2) detonation initiated directly by the pressure wave generated from other hot-spot autoignition; (3) autoignition to detonation transition based on the reactivity gradient theory. Meanwhile, to further identify the autoignition transition mode under continuous variation of pressure wave intensity and initial temperature, an idealized physical model, with the Mach number of the pressure wave as the link between the flame propagation duration and autoignition time of the end-gas, is proposed. It is shown that the autoignition can be suppressed by the elevated flame speed when the pressure wave is weak, while it cannot be prevented intrinsically when the temperature of the end-gas is high or the pressure wave is strong enough. Moreover, different autoignition propagation modes are identified from Bradley’s diagram, including deflagration, developing detonation and thermal explosion, and the combined effects of reactivity and pressure wave strength are discussed as well.

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Relationship of flame propagation and combustion mode transition-final - Accepted Manuscript
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Accepted/In Press date: 5 January 2020
e-pub ahead of print date: 24 January 2020
Published date: April 2020
Keywords: Detonation, End-gas autoignition, Flame propagation, Pressure wave

Identifiers

Local EPrints ID: 437664
URI: http://eprints.soton.ac.uk/id/eprint/437664
ISSN: 0010-2180
PURE UUID: bebd4751-220a-43b4-8435-8199f8c04ab2
ORCID for Ralf Deiterding: ORCID iD orcid.org/0000-0003-4776-8183

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Date deposited: 10 Feb 2020 17:30
Last modified: 28 Apr 2022 05:52

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Contributors

Author: Xiaojun Zhang
Author: Haiqiao Wei
Author: Lei Zhou
Author: Xiaodong Cai
Author: Ralf Deiterding ORCID iD

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