Ignition delay in hydrogen–air and syngas–air mixtures: Experimental data interpretation via flame propagation

Medvedev, S. P.; Agafonov, G. L.; Khomik, S. V.; Gel’fand, B. E.

doi:10.1016/j.combustflame.2010.03.003

Cited by 35 publications

(7 citation statements)

References 15 publications

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“…The reduced-chemistry predictions are in excellent agreement with detailed-chemistry predictions until temperatures decrease below about 900 K, where the need for further study of both computational and experimental results has been discussed widely in the literature [12,13,14].…”

Section: Validation Of the Reduced Mechanismsupporting

confidence: 64%

A four-step reduced mechanism for syngas combustion

Boivin

Jiménez

Sánchez

et al. 2011

Combustion and Flame

152

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A four-step reduced chemical-kinetic mechanism for syngas combustion is proposed for use under conditions of interest for gas-turbine operation. The mechanism builds upon our recently published three-step mechanism for H 2 -air combustion (Boivin et al., Proc. Comb. Inst. 33, 2010), which was cate that the reduced description can be applied with reasonable accuracy in numerical studies of gas-turbine syngas combustion.

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Section: Validation Of the Reduced Mechanismsupporting

confidence: 64%

A four-step reduced mechanism for syngas combustion

Boivin

Jiménez

Sánchez

et al. 2011

Combustion and Flame

152

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“…As a result, the ignition delay measured experimentally in shock tubes is not that corresponding to homogeneous autoignition but rather the ratio of the tube radius to the flame speed [9]. Although more work is required to further clarify the nature of these low-temperature shock-tube processes, that is not the intention of the present paper.…”

Section: Introductionmentioning

confidence: 63%

Explicit analytic prediction for hydrogen–oxygen ignition times at temperatures below crossover

Boivin

Sánchez

Williams

2012

Combustion and Flame

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This paper addresses homogeneous ignition of hydrogen-oxygen mixtures when the initial conditions of temperature and pressure place the system below the crossover temperature associated with the second explosion limit.A three-step reduced mechanism involving H 2 , O 2 , H 2 O, H 2 O 2 and HO 2 , derived previously from a skeletal mechanism of eight elementary steps by assuming O, OH and H to follow steady state, is seen to describe accurately the associated thermal explosion. At sufficiently low temperatures, HO 2 consumption through HO 2 + HO 2 → H 2 O 2 + O 2 is fast enough to place this intermediate in steady state after a short build-up period, thereby reducing further the chemistry description to the two global steps 2H 2 + O 2 → 2H 2 O and 2H 2 O → H 2 O 2 + H 2 . The strong temperature sensitivity of the corresponding overall rates enables activation-energy asymptotics to be used in describing the resulting thermal runaway, yielding an explicit expression that predicts with excellent accuracy the ignition time for different conditions of initial temperature, composition, and pressure.

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“…The propagation of the forming combustion front into the unreacted mixture determines the time of the defl agration distribution of the fl ame τ d , which can be much smaller than the kinetic time of the spontaneous ignition of a mixture τ k at the given temperature when the progress of the process is determined entirely by thermally equilibrium gas-phase chemical reactions [9]. In Fig.…”

mentioning

confidence: 99%

Ignition of Hydrogen–Oxygen Mixtures Behind the Incident Shock Wave Front

Павлов

Gerasimov

2016

J Eng Phys Thermophy

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Experimental investigation of the ignition of a stoichiometric hydrogen-oxygen mixture behind an incident shock wave in a shock tube at pressures p = 0.002-0.46 MPa and temperatures T = 500-1000 K is carried out. The existence of three limits of ignition typical of the ignition of hydrogen-oxygen mixtures in a spherical vessel is noted. It is shown that at pressures p ≥ 0.1 MPa the ignition of a hydrogen-oxygen mixture begins at a much lower temperature than the ignition of a hydrogen-air mixture. The measured induction times agree well with theoretical estimates.Introduction. Investigation of the ignition of hydrogen-oxygen mixtures in shock tubes behind the incident shock wave front is of both theoretical and practical interest. In particular, the creation of hypersonic passenger airplanes requires the development of new effi cient engines burning hydrogen fuel [1]. The supersonic character of fl ow of a gaseous mixture behind the incident shock wave front explains the attractiveness of the use of a shock tube for carrying out experiments related to the practical implementation of hydrogen ignition under conditions of a hypersonic fl ight [2]. The majority of research works concerned with the study of the process of ignition of combustible mixtures in shock tubes were carried out behind refl ected shock waves where the gas is at rest relative to the shock tube walls [3]. In a recent work [4], measurement of the limits of ignition and times of induction of hydrogen-air mixtures was made behind incident shock waves, as well as a comparison of the obtained results with the results of experiments conducted behind refl ected shock waves. Studies reporting on experimental works associated with ignition of hydrogen-oxygen mixtures behind refl ected shock waves are very few [5][6][7], whereas the data that would have been obtained behind incident shock waves are lacking completely.The aim of the present work is to determine the ignition limits and induction times in stoichiometric hydrogenoxygen mixtures behind the incident shock wave front and to compare the results obtained with those related to pertinent experiments with hydrogen-air mixtures.Experimental. Experiments on studying the process of ignition of hydrogen-oxygen mixtures were carried out on a shock tube (inner radius r = 28.5 mm) consisting of a high-pressure chamber of length 1 m and a low-pressure chamber of length 4.5 m separated by a diaphragm. The low-pressure chamber is fi lled with a test gas and the high-pressure one, with a propelling gas. When the diaphragm is ruptured, in the low-pressure chamber a shock wave starts to propagate, as well as to compress and heat the mixture being investigated. The test facility is equipped with systems of evacuation, preparation, and bleeding-in of gas mixtures, instrumentation for recording emission and absorption spectra, measuring the shock wave velocity, and recording the pressure profi le. The schematic diagram of the facility and description of the measuring equipment are given in [4].Experiments were carri...

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Ignition delay in hydrogen–air and syngas–air mixtures: Experimental data interpretation via flame propagation

Cited by 35 publications

References 15 publications

A four-step reduced mechanism for syngas combustion

A four-step reduced mechanism for syngas combustion

Explicit analytic prediction for hydrogen–oxygen ignition times at temperatures below crossover

Ignition of Hydrogen–Oxygen Mixtures Behind the Incident Shock Wave Front

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