Ignition of lean hydrogen–air mixtures

Swain, M.R.; Filoso, Patrick; Swain, Matthew N.

doi:10.1016/j.ijhydene.2004.10.017

Cited by 21 publications

(7 citation statements)

References 1 publication

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“…Such knowledge is relevant, for example, to proposed laser-induced spark ignition [1]. Because of the interest in this application, as well as safety concerns in explosion prevention, the study reported here addresses ultra-lean hydrogen flammability limits at different pressures, temperatures, and water-vapor content, complementing existing experimental results [2,3,4,5].…”

Section: Introductionmentioning

confidence: 84%

Flammability conditions for ultra-lean hydrogen premixed combustion based on flame-ball analyses

Fernández-Tarrazo

Sánchez

Liñán³

et al. 2012

International Journal of Hydrogen Energy

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Keywords:Hydrogen Flammability limit Ultra-lean combustion Reduced chemistryFlame balls a b s t r a c t It has been reasoned that the structures of strongly cellular flames in very lean mixtures approach an array of flame balls, each burning as if it were isolated, thereby indicating a connection between the critical conditions required for existence of steady flame balls and those necessary for occurrence of self-sustained premixed combustion. This is the starting assumption of the present study, in which structures of near-limit steady sphericosymmetrical flame balls are investigated with the objective of providing analytic expressions for critical combustion conditions in ultra-lean hydrogen-oxygen mixtures diluted with N 2 and water vapor. If attention were restricted to planar premixed flames, then the lean-limit mole fraction of H 2 would be found to be roughly ten percent, more than twice the observed flammability limits, thereby emphasizing the relevance of the flame-ball phenomena.Numerical integrations using detailed models for chemistry and radiation show that a onestep chemical-kinetic reduced mechanism based on steady-state assumptions for all chemical intermediates, together with a simple, optically thin approximation for water-vapor radiation, can be used to compute near-limit fuel-lean flame balls with excellent accuracy.The previously developed one-step reaction rate includes a crossover temperature that determines in the first approximation a chemical-kinetic lean limit below which combustion cannot occur, with critical conditions achieved when the diffusion-controlled radiation-free peak temperature, computed with account taken of hydrogen Soret diffusion, is equal to the crossover temperature. First-order corrections are found by activation-energy asymptotics in a solution that involves a near-field radiation-free zone surrounding a spherical flame sheet, together with a far-field radiation-conduction balance for the temperature profile. Different scalings are found depending on whether or not the surrounding atmosphere contains water vapor, leading to different analytic expressions for the critical conditions for flame-ball existence, which give results in very good agreement with those obtained by detailed numerical computations. The one-step chemistry employed in the present work, which involves a non-Arrhenius rate having a cutoff at the crossover temperature, applies with excellent accuracy to the description of lean premixed hydrogen-air combustion, i.e, for f(0:5 at atmospheric pressure, and could be used for instance in the numerical simulation of the propagation of curved or cellular flames in ultra-lean reactive atmospheres, of interest for safety analyses related to the storage, transport, and handling of hydrogen.

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Section: Introductionmentioning

confidence: 84%

Flammability conditions for ultra-lean hydrogen premixed combustion based on flame-ball analyses

Fernández-Tarrazo

Sánchez

Liñán³

et al. 2012

International Journal of Hydrogen Energy

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“…This number was introduced for liquid fuels and characterizes the resistance of these fuels to a knock generated by self-ignition of the remains of the mixture in its final phase of combustion in a piston engine. Hydrogen, in literature (Das [1], Swain and others [2]) is characterized by RON (research octane number) with the value of 130 as a fuel of very good resistance to knock combustion. On the other hand, during combustion hydrogen can generate pressure waves of intensity higher than gasoline combusted under the same conditions [3].…”

Section: Wstępmentioning

confidence: 99%

“…W odniesieniu do wodoru w literaturze (m.in. Das [1] oraz Swain i inni [2]) podaje się LOB (liczba oktanowa badawcza) na poziomie 130, charakteryzując wodór, z jednej strony, jako paliwo o bardzo dobrej odporności na spalanie stukowe. Z drugiej strony wodór podczas spalania może generować fale ciśnienia o intensywności wyższej niż spalana w takich samych warunkach benzyna [3].…”

Section: Wstępunclassified

Hydrogen resistance to knock combustion in spark ignition internal combustion engines

Szwaja¹

2011

Combustion Engines

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The results of investigations focusing on knock combustion analysis of a hydrogen-fueled engine have been presented in the paper. Knock intensity was determined as the intensity of the in-cylinder combustion pressure pulsations (recorded with a sampling frequency of 100 kHz) and filtered through high-pass filtering with cut-off frequency of 3.5 kHz. The research was conducted on the CFR engine with a variable compression ratio ranging from 6 to 14. The research has shown a rapid increase in pressure pulsations amplitude was observed while the compression ratio was changed from 11 to 12. This was interpreted as a result of in-cylinder hydrogen-air mixture self-ignition at the end of the spark ignition controlled combustion. Supporting this observation the theorem of dual nature of hydrogen knock combustion was postulated. Intensity of the pressure pulsations that accompany normal combustion without hydrogen self-ignition was in an exponential correlation with the compression ratio, which directly translates into a similar correlation of the pulsations and temperature of hydrogen-air mixture at the moment of ignition.

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“…The largest time step used was 0.4 to 0.5 seconds. 8 We previously used a polyhedral 9 7 With the incompressible ideal gas option, operating pressure only is used in the density calculation, and this is suitable for low Mach number flows. Density would be calculated as a function of operating pressure and local relative pressure in a compressible, high Mach number flow.…”

Section: Computational Fluid Dynamics Model Validationmentioning

confidence: 99%

“…Those comparisons emphasize the sensitivity of the results to the modeling approach; the key variables are turbulence model, time and space resolution, and discretization scheme. Swain et al used helium to study leakage scenarios experimentally [7] and tested hydrogen ignition and combustion scenarios [8,9,10]. Helium is useful in experimental work because (1) it avoids the hazard of possible ignition during the experiment, (2) its physical properties are similar to those of hydrogen, 1 Our study specifically addresses a slow, sustained, indoor hydrogen gas leak that, over time, may develop a flammable mixture throughout a large portion of the garage volume.…”

Section: Introductionmentioning

confidence: 99%

Buoyancy-Driven Ventilation of Hydrogen from Buildings: Laboratory Test and Model Validation

Barley¹,

Gawlik²

2009

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Hydrogen gas leaking from a hydrogen-powered vehicle in a residential garage may form a flammable mixture with air. Passive, buoyancy-driven ventilation is one approach to limiting the concentration to a safe level. We explored the relationship between leak rate, ventilation design, and hydrogen concentration through laboratory testing, an algebraic analysis, and CFD modeling. We used helium to test slow, steady, low-velocity leaks in a full-scale test room under nearly isothermal, steady conditions, and we report the results in sufficient detail that other modelers can use them. The results show the importance and variability of stratification. Our algebraic and CFD models agree very well with the experimental results. We describe our CFD approach in sufficient detail for use by others. We tested under nearly isothermal conditions, but also discuss indoor-outdoor temperature difference as an important risk factor. Information about realistic leakage scenarios is needed to apply these results as safety recommendations.iv

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Ignition of lean hydrogen–air mixtures

Cited by 21 publications

References 1 publication

Flammability conditions for ultra-lean hydrogen premixed combustion based on flame-ball analyses

Flammability conditions for ultra-lean hydrogen premixed combustion based on flame-ball analyses

Hydrogen resistance to knock combustion in spark ignition internal combustion engines

Buoyancy-Driven Ventilation of Hydrogen from Buildings: Laboratory Test and Model Validation

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