Ignition

Glassman, Irvin; Yetter, Richard A.

doi:10.1016/b978-0-12-088573-2.00007-5

Cited by 92 publications

(139 citation statements)

References 6 publications

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“…For an inclined surface, the gravitational acceleration in calculating the Grashof number must be replaced by its streamwise component

g \cos sans-serifθ

[3,33,34,35,36,37]. As a result, the modified Grashof number

G r^{*}

is given by

G r^{*} = \frac{g \cos sans-serifθ \times sans-serifψ false(T_{f} - T_{p} false) L^{3}}{v^{2}}

where

ψ

is the volume thermal expansion coefficient; L is characteristic length along fire plume, which can be estimated as the fire length of unit width,

1 / \sin false(α / 2 false)

in this study; and

v

is kinematic viscosity.…”

Section: Resultsmentioning

confidence: 99%

Prediction of Three-Dimensional Downward Flame Spread Characteristics over Poly(methyl methacrylate) Slabs in Different Pressure Environments

Zhao

Zhou

Liu³

et al. 2016

Materials

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The present study is aimed at predicting downward flame spread characteristics over poly(methyl methacrylate) (PMMA) with different sample dimensions in different pressure environments. Three-dimensional (3-D) downward flame spread experiments on free PMMA slabs were conducted at five locations with different altitudes, which provide different pressures. Pressure effects on the flame spread rate, profile of pyrolysis front and flame height were analyzed at all altitudes. The flame spread rate in the steady-state stage was calculated based on the balance on the fuel surface and fuel properties. Results show that flame spread rate increases exponentially with pressure, and the exponent of pressure further shows an increasing trend with the thickness of the sample. The angle of the pyrolysis front emerged on sample residue in the width direction, which indicates a steady-burning stage, varies clearly with sample thicknesses and ambient pressures. A global non-dimensional equation was proposed to predict the variation tendency of the angle of the pyrolysis front with pressure and was found to fit well with the measured results. In addition, the dependence of average flame height on mass burning rate, sample dimension and pressure was proposed based on laminar diffusion flame theory. The fitted exponent of experimental data is 1.11, which is close to the theoretical value.

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“…For an inclined surface, the gravitational acceleration in calculating the Grashof number must be replaced by its streamwise component

g \cos sans-serifθ

[3,33,34,35,36,37]. As a result, the modified Grashof number

G r^{*}

is given by

G r^{*} = \frac{g \cos sans-serifθ \times sans-serifψ false(T_{f} - T_{p} false) L^{3}}{v^{2}}

where

ψ

is the volume thermal expansion coefficient; L is characteristic length along fire plume, which can be estimated as the fire length of unit width,

1 / \sin false(α / 2 false)

in this study; and

v

is kinematic viscosity.…”

Section: Resultsmentioning

confidence: 99%

Prediction of Three-Dimensional Downward Flame Spread Characteristics over Poly(methyl methacrylate) Slabs in Different Pressure Environments

Zhao

Zhou

Liu³

et al. 2016

Materials

View full text Add to dashboard Cite

show abstract

“…Using Eqs. (16) and (17), the fundamental frequency of the base flow is found numerically to be approximately 1.82 √ p 0 /ρ 0 /L 1/2 . Finally, note that the global eigenfunctions found by decomposing the linearized Poincare map into dynamic modes correspond only to an instantaneous valueŨ (x, y, z, t 1 ), where t = t 1 is the initial time of the period [t 1 , t 1 + T f ].…”

Section: Floquet Stabilitymentioning

confidence: 77%

“…16 The scaled activation energy is taken close to the longitudinal instability limit for planar detonations, E = 20. The rationale for this choice is to focus the present research on transverse instability, thus avoiding the study of galloping detonations which feature slow pulsations that complicate the task of obtaining meaningful averages.…”

Section: Parametersmentioning

confidence: 99%

Dynamic mode decomposition analysis of detonation waves

2012

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Dynamic mode decomposition is applied to study the self-excited fluctuations supported by transversely unstable detonations. The focus of this study is on the stability of the limit cycle solutions and their response to forcing. Floquet analysis of the unforced conditions reveals that the least stable perturbations are almost subharmonic with ratio between global mode and fundamental frequency λ i /ω f = 0.47. This suggests the emergence of period doubling modes as the route to chaos observed in larger systems. The response to forcing is analyzed in terms of the coherency of the four fundamental energy modes: acoustic, entropic, kinetic, and chemical. Results of the modal decomposition suggest that the self-excited oscillations are quite insensitive to vortical forcing, and maintain their coherency up to a forcing turbulent Mach number of 0.3. C 2012 American Institute of Physics. [http://dx. Massa, Kumar, and Ravindran Phys. Fluids 24, 066101 (2012) and isotropic) for incompressible turbulence. Previous work on canonical detonation-turbulence interaction 6 focused on flow statistics and showed that the fundamental difference between the shock and detonation problems is the presence of a self-excited unstable region in the detonation post-shock, which supports intrinsic time scales (natural frequencies). The nonlinear modes of the detonation are investigated by applying a novel dynamic mode decomposition (DMD) approach developed by Schmid. 7 DMD is used to extract dynamic information from a sequence of snapshots of the flow field, which is projected onto a lower dimensional Krylov subspace to determine the eigenvalues and the corresponding eigenvectors. Among these, the most dominant are identified and analyzed. Demonstrations of this method are presented in Ref. 7 for a plane channel flow, flow over a two-dimensional cavity, and wake flow behind a flexible membrane passing between two cylinders. More recently, DMD technique has been successfully used to extract linear eigenmodes associated with acoustic pressure data obtained from an electrically heated horizontal Rijke tube. 8 The application of DMD to detonation waves and the decomposition of the energy modes into acoustic, entropic, kinetic, and chemical features is an original contribution of the present work.The remaining portion of this paper is divided in three parts. The method used to solve the flow field is detailed in Sec. II, the analysis of the results is presented in Sec. III, and the concluding remarks are given in Sec. IV. II. METHOD A. Governing equations

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“…For instance, in the low-pressure limit, by ignoring the three-body reaction term in matrix (5) and assuming quasi-steadiness for O and OH, one can obtain the asymptotic first limit determined by 1 = 0 has no positive concentration root to yield the first limit, in contrast to the statement in Ref. 3. Similarly, the wall destruction of O alone cannot balance the (R1) branched-chain, and that of H 2 O 2 alone cannot explain the third limit.…”

Section: A Key Roles Of the Destruction Of H And Homentioning

confidence: 80%

“…Furthermore, at each of two critical temperatures, it has one simple real root and one double real root, indicating the state of the turning point. The nature of the roots can be determined by computing the discriminant of the cubic equation (10), namely, = abcd − 4b 3 …”

Section: A the General Cubic Equation For The Three Limitsmentioning

confidence: 99%

An analysis of the explosion limits of hydrogen-oxygen mixtures

Law

2013

The Journal of Chemical Physics

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In this study, the essential factors governing the Z-shaped explosion limits of hydrogen-oxygen mixtures are studied using eigenvalue analysis. In particular, it is demonstrated that the wall destruction of H and HO2 is essential for the occurrence of the first and third limits, while that of O, OH, and H2O2 play secondary, quantitative roles for such limits. By performing quasi-steady-state analysis, an approximate, cubic equation for the explosion limits is obtained, from which explicit expressions governing the various explosion limits including the state of the loss of non-monotonicity are derived and discussed.

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Ignition

Cited by 92 publications

References 6 publications

Prediction of Three-Dimensional Downward Flame Spread Characteristics over Poly(methyl methacrylate) Slabs in Different Pressure Environments

Prediction of Three-Dimensional Downward Flame Spread Characteristics over Poly(methyl methacrylate) Slabs in Different Pressure Environments

Dynamic mode decomposition analysis of detonation waves

An analysis of the explosion limits of hydrogen-oxygen mixtures

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