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Bychkov, Vitaly
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Publications (10 of 65) Show all publications
Bychkov, V., Sadek, J. & Akkerman, V. (2017). Analysis of flame acceleration in open or vented obstructed pipes. PHYSICAL REVIEW E, 95(1), Article ID 013111.
Open this publication in new window or tab >>Analysis of flame acceleration in open or vented obstructed pipes
2017 (English)In: PHYSICAL REVIEW E, ISSN 2470-0045, Vol. 95, no 1, article id 013111Article in journal (Refereed) Published
Abstract [en]

While flame propagation through obstacles is often associated with turbulence and/or shocks, Bychkov et al. [V. Bychkov et al., Phys. Rev. Lett. 101, 164501 (2008)] have revealed a shockless, conceptually laminar mechanism of extremely fast flame acceleration in semiopen obstructed pipes (one end of a pipe is closed; a flame is ignited at the closed end and propagates towards the open one). The acceleration is devoted to a powerful jet flow produced by delayed combustion in the spaces between the obstacles, with turbulence playing only a supplementary role in this process. In the present work, this formulation is extended to pipes with both ends open in order to describe the recent experiments and modeling by Yanez et al. [J. Yanez et al., arXiv: 1208.6453] as well as the simulations by Middha and Hansen [P. Middha and O. R. Hansen, Process Safety Prog. 27, 192 (2008)]. It is demonstrated that flames accelerate strongly in open or vented obstructed pipes and the acceleration mechanism is similar to that in semiopen ones (shockless and laminar), although acceleration is weaker in open pipes. Starting with an inviscid approximation, we subsequently incorporate hydraulic resistance (viscous forces) into the analysis for the sake of comparing its role to that of a jet flow driving acceleration. It is shown that hydraulic resistance is actually not required to drive flame acceleration. In contrast, this is a supplementary effect, which moderates acceleration. On the other hand, viscous forces are nevertheless an important effect because they are responsible for the initial delay occurring before the flame acceleration onset, which is observed in the experiments and simulations. Accounting for this effect provides good agreement between the experiments, modeling, and the present theory.

National Category
Fluid Mechanics and Acoustics Applied Mechanics
Identifiers
urn:nbn:se:umu:diva-131637 (URN)10.1103/PhysRevE.95.013111 (DOI)000392286000009 ()28208488 (PubMedID)
Available from: 2017-03-01 Created: 2017-03-01 Last updated: 2018-06-09Bibliographically approved
Jukimenko, O., Modestov, M., Dion, C., Marklund, M. & Bychkov, V. (2017). Multilevel model for magnetic deflagration in nanomagnet crystals. Physical Review B, 95(17), Article ID 174403.
Open this publication in new window or tab >>Multilevel model for magnetic deflagration in nanomagnet crystals
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2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 95, no 17, article id 174403Article in journal (Refereed) Published
Abstract [en]

We extend the existing theoretical model for determining the characteristic features of magnetic deflagration in nanomagnet crystals. For the first time, all energy levels are accounted for calculation of the the Zeeman energy, the deflagration velocity, and other parameters. It reduces the final temperature and significantly changes the propagation velocity of the spin-flipping front. We also consider the effect of a strong transverse magnetic field, and show that the latter significantly modifies the spin-state structure, leading to an uncertainty concerning the activation energy of the spin flipping. Our front velocity prediction for a crystal of Mn-12 acetate in a longitudinal magnetic field is in much better agreement with experimental data than the previous reduced-model results.

Keywords
Nanomagnets, Zeeman energy, spin avalanches, magnetic deflagration
National Category
Condensed Matter Physics
Research subject
Physics Of Matter
Identifiers
urn:nbn:se:umu:diva-124442 (URN)10.1103/PhysRevB.95.174403 (DOI)000400659900001 ()
Funder
Swedish Research Council
Note

Originally published in manuscript form

Available from: 2016-08-11 Created: 2016-08-11 Last updated: 2018-06-07Bibliographically approved
Demir, S., Bychkov, V., Chalagalla, S. H. & Akkerman, V. (2017). Towards a predictive scenario of a burning accident in a mining passage. Combustion theory and modelling, 21(6), 997-1022
Open this publication in new window or tab >>Towards a predictive scenario of a burning accident in a mining passage
2017 (English)In: Combustion theory and modelling, ISSN 1364-7830, E-ISSN 1741-3559, Vol. 21, no 6, p. 997-1022Article in journal (Refereed) Published
Abstract [en]

To reveal the inner mechanisms of a combustion accident in a coalmine, the key stages and characteristics of premixed flame front evolution such as the flame shapes, propagation speeds, acceleration rates, run-up distances and flame-generated velocity profiles are scrutinised. The theories of globally spherical, expanding flames and of finger-flame acceleration are combined into a general analytical formulation. Two-dimensional and cylindrical mining passages are studied, with noticeably stronger acceleration found in the cylindrical geometry. The entire acceleration scenario may promote the total burning rate by up to two orders of magnitude, to a near-sonic value. Starting with gaseous combustion, the analysis is subsequently extended to gaseous-dusty environments. Specifically, combustible dust (e.g. coal), inert dust (e.g. sand), and their combination are considered, and the influence of the size and concentration of the dust particles is quantified. In particular, small particles influence flame propagation more than large ones, and flame acceleration increases with the concentration of a combustible dust, until the concentration attains a certain limit.

Place, publisher, year, edition, pages
TAYLOR & FRANCIS LTD, 2017
Keywords
dust combustion, mining safety, fire safety, Darrieus-Landau instability, finger flame shape
National Category
Other Physics Topics
Identifiers
urn:nbn:se:umu:diva-143169 (URN)10.1080/13647830.2017.1328129 (DOI)000416606900001 ()
Available from: 2017-12-19 Created: 2017-12-19 Last updated: 2018-06-09Bibliographically approved
Demir, S., Akkerman, V., Rangwala, A. S. & Bychkov, V. (2016). ANALYSIS OF "FINGER" FLAME ACCELERATION AS A STAGE OF A METHANE AIR-DUST FIRE IN A COAL MINE. In: PROCEEDINGS OF THE ASME POWER CONFERENCE, 2015: . Paper presented at ASME 2015 Power Conference, POWER2015, San Diego, CA,JUN 28-JUL 02, 2015. The american society of mechanical engineers, Article ID V001T03A007.
Open this publication in new window or tab >>ANALYSIS OF "FINGER" FLAME ACCELERATION AS A STAGE OF A METHANE AIR-DUST FIRE IN A COAL MINE
2016 (English)In: PROCEEDINGS OF THE ASME POWER CONFERENCE, 2015, The american society of mechanical engineers , 2016, article id V001T03A007Conference paper, Published paper (Refereed)
Abstract [en]

To reveal the inner mechanism of gas explosion, the entire scenario of premixed flame front evolution within an accidental fire is prescribed. Specifically, "finger" flame shape, which is one of the key stages of flame evolution, is scrutinized with the situation of a methane-air explosion. A transition from a globally -spherical front to a finger-shaped one occurs when a flame starts approaching the passage walls. While this acceleration is extremely strong, it stops as soon as the flame touches the passage wall. This mechanism is Reynolds-independent; being equally relevant to micro channels and giant tunnels. The flame speed increases by an order of magnitude during this stage. To implement dusty environments, Seshadri formulation for the planar flame [Combustion and Flame 89 (7992) 333] is employed with a non-uniform distribution of inert dust gradients, specifically, linear, parabolic and hyperbolic spatial dust distribution gradients are incorporated into the "finger" flame shape. This study systematically investigates how the noncombustible dust distributions affect fire evolution, the flame shape, and propagation velocity.

Place, publisher, year, edition, pages
The american society of mechanical engineers, 2016
Keywords
Coal mining, Dust, Fire, Flames, Methane
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-120113 (URN)10.1115/POWER2015-49240 (DOI)000373970600027 ()978-0-7918-5660-4 (ISBN)
Conference
ASME 2015 Power Conference, POWER2015, San Diego, CA,JUN 28-JUL 02, 2015
Available from: 2016-06-13 Created: 2016-05-09 Last updated: 2018-06-07Bibliographically approved
Jukimenko, O., Modestov, M., Dion, C. M., Marklund, M. & Bychkov, V. (2016). Counterpart of the Darrieus-Landau instability at a magnetic deflagration front. Physical Review B. Condensed Matter and Materials Physics, 93(13), Article ID 134418.
Open this publication in new window or tab >>Counterpart of the Darrieus-Landau instability at a magnetic deflagration front
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2016 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 93, no 13, article id 134418Article in journal (Refereed) Published
Abstract [en]

The magnetic instability at the front of the spin avalanche in a crystal of molecular magnets is considered. This phenomenon reveals similar features with the Darrieus-Landau instability, inherent to classical combustion flame fronts. The instability growth rate and the cutoff wavelength are investigated with respect to the strength of the external magnetic field, both analytically in the limit of an infinitely thin front and numerically for finite-width fronts. The presence of quantum tunneling resonances is shown to increase the growth rate significantly, which may lead to a possible transition from deflagration to detonation regimes. Different orientations of the crystal easy axis are shown to exhibit opposite stability properties. In addition, we suggest experimental conditions that could evidence the instability and its influence on the magnetic deflagration velocity.

Keywords
Molecular magnets, Flames, Mn-12-acetate, Stability, Fusion
National Category
Condensed Matter Physics
Research subject
Physics
Identifiers
urn:nbn:se:umu:diva-119332 (URN)10.1103/PhysRevB.93.134418 (DOI)000373974800005 ()
Funder
Swedish Research Council
Available from: 2016-04-15 Created: 2016-04-15 Last updated: 2018-06-07Bibliographically approved
Ugarte, O., Bychkov, V., Sadek, J., Valiev, D. & Akkerman, V. (2016). Critical role of blockage ratio for flame acceleration in channels with tightly spaced obstacles. Physics of fluids, 28(9), Article ID 093602.
Open this publication in new window or tab >>Critical role of blockage ratio for flame acceleration in channels with tightly spaced obstacles
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2016 (English)In: Physics of fluids, ISSN 1070-6631, E-ISSN 1089-7666, Vol. 28, no 9, article id 093602Article in journal (Refereed) Published
Abstract [en]

A conceptually laminar mechanism of extremely fast flame acceleration in obstructed channels, identified by Bychkov et al. ["Physical mechanism of ultrafast flame acceleration," Phys. Rev. Lett. 101, 164501 (2008)], is further studied by means of analytical endeavors and computational simulations of compressible hydrodynamic and combustion equations. Specifically, it is shown how the obstacles length, distance between the obstacles, channel width, and thermal boundary conditions at the walls modify flamepropagation through a comb-shaped array of parallel thin obstacles. Adiabatic and isothermal (cold and preheated) side walls are considered, obtaining minor difference between these cases, which opposes the unobstructed channel case, where adiabatic and isothermal walls provide qualitatively different regimes offlame propagation. Variations of the obstructed channel width also provide a minor influence on flamepropagation, justifying a scale-invariant nature of this acceleration mechanism. In contrast, the spacing between obstacles has a significant role, although it is weaker than that of the blockage ratio (defined as the fraction of the channel blocked by obstacles), which is the key parameter of the problem. Evolution of the burning velocity and the dependence of the flame acceleration rate on the blockage ratio are quantified. The critical blockage ratio, providing the limitations for the acceleration mechanism in channels with comb-shaped obstacles array, is found analytically and numerically, with good agreement between both approaches. Additionally, this comb-shaped obstacles-driven acceleration is compared to finger flameacceleration and to that produced by wall friction.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2016
National Category
Other Physics Topics Other Mechanical Engineering Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-125154 (URN)10.1063/1.4961648 (DOI)000384878900016 ()
Funder
Lars Hierta Memorial Foundation, FO2015-0916
Available from: 2016-09-07 Created: 2016-09-07 Last updated: 2018-06-07Bibliographically approved
Ugarte, O., Demir, S., Demirgok, B., Akkerman, V., Bychkov, V. & Valiev, D. (2016). Effect of Wall Boundary Conditions on Flame Propagation in Micro-Chambers. In: PROCEEDINGS OF THE ASME POWER CONFERENCE, 2015: . Paper presented at ASME 2015 Power Conference, POWER2015, San Diego, CA, JUN 28-JUL 02, 2015. The american society of mechanical engineers, Article ID V001T03A009.
Open this publication in new window or tab >>Effect of Wall Boundary Conditions on Flame Propagation in Micro-Chambers
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2016 (English)In: PROCEEDINGS OF THE ASME POWER CONFERENCE, 2015, The american society of mechanical engineers , 2016, article id V001T03A009Conference paper, Published paper (Refereed)
Abstract [en]

Flame dynamics in micro-pipes have been observed to be strongly affected by the wall boundary conditions. In this respect, two mechanisms of flame acceleration are related to the momentum transferred in these regions: 1) that associated with flame stretching produced by wall friction forces; and 2) when obstacles are placed at the walls, as a result of the delayed burning occurring between them, a jet-flow is formed, intensively promoting the flame spreading. Wall thermal conditions have usually been neglected, thus restricting the cases to adiabatic wall conditions. In contrast, in the present work, the effect of the boundary conditions on the flame propagation dynamics is investigated, computationally, with the effect of wall heat losses included in the consideration. In addition, the powerful flame acceleration attained in obstructed pipes is studied in relation to the obstacle size, which determines how different this mechanism is from the wall friction. A parametric study of two-dimensional (2D) channels and cylindrical tubes, of various radiuses, with one end open is performed. The walls are subjected to slip and non-slip, adiabatic and constant temperature conditions, with different fuel mixtures described by varying the thermal expansion coefficients. Results demonstrate that higher wall temperatures promote slower propagation as they reduce the thermal expansion rate, as a result of the post-cooling of the burn matter. In turn, smaller obstacle sizes generate weaker flame acceleration, although the mechanism is noticed to be stronger than the wall friction-driven, even for the smaller sizes considered.

Place, publisher, year, edition, pages
The american society of mechanical engineers, 2016
Keywords
Boundary-value problems, Flames
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-120112 (URN)10.1115/POWER2015-49351 (DOI)000373970600029 ()
Conference
ASME 2015 Power Conference, POWER2015, San Diego, CA, JUN 28-JUL 02, 2015
Available from: 2016-06-20 Created: 2016-05-09 Last updated: 2018-06-07Bibliographically approved
Dion, C., Demirgok, B., Akkerman, V., Valiev, D. & Bychkov, V. (2015). Acceleration and Extinction of Flames In Channels With Cold Walls. In: M.I. Radulescu (Ed.), Proceedings of the 25th International Colloquium on the Dynamics of Explosions and Reactive Systems: . Paper presented at 25th International Colloquium on the Dynamics of Explosions and Reactive Systems, 2nd-7th August 2015, Leeds, UK.
Open this publication in new window or tab >>Acceleration and Extinction of Flames In Channels With Cold Walls
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2015 (English)In: Proceedings of the 25th International Colloquium on the Dynamics of Explosions and Reactive Systems / [ed] M.I. Radulescu, 2015Conference paper, Published paper (Refereed)
National Category
Mechanical Engineering Other Mechanical Engineering
Identifiers
urn:nbn:se:umu:diva-107733 (URN)
Conference
25th International Colloquium on the Dynamics of Explosions and Reactive Systems, 2nd-7th August 2015, Leeds, UK
Funder
Swedish National Infrastructure for Computing (SNIC), 2014/1-305
Available from: 2015-08-27 Created: 2015-08-27 Last updated: 2018-06-07Bibliographically approved
Bychkov, V., Modestov, M. & Law, C. K. (2015). Combustion Phenomena in Modern Physics: I. Inertial Confinement Fusion. Progress in Energy and Combustion Science, 47, 32-59
Open this publication in new window or tab >>Combustion Phenomena in Modern Physics: I. Inertial Confinement Fusion
2015 (English)In: Progress in Energy and Combustion Science, ISSN 0360-1285, E-ISSN 1873-216X, Vol. 47, p. 32-59Article, review/survey (Refereed) Published
Abstract [en]

The overarching objective of the present endeavor is to demonstrate the universal character of combustion phenomena for various areas of modern physics, focusing on inertial confinement fusion (ICF) in this review. We present the key features of laser deflagration, and consider the similarities and differences between the laser plasma flow and the slow combustion front. We discuss the linear stage of the Rayleigh-Taylor instability in laser ablation, short-wavelength stabilization of the instability due to the mass flow, and demonstrate the importance of the concepts and methods of combustion science for an understanding of the corresponding ICF processes. We show the possibility of the Darrieus-Landau instability in the laser ablation flow and discuss the specific features of the instability at the linear and nonlinear stages as compared to the combustion counterpart of this phenomenon. We consider the nonlinear stage of the Rayleigh-Taylor instability in the ICF and generation of ultra-high magnetic field by the instability, and show that proper understanding of vorticity production in the laser plasma and, hence, of the magnetic field generation requires concepts from combustion science.

Keywords
Combustion,  Inertial confinement fusion,  Deflagration,  Rayleigh-Taylor instability,  Darrieus-Landau instability
National Category
Energy Engineering Fluid Mechanics and Acoustics Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-96871 (URN)10.1016/j.pecs.2014.10.001 (DOI)000349588700002 ()
Available from: 2014-12-05 Created: 2014-12-05 Last updated: 2018-06-07Bibliographically approved
Sun, M.-B., Cui, X.-D., Wang, H.-B. & Bychkov, V. (2015). Flame Flashback in a Supersonic Combustor Fueled by Ethylene with Cavity Flameholder. Journal of Propulsion and Power, 31(3), 976-980
Open this publication in new window or tab >>Flame Flashback in a Supersonic Combustor Fueled by Ethylene with Cavity Flameholder
2015 (English)In: Journal of Propulsion and Power, ISSN 0748-4658, E-ISSN 1533-3876, Vol. 31, no 3, p. 976-980Article in journal (Refereed) Published
Place, publisher, year, edition, pages
American Institute of Aeronautics and Astronautics, 2015
National Category
Physical Sciences
Identifiers
urn:nbn:se:umu:diva-109390 (URN)10.2514/1.B35580 (DOI)000360839900025 ()
Available from: 2015-09-28 Created: 2015-09-25 Last updated: 2018-06-07Bibliographically approved
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