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Effect of Magnetic Fields on Fire

Effect of Magnetic Fields on Fire. Katsuo Maxted Aviation Fire Dynamics March 15, 2013. Outline. Introduction Magnetic Properties in Combustion Magnetic Confinement Fusion Magnetic Induction in a Plasma Torch Modeling Affects on a Diffusion Flame Benefits Using Magnetism. Introduction.

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Effect of Magnetic Fields on Fire

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  1. Effect of Magnetic Fields on Fire Katsuo Maxted Aviation Fire Dynamics March 15, 2013

  2. Outline • Introduction • Magnetic Properties in Combustion • Magnetic Confinement Fusion • Magnetic Induction in a Plasma Torch • Modeling Affects on a Diffusion Flame • Benefits Using Magnetism

  3. Introduction Magnetism • Defined as the phenomena that accounts to forces exerted by magnets • Depends on other magnetic fields, temperature, and pressure

  4. N S Introduction Types of Magnets • Ferromagnets are permanent and have the strongest influence.

  5. Introduction Types of Magnets • Paramagnets are temporary magnets that created from an applied magnetic field S N N S

  6. Introduction Types of Magnets • Diamagnets are the weakest magnets that exhibit an opposing magnetic field to an applied one N S N S

  7. N S Introduction Types of Magnets • Electromagnets are magnets composed of wires carrying an electric current

  8. Introduction • Bio-magnetics [1] • Magnetic Resonance Imaging (MRI) • Enhance Combustion Processes Magnetic Fields have been applied in:

  9. Introduction • Units are in T (Tesla) for strength and T/m (Tesla per meter) for intensity • Refer to magnetic gradient for multiple field lines • Paramagnetism, Ferromagnetism, & Diamagnetism

  10. Introduction Magnetic field affects all gases: • Oxygen is known for its paramagnetism • Nitrogen, Carbon Dioxide, and most hydrocarbon fuels are repelled because of their diamagnetic nature [2, 3] http://www.youtube.com/embed/ozhIQG8XBkY

  11. Outline • Introduction • Magnetic Properties in Combustion • Magnetic Confinement Fusion • Magnetic Induction in a Plasma Torch • Modeling Affects on a Diffusion Flame • Benefits Using Magnetism

  12. Magnetic Properties Background [4, 5, 6] • In the presence of an external magnetic field, a flame on wax paper forms an equatorial disk and is more luminous • Faraday attributed this to deflection of charged particles from the flame • Von Engel & Cozens said deflection is caused by diamagnetic gases

  13. Magnetic Properties Effect on Fluid Flow • For highly conductive fluids like plasma and salt water, Lenz’s law indicates that a charged fluid will follow the direction of a magnetically induced electromotive force • Magnetic field lines perpendicular to fluid flow direction increase it’s speed while parallel magnetic fields do the opposite [2]

  14. Magnetic Properties Effects in Chemical Reactions • Spin (S) indicates the angular momentum of a charged particle • The multiplicity or overall spin of a molecule is defined as 2S + 1 where S = ½*(number of unpaired electrons) • Maxwell’s theory states that a moving charged particle creates a magnetic moment, indicating that a higher spin generates a stronger magnetic moment

  15. Magnetic Properties Effects in Chemical Reactions [7] • Oxygen gas (which is in a singlet state) must be broken into triplets before becoming paramagnetic • Radicals are paramagnetic with a spin S = ½ • Diamagnetic effects cause radicals to form in pairs, causing doublets to excite to triplets, and after reaction, spins are conserved from diamagnetic predecessors

  16. Magnetic Properties Effects in Chemical Reactions [7] • Magnetic control on spin • Four spin states: exchange interaction, electron spin-dipolar interaction, hyperfine interaction and Zeeman interaction

  17. Magnetic Properties Effects in Chemical Reactions • Example: Photochemical Process [8] Stationary temperature dependence of the reacting system on external radiation value in the presence and in the absence of magnetic field

  18. Magnetic Properties Effects in Chemical Reactions • Example: Photochemical Process [8] Stationary concentration dependence of biradicals on external radiation value in the presence and in the absence of magnetic field

  19. Magnetic Properties • Magnetic field Intensity of 1 T is said to alter combustion characteristics [3, 9] • Production of 1 T rare-earth magnets can replace the need for electromagnets [10, 11]

  20. Magnetic Properties Dipole alignment • Oxygen has randomly oriented dipole moments that align with the applied field • Nitrogen, Carbon Dioxide and most hydrocarbon fuels form a net dipole moment in opposition to the applied field

  21. Magnetic Properties Three Regimes for blocking gas flow [12]: • First Regime - At low velocities, gas flow is diffused through the magnetic curtain. • Second Regime - At slightly higher flow velocities, gas flow is blocked at the highest magnetic field gradient • Third Regime - At higher flow rates, the gas flow is allowed to pass though curtain in a pinched fashion Magnetic fields do not separate nitrogen and oxygen! Magnetic fields do not separate nitrogen and oxygen

  22. Magnetic Properties For combustion of alchohol [1, 2] • Application of magnetic field gradients of 20-200T/m under 0.5 - 1.4 T decreased combustion temperature from 200 to 100 ˚C • Combustion rate decreased for location of highest magnetic field strength • Candle flame, hydrogen flame and methane flame are also deflected toward lesser magnetic field strengths

  23. Magnetic Properties Flame Quenching [3] • Candle flame can be quenched between two cylindrical electromagnets when interacting with a field strength of 1.5 T and intensity gradient of 50-300 T/m in a 5-10 mm space • Flame is not quenched below 0.9 T

  24. Magnetic Properties Radiative Emissions from Diffusion Flames [13] • Magnetic field near reaction zone greatly increases emission intensity • Cleaner burning - soot levels are decreased

  25. Magnetic Properties Studies in Microgravity [14, 15, 16] • Larger influence on diffusion flames due to buoyancy induced convective air flow • Longer burning periods on diffusion flames • Affects flame shape without pressurized containments

  26. Magnetic Properties Studies in Microgravity [14, 15, 16] • In microgravity, the magnetic field causes the flame to behave like it’s subjected to buoyant forces (which can be isolated in normal gravity) • Large soot particles can be decreased

  27. Magnetic Properties Summary • Uniform Magnetic field produces no observable change • Combustion is enhanced in the presence of a decreasing magnetic field • Ferromagnets are ideal for experimentation due to the absence of Ampere and Lorenz forces

  28. Outline • Introduction • Magnetic Properties in Combustion • Magnetic Confinement Fusion • Magnetic Induction in a Plasma Torch • Modeling Affects on a Diffusion Flame • Benefits Using Magnetism

  29. Magnetic Confinement Fusion Plasma in Relation to Fire • Plasma is defined as a quasineutral gas composed of charged and neutral particles • The ‘reaction zone’ of a diffusion flame at high pressure may be characterized as a plasma http://www.youtube.com/embed/uPU9cEK5YsM

  30. Magnetic Confinement Fusion • Stellarator • Toroidal Tokamak • Spherical Tokamak

  31. Magnetic Confinement Fusion • Stellarator [17] QPS Coil-sets and plasma. Modular coils are shown in light blue, toroidal field coils are pink, vertical field coils are in tan. Color contours (blue = low field, red = high field) show the magnetic field strength on the outer plasma magnetic flux surface

  32. Magnetic Confinement Fusion • Toroidal Tokamak [18]

  33. Magnetic Confinement Fusion • Spherical Tokamak [19] 33

  34. Outline • Introduction • Magnetic Properties in Combustion • Magnetic Confinement Fusion • Magnetic Induction in a Plasma Torch • Modeling Affects on a Diffusion Flame • Benefits Using Magnetism

  35. Plasma Torch[20] • Hybrid (RF + DC) plasma torch

  36. Plasma Torch[20] • Direct Current Induction Includes anodes, cathode and gas inlets

  37. Plasma Torch[20] • Radio-frequency Induction Advantages: large volume plasma generation; cleanness; simplicity; easy in-feeding into plasma; long lifecycle Includes metal water-cooling sections; quarts tube; body corpus and gas former

  38. Plasma Torch[20]

  39. Plasma Torch[20]

  40. Outline • Introduction • Magnetic Properties in Combustion • Magnetic Confinement Fusion • Magnetic Induction in a Plasma Torch • Modeling Affects on a Diffusion Flame • Benefits Using Magnetism

  41. Affects on Diffusion Flame [21]

  42. Affects on Diffusion Flame [21] Evolution of the temperature along the flame axis, lift-off height and flame length with the injection velocity of air in the presence of a magnetic field(MF) and without magnetic field(WMF) for two injection velocities of CH4: 0.54(a) and 0.79(d) for a position of the burner Z = +85mm.

  43. Affects on Diffusion Flame [21] Evolution of the visual lift-off height with the injection velocity of air in the presence of a magnetic field (MF) and without magnetic field (WMF) for two injection velocities of CH4: 0.54 and 0.79 m/s for a position of the burner Z = -185mm.

  44. Affects on Diffusion Flame [21]

  45. Affects on Diffusion Flame [21] • Analysis • Magnetic fields of decreasing strength lengthen lift-off height and accelerate normal convection • Thermo-magnetic convection slows normal convection for fields of increasing strength

  46. Solenoid (hollow) Magnetic Field Lines Diffusion Flame Field Modeling

  47. Field Modeling • Geometry Coil 0

  48. Field Modeling • Biot-Savart Law

  49. Field Modeling • Biot-Savart Law

  50. Field Modeling • Biot-Savart Law

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