Effect of Magnetic Fields on Fire

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