Lorentz forces provide a unique method for the control and mixing of gas
flows without the physical intrusion of objects into the flow. Lorentz forces arise
when an electric current is passed through a volume in the presence of a magnetic
field. The interaction between the electric current and the electric and magnetic
fields produces a body force which affects the flow. These forces have been
investigated experimentally by other researchers and show promise as a way to
accelerate combustion in diffusion flames by increasing the mixing rate of fuel and
oxidant streams. Theoretical and numerical models were developed to gain insight
into this process.
Alkali metal seeding raises the electrical conductivity of a flame by two to
three orders of magnitude. This has two significant effects: the Lorentz force
becomes stronger for the same applied electric current and magnetic field, and the
alkali seed concentration becomes a dominant factor in determining electrical
conductivity of seeded gases. This makes electrical conductivity much easier to
predict, and so the Lorentz body force produced is easier to determine.
A theoretical basis for numerical modeling of reactive flows with variable
body forces has been developed. Many issues are important in simulating gas
flows. Conservation of chemical species must be carefully maintained. Mass
transport by gaseous diffusion, which limits combustion rates in a diffusion flame,
must be appropriately modeled. Viscous action is also important, since it promotes
mixing of the fuel and oxidant streams. Convective, conductive, and diffusive
transport of energy must be carefully treated since energy transport directly affects
the fluid flow.
A numerical model of an incompressible gas flow affected by Lorentz forces
was written and tested. Although assumptions made in the model, such as
isothermal conditions and uniform density, are not found in diffusion flames, the
numerical model predicts velocity vector patterns similar to those observed in actual
Lorentz force tests on diffusion flames.
A simulation code for compressible, reactive gas flows which include
Lorentz forces has also been written. Several parts of the model have been
validated, and the approach used appears likely to produce successful simulations.
Further validation studies will be required, however, before complete modeling of
the diffusion flame can proceed. / Graduation date: 1995
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/35563 |
| Date | 21 November 1994 |
| Creators | Thompson, Jon Ira |
| Contributors | Pattee, Heidi A. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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