University Research project - Radial Spark discharge

Question

University Research project - Radial Spark discharge

rodjerramjet (Aerospace)

(OP)

20 May 08 03:32

Hey,
I am currently designing a radial arc discharge ignition system for a Pulse Detonation Engine; I have a few questions that maybe you can help me with.
1. Can anyone recommend a paper that has investigated the Lorentz force acting on a spark, in particular the spark velocity to magnetic field strength relationship?
2. Can anyone suggest a supplier for Neo radial magnetized rings that will do evaluation quantities?

Cheers

Andrew

oldfieldguy (Electrical) · Answer 1 · 2008-05-20 08:54:18

andrew--

I wish I could be of assistance, but I can't.

However, that's an interesting project you're on. I was just reading a bit on it yesterday. I was curious to see the difference between the PDE and the old pulse-jet technology.

Good luck!

old field guy

MagMike (Materials) · Answer 2 · 2008-05-20 11:32:43

Andrew,
I'm not aware of anyone supplying evaluation quantities of fully sintered radially oriented Neo rings. They are generally very expensive to tool up.

What magnetic field strength do you need? Can you work with compression bonded Neo? That type of Neo is isotropic and can be magnetized radially. They are not as strong as fully sintered, but much more available.

There are other methods that might work, but it would help to know your magnetic field requirements (hopefully not "as strong as possible").

Also, I'm not aware of paper dealing with spark behavior and magnetic fields

Mike

MJR2 (Mechanical) · Answer 3 · 2008-05-20 12:47:23

I would have to wonder how you might be using the magnets. Any neo near an engine heat source like that might likely be demagnetized.

Mike

rodjerramjet (Aerospace) · Answer 4 · 2008-05-21 00:50:48

Hey guys thank you for the replys,

oldfieldguy: The difference between PDE and regular pulse jet is that the pulse jet burns fuel where as the PDE detonates the fuel as in an explosion more bang for your buck so to speak.

MagMike: The thing is that the stronger the magnet the higher the spark velocity I can achieve this will give the cleanest focal point of the flame front, but from my calculations looking for about 1 T. Compression bonded would be fine I guess.

MJR2: Demagnetizing though heat isnt a big worry beacuse the total test time is about 2 seconds and I was thinking of insulating the magnet in a resin too.

thank you for the help

MagMike (Materials) · Answer 5 · 2008-05-21 09:26:13

Unfortunately, compression bonded NdFeB will not produce 1 Tesla. The remanence for compression bonded NdFeB is about 0.69 Tesla.

Your best bet may be to use two axially oriented NdFeB rings with a steel ring in between. The NdFeB rings would have their North poles in contact with the steel, driving flux through the steel in a radial direction. You'll need a strong adhesive to keep the magnets bonded to the steel.

The next question would be: What diameter rings are you looking for?

rodjerramjet (Aerospace) · Answer 6 · 2008-05-21 21:12:59

Just need an ID of about 30mm to 35mm I have found one that is 25mm made from arc segments, I think using arc segments can work. Just need to do some CFD to see if the stagnation of the flow is enough in the smaller space to allow an easy combustion. Thank you for the help,
Andrew

sreid (Electrical) · Answer 7 · 2008-05-22 14:12:31

You can also build an approximate ring out of rectangular magnets. The ID is a polygon but approximates a circle. It's then pretty easy to purchase small quantities of magnets to your XYZ size.

unclesyd (Materials) · Answer 8 · 2008-05-25 08:06:09

A partial answer to your question #1. You will need to checkout the NASA site as there are probably several papers that will have the information you need.

http://ntrs.nasa.gov/search.jsp?R=958154&id=1&qs=No%3D50%26Ntt%3Dcircular%252Bmagnetic%252Bfield%26Ntk%3Dall%26Ntx%3Dmode%2520matchall%26N%3D0%26Ns%3DHarvestDate%257c1

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University Research project - Radial Spark discharge