Spark Ignition Technology: Electric Arc Plasmas and Electrode Erosion

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Spark Ignition TechnologyElectric Arc Plasmas
and Electrode Erosion

• Matt DAmato

Ohio Wesleyan University
John Whealton
Oak Ridge National Laboratory
National Transportation Research Center
December 13, 2001
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Why Are We Interested?

• Applied Science
• Potential for using lean burning fuel mixtures
  with rotating arc spark plug
• High pressure applications (gt 20 atm) currently
  have no spark plug that can last a long time due
  to electrode erosion
• Basic Science
• Plasma physics and atomic physics involved in
  electric discharge

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Experimental Design
(SmCo Magnets)
Power Supply
Ignition System
(B-field)
-

Spark Plug
Looking for information on two fronts
Erosion/Spectroscopy
Time Evolution/Photography

• High-speed imaging (ns)

• UV/Orange line intensities

• Nanosecond gate width camera used for imaging
  spark light with and without a monochromator
• Spark may last for 2-3 ms so ns resolution
  promises detailed analysis of breakdown, arc,
  and glow portions of the discharge

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(No Transcript)
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Magnet 1 Hz spark rate 1 ms gate width (longer
exposure captures full arc)
No Magnet 1 Hz spark rate 10 ns gate width (same
over longer exposures)

• Arc with and without presence of 1500 Gauss
• magnetic field along cylindrical axis
• Notice increased area of current sheet (180
  degrees)

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Timing Issues
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Camera control unit
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Frame grabber (data acquisition)
Ignition system and spark

• PROBLEM Ideally, one signal triggers all
  desired events
• SOLUTION Use multi-channel, delayed signal
  generator
• Accounts for 140 ns delay in camera circuitry
• Allows for minimum 5 ms dwell on spark coil
• Enables data acquisition at typical (30-60 Hz
  2k-3k rpm)
• and slow (1 Hz) spark rates
• Remember that spark does not occur at the same
  time as
• the spark gap is varied longer ramp time before
  breakdown for larger gaps

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Spark Gap and Erosion

• Some Considerations
• Conventional plug gap varied from 0.5 mm to 2.5
  mm
• Spark should contain more energy in larger gaps
• (higher breakdown voltage)
• Erosion analyzed by UV/orange spectral line ratio
• Difficult to balance image gain and intense lines
  to obtain desired
• signal
• Heat causes problems with resistor plugs and,
  possibly, non-resistor
• plugs too

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Clean spark plug -- sanded
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Three hours after sanding and first test.
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24 hours after sanding and first test.
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Basic Physics In Spark Plugs
Faradays Law (for a tightly wound coil of N
turns)
Emf -N(dFB/dt)
Vsecondary Vprimary(Nsecondary/Nprimary)
or, in terms of voltage in coils
Circuit Equations V IR P IV (Energy
transfer) P I2R (resistive dissipation)
Lorentz Force -- Moving charges in a magnetic
field



F q(v x B)
Remember right-hand rule or the F.B.I. for
positive charges
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Acknowledgements

• John Andriulli, Bill Partridge, Jacob Yoder
• Kaye McGinty and NTRC staff
• This project is funded by the United States
• Department of Energy