Plasma Jet Ignition

[Don.F.Broadus at ucm.com]

Smokey yunick of racing fame experimented with the plasma ignition and found
the results promising. The power supply was the 
biggest problem to overcome to get plasma out of the lab and onto the
street. You mention lighting gas with a  blowtorch, Smokey
actually did that and that's what got him started on plasma experiments.    

> -----Original Message-----
> From:	bob at bobthecomputerguy.com [SMTP:bob at bobthecomputerguy.com]
> Sent:	Tuesday, February 23, 1999 10:42 AM
> To:	diy_efi at efi332.eng.ohio-state.edu; fanglers at xephic.dynip.com
> Subject:	Plasma Jet Ignition
> 
> More Heywood Factoids - chapter 9.5
> 
> All spark ignition is divided into three stages:  Breakdown, arc and glow.
> Breakdown is when the spark is first established, arc is after the plasma
> explosion and glow is the termination of spark.
> 
> The breakdown stage is where the plasma column is generated. Its
> characterizes
> by high (> 10 KV) voltage, high peak current (~200 A) and short duration
> (~10
> ns ) and is about 40 micro m in diameter.  All energy is transferred
> without
> loss to this column.  The temperature and pressure rise extremely rapidly
> in
> this column to about 60,000 k and a few hundred atmospheres.  A strong
> shock
> wave or blast wave propagates outward, the channel expands and in
> consequence,
> the plasma temperature falls.  Typically, 30% of the plasma energy is
> carried
> away by the shock wave: however most of this is regained since spherical
> blast
> waves transfer most of their energy to the gas within a small sphere (~
> 2mm)
> into which the breakdown plasma soon expands.
> 
> The breakdown phase ends when a hot spot develops on the cathode and the
> column degrades to an arc.
> 
> The arc phase voltage is low (< 100v), though the current can be as high
> as
> the external circuit permits.  In contrast to the breakdown phase where
> the
> gas in the channel is fully disassociated and ionized, in the arc phase
> the
> degrees of disassociation may still be high at the center of the
> discharge,
> but the degree of ionization is much lower (~ 1%).  Voltage drops at the
> cathode and anode electrodes  are a significant fraction of the arc
> voltage
> and the energy deposited in these electrode sheath regions, which is
> conducted
> away by the metal electrodes, is a substantial fraction of the total
> energy.
> 
> About 94% of the spark energy  is converted to plasma in the breakdown
> phase
> vs only 50% in the arc stage - plus the arc stage is only ~6000K.
> 
> About .2mj of energy is required to ignite a quiescent stoichiometric
> fuel-air
> mixture at normal engine conditions.  Swirl, turbulence, etc raise this
> number
> by an order of magnitude in a working normal engine.
> 
> Conventional coil type ignitions deliver 30 to 50 MJ, but a plasma jet
> typically requires 1 joule or more stored energy and this is released in
> < 20
> microseconds.   
> 
> There is a race condition - to pump as much energy as fast as possible
> into
> the plasma column after it is established and before the plasma blast so
> as to
> maximize the blast effect.  Before the blast and cathode hot spotting
> occurs,
> the plasma column has almost infinite conductance.  Since greater than 90%
> of
> the pumped energy will convert to plasma at sun like temperatures in the
> breakdown stage, its critical to pump it early.
> 
> The blast wave from the plasma chamber into the main chamber is comparable
> to
> trying to light a pool of gasoline with a match ( conventional ) or a blow
> torch ( Plasma Jet )  
> 
> 1963 Ford C-600 Prison Bus Conversion "Home"
> 1971 Lincoln Continental 460 "Christine"
> 1972 "Whale" Mustang awaiting transplant
> 1978 Dodge Long Bed Peeek Up "Bundymobile"
> 
> Habaneros - not just for breakfast anymore