Plasma Jet Ignitition

[Wen Yen Chan]

Hello,

Just a thought.... why not add a small HV capacitor in parallel with a non
resistor plug (using  a low inductance path) and switch the ignition wires
to solid conductor types. When the normal ignition system fires the HV cap
would charge 'slowly' to the breakdown voltage of the gap and dump its
charge really quickly. The speed at which we could dump the charge through
the plug would not be limited by the inductance of the spark plug wires
or the leakage inductance of the ignition coils.

Wen

On Wed, 24 Feb 1999, Robert Harris wrote:

> Why? -  All spark ignition starts with a plasma phase.  During this breakdown
> phase the "blast wave" created will exceed 10 to the 4th meters velocity at
> several hundred atmospheres pressure.   This injects a cloud of hyper
> temperature ~60,000k free radicals into the combustible mixture.  As the
> electrodes heat up and the conductance falls, the spark transitions into an
> arc, where the expanding velocity drops to below local sonic and the
> temperature falls to ~6000 k.   The energy transfer heat is primarily
> conduction to the combustible mixture.
> 
> Increasing the size of the Plasma phase of ANY spark ignition results in
> greater quantity and penetration of free radicals into the combustible
> mixture.  The larger the cloud of free radicals expelled during the Plasma
> breakdown, the faster and surer the ignition.  Translation - less advance
> needed, faster flame front generation.  More power, more tolerance to the
> cyclic F/A variations - particularly those seen by the sparking device.
> 
> There are literally hundreds of patents which I am patiently wading thru, but
> there has been a lot of thought on this.
> 
> In a conventional ignition system, most of the energy is disapated in the arc
> and glow stage, yet the Plasma stage determines most of the ignition
> characteristics.  ANY design that pumps more energy into the plasma portion
> will increase the size of the cloud and result in better performance.  And
> while the lab researchers try to reach 1 joule to virtually flood the main
> chamber and cause near instantaneous combustion ***** NOT DETONATION **** , I
> would be quite content to pump as much as practical into the plasma stage and
> suffer with only greatly extended mixture range, elimination of misfire and
> near TDC timing.  
> 
> How much is helpful?  Depending on the ignition design, only up to about 2 %
> of the total sparking energy is consumed in the Plasma phase.  Simply using
> another CD box triggered and rigged by a diode stack to fire into the first
> and modified to quickly dump its energy could potentially increase the plasma
> energy 50 fold if it could dump fast enough.
> 
> >From the reading of the patents and others, simply shielding the spark in a
> pre chamber reduces the energy needed to fire an order of magnitude ( why
> anti-fouler improve ignition )   Combining any small pre chamber with a pumped
> up plasma ignition should result in nice increase's in power and mixture
> range.  Also, the patents mention controls on when to plasma pump and when not
> to - just to reduce the electrical loss's to the system.  And yes, there is
> also discussion of reducing the resultant emi.
> 
> 
> 
> 
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