CA1245711A - Plasma jet ignition apparatus - Google Patents

Abstract

Abstract of the Disclosure A plasma jet ignitor apparatus for generating plasma from a plasma medium such as hydrogen and for discharging the plasma as a jet into the combustion chamber of an internal combustion chamber. The apparatus has a plug which has an electrode from which a high energy spark is generated. The spark causes hydrogen which is introduced into the plasma generation cavity by a fuel line to become plasma. The plasma generation cavity is defined by magnetic field generation means. The cavity has an inlet opening adjacent the plasma generation location and an outlet orifice. The plasma is ejected as a plasma jet from the cavity from the orifice. The magnetic field generation means is disposed as a magnetic field coil wound about the cavity. The magnetic field is charged by the discharge of a capacitor at the time of the formation of the plasma in the cavity. The magnetic field accelerates the plasma out of the cavity through the orifice so that the plasma exits as a high velocity jet and achieves effective penetration. Timing means are also included for timing the introduction of hydrogen into the cavity the discharge of the plasma generating spark and the triggering of the magnetic field.

Description

~2~57~

PLASMA JET IGNITION APPARATUS

Backaround of the Invention .
The present invention relates to an ignition apparatus and, more particularly, to a plasma jet ignition apparatus for generating and discharging a jet oE plasma for igniting fuel in combustion chambers of power sources such as inl:ernal combustion engines and the like.
Power sources such a~ internal combustion engines and the like rely on the combustion of fuel as their primary source of energy. This combustion usually occurs in one or more combustion chambers where the fuel is ignited by various ignition means. The fuel that is most often used for these powe~ sources are hydrocarbon based fuel6 such as gasoline and diesel fuel. In the past, the efEiciency of the power 60urces which u6ed these fuel6 was not as important as it ;s today. World events have made the crude oil from which many of those fuels are derived both expensive and in s.~arce supply. The need for refinement of that crude oil into various octane and cetane levels required for conventional ignition systems also adds to this expense. Additionally, environmental concerns. have also required that such power sources provide for improved ef f iciency and reduced emission of environmentally harmful exhaust by-products. This present 6ituation calls for higher efficiency engines and less costly fuels.
Efficiency can be improved and emissions reduced by the use of ~pecial materials and stLuctural changes to recuperate kinetic and thermal energies from the exhaust gasefi. Many attempt6 and de~igns have been directed to .

,~

~2~
this aspect of the problem. The other means for improving efLiciency and Leducing emissions is by the improvement of - the combustion process which can be accomplished through the use of efEicient igniti~n apparatus for the combustion of lean air/fuel mixtures. Present ignition systems use conventional spark plugs which discharge a high voltage-low energy spark oE approximately .1 Joules into-the combustible mixture. This spark ignites a small volume of the mlxture which in turn spreads through the volume of the mixture at the speed of the flame front to ignite the rest of the mixture. This mixture usually contains a high-octane gasoline fuel in a rich ai~/Euel mixture. Lean air/fuel mixtures do not burn as well because the flame speed of the front is reduced. Because the actual burning rate and i.gnition delay of this SySteln depends upon the physical chemistry o~ the Euel ex~remely sophisticated combustion charnber6 have been necessary to produce slight improvements in ignition delay and buLning rate. Additionally, high octane or high cetane fuels are needed which are more expensive and scarce. Moreover, because conventional spark plug ignition systems require relatively rich air/fuel mixtures for proper combustion it is important to precisely maintain this air/fuel mixture for efficient operation. Thus the conventional ignition systems limi-t the useful operating range of hoth low and high compression rati-o internal combustion engines and the like.
An ignition sy~tem that could reduce the fuel ignition delay and promote faster ~u~ning rates would improve fuel economy, reduce emissions, and extend the useful operating ~2~5i~
range of the engine in terms of the air/fuel mixture and also in terms of the types of fuel6 that could be used.
Running an engine with lean air/fuel mixtures presents numerous of the above advan~ages. The excess air provides for nearly complete combustion of hydrocarbons and carbon monoxlde which are usually released as exhaust gases. T~e greater dilution of the charge with a lean mixture resul~s in a lower peak temperature attained within the combustion chamber, This reduces the for`mation of nitric oxide pollutants, The ratio of specific heats of fuel-air rnixtures increases as leanec mixtures are employed. This means higher thermal efficiency at a given compres6ion ratio, Output power may be controlled by just the variation of the air/fuel ratio in a lean mixture, This avoids the use of a throttle,valve, which generaLly introduces pressure drops and a resulting decrease efficiency, Thus the use of lean mixtures results in a decrease in pollutant productlon and increases in efficiency.
~ s pointed out, conventional spark plugs do not, efficiently cause combustion of lean mixtures and either misfiring occurs or there is no combustion. The typical spark of a conventional spark plug is highly localized and ignites a very small volume of fuel in the general vicinity of the surface of the spark, The small initial flame front produced from the spark is slowed in lean mixtures resulting in long ignition delay and poor combustion because of insufficient penetration of the flame front into the volume of the lean mixture within the combustion chamber. For efficient burning of such ~LZ~7~

mixtures the flame speed must be increased.
The stratified charge engine is one s~ructure which - has been employed to attempt to gain the benefits of burning leaner air/fuel mi~tures. The basis of this design is to pro~ide for an initial combustion chamber in which a very rich air/fuel mixture is first ignited into a flame. Because of the pressure resulting from the chemical combustion this flame then entèrs the main combustion chamber to ignite a leaner mixture contained within the main chamber. The process requires chemical combustion in the initial chamber and the rest~ucturing of the basic design of various internal combustion engines so that this initial chamber is provided for. These engines also require additional components, valves, and other design changes to present eng.ines to allow for the use of the initial combustion of a rich mixture.
Another system for burning lean mixtures i8 based on the use of plasma jets. Basically these various systems create a jet of plasma which is introduced into the main combustion chamber. This jet causes the combustion of the fuel in the combustion chamber. The basic structure provides for an initial cavity in which a small amount of gas or the like is introduce~. This gas is subjected to an electric discharge of high energy. This causes the gas to become a hot ionized gas otherwise known as pla~ma.
Because of a great and quick buildup in pressure this plasma rushes out of an ori~ice in the cavity into the main combustion chamber as a jet or plume oE plasma.
Unlike the stratified engine flame this jet enters the combustion chamber at supersonic spee~s. The physical ~ 5~

chemlstry of this jet improves the ignition of lean mixtures because oE the velocity and penetration into the - chamber of the jet. Further the jet cause turbulence within the combustion chamber and this further enhances the combustion of the lean mixture6. These fluid mechanical effects of the plasma jet on ignition have an appreciable affect over an appreciable amount of time and thereby enhance the complete ignition and combu6tion of the lean mixture within the combustion chamber. The chemicaI effects on the'ignition occur because of heat of the plasma jet and because of the generation of free radicals in the plasma which react with the lean fuel mixture to increase combustion. Plasma jet ignition is also much less sensitive to ~iming so that this is a further impcovement over conv.entional spark plugs where efficiency is reduced if the timing i6 awry.
It has bee,n recognized in the art that a plasma jet ignition system would have many advantages for use in internal combustion engines. Plasma jet ignitors can be adapted to be placed into internal combustion engines with relative ease. They provide for controllable ignition factors, improve fluid mechanical aspects of ignition, and offer an excellent means by which lean mix~ures may be burned to extend the operating ranges of conventional engines. This of course provides all of the advantages of burning of lean mixtures in term6 of fuel savings an~
pollutant reduction. Plasma jet igniters are also less timing sensitive.
As has been pointed out the plasma medium, the magnitude and duration of the energy that generates the ~Z~57~
plasma, the size of the plasma cavity and the 6ize of the orifice all affect plasma jet ignition effectiveness. The - initial velocity of the plasma jet as it enters the main combustion chamber governs the penetration of the jet and its ability to cause turbulence and enhance combustion.
This velocity has been controlled by the dimen6ions of the plasma forming cavity and the ejection orifice. The duration and the amount of energy imparted to the plasma also governs the initial velocity. Higher energies must be discharged through the 6park plug electrodes than for conventional spark plug6 to generate plasma jets of sufficient pressure to be able to achieve the advantages of penetration and turbulence mentioned for enhanced combustion. These high energie6 tend to erode electrodes at a faster rate and to erode the orif;ce and cavity shape oE the plugs. The need to be able to place plasma jet plugs within conventional engines provldes constraints on the cavity and orifice size. Additionally the use of too high an energy level to crea-te the plasma increases the temperature and in some ins-tances this ;ncrease in temperature leads to the production of nitcous oxides.
The present invention provides for a plasma jet ignitor that can be easily adapted for use with internal combustion engines. It improves combustion and reduces pollutants by providing a jet of plasma that will ignite lean levels of fuel/air mixtures. The invention also provides for an external magnetic field mean6 to accelerate the plasma jet ~o that the jet achieves good initial velocity 60 that it achieves the appropriate penetration into the combustion chamber to provide ~or the 7~L~

most efficient combustion of the fuel mixture. Because of the use of external means to accelerate the jet, the cavity size and the orifice size are not as constrained.
Further the initial enregy needed for the electrode discharge does not need to be as great. This means,that the electrode life will be increased and that the temperature will not be as high thus reducing the creation of pollutants. Further advantages ancl features of present invention are discernable from the disclosure that follows.

57~

Summary of the Invention -Accordingly, an object of the present invention is to provide an improved plasma jet ignition apparatus.
According to one aspect of the invention there is provided a plasma jet ignitor apparatus for generating plasma from a plasma medium and for discharging said plasma as a jet, said apparatus comprising:
electrode discharge means for discharging energy to generate plasma from said plasma medium at a plasma generation location; means defining a plasma cavity, said cavity having an outlet orifice; and r,lagnetic field generation means for generat;ng a magnetic field to accelerate plasma in sai.d cavity out said outlet orifice so that a jet of plasma exits from said outlet ori.fice.
Related objects and advantages of the present invelltion will become apparent From t~e Fo:llow:ing -E:i.gures and detailecl description.

7~.
Brief Description oE the Drawinqs .

FIG. 1 is a partial side elevational view in cross section of a typical embodiment of a plasma je-t igniter according to the present invention.
FIG. 2 is a block diagram of a plasma jet ignition system according to a typical embodiment of the present - invention.

~2~5~
Description of the Preferred Embodiment For the purposes of promoting an understanding o~ the principles of the invention, reference will now be made to the embodiment illus-trated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
Referring to FIG. 1 there is shown the preferred embodiment of a plasma jet ignitor apparatus 10 for generating plasma from a plasma medium and for discharging the p].asma as a jet. 'rhe a~paratus 10 is useable with an internal combustion engine for generating a jet of plasma into a combustion chamber of the internal combustion engine to ignite a fuel in the combustion chamber. The present struc~ure as hereinafter described can be use.d to replace conventional spark plugs with the plasma jet ignition plug 11 shown in FI~. 1. Only the bottom yortion of th,e plug ll need be shown for an understanding of the invention because the upper portion ha~ the structure of any conventional spar.k pIug. Because the general external geometry of the plug 11 is like a conventional spark plug it.can be pl-a-ced in the conventional spark plug receptacle of a conventional internal combustion engine.

~ ~57~
The pluy 11 has a housing 12 which is made of metal and has means for attaching the ~lug 11 at a location - adjacent the combustion chamber of an in~ernal combustion engine. These means are the external screw threads 13 which mate with the threads of a conventional spark plug receptacle. Of course any other desired size of threads may be used. The housing has a central bore 14 in whieh~
electrode discharge means 15 are disposed within the housing 12 for discharging energy. The electrode discharge means 15 have a ceramic body 16 which is a cylinder of ceramic material which is received in the bore 14 of the housing 12. This ceramic body 16 has a central bore 17 in ~lhich an electrode 18 is disposed.
The electrode 18 has a discharge end 19 from which electrical energy is dischary~ed and a spark occurs in the ~park gap 20 between the electro'de end 19 and the ground electrode 21. This spark gap 20 is also adjacent the plasma generation location 22 at which the energy from ~he discharge of the electrode generates plasma from a plasma medium. The electrode discharge means further includes electrical means 23, as shown in FIG. 2 which is electrically engaged as shown diagrammatically at 24 with the electrode 18 for providing electrical energy to the electrode to cause a discharge of energy at the plasma generation location. As shown in ~IG. Z the source of the electrical energy is a conventional 12 volt power source -50. This source 50 is in e]ectrical engagement by line 53 with a trigger voltage source 54. Line 55 electrically connects the trigger 5~ with a high energy ignition coil 56 which is connected to distributor ~5 and then to the ~ s~
electrode. The functioning of this electrical Means in the preferred embodiment shall'be more fully explained hereinafter.
The electrode discharge-means includes plasma medium introduction means 25 as shown in FIG. 1 and 2. I'he plasma medium means ZS have a plasma medium passage~ay ~6 disposed in the housing 12. This passageway 26 has a plasma medium outlet opening 27 disposed adjacent the plasma generation location 22. The opposite second end-2a of the passageway 26 is disposed in flow communication with a plasma medium source 29 which contains a 6upply of plasma medium. Thereby a flow communication is established between the plasma medium source 29 and the plasma generation location 22 for introdu'cing plasma medium to the plasma generati~on location. As shown in FIG. 2 the plasma medium pafisageway 26 has a first solenoid valve 47, then an injection calibrated cavity 52 which holds a, in the preferred embodiment a calibrated amount of plasma medium for calibrated injection into the cavity 30. There is also a second solenoid val~e ~8 down the line before the passageway 26 enters the plug 12. The functioning of this plasma medium introducing means in the preferred embodiment shall be more fully explained hereinafter.
In the preferred- embodiment the plasma medium that is used is Hydrogen ga's. Other types of pIasma mediums are -of aourse possible. Hydrogen gas has been ~ound to reduce fuel ignition delay and to enharIce the combustion caused ' by the plasma generated from the hydrogen. Nitrogen may be used as the plasma medium if it is de6ired to reduce , 12 57~
nitrous oxides emissions. Fuel and water mixtures reduce hydrocarbon particulate emissions.
- As shown in FIG. 1 the plug 12 has a plasma generation cavity 30 at its lower end.- The cavity inner wall 31 is defined by a magnetic field generation means 33. The actual inner wall that is included as part of the magnetic field generation means, in the preferred embodiment, is an integral inner wall of the housing 12. An alternative design is to provide the inner wall as part of a shroud 32 that is securely attached to the housing 12 at its lower portion 34. The plasma cavity shroud 32 has an open portion 35 adjacent the plasma generation location 22.
The open portion 35 i6 adapted to be secured to the electrQde discharge means housing 12. The integral wall or the shroud provide two app.roaches by which the present invention can be achieved. one approach is the constructing of the magnetic field generation means integrally with-the-remainder of the plug 12. The other approach is the use of a shroud 32 which is attached to conventional plasma jet plug design so that the enhancement provided by the present invention's magnetic ield generation means, as hereinafter explained, may be realized for those plugs also.
The cavity 30, whether defined by the housing or the shroud wall, has an inlet opening or open portion 35 adjacent the plasma generation location 22. The cavity also has an outlet orifice di~charge means as 6ho~n by the orifice 36. The inlet opening or open portion 35 provideS
flow communication between the plasma gene~ation location 22, the cavity 30 and the cavity discharge orifice mean6 ]3 ~2~7:~
36. The cavity 30 shown in FIG. l has a conical shape 37 towards the orifice 36 and the orifice 36 has a conical - shape 3~3 towards the cavity 30. When the plug 12 is in an internal combustion engine the outlet orifice 36 is in flow communication with the combustion chamber so that the plasma jet goes from the cavity and into the combustion chamber to ignite the fuel in.the chamber. In the preferred embodiment, the cavity 30 has a volume of appro~imately 50 cubic millimeters and the orifice 36 has an open diameter 39 of l millimeter. Variations in the cavity size and orifice diameter are possible and such vari.ations will affect the velocity and penetration of the plasma je-t and such variations are intended to be within the scope of the present inven~ion.
The present invention pro~vides magnetic field generation means 33 for creating a magnetic field to accelerate the jetting of the plasma from the plasma generation location 22 through the cavity 30 and out the orifice 36 as a jet. The magnetic field generation means 33 includes a magnetic field coil 40 disposed about and defining the plasma generation cavity 30. This field coil 40 is embedded in the preferred embodiment in a ceramic cap 41. Thi6 cap 41 of cou~se can be integral with the plug housing 12 or it can be part of the shroud 32. The magnetic generation means 33 ~urther includes magnetic field electrical energy means 42 electrically engaged 43 -with the magnetic field coil 40 for introducing electrical energy into the field coil 40 to produce the desired magnetic field for the acceleration of the plasma out of the cavity 30 through the orifice 36. The electrical ' 14 ~'~4~7~L~
energy means 42 include the electrically engayement of the magnetic field coil ~0 with the triggering device 54 by line 59. The functioning of these electrical energy means 42 in the preferred embodiment shall be described below.
The preferred embodiment of the present invention also has timing means 44 and ~5 for timing the introduction of plasma medium by the plasma medium introduction means wi~h the dischaLge of -energy by the electrode discharge means with the acceleration of the pl-asma by the magnetic field generation means. The timing means include distributor 44 and distributor 95. Distributor ~4 is engaged w;th the plasma medium introduction means 25. One engagement is with a first solenoid valve 47 by line 96 and the second engagement is with solenoid valve ~B by line 99.
Distributor ~q is powered by .a conventional 12 volt power supply 50 through power line 51. Distributor ~5 i6 electrically engaged by line 57 with the high energy ignition coil 56 and electrically engaged with the electrodés 18 by line 5a. The timing means functioning for the preferred embodiment shall be more fully explained below.
The operation of the preferred embodiment will now be explained. Thé present invention provides for an apparatus and sy6tem for ejecting a jet of plasma into for example, a combustion chamber. This jet is accelerated by a combined action of a static pressure and an accelerating magnetic field. ~t the beginning of a cycle or initially the timing distributor ~ trigge-rs solenoid valve 97 and the plasma medium which is hydrogen flows from the plasma medium source 29 to the calibrated injection cavity 52.

, ~ 15 7~

At this time valve 4~ i6 already shut off. In the preferred embodiment the injection cavity holds - approximately .OS milligrams of hydrogen. Distributor 45 then shuts off valve 47 and-triggers solenoid valve 48 and the calibrated amount of hydrogen flows throug,h pas6ageway 26 and is introduced into the 50 cubic mil~limeter plasma generation cavity 30 from outlet opening 27. Distributo~
~5 is timed relative to distributor 4~ so that distributor 45 triggers the electrical means 23 for the electrode discharge means. This timing depends on the engine load but is usually only a few moments after the hydrogen enters the plasma generation cavity 30. In the preferred embodiment, this causes a high energy spark of approximately .7 joules to be discharged by the electrode lB at the plasma generation l~ocation 22. ~'his high energy 6park causQs the hydroqen to become a hot ionized gas otherwise known as plasma. In the preferred embodiment, due to the extremely short.deposition time of .
a~proximately S0 microseconds at which the electrical energy is discharged, an abrupt increase in temperature and pressure is caused within the plasma cavity 30. Since this pressure is much greater than the pressure outside of the cavity, the plasma generated i6 ejected from the cavity 30 through the orifice 36.
To improve~and control the penetrati-on of the jet so that the most effective penetration will occur the magnetic field means 33 is energized during the plasma formation. The magnetic field electrical.mean6 42 are connected to the power supply 50 through the trigger voltage source 54. The magnetic field electrical means 42 ` . 16 ~2~5~
at the time of the electrode discharge cause a large amount of energy, of approximately 10 joules, stored in a capacitor to be discharged into the magnetic field coil 40 which is wcund around the cavity 30. This creates an appreciable magnetic field which accelerates the plasma jet so that good penetration is achieved. With the dimensions recited herein as the preferred embodiment the plasma jet has been ejected by this invention to an approximate depth of 5 centimeters within a combustion chamber. Thereby good combustion results due to increased flame speed, turbulence, and larger flame front resulting in multi-point ignition.
While the invention has been illustrated and described in detail in the drawings and foregoing descrip~ion, the same is to be considered as i~llu6tralive and not restrictive in char.lc~.er, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.

Claims (13)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A plasma jet ignitor apparatus for generating plasma from a plasma medium and for discharging said plasma as a jet, said apparatus comprising:
electrode discharge means for discharging energy to generate plasma from said plasma medium at a plasma generation location;
means defining a plasma cavity, said cavity having an outlet orifice; and magnetic field generation means for generating a magnetic field to accelerate plasma in said cavity out said outlet orifice so that a jet of plasma exits from said outlet orifice.

2. The plasma jet ignitor apparatus of claim 1 wherein said electrode discharge means includes plasma medium introduction means having a plasma medium passageway in flow communication with said plasma generation location for introducing plasma medium to said plasma generation location.

3. The plasma jet ignitor apparatus of claim 1 wherein said magnetic field generation means includes a magnetic field coil disposed about the exterior of said plasma cavity, and said magnetic generation means further includes magnetic field electrical energy means engaged with said magnetic field coil for introducing electrical energy into said field coil to produce said magnetic field.

4. The plasma jet ignitor apparatus of claim 1 wherein said electrode discharge means includes an electrode having a discharge end, said discharge end being disposed adjacent said plasma generation location; and said electrode discharge means further includes electrical means electrically engaged with said electrode for providing electrical energy to said electrode to cause a discharge of energy at said plasma generation location.

5. The plasma jet ignitor apparatus of claim 2 wherein said plasma medium introduction means includes a plasma medium outlet opening disposed adjacent said plasma generation location, a plasma medium source, and said plasma medium passageway having a first end in flow communication with said plasma medium source and a second end in flow communication with said plasma medium outlet opening.

6. The plasma jet ignitor apparatus of claim 2 further having timing means for timing the introduction of plasma medium by the plasma medium introduction means with the discharge of energy by the electrode discharge means with the acceleration of the plasma by the magnetic field generation means.

7. A plasma jet ignitor apparatus for use in an internal combustion engine for generating a jet of plasma into a combustion chamber of the internal combustion engine to ignite a fuel in said combustion chamber, said apparatus comprising:
a housing having means for attaching said housing adjacent said combustion chamber:
said housing having an interior wall defining a plasma generation cavity disposed within said housing;
plasma medium introduction means for introducing plasma medium into said plasma generation cavity;
electrode discharge means for discharging energy within said plasma generation cavity to generate plasma from said plasma medium:
discharge orifice means in flow communication with said combustion chamber for jetting said plasma out of said plasma generation cavity in the form of a plasma jet into said combustion chamber: and magnetic field generation means for creating a magnetic field to accelerate said jetting of said plasma out of said plasma generation cavity into said cylinder combustion chamber.

8. The plasma jet ignitor apparatus of claim 7 wherein said magnetic field generation means includes a magnetic field coil disposed about the exterior of said plasma generation cavity, and said magnetic field generation means further includes magnetic field electrical energy means engaged with said magnetic field coil for introducing electrical energy into said field coil to produce said magnetic field.

9. The plasma jet ignitor apparatus of claim 8 wherein said electrode discharge means includes an electrode having a discharge end, said discharge end being disposed within said cavity adjacent-said interior wall; and said electrode discharge means further includes electrical means for providing electrical energy to said electrode to cause a discharge of electrical energy into said chamber adjacent said discharge end.

10. The plasma jet ignitor apparatus of claim 9 wherein said plasma medium introduction means includes a plasma medium outlet opening disposed in said interior wall, a plasma medium source, and a plasma medium passageway having a first end in flow communication with said plasma medium source and a second end in flow communication with said plasma medium outlet opening.

11. The plasma jet ignitor apparatus of claim 9 further having timing means for timing the introduction of plasma medium by the plasma medium introduction means with the discharge of energy by the electrode discharge means with the acceleration of the plasma by the magnetic field generation means.

12. A plasma jet ignitor shroud for a plasma jet igniter apparatus for generating plasma from a plasma medium and for discharging said plasma as a jet, said apparatus having electrode discharge means for discharging energy to generate plasma from said plasma medium at a plasma generation location, said shroud comprising:

magnetic field generation means having a plasma cavity shroud, said cavity shroud having an open portion adjacent said plasma generation location, said open portion being adapted to be secured to said electrode discharge means, said cavity shroud further having an outlet orifices, said open portion providing flow communication between said plasma generation location and said cavity:
said magnetic field generation means being for generating a magnetic field to accelerate plasma in said cavity shroud out said outlet orifice so that a jet of plasma exits from said outlet orifice.

13. The plasma jet ignitor apparatus of claim 12 wherein said magnetic field generation means includes a magnetic field coil disposed about the exterior of said cavity shroud, and said magnetic field generation means further includes magnetic field electrical energy means engaged with said magnetic field coil for introducing electrical energy into said field coil to produce said magnetic field.