WO1993010348A1

WO1993010348A1 - Plasma-arc ignition system

Info

Publication number: WO1993010348A1
Application number: PCT/CA1992/000510
Authority: WO
Inventors: John Paterson
Original assignee: Ortech Corporation
Priority date: 1991-11-22
Filing date: 1992-11-23
Publication date: 1993-05-27
Also published as: CA2124070C; CA2124070A1; GB9124824D0

Abstract

An ignition system for igniting fuel within an engine cylinder, comprising: at least one ignition plug disposed in the cylinder; high-voltage pulse generator means connected to the ignition plug for generating a pre-pulse of static charge within the cylinder so as to ionize the fuel in the engine cylinder and thereby increase conductivity thereof, the pre-pulse comprising a high negative voltage high frequency burst of full-wave rectified alternating current; high-current pulse generator means connected to the ignition plug for generating a high-current pulse within the engine cylinder so as to form a plasma adjacent the plug for initiating combustion of the fuel within the engine cylinder; and controller means for selectively enabling and disabling the high-voltage pulse generator means and the high-current pulse generator means at predetermined times.

Description

PLASMA-ARC IGNITION SYSTEM Field of the Invention

This invention relates in general to ignition systems in fuel powered engines. More particularly, the invention relates to an electrical current-generated plasma and ignition system for gas powered engines. Background of the Invention

Existing spark-ignition systems for automobiles date back to about 1905. Although modern materials such as plastics and semiconductors have been used to improve the efficiency of the sparking coil, there has been little improvement to the basic principle, which provides for a 30 KV spark across two electrodes in the gasoline cylinder of the engine to ignite the fuel mixture. The single point ignition process effected by well known prior art spark plugs results in a slow moving flame-front across the engine cylinder. The speed of combustion resulting from this slow moving flame front necessitates advancing initiation of the spark as the engine speed increases, resulting in loss of power.

As is well known, diesel engines do not use spark plugs. Instead, fuel is injected into a preheated cylinder and exploded by heat of compression. Similarly, high performance racing engines use glow plugs and doped methane fuels which tend to auto-ignite in a similar manner as the diesel principle, thereby achieving efficiency and performance significantly higher than spark ignition gasoline engines. In the field of radio frequency electronics, it is a well known principle that A.C. coupling on transformers improves in proportion to f², where f represents frequency, and that use of a resonant transformer at radio frequencies will result in the generation of extremely high voltages.

Furthermore, it is known from semiconductor processing electronics that high voltage radio waves will excite gases under pressure, and that if the input radio energy is high enough, the radio waves will strip electrons from the gas molecules, and cause ionization of the gas into a plasma mixture which can be heated by electrical currents. If the plasma mixture consists of two combustible mixtures combined in the correct proportions, then the mixture will explode under plasma heating.

By the late 1970's, the effectiveness of the plasma jet igniter as conceived by L. Gussak, L.A. Gussak, USSR., Energetikco Transport Academy Izvestijia (1965), Vol. No. 4, pp. 98-110 "New Principle of Ignition and

Combustion in Engines", was well accepted; although the practical aspects of its application to engines required engineering research to qualify data on fuel economy, emissions and the LML. A number of outstanding we11-documented projects, have exposed the geometry of the plasma jet igniter nozzle-cavity, the electromagnetic energy-package stressed into the cavity, the time-scale of the pulse, and the velocity of the blast-wave and jet plume ejected from the nozzle cavity.

During this period, the.work of J.D. Dale at the University of Alberta, Edmonton, A.K. Oppenheim at the University of California, Berkeley, and D. Fitzgerald at Jet Propulsion/CALTECH stand out as definitive, authoritative work leading to a true understanding of the application, benefits and superiority of plasma jet ignition over conventional spark ignition, for low- emission lean-burn engines. It was found, for example, that there was a direct correlation between reducing NO_x emissions/specific lb/hr. fuel consumption and increasing the air-fuel equivalence ratio; this was known from earlier engine experiments, but had tended to be limited to E=0.7 because of the misfiring caused by the inability of conventional spark ignition to initiate combustion consistently.

Application of plasma jet ignition to the misfiring problem at the Lean Flammability Limit (LFL) showed that the equivalence ratio could be easily pushed to E=0.5 (air/fuel=20:1 in the case of air-methane mixtures), see SAE 780637, A.K. Oppenheim, K. Teichnao, K. Horn, H.E. Steward, "Jet Ignition of an Ultra-Lean Mixture." In two cases, SAE 850077, C.F. Edwards, H.E. Stewart, A.K. Oppenheim, "a Photographic Study of Plasma Ignition Systems", and SAE 810146, J.D. Dale, A.K. Oppenheim, "Enhanced Ignition for IC Engines with pre-mixed gases", Oppenheim, Edwards and Stewart showed that for the propane/air mixture used in their tests a typical spark plug permitted lean operation down to the equivalence ratio of 0.7, after which mis-ignition occurred. The standard plasma jet igniters provided an extension of the lean limit to an equivalence ratio of 0.5 and it seemed that this limit was imposed by either extinction of the flame or too slow burning rate, rather than by misfire. A minor section of this investigation noted that a plasma jet igniter with an HC-substance accelerator feedstock achieved an equivalence ratio of 0.4. U.S. Patent 4,996,967 (Cummins Engine Company, Inc.) discloses an apparatus and method for generating a highly conductive channel for the flow of plasma current, in which a pre-pulse is utilized to ensure that an ionized channel is developed to a significantly conductive state prior to application of a sustaining voltage for sustaining plasma flow through the channel. However, according to the '967 Patent, the pre-pulse signal is in the form of a simple DC pulse. It has been found that the use of a single DC pulse does not provide the best possible efficiency for ensuring complete ionization prior to onset of the plasma current. Brief Description of the Drawings

A further discussion of the prior art as well as a description of the present invention are provided herein below with reference to the following drawings in which: Figures 1A and IB show a typical combustion cycle of a modern internal combustion engine; Figures 2A and 2B show a typical modern electronic ignition system and timing waveforms respectively;

Figures 3 and 3B show waveforms and spark current according to typical modern electronic ignition systems; Figure 4 is a block diagram of a plasma-arc ignition system according to the present invention;

Figure 5 is a block diagram showing closed loop control of the high-current generator using a current probe; Figure 6 shows typical RMS values of leakage current during a spark voltage pulse of the plasma-arc ignition system of the present invention;

Figure 7A is a pulse-timing diagram for the plasma- arc ignition system according to the present invention; Figures 7B, 7C and 7D show the high voltage pulse, the resulting ionization current and arc current according to the preferred embodiment.

Figure 8A is a schematic diagram of a high-voltage generator according to an alternative embodiment; Figure 8B shows the signal output from the high- voltage generator of Figure 8A, and ionization current plotted with respect to time;

Figure 9A is a schematic diagram of a high-current generator according to the peferred embodiment; Figure 9B is plot of current gain amplitude by frequency for the high-current generator of Figure 9A; Figures 9C and 9D show maximum and minimum output current signals, respectively, from the high-current generator of Figure 9A; Figure 10A is a cross sectional view of a conventional plasma jet igniter;

Figure 10B is a schematic representation of a basic jet plume generated by the plasma jet igniter of Figure 10A; Figure 11A is a cross sectional view of a plasma jet igniter with toroidal vortex generator according to the present invention; Figure 11B is a detailed view of a portion of Figure 11A;

Figure 11C is a schematic representation of a toroidal jet with immediate vortex ring effects produced by the plasma jet igniter of Figures 11A and 11B;

Figure 12 is a cross-sectional view of a plasma jet igniter with vortex generator and contained substance for creating multi-point ignition sources within the vortex toroid, according to an alternative embodiment of the invention;

Figure 13 is a cross-sectional view of a plasma ball igniter according to a further alternative embodiment;

Figures 14A-14D show additional modifications of the plasma ball igniter of Figure 13; Figures 15A-15D are schematic representations of the plug body and plasma ball generated by various multi-port plasma ball igniter variants;

Figure 16A is a cross sectional view of a plasma jet igniter with D-shaped electrodes according to a further alternative embodiment; and

Figure 16B is an end view of the plasma plug shown in Figure 16A, and Figure 16C is a schematic representation showing location of a plasma body (elliptoid) generated by the plasma plug of Figures 16A and 16B.

Detailed Description of the

Preferred Embodiment and of the Prior Art

Figure 1 shows the typical combustion cycle of a modern 6-cylinder 3.3 litre gasoline fourstroke internal combustion engine, with the different timing effects on the combustion process at 1000 rpm and 6000 rpm. The red-line for engines in normal use occurs at 6000 rpm, while 1000 rpm is slightly over the off-load idle condition. Figure 2A shows the typical modern electronic ignition system used to create the ignition spark, and Figure 3 shows the typical waveforms and current of the spark.

Referring to Figure 2A, the general characteristics of existing systems of spark formation is based on a high-voltage step-up transformer Tl from the 12V battery supply, using the slow charge of a capacitor Cl up to 12V through transistor Ql. This occurs during the "off" cycle between Top Dead Centre (TDC) pulses. The charging circuit has to be designed such that the capacitor Cl can be fully charged between sparks at the maximum speed of the engine, which allows about 20 milliseconds (0.020 sec) for full charge. At the TDC pulse spark time, the pulse triggers the discharge circuit Q2, which allows the capacitor Cl to discharge its current rapidly through the primary of transformer Tl, which typically has a step-up ratio of 100:1. The rapid discharge of current through the primary coil of Tl coupled with the resonance effects caused by the LC combination of Cl-Tl reactances multiply the circulating current by up to 20 times, resulting in the 25-30KV spark. The Tl secondary coil may be manufactured with additional or designed-in capacitances (shown dotted) to cause resonance effects in the secondary windings of Tl (the high-voltage side) . Once the discharging of Cl is complete, the sparking cycle is over, and Cl starts charging again. Figure 3 shows the typical structure of the spark so generated.

Measuring the voltage from the transformer Tl, it quickly rises in about 25 useconds (.000065 sees) to about 25Kv at which point ionisation of the gases in the cylinder starts to occur and leakage current increases dramatically, causing self-resonance conditions in the transformer Tl. These resonances remain a further 35uS as the discharge dissipates from the capacitor Cl and self-oscillation of Tl causes alternating peaks of voltage. The current pulses which are created in the ionised gases in the cylinder cause ignition by Joule- heating effects, generally termed minimal arc-heating. The combination of current pulses, and the high-voltage coil Tl with its high-resistance leads to the plugs is essentially a self-quenching cycle; it begins with the high-voltage pulse causing ionisation, which causes current to flow in the gas, which increases back-e f in Tl, which reduces the high-voltage pulse, which extinguishes the leakage arc, which allows the high- voltage pulse to reappear, and the cycle repeats until all of the energy stored in capacitor Cl is dissipated. The typical advantages of such ignition systems are that they are simple, low-cost and safe. Inherent high- resistance in Tl is claimed as a safety feature, together with the high-resistance plug-leads, and it is true that one cannot be burned or receive dangerous shocks from these spark-ignition systems. However, the inherent high-resistance of all of the components prevents efficient delivery of higher energies to the spark plug tip. The typical energy delivered per spark is about .030 Joules, whereas the typical energy stored by the capacitor Cl is about .090 Joules, so that the process is seen to be only 33% efficient.

Referring again to Figure 1, which shows the typical combustion cycle for a four-stroke engine, it can be seen that at 1000 rpm (slow speed, no-load) conditions appear to be near ideal (Figure 1A) : rotation speed is 170 usec per degree spark time of 11 usec = .58 degree advance of 3 degrees is all that is needed combustion flame burning time takes 1.5 mil sec = 8.8 degrees

However, at mid range, 3000-6000 rpm (max speed, full load) conditions are marginal (Figure IB) : rotation speed is 28 usec per degree spark time is 100 usec = 3.6 degrees advance of 9 degrees needed (3000 rpm) advance of 18 degrees needed (6000 rpm) combustion flame burning time takes 1.5 milsecs =

53.6 degrees (6000 rpm)

The inventor has recognized that significant improvements can be made. Firstly, the spark time can be shortened to 50 usecs. Increased energy can be delivered to spark to .090 Joules, or higher, and the flame combustion time can be shortened to 0.5 milsecs (28 degrees at 6000 rpm) .

From these improvements it is expected that the spark-advance can be reduced at high speeds, giving some increase in efficiency; combustion can be initiated nearer to TDC at all times, and burn faster; some fuel efficiencies will be achieved (or power improvements accepted) ; and emissions behaviour of exhaust gases may be improved.

Considerable prior art literature is available on the subject of spark ignition systems. The existing prior art can be classified generally into the following types (some of which are in use, others of which are not) :

(a) minor changes to spark plugs (NGK split-fire) ;

(b) substitution of electronics for spark-gap points;

(c) addition of voltage-doublers to +24V to increase capacitor charging;

(d) uses of coaxial cable radio and radio-frequency energy pulses;

(e) uses of microwave plumbing and microwave frequency pulses; (f) uses of resonant chambers associated with the piston and cylinder diameters and radio and microwave f equencies;

(g) uses of special plugs and extensive modifications to the plug electrodes; (h) uses of charged-capacitance transmission-line in plug-leads and capacitor load in spark-plug; (i) modifications and adaptation of semi-conductors to means of spark distribution;

(j) modifications of spark-plug leads for high resistance; (k) mechanical modifications to introduce automatic advance with engine speed;

(1) electronic modifications to replace mechanical spark advance timing;

Most of the inventions which have been adapted for use are simple, easy to manufacture, and easy to install. The prior art of the time has been advanced in a modest way, without any changes to the engine structure. Some examples are the use of semi-conductors and capacitor discharge ignition (CDI) to replace the spark-gap points, and electronic timing advance to replace the vacuum mechanical advance methods.

Most of the inventions which have not been adapted for use in engines required major modifications to the cylinder/pistons and/or additional combustion chambers. Where as most of the prior art relates to functional improvements in spark ignition technology, the present invention is directed to the problems of (1) controlled spark timing to achieve optimum engine combustion over a wide range of engine types, fuels and atmospheric conditions; (2) accelerated Joule-heating effect to the air-fuel mixture, to reduce combustion time and therefore reduce spark advance needed at higher speeds; and (3) adaptable spark timing, adaptable Joule-heating and duration to minimize emissions products over a range of engine operating conditions, and (4) possible full-stroke ignition timing to bottom dead centre (BDC) for the purpose of continuing combustion during the working stroke in four-cycle engines to ensure complete combustion of all hydro-carbon products. Turning to Figure 4, a plasm-arc ignition system is shown according to this invention having separate high- voltage generator 1 and high-current generator 2 for the purpose of producing controlled timing of the start of combustion, and faster and cleaner burning of the air- fuel mixture. In conjunction with this improvement, it is a further object of an aspect of the invention to provide an Ionisation Current Detector (ICD 3) by means of which ionisation current can be detected during the high voltage pulse, and used as additional information control to start the high current pulse.

Therefore, according to the present invention, a micro-controller plasma control system 4 is provided for receiving engine operation parameters such as RPM and TDC timing, as well as manifold air density, and in response generating trigger pulses for selectively enabling and disabling the high-voltage generator 1 and high-current generator at predetermined times. The micro-controller 4 preferably includes a microprocessor for integrating the received data, and calculating appropriate timing signals for the start of the current arc, amount of current and duration of the arc on the basis of empirical formulae operating on the receiving engine parameters. This optimizes the amount of advance required to a minimum, and optimizes to a maximum the amount of energy coupled to the combustion flame-front for accelerating combustion. The ionization current detector 3 provides output signals to both the micro-controller 4 and the high- current generator 2. The purpose of its input to the micro-controller 4 is to signal readiness to turn-off the high voltage pulse while ionization is occurring. The purpose of the signal into the high-current generator 2 is to trigger it to provide the high-current pulse, which is controlled in amplitude and frequency by the input from the micro-controller 4, which is based on empirical formulae using engine-map data. The high-voltage generator 1 receives the plasma timing pulse from the micro-controller 4 and immediately initiates an alternating high voltage discharge at approximately 35 KV and 500 kilohertz via a distribution system 5 which is connected to plasma plug 6 within engine cylinder 7 (fuel and exhaust ports have been omitted from the schematic representation of cylinder 7 for the purposes of clarity) .

The ionization current detector is connected to a sensor 8 which is connected in series with the high- voltage generator 1 and distribution system 5. The ionization current detector 3 detects when the small leakage current around the plasma plug 6 suddenly increases, which is indicative of a change from the typical spark plug leakage current to the ionization break down associated with- an actual spark (in an SI system) . In a PJI system, it is at this time that the conditions exist for a plasma to be formed and subsequently maintained. This current boundary varies widely over the life and type of engine because it is mainly dependent on type of fuel used, and atmospheric conditions such as cold, dry air or warm, wet air. The ionization signal is sent to the controller 4, which in response immediately enables the high-current generator 2 for generating plasma current.

High current generator 2 receives the trigger pulse from ionisation detector 3 and magnitude control signal from controller 4 to start the plasma current, as well as further data defining the maximum plasma current and duration of the plasma pulse. A high voltage blocker 9 prevents feed-back of the high voltage pulse into the circuits of the current generator 2 which could otherwise be damaged. The plasma plug 6 and distribution system 5 are provided with a dedicated plasma current return circuit which does not simply connect to the engine block and chassis. The distribution system 5 distributes the plasma energy to the plugs (only 1 plug being shown for ease of illustration) , and as such is required to be a very low impedance device. The plasma plug 6 is discussed in greater detail below.

Turning to Figure 5, a circuit is shown for precise control of the plasma current by means of a current probe or current sensor 10, such as a Hall Effect sensor, to provide feed-back control in an error driven closed-loop circuit. This circuit is shown as comprising an analogue to digital converter 11 connected to the current sensor 10 for receiving and digitizing the current output from the high-current pulse generator 2 and generating an actual current data signal in response thereto. A subtractor 12 is connected to the output of analogue-to- digital converter 11 as well as to the controller 4 for subtracting the current demanded from the actual current data signal and in response generating an error signal. A digital-to-analogue converter 13 receives and converts the error signal to analogue form and in response generates the output current.

Figure 6 shows an analysis of typical RMS values of leakage current during the system's spark voltage pulse. It should be noted that the -time scale is approximately lOOusec (.0001 sec). Ionisation currents on the order of 10 MA (O.lOamp) flow before an arc can be formed in the air-fuel gas mixture. The conditions of the induced air and the fuel composition affect the ionisation current in the following ways:

0. For "dry gaseous fuels", such as methane, propane: 0 Cold moist air has high moisture content (1000 particles per cc) and readily produces ionisation current 0 Hot dry air has zero (or very low) moisture content and it is difficult to produce ionisation current, except with maximum voltage stress of 200 V per mm per atmosphere 0 Gas flash point is much higher than gasolines, so higher temperatures are required to initiate and continue combustion 0 Gases have a cooling effect on the intake, which tends to make ignition slower

0 Over a wide range of ratios from "rich" to stoichiometric to "very lean", the air-fuel mixture ranges from 85% to 96% air, but the "wetness" of the air-fuel mixture is dependent on the atmosphere, not on the fuelling ratio

2. For "wet" fuels such as the gasolines, alcohols: 0 Fuel enters as a particulated aerosol, mixed with air, but has "wet" properties which helps ionisation of the air-fuel mixture

0 Aerosol evaporation is slowed by increasing compression of the engine up to TDC 0 Cold moist air has high moisture content (as described above) and readily produces ionization current

0 Hot dry air has zero moisture content but is moderated by the "wetness" of these fuels, in an air-fuel mixture 0 Very rich starting conditions can provide "too- wet" combustion chamber conditions when coupled with cold moist air, and "wet" the plug to the point where the lowered resistance is too low for existing coil types, and their spark energy is dissipated internally The differences in these conditions can cause incorrect working of the high-voltage pulse-system, such that if it is adjusted to suit hot dry air (i.e. a prolonged high-voltage pulse) , it will burn the plug electrodes in cold moist air conditions. Further, if the high-voltage pulse is set to suit the moist air conditions it will not generate enough ionisation current in the hot dry air conditions. These differences in timing needed for ionisation to reach the trigger level in various air conditions are compensated for in the Ionisation Current Detector (ICD3) of the present invention. The ICD3 of the present invention is designed to be sensitive to the level of the ionisation current at the plug gaps, as an indication of the breakdown voltage point of the various air-fuel mixtures and chamber pressures. According to the present invention, the level of ionization current is a standard measure for, and allowance of, predetermined leakage current through the plug-leads and plugs, which do not form part of the ionisation current and do not contribute to the air-fuel ionisation process. Figure 7A shows the control timing of the high- voltage pulse, resulting ionization current, ionization current detector pulse and plasma current pulse for the circuit of Figure 4. In particular, once the ionization threshold has been detected by ionization current detector, high current generator 2 is enabled for starting generation of plasma current, and once plasma current flow is detected, the high voltage generator 1 is disabled via micro-controller 4.

Figures 7B, 7C and 7D show the high-voltage pulse, the resulting typical ionisation current, and the Joule- heating plasma-arc current in greater detail. A rectified sinusoidal alternating system is used with harmonic content lower than 0.1%, to generate high voltage by means of a resonating high-Q transformer at high-frequency. Such harmonic purity prevents energy losses and waveform distortion, and maintains the highest voltages possible. High frequency is used and controlled by the high-voltage pulse generator 1 (Figure 4) to run for a specific number of cycles, until the ionization current reaches the trigger level for a plasma-arc to be initiated. The Ionisation Current Detector (ICD 3) then outputs a trigger pulse to the High-Current Pulse Generator 2. A pure sinusoidal alternating system is used with harmonic content less than 1% to generate the high-current pulse by means of a resonating current transformer with high-Q and low losses. Turning to Figure 8A, a high voltage generator according to an alternative embodiment is shown for generating a full wave rectified negative high voltage pre-charge pulse. The system of Figure 8A comprises a high frequency oscillator 80 for receiving an on/off trigger signal from the micro-controller 4, a tuned transformer 82, which is adapted to resonate at 500 kilohertz (i.e. the frequency of the signal output from oscillator 80) , and a full-bridge rectifier 83 for converting the resulting high voltage sinusoidal waveform into the full wave rectified signal of Figure 8B. The output from bridge 83 is connected to the central electrode and side electrode of a suitable plasma plug (see Figures 10-16) .

Figure 9A shows a block diagram for high current generator 2. The circuit comprises a variable frequency oscillator 90 for receiving .an/off trigger signal from controller 4 as well as demand current amplitude. The output of oscillator 90 is connected to a tuned transformer 92 which, in turn, is connected to the central and side electrodes of a suitable plasma plug

(see Figures 10-16) . The high current pulse (Figures 9C and 9D) provides the arc current necessary to maintain the plasma by means of the resonating high-Q low loss current transformer 92 operating at the desired frequency in the range of 50 to 150 kilohertz. The frequency is preferably selectable in order to take advantage of operational benefits which may be identified with specific frequencies in this range.

High intensity Joule heating effects are caused in the plasma arc channel by the generation of the high current pulse at the plasma plug electrodes. The high current generator circuit of Figure 9A delivers a predetermined number of precise current pulses each up to 20 amps with a resolution to fractions of an amp. The pulse shape and therefore the energy input, are determined by the micro-controller 4 from monitored engine parameters and internal look-up tables. Precise control of the current is also achieved by the feed-back control system discussed above with reference to Figure 5.

Figure 9B shows current gain amplitude for the high- current generator 2 of Figure 9A as a function of frequency.

The plasma-arc Joule-heating pulse complies with such prior art approaches as Tungsten Inert Gas Welding (TIGW) of which the primary parameters for the present invention are:

0 Modifications of spark plug structure and material 0 Precise control (+/- 1%) of plasma-arc current materials 0 Precise control (+/- 8%) of plasma-arc current duration 0 Precise AC balancing of the plasma-arc positive and negative current Plasma-arc physics are used in the present invention for creating high-intensity Joule-heating effects in the plasma-arc channel formed by the High-Current Pulse at the spark plug tips, in a variety of embodiments (Figures 10-16) , so that a range of precise heat pulses can be delivered to the combustion chamber, as required by the specific engine type, and operating conditions and fuel, as defined by the Spark Advance Timing Algorithm.

In the limited dimensions of the spark plug gaps in the various embodiments illustrated in Figures 10 to 16, the typical resistance of the plasma-arc channel when heated and established is in the range 0.5 ohms to 8.5 ohms, and is capable of carrying plasma-arc current in the range 2 amps to 150 amps. The lower levels of current have been proven, by experiment, to be unstable and too weak to sustain Joule heating, whereas the higher currents at 90 amps and above are too powerful and can cause plug damage at higher rpm. Figure 10A is a cross-sectional view of a conventional plasma jet igniter or plasma plug, comprising a central electrode 111 of copper and nickel, a standard plug steel body 112, standard plug washer 113, the steel body 112 having a threaded fit 114. A central insulator 5, preferably of alumina, surrounds the central electrode 111, and an additional epoxy fill 6 is provided in the cavity behind insulator 115. Preferably, a cavity 117 is drilled out in central electrode 111 (approximately 2 mm deep) . An end plate 118 is provided (preferably fabricated of HS-14 steel silver-brazed to plug) , having a cavity orifice 119 of approximately 2 mm diameter, 45° bevel.

Figure 10B shows the basic jet plume produced by the standard plasma plug of Figure 10A. Turning to Figures 11A and 11B, an initial variant to the basic plasma plug is provided in accordance with the present invention. Reference numerals 111-115 designate parts which are similar to those of the standard plasma plug shown in Figure 10A. However, according to the illustrated variant, epoxy 116A is provided for filling the rear cavity, add-on tungsten button 117A is provided with chamfered edge to create a stress field at "A". An end plate 118 is provided in the usual manner, with annular gap 119A. However, according to the variant illustrated, a toroidal centre piece 110 is provided for creating vortices. The centre piece 110 may be fabricated from ceramic alumina, with epoxy to the central electrode ill.

Figure lie shows the toroidal jet created by the plasma plug design of Figures 11A and 11B, showing immediate vortex ring effects. Figure 12 illustrates an alternative plasma plug design according to the invention, comprising a central electrode 111, parts 112-115 being identical to the conventional parts discussed above with reference to Figure 10A, epoxy fill 126 having a surface which faces the plasma arc area (A) and which is parabolic, the focus of which is identified by reference mark X and reference numeral 129. An add-on tungsten button 127 with chamfered edge is provided to create the stress field at "A". End plate 128 is provided in the usual manner, the gap identified as the focus point X (reference numeral 129) can be optimized and shaped by formation of the centre piece 110 so as to shape the plasma jet and direct it into a vortex. The centre piece 110 is preferably ceramic and may be of suitable size and shape. A recessed groove 121 is provided for containing an organic catalyst for creating multi-point ignition sources within the vortex toroid. The organic catalyst may be described in generic form as 'C_NH_2N- 0_N, where C_NH_2N is a poly erizable compound where N is greater than 12, and 0_N is physically absorbed in the compound.

Turning to Figure 13, a plasma ball igniter is shown according to a further aspect of the present invention having a central electrode 111, standard parts 112-115, epoxy 116 to fill the gap, and a tip 137 which may have different shapes (e.g.- rounded, multi-point, etc.), according to specific geometries for open-plasma. The ring electrode 138 is preferably provided with eight points (tungsten - 2% thorium alloy) . Reference numeral 139 designates the locations (A) of the main arc channel. Turning to Figures 14A-14D, there is shown a plurality of embodiments of plasma-plug according to the principles of the present invention. For example, according to Figure 14A a central angular tip electrode is shown surrounded by an alumina insulator (AL₂0₃) which is in turn surrounded by a steel jacket-threaded body. A pair of side electrodes extend from the steel body and are provided with rectangular faces. In Figures 14B and

14C, plasma-plugs are illustrated having three electrodes and four electrodes, respectively. A plasma arc is generated between the electrodes of the plasma plugs of Figures 14B and 14C as illustrated in Figures 15B and

15C, respectively.

Thus, the multi-port embodiment of Figures 14A-14D incorporate multiple side electrodes for distributing the generated plasma arc. The embodiment of Figures 14D and 15D utilizes pointed tip side electrodes in number up to sixteen. Figures 16A to 16C shows a further alternative embodiment of plasma plug having D-shaped electrodes 161 and 162 each of equal area. In all other respects, the plug of Figures 16A-16C incorporates well known components identified by reference numerals common with

Figures 10-13.

Other modifications and variations of the present invention are possible without departing from the sphere and scope of the invention as defined by the claims appended hereto.

Claims

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

1. An ignition system for igniting fuel within an engine cylinder, comprising: a) at least one ignition plug disposed in said cylinder; b) high-voltage pulse generator means connected to said ignition plug for generating a pre-pulse of static charge within said cylinder so as to ionize said fuel in said engine cylinder and thereby increase conductivity thereof, said pre-pulse comprising a high voltage high frequency burst of alternating current; c) high-current pulse generator means connected to said ignition plug for generating a high-current pulse within said engine cylinder so as to form a plasma adjacent said plug for initiating combustion of said fuel within said engine cylinder; and d) controller means for selectively enabling and disabling said high-voltage pulse generator means and said high-current pulse generator means at predetermined times.

2. The ignition system of claim 1, wherein said controller means selectively enables and disables said high-voltage pulse generator means and said high-current pulse generator means at said predetermined times in accordance with one or more engine operation parameters.

3. The ignition system of claim 1, wherein said controller means enables said high-voltage pulse generator means for a predetermined number of cycles of said alternating current in accordance with engine fuel- charge requirements.

4. The ignition system of claim 1, further comprising an ionization current detector connected to said high-voltage pulse generator means and said controller means for detecting ionisation current resulting from said pre-pulse and in response enabling said high-current pulse generator means and causing said controller means to disable said high-voltage pulse generator means.

5. The ignition system of claim l, further comprising a current probe connected to an output of said high-current pulse generator means for sensing current output from said high-current pulse generator means.

6. The ignition system of claim 5, wherein said high-current pulse generator means further includes an error driven closed-loop feedback circuit for controlling amplitude of said high-current pulse in response to current demanded by said controller means and output current sensed by said current probe.

7. The ignition system of claim 6, wherein said error driven closed-loop feedback circuit comprises an analog-to-digital converter connected to said current probe for receiving and digitizing said current output from said high-current pulse generator means and generating an actual current data signal in response thereto, a subtracter connected to said analog-to-digital converter and said controller means for subtracting said current demanded from said actual current data signal and in response generating an error signal, a digital-to- analog converter for receiving and converting said error signal to analog form and in response generating said output current.

8. The ignition system of claim 5, 6 or 7, wherein said current probe is a Hall effect device.

9. The ignition system of claim 2, wherein said controller means receives said engine parameters in the form of one or more of fuel composition data, air density data, air temperature data, engine physical data, and RPM data.

10. The ignition system of claim l, wherein said high-voltage pulse generator means further comprises a high frequency oscillator for generating a sinusoidal output signal of predetermined frequency, a transformer with capacitors on primary and secondary circuits thereof for tuning said transformer to said predetermined frequency, said transformer receiving said sinusoidal output signal and in response resonating at said predetermined frequency and generating said high voltage high frequency burst of alternating current.

11. The ignition system of claim 10, wherein said predetermined frequency is approximately 500kHz and said high voltage is approximately 35KV.

12. The ignition system of claim 1, further including a high voltage blocker for preventing said high voltage high frequency burst of alternating current from entering said high-current pulse generator means.

13. The ignition system of claim 12 wherein said high voltage blocker is a double-octave filter.

14. The ignition system of claim 1, wherein said high-current pulse generator further includes an oscillator for generating a sinusoidal signal having predetermined amplitude and shape dictated by said controller means, and a resonating high-Q low loss current transformer for receiving said variable amplitude sinusoidal signal and in response generating said high- current pulse for application to said ignition plug.

15. The ignition system of claim 14, wherein said sinusoidal signal is in the range of from 50kHz to 150kHz.

16. The ignition system of claim 14, wherein said ignition plug further comprises a central electrode connected to one terminal of said current transformer, an insulator surrounding said central electrode, a metallic threaded jacket surrounding said insulator and having a plug electrode extending therefrom adjacent said central electrode, said jacket being connected to a remaining terminal of said current transformer, whereby said ignition plug and said high-current pulse generator form a fully balanced-to-ground AC circuit.

17. The ignition system of claim 16, wherein said ignition plug further includes means adjacent said central electrode and said plug electrode for generating a toroidal vortex of said plasma.

18. The ignition system of claim 17, wherein said ignition plug further includes means for focusing said toroidal vortex at a predetermined point, and means for storing a predetermined substance in the vicinity of said predetermined point for creating multi-point ignition sources within said toroidal vortex.

19. The ignition system of claim 16, wherein said plug electrode comprises a plurality of generally triangular points arranged circularly around said metallic threaded jacket.

20. The ignition system of claim 14, wherein said ignition plug further comprises a pair of D-shaped central electrodes having a gap therebetween and connected to opposite terminals of said current transformer, an insulator surrounding said central electrodes, and a threaded jacket surrounding said insulator, such that said ignition plug and said high- current pulse generator form a fully balanced-to-ground AC circuit.

21. The ignition system of claim 21, wherein said ignition plug further includes an organic catalyst disposed in said jacket adjacent said pair of D-shaped central electrodes.

22. The ignition system of claim 21 wherein said organic catalyst comprises a combination of carbon, hydrogen and oxygen and does not contain traces or metallic residues or salts of platinum, palladium,silver, gold, copper, rubidium, lead, arsenic, cobalt, mercury, cadmium or cesium.

23. The ignition system of claim 1, further comprising a plurality of additional ignition plugs connected to said high-voltage pulse generator and said high-current pulse generator via a distribution system, each of said additional ignition plugs being connected to said distribution system via a co-axial cable.

24. The ignition system of claim 10, wherein said high-voltage pulse generator means further comprises a full-bridge rectifier connected to said secondary circuit of said transformer for negative rectifying said high- voltage alternating current.