An ignition circuit and a method of operating an igniter (preferably a traveling spark igniter) in an internal combustion engine, including a high pressure engine. A high voltage is applied to electrodes of the igniter, sufficient to cause breakdown to occur between the electrodes, resulting in a high current electrical discharge in the igniter, over a surface of an isolator between the electrodes, and formation of a plasma kernel in a fuel-air mixture adjacent said surface. Following breakdown, a sequence of one or more lower voltage and lower current pulses is applied to said electrodes, with a low simmer current being sustained through the plasma between pulses, preventing total plasma recombination and allowing the plasma kernel to move toward a free end of the electrodes with each pulse.

An ignition circuit and a method of operating an igniter (preferably a traveling spark igniter) in an internal combustion engine, including a high pressure engine. A high voltage is applied to electrodes of the igniter, sufficient to cause breakdown to occur between the electrodes, resulting in a high current electrical discharge in the igniter, over a surface of an isolator between the electrodes, and formation of a plasma kernel in a fuel-air mixture adjacent said surface. Following breakdown, a sequence of one or more lower voltage and lower current pulses is applied to said electrodes, with a low simmer current being sustained through the plasma between pulses, preventing total plasma recombination and allowing the plasma kernel to move toward a free end of the electrodes with each pulse.

An ignition device according to the present invention includes: an ignition plug, which includes a first electrode, a second electrode, and a dielectric body arranged between the electrodes; an AC power supply configured to generate an AC voltage to be applied between the electrodes; a thermal plasma detection portion configured to output a thermal plasma occurrence signal when thermal plasma has occurred between the electrodes; and an application time period determination portion configured to determine an application time period for the AC voltage during one cycle of the internal combustion engine in advance before the application, and when the thermal plasma occurrence signal is received while the AC voltage is being applied based on the application time period, change the application time period so as to shorten the application time period.

A corona igniter assembly which is designed to reduce the amount of air gaps between insulating components and thus reduce electrical fields concentrated in those air gaps and the associated unwanted corona discharge. The assembly includes a high voltage center electrode surrounded by a ceramic insulator and a high voltage insulator. A dielectric compliant insulator is disposed between the ceramic insulator and the high voltage insulator. A layer of metal is applied to at least one of the insulators, for example the ceramic insulator. A compliant collet formed of a partially resistive material covers a sharp edge of the layer of metal to reduce the electric field and smooth the electric field distribution at the sharp edge of the metal layer.

A corona igniter assembly which is designed to reduce the amount of air gaps between insulating components and thus reduce electrical fields concentrated in those air gaps and the associated unwanted corona discharge. The assembly includes a high voltage center electrode surrounded by a ceramic insulator and a high voltage insulator. A dielectric compliant insulator is disposed between the ceramic insulator and the high voltage insulator. A layer of metal is applied to at least one of the insulators, for example the ceramic insulator. A compliant collet formed of a partially resistive material covers a sharp edge of the layer of metal to reduce the electric field and smooth the electric field distribution at the sharp edge of the metal layer.

A quarter wave coaxial cavity resonator for producing corona discharge plasma from is presented. The quarter wave coaxial cavity resonator has a folded cavity made of opposing concentric cavity members that are nested together to form a continuous cavity ending in a aperture. A center conductor with a tip is positioned in the cavity. The folded cavity advantageously permits the coaxial cavity resonator to resonate at a lower operating frequency than an unfolded quarter wave coaxial cavity resonator of the same length. Embodiments of the quarter wave coaxial cavity resonator use narrower apertures to reduce radiative losses, and include center conductors that are reactive load elements, such as helical coils. When a radio frequency (RF) oscillation is produced in the quarter wave coaxial cavity resonator, corona discharge plasma is formed at the tip of the center conductor. The corona discharge plasma can be used to ignite combustible materials in combustion chambers of combustion engines.

A quarter wave coaxial cavity resonator for producing corona discharge plasma from is presented. The quarter wave coaxial cavity resonator has a folded cavity made of opposing concentric cavity members that are nested together to form a continuous cavity ending in a aperture. A center conductor with a tip is positioned in the cavity. The folded cavity advantageously permits the coaxial cavity resonator to resonate at a lower operating frequency than an unfolded quarter wave coaxial cavity resonator of the same length. Embodiments of the quarter wave coaxial cavity resonator use narrower apertures to reduce radiative losses, and include center conductors that are reactive load elements, such as helical coils. When a radio frequency (RF) oscillation is produced in the quarter wave coaxial cavity resonator, corona discharge plasma is formed at the tip of the center conductor. The corona discharge plasma can be used to ignite combustible materials in combustion chambers of combustion engines.

An ignition circuit and a method of operating an igniter (preferably a traveling spark igniter) in an internal combustion engine, including a high pressure engine. A high voltage is applied to electrodes of the igniter, sufficient to cause breakdown to occur between the electrodes, resulting in a high current electrical discharge in the igniter, over a surface of an isolator between the electrodes, and formation of a plasma kernel in a fuel-air mixture adjacent said surface. Following breakdown, a sequence of one or more lower voltage and lower current pulses is applied to said electrodes, with a low simmer current being sustained through the plasma between pulses, preventing total plasma recombination and allowing the plasma kernel to move toward a free end of the electrodes with each pulse.

An ignition circuit and a method of operating an igniter (preferably a traveling spark igniter) in an internal combustion engine, including a high pressure engine. A high voltage is applied to electrodes of the igniter, sufficient to cause breakdown to occur between the electrodes, resulting in a high current electrical discharge in the igniter, over a surface of an isolator between the electrodes, and formation of a plasma kernel in a fuel-air mixture adjacent said surface. Following breakdown, a sequence of one or more lower voltage and lower current pulses is applied to said electrodes, with a low simmer current being sustained through the plasma between pulses, preventing total plasma recombination and allowing the plasma kernel to move toward a free end of the electrodes with each pulse.

An ignition system and a method for a spark-ignition combustion engine having a high-frequency plasma-augmented ignition spark, the spark ignition of the fuel being realized by at least one spark plug associated with a combustion chamber of the combustion engine. The spark plug has a prechamber having at least one opening via which the prechamber communicates with the combustion chamber on the fuel side, so that the ignition spark in the prechamber, into which the high-frequency plasma can be injected, induces the plasma-augmented spark ignition of the fuel in the prechamber.