Air/fuel mixture is received from a combustion chamber of the internal combustion engine into an enclosure about a flame kernel initiation gap between a first ignition body and a second ignition body. Air/fuel mixture received into the enclosure is directed into a flame kernel initiation gap. The mixture is then ignited in the flame kernel initiation gap.

Air/fuel mixture is received from a combustion chamber of the internal combustion engine into an enclosure about a flame kernel initiation gap between a first ignition body and a second ignition body. Air/fuel mixture received into the enclosure is directed into a flame kernel initiation gap. The mixture is then ignited in the flame kernel initiation gap.

An engine system includes an engine, a main combustion chamber formed by a cylinder head and a piston, an auxiliary chamber formed with a communicating hole communicating with the main combustion chamber, an injector configured to inject fuel into the main combustion chamber, an ignition plug provided to the auxiliary chamber and configured to ignite a mixture gas inside the auxiliary chamber, an accelerator opening sensor, and a control device. The control device controls the injector so that an air-fuel ratio of the mixture gas inside the auxiliary chamber becomes a first air-fuel ratio when an engine load range is a first range, and the air-fuel ratio of the mixture gas inside the auxiliary chamber becomes a second air-fuel ratio leaner than the first air-fuel ratio when the engine load range is a second range where the engine load is higher than in the first range.

A spark plug capable of generating a sufficient volume of jet with an increased range is provided. The spark plug includes a metal shell having a tubular shape; a center electrode retained in the metal shell in an insulated manner; a ground electrode that is electrically connected to the metal shell and that defines a spark gap between the center electrode and an end portion of the ground electrode; and a cap portion that covers the center electrode and the end portion of the ground electrode from the front in a region in front of the metal shell and in which a through hole is formed. The cap portion includes a plurality of projections on an inner surface of the through hole. The projections extend in an extending direction in which the through hole extends.

A spark plug capable of generating a sufficient volume of jet with an increased range is provided. The spark plug includes a metal shell having a tubular shape; a center electrode retained in the metal shell in an insulated manner; a ground electrode that is electrically connected to the metal shell and that defines a spark gap between the center electrode and an end portion of the ground electrode; and a cap portion that covers the center electrode and the end portion of the ground electrode from the front in a region in front of the metal shell and in which a through hole is formed. The cap portion includes a plurality of projections on an inner surface of the through hole. The projections extend in an extending direction in which the through hole extends.

Methods and systems are provided for operating an engine with a series gap igniter. In one example, a system may include a series gap igniter coupled to a cylinder head of a cylinder, the series gap igniter including a first spark gap in an internal volume of the series gap igniter and a second spark gap of the series gap igniter external to the internal volume of the series gap igniter and within a clearance volume of the cylinder. In this way, a cylinder with a series gap igniter may be operated to efficiently and reliably initiate combustion over a range of engine operating conditions.

A prechamber spark plug. The prechamber spark plug includes: a housing, and a cap which has at least one pass-through opening, the cap being situated at a combustion chamber-side end of the housing. The cap and the housing form a prechamber. An outer cap surface area of the cap, which faces away from the prechamber, has at least one predefined ratio to respectively one further geometric feature of the cap.

A prechamber spark plug. The prechamber spark plug includes: a housing, and a cap which has at least one pass-through opening, the cap being situated at a combustion chamber-side end of the housing. The cap and the housing form a prechamber. An outer cap surface area of the cap, which faces away from the prechamber, has at least one predefined ratio to respectively one further geometric feature of the cap.

A method of providing a passive ignition pre-chamber for an internal combustion engine. The pre-chamber is typically implemented as a cap on the electrode end of a spark plug and encloses a pre-chamber volume in which fuel is mixed with air to form a consistently ignitable mixture. The pre-chamber is passive in the sense that gas exchange with the engine's main combustion chamber is realized by local flow fields near nozzles into the main chamber and by pressure differences between the pre-chamber and the main chamber. The nozzles are sized such that at least one of the nozzles has a larger diameter than the remaining nozzles, as optimized using flow field and pre-chamber turbulence analysis.

A spark plug for an internal combustion engine includes a cylindrical insulator, a center electrode, a cylindrical housing, and a plug cover. On a tip side of the insulator, an auxiliary combustion chamber is formed which is surrounded by at least the plug cover. The plug cover is provided with nozzle holes that communicate between the auxiliary combustion chamber and the outside of the auxiliary combustion chamber. A central axis of the nozzle hole is inclined with respect to a plug radial direction when viewed in a plug axial direction. At least a part around an outer opening of the nozzle hole is provided with a concave portion that is adjacent to the outer opening. The concave portion is recessed from the outside to the inside of the plug cover.