To meet both a request to improve the thermal efficiency in the medium load operation of an engine and a request to suppress knocking in the high load and high rotation operation of the engine, the engine includes a main combustion chamber comprising a cylinder block, a cylinder head, and a piston; a pre-chamber having a plurality of injection holes that open into the main combustion chamber; and a spark plug that ignites an air-fuel mixture in the pre-chamber. A compression ratio of the main combustion chamber is not less than 14 and not more than 24. A first index, which is the product between a total cross-sectional area of the plurality of injection holes and the compression ratio, is not less than 0.1496 cm.sup.2 and not more than 0.8449 cm.sup.2.

There are provided systems and methods for the use of rich limit extenders, and in particular pre-chamber assemblies, for increasing the ability of a spark-ignition engine to operate under fuel-rich conditions. In embodiments the pre-chamber assemblies are combined with spark-ignition engines as a reformer in a gas-to-liquid system for converting a combustible fuel source into synthesis gas. Embodiments of the reformers having pre-chambers provide a synthesis gas product having a H.sub.2/CO ratio, with increased H.sub.2 concentrations.

To effectively suppress strong knock that occurs in the operating region of high load and high rotation in a specific engine having a pre-chamber in a combustion chamber, the engine includes a piston that defines a combustion chamber together with a cylinder block and a cylinder head. The combustion chamber includes a sub-chamber and a main chamber separated from the sub-chamber by a pre-chamber. The specific ratio obtained by dividing a volume of the sub-chamber by a stroke volume of a cylinder is greater than or equal to 0.00005 and less than or equal to 0.00045.

Fuel gas (G) is supplied via a pipe to a pre-combustion chamber of an internal combustion engine. The pre-combustion chamber is formed inside a chamber body which is received in a cavity of the engine body, while the pipe is received in a passageway of the engine body which communicates with the cavity. A seal which may be made from an elastomer comprises a wall defining an interior space opening through the wall at first, second and third openings. A first portion of the wall defining the first and second openings is arranged in the cavity so that the chamber body can be inserted through the openings into the interior space of the seal, while a second portion of the wall comprising the third opening is received in the passageway so that the pipe can be inserted into the interior space of the seal via the third opening. The pipe is sealed in fluid communication with the pre-combustion chamber via an inlet in the chamber body by sealing regions of the seal.

The invention relates to an engine having prechamber ignition, in particular a gas engine, that comprises a main combustion space in a cylinder of the engine for combusting an air-fuel mixture and a prechamber having an ignition device arranged therein and a fuel injector arranged therein, wherein the prechamber has at least one transfer port that fluidically connects the prechamber to the main combustion space. The engine is characterized in that the fuel injector arranged in the prechamber is the only fuel injector via which fuel can be introduced into the associated main combustion space.

There are provided systems and methods for using fuel rich partial oxidation to produce an end product from waste gases, such as flare gas. Lambda sensor modifications and other control parameters that provide closed-loop mixture control at extremely fuel-rich operating conditions utilizing feed-forward and feedback approaches, physics-based engine models, novel use of a lambda sensor (O.sub.2-based sensor), sensors with intermittent contact with the gas stream. In an embodiment the system and method use air-breathing engines having control systems, control parameters, sensors and input/output (I/O) for the fuel rich (ER of 1.2 and greater), partial oxidation of the flare gas to form syngas. In embodiments the syngas is further converted into an end product. In an embodiment the end product is methanol.

Aspects relate to zero-emission propulsion systems and generators using ammonia (NH.sub.3) as fuel for engines and power plants. While ammonia has poor flammability, mixing hydrogen with ammonia (NH.sub.3) may improve flammability and thus facilitate the ignition of an air/ammonia mixture in engines or power plants. Alternatively, hydrogen (H.sub.2) may be supplied in a separate fuel system as a pilot fuel for pilot ignition of an air/ammonia mixture. Hydrogen can also be used in air independent systems along with oxygen (O.sub.2) from an oxygen tank. In addition to hydrogen, other bio or fossil fuels can be used as pilot fuel for pilot ignition of an air/ammonia mixture. An advantage of using existing bio or fossil fuels for pilot ignition is that engines or power plants will have a pilot fuel system with sufficient capacity to maintain normal operations if ammonia is not available.

Systems and methods for starting and operating a direct injection engine are described. In one example, the air and fuel are injected into a pre-chamber of a cylinder of an engine while the engine is not rotating. The air and fuel are combusted in the pre-chamber to improve ignition of an air and fuel mixture in the cylinder.

Systems, devices, and methods described herein provide one or more radical chemicals generators (RCGs) and/or mini-chambers (M-Cs) that can be used to provide enhanced radical ignition (ERI) in an internal combustion engine. RCGs as described herein can include quenching systems (QSs) that can be configured to quench a flame of combustion products to produce a jet of partial combustion products containing radical species (RS). The jet of partial combustion products can be injected to a main combustion chamber (MCC) of an engine to induce ERI. ERI can proceed under leaner fuel conditions and lower temperatures compared to those needed for conventional thermally induced, fuel oxidation chain initiation reaction processes.

Optimized alcohol and plasma enhanced prechambers for engines powered by gasoline and other fuels are used to increase the range of prechamber operation and to reduce soot. The increased prechamber capability is employed to extend the limit of lean operation of the engines. It can also be used to extend the limit of heavy EGR operation and to enable higher RPM operation. The amount of alcohol used in the prechamber is preferably less than 2% of the fuel that is used in the engine cylinder. The alcohol for the prechamber can be entirely provided by onboard separation from a gasoline-alcohol fuel mixture.