In certain embodiments, a unique method and pre-combustion chamber (PCC) structure may ensure very efficient flame propagation of lean fuel-air mixture in natural gas engines by reducing the amount of fuel admitted to the PCC. A PCC may include an enclosed volume of 1-3% of the main combustion chamber volume, with a spark plug and a fuel passage located opposite one or more PCC discharge nozzles to create a relatively richer fuel-air mixture with relatively lower turbulence in the spark plug region and a relatively leaner fuel-air mixture with relatively high turbulence in the nozzle region, which can be reliably and efficiently ignited, resulting in a high velocity flame jet/torch emerging from the prechamber into the main chamber. The PCC may be threaded with a 22 mm1.5 or -18 thread size, to allow the PCC to be screwed into a cylinder head in place of a spark plug.

A method of operating an internal combustion engine having pilot subchambers communicating with main combustion chambers, the internal combustion engine configured in use to deliver a main fuel injection of a maximum quantity of fuel to the main combustion chambers when the internal combustion engine is operated at maximum load. The method includes delivering a pilot fuel injection of at most 10% of the maximum quantity to the pilot subchambers, igniting the pilot fuel injection within the pilot subchambers, directing the ignited fuel from the pilot subchambers to the main combustion chambers, and delivering a main fuel injection of a main quantity of fuel to at least one of the main combustion chambers receiving the ignited fuel, with the main quantity being at most 10% of the maximum quantity.

A method of combusting fuel, e.g. heavy fuel, in a rotary engine, including injecting a main quantity of fuel directly into a combustion chamber to form a first fuel-air mixture having a first air-fuel equivalence ratio higher than 1, injecting a pilot quantity of fuel into a pilot subchamber to form a second fuel-air mixture having a second air-fuel equivalence ratio smaller than the first air-fuel equivalence ratio, igniting the second fuel-air mixture within the pilot subchamber, using the ignited second fuel-air mixture from the pilot subchamber to ignite the first fuel-air mixture, and injecting a supplemental quantity of fuel directly into the combustion chamber after igniting the first fuel-air mixture, upstream of an exhaust port of the rotary engine with respect to a direction of rotation of the rotor. A rotary engine with interburner fuel injector is also discussed.

In certain embodiments, a two-stage precombustion chamber may be used to reduce engine NOx levels, with fueled precombustion chambers, while maintaining comparable engine power output and thermal efficiency. One or more fuel admission points may be located in either the first prechamber stage or the second prechamber stage. A more efficient overall combustion characterized by low levels of NOx formation may be achieved by a two-stage precombustion chamber system while generating very high energy flame jets emerging from the second prechamber stage into the main combustion chamber. A first prechamber stage may be substantially smaller than a second prechamber stage. The volumes and aspect ratios of the two prechamber stages, along with the location of the electrodes within the first stage prechamber, the holes patterns, angles and the separate fueling, may be selected to create a distribution of fuel concentration that is substantially higher in the first stage prechamber compared to the second prechamber stage.

A gas engine includes: a main combustion chamber; and a precombustion chamber including an ignition plug disposed in a precombustion-chamber upper section and a throat formed in a precombustion-chamber lower section, the throat including a nozzle hole, configured such that mixed gas flows into the throat of the precombustion chamber via the nozzle hole from the main combustion chamber in a compression stroke. The nozzle hole has an opening edge portion on a throat side, the opening edge portion including a curved surface portion formed along a peripheral edge of the opening edge portion. The throat extends linearly along a center axis of the precombustion chamber. A ratio of a length of the throat to an inner diameter of the throat is not smaller than 1.6 and not greater than 2.6, and a value obtained by multiplying a ratio of the inner diameter of the throat to a radius of the curved surface portion by a ratio of the inner diameter of the throat to a precombustion chamber upper portion diameter is not smaller than 18.

In certain embodiments with large size prechambers and/or with prechambers that have large spark-gap electrode assemblies, a poor scavenge of the crevice volume may cause deterioration of the preignition margin, which then may limit the power rating of the engine, may cause the flow velocity field of the fuel-air mixture to be excessively uneven and may result in the deterioration of the misfire limit. One or more auxiliary scavenging ports may allow admission of fuel rich mixture to the crevice volume, thereby cooling the residual gases and preventing occurrence of preignition. More organized and powerful flow velocity fields may be obtained in the spark-gap electrode assembly region. This condition may result in a significant extension of the flammability limit and may significantly improve the combustion efficiency of the prechamber. Passive prechambers using the active scavenge concept may increase the engine power output and reduce the emission of pollutants from engine combustion.

A precombustion-chamber engine includes a cylinder, a cylinder head disposed on a top of the cylinder, and a piston reciprocably disposed within the cylinder. A main combustion chamber is defined between the piston and the cylinder head. The cylinder head includes a precombustion-chamber forming part which defines a precombustion chamber communicating with the main combustion chamber through a nozzle. The precombustion chamber includes a cylindrical first passage part extending upwardly from the nozzle, a second passage part extending upwardly from the first passage part and having an upwardly-increasing cross-sectional area, and a cylindrical space part which extends upwardly from the second passage part and in which a spark plug is disposed. Center O of a cross-section, orthogonal to straight line L, of the second passage part is eccentric with respect to straight line L composed of an axis of the first passage part and an extended line of the axis.

A method of operating an internal combustion engine having pilot subchambers communicating with main combustion chambers, the internal combustion engine configured in use to deliver a main fuel injection of a maximum quantity of fuel to the main combustion chambers when the internal combustion engine is operated at maximum load. The method includes delivering a pilot fuel injection of at most 10% of the maximum quantity to the pilot subchambers, igniting the pilot fuel injection within the pilot subchambers, directing the ignited fuel from the pilot subchambers to the main combustion chambers, and delivering a main fuel injection of a main quantity of fuel to at least one of the main combustion chambers receiving the ignited fuel, with the main quantity being at most 10% of the maximum quantity.

In certain embodiments with large size prechambers and/or with prechambers that have large spark-gap electrode assemblies, a poor scavenge of the crevice volume may cause deterioration of the preignition margin, which then may limit the power rating of the engine, may cause the flow velocity field of the fuel-air mixture to be excessively uneven and may result in the deterioration of the misfire limit. One or more auxiliary scavenging ports may allow admission of fuel rich mixture to the crevice volume, thereby cooling the residual gases and preventing occurrence of preignition. More organized and powerful flow velocity fields may be obtained in the spark-gap electrode assembly region. This condition may result in a significant extension of the flammability limit and may significantly improve the combustion efficiency of the prechamber. Passive prechambers using the active scavenge concept may increase the engine power output and reduce the emission of pollutants from engine combustion.

An engine is provided. In one embodiment, the engine includes a precombustion chamber having a body, a secondary combustion chamber disposed at least partially in the body, and a plurality of passages configured to place the precombustion chamber in fluid communication with a main combustion chamber.