An engine system is provided, which includes a main combustion chamber, a subchamber, an injector that injects fuel into the main combustion chamber, a main spark plug that ignites a mixture gas inside the main combustion chamber, a subspark plug that ignites the mixture gas inside the subchamber, an exhaust gas recirculation (EGR) device and a control device. In a specific range where EGR is performed, the ignition devices are controlled so that a subignition timing is retarded from a main ignition timing, and an ignition phase difference that is a retard amount of the subignition timing from the main ignition timing becomes larger under a high EGR condition than a low EGR condition, the EGR conditions being conditions in the specific range where engine speeds are the same and EGR rates are different, and the high EGR condition being larger in the EGR rate than the low EGR condition.

A method of operating an engine includes igniting a combustible mixture in a combustion chamber of the engine, which produces exhaust gases. The exhaust gases are ejected into an exhaust manifold of the engine to create a primary exhaust stream. A portion of the exhaust gases is separated from the primary exhaust stream to create a secondary exhaust stream. Air and fuel are then mixed with the secondary exhaust stream to form a reformer feed mixture. The reformer feed mixture is reacted in a catalytic reformer to create a reformate exhaust stream, which is then mixed with an intake air stream to create a mixed air stream. The mixed air stream is the fed to the combustion chamber of the engine as the combustible mixture.

A method includes operating a spark ignition engine and flowing low pressure exhaust gas recirculation (EGR) from an exhaust to an inlet of the spark ignition engine. The method includes interpreting a parameter affecting an operation of the spark ignition engine, and determining a knock index value in response to the parameter. The method further includes reducing a likelihood of engine knock in response to the knock index value exceeding a knock threshold value.

A method includes operating a spark ignition engine and flowing low pressure exhaust gas recirculation (EGR) from an exhaust to an inlet of the spark ignition engine. The method includes interpreting a parameter affecting an operation of the spark ignition engine, and determining a knock index value in response to the parameter. The method further includes reducing a likelihood of engine knock in response to the knock index value exceeding a knock threshold value.

An engine system includes an engine configured to combust liquid natural gas and generate an exhaust gas comprising methane; a catalytic reactor coupled downstream of the engine and configured to convert methane into a product through one or more of oxidative coupling of methane (OCM) reaction and steam methane reforming (SMR) reaction; and a recirculation loop configured to recirculate at least a part of the product back to the engine.

An engine is equipped with an engine body, a turbocharger, an exhaust gas purifier, an exhaust communication pipe. The turbocharger is connected to the engine body. The exhaust gas purifier purifies exhaust gas discharged from the turbocharger. The exhaust communication pipe connects the turbocharger with the exhaust gas purifier. The exhaust communication pipe includes: a first connection member that is connected to the turbocharger, and a second connection member that connects the first connection member with the exhaust gas purifier. A downstream end portion of the first connection member has an inner peripheral face having a cross-section of a circular shape. An upstream end portion of the first connection member has an inner peripheral face having a cross-section of an abnormal-shape that is different from the inner peripheral face of the downstream end portion.

An embodiment apparatus for reducing fouling of an exhaust gas recirculation (EGR) cooler includes an exhaust gas transfer part configured to connect a diesel oxidation catalyst (DOC) of an exhaust gas post-treatment system extending from an engine through an exhaust line to an EGR cooler installed in an EGR line and configured to recirculate exhaust gas discharged from an exhaust manifold to an intake manifold, a valve installed in the exhaust gas transfer part, and a controller configured to selectively open the valve as the exhaust gas post-treatment system enters a predetermined diesel particulate filter (DPF) regeneration condition and allow exhaust gas discharged from the DOC to be supplied to the EGR cooler through the exhaust gas transfer part.

A system, a use of such a system and a multi system for cleaning exhaust gas from a combustion engine. The system comprises a first exhaust gas scrubber to communicate with a scrubber water circulation tank. A first outlet of the first exhaust gas scrubber is connectable to a first inlet of the scrubber water circulation tank, and a first inlet of the first exhaust gas scrubber is connectable to a first outlet of the scrubber water circulation tank, to enable circulation of scrubber water between the scrubber water circulation tank and the first exhaust gas scrubber. An air supply device feeds air into the first exhaust gas scrubber to aerate the scrubber water during its passage through the first exhaust gas scrubber. Accordingly, a second inlet of the first exhaust gas scrubber is arranged to be connected to an outlet of the air supply device.

A system, a use of such a system and a multi system for cleaning exhaust gas from a combustion engine. The system comprises a first exhaust gas scrubber to communicate with a scrubber water circulation tank. A first outlet of the first exhaust gas scrubber is connectable to a first inlet of the scrubber water circulation tank, and a first inlet of the first exhaust gas scrubber is connectable to a first outlet of the scrubber water circulation tank, to enable circulation of scrubber water between the scrubber water circulation tank and the first exhaust gas scrubber. An air supply device feeds air into the first exhaust gas scrubber to aerate the scrubber water during its passage through the first exhaust gas scrubber. Accordingly, a second inlet of the first exhaust gas scrubber is arranged to be connected to an outlet of the air supply device.

A three-way catalyst and an NO.sub.x adsorption catalyst are disposed in an engine exhaust passage. In a predetermined low-load engine operation area, combustion in a combustion chamber is carried out at a lean base air-fuel ratio and an air-fuel ratio in the combustion chamber is changed to a rich range at the time of discharging NO.sub.x from the NO.sub.x adsorption catalyst. In a predetermined high-load engine operation area, the air-fuel ratio in the combustion chamber is controlled to a theoretical air-fuel ratio in a feedback manner. In a predetermined middle-load engine operation area, the combustion in the combustion chamber is carried out at the base air-fuel ratio lower than the base air-fuel ratio in the low-load engine operation area and the air-fuel ratio in the combustion chamber is changed to the rich range with a period shorter than a rich period of the air-fuel ratio for discharging NO.sub.x in the low-load engine operation area.