Internal combustion engine with gas feeding system
An engine is equipped with a gas feeding system, including main gas injectors each associated with an intake duct of a respective engine cylinder, a gas distribution manifold communicating with said main injectors, a gas tank, connected to the manifold, where pressurized gas is accumulated, a controlled pressure valve interposed between the tank and manifold, and a control unit for controlling the pressure valve to establish a gas pressure in the manifold. A spark plug of each cylinder is mounted within a support body that defines a combustion pre-chamber and a channel for auxiliary gas injection within the pre-chamber, communicating with a respective auxiliary gas injector. The auxiliary gas injectors are in communication with the manifold, downstream of the pressure valve. In the channel, a non-return valve and a restricted passage are provided in series, providing for passage of gas flow proportional to a volume of the pre-chamber.
1. A spark-ignition internal combustion engine having a system for feeding a gas, the engine comprising:
an engine block with a plurality of cylinders and a cylinder head defining a main combustion chamber associated with each cylinder,
an ignition spark plug associated with each cylinder,
a plurality of electromagnetically-controlled main gas injectors, each associated with an intake duct of a respective cylinder of the engine,
a gas distribution manifold, communicating with said main gas injectors,
a gas tank connected via a connection to the distribution manifold, where gas under pressure is accumulated,
wherein:
the spark plug of each cylinder is mounted within a support body that is mounted within a cavity of said cylinder head opening out in said main combustion chamber,
said support body defines a combustion pre-chamber having a first end facing electrodes of the respective spark plug and a second end communicating with the respective main combustion chamber through a plurality of orifices,
said support body also defines a channel for auxiliary gas injection into said combustion pre-chamber, said channel having a first end opening out in said combustion pre-chamber, adjacent to said spark plug, said channel being in communication with a respective auxiliary electromagnetically-controlled gas injector, mounted on the cylinder head in a remote position with respect to said combustion pre-chamber, and
in said auxiliary gas injection channel associated with each combustion pre-chamber there are arranged in series a non-return valve which enables gas to flow only towards the combustion pre-chamber, and a restricted passage,
wherein said engine further comprises:
an electronically-controlled pressure regulation valve, interposed in the connection between the gas tank and the distribution manifold, and
an electronic control unit configured to control opening and closing of each main gas injector, according to operating conditions of said gas feeding system, and according to operating conditions of the engine, for controlling said pressure regulation valve in order to establish a gas pressure in the gas distribution manifold, the gas pressure being determined according to the operating conditions of said gas feeding system and according to the operating conditions of the engine,
and wherein:
the auxiliary gas injectors associated with the combustion pre-chambers are all in communication with said distribution manifold, downstream of said electronically-controlled pressure regulation valve, with reference to flow of the gas coming from the gas tank,
said electronic control unit also being configured to control opening and closing of each of said auxiliary gas injectors, and
said restricted passage is defined by a hole of a bushing inserted within said channel for auxiliary gas injection defined within said support body, said hole having a diameter (D) such that a D/V ratio between said diameter and a volume (V) of the combustion pre-chamber is between 3×10 −4 and 6×10 −4 mm −2 , thereby providing for passage of a gas flow proportional to the volume of the combustion pre-chamber.
2. The engine according to claim 1 , wherein said support body comprises an upper portion and a lower portion, rigidly connected to each other to define the combustion pre-chamber, said upper portion of the support body having a cylindrical configuration and the cavity having a substantially cylindrical configuration, and said upper portion of the support body being received within the cavity formed in the cylinder head,
wherein an outer surface of said upper portion has a circumferential groove that defines a circumferential chamber with a surface of said cylindrical cavity, said circumferential chamber communicating with the respective auxiliary gas injector by a second channel formed in the cylinder head, and
wherein a second end of said auxiliary gas injection channel communicates with said circumferential chamber.
3. The engine according to claim 2 , wherein said auxiliary gas injection channel extends through the upper portion of the support body and has:
a lower channel portion, opening out in the combustion pre-chamber, in which the bushing is inserted defining the restricted passage, and
an upper channel portion opening out in said circumferential chamber, wherein which the non-return valve is inserted.
4. The engine according to claim 1 , wherein the volume of the combustion pre-chamber is less than 3% of a volume of the main combustion chamber of each cylinder.
5. The engine according to claim 1 , wherein the combustion pre-chamber has a main portion of elongated cylindrical shape, having an L/D ratio between its length (L) and its diameter (D) which is between 3 and 6.
6. The engine according to claim 5 , wherein the orifices for communication between the combustion pre-chamber and the main combustion chamber are inclined with respect to a main axis of said elongated main portion of the combustion pre-chamber by an angle from 50° to 70°.