EP4617477A1

EP4617477A1 - Internal combustion engine system

Info

Publication number: EP4617477A1
Application number: EP24162922.9A
Authority: EP
Inventors: Fredrik Larsson; Fredrik Rahm
Original assignee: Volvo Truck Corp
Current assignee: Volvo Truck Corp
Priority date: 2024-03-12
Filing date: 2024-03-12
Publication date: 2025-09-17

Abstract

The present disclosure relates to an internal combustion engine (ICE) system (10) for a vehicle (1), the ICE system comprising: a two-stroke ICE (20) operable on a fuel (50), the ICE having at least one cylinder (30) with a cylinder wall (30a) and further a reciprocating piston (31) moveable in an axial direction (A) within the cylinder between a bottom dead center (BDC) and a top dead center (TDC), the at least one cylinder at least partly defining a combustion chamber with a top end (33) of the piston, wherein the at least one cylinder comprises at least one intake port (35) arranged at a top end (36) of the at least one cylinder, and further configured to be in fluid communication with the combustion chamber, an exhaust port (38) arranged axially distal from the top end of the at least one cylinder, allowing the at least one intake port and the exhaust port to be fluidly separated by the piston, and wherein the at least one cylinder further comprises an evacuation port (95) arranged at the top end of the at least one cylinder, the evacuation port being configured to be in fluid communication with the combustion chamber, and a controllable evacuation valve (96) disposed in the evacuation port and configured to provide an engine braking by controlling the flow of fluid medium through the evacuation port.

Description

TECHNICAL FIELD

The disclosure relates generally to an internal combustion engine system for a vehicle. The disclosure can be applied to heavy-duty vehicles, such as trucks, buses, and construction equipment, among other vehicle types. Although the disclosure may be described with respect to a truck, the disclosure is not restricted to any particular vehicle. The internal combustion engine system may e.g. be applicable for other types of vehicles propelled by means of an internal combustion engine such as cars and other lightweight and light-duty vehicles etc. The internal combustion engine system may likewise be applicable in marine vessels and the like. Further, the internal combustion engine of the internal combustion engine system may typically be a two-stroke internal combustion engine operable on a hydrogen-based fuel.

BACKGROUND

To mitigate negative climate impacts, there is growing interest in reducing fossil fuel consumption. For instance, criteria such as exhaust gas reduction, enhanced engine efficiency (i.e., reduced fuel consumption), and decreased engine noise levels have become pivotal in the design and selection of suitable internal combustion engine (ICE) systems and component. Furthermore, in the field of heavy-duty vehicles, including trucks, numerous environmental regulations impose specific requirements on vehicles, such as limits on the maximum allowable exhaust gas emissions.
One possibility for reducing emissions is to use hydrogen gas, produced in a fossil-free way, as fuel in internal combustion engines instead of using e.g. fossil-based diesel. The vast number of existing conventional diesel engines cannot operate properly when simply switched to hydrogen fuel from diesel; these engines require adaptation to be capable of utilizing hydrogen fuel. However, to make such adaptation of existing diesel engines economically feasible, it is necessary that the adaptations are not too complex and costly.
Incorporating hydrogen as a fuel in internal combustion engines presents several challenges, particularly for heavy-duty vehicles, which existing engine architectures may not adequately address. Consequently, there remains a need for an improved internal combustion engine system for vehicles that can efficiently utilize hydrogen fuel.

SUMMARY

According to a first aspect of the disclosure, there is provided an internal combustion engine (ICE) system for a vehicle. The ICE system comprises a two-stroke ICE operable on a fuel. The ICE has at least one cylinder with a cylinder wall and further a reciprocating piston moveable in an axial direction A within the cylinder between a bottom dead center (BDC) and a top dead center (TDC), the at least one cylinder at least partly defining a combustion chamber with a top end of the piston, wherein the at least one cylinder comprises at least one intake port arranged at a top end of the at least one cylinder, and further configured to be in fluid communication with the combustion chamber, an exhaust port arranged axially distal from the top end of the at least one cylinder, allowing the at least one intake port and the exhaust port to be fluidly separated by the piston, and wherein the at least one cylinder further comprises an evacuation port arranged at the top end of the at least one cylinder, the evacuation port being configured to be in fluid communication with the combustion chamber, and a controllable evacuation valve disposed in the evacuation port and configured to provide an engine braking by controlling the flow of fluid medium through the evacuation port.
The first aspect of the disclosure may seek to provide an improved engine braking operation of a two-stroke ICE system. In the context of the present disclosure, the term "engine braking" typically refers to an operation of the engine when the retarding forces within the engine are used to slow a vehicle down. When an engine braking mode is activated, the controllable evacuation valve is controlled to an open state, or at least a partly open state, thereby releasing compressed fluid medium trapped in the cylinder via the evacuation port, and slowing down the vehicle. In particular, the disclosure may seek to provide an improved engine braking operation of a two-stroke ICE system configured to provide propulsion power through combustion of a fuel such as a hydrogen-based fuel. A technical benefit may include a more efficient engine braking operation for a two-stroke ICE engine, enabling better vehicle control. The term "fluid medium" may refer to a compressed gas fluid medium, compressed air, exhaust gas, or a mix thereof.
By arranging the intake and exhaust ports of the cylinders at different positions, the corresponding piston creates a blocking effect between these ports when it reaches its top dead center. Such configuration ensures that the hotter parts of the cylinder, such as the exhaust port and the cylinder wall or liner, are completely isolated from the combustible gas, typically an air/fuel mixture.
As such, the proposed ICE system enables a length-scavenging system that separates the hot exhaust end of the cylinder from the cold intake end where the combustibles are present. Therefore, the knock risk may be drastically reduced with the proposed ICE system. To this end, the proposed ICE system provides for suppressing the tendency for knock and/or self-ignition of the fuel, such as a gaseous fuel, e.g. hydrogen-based fuel.
In addition, the proposed two-stroke ICE, favorably operable on hydrogen, or any other gaseous fuel, provides for increasing the BMEP potential due to twice the firing frequency. In particular, the two-stroke cycle enable the ICE to operate at a higher lambda with a maintained power density, as compared to four stroke ICEs.
A "two-stroke operation" or "two-stroke mode" refers to a cycle of the internal combustion engine, in which the piston moves two strokes (up and down movements) between the TDC and the BDC during only one crank shaft revolution so as to complete a full work cycle. In general, the operation of the internal combustion engine when operated in a general two-stroke operation corresponds to a repetitive engine operation every crank shaft revolution.
The fuel may be a gaseous fuel, a liquid fuel or a combination thereof, e.g. a dual fuel having a first fuel and a second fuel.
By the provision of arranging the exhaust port axially distal from the top end of the at least one cylinder, allowing the at least one intake port and the exhaust port to be fluidly separated by the piston, the at least one intake port and the exhaust port are located at different positions and fluidly separated by the piston top end when the piston is in the upper part of the cylinder. In particular, the at least one intake port and the exhaust port are located at different positions and fluidly separated by the piston top end when the piston is in its top dead center. As such, the fluid communication between the combustion chamber and the exhaust port is controlled by a position of the piston, typically corresponding to an axial position of the piston along the axial direction.
In some examples, including in at least one preferred example, optionally the controllable evacuation valve may be controllable in cooperation with the movement of the piston such that the controllable evacuation valve permits evacuation of fluid medium from the combustion chamber via the evacuation port during a compression stroke. A technical benefit may include enhanced timing precision of engine braking, contributing to improved fuel efficiency and reduced emissions.
In some examples, including in at least one preferred example, optionally the controllable evacuation valve may be controllable in cooperation with the movement of the piston such that the controllable evacuation valve skips evacuation of fluid medium from the combustion chamber via the evacuation port for a given crankshaft revolution. A technical benefit may include the ability to dynamically adjust engine braking intensity, allowing for smoother deceleration and enhanced engine performance under varying load conditions.
In some examples, including in at least one preferred example, optionally the controllable evacuation valve may be configured to be controllable by an actuator of a camshaft-driven valve actuation system. A technical benefit may include improved reliability and durability of the engine braking mechanism by a mechanical camshaft system.
In some examples, including in at least one preferred example, optionally the controllable evacuation valve may be configured to be controllable by an actuator of a variable valve actuation system. A technical benefit may include enhanced flexibility in engine braking control, enabling more precise management of vehicle deceleration.
In some examples, including in at least one preferred example, optionally the controllable evacuation valve may be controllable in response to an engine braking command from a control system. A technical benefit may include providing an enhanced integration with more advanced driver assistance systems (ADAS), allowing for automated control of engine braking in response to driving conditions and enhancing vehicle safety.
In some examples, including in at least one preferred example, optionally the evacuation port may be arranged in fluid communication with a fluid conduit arranged to route the fluid medium to a position downstream of a turbine of a turbocharger system. A technical benefit may include the potential for energy recovery and efficiency improvement by utilizing the evacuated fluid medium to assist in turbocharger operation.
In some examples, including in at least one preferred example, optionally the evacuation port may be arranged in fluid communication with a fluid conduit arranged to route the fluid medium to a position upstream of the turbine of the turbocharger system. A technical benefit may include the potential for energy recovery and efficiency improvement by utilizing the evacuated fluid medium to assist in turbocharger operation. This may also typically contribute to higher boost during engine braking, i.e., more mass is trapped in the cylinder, which provides for higher compression and brake power.
In some examples, including in at least one preferred example, optionally the ICE system may further comprise a controllable exhaust brake valve disposed in an exhaust duct downstream the exhaust port, the controllable exhaust brake valve being configured to restrict the flow of exhaust gases in the exhaust conduct. A technical benefit may include increased engine braking power and efficiency, particularly beneficial for heavy-duty vehicles in downhill scenarios. This may also contribute to higher boost during engine braking, i.e., more mass is trapped in the cylinder, which provides for higher compression and brake power. This can be provided in several different manners. For example, in an example where the controllable exhaust brake valve is also in fluid communication with the evacuation port, the controllable exhaust brake valve is configured to restrict the flow of fluid medium exiting the evacuation port, thereby creating back pressure that acts against the piston movement in the cylinder.
In addition, or alternatively, the controllable exhaust brake valve may be configured to restrict the flow of exhaust gases exiting the exhaust port, thereby creating back pressure that increase the pressure in cylinder and increasing the trapped mass. In this example, it should be noted that an air charging system may typically need to compensate with boost pressure accordingly to maintain the scavenging flow, which is at least partly due to that a two-stroke ICE is typically open during scavenging. The boost pressure compensation can typically be provided by a positive displacement device and/or a turbocharger that is driven independently, or partly by the exhaust gases. Accordingly, in one example, the ICE system is operable to control the boosting level by mechanical or electrical boosting (using e.g. a positive displacement device and/or a turbocharger) in combination with the controllable exhaust brake valve in the exhaust duct. By controlling the exhaust flow and compensating with additional boost pressure, the power output and fuel efficiency can be enhanced while managing the challenges presented by the scavenging process in two-stroke ICE systems.
In some examples, including in at least one preferred example, optionally the ICE system may be a spark-ignition ICE system, and the at least one cylinder having an ignition source arranged in the combustion chamber. The ignition source may be any one of a spark plug and a glow plug.
In some examples, including in at least one preferred example, optionally the ICE system may comprise a fuel injector arrangement for injecting fuel, the fuel injector arrangement being arranged in the combustion chamber. A technical benefit may include enhanced fuel delivery for improved combustion efficiency.
In some examples, including in at least one preferred example, optionally the ICE system may comprise a fuel injector arrangement for injecting fuel, the fuel injector arrangement being arranged upstream the at least one intake port to provide a port fuel injection arrangement. A technical benefit may include enhanced fuel delivery for improved combustion efficiency. The use of a port injection allows for providing a homogenous mixture which enables an improved knock and auto-ignition control and also contributes to reduce the emissions.
In some examples, including in at least one preferred example, optionally the flow of intake gas through the at least one intake port may be controllable by a controllable intake valve. A technical benefit may include the ability to precisely control the air-fuel mixture, further enhancing engine efficiency and performance.
In some examples, including in at least one preferred example, optionally the at least one cylinder may be a first cylinder and the piston may be a first piston, and the ICE further having a second cylinder forming a pair of cylinders with the first cylinder, the second cylinder accommodating a corresponding reciprocating second piston operable between a bottom dead center and a top dead center, and further at least partly defining a second combustion chamber with a top end of the second piston, wherein the second cylinder further comprises a corresponding ignition source arranged in the second combustion chamber, at least one corresponding intake port arranged at a top end of the second cylinder and in fluid communication with the second combustion chamber, and further a corresponding exhaust port arranged axially distal from the top end of the second cylinder, allowing the at least one corresponding intake port and the corresponding exhaust port to be fluidly separated by the second piston.
In some examples, including in at least one preferred example, optionally the first and second cylinders may be separated from each other with a crank angle of 180 degrees. By having the pair of first and second cylinders arranged separated from each other with a crank angle of 180 degrees, the two cylinders can provide a 180 degrees cycle separation irrespectively of the ICE and cylinder arrangement/configuration. In some examples, including in at least one preferred example, optionally the pair of first and second cylinders may be arranged separated from each other with a crank angle of 180 degrees, so as to provide a 180 degrees combustion phasing separation.
In some examples, including in at least one preferred example, optionally the ICE system may further comprise an air intake duct having a positive displacement device configured to receive and feed intake air to the pair of cylinders, the positive displacement device further being arranged in the air intake duct to separate an upstream intake tract from a downstream plenum of the air intake duct, the downstream plenum being in fluid communication with each one of the first and second cylinders of the pair of cylinders. A technical benefit may include improved air management and distribution, leading to more efficient combustion and enhanced engine performance. By the arrangement of the positive displacement device in the air intake duct, the displacement device is arranged to eliminate, or at least reduce, the risk of having pressure pulses transferred backwards from the combustion chambers to the upstream intake tract of the air intake duct. As such, the intake ports are mechanically isolated from the intake tract. The positive displacement device is thus arranged to seal the cylinders and the downstream intake plenum from the upstream intake tract of the air intake duct (intake manifold) in case of backfire. Also, by the arrangement and configuration of the displacement device in the air intake duct, the displacement device can still provide an even flow by the alternating feed to the cylinder pair.
To this end, the ICE system may thus provide separate intake plenum for each pair of cylinders with a 180 degrees combustion phasing separation, where the intake duct has a close coupled positive displacement device for each pair of cylinders. Such ICE system may contribute to reducing time-to-ignition with decreased risk of having backfiring into the induction system of the ICE system.
It should be noted that the proposed ICE system may not be restricted to a system with one single pair of cylinders, but can also be implemented in four cylinders, six cylinders etc. Hence, the proposed ICE system may have a minimum of two cylinders, but multiples of two cylinders may be possible.
In some examples, including in at least one preferred example, optionally the controllable intake valve of the first cylinder may be controllable in correlation with the movement of the first piston and the controllable intake valve of the second cylinder is controllable in correlation with the movement of the second piston such that fluid communication between the respective combustion chambers and the downstream plenum being selectively opened and closed during a crank shaft revolution of the ICE. A technical benefit may include synchronized air intake with piston movement, improving air utilization and enhancing engine efficiency.
In some examples, including in at least one preferred example, optionally the ICE system may be a hydrogen ICE system configured to operate on a gaseous fuel containing a hydrogen-based gaseous fuel. A technical benefit may include reduced environmental impact due to lower CO2 emissions compared to traditional hydrocarbon fuels, aligning with global sustainability goals. Hydrogen-based fuel may typically have a high auto-ignition temperature, however, low ignition energy may only be needed if a spark (or glowing surface or particle) is present. The low ignition energy may, however, pose some challenges on the ICE, e.g. it may be difficult to use a cylinder head where the hot exhaust ports/valves are located in the same combustion chamber as the intake ports/valves or in the vicinity of the compressed air/ fuel mixture prior to ignition. A technical benefit of the proposed ICE system for use with a hydrogen-based fuel may include a more reliable and robust hydrogen ICE system.
The ICE system may be beneficial for all force scavenged two strokes ICE systems, including, but not limited to compression ignited fuel engines, for example H2 ICE systems with diesel pilot injection in a two-stroke mode. In some examples, including in at least one preferred example, optionally the fuel may be a gaseous fuel. One example of a gaseous fuel is a hydrogen-based fuel. In some examples, including in at least one preferred example, optionally the fuel is a liquid fuel. One example of a liquid fuel is an NH3-based fuel.
In some examples, including in at least one preferred example, optionally the plenum may comprise an air inlet configured to be in fluid communication with the positive displacement device and a plurality of outlets configured to be in fluid communication with the intake ports of the first and second cylinders.
In some examples, including in at least one preferred example, optionally the ICE system may comprise a common crankcase housing for the pair of cylinders, or, the ICE system may comprise multiple set of pair of cylinders and the ICE system comprises a common crankcase housing for all cylinders of the ICE.
In some examples, including in at least one preferred example, optionally each one of the controllable intake valve and the corresponding controllable intake valve may be arranged to open and close a fluid passage of the respective intake port, thus controlling the flow of fluid to the respective combustion chamber.
In some examples, including in at least one preferred example, optionally the ICE system may comprise a fuel injector arrangement arranged in the downstream plenum of the air intake duct so as to provide a fuel injection upstream the intake ports of the first and second cylinders. A technical benefit may include an improved injection of fuel into the combustion chamber(s) of the ICE. Hereby, the ICE system is configured to provide port injection of the gaseous fuel or the liquid fuel.
In some examples, including in at least one preferred example, optionally the fuel injector arrangement may be controllable to inject fuel to the intake port and the corresponding intake port such that pressure pulses are generated in the downstream plenum and subsequently travel into the corresponding combustion chambers. A technical benefit may include an improved scavenging effect. As such, the ICE system is configured to provide a scavenging effect by the injection timing in the intake port(s). The fuel injector arrangement may generally be controllable in response to a predetermined fuel injection event.
In some examples, including in at least one preferred example, optionally the fuel injector arrangement may be controllable to provide a sequential injection of fuel to the first and second cylinders so as to allow for active cylinder scavenging during a latter part of a corresponding intake stroke of a corresponding cylinder of the first and second cylinders.
In some examples, including in at least one preferred example, optionally the controllable intake valve of the first cylinder may be controllable in correlation with the movement of the first piston and the controllable intake valve of the second cylinder may be controllable in correlation with the movement of the second piston such that fluid communication between the respective combustion chambers and the plenum being selectively open and closed during a crank shaft revolution of the ICE. A technical benefit may include to further reduce the risk of backfire.
In some examples, including in at least one preferred example, optionally the plenum may comprise an air inlet in fluid communication with the positive displacement device and a plurality of outlets configured to be in fluid communication with the intake ports of the first and second cylinders. A technical benefit may include an improved air supply system for supplying air to the cylinders. By way of example, the plenum is a Siamese-shaped design.
In some examples, including in at least one preferred example, optionally the controllable intake valves may be configured to provide variable valve actuation. A technical benefit may include an improved control of the air supply system for supplying air to the cylinders during operation of the ICE system. Variable valve actuation may also allow for tuning the phasing (valve timing) for a more optimum pulse capture and efficiency in synchronization with the fuel injection and the corresponding pulse in the plenum.
In some examples, including in at least one preferred example, optionally the positive displacement device may be a variable positive displacement device configured to be operated in a variable manner. A technical benefit may include an improved control of the flow and/or pressure of air to the cylinders during operation of the ICE system. Moreover, a variable driven positive displacement device allows for a higher flexibility of the air intake system of the ICE system and also an improved function of the ICE system on a general level.
In some examples, including in at least one preferred example, optionally the ICE system may further comprise additional pairs of cylinders with corresponding air intakes duct and positive displacement devices. In some examples, including in at least one preferred example, optionally the exhaust ports may be arranged in fluid communication with an exhaust duct arranged to transport exhaust gas away from the cylinders.
According to a second aspect of the disclosure, there is provided a vehicle comprising an internal combustion engine system according to the first aspect and/or according to any one of the examples of the first aspect. A technical benefit may include the integration of the ICE system into vehicles, offering improved efficiency, performance, and environmental benefits.
The disclosed aspects, examples (including any preferred examples), and/or accompanying claims may be suitably combined with each other as would be apparent to anyone of ordinary skill in the art. Additional features and advantages are disclosed in the following description, claims, and drawings, and in part will be readily apparent therefrom to those skilled in the art or recognized by practicing the disclosure as described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples are described in more detail below with reference to the appended drawings.

Fig. 1 is an exemplary embodiment of the present disclosure, comprising a side view of a vehicle, in the form of a truck, according to an example.
Fig. 2 shows an internal combustion engine system, according to an example.
Fig. 3 shows an internal combustion engine system, according to an example.
Fig. 4 shows an internal combustion engine system, according to an example.

DETAILED DESCRIPTION

The detailed description set forth below provides information and examples of the disclosed technology with sufficient detail to enable those skilled in the art to practice the disclosure.
In conventional internal combustion engine systems comprising an internal combustion engine (ICE), engine braking is typically achieved through mechanical friction and the compression of air within the cylinders when the throttle is closed and fuel injection is ceased. While the compression of air contributes to the braking effect, a significant portion of the energy involved in compressing the air is recuperated as the piston descends and the compressed air expands. This natural cycle may limit the efficiency of engine braking since not all the energy used in compressing the air is utilized for braking purposes.
The disclosure may seek to provide an improved engine braking operation of a two-stroke ICE system. More specifically, the disclosure may seek to maximize, or at least increase, the braking energy derived from the air compression phase in ICEs. By integrating one or more dedicated controllable evacuation valves configured to permit evacuation of fluid medium from the combustion chamber, it becomes possible to provide enhanced engine braking efficiency for two-stroke ICE systems. By way of example, by evacuating compressed air through the evacuation port, while using the inlet and exhaust ports for their intended purposes during the two-stroke engine cycle, it can be ensured that the energy expended in compressing the air is effectively utilized for braking.
For heavy-duty vehicles, especially those operating in challenging terrains, the enhanced engine braking may also provide drivers with better control over vehicle speed during descents, improving safety and handling. Hence, a technical benefit may include a more efficient engine braking operation for a two-stroke ICE engine, enabling better vehicle control.
The proposed two-stroke ICE system has a higher potential for engine braking power compared to a four-stroke ICE system because it completes a power cycle every revolution, meaning each piston stroke can act as a braking stroke. It should also be noted that conventional engine braking methods used in four-stroke ICE system are not suitable in the proposed two-stroke ICE system. This is due to the design differences where the intake port is located at the top of the cylinder and the exhaust port at the middle or bottom of the cylinder (i.e., the exhaust port is axially distanced from the intake port). Traditional engine braking rather relies on exhaust valves positioned at the top of the cylinder.
In the context of the present disclosure, the term "engine braking" typically refers to an operation of the engine when the retarding forces within the engine are used to slow a vehicle down. When an engine braking mode is activated, the controllable evacuation valve is controlled to an open state, or at least a partly open state, thereby releasing compressed fluid medium trapped in the cylinder via the evacuation port, and slowing down the vehicle. In particular, the disclosure may seek to provide an improved engine braking operation of a two-stroke ICE system configured to provide propulsion power through combustion of a fuel such as a hydrogen-based fuel.
Fig. 1 is an exemplary embodiment of the present disclosure, comprising a side view of a vehicle 1, in the form of a truck, according to an example.
Whilst the shown embodiment illustrates a truck, the disclosure may relate to any vehicle, such as a car, bus, industrial vehicle, boat, ship, etc., wherein motive power may be derived from an internal combustion engine.
The vehicle 1 comprises an internal combustion engine system 10. The internal combustion engine system may generally herein refer to the ICE system 10. Moreover, the vehicle 1 may also comprise a controller 90. The controller 90 is here part of a control system. The controller 90 may be part of the ECU of the vehicle 1. The controller 90 typically comprises a processing circuitry 91 configured to control the ICE system 10, as described herein.
The ICE system 10 will hereinafter be described in relation to Figs. 2 to 4, illustrating an example of an ICE system. More specifically, Figs. 2 and 3 show an example of an ICE system 10, in which Fig. 2 is cross-sectional view of the ICE 20 and Fig. 3 is a perspective view of the ICE 20. Purely by way of example, the Figs. 2 and 3 of the ICE system 10 may be used in the vehicle 1 of Fig. 1.
The ICE system 10 comprises a two-stroke ICE 20. The ICE 20 is operable on a fuel, such as a gaseous fuel 50 (indicated in Fig. 3). The ICE 20 may in other examples be operable on a liquid fuel. One example of a gaseous fuel is a hydrogen-based fuel. One example of a liquid fuel is an NH3-based fuel. Other examples of liquid fuels are LNG, LPG, petrol, and the like.
Moreover, the ICE system 10 is here a spark-ignition ICE system. The spark-ignited two-stroke ICE 20 is operable on a hydrogen-based fuel. The combustion in such hydrogen ICE system 10 is based on a combustion of air and hydrogen, as is commonly known in the art. While the combustion of hydrogen with oxygen may only produce water as its only product in a pure combustion process between hydrogen and oxygen, a hydrogen ICE system 10 based on combustion of air and hydrogen generally produce water, heat and NOx, as is commonly known in the art. In addition, hydrogen can be combusted in an internal combustion engine over a wide range of fuel-air mixtures. A hydrogen ICE system 10 may be operated to produce very low emissions during certain conditions. The hydrogen ICE system 10 may operate based on hydrogen liquid or hydrogen gas. The hydrogen ICE system 10 as described herein contributes to a leaner operation of the ICE 20, which is favorable from a NOx emission perspective.
As illustrated e.g. in Fig. 2, the ICE 20 comprises at least one cylinder 30 with a cylinder wall 30a. Typically, the at least one cylinder is a first cylinder 30 of the ICE 20. Hence, the ICE 20 comprises at least the first cylinder 30. However, the ICE 20 may typically comprise a number of cylinders, such as a pair of first and second cylinders, as illustrated and described in relation to Fig. 3, or a multiple number of pair of cylinders. The cylinder 30 extends in an axial direction A (Z) and in a radial direction R (Y). The cylinder 30 also has an extension in a circumferential direction C.
Thus, the cylinder wall 30a extends in the axial direction A and in the circumferential direction C. The cylinder wall 30a is an inner wall of the cylinder 30. In one example, the inner wall of the cylinder is provided by a so called a cylinder liner, as is commonly known in the art. The cylinder wall 30a may thus be part of a cylinder liner.
As depicted in Fig. 2, the cylinder 30 here also comprises a cylinder head 30b. The cylinder head 30b here defines an uppermost portion of the cylinder 30, as seen in the axial direction A.
By way of example, the cylinder head 30b may have an essentially flat bottom inner surface. Other examples of cylinder heads are also possible. The design of the combustion chamber may thus be provided in several different ways in view of the design of the cylinder head 30b. Hence, the design of the cylinder head 30b and the cylinder 30 in the figures are only provided for illustrating one example of the cylinder design.
The ICE 20 further comprises a reciprocating piston 31. The reciprocating piston 31 is moveable in the axial direction A within the cylinder 30. The reciprocating piston 31 is moveable in the axial direction A within the cylinder 30 between the bottom dead center (BDC) and the top dead center (TDC). The reciprocating piston 31 may in the following be denoted simply as the piston for ease of reference.
As illustrated in Fig. 2, the ICE system 10 further comprises a crank shaft 27 and a connecting rod 28. The connecting rod 28 is operatively connected to the piston 31, as further described below.
The piston 31 may generally comprise a suitable number of piston rings. By way of example, the piston 31 comprises one or more compression rings and oil control rings. The number of piston rings and type of piston rings are selected based on the fuel of the ICE system 10. In this example, the piston rings are arranged at a top end 33 of the piston 31.
The reciprocating piston 31 further at least partly defines a combustion chamber 32 with the top end 33 of the piston 31. The combustion chamber 32 is arranged at the end portion, i.e. the cylinder head 30b, of the cylinder 30 so that an upper surface of the top end 33 defines a lower side of the combustion chamber 32.
To provide the spark-ignition function of the ICE 20, the cylinder 30 further comprises an ignition source 34. The ignition source 34 is arranged in the combustion chamber 32. The ignition source 34 is arranged in the cylinder 30 and at a location facing the combustion chamber 32. By way of example, the ignition source 34 is arranged at an upper end of the cylinder 30, as illustrated in Fig. 2. In particular, the ignition source 34 is arranged at the cylinder head 30b of the cylinder 30. Other arrangements of the ignition source are also conceivable.
The ignition source 34 is configured to ignite the hydrogen gas supplied via a fuel arrangement, as described herein. By way of example, the ignition source 34 is a spark-plug. A spark plug is a device for delivering electric current from an ignition system to the combustion chamber of a spark-ignition engine to ignite the compressed fuel/air mixture by an electric spark, while containing combustion pressure within the engine.
In addition, the cylinder 30 of the ICE 20 comprises at least one intake port 35 arranged at a top end 36 of the cylinder 30. The intake port 35 is configured to be in fluid communication with the combustion chamber 32. The top end 36 is here an integral part of the cylinder head 30b.
Moreover, the flow of combustible gas through the at least one intake port 35 is controllable by a controllable intake valve 37. The combustible gas is one example of a fluid medium. Typically, the combustible gas comprises fresh air. In other examples, the combustible gas contains a mix of air and port injected hydrogen gas (the gaseous fuel). More specifically, in one example where the ICE system 10 is a direct injected ICE system, the intake valve 37 is controlled so that only air is supplied through the intake port 35. In another example, in which the ICE system 10 is a port injected ICE system, the intake valve 37 is controlled so that a mix of air and hydrogen fuel is supplied through the intake port 35.
The controllable intake valve 37 is arranged to open and close a fluid passage of the intake port 35, thus controlling the flow of fluid medium to the combustion chamber 32.
Further, the cylinder 30 of the ICE 20 comprises an exhaust port 38 arranged distal from the top end 36 of the cylinder 30, such that the at least one intake port 35 and the exhaust port 38 are located at different positions and separated by the piston top end 33 when the first piston 31 is in its top dead center.
The exhaust port 38 is configured to exhaust combusted gas from the cylinder 30. The exhaust port 38 is arranged distal from the top end 33 of the cylinder 30. Hereby, the intake port 35 and the exhaust port 38 are located at different positions and separated by the top end 33 when the piston 31 is in its TDC. In this context, the term "distal" means that the exhaust port 38 is arranged spaced apart from the top end 33 in a direction Z of the cylinder 30 corresponding to an axial direction of the piston 31. The top end 33 is thus considered to be a proximal part of the cylinder 30. In other words, the piston 31 is arranged in the cylinder 30 for reciprocal movement along a central axis ZA1, here extending in the direction Z. In other words, in this example, the axial direction of the piston 31 corresponds to the direction Z. The central axis ZA1 is thus arranged in parallel to the direction Z. Hence, the exhaust port 38 is arranged axially distal from the top end 33 of the cylinder 30 in the axial direction of the cylinder 30 and the piston 31, here corresponding to the direction Z.
As such, the exhaust port 38 is arranged axially distal from the top end 33 of the cylinder 30, allowing the intake port 35 and the exhaust port 38 to be fluidly separated by the piston 31.
By way of example, the exhaust port 38 is arranged at a lower to mid part 39 of the cylinder 30.
In some examples, as illustrated in Fig. 2, when the cylinder 30 comprises the cylinder liner, the cylinder liner here also comprises the exhaust port 38 located at a lower to mid part 39 of the cylinder liner. Hence, the exhaust port 38 is generally arranged distal from the top end 33 of the cylinder 30 and positioned in the cylinder wall 30a of the cylinder liner of the cylinder 30.
The exhaust port 38 is arranged in fluid communication with an exhaust duct 61. The exhaust duct 61 is arranged to transport exhaust gas away from the cylinder 30, which is depicted in e.g. Fig. 3.
Moreover, as illustrated Fig. 2, the cylinder 30 comprises an evacuation port 95. The evacuation port 95 is arranged at the top end 36 of the cylinder 30. By way of example, the evacuation port 95 is arranged in the cylinder head 30b. The evacuation port 95 typically extends through the cylinder head 30b, as illustrated in Fig. 2.
The evacuation port 95 is configured to be in fluid communication with the combustion chamber 32.
The ICE 20 further comprises a controllable evacuation valve 96 for providing an engine braking operation. As depicted in Fig. 2, the cylinder 30 comprises the controllable evacuation valve 96. The controllable evacuation valve 96 is disposed in the evacuation port 95. The controllable evacuation valve 96 is configured to provide an engine braking operation by controlling the flow of fluid medium through the evacuation port 95. More specifically, the controllable evacuation valve 96 is configured to provide engine braking by permitting the fluid medium, such as compressed air, contained in the combustion chamber 32 to discharge from the combustion chamber 32 through the evacuation port 95.
Typically, the controllable evacuation valve 96 is controllable in cooperation with the movement of the piston 31 such that the controllable evacuation valve 96 permits evacuation of fluid medium, such as compressed air, from the combustion chamber 32 via the evacuation port 95 during a compression stroke.
While the controllable evacuation valve 96 is typically controlled to an open state during the compression stroke, the controllable evacuation valve 96 can in other operating situations for other ICE system be controlled to permit evacuation of fluid medium from the combustion chamber 32 via the evacuation port 95 just after the completion of the compression stroke. Thus, the evacuation of fluid medium from the combustion chamber 32 via the evacuation port 95 may occur at various positions of the piston 31, such as at the end of the compression stroke, or just after the compression stroke.
However, the evacuation of fluid medium, such as compressed air, from the combustion chamber 32 via the evacuation port 95 may typically occurs before the intake valve 37 opens.
In some examples, the evacuation of compressed air is performed at TDC, before TDC, or slightly after the TDC. Hence, the evacuation of compressed air can occur adjacent the TDC, such as within a crank angle of 10 degrees after TDC.
The operation of engine braking can be further explained by the following piston movements within the cylinder 30. When the piston 31 travels up in the combustion chamber 32 (typically referring to the cylinder bore defined by the cylinder liner), air is compressed and provides the main resistance in the engine braking operation. Moreover, for each compression stroke, the controllable evacuation valve 96 is typically opened so as to permit the compressed air to be evacuated via the evacuation port 95. Subsequently, the piston 31 travels down to BDC and starts a new intake cycle, compresses air and thereafter permit the air out again from the evacuation port 95. On the other hand, when engine braking is not requested, the actuator 97 is deactivated, which means that the controllable evacuation valve 96 is not opening, and the ICE 20 operates in its propulsion mode. The camshaft for the engine brake is still rotating but since the actuator 97 is deactivated the camshaft rotates freely, without moving the controllable evacuation valve 96.
The controllable evacuation valve 96 can also be controlled in other ways. For example, the controllable evacuation valve 96 is controllable in cooperation with the movement of the piston 31 such that the controllable evacuation valve 96 skips evacuation of fluid medium from the combustion chamber 32 via the evacuation port 95 for a given crankshaft revolution.
In this context, the term "skips" means that, for a specific engine cycle, the controllable evacuation valve 96 does not open to allow the evacuation of fluid medium from the combustion chamber 32 through the evacuation port 95. Instead, the controllable evacuation valve 96 remains closed, preventing the fluid medium from being expelled during that engine cycle. This may allow for a more precis control of the engine braking operation.
The controllable evacuation valve 96 can be provided and designed in several different ways. In one example, as depicted in Fig. 2, the controllable evacuation valve 96 is a conventional poppet valve. The poppet valve is disposed in the cylinder head 30b. As such, the controllable evacuation valve 96 is arranged at the end of the evacuation port 95 (towards the cylinder 30), as may be gleaned from Fig. 2.
The controllable evacuation valve 96 can also be controlled in several different ways. For example, the controllable evacuation valve 96 is configured to be controllable by an actuator 97 of a controllable valve actuation assembly 63. Thus, in Fig. 2, the ICE system 10 comprises a controllable valve actuation assembly 63 for actuating the controllable evacuation valve 96. The actuator 97 is an integral part of the controllable valve actuation assembly 63.
In Fig. 2, the controllable valve actuation assembly 63 is a camshaft-driven valve actuation system, which comprises a camshaft.
Moreover, although strictly not required, the controllable valve actuation assembly 63 is here arranged and configured to actuate both the controllable evacuation valve 96 and the controllable intake valve 37. The controllable valve actuation assembly 63 is adapted to actuate the controllable evacuation valve 96 and controllable intake valves 37 in accordance with one or more lift modes during the two-stroke operation of the ICE 20.
In Fig. 2, the controllable evacuation valve 96 and the controllable intake valve 37 are actuated by a common camshaft 63 having two spaced apart actuators (cam lobes) 99, 97.
In other examples, although not illustrated, the controllable evacuation valve 96 is configured to be controllable by an actuator 97 of the controllable valve actuation assembly 63 in the form of a variable valve actuation system. One example of a variable valve actuation system is a camless system, such as a flow control valve assembly. A flow control valve assembly typically comprises an actuator in the form of a hydraulic, electric, and/or a pneumatic actuator.
The controllable valve actuation assembly 63 is configured to be controlled by a control system, such as the controller 90 (as illustrated in Fig. 1).
In Fig. 2, the controllable evacuation valve 96 is also controllable in response to an engine braking command from a control system, such as the controller 90 (as illustrated in Fig. 1). The engine braking command typically contains a signal, and/or instructions, to the controllable valve actuation assembly 63 for controlling the controllable evacuation valve 96 to open the passage in the evacuation port 95 such that compressed air can be released from the combustion chamber 32 and through the evacuation port 95, thereby providing an engine braking operation of the ICE 20. The controllable evacuation valve 96 is thus configured to provide an engine braking operation of the ICE 20.
As used herein, engine braking typically refers to an operation of the ICE 20 when the retarding forces within the ICE 20 are used to slow the vehicle 10 down. When an engine braking mode is activated by the controller 90, or by any other control system of the vehicle 10, the controllable evacuation valve 96 is controlled to an open state, or at least a partly open state, thereby releasing compressed air trapped in the cylinder 30 via the evacuation port 95, and slowing down the vehicle 10.
To route the compressed air from the evacuation port 95, the evacuation port 95 is typically fluidly connected to a subsequent fluid conduit, such as the fluid conduit 98, as depicted in the Figs. 2 and 3. Thus, the evacuation port 95 is configured to be in fluid communication with a fluid conduit for transportation of the fluid medium. The evacuation port 95 is here arranged in fluid communication with the fluid conduit 98 arranged to route the fluid medium away from the evacuation port 95. The fluid conduit 98 can be arranged in fluid communication with a storage tank (not illustrated) for storing compressed air for other use within the ICE system 10, or be routed to a position before, or after, a turbine 71 of a turbocharger system 70, as schematically illustrated in Fig. 4, and further described herein.
It should be noted that the cylinder 30 may optionally comprise a fuel injector arrangement for injecting fuel. The fuel injector arrangement is arranged in the combustion chamber 30. However, the ICE system 20 may alternatively, or in addition, be configured for port fuel injection, which means that the fuel injector arrangement is typically arranged upstream the intake port 35.
Although the fluid medium to be evacuated through the evacuation port 95 is typically compressed air, the fluid medium may in other operations, or in other ICE systems 10, constitute compressed gas, such as exhaust gas, or a mix of exhaust gas and compressed gas.
Fig. 3 depicts further details of the ICE system 10, in which the ICE system 10, and ICE 20, of Fig. 1 and 2 comprises a set of two cylinders. In Fig. 3, the at least one cylinder in Fig. 2 is denoted as the first cylinder 30. In a similar vein, the other features described in relation to Fig. 2 are in Fig. 3 denoted with the term "first". In other words, the piston in Fig. 2 is here a reciprocating first piston 31, or simply the first piston 30, the cylinder wall is here a first cylinder wall 30a, the cylinder head is here a first cylinder head 30b, the evacuation port is a first evacuation port, etc. The above examples of the arrangement of the cylinder 30, the piston 31, the cylinder wall 30a, the cylinder head 30b, the combustion chamber, the exhaust port, the intake port and the evacuation port and any other components are applicable to the first cylinder and its components as well as to any other herein-described cylinder, such as a second cylinder, a third cylinder etc.
As depicted in Fig. 3, the ICE 20 comprises the first cylinder 30 and a second cylinder 40. The first cylinder 30 comprises a first cylinder wall 30a and a first cylinder head 30b. The first cylinder wall 30a may be part of a cylinder liner. In a similar vein, the second cylinder 40 comprises a second cylinder wall 40a and a second cylinder head 40b. The second cylinder wall may be part of a corresponding cylinder liner. The first and second cylinders 30, 40 are here a pair of first and second cylinders 30, 40. Typically, although strictly not required, the first and second cylinders 30, 40 are here a pair of neighboring first and second cylinders 30, 40. In this context, the term "neighboring" generally means that the cylinders are arranged next to each other, i.e. adjacent to each other within the ICE system, so as to allow for forming a pair of cylinders operating according to the two-stroke operation. In other words, the first and second cylinders 30, 40 are arranged next to each other in the ICE 20. This may have a positive impact on the volumetric efficiency of the ICE system 10. However, it should be noted that the first and second cylinders 30, 40 may in some ICE systems be arranged slightly distanced from each other as long as the cylinders work as a pair of cylinders, i.e. the cylinders are connected to the same crank shaft and separated with a 180 crank angle degrees, as further described herein.
It should be noted that the ICE 20 may comprise any even number of cylinders. For example, the ICE 20 may comprise four, six, or eight cylinders. For ease of reference, however, the description herein is for an ICE system 10 having a pair of cylinders 30, 40.
As illustrated in Fig. 3, the ICE system 10 further comprises the crank shaft 27, a set of connecting rods, 28, 29 and a crankcase 65. The crankcase 65 is configured to accommodate the crank shaft 27 and the connecting rods 28, 29. Each one of the connecting rods 28, 29 is operatively connected to a corresponding piston, as further described below.
The ICE system 20 may also comprise an oil sump 62 and a splash plate for the oil 68. These components are conventional parts of an ICE, and not further described herein.
The first cylinder 30 is configured to accommodate the reciprocating first piston 31. The reciprocating first piston 31 is operable between a bottom dead center, BDC, and a top dead center, TDC. More specifically, the first piston 31 is arranged to reciprocate in the first cylinder 30 between the BDC and the TDC. The first piston 31 is in the TDC position at -360°, 0° and 360° CAD. The first piston 31 is via the connection rod 28 connected to the crank shaft 27, which is in line with a conventional ICE.
The first piston 31 may generally comprise a suitable number of piston rings. By way of example, the first piston 31 comprises one or more compression rings and oil control rings. The number of piston rings and type of piston rings are selected based on the fuel of the ICE system 10. In this example, the piston rings are arranged at a top end 33 of the first piston 31. The reciprocating first piston 31 further at least partly defines the first combustion chamber 32 with the top end 33 of the first piston 31. The combustion chamber 32 is arranged at the end portion, i.e. the first cylinder head 30b, of the first cylinder 30 so that an upper surface of the top end 33 defines a lower side of the first combustion chamber 32. The first cylinder 30 further comprises the ignition source 34. The ignition source 34 is arranged in the first combustion chamber 32. The ignition source 34 is arranged in the first cylinder 30 and at a location facing the combustion chamber 32. By way of example, the ignition source 34 is arranged at an upper end of the cylinder 30, as illustrated in Fig. 3. In particular, the ignition source 34 is arranged at the cylinder head 30b of the first cylinder 30. Other arrangements of the ignition source are also conceivable. In addition, the first cylinder 30 of the ICE 20 comprises the least one intake port 35 arranged at the top end 36 of the first cylinder 30 and in fluid communication with the combustion chamber 32. The top end 36 is here an integral part of the cylinder head 30b.
Moreover, the flow of combustible gas through the at least one intake port 35 is controllable by the controllable intake valve 37. In this example, the combustible gas may generally contain a mix of air and port injected hydrogen gas (the gaseous fuel). The controllable intake valve 37 is arranged to open and close a fluid passage of the intake port 35, thus controlling the flow of fluid to the combustion chamber 32. Further, the first cylinder 30 of the ICE 20 comprises the exhaust port 38 arranged distal from the top end 36 of the first cylinder 30, such that the at least one intake port 35 and the exhaust port 38 are located at different positions and separated by the piston top end 33 when the first piston 31 is in its top dead center. More specifically, as illustrated in Fig. 3, the first cylinder 30 comprises a first exhaust port 38. The first exhaust port 38 is configured to exhaust combusted gas from the first cylinder 30. The first exhaust port 38 is arranged distal from the top end 33 of the first cylinder 30. Hereby, the intake port 35 and the exhaust port 38 are located at different positions and separated by the top end 33 when the first piston 31 is in its TDC. In this context, the term "distal" means that the first exhaust port 38 is arranged spaced apart from the top end 33 in a direction Z of the first cylinder 30 corresponding to an axial direction of the first piston 31. The top end 33 is thus considered to be a proximal part of the first cylinder 30. In other words, the first piston 31 is arranged in the first cylinder 30 for reciprocal movement along a central axis ZA1, here extending in the direction Z. In other words, in this example, the axial direction of the first piston 31 corresponds to the direction Z. the central axis ZA1 is thus arranged in parallel to the direction Z. Hence, the first exhaust port 38 is arranged axially distal from the top end 33 of the first cylinder 30 in the axial direction of the first cylinder 30 and the first piston 31, here corresponding to the direction Z. By way of example, the exhaust port 38 is arranged at a lower to mid part 39 of the first cylinder 30.
In some examples, as illustrated in Fig. 3, when the first cylinder 30 comprises the first cylinder liner, the cylinder liner here also comprises the first exhaust port 38 located at a lower to mid part 39 of the cylinder liner. Hence, the first exhaust port 38 is typically arranged distal from the top end 33 of the first cylinder 30 and positioned in the cylinder wall 30a of the cylinder liner of the first cylinder 30.
The second cylinder 40 is configured to accommodate a reciprocating second piston 41. The reciprocating second piston 41 is operable between a bottom dead center, BDC, and a top dead center, TDC. More specifically, the second piston 41 is arranged to reciprocate in the second cylinder 40 between the BDC and the TDC. The second piston 41 is in the TDC position at -360°, 0° and 360° CAD. The second piston 41 is via a connection rod 29 connected to the crank shaft 27, which is in line with a conventional ICE.
The second piston 41 typically comprises a suitable number of piston rings. By way of example, the second piston 41 comprises one or more compression rings and oil control rings. The number of piston rings and type of piston rings are selected based on the fuel of the ICE system 10. In this example, the piston rings are arranged at a top end 43 of the second piston 41.
The reciprocating second piston 41 further at least partly defines a second combustion chamber 42 with a top end 43 of the second piston 41. The combustion chamber 42 is arranged at end portion, i.e. the second cylinder head 40b, of the second cylinder 40 so that an upper surface of the top end 43 defines a lower side of the second combustion chamber 42. Each one of the piston top ends may have a flat top or the piston top ends may be slightly dished so as to avoid hotspots. The second cylinder 40 further comprises a corresponding ignition source 44 arranged in the second combustion chamber 42. The ignition source 44 is arranged in the second cylinder 40 and at a location facing the combustion chamber 42. By way of example, the ignition source 44 is arranged at an upper end of the combustion cylinder 40, as illustrated in Fig. 2. In particular, the ignition source 44 is arranged at the cylinder head 40b of the second cylinder 40. Other arrangements of the ignition source are also conceivable. Each one of the ignition sources 34, 44 is here a spark plug. The ignition source may also be a glow plug.
Accordingly, in each cylinder 30, 40, there is a corresponding spark plug 34, 44 arranged to ignite a mix of fuel and oxygen in the cylinder. The hydrogen fuel is generally compressed to a certain level. The compressed air-fuel mixture is thus ignited by the spark plug.
In addition, the second cylinder 40 of the ICE 20 comprises at least one corresponding intake port 45 arranged at a top end 46 of the second cylinder 40 and in fluid communication with the second combustion chamber 42. The top end 46 is here an integral part of the cylinder head 40b. Moreover, the flow of combustible gas through the at least one corresponding intake port 45 is controllable by a corresponding controllable intake valve 47. In this example, the combustible gas may generally contain a mix of air and port injected hydrogen gas (the gaseous fuel). The controllable intake valve 47 is arranged to open and close a fluid passage of the intake port 45, thus controlling the flow of fluid to the combustion chamber 42. Further, the second cylinder 40 of the ICE 20 comprises a corresponding exhaust port 48 arranged distal from the top end 46 of the second cylinder 40, such that the at least one corresponding intake port 45 and the corresponding exhaust port 48 are located at different positions and separated by the piston top end 43 when the corresponding second piston 41 is in its top dead center.
In a similar vein to the first cylinder 30 and its exhaust port 38, the corresponding exhaust port 48 is configured to exhaust combusted gas from the second cylinder 40. The corresponding exhaust port 48 is arranged distal from the top end 43 of the second cylinder 40. Hereby, the intake port 45 and the exhaust port 48 are located at different positions and separated by the top end 43 when the second piston 41 is in its TDC. In this context, the term "distal" means that the exhaust port 48 is arranged spaced apart from the top end 43 in the direction Z of the second cylinder 40 corresponding to an axial direction of the second piston 41. The top end 43 is thus considered to be a proximal part of the second cylinder 40.
More specifically, the second piston 41 is arranged in the second cylinder 40 for reciprocal movement along a central axis ZA2, here extending in the direction Z. In other words, in this example, the axial direction of the second piston 41 corresponds to the direction Z. The central axis ZA2 is thus arranged in parallel to the direction Z. Hence, the second exhaust port 48 is arranged axially distal from the top end 43 of the second cylinder 40 in the axial direction of the second cylinder 40 and the second piston 41, here corresponding to the direction Z. By way of example, the exhaust port 48 is arranged at a lower to mid part 49 of the second cylinder 40. The exhaust port 48 is arranged at a lower to mid part 49 of the second cylinder 40 as seen along the central axis ZA2.
It should be noted that in Fig. 3, the first central axis ZA1 of the first piston 31 is arranged parallel to the second central axis ZA2 of the second piston 41. However, the pistons 31, 41 may also be arranged in a slightly different configuration where the first central axis ZA1 of the first piston 31 is arranged non-parallel to the second central axis ZA2 of the second piston 41, at least as long as the first and second cylinders are arranged separated from each other with a crank angle of 180 degrees.
In some examples, as illustrated in Fig. 3, when the second cylinder 40 comprises the second cylinder liner, the cylinder liner comprises the corresponding exhaust port 48 located at a lower to mid part 49 of the cylinder liner. Hence, the corresponding exhaust port 48 is generally arranged distal from the top end 43 of the second cylinder 40 and positioned in the cylinder wall 40a of the cylinder liner of the second cylinder 40.
As illustrated in Fig. 3, the pair of neighboring first and second cylinders 30, 40 are arranged separated from each other with a crank angle of 180 degrees (180 CAD). In this manner, the cylinders 20, 30 are separated from each other so to provide a 180 degrees combustion phasing separation. As such, the cylinders 30, 40 can be arranged in the ICE system 10 to provide a 180 degrees cycle separation irrespectively of the ICE and cylinder arrangement/configuration.
By arranging the exhaust ports 38, 48 in the lower to mid parts of the cylinders 30, 40, the respective intake ports 35, 45 and exhaust ports 38. 48 are in each cylinder 30, 40 located at different positions and separated by the respective piston top end 33, 43 when the respective piston is in its TDC. Accordingly, by arranging the respective intake port 35, 45 and exhaust port 38, 48 of the cylinders 30, 40 at different positions along the direction Z (i.e. along the axial directions of the pistons and cylinders), the corresponding piston will provide for a blocking effect between the intake and exhaust ports when the corresponding piston is in its TDC, so that the hot part of the cylinder (exhaust port and cylinder wall/liner) will be entirely separated from the combustible gas (air). The blocking effect is at least schematically illustrated in Fig. 3.
As such, the configuration of the intake and exhaust ports enables a length-scavenging ICE system that separates the hot exhaust end of each cylinder from the cold intake end where the combustibles are present. Therefore the knock risk may be reduced during operation of the ICE system 10. In comparison with a two-stroke diesel ICE using multiple cylinders, this also allows for a reversed scavenging of the corresponding combustion chamber with the controllable intake valves in the cylinder head and the exhaust ports at the cylinder wall/liner (e.g. in the lower part of cylinder wall). In other words, there are no exhaust valves in the cylinder head as compared to more conventional ICE systems.
By the combination of the arrangement of the ignition source 34, 44 and the position of the intake and exhaust ports 35, 45, 38, 48, the ICE system 10 is configured to provide a forced induction in the top of the cylinders, an ignition source for igniting the hydrogen fuel in each combustion chamber 32, 42, while further being configured to expel the exhaust gases through respective exhaust port 28, 38 in the lower to mid parts of the respective cylinder, e.g. lower parts of the walls 30a, 40a of the cylinder liners.
Moreover, the ICE system 10 in Fig. 3 is also configured to provide an engine braking operation by controlling one or more controllable evacuation valves 96, as described above in relation to Fig. 2. Hence, as illustrated Fig. 3, the first cylinder 30 comprises at least one evacuation port 95. The evacuation port 95 is arranged at the top end 36 of the first cylinder 30. By way of example, the evacuation port 95 is arranged in the cylinder head 30b. The evacuation port 95 typically extends through the cylinder head 30b, as illustrated in Fig. 3. The evacuation port 95 is configured to be in fluid communication with the combustion chamber 32. The ICE 20 further comprises the controllable evacuation valve 96 for providing the engine braking operation. As depicted in Fig. 3, the first cylinder 30 comprises the controllable evacuation valve 96. The controllable evacuation valve 96 is disposed in the evacuation port 95. The controllable evacuation valve 96 is configured to provide an engine braking operation by controlling the flow of fluid medium through the evacuation port 95. More specifically, the controllable evacuation valve 96 is configured to provide engine braking by permitting the fluid medium, such as compressed air, contained in the combustion chamber 32 to discharge from the combustion chamber 32 through the evacuation port 95. Typically, the controllable evacuation valve 96 is controllable in cooperation with the movement of the first piston 31 such that the controllable evacuation valve 96 permits evacuation of fluid medium, such as compressed air, from the combustion chamber 32 via the evacuation port 95 during a compression stroke of the first piston 31.
Analogously, as illustrated in Fig. 3, the second cylinder 40 comprises a corresponding evacuation port 95. The corresponding evacuation port 95 is arranged at the top end 46 of the second cylinder 40. By way of example, the evacuation port 95 is arranged in the cylinder head 40b. The evacuation port 95 typically extends through the cylinder head 40b, as illustrated in Fig. 3. The evacuation port 95 is configured to be in fluid communication with the combustion chamber 42. The second cylinder 40 further comprises a corresponding controllable evacuation valve 96 for providing an engine braking operation. As depicted in Fig. 3, the second cylinder 40 comprises the corresponding controllable evacuation valve 96. The corresponding controllable evacuation valve 96 is disposed in the corresponding evacuation port 95. The corresponding controllable evacuation valve 96 is configured to provide an engine braking operation by controlling the flow of fluid medium through the corresponding evacuation port 95. More specifically, the corresponding controllable evacuation valve 96 is configured to provide engine braking by permitting the fluid medium, such as compressed air, contained in the combustion chamber 42 to discharge from the combustion chamber 42 through the corresponding evacuation port 95. Typically, the corresponding controllable evacuation valve 96 is controllable in cooperation with the movement of the second piston 41 such that the corresponding controllable evacuation valve 96 permits evacuation of fluid medium, such as compressed air, from the combustion chamber 42 via the corresponding evacuation port 95 during a compression stroke of the second piston 41.
Further, as depicted in Fig. 3, the ICE system 10 comprises an air intake duct 22. The air intake duct 22 is a manifold which is arranged and configured to feed intake air to the cylinders, in this example the first and second cylinders 30, 40. The air intake duct 22 comprises a positive displacement device 23, as illustrated in Fig. 3. The positive displacement device 23 is configured to receive and feed intake air 51 to the at least one pair of neighboring cylinders 30, 40. The air intake duct 22 comprises an intake tract 24 and a plenum 25. The air intake tract 24 is arranged upstream the positive displacement device 23. The plenum 25 is arranged downstream the positive displacement device 23. The positive displacement device 23 is also arranged in the air intake duct 22 to separate the upstream intake tract 24 from the downstream plenum 25 of the air intake duct 22. It should be noted that the plenum 25 may in some examples be an integral part of the cylinder heads of the cylinders. Hence, at least parts of the air intake duct may be integral parts of the cylinder heads of the cylinders.
The positive displacement device 23 is configured to fluidly seal against back flow from the combustion chamber(s) 32, 42. Furthermore, the positive displacement device 23 is configured to exhaust its (complete) internal displacement for each revolution. The positive displacement device 23 is here a positive displacement pump. The positive displacement pump is configured to displace gas from an upstream position to a downstream position of the air intake duct 22 thereof by trapping a fixed amount of air and forcing that trapped amount of air from the upstream position to the downstream position.
By way of example, the positive displacement device 23 is a rotary roots type blower having a pair of rotary members 23a, 23b provided with meshing lobes. Other configurations of the positive displacement device may also be readily appreciated.
The positive displacement device 23 is here a variable positive displacement device configured to be operated in a variable manner. The use of a variable driven positive displacement device allows for a higher flexibility of the air intake duct forming the air intake system of the ICE system 10. The use of a variable driven positive displacement device also contributes to improve the overall function of the ICE system 10. Positive displacement devices may generally operate with flow and pressure as independent variables. This means that if pressure increases and speed remains constant, the flow rate is largely unaffected. A variable positive displacement device, such as a pump, is a device that converts mechanical energy to hydraulic (fluid) energy. The displacement can be varied while the pump is running. The positive displacement device may be driven variably for the high flexibility and improved functionality of the ICE system.
The positive displacement device 23 may be electrically driven, hydraulically driven, etc. An electrified positive displacement device may also improve turbo transients by boosting with scavenging that may also drive the turbine in the turbo. Such configuration of the ICE system may allow for reduced pressure before the displacement pump and/or after the turbo compressor reducing compressor work instantly.
The upstream intake tract 24 is here an integral part of the air intake duct 22. The intake duct 24 is by way of example provided in the form of a cylindrical shaped housing having an inner volume. The plenum 25 is also generally an integral part of the air intake duct 22. Also, as illustrated in Fig. 3, the downstream plenum 25 is in fluid communication with each one of the first and second cylinders 30, 40. By way of example, as illustrated in Fig. 3, the downstream plenum 25 is in fluid communication with each one of the first and second cylinders 30, 40 via respective intake ports 35, 45.
In Fig. 3, the downstream plenum 25 is provided in the form of a so-called Siamese-shaped design. Such Siamese-shaped design has a first inlet conduit 25a and a set of two outlet conduits 25b, 25c, as schematically illustrated in Fig. 3. The diameter and length of the inlet and outlet conduits may vary depending on the type of ICE system 10, and the plenum 25 in Fig. 3 is only schematically illustrated.
The plenum 25 comprises an air inlet 25d in fluid communication with the positive displacement device 23 and a plurality of outlets 25e, 25f configured to be in fluid communication with the intake ports 35, 45 of the first and second cylinders 30, 40, respectively. The first inlet conduit 25a has the air inlet and the outlet conduits 25b, 25c have the corresponding outlets. Accordingly, the plenum 25 is defined by the conduit arrangement between the intake ports 35, 45 of the first and second cylinders 30, 40 and the positive displacement device 23, as depicted in e.g. Fig. 3.
The plenum 25 may also be provided in other ways, e.g. by a single large inner volume defined by a common conduit. The internal volume of the plenum should generally be selected to provide an efficient backfire protection and may thus benefit from being minimized in volume in view of the other volumes of the other components.
The plenum 25 in combination with the arrangement and configuration of the positive displacement device 23 provides for an improved air supply system for supplying air to the cylinders 30, 40.
It should be noted that even though the positive displacement device 23 provides for an essentially fluid-tight seal in the air intake duct 22, it will be a continuous flow of air through the positive displacement device 23 thanks to the configuration of the cylinders 30, 40 with a 180 CAD separation, since the pair of cylinders 30, 40 interact with respect to the intake event. By the arrangement of the positive displacement device 23 in the air intake duct 22, the positive displacement device 25 is arranged to eliminate, or at least reduce, the risk of having pressure pulses transferred backwards from the combustion chambers 30, 40 to the upstream intake tract 24 of the air intake duct 22. As such, the intake ports 35, 45 are mechanically isolated from the intake tract 24. The positive displacement device 23 is thus arranged to seal the cylinders 30, 40 and the downstream plenum 25 from the upstream intake tract 24 of the air intake duct 22 (intake manifold) in case of backfire. Also, by the arrangement and configuration of the positive displacement device 23 in the air intake duct 22, the positive displacement device 23 can still provide an even flow by alternating feed to the cylinder pair 30, 40.
Moreover, the proposed ICE system provides for suppressing the tendency for knock and/or self-ignition of the fuel, such as a gaseous fuel, e.g. hydrogen-based fuel. This is e.g. provided by the combination of having a separate intake plenum 23 for each pair of cylinders 30, 40 with the 180 degrees combustion phasing separation, and where the intake duct 22 has a close coupled positive displacement device 23 for each pair of cylinders 30, 40. By arranging the positive displacement device 25 close to the cylinders, the internal volume of the plenum 25 can be minimized, thus providing for an even more efficient backfire protection.
Similar to the example of the ICE system in Fig. 2, the ICE system 20 in Fig. 3 comprises a fuel injector arrangement 26. In Fig. 3, the fuel injector arrangement 26 is arranged in the plenum 25 of the air intake duct 22 so as to provide a fuel injection upstream the intake ports 35, 45 of the cylinders 30, 40. In this manner, there is provided an improved injection of fuel into the combustion chambers 32, 42 of the ICE 20.
The fuel injector arrangement 26 comprises at least one fuel injector configured inject fuel. In Fig. 3, the fuel injector arrangement 26 comprises a set of two fuel injector, 26a, 26b. There is generally one fuel injector 26a, 26b arranged upstream respective intake port 35, 45. By way of example, the outlet conduit 25b comprises a first fuel injector 26a and the outlet conduit 25c comprises the second fuel injector 26b. Hereby, the ICE system 10 is configured to provide port injection of the gaseous fuel 50 upstream respective intake port 35, 45. The use of a port injection allows for providing a homogenous mixture which enables an improved knock and auto-ignition control and contribute to reduce the emissions.
The fuel injector arrangement 26 is operable / controllable in response to a fuel injection event such that fuel injection is injected to one or more of the corresponding intake ports 35, 45 such that pressure pulses are generated in the plenum 25 and subsequently travel into the corresponding combustion chambers 32, 42. Hereby, there is provided an improved scavenging effect. As such, the ICE system 10 is configured to provide a scavenging effect by the injection timing in the respective intake port 35, 45.
By way of example, the fuel injector arrangement 26 is operable / controllable to provide a sequential injection of fuel to the cylinders 30, 40 so as to allow for an active cylinder scavenging during a latter part of a corresponding intake stroke of a corresponding cylinder of the cylinders 30, 40. Put it differently, a sequential injection enables active cylinder scavenging (emptying of exhaust) during latter part of the intake stroke and creates a final pressure pulse (from the injected fuel) that increases the trapped mass in the cylinder after any exhaust port and intake valve closures. This may also contribute to a fuel-free plenum and/or intake port after the intake valve closure. Further, the generated pressure pulse increases the scavenging effect. It may be noted that the sequential injection can be tuned for different speeds and valve timings.
Typically, the pressure pulse will also travel backwards in the downstream plenum 25. For instance, the pressure pulse will be reflected in the sister cylinder intake valve that is closed. Thereafter, the pressure pulse travels back to the still open intake valve and enters the cylinder with the open valve and complete the cylinder filling, thus also contributing to the complete trapped mass.
In some examples, although not illustrated, the fuel injectors 26a, 26b of the fuel injector arrangement 26 may be arranged in each one of the combustion chambers of the cylinders.
Although not illustrated, the ICE system 10 in Fig. 3 may be provided with a number of two intake valves 37 for the first cylinder 30 and a number of two controllable intake valves 47 for the second cylinder 40. Hence, in some examples, each one of the cylinder heads 30b, 40b comprises a number of at least two controllable intake valves. In some examples, each one of the cylinder heads 30b, 40b of the first and second cylinders 30, 40 may have a plurality of controllable intake valves.
In Fig. 3, the controllable intake valves 37, 47 are configured to provide variable valve actuation. The variable valve actuation can be provided by a hydraulic system, electronic system or pneumatic system. However, the controllable intake valves 37, 47 may also be conventional controllable intake valves, such as a camshaft-based system, as is commonly used in diesel ICE systems. Hence, in some examples, the controllable intake valves are conventional camshaft actuated valves. Such camshaft actuated valves may also include variable valve actuation depending on arrangement and configuration of the valves.
In Fig. 3, the controllable valve actuation assembly 63 is arranged for actuating the controllable evacuation valves 96, the inlet control valve 37 and the corresponding inlet control valve 47. The valve actuation assembly 63 is adapted to actuate the controllable evacuation valve 96 and the inlet control valves 37, 47 in accordance with one or more lift modes during the combustion cycle of the ICE system 10.
As may also be gleaned from Fig. 3, each one of the exhaust ports 38, 48 is arranged in fluid communication with the exhaust duct 61 arranged to transport exhaust gas away from each one of the cylinders.
Fig. 4 is another example of the ICE system 10. The ICE system 10 here comprises the features and components of the ICE system 10 as described in relation to Figs. 2 and 3. The ICE system 10 illustrated in Fig. 4 differs from that shown in Figs. 2 and 3 in that the ICE system 10 also comprises the turbocharger arrangement 70. The turbocharger arrangement 70 comprises the turbocharger turbine 71 operatively connected to a turbocharger compressor 72, wherein the turbocharger compressor 72 is arranged in an air intake conduit 73 in fluid communication with the air intake duct 22. The turbocharger turbine 71 is arranged in the exhaust duct 61 so as to drive the turbocharger compressor 72. In other words, the turbine 71 is configured to convert engine exhaust gas into mechanical energy to drive the compressor 72.
The turbocharger turbine 71 may be a conventional turbine for an ICE system 10. Alternatively, the turbocharger turbine 71 may be a variable geometry turbine in fluid communication with the cylinders.
As illustrated in Fig. 4, the evacuation port 95 is arranged in fluid communication with a fluid conduit 98 arranged to route the fluid medium to a position 93 downstream of the turbine 71 of the turbocharger system 70.
Alternatively, or in addition, as illustrated in Fig. 4, the evacuation port 95 is arranged in fluid communication with a fluid conduit 98 arranged to route the fluid medium to a position 94 upstream of the turbine 71 of the turbocharger system 70. This may also typically contribute to higher boost during engine braking, i.e., more mass is trapped in the cylinder, which provides for higher compression and brake power.
As further illustrated in Fig. 4, the ICE system 10 comprises a controllable exhaust brake valve 64 disposed in the exhaust duct 61 downstream of the exhaust port 38. The controllable exhaust brake valve 64 is configured to restrict the flow of exhaust gases exiting the exhaust port 38, thereby creating back pressure that acts against the piston movement in the cylinder 30. In this manner, the engine braking operation can be further controlled during operation of the ICE system 10 and the vehicle 1. The controllable exhaust brake valve 64 may typically be provided in the form of a conventional exhaust valve as is commonly known in the art. By way of example, the controllable exhaust brake valve is a controllable butterfly valve, or the like.
In addition, or alternatively, the evacuation port 95 is also configured to be in fluid communication with the controllable exhaust brake valve 64. Hence, the flow of fluid medium from the evacuation port 95 is allowed to flow to the exhaust duct 61. Typically, the fluid conduit 98 (from the evacuation port 95) is arranged in fluid communication with the controllable exhaust brake valve 64. By this arrangement, the controllable exhaust brake valve 64 is configured to restrict the flow of exhaust gases exiting the evacuation port 95, thereby creating back pressure that acts against the piston movement in the cylinder 30.
It should be noted that an air charging system may typically need to compensate with boost pressure accordingly to maintain the scavenging flow, which is at least partly due to that the two-stroke ICE 20 is typically open during scavenging. Scavenging is the process of flushing out exhaust gases from the cylinder and replacing them with a fresh air-fuel mixture. Two-stroke ICE systems 10 are different to four-stroke ICE systems, which lead to other challenges in efficiently managing air flow. The boost pressure compensation can typically be provided by the positive displacement device and/or the turbocharger that is driven independently, or partly by the exhaust gases. Accordingly, in one example, the ICE system 10 is operable to control the boosting level by mechanical or electrical boosting (using e.g. the positive displacement device and/or the turbocharger) in combination with the controllable exhaust brake valve 64 in the exhaust duct 61.
Moreover, in some examples, the flow of fluid medium from the evacuation port 95 is allowed to flow to the exhaust duct 61 downstream of the controllable exhaust brake valve 64. Typically, in such example, the fluid conduit 98 (from the evacuation port 95) is arranged in fluid communication with the exhaust duct 61 downstream of the controllable exhaust brake valve 64. Such arrangement may lead to a lower cylinder pressure at TDC during engine braking, further facilitating the engine braking operation as a lower portion of warmed air is remained in the system.
The controllable exhaust brake valve 64 is here disposed upstream (upstream position 69) of the turbine 71 of the turbocharger system 70. In other examples, the controllable exhaust brake valve 64 is disposed downstream of the turbine 71 of the turbocharger system 70.
In Fig. 4, the ICE system 10 further comprises an exhaust gas recirculation, EGR, system 80 comprising an EGR conduit 81 arranged to connect the exhaust duct 61 and the air intake duct 22 so as to permit recirculation of exhaust gas through the cylinders during operation of the ICE 20.
The EGR system 80 here further comprises a corresponding positive displacement device 82. The positive displacement device 82 is disposed in the EGR conduit 81. The positive displacement device 82 is generally of the same type as the device 23 but may also be provided in other ways. The positive displacement device 82 is by way of example a roots blower.
The EGR conduit 81 connects to the air intake conduit 73 at a position 84 downstream the turbocharger compressor 72 and further connects to the exhaust duct 61 at a position 85 upstream the turbocharger turbine 71.
Typically, as illustrated in Fig. 4, the ICE system 10 may also comprise an air cooler 67, such as charge air cooler (CAC). By way of example, the CAC 67 is arranged in the air intake conduit 73. More specifically, the CAC 67 is arranged in the air intake conduit 73 between the turbocharger compressor 72 and the air intake duct 72, as seen in a direction of flow from the compressor 72 to the air intake duct 22.
It should be readily appreciated that the air intake duct of Fig. 3 and/or Fig. 4 may have its own inlet for receiving fresh air from the outside and/or be configured to receive air from the air intake conduit 73.
Moreover, in the ICE system 10 of Figs. 2 to 4, the ICE system 10 further comprises the controller 90 configured to collectively control the positive displacement device 23 and the intake valves 37, 47 so as to control flow of gas to the respective combustion chambers 32, 42, and further configured to control the controllable evacuation valves 96 to provide engine braking, as described herein.
The controller 90 is also configured to terminate fuel injection during an intake phase and before an intake valve closure, whereby the remaining part of the intake phase comprises emptying the plenum 25 of fuel and subsequently introducing fresh air to the plenum 25 by operating the positive displacement device 23.
Typically, it should be noted that each one of the first and second cylinders 30, 40 has three primary events. These events are compression event, combustion and work event, and exhaust and intake event. The compression event occurs when a corresponding piston is at an upper half of the corresponding cylinder when it travels from BDC to TDC. The combustion and work event occurs when a corresponding piston is at an upper half of the corresponding cylinder when it travels from TDC to BDC. The exhaust and intake event generally occurs when a corresponding piston is at a lower half of the corresponding cylinder. By way of examples, the exhaust and intake event occurs when a corresponding piston is at a lower half of the cylinder and is travelling towards its BDC, across its BDC and/or when the corresponding piston is at a lower half of the cylinder and is travelling towards its TDC.
It should, however, be noted that the exhaust and intake event may occur in different regions of the cylinders, and can be slightly divided, but the exhaust and intake event will generally occur at the same time. During the exhaust and intake event, the ICE system provides the scavenging effect, i.e. fresh intake gas pushes the residual exhaust out the exhaust port.
In view of the above, the piston 31, 41 of one of the cylinders 30, 40 may generally perform the compression stroke / compression phase (or event) during about 270 - 0 CAD, followed by the combustion and work phase (event) during 0-90 CAD at an upper half of the corresponding cylinder when the piston travels from TDC to BDC, while the other piston of the other cylinder performs the exhaust and intake phase (event) at a lower half of the other cylinder during 90 to 270 CAD. It may also be noted that there is generally an overlap between the end of the combustion and work phase (event) and the start of the exhaust and intake phase (event).
More specifically, the controllable intake valve 37 of the first cylinder 30 is operable in correlation with the movement of the first piston 31 and the controllable intake valve 47 of the second cylinder 40 is operable in correlation with the movement of the second piston 41. In this manner, the fluid communication between the respective combustion chambers 32, 42 and the plenum 25 is selectively open and closed during a crank shaft revolution of the ICE 20. As mentioned herein, such configuration of the ICE system 10 in combination with the positive displacement device 23 in the air intake duct 22 allows for reducing risk of backfire.
The inlet control valve 37 and the corresponding inlet control valve 47 are controlled and actuated by the controllable valve actuation assembly 63. Purely by way of example, the control valve actuation assembly 63 may comprise an electric actuator (not shown) adapted to actuate the inlet control valve(s) in at least two lift modes, i.e. between an open mode and a closed mode.
In addition, as mentioned above, the cylinders 30, 40 are separated from each other with a crank angle of 180 degrees. Such arrangement and configuration of the ICE system 20 allows for 180 degrees combustion phasing separation. Due to the arrangement of the first and second cylinders 30, 40 being arranged separated from each other with a crank angle of 180 degrees, the ICE system 10 is configured to operate the intake valves 37, 47 of the first and second cylinders 30, 40 such that the intake valves 37, 47 of the cylinders 30, 40 are completely closed when the respective piston is halfway up in the cylinder, which may further reduce the risk of a backfire. To this end, by the configuration of having the first and second cylinders 30, 40 separated from each other by 180 crank angle degrees in combination with the arrangement of the positive displacement device 23, it becomes possible to reduce the risk of backfire. Also, it should be readily appreciated that at injection, after scavenging has started, the injected hydrogen fuel will expand and create a pulse in the intake ports and plenum. This pulse will propagate and add to the scavenging effect and also increase the pressure in the cylinder. However, the pulse is limited from travelling backwards in the air intake duct (air intake system) by the positive displacement device 23 acting like a check valve and also momentarily adding boost pressure during the pulse.
In operation of the ICE system 10, the ICE system 10 may perform the following method: In a step S10, when a piston is travelling down from TDC to BDC in one of the cylinders during expansion of the combustibles and a corresponding exhaust port is uncovered, the effective work stroke is ended, and the gases are exhausted through the exhaust port. Subsequently, in a step S20, the intake valve(s) of one of the cylinder opens and the cylinder is purged by incoming air fed by the aforementioned boosting system (e.g. by the turbocharger arrangement 70 and the positive displacement device 23). At this stage there is no fuel present in the boost mass or the cylinder. Then, in step S30, the piston reaches BDC. Thereafter, in step S40, the piston starts to move up towards its TDC and the piston eventually covers the exhaust port again. At this position, the fuel injector arrangement is operated to inject e.g. hydrogen fuel. The hydrogen fuel is injected into the intake port, creating the pressure pulse from the injected hydrogen fuel. As such, the ICE system 10 is operated to start injecting hydrogen gas into the air stream in the plenum 25, thus feeding air and hydrogen into the cylinder. The injection starts after the intake valve has opened just after the initial scavenging (cylinder purge) and ends before the intake valve closes which provides an essentially intake tract free of combustible gas. Initial scavenging of the cylinder (purging) is the time between IVO and start of hydrogen gas injection. In step S50, the piston continues to travel up (about halfway) through the stroke and the intake valves closes. In step S60, the piston travels to just before TDC, TDC or just after TDC (i.e. close to TDC). Subsequently, in step S70, the ignition source (e.g. a spark plug) ignites the homogenous air/hydrogen mix in the cylinder(s). Then, in step S80, the piston is forced down in the work stroke (expansion). Thereafter, in step S90, the cycle repeats from above steps S10 to S80. Moreover, during some driving operations, there is a need for activating engine braking. By way of example, engine braking is activated and performed during the compression phase / compression stroke. More specifically, during the compression phase / compression stroke, the controllable evacuation valve 96 is controlled in response to the engine braking command from the controller 90, whereby the controllable evacuation valve 96 is controlled from its closed state to its open state. In the open state of the controllable evacuation valve 96, compressed air contained in the combustion chamber 32 is allowed to flow from the combustion chamber 32 through the evacuation port 95 (and in the open state of the controllable evacuation valve 96). As such, when engine braking is activated, the evacuation valve 96 is controlled to modify the operation of the ICE 20 so that the compressed air in the combustion chamber 32 is released through the evacuation port 95. In this mode of operation of the ICE, denoted as the engine braking operation of the ICE 20, each piston stroke acts as a braking stroke. This mean that braking power is generated during the compression of fluid medium while both the intake valve 35 and the evacuation valve 95 are in their closed positions. The opening of the evacuation valve 95 facilitates decompression, preventing the transfer of energy back during the expansion stroke. Hereby, the ICE 20 operates in an engine braking mode, leading to the deceleration of the piston movement, which in turn slows down the engine and the vehicle.
As should be readily appreciated from the above, the operation of purging, scavenging and subsequent fuel injection operation, creating a boost pulse, as well as the ending of fuel injection where hydrogen (H2)/air mixture is pushed into the cylinder allows for emptying the plenum 25, while the positive displacement device 23 is operated to push in fresh air in the plenum 25. In this manner, the arrangement and configuration of the ICE system 10 provides for avoiding, or at least reducing the risk of having hydrogen mixture in the plenum 25, hence, reducing the risk for backfire.
It should be noted that if the intake valves are opened all at the same time, a flow effect in the whole cross section area of the cylinder can be obtained so that the cylinder is filled homogenously from top to bottom, driving out the exhaust gases so that low mixing between the fresh charge air and the warm exhaust combustibles is obtained. This may be useful so as to reduce the mixture temperature and residuals in preparation of the mixture. The intake valves are then completely closed when the piston is halfway up in the cylinder which reduces the risk of a backfire.
It should be noted that the above presentation of the ICE system 10 should also be regarded as disclosing a method for controlling the ICE system 10, for instance using the controller 90.
The combustion chambers can be designed in several different manners and may be any one of a flat, hemispherical, or pent roof design with only intake valves. It may be beneficial to cover a large area of the combustion chamber with valves so that the cylinder filling can be made in an efficient manner.
All moving parts in the ICE 20 may generally be lubricated by means of conventional pressure lubrication. Other options are also possible.
The positive displacement device 23 and the plenum 25 of the air intake duct 22 are generally considered to be the cold components and may be made from an aluminum alloy. The air intake duct 22 may typically be fastened to the cylinder heads that may be warmer, which is made of cast iron or steel. This may minimize the risk of hydrogen embrittlement since no gas containing hydrogen comes into contact with any iron or steel that is colder than 150 degrees C, which is the threshold when hydrogen embrittlement is considered to occur.
The ICE system 10 can be cooled in several different ways. By way of example, the ICE system 10 comprises a controlled low temperature coolant circuit for temperature control of the CAC (Compressed Air Cooler) and/or the EGR cooler. By this, the condensation level of the returned water from the combustibles (H2 produce H2O when combusted) is controlled. In addition, the ICE system 10 may comprise water injection system. The water injection system can be arranged and configured to inject water in the intake port(s), directly into the cylinder, or prior to the intake positive displacement device 23. Moreover, the condensed water from the exhaust can be used for water injection. If it is injected prior to the positive displacement device, there is a benefit of mixing and evaporation/ cooling in the roots blower. The water injection as a temperature reduction medium for the boost air after the positive displacement device is an advantage in examples where the positive displacement device is used for compression work for additional boosting.
It should be noted that the ICE system 10 may not be restricted to a system with one single pair of cylinders 30, 40, but can also be implemented in an ICE system comprising four cylinders, six cylinders etc. Hence, the ICE system 10 may have a minimum of two cylinders, but multiples of two cylinders may likewise be possible.
In ICE systems 10 further comprising additional pairs of neighboring cylinders, each arrangement of a pair of neighboring cylinders has a corresponding air intake duct with a corresponding positive displacement device.
In other words, a four-cylinders ICE will have two positive displacement devices and a six-cylinder ICE will have three positive displacement devices. Such ICE system may also use a positive displacement device with a plurality of separated sections, wherein each section is provided to cooperated with a given pair of cylinders. In this arrangement, the flow of fluid (air) to each pair of cylinders should be separated from each other. The cylinder pairs can be arranged spaced-apart so as to allow for ignition of fuel for three cylinders at once (flat crank) or arranged evenly offset from each other for an evenly spread firing order. In this way, it becomes possible to charge one cylinder in the pair at the time without creating unwanted pulsation since one cylinder is in its intake stroke while the other one is in its work stroke.
Moreover, the present disclosure may be exemplified by any one of the below examples.
Example 1: An internal combustion engine ICE system 10 for a vehicle 1, the ICE system comprising a two-stroke ICE 20 operable on a fuel 50, the ICE having at least one cylinder 30 with a cylinder wall 30a and further a reciprocating piston 31 moveable in an axial direction A within the cylinder between a bottom dead center BDC and a top dead center TDC, the at least one cylinder at least partly defining a combustion chamber with a top end 33 of the piston, wherein the at least one cylinder comprises at least one intake port 35 arranged at a top end 36 of the at least one cylinder, and further configured to be in fluid communication with the combustion chamber, an exhaust port 38 arranged axially distal from the top end of the at least one cylinder, allowing the at least one intake port and the exhaust port to be fluidly separated by the piston, and wherein the at least one cylinder further comprises an evacuation port 95 arranged at the top end of the at least one cylinder, the evacuation port being configured to be in fluid communication with the combustion chamber, and a controllable evacuation valve 96 disposed in the evacuation port and configured to provide an engine braking by controlling the flow of fluid medium through the evacuation port.
Example 2: ICE system according to example 1, wherein the controllable evacuation valve is controllable in cooperation with the movement of the piston such that the controllable evacuation valve permits evacuation of fluid medium from the combustion chamber via the evacuation port during a compression stroke.
Example 3. ICE system according to example 1 or example 2, wherein the controllable evacuation valve is controllable in cooperation with the movement of the piston such that the controllable evacuation valve skips evacuation of fluid medium from the combustion chamber via the evacuation port for a given crankshaft revolution.
Example 4. ICE system according to any one of the preceding examples, wherein the controllable evacuation valve is configured to be controllable by an actuator of a camshaft-driven valve actuation system.
Example 5. ICE system according to any one of the preceding examples 1 to 3, wherein the controllable evacuation valve is configured to be controllable by an actuator of a variable valve actuation system.
Example 6. ICE system according to any one of the preceding examples, wherein the controllable evacuation valve is controllable in response to an engine braking command from a control system.
Example 7. ICE system according to any one of the preceding examples, wherein the evacuation port is arranged in fluid communication with a fluid conduit arranged to route the fluid medium to a position downstream of a turbine 71 of a turbocharger system 70, or to a position upstream of the turbine of the turbocharger system.
Example 8. ICE system according to any one of the preceding examples, further comprising a controllable exhaust brake valve disposed in an exhaust duct 61 downstream the exhaust port, the controllable exhaust brake valve being configured to restrict the flow of exhaust gases in the exhaust duct.
Example 9. ICE system according to any one of the preceding examples, wherein the ICE system is a spark-ignition ICE system, and the at least one cylinder having an ignition source 34 arranged in the combustion chamber.
Example 10. ICE system according to any one of the preceding examples, wherein the ICE system comprises a fuel injector arrangement for injecting fuel, the fuel injector arrangement being arranged in the combustion chamber, or the fuel injector arrangement being arranged upstream the at least one intake port to provide a port fuel injection arrangement.
Example 11. ICE system according to any one of the preceding examples, wherein the flow of intake gas through the at least one intake port is controllable by a controllable intake valve 37.
Example 12. ICE system according to any one of the preceding examples, wherein the at least one cylinder is a first cylinder and the piston is a first piston, and the ICE further having a second cylinder forming a pair of cylinders with the first cylinder, the second cylinder accommodating a corresponding reciprocating second piston 41 operable between a bottom dead center and a top dead center, and further at least partly defining a second combustion chamber 42 with a top end 43 of the second piston, wherein the second cylinder further comprises a corresponding ignition source 44 arranged in the second combustion chamber, at least one corresponding intake port 45 arranged at a top end 46 of the second cylinder and in fluid communication with the second combustion chamber, and further a corresponding exhaust port 48 arranged axially distal from the top end of the second cylinder, allowing the at least one corresponding intake port and the corresponding exhaust port to be fluidly separated by the second piston.
Example 13. ICE system according to example 12, wherein the first and second cylinders are separated from each other with a crank angle of 180 degrees.
Example 14. ICE system according to example 12 or example 13, further comprising an air intake duct 22 having a positive displacement device 23 configured to receive and feed intake air to the pair of cylinders, the positive displacement device further being arranged in the air intake duct to separate an upstream intake tract 24 from a downstream plenum 25 of the air intake duct, the downstream plenum being in fluid communication with each one of the first and second cylinders of the pair of cylinders.
Example 15. ICE system according to any one of the preceding examples, wherein the ICE system is a hydrogen ICE system configured to operate on a gaseous fuel containing a hydrogen-based gaseous fuel.
Example 16. A vehicle comprising an internal combustion engine system according to any one of the examples 1 to 15.
As used herein, the terms "upstream" and "downstream" refer to the relative direction with respect to fluid flow in a fluid pathway. For example, "upstream" refers to the direction from which the fluid flows, and "downstream" refers to the direction to which the fluid flows.
Also, the term "longitudinal", "longitudinally", "axially" or "axial" refer to a direction at least extending between axial ends of a particular component, typically along the arrangement or components thereof in the direction of the longest extension of the arrangement and/or components. The terms "vertical" and "vertically" generally correspond to the axial direction.
The terminology used herein is for the purpose of describing particular aspects only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. It will be further understood that the terms "comprises," "comprising," "includes," and/or "including" when used herein specify the presence of stated features, integers, actions, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, actions, steps, operations, elements, components, and/or groups thereof.
It will be understood that, although the terms first, second, etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element without departing from the scope of the present disclosure.
Relative terms such as "below" or "above" or "upper" or "lower" or "horizontal" or "vertical" may be used herein to describe a relationship of one element to another element as illustrated in the Figures. It will be understood that these terms and those discussed above are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element, or intervening elements may be present. In contrast, when an element is referred to as being "directly connected" or "directly coupled" to another element, there are no intervening elements present.
Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.
It is to be understood that the present disclosure is not limited to the aspects described above and illustrated in the drawings; rather, the skilled person will recognize that many changes and modifications may be made within the scope of the present disclosure and appended claims. In the drawings and specification, there have been disclosed aspects for purposes of illustration only and not for purposes of limitation, the scope of the disclosure being set forth in the following claims.

Claims

An internal combustion engine (ICE) system (10) for a vehicle (1), the ICE system comprising:
a two-stroke ICE (20) operable on a fuel (50),

the ICE having at least one cylinder (30) with a cylinder wall (30a) and further a reciprocating piston (31) moveable in an axial direction (A) within the cylinder between a bottom dead center (BDC) and a top dead center (TDC), the at least one cylinder at least partly defining a combustion chamber with a top end (33) of the piston,

wherein the at least one cylinder comprises at least one intake port (35) arranged at a top end (36) of the at least one cylinder, and further configured to be in fluid communication with the combustion chamber,

an exhaust port (38) arranged axially distal from the top end of the at least one cylinder, allowing the at least one intake port and the exhaust port to be fluidly separated by the piston, and

wherein the at least one cylinder further comprises an evacuation port (95) arranged at the top end of the at least one cylinder, the evacuation port being configured to be in fluid communication with the combustion chamber, and a controllable evacuation valve (96) disposed in the evacuation port and configured to provide an engine braking by controlling the flow of fluid medium through the evacuation port.
ICE system according to claim 1, wherein the controllable evacuation valve is controllable in cooperation with the movement of the piston such that the controllable evacuation valve permits evacuation of fluid medium from the combustion chamber via the evacuation port during a compression stroke.
ICE system according to claim 1 or claim 2, wherein the controllable evacuation valve is controllable in cooperation with the movement of the piston such that the controllable evacuation valve skips evacuation of fluid medium from the combustion chamber via the evacuation port for a given crankshaft revolution.
ICE system according to any one of the preceding claims, wherein the controllable evacuation valve is configured to be controllable by an actuator of a camshaft-driven valve actuation system.
ICE system according to any one of the preceding claims 1 to 3, wherein the controllable evacuation valve is configured to be controllable by an actuator of a variable valve actuation system.
ICE system according to any one of the preceding claims, wherein the controllable evacuation valve is controllable in response to an engine braking command from a control system.
ICE system according to any one of the preceding claims, wherein the evacuation port is arranged in fluid communication with a fluid conduit arranged to route the fluid medium to a position downstream of a turbine (71) of a turbocharger system (70), or to a position upstream of the turbine of the turbocharger system.
ICE system according to any one of the preceding claims, further comprising a controllable exhaust brake valve disposed in an exhaust duct (61) downstream the exhaust port, the controllable exhaust brake valve being configured to restrict the flow of exhaust gases in the exhaust duct.
ICE system according to any one of the preceding claims, wherein the ICE system is a spark-ignition ICE system, and the at least one cylinder having an ignition source (34) arranged in the combustion chamber.
ICE system according to any one of the preceding claims, wherein the ICE system comprises a fuel injector arrangement for injecting fuel, the fuel injector arrangement being arranged in the combustion chamber, or the fuel injector arrangement being arranged upstream the at least one intake port to provide a port fuel injection arrangement.
ICE system according to any one of the preceding claims, wherein the at least one cylinder is a first cylinder and the piston is a first piston, and the ICE further having a second cylinder forming a pair of cylinders with the first cylinder, the second cylinder accommodating a corresponding reciprocating second piston (41) operable between a bottom dead center and a top dead center, and further at least partly defining a second combustion chamber (42) with a top end (43) of the second piston, wherein the second cylinder further comprises a corresponding ignition source (44) arranged in the second combustion chamber, at least one corresponding intake port (45) arranged at a top end (46) of the second cylinder and in fluid communication with the second combustion chamber, and further a corresponding exhaust port (48) arranged axially distal from the top end of the second cylinder, allowing the at least one corresponding intake port and the corresponding exhaust port to be fluidly separated by the second piston.
ICE system according to claim 11, wherein the first and second cylinders are separated from each other with a crank angle of 180 degrees.
ICE system according to claim 11 or claim 12, further comprising an air intake duct (22) having a positive displacement device (23) configured to receive and feed intake air to the pair of cylinders, the positive displacement device further being arranged in the air intake duct to separate an upstream intake tract (24) from a downstream plenum (25) of the air intake duct, the downstream plenum being in fluid communication with each one of the first and second cylinders of the pair of cylinders.
ICE system according to any one of the preceding claims, wherein the ICE system is a hydrogen ICE system configured to operate on a gaseous fuel containing a hydrogen-based gaseous fuel.
A vehicle comprising an internal combustion engine system according to any one of the claims 1 to 14.