Technical field of the invention

The present invention relates to a crossflow cylinder head for a single cylinder of a multi-cylinder piston engine, as defined in claim 1 . The invention also concerns a cylinder head assembly for a piston engine and a piston engine.

Background of the invention

In large piston engines, such as in engines used as main or auxiliary engines in ships or in engines used at powerplants for producing electricity, each cylinder of the engine is provided with an own cylinder head. The cylinder head closes the upper end of the cylinder and delimits a main combustion chamber. In four-stroke engines, the cylinder head serves for several purposes. For instance, the cylinder head is provided with an inlet channel for introducing intake air into the combustion chamber and with an exhaust channel for discharging exhaust gas from the combustion chamber.

As the cylinder head is in direct contact with the combustion chamber and the hot exhaust gas flows through the cylinder head, cooling of the cylinder head is needed to control the temperature of the cylinder head. Excessive temperatures may damage the cylinder head and components attached to the cylinder head. However, also excessive cooling is harmful, as it can reduce the efficiency of the engine. In particular, the temperature of the exhaust gas should be high to ensure effective operation of turbochargers. of the invention

An object of the invention is to provide an improved crossflow cylinder head for a single cylinder of a multi-cylinder four-stroke piston engine. The characterizing features of the cylinder head according to the invention are presented in claim 1 . Another object of the invention is to provide an improved cylinder head assembly. A further object of the invention is to provide an improved piston engine.

The cylinder head according to the invention has a bottom surface configured to face a cylinder of an engine and a top surface facing an opposite direction, and an intake side and an exhaust side. The cylinder head comprises - an inlet channel arranged on the intake side,

- an exhaust channel arranged on the exhaust side,

- a first intake valve hole and a second intake valve hole arranged on the intake side, each intake valve hole extending from the bottom surface to the top surface and being configured to receive an intake valve,

- a first exhaust valve hole and a second exhaust valve hole arranged on the exhaust side, each exhaust valve hole extending from the bottom surface to the top surface and configured to receive an exhaust valve, and

- a cooling liquid cavity.

The cylinder head further comprises an integral extension formed on the exhaust side, the extension comprising a first push rod passage and a second push rod passage, each of the first push rod passage and the second push rod passage being configured to allow through passage of a push rod that is configured to operate intake and/or exhaust valves of the cylinder, the exhaust channel being arranged to pass in the extension between the first push rod passage and the second push rod passage.

The integral extension on the exhaust side improves the efficiency, reliability and safety of the engine. The extension, and in particular the push rod passages arranged on the sides of the exhaust channel reduce heat radiation from the exhaust channel. This helps both keeping the exhaust gas temperature high, which allows effective energy recovery in turbochargers, and reduces surface temperatures of the engine, thus improving the safety of the engine. The push rod passages also allow collecting oil leakages from valve actuators and preventing the oil from contacting exhaust duct components.

According to an embodiment of the invention, the cooling liquid cavity is at least partly arranged in the extension of the cylinder head. That reduces further heat radiation from the exhaust channel.

According to an embodiment of the invention, the cylinder head comprises at least one cooling liquid outlet that is arranged in the extension of the cylinder head for discharging cooling liquid from the cooling liquid cavity. Cooling liquid conducted from the cylinder head through the extension provides an improved heat shield in the cylinder head and allows the cooling liquid to be introduced into an external component for blocking heat from the exhaust system. According to an embodiment of the invention, the cylinder head comprises at least one cooling liquid outlet arranged in the extension below the exhaust channel. That allows discharging cooling liquid from the cylinder head below the exhaust channel and forming a heat shield below an exhaust manifold.

According to an embodiment of the invention, the cylinder head comprises at least one cooling liquid outlet arranged in the extension above the exhaust channel. That allows discharging cooling liquid from the cylinder head above the exhaust channel and forming a heat shield above or on the side of an exhaust manifold.

According to an embodiment of the invention, the cylinder head comprises at least two cooling liquid outlets arranged in the extension above the exhaust channel. That allows a larger portion of the cooling liquid to be circulated above the exhaust channel, where temperatures are high.

According to an embodiment of the invention, the cooling liquid cavity comprises a lower portion arranged on the bottom surface side of the exhaust channel and an upper portion arranged on the top surface side of the exhaust channel. This ensures effective cooling of the cylinder head around the exhaust channel and forms a heat shield around the exhaust channel.

According to an embodiment of the invention, the cylinder head comprises a cooling liquid duct for introducing cooling liquid into the cooling liquid cavity.

According to an embodiment of the invention, the cooling liquid duct comprises a first branch for introducing cooling liquid into the lower portion of the cooling liquid cavity and a second branch for introducing cooling liquid into the upper portion of the cooling liquid cavity. That ensures effective cooling in both portions of the cooling liquid cavity.

According to an embodiment of the invention, the cooling liquid duct has an inlet end opening onto the bottom surface of the cylinder head. The cooling liquid can thus be introduced from a cylinder liner or engine block to the cylinder head.

According to an embodiment of the invention, the inlet end of the cooling liquid duct is arranged to open in an area that is configured to be aligned in a mounted state of the cylinder head with an upper end of a cylinder liner for receiving cooling liquid from a cooling liquid channel of the cylinder liner. That allows the cooling liquid to be supplied directly from the cylinder liner into the cylinder head.

According to an embodiment of the invention, the extension of the cylinder head is configured for attachment of a cooling liquid module that is configured to receive cooling liquid from the cooling liquid cavity. A cooling liquid module can thus be arranged on the side of the cylinder head. This is beneficial especially in V-engines, where the cooling liquid module can function as a heat shield below an exhaust manifold.

According to an embodiment of the invention, the exhaust channel comprises a first branch from the first exhaust valve hole and a second branch from the second exhaust valve hole, the first branch and the second branch merging into a common portion passing through the extension of the cylinder head.

According to an embodiment of the invention, the exhaust channel in the extension of the cylinder head is configured to receive an inner sleeve. The inner sleeve can function as a heat shield preventing heat conduction and radiation from the exhaust channel.

According to an embodiment of the invention, the exhaust channel in the extension comprises an outer support portion configured to support an outer end of the inner sleeve and an inner support portion configured to support an inner end of the inner sleeve, and an intermediate portion having a larger diameter than the inner support portion such that a free space is formed between the exhaust channel and the inner sleeve in a mounted state of the inner sleeve. The gap formed around the inner sleeve insulates the exhaust channel from the rest of the cylinder head and helps keeping the exhaust gas temperatures high.

According to an embodiment of the invention, the cylinder head comprises a central hole arranged between the intake and exhaust valve holes and extending from the bottom surface to the top surface.

According to an embodiment of the invention, the central hole is configured to receive a fuel injector or a prechamber assembly. The cylinder head assembly according to the invention comprises a cylinder head defined above and a cooling liquid module attached to the extension of the cylinder head. The cooling liquid module forms a heat shield at least on one side of an exhaust manifold.

The piston engine according to the invention comprises a cylinder head defined above.

Brief description of the drawings

Embodiments of the invention are described below in more detail with reference to the accompanying drawings, in which

Fig. 1 shows a perspective view of a cylinder head according to an embodiment of the invention,

Fig. 2 shows the cylinder head of figure 1 seen from the direction of an extension of the cylinder head,

Fig. 3 shows a cross-sectional view of an extension of the cylinder head of figure 1 ,

Fig. 4 shows a cross-sectional view of a lower part of the cylinder head of figure 1 ,

Fig. 5 shows a cross-sectional view of the cylinder head of figure 1 and components attached to the cylinder head,

Fig. 6 shows a cross-sectional view of a part of the cylinder head of figure 1 and components attached to the cylinder head, and

Fig. 7 shows another cross-sectional view of a part of a cylinder head of figure 1 and components attached to the cylinder head.

Detailed description of embodiments of the invention

Figure 1 shows a cylinder head 1 according to an embodiment of the invention. The cylinder head 1 is a cylinder head of a large piston engine. The expression “large piston engine” refers here to an engine having a cylinder diameter of at least 150 mm. The engine can be, for instance, an engine that is used as a main or an auxiliary engine in a ship or an engine that is used at a power plant for driving a generator for producing electricity. The engine is a multi-cylinder four-stroke engine. The number of cylinders in the engine can be, for instance, 5 to 20. The cylinders can be arranged in-line or in a V-configu ration.

The cylinder head 1 is configured to close an upper end of a cylinder 2 of the engine. Each cylinder 2 of the engine is provided with an own cylinder head 1 . The cylinder head 1 is a one-piece part.

The engine in which the cylinder head 1 is used can be configured to be operable using at least a first, gaseous fuel. The expression “gaseous fuel” refers here to a fuel that is gaseous in atmospheric pressure and at a temperature of 20 °C. The first fuel can be, for instance, natural gas or biogas. The term “biogas” refers here to a gas that mainly consists of methane and which is obtained from renewable sources. The biogas can be produced for example from organic waste. Natural gas could be stored either as a liquefied gas (LNG) or compressed gas (CNG). Biogas could be stored in a similar manner. Instead of methane-based fuels, the first fuel could be, for instance, hydrogen or ammonia or a mixture of two or more types of gaseous fuel.

The engine can be further configured to be operable using a second fuel. The second fuel can be either gaseous fuel or liquid fuel. If the first fuel is natural gas or biogas, the second fuel could be, for instance, hydrogen. Alternatively, the second fuel could be liquid fuel, such as light fuel oil or heavy fuel oil. The engine can also be operable using a third fuel or even further fuels.

The engine can thus be a gas engine, a dual-fuel engine or a multi-fuel engine. However, the engine could also be operable solely using one or more liquid fuels.

The engine can be configured to be operable using mixtures of different fuels. For instance, the engine could be operable using a mixture of hydrogen and some other gaseous fuel and/or a mixture of ammonia and some other gaseous fuel.

When the engine is operated using a gaseous fuel, it can utilize a liquid fuel, such as light fuel oil as a pilot fuel facilitating ignition of the gaseous fuel. However, that is not necessary, but the gaseous fuel could be self-igniting or spark plugs or other ignition means could be used for igniting the gaseous fuel. The cylinder head 1 has a bottom surface 1A configured to delimit an upper end of a main combustion chamber 31 of a cylinder 2, and a top surface 1 B facing an opposite direction than the bottom surface 1A. The cylinders 2 of the engine do not need to be in an upright position, but the cylinders 2 can be inclined from the vertical direction. For instance in a V-engine, the upper ends of the cylinders 2 can be located farther outwards from the longitudinal center line of the engine than the lower ends. The term “bottom surface” thus refers to that side of the cylinder head 1 that is facing the main combustion chamber 31 , but the bottom surface 1 A does not need to be a horizontal surface facing downwards.

The engine comprises an engine block and cylinder liners 19 arranged in the engine block. The cylinders 2 are formed by the cylinder liners 19. The upper end of each cylinder liner 19 extends above the upper surface of the engine block. The cylinder head 1 can be arranged against the upper end of the cylinder liner 19 and attached to the engine block.

The cylinder head 1 is a crossflow cylinder head. The term “crossflow cylinder head” means that the intake and exhaust valves are located on opposite sides of the cylinder head 1 .

The cylinder head 1 has an intake side 11 and an exhaust side 12. When the cylinder head 1 is divided into two halves by an imaginary plane 32, which is in a mounted state of the cylinder head 1 parallel to the axial direction of the cylinder 2, the intake side 11 is that side of the cylinder head 1 on which the intake valves 8 of the cylinder 2 are located, and the exhaust side 12 is that side of the cylinder head 1 on which the exhaust valves 9 of the cylinder 2 are located. The imaginary plane 32 does not need to be in the middle of the cylinder head 1 . In the embodiment of the figures, the imaginary plane 32 dividing the cylinder head 1 into the intake side 11 and the exhaust side 12 is located such that in the mounted state of the cylinder head 1 , the imaginary plane 32 crosses with the longitudinal center axis of the cylinder 2. In a mounted state of the cylinder head 1 , the intake side 11 of the cylinder head 1 is on a first side of the longitudinal center line of a row of cylinders. The exhaust side 12 of the cylinder head 1 is on a second side of said longitudinal center line of said row of cylinders. In an in-line engine, the intake sides 11 of all the cylinder heads 1 of the engine are on the same side of the longitudinal center line of the cylinders. In a V-engine the cylinder heads 1 can be mounted such that the exhaust sides 12 of the cylinder heads 1 of a first bank face the exhaust sides 12 of the cylinder heads 1 of a second bank. The intake sides 11 of the cylinder heads 1 can thus point laterally outwards from the longitudinal center line of the engine.

It is not necessary that the imaginary plane 32 crosses with the longitudinal center axis of the cylinder 2, but the imaginary plane 32 could be offset from the longitudinal center axis of the cylinder 2.

The cylinder head 1 comprises attachment holes 34 for attaching the cylinder head 1 to the engine block. In the embodiment of the figures, the cylinder head

I comprises four attachment holes 34. Each attachment hole 34 is configured to receive a stud bolt for attaching the cylinder head 1 to the engine block. In a mounted state of the cylinder head 1 , the radial distances of the attachment holes 34 from the longitudinal center axis of the cylinder 2 are equal to each other.

The cylinder head 1 comprises an inlet channel 3 arranged on the intake side

I I of the cylinder head 1. The inlet channel 3 is configured for introducing intake air into the main combustion chamber 31 of the cylinder 2. In the embodiment of the figures, the inlet channel 3 is further configured to allow introducing gaseous main fuel into the inlet channel 3 and further into the main combustion chamber 31. The cylinder head 1 further comprises an exhaust channel 4 arranged on the exhaust side 12 of the cylinder head 1 . The exhaust channel 4 is configured for discharging exhaust gas from the main combustion chamber 31 .

The cylinder head 1 comprises a first intake valve hole 5A and a second intake valve hole 5B arranged on the intake side 11 of the cylinder head 1. Each intake valve hole 5A, 5B extends from the bottom surface 1A of the cylinder head 1 to the top surface 1 B and is configured to receive an intake valve 8. The cylinder head 1 can thus be provided with two intake valves 8.

The cylinder head 1 comprises a first exhaust valve hole 6A and a second exhaust valve hole 6B arranged on the exhaust side 12 of the cylinder. Each exhaust valve hole 6A, 6B extends from the bottom surface 1A to the top surface 1 B and is configured to receive an exhaust valve 9. The cylinder head 1 can thus be provided with two exhaust valves 9. In the embodiment of the figures, the cylinder head 1 further comprises a central hole 29 arranged between the intake and exhaust valve holes 5A, 5B, 6A, 6B and extending from the bottom surface 1 A of the cylinder head 1 to the top surface 1 B. In the embodiment of the figures, the central hole 29 is configured to receive a fuel injector 30. The fuel injector 30 is configured to inject liquid pilot fuel into the main combustion chamber 31 . However, the central hole 29 could also be configured to receive a prechamber assembly.

The cylinder head 1 further comprises an integral extension 13 that is formed on the exhaust side 12. In the embodiment of the figures, the cylinder head 1 extends on the exhaust side 12 farther form the area that is configured to cover the cylinder 2 in a mounted state of the cylinder head 1 than on the intake side 11.

The extension 13 comprises a first push rod passage 14A and a second push rod passage 14B. Each of the push rod passages 14A, 14B is configured to allow through passage of a push rod 15. Push rods 15 can thus be inserted through the push rod passages 14A, 14B. In a mounted state of the cylinder head 1 , the push rods 15 can be operated by means of a camshaft that is located below the level of the bottom surface 1 A of the cylinder head 1 . The push rods 15 can operate valve actuating mechanism that is located at least partly above the level of the top surface 1 B of the cylinder head 1 . In a mounted state of the cylinder head 1 , the push rod passages 14A, 14B are located farther from the longitudinal center axis of the cylinder 2 than the attachment holes 34.

One of the push rods 15 is configured to operate the intake valves 8 of the cylinder 2 and one of the push rods 15 is configured to operate the exhaust valves 9 of the cylinder 2. The push rods 15 are lifted by means of the cams of a camshaft. If the cylinder head 1 is used in a V-engine, cams for the cylinders 2 of both banks of the engine can be arranged in the same camshaft. The push-rods are spring-biased against the cams. The push-rod passages 14A, 14B collect lubricating oil from the valve actuating mechanism above the cylinder head 1 and conduct it past the exhaust channel 4.

The exhaust channel 4 is arranged to pass in the extension 13 between the first push rod passage 14A and the second push rod passage 14B. The exhaust channel 4 opens to the side of the cylinder head 1 in the extension 13. The extension 13 is configured to allow an exhaust manifold 43 to be attached to the extension 13 and in fluid communication with the exhaust channel 4. The push rod passages 14A, 14B are thus arranged on the sides of the exhaust channel 4, forming heat shields on the sides of the exhaust channel 4. This reduces heat radiation and conduction from the exhaust channel 4 to the outside of the cylinder head 1. The extension 13 is provided with threaded holes 35 for allowing the exhaust manifold 43 to be attached to the extension 13 by means of screws 36.

An exhaust manifold 43 can be seen in figures 5-7. The exhaust manifold 43 comprises a longitudinal portion 45. The axial direction of the longitudinal portion 45 is parallel to the longitudinal direction of the row of cylinders. The exhaust manifold 43 further comprises a plurality of branches 46 connecting the longitudinal portion 45 to the exhaust channels 4 of the cylinder heads 1 . The number of branches 46 in the exhaust manifold 43 equals the number of cylinders 2 to which the exhaust manifold 43 is connected. An in-line engine can comprise a single exhaust manifold. A V-engine can be provided with a separate exhaust manifold for each cylinder bank. Each branch 46 of the exhaust manifold comprises a mounting flange 53 for attaching the branch 46 to the extension 13 of the cylinder head 1 .

The exhaust channel 4 comprises a first branch 4A from the first exhaust valve hole 6A and a second branch 4B from the second exhaust valve hole 6B. The first branch 4 and the second branch 4B merge into a common portion 4C that passes through the extension 13 of the cylinder head 1 . The exhaust channel 4 is merged into the common portion 4C before the push rod passages 14A, 14B.

The cylinder head 1 comprises a cooling liquid cavity 16. The cooling liquid cavity 16 is configured to receive and discharge cooling liquid to allow circulation of cooling liquid in the cylinder head 1 . In the embodiment of the figures, the cooling liquid is received from a cooling liquid duct 20 of the cylinder liner 19 and discharged from the extension 13 of the cylinder head 1 . In the embodiment of the figures, the cooling liquid cavity 16 is arranged partly in the extension 13.

The cooling liquid cavity 16 comprises a lower portion 16A and upper portion 16B. The lower portion 16A is arranged below the exhaust channel 4, i.e. on the bottom surface side of the exhaust channel 4. The upper portion 16B is arranged above the exhaust channel 4, i.e. on the top surface side of the exhaust channel 4. In the embodiment of the figures, the upper portion 16B connects to the lower portion 16A on the sides of the exhaust channel 4.

The cylinder head 1 comprises a cooling liquid duct 17 for introducing cooling liquid into the cooling liquid cavity 16. In the embodiment of the figures, the cooling liquid duct 17 comprises a first branch 17A for introducing cooling liquid into the lower portion 16A of the cooling liquid cavity 16 and a second branch 17B for introducing cooling liquid into the upper portion 16B of the cooling liquid cavity 16. The cooling liquid duct 17 has an inlet end 18 opening onto the bottom surface 1A of the cylinder head 1 . The inlet end 18 of the cooling liquid duct 17 is arranged to open in an area that is configured to be aligned in a mounted state of the cylinder head 1 with an upper end of the cylinder liner 19 for receiving cooling liquid from the cooling liquid channel 20 of the cylinder liner 19.

The second branch 17B of the cooling liquid duct 17 comprises a portion extending in the direction of the central hole 29 of the cylinder head 1 . Said portion is arranged between the central hole 29 and the exhaust channel 4 such that said portion is located closer to the central hole 29 than the exhaust channel 4. That helps avoiding excessive cooling of the exhaust gas.

The cylinder head 1 comprises at least one cooling liquid outlet 21 , 22A, 22B that is arranged in the extension 13 of the cylinder head 1 for discharging cooling liquid from the cooling liquid cavity 16. In the embodiment of the figures, the cylinder head 1 comprises three cooling liquid outlets 21 , 22A, 22B. A first cooling liquid outlet 21 is arranged below the exhaust channel 4. The first cooling liquid outlet 21 is configured to discharge cooling liquid from the lower portion 16A of the cooling liquid cavity 16. The cylinder head 1 further comprises a second cooling liquid outlet 22A and a third cooling liquid outlet 22B. The second and third cooling liquid outlets 22A, 22B are configured to discharge cooling liquid from the upper portion 16B of the cooling liquid cavity 16.

The extension 13 of the cylinder head 1 is configured for attachment of a cooling liquid module 23 that is configured to receive cooling liquid from the cooling liquid cavity 16. The cooling liquid module 23 is arranged to receive cooling liquid via the cooling liquid outlets 21 , 22A, 22B of the cylinder head 1. The cooling liquid module 4323 forms a heat shield below the exhaust manifold 43. The cooling liquid module 23 comprises a lower portion 23A and an upper portion 23D. The lower portion 23A of the cooling liquid module 23 is arranged to receive cooling liquid via the first cooling liquid outlet 21 of the cylinder head 1 and the upper portion 23D is arranged to receive cooling liquid via the second and third cooling liquid outlets 22A, 22B of the cylinder head 1 . The lower portion 23A and the upper portion 23D of the cooling liquid module 23 are arranged in fluid communication with each other via side portions of the cooling liquid module 23.

In the embodiment of the figures, the lower portion 23A of the cooling liquid module 23 comprises a cooling liquid inlet 50 that is arranged to receive cooling liquid from the cooling liquid cavity 16 of the cylinder head 1. The lower portion 23A of the cooling liquid module 23 can be connected to the lower portion 16A of the cooling liquid cavity 16 of the cylinder head 1. The upper portion 23D of the cooling liquid module 23 comprises two cooling liquid inlets 51 arranged to receive cooling liquid from the cylinder head 1 . The upper portion 23D of the cooling liquid module 23 can be connected to the upper portion 16B of the cooling liquid cavity 16 of the cylinder head 1 .

The lower portion 23A of the cooling liquid module 23 has an end surface 54 that is located away from the cylinder head 1 . The mutual angle between the end surface 54 and the axial direction of the respective cylinder 1 is preferably 15 to 40 degrees, the upper edge of the end surface 54 being located farther from the cylinder 2 than the lower edge. This allows the same cooling liquid modules 23 to be used both in V-engines and in-line engines. The angle is preferably substantially equal to the inclination angle of the cylinders 2 of a V- engine from the vertical direction. In an in-line engine, the end surface 54 can be used as an attachment point for a heat insulation cover surrounding the exhaust manifold 43.

The exhaust channel 4 in the extension 13 of the cylinder head 1 is configured to receive an inner sleeve 24. In the embodiment of the figures, the exhaust channel 4 in the extension 13 comprises an outer support portion 25 configured to support an outer end of the inner sleeve 24 and an inner support portion 26 configured to support an inner end of the inner sleeve 24. The exhaust channel 4 further comprises an intermediate portion 27 having a larger diameter than the inner support portion 26 such that a free space 28 is formed between the exhaust channel 4 and the inner sleeve 24 in a mounted state of the inner sleeve 24. In the embodiment of the figures, the outer diameter of the inner sleeve 24 is constant. The inner diameter of the inner support portion 26 is substantially the same as the inner diameter of the outer support portion 25. However, the inner diameter of the outer support portion 25 could be greater than the inner diameter of the inner support portion 26. In that case, the diameter of the inner sleeve 24 could increase towards the outer end, or an intermediate piece could be arranged between the inner sleeve 24 and the outer support portion 25. The exhaust gas flows in the inner sleeve 24. The inner sleeve and the free space 28 around the inner sleeve 24 reduces heat radiation and conduction from the exhaust channel 4.

It will be appreciated by a person skilled in the art that the invention is not limited to the embodiments described above, but may vary within the scope of the appended claims.