Pre-chamber, cylinder head and piston engine

Abstract

A pre-chamber (4) for a cylinder (1) of a piston engine comprises a combustion portion (5) for receiving a mixture of air and fuel to ignite the mixture and a nozzle portion (6) for establishing fluid communication between the combustion portion (5) and a main combustion chamber (7) of the engine, the nozzle portion (6) comprising a nozzle opening (6a) configured to allow flow from the main combustion chamber (7) into the pre-chamber (4) and flow from the pre-chamber (4) into the main combustion chamber (7). The pre-chamber (4) comprises at least one auxiliary passage (9) having a first end (9a) opening into the nozzle portion (6) within the pre-chamber (4) and a second end (9b) opening outside the pre-chamber (4), the auxiliary passage (9) being configured such that flow from the main combustion chamber (7) into the pre-chamber (4) during a compression stroke and flow from the pre-chamber (4) into the main combustion chamber (7) during a combustion stroke causes fluid to flow through the auxiliary passage (9) into the nozzle portion (6).

Description

TECHNICAL FIELD

[0001] The present invention relates to a pre-chamber for a cylinder of a piston engine. The invention also relates to a cylinder head and a piston engine. BACKGROUND

[0002] Internal combustion engines can be provided with a pre-chamber, also called a pre-combustion chamber. In a pre-chamber engine, each cylinder is provided with a pre-chamber and part of the fuel is introduced into the pre-chamber. Depending on the engine, the fuel can be self-igniting or a spark plug or some other device can be used to ignite the fuel. Thus, the combustion is initiated in the pre-chamber, but the main part of the combustion takes place in the cylinder outside the pre-chamber. The pre-chamber construction is particularly advantageous in lean burn engines, where part of the fuel is introduced into the pre-chamber and part of the fuel is mixed with air before the intake valve. Such an arrangement can be used for example in a spark-ignited gas engine. The gas-air mixture in the pre-chamber is rich compared to the mixture in the cylinder. The rich mixture in the pre-chamber is ignited by a spark plug and the flame from the pre-chamber ignites the mixture in the cylinder.

[0003] A common problem in pre-chamber engines is insufficient mixing of air and fuel, which leads to incomplete combustion. Another problem encountered in pre-chamber engines is excessive thermal loading of the pre-chamber components. SUMMARY

[0004] It is an object of the present invention to provide an improved pre-chamber for a cylinder of a piston engine, which pre-chamber comprises a combustion portion configured to receive a mixture of air and fuel to ignite the mixture and a nozzle portion configured to establish fluid communication between the combustion portion of the pre-chamber and a main combustion chamber of the engine, the nozzle portion comprising at least one nozzle opening configured to allow flow from the main combustion chamber into the pre-chamber and flow from the pre-chamber into the main combustion chamber. It is a further object of the present invention to provide an improved cylinder head and an improved piston engine.

[0005] According to the invention, the pre-chamber comprises at least one auxiliary passage having a first end opening into the nozzle portion within the pre-chamber and a second end opening outside the pre-chamber, the auxiliary passage being configured to cause fluid flow through the auxiliary passage into the nozzle portion of the pre-chamber from the main combustion chamber into the pre-chamber during the compression stroke and from the pre-chamber into the main combustion chamber during the combustion stroke.

[0006] Due to the auxiliary passage, fluid flow is drawn into the nozzle portion both during the compression stroke and during the combustion stroke. During the compression stroke, the flow improves the mixing within the pre-chamber. During the combustion stroke, the flow cools the pre-chamber. It also lifts the flame out of the pre-chamber through the at least one nozzle opening.

[0007] According to an embodiment of the invention, the cross-sectional area of the auxiliary channel is smaller than the cross-sectional area of the at least one nozzle opening. Advantageously, the cross-sectional area of the auxiliary channel is at most 30% of the cross-sectional area of the nozzle opening. The smaller cross-sectional area contributes to the situation that fluid is sucked into the nozzle portion via the auxiliary channel.

[0008] According to an embodiment of the invention, the second end of the auxiliary channel opens onto the outer surface of the nozzle portion. This allows the length of the auxiliary channel to be short.

[0009] According to an embodiment of the invention, the second end of the auxiliary channel opens into the main combustion chamber in the mounted state of the pre-chamber. During the compression stroke, the mixture of air and fuel from the main combustion chamber is thus sucked into the nozzle portion via the auxiliary channel. The fuel concentration in the nozzle portion is thus not significantly changed, but the mixing is improved. During the combustion stroke, the cooler mixture from the main combustion chamber effectively cools the nozzle portion.

[0010] According to an embodiment of the invention, the auxiliary channel comprises a portion that, starting from the first end and in the mounted state of the pre-chamber, slopes upward from the lateral direction of the cylinder. This contributes to the situation that fluid is sucked into the nozzle portion via the auxiliary channel, in particular during the combustion stroke.

[0011] According to an embodiment of the invention, the first end of the auxiliary channel is above the level of the upper edge of the at least one nozzle opening in the longitudinal direction of the cylinder in the mounted state of the pre-chamber.

[0012] According to an embodiment of the invention, the pre-chamber comprises a plurality of nozzle openings, and the first end of the auxiliary channel is located between two nozzle openings.

[0013] According to an embodiment of the invention, the auxiliary channel is curved.

[0014] According to an embodiment of the invention, the shape of the auxiliary channel opens towards the nozzle portion end of the pre-chamber. This causes a portion of the auxiliary channel to slope upward and still have a second end that opens into the main combustion chamber.

[0015] According to an embodiment of the invention, the auxiliary channel is straight, and the first end of the auxiliary channel is closer to the nozzle portion end of the pre-chamber than the second end. A pre-chamber with a straight auxiliary channel is simpler to manufacture than a pre-chamber with a more complex-shaped auxiliary channel.

[0016] According to an embodiment of the invention, the pre-chamber comprises several auxiliary channels. This allows more fluid to flow into the nozzle portion via the auxiliary channels.

[0017] A cylinder head according to the invention is provided with the above-described pre-chamber.

[0018] A piston engine according to the invention comprises the above-described pre-chamber. Attached Figure Description

[0019] Embodiments of the present invention will now be described in more detail with reference to the accompanying drawings, wherein:

[0020] Figure 1 A schematic cross-sectional view of a cylinder and a portion of the cylinder head of a piston engine is shown.

[0021] Figure 2 A cross-sectional view of a pre-combustion chamber according to an embodiment of the present invention is shown; and

[0022] Figure 3 A cross-sectional view of the pre-combustion chamber according to another embodiment of the present invention is shown. Detailed Implementation

[0023] exist Figure 1 The image shows the cylinder head 8 of a piston engine. The engine is a large internal combustion engine, such as a main or auxiliary engine in a ship, or an engine used for power generation in a power plant. The engine has several cylinders 1. Each cylinder 1 of the engine has a cylinder head 8 that closes the upper end of the cylinder 1. The term "upper end" here refers to the end of the cylinder 1 away from the crankshaft. The cylinders 1 do not necessarily have to be vertically arranged, but they can be at other angles relative to the bottom of the engine. A main combustion chamber 7 is formed within the cylinder 1 between the cylinder head 8 and the piston 2, which is arranged to move in a reciprocating motion within the cylinder 1. The walls of the cylinder 1 are formed by cylinder liners. The main combustion chamber 7 is in fluid communication with a pre-combustion chamber 4. Therefore, intake air or a mixture of intake air and fuel, residual gases from combustion, and possible recirculated exhaust gases can flow from the main combustion chamber 7 into the pre-combustion chamber 4. Fluid is also allowed to flow from the pre-combustion chamber 4 into the main combustion chamber 7. Figure 1 In this embodiment, the pre-combustion chamber 4 is concentric with the main combustion chamber 7. However, the position of the pre-combustion chamber 4 may also be different.

[0024] exist Figure 1 In this embodiment, the engine is a spark-ignition gas engine, wherein a portion of the gaseous fuel is introduced into the intake manifold to form a lean air / fuel mixture, and a portion of the fuel is introduced into the pre-combustion chamber 4 to form a rich mixture, which is ignited by a spark plug (not shown). The leaner mixture in the main combustion chamber 7 is ignited by the combustion of the richer mixture formed in the pre-combustion chamber 4. The pre-combustion chamber 4 is provided with a fuel inlet for introducing fuel into the pre-combustion chamber 4. The pre-combustion chamber 4 is provided with a spark plug.

[0025] The pre-chamber 4 comprises a combustion portion 5 and a nozzle portion 6. The combustion portion 5 is configured to receive a mixture of fuel and air to ignite the mixture. The nozzle portion 6 is configured to connect the combustion portion 5 of the pre-chamber 4 to the main combustion chamber 7. In the embodiment of the figures, the nozzle portion 6 comprises a plurality of nozzle openings 6a. The nozzle openings 6a are configured to allow a flow from the main combustion chamber 7 into the pre-chamber 4 and from the pre-chamber 4 into the main combustion chamber 7. The nozzle portion 6 can also be provided with a single nozzle opening.

[0026] The nozzle portion 6 has a smaller volume than the combustion portion 5. The nozzle portion 6 forms an elongated passage extending from the combustion portion 5 of the pre-chamber 4 to the main combustion chamber 7. The cross-sectional area of the nozzle portion 6, seen in the longitudinal direction of the nozzle portion 6, is smaller than the cross-sectional area of the combustion portion 5, seen in the same direction.

[0027] In the embodiment of the figures, the axial direction of the nozzle portion 6 is parallel to the axial direction of the cylinder 1. However, the nozzle portion 6 can also be inclined with respect to the axial direction of the cylinder 1.

[0028] During the compression stroke, a mixture of fuel and air flows via the nozzle openings 6a into the nozzle portion 6 of the pre-chamber 4 and further into the combustion portion 5 of the pre-chamber 4. Additional fuel is directly introduced into the combustion portion 5. A richer fuel / air mixture is thus formed in the combustion portion 5. The mixture is ignited by the spark plug. After ignition, the ignited mixture and combustion products flow from the combustion portion 5 via the nozzle portion 6 and the nozzle openings 6a into the main combustion chamber 7.

[0029] In the embodiment of the figures, the pre-chamber 4 is formed by a main part and a nozzle part. The nozzle portion 6 is formed by the nozzle part and the combustion portion 5 is mainly formed by the main part. The combustion portion 5 is partially delimited by the nozzle part. The pre-chamber 4 can also be formed by a single part. Alternatively, it can be formed by several parts.

[0030] The pre-chamber 4 according to the invention comprises at least one auxiliary passage 9. The auxiliary passage 9 has a first end 9a and a second end 9b. The first end 9a opens into the nozzle portion 6 within the pre-chamber 4. The first end 9a is positioned close to the nozzle openings 6a. The first end 9a is located in the half of the nozzle portion 6 that is farthest away from the combustion portion 5 of the pre-chamber 4. Preferably, the first end 9a is located in the third of the nozzle portion 6 that is farthest away from the combustion portion 5.

[0031] The second end 9b opens out of the pre-chamber 4. The auxiliary passage 9 is configured such that flow between the pre-chamber 4 and the main combustion chamber 7 causes fluid flow through the auxiliary passage 9 into the nozzle portion 6 of the pre-chamber 4. During the compression stroke, flow from the main combustion chamber 7 through the nozzle opening 6a into the nozzle portion 6 and further into the combustion portion 5 causes flow from outside the pre-chamber 4 into the nozzle portion 6 via the auxiliary passage 9. During the combustion stroke, flow from the combustion portion 5 into the main combustion chamber 7 via the nozzle portion 6 and the nozzle opening 6a causes flow from outside the pre-chamber 4 into the nozzle portion 6 via the auxiliary passage 9.

[0032] During the compression stroke, flow through the auxiliary passage 9 into the nozzle portion 6 promotes mixing of the air and fuel mixture flowing into the pre-chamber 4. During the combustion stroke, flow through the auxiliary passage 9 into the nozzle portion 6 cools the pre-chamber 4, in particular the nozzle portion 6 of the pre-chamber 4. The flow can also promote the flame exiting via the nozzle opening 6a.

[0033] Flow through the auxiliary passage 9 into the nozzle portion 6 of the pre-chamber 4 is achieved due to the Venturi effect. When fluid flows from the combustion portion 5 of the pre-chamber 4 or from the main combustion chamber 7 into the nozzle portion 6, which has a smaller cross-sectional area, the fluid velocity increases. The increased fluid velocity reduces the static pressure in the nozzle portion 6, which causes suction into the nozzle portion 6 via the auxiliary passage 9.

[0034] The cross-sectional area of the auxiliary passage 9 is smaller than the cross-sectional area of any nozzle opening 6a. The cross-sectional area of the auxiliary passage 9 can be, for example, at most 30% of the cross-sectional area of a single nozzle opening 6a. The smaller diameter of the auxiliary passage 9 helps to create the Venturi effect.

[0035] In the embodiment of the figures, the second end 9b of the auxiliary passage 9 opens onto the outer surface of the nozzle portion 6 of the pre-chamber 4. This minimises the required length of the auxiliary passage 9. In the embodiment of the figures, the second end 9b of the auxiliary passage 9 opens into the main combustion chamber 7. In the embodiment of the figures, the second end 9b of the auxiliary passage 9 opens into a gap between the nozzle portion 6 of the pre-chamber 4 and the cylinder head 8. In both embodiments, fluid from the main combustion chamber 7 flows into the auxiliary passage 9. Thus, during the compression stroke, the fuel concentration of the flow through the auxiliary passage 9 is not significantly different from the fuel concentration of the flow through the nozzle opening 6a. Thus, the fuel concentration in the pre-chamber 4 is substantially unaffected by the flow through the auxiliary passage 9, and mixing in the nozzle portion 6 is improved. During the combustion stroke, cooler fluid from the main combustion chamber 7 flows into the nozzle portion 6, so the nozzle portion 6 is effectively cooled. Figure 2 Figure 3 In the embodiment of the figures, the second end 9b of the auxiliary passage 9 opens onto the outer surface of the nozzle portion 6 of the pre-chamber 4. This minimises the required length of the auxiliary passage 9. In the embodiment of the figures, the second end 9b of the auxiliary passage 9 opens into the main combustion chamber 7. In the embodiment of the figures, the second end 9b of the auxiliary passage 9 opens into a gap between the nozzle portion 6 of the pre-chamber 4 and the cylinder head 8. In both embodiments, fluid from the main combustion chamber 7 flows into the auxiliary passage 9. Thus, during the compression stroke, the fuel concentration of the flow through the auxiliary passage 9 is not significantly different from the fuel concentration of the flow through the nozzle opening 6a. Thus, the fuel concentration in the pre-chamber 4 is substantially unaffected by the flow through the auxiliary passage 9, and mixing in the nozzle portion 6 is improved. During the combustion stroke, cooler fluid from the main combustion chamber 7 flows into the nozzle portion 6, so the nozzle portion 6 is effectively cooled.

[0036] ​In the embodiment shown in the accompanying drawings, the auxiliary channel 9 includes a portion starting from a first end 9a of the auxiliary channel 9, which slopes laterally upward from the cylinder 1 in the pre-combustion chamber 4 mounting state. Figure 3 In this embodiment, the entire auxiliary channel 9 is tilted upwards. Figure 2 In this embodiment, only a portion of the auxiliary channel 9 is inclined upwards. During the combustion stroke, the inclined portion helps prevent fluid from being discharged from the nozzle portion 6 via the auxiliary channel 9.

[0037] exist Figure 2 In this embodiment, the auxiliary channel 9 is curved. The shape of the auxiliary channel 9 opens towards the nozzle portion end of the pre-combustion chamber 4. Therefore, the highest point of the auxiliary channel 9 is located between the ends of the auxiliary channel 9. The curved shape of the auxiliary channel 9 allows a portion of the auxiliary channel 9 to tilt upwards, while allowing the second end 9b of the auxiliary channel 9 to be positioned in the main combustion chamber 7.

[0038] exist Figure 3 In this embodiment, the auxiliary channel 9 is straight, and the first end 9a of the auxiliary channel 9 is closer to the nozzle portion end of the pre-combustion chamber 4 than the second end 9b. A pre-combustion chamber 4 with a straight auxiliary channel 9 is simpler to manufacture than a pre-combustion chamber 4 with a curved auxiliary channel 9.

[0039] In the embodiment shown in the accompanying drawings, the first end 9a of the auxiliary channel 9, in the pre-combustion chamber 4 installation state, is located at the height above the upper edge of the nozzle opening 6a along the longitudinal direction of the cylinder 1. Alternatively, the first end 9a of the auxiliary channel 9 may be located between the two nozzle openings 6a.

[0040] In the embodiment shown in the accompanying drawings, the pre-combustion chamber 4 includes several auxiliary channels 9. By providing several auxiliary channels 9 to the pre-combustion chamber 4, a higher flow rate through the auxiliary channels 9 can be achieved.

[0041] The pre-combustion chamber 4, or at least the nozzle portion 6 of the pre-combustion chamber 4, can be manufactured using additive manufacturing. Additive manufacturing allows for complex shapes of the auxiliary channel 9. However, particularly in the case of a straight auxiliary channel 9, the pre-combustion chamber 4 can also be made using other manufacturing methods. For example, the auxiliary channel 9 can be drilled.

[0042] Those skilled in the art will understand that the present invention is not limited to the above embodiments, but can be varied within the scope of the appended claims.

Claims

1. A pre-combustion chamber (4) for a cylinder (1) of a piston engine, the pre-combustion chamber (4) comprising a combustion section (5), a nozzle section (6), and at least one auxiliary passage (9), the combustion section being configured to receive an air-fuel mixture for ignition, the nozzle section being configured to establish fluid communication between the combustion section (5) of the pre-combustion chamber (4) and a main combustion chamber (7) of the engine, the nozzle section (6) comprising at least one nozzle opening (6a) configured to allow flow from the main combustion chamber (7) to the pre-combustion chamber (4) and from the pre-combustion chamber (4) to the main combustion chamber (7). The auxiliary channel has a first end (9a) and a second end (9b) in the pre-combustion chamber (4) leading to the nozzle portion (6) and the cross-sectional area of ​​the auxiliary channel (9) is smaller than the cross-sectional area of ​​the at least one nozzle opening (6a). The nozzle portion (6) has a smaller volume than the combustion portion (5) and forms an elongated channel extending from the combustion portion (5) of the pre-combustion chamber (4) to the main combustion chamber (7). The cross-sectional area of ​​the nozzle portion (6) viewed longitudinally is smaller than the cross-sectional area of ​​the combustion portion (5) viewed in the same direction. The second end (9b) of the auxiliary channel (9) opens outside the pre-combustion chamber (4). The auxiliary channel (9) is configured such that during the compression stroke, the flow from the main combustion chamber (7) through the at least one nozzle opening (6a) into the pre-combustion chamber (4) and during the combustion stroke, the flow from the pre-combustion chamber (4) through the at least one nozzle opening (6a) into the main combustion chamber (7) causes fluid to flow through the auxiliary channel (9) into the nozzle portion (6) of the pre-combustion chamber (4).

2. The pre-combustion chamber (4) according to claim 1, wherein, The cross-sectional area of ​​the auxiliary channel (9) is at most 30% of the cross-sectional area of ​​the nozzle opening (6a).

3. The pre-combustion chamber (4) according to claim 1 or 2, wherein, The second end (9b) of the auxiliary channel (9) opens onto the outer surface of the nozzle portion (6).

4. The pre-combustion chamber (4) according to claim 1 or 2, wherein, The second end (9b) of the auxiliary channel (9) leads to the main combustion chamber (7) in the installed state of the pre-combustion chamber (4).

5. The pre-combustion chamber (4) according to claim 1 or 2, wherein, The auxiliary channel (9) includes a portion that starts from the first end (9a) and slopes laterally upward from the cylinder (1) in the installed state of the pre-combustion chamber (4).

6. The pre-combustion chamber (4) according to claim 1 or 2, wherein, The first end (9a) of the auxiliary channel (9) is located above the height of the upper edge of the at least one nozzle opening (6a) along the longitudinal direction of the cylinder (1) in the installed state of the pre-combustion chamber (4).

7. The pre-combustion chamber (4) according to claim 1 or 2, wherein, The pre-combustion chamber (4) includes several nozzle openings (6a), and the first end (9a) of the auxiliary channel (9) is located between two nozzle openings (6a).

8. The pre-combustion chamber (4) according to claim 1 or 2, wherein, The auxiliary channel (9) is curved.

9. The pre-combustion chamber (4) according to claim 8, wherein, The auxiliary channel (9) is shaped to open toward the end of the nozzle portion of the pre-combustion chamber (4).

10. The pre-combustion chamber (4) according to claim 1 or 2, wherein, The auxiliary channel (9) is straight, and the first end (9a) of the auxiliary channel (9) is closer to the nozzle portion end of the pre-combustion chamber (4) than the second end (9b).

11. The pre-combustion chamber (4) according to claim 1 or 2, wherein, The pre-combustion chamber (4) includes several auxiliary channels (9).

12. A cylinder head (8) for a piston engine, wherein, The cylinder head (8) is provided with a pre-combustion chamber (4) according to any one of claims 1 to 11.

13. A piston engine comprising a pre-combustion chamber according to any one of claims 1 to 11.

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