Piston, internal combustion engine, and vehicle

Abstract

A piston (1) for an internal combustion engine (4) is disclosed. The piston (1) is configured to reciprocate along a central axis (ca) of the piston (1) during operation in the engine (4). The piston (1) includes a number of fuel guide surfaces (3) arranged at a distance (d) from a top surface (5) of the piston (1) measured along the central axis (ca). Each fuel guide surface (3) is configured to guide a fuel spray (12) injected onto the fuel guide surface (3). The fuel guide surfaces (3) are arranged to have a gap (7) between two adjacent fuel guide surfaces (3). The present disclosure also relates to an engine (4) including the piston (1) and a vehicle (2) including the internal combustion engine (4).

Description

Technical Field

[0001] The present disclosure relates to a piston for an internal combustion engine. The present disclosure further relates to an internal combustion engine comprising a cylinder and a piston configured to reciprocate in the cylinder. Furthermore, the present disclosure relates to a vehicle comprising the internal combustion engine. Background Art

[0002] An internal combustion engine, such as a four-stroke internal combustion engine, includes one or more cylinders and a piston arranged in each cylinder. The piston is connected to the engine's crankshaft and is arranged to reciprocate within the cylinder as the crankshaft rotates. The engine typically also includes one or more inlet and outlet valves and one or more fuel supply devices. The one or more inlet and outlet valves are controlled by corresponding valve control devices, which typically include one or more camshafts rotatably connected to the engine's crankshaft via a belt, chain, gears, or similar device. A four-stroke internal combustion engine completes four separate strokes as the crankshaft rotates. A stroke is the complete travel of the piston along the cylinder in either direction. The uppermost position of the piston in the cylinder is typically referred to as top dead center (TDC), while the lowermost position of the piston in the cylinder is typically referred to as bottom dead center (BDC). The strokes occur in the following order: intake stroke, compression stroke, expansion stroke, and exhaust stroke.

[0003] Compression-ignition engines, such as diesel engines, include a fuel injector in each cylinder of the engine. Furthermore, many modern spark-ignition engines, such as gasoline engines, also include a fuel injector in each cylinder of the engine. These types of engines are often referred to as direct-injection engines. A fuel injector typically includes a number of orifices and a needle configured to control the flow of fuel through the orifices. The fuel injector is typically controlled to inject fuel into the cylinder toward the end of the compression stroke of the cylinder in question. When fuel is injected into the cylinder through the orifices, a slightly conical fuel spray is formed in the cylinder.

[0004] Fuel consumption is a major concern for internal combustion engines. Two ways to improve an engine's fuel efficiency are to reduce heat transfer to the combustion chamber walls and to increase combustion heat release. Combustion heat release is a measure of the burn rate (i.e., the rate at which the fuel is burning) and can be improved by improving the mixing ratio between air and fuel. Heat transfer to the combustion chamber walls and combustion heat release are generally conflicting requirements. That is, when combustion heat release is increased, heat transfer to the combustion chamber walls generally increases, and vice versa.

[0005] Furthermore, when a fuel spray is injected into a cylinder, a stoichiometric region forms around the fuel spray. Within this region, the fuel and air are in a stoichiometric ratio. This region is sometimes referred to as the stoichiometric surface area of ​​the fuel spray. Stoichiometric combustion is beneficial for engine heat release and fuel efficiency. However, the engine's fuel nozzles and combustion chamber impose limitations on the size of this stoichiometric surface area. Summary of the Invention

[0006] It is an object of the present invention to overcome or at least alleviate at least some of the above mentioned problems and disadvantages.

[0007] According to a first aspect of the present invention, this object is achieved by a piston for an internal combustion engine. The piston is configured to reciprocate along a central axis of the piston during operation in the engine. The piston includes a number of fuel guide surfaces arranged at a distance from a top surface of the piston measured along the central axis. Each fuel guide surface is configured to guide a fuel spray injected onto the fuel guide surface. The fuel guide surfaces are arranged with a gap between two adjacent fuel guide surfaces.

[0008] Because the fuel guide surfaces are arranged with a gap between two adjacent fuel guide surfaces, air can flow through the gap and enter the fuel spray guided by the fuel guide surfaces. This improves the mixing ratio between air and fuel. Thus, the provided piston is suitable for improving combustion heat release without significantly affecting heat transfer to the combustion chamber walls. Therefore, the provided piston is suitable for improving the fuel efficiency of the engine.

[0009] Furthermore, because each fuel guide surface is configured to guide the fuel spray injected onto it, each fuel spray has a flatter cross-section after being guided by the fuel guide surface. That is, when fuel is freely injected into the cylinder through the injector's orifice, a slightly conical fuel spray forms in the cylinder. A conical fuel spray has a circular cross-section perpendicular to the injection direction. However, because each fuel guide surface is configured to guide the fuel spray injected onto it, a flatter fuel spray is formed after the impact between the fuel spray and the corresponding fuel guide surface. Compared to a conical fuel spray, a flat fuel spray has a more elliptical cross-section perpendicular to the injection direction. Therefore, a flat fuel spray has a larger surface-to-volume ratio than a conical fuel spray, providing more surface area for mixing air and fuel. Consequently, a flat fuel spray has a larger stoichiometric surface area than a conical fuel spray. As a result, the provided piston is suitable for improving combustion heat release without significantly affecting heat transfer to the combustion chamber walls. Therefore, the provided piston is suitable for improving engine fuel efficiency.

[0010] Thus, a piston is provided which overcomes or at least alleviates at least some of the above mentioned problems and disadvantages.Thus, the above mentioned objects are achieved.

[0011] Optionally, each fuel guide surface includes a trailing edge, and a gap is formed circumferentially between the trailing edges of two adjacent fuel guide surfaces. Thus, a piston is provided that allows air to efficiently flow into the fuel spray via the gap between the trailing edges of the fuel guide surfaces. Thus, a piston is provided that provides conditions for improving combustion heat release without significantly affecting heat transfer to the walls of the combustion chamber.

[0012] Optionally, the piston includes a piston bowl, wherein a number of fuel-directing surfaces are arranged in the piston bowl. Thus, the provided piston is capable of directing a fuel spray into the piston bowl. Thus, the provided piston provides conditions for improving combustion heat release without significantly affecting heat transfer to the walls of the combustion chamber.

[0013] Optionally, a certain number of fuel guide surfaces are distributed around the central axis of the piston. This provides a piston capable of guiding the fuel spray into the combustion chamber in a uniform and well-distributed manner. This provides conditions for improving the air / fuel mixing ratio and, therefore, combustion heat release. Furthermore, a relatively short distance between the injector orifice and the fuel guide surfaces is provided. This provides conditions for reducing interaction between the flame and the combustion chamber walls, and, therefore, heat transfer to the combustion chamber walls.

[0014] Optionally, the piston includes a central projection projecting from the top surface of the piston at a position between a number of the fuel directing surfaces. Thus, a piston is provided that can achieve a high compression ratio in the cylinder and / or provide for a larger piston bowl without reducing the compression ratio in the cylinder.

[0015] Optionally, the central projection is conical or frusto-conical. This provides an efficient structure capable of achieving a high compression ratio in the cylinder while allowing the fuel spray to be positioned adjacent to the sides of the central projection. This allows the available space in the combustion chamber of an engine comprising a piston to be utilized in an efficient manner.

[0016] Optionally, at least one of the fuel guide surfaces includes a curved trailing edge having a radius of curvature that is less than a radial distance from the central axis to the curved trailing edge. This provides a piston capable of effectively guiding the fuel spray while providing conditions for effective airflow through the gap into the fuel spray guided by the fuel guide surface.

[0017] Optionally, the radius of curvature is less than 70% of the radial distance from the central axis to the arcuate trailing edge.Thus, the provided piston can guide the fuel spray in an effective manner while providing conditions for effective airflow to enter the fuel spray guided by the fuel guide surface through the gap.

[0018] Optionally, the radial distance from the central axis to the trailing edge of the fuel guide surface is 10%-50% greater than the radial distance from the central axis to the radially inner boundary surface of the gap. This provides conditions for effective airflow through the gap into the fuel spray guided by the fuel guide surface.

[0019] Optionally, the radial distance from the central axis to the trailing edge of the fuel guide surface is within a range of 25%-70% of the piston radius, or within a range of 35%-55% of the piston radius. This provides for a relatively short distance between the injector orifice and the fuel guide surface. This reduces interaction between the flame and the combustion chamber walls, and thus reduces heat transfer to the combustion chamber walls.

[0020] Optionally, the fuel guide surface is inclined relative to the radial direction of the piston. This provides conditions for directing the fuel spray in a direction that reduces the interaction between the flame and the walls of the combustion chamber. In this way, heat transfer to the walls of the combustion chamber can be reduced.

[0021] Optionally, the fuel guide surface is inclined at a positive pitch angle relative to the radial direction of the piston. This provides conditions for directing the fuel spray in a direction that reduces interaction between the flame and the walls of the combustion chamber. In this way, heat transfer to the walls of the combustion chamber can be reduced.

[0022] Optionally, the positive pitch angle is in the range of 3 to 14 degrees, or in the range of 4.5 to 7.5 degrees. This provides conditions for directing the fuel spray in a direction that reduces interaction between the flame and the walls of the combustion chamber. In this way, heat transfer to the walls of the combustion chamber can be reduced.

[0023] Optionally, the distance between the trailing edge of the fuel guide surface and the piston top surface adjacent to the trailing edge, measured along the central axis, is within a range of 3%-25% of the piston radius, or within a range of 7%-14% of the piston radius. This provides for efficient airflow through the gap into the fuel spray guided by the fuel guide surface. Furthermore, this provides for efficient air flow into the fuel spray from the area between the piston top surface and the trailing edge of the fuel guide surface.

[0024] Optionally, the piston is a piston for a compression ignition engine. Thus, the provided piston for a compression ignition engine has conditions for improving combustion heat release without significantly affecting heat transfer to the walls of the combustion chamber. Consequently, the provided piston has conditions for improving the fuel efficiency of the compression ignition engine.

[0025] According to a second aspect of the present invention, this object is achieved by an internal combustion engine comprising a cylinder and a piston according to some embodiments of the present disclosure, wherein the piston is configured to reciprocate in the cylinder.

[0026] Since the internal combustion engine includes a piston according to some embodiments, the provided engine has conditions for improving combustion heat release without significantly affecting heat transfer to the walls of the combustion chamber. Therefore, the provided internal combustion engine has conditions for improving fuel efficiency.

[0027] Thus, an internal combustion engine is provided which overcomes or at least alleviates at least some of the above mentioned problems and disadvantages.Thus, the above mentioned objects are achieved.

[0028] Optionally, the engine includes a fuel injector comprising a number of orifices, wherein each orifice is configured to inject a fuel spray onto a fuel guiding surface of the piston. Thus, an engine is provided that can guide the fuel spray in an efficient manner to improve combustion heat release without significantly affecting heat transfer to the walls of the engine's combustion chamber.

[0029] Optionally, the central axis of the piston extends through the fuel injector. This provides an engine capable of directing a uniform and well-distributed fuel spray into the combustion chamber. This provides conditions for improving the air / fuel mixture and, therefore, combustion heat release. Furthermore, a relatively short distance between the orifice of the engine's injector and the fuel-introducing surface is provided. This reduces interaction between the flame and the walls of the engine's combustion chamber, and, therefore, reduces heat transfer to the combustion chamber walls.

[0030] Optionally, the engine is a compression ignition engine. Thus, the provided compression ignition engine has conditions for improving combustion heat release without significantly affecting heat transfer to the walls of the combustion chamber. Therefore, the provided compression ignition engine has conditions for improving fuel efficiency.

[0031] According to a third aspect of the invention, this object is achieved by a vehicle comprising an internal combustion engine according to some embodiments of the present disclosure.

[0032] Thus, a vehicle is provided which has the conditions for improving fuel efficiency. Thus, a vehicle is provided which overcomes or at least mitigates at least some of the problems and disadvantages mentioned above. Thus, the objects mentioned above are achieved.

[0033] Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Various aspects of the present invention, including its particular features and advantages, will be readily understood from the exemplary embodiments discussed in the following detailed description and accompanying drawings, in which:

[0035] Figure 1 shows a vehicle according to some embodiments,

[0036] Figure 2 Schematically shows Figure 1 The internal combustion engine of the vehicle shown in

[0037] Figure 3 Shown Figure 2 A perspective view of a piston of an internal combustion engine is shown in,

[0038] Figure 4 Shown Figure 3 A top view of the piston shown in FIG.

[0039] Figure 5 Shown Figure 3 and Figure 4 The cross section of the piston is shown in FIG, and

[0040] Figure 6 Shown Figure 5 A portion of the cross section is shown in . DETAILED DESCRIPTION

[0041] Aspects of the present invention will now be described more fully. Like numbers refer to like elements throughout. For the sake of brevity and / or clarity, well-known functions or configurations will not necessarily be described in detail.

[0042] Figure 1 A vehicle 2 is shown according to some embodiments. The vehicle 2 includes an internal combustion engine 4. The internal combustion engine 4 is configured to provide motive power to the vehicle 2 via wheels 32 of the vehicle 2.

[0043] According to the embodiment shown, the vehicle 2 is a truck. However, according to other embodiments, as mentioned herein, the vehicle 2 may be another type of manned or unmanned vehicle for land-based or water-based propulsion, such as a truck, bus, construction vehicle, tractor, car, ship, boat, etc.

[0044] Figure 2 Schematically shows Figure 1, an internal combustion engine 4 of a vehicle 2 is shown in FIG. For reasons of brevity and clarity, the internal combustion engine 4 is referred to as “engine 4” in some places herein. As indicated above, the engine 4 is configured to provide motive power to a vehicle including the engine 4. However, according to further embodiments, as mentioned herein, the engine 4 may be a stationary engine, such as an engine configured to power a generator to generate electricity. The internal combustion engine 4 includes a number of pistons 1, each of which is configured to reciprocate in a corresponding cylinder 6 of the internal combustion engine 4. According to the embodiment shown, the engine 4 includes four cylinders 6 and four pistons 1. According to further embodiments, the engine 4 may include another number of cylinders 6 and pistons 1.

[0045] Internal combustion engine 4 includes a fuel injector 8 disposed in each cylinder 6. Fuel injector 8 is configured to inject fuel directly into cylinder 6 of internal combustion engine 4. Therefore, internal combustion engine 4, as referred to herein, may also be referred to as a "direct injection engine." Furthermore, according to the illustrated embodiment, internal combustion engine 4 is a four-stroke engine. Therefore, internal combustion engine 4, as referred to herein, may also be referred to as a "four-stroke internal combustion engine," a "direct injection four-stroke internal combustion engine," or the like.

[0046] Furthermore, according to the embodiment shown, the internal combustion engine 4 is a diesel engine. According to further embodiments, the internal combustion engine 4 as referred to herein may be another type of compression ignition engine, or an Otto engine with spark ignition, wherein the Otto engine may be configured to run on gas, gasoline, alcohol, similar volatile fuels, or combinations thereof.

[0047] Figure 3 Shown Figure 2 is a perspective view of a piston 1 of an internal combustion engine 4 shown in . The piston 1 is configured to reciprocate along a central axis ca of the piston 1 during operation in the engine. When the piston 1 is arranged in a cylinder of the engine, the central axis ca of the piston 1 coincides with the central axis of the cylinder of the engine.

[0048] like Figure 3 As can be seen in the figure, the piston 1 includes a certain number of fuel guide surfaces 3. The fuel guide surfaces 3 are arranged at a distance d1 from the top surface 5 of the piston 1, measured along the central axis ca. In other words, the piston 1 includes a protruding area 16 protruding from the top surface 5 of the piston 1. The fuel guide surfaces 3 are arranged on the top surface 16' of the protruding area 16. According to another embodiment, the piston 1 may include one protrusion 16 for each fuel guide surface 3, wherein each fuel guide surface 3 is arranged on the top surface 16' of the protrusion 16. When the piston 1 is arranged in the cylinder of the engine, the top surface 5 of the piston 1, the top surface 16' of the protruding area 16, and the fuel guide surfaces 3 face the combustion chamber and form its delimiting surface.

[0049] Each fuel guide surface 3 is configured to guide the fuel spray injected onto the fuel guide surface 3. Figure 3 As clearly seen in the figure, the fuel guide surfaces 3 are arranged such that a gap 7 is formed between two adjacent fuel guide surfaces 3. In this way, air can flow through the gap 7 into the fuel spray injected onto the fuel guide surfaces 3. This provides an improved mixing ratio between air and fuel. As further explained herein, the piston 1 is thus provided with conditions for improving combustion heat release without significantly affecting heat transfer to the walls of the combustion chamber.

[0050] According to the embodiment shown, the piston 1 comprises ten fuel guide surfaces 3. However, for reasons of simplicity and clarity, Figure 3 Only some of the fuel guide surfaces 3 in the piston 1 have been provided with the reference number "3". According to further embodiments, the piston 1 may include another number (e.g., a number between four and sixteen) of fuel guide surfaces 3. The piston 1 is configured to be combined with a fuel injector having the same number of orifices as the number of fuel guide surfaces 3, such that each orifice is configured to inject a fuel spray onto the fuel guide surface 3 of the piston 1.

[0051] According to the embodiment shown, a number of fuel guide surfaces 3 are distributed around a centre axis ca of the piston 1. When the piston 1 is arranged in a cylinder of an engine, the centre axis ca of the piston 1 may coincide with a centre axis of a fuel injector.

[0052] According to the illustrated embodiment, the fuel guide surfaces 3 are arranged such that a gap 7 is formed between a pair of adjacent fuel guide surfaces 3. Figure 3 As seen in FIG, each fuel guide surface 3 comprises a trailing edge 3 ′, and wherein a gap 7 is formed between the trailing edges 3 ′ of two adjacent fuel guide surfaces 3 along the circumferential direction cd of the piston 1 .

[0053] According to the illustrated embodiment, the piston 1 includes a piston bowl 9. As indicated above, according to the illustrated embodiment, the piston 1 is a piston 1 for a compression ignition engine. A certain number of fuel guide surfaces 3 are arranged in the piston bowl 9. In addition, according to the illustrated embodiment, the piston 1 includes a central protrusion 11 that protrudes from the top surface 5 of the piston 1 at a position between the certain number of fuel guide surfaces 3. According to the illustrated embodiment, the central protrusion 11 is conical. According to another embodiment, the central protrusion 11 may be frustoconical. According to the illustrated embodiment, the central axis of the central protrusion 11 coincides with the central axis ca of the piston 1.

[0054] Figure 4 Shown Figure 3 The top view of the piston 1 is shown in FIG. Figure 4, the piston 1 is shown as seen in a direction directly towards the top surface 5 of the piston 1 , ie in a viewing direction coinciding with the centre axis ca of the piston 1 .

[0055] like Figure 4 as well as Figure 3 As can be seen in FIG, each of the fuel guide surfaces 3 comprises a curved trailing edge 3'. Figure 4 As shown in , the radius of curvature rc1 of each curved trailing edge 3' is less than the radial distance r1 from the central axis ca to the curved trailing edge 3'. As is the case according to the illustrated embodiment, each curved trailing edge 3' may have a varying radius of curvature rc1 along the trailing edge 3'. The radius of curvature rc1 is measured in a plane P perpendicular to the central axis ca. According to the illustrated embodiment, the minimum radius of curvature rc1 of the trailing edge 3' is approximately 13% of the radial distance r1 from the central axis ca of the piston 1 to the curved trailing edge 3'. According to other embodiments, the minimum radius of curvature r1 of the trailing edge 3' may be in the range of 3%-70% or 7%-25% of the radial distance r1 from the central axis ca to the curved trailing edge 3'.

[0056] According to the embodiment shown, the radial distance r1 from the center axis ca of the piston 1 to the trailing edge 3' of the fuel guide surface 3 is approximately 33% greater than the radial distance r2 from the center axis ca to the radially inner delimiting surface 7' of the gap 7. According to another embodiment, the radial distance r1 from the center axis ca to the trailing edge 3' of the fuel guide surface 3 may be 10%-50% greater than the radial distance r2 from the center axis ca to the radially inner delimiting surface 7' of the gap 7.

[0057] According to the illustrated embodiment, the radial distance r1 from the central axis ca of the piston 1 to the trailing edge 3' of the fuel guide surface 3 is approximately 45% of the radius r of the piston 1. According to other embodiments, the radial distance r1 from the central axis ca to the trailing edge 3' of the fuel guide surface 3 may be in the range of 25%-70% of the radius r of the piston 1, or may be in the range of 35%-55% of the radius r of the piston 1.

[0058] Figure 5 Shown Figure 3 and Figure 4 The cross section of the piston 1 is shown in FIG. Figure 5 In the figure, the cross section is taken in a plane including the center axis ca of the piston 1. Figure 5 In FIG, the fuel guide surface 3 and the trailing edge 3' of the fuel guide surface 3 are indicated. Figure 5 In FIG. 5 , the top surface 5 of the piston 5 , the piston bowl 9 and the central protrusion 11 are indicated.

[0059] Figure 6 Shown Figure 5 In addition, in Figure 6 In FIG, a cross section of a fuel injector 8 is schematically shown. The fuel injector 8 is arranged so that its center axis coincides with the center axis ca of the piston 1. In other words, according to the embodiment shown, the center axis ca of the piston 1 extends through the fuel injector 8. The fuel injector 8 comprises a needle 34 and a number of orifices 10. The position of the needle 34 controls the flow of fuel through the orifices 10. In FIG. Figure 6 In FIG, only one orifice 10 is seen. However, as mentioned above, the fuel injector 8 may include the same number of orifices 10 as the number of fuel guide surfaces 3 of the piston 1. Each orifice 10 is configured to inject a fuel spray 12 onto the fuel guide surface 3 of the piston 1. Figure 6 , such a fuel spray 12 is schematically shown.

[0060] According to the embodiment shown, the fuel guide surface 3 is inclined relative to the radial direction rd of the piston 1. Figure 6 As indicated in FIG, the radial direction rd of the piston 1 intersects the central axis ca of the piston 1 and is parallel to a plane P perpendicular to the central axis ca of the piston 1. More specifically, according to the illustrated embodiment, the fuel guide surface 3 is inclined at a positive pitch angle a1 relative to the radial direction rd of the piston 1. As used herein, the definition of "positive pitch angle a1" is the angle a1 at which the fuel guide surface 3, as seen in the radial direction r of the piston 1 pointing in the direction from the central axis ca of the piston 1, increases the distance between the fuel guide surface 3 and the top surface 5 of the piston 1 adjacent to the fuel guide surface 3 along the fuel guide surface 3.

[0061] According to the illustrated embodiment, the positive pitch angle a1 is approximately 6 degrees. According to other embodiments, the positive pitch angle a1 may be in the range of 3 to 14 degrees, or in the range of 4.5 to 7.5 degrees. In this way, fuel from the fuel spray 12 impacting the fuel guide surface 3 can be rebounded against the fuel guide surface 3 in a direction that reduces interaction between the flame and the walls of the combustion chamber. In this way, heat transfer to the walls of the combustion chamber can be further reduced. According to still other embodiments, one or more of the fuel guide surfaces 3 may be inclined at a negative pitch angle a1 relative to the radial direction rd of the piston 1.

[0062] According to the illustrated embodiment, a distance d1 between the trailing edge 3' of the fuel guide surface 3 and the top surface 5 of the piston 1 adjacent to the trailing edge 3', as measured along the center axis ca, is approximately 10.5% of the radius r of the piston 1. According to other embodiments, the distance d1 between the trailing edge 3' of the fuel guide surface 3 and the top surface 5 of the piston 1 adjacent to the trailing edge 3', as measured along the center axis ca, may be in the range of 3%-25% of the radius r of the piston 1, or may be in the range of 7%-14% of the radius r of the piston 1. Thus, air can be efficiently delivered to the fuel spray 12 that bounces off the fuel guide surface 3 from the area between the top surface 5 of the piston 1 and the trailing edge 3' of the fuel guide surface 3.

[0063] It should be understood that the foregoing is a description of various exemplary embodiments, and that the present invention is limited only by the appended claims. Those skilled in the art will recognize that modifications may be made to the exemplary embodiments, and that different features of the exemplary embodiments may be combined to produce embodiments other than those described herein, without departing from the scope of the present invention as defined by the appended claims.

[0064] As used herein, the terms “comprising” and “comprises” are open ended and include one or more stated features, elements, steps, components or functions, but do not preclude the existence or addition of one or more other features, elements, steps, components, functions or groups thereof.

Claims

1. A piston (1) for an internal combustion engine (4), the piston (1) being configured to reciprocate along a central axis (ca) of the piston (1) during operation in the engine (4), wherein the piston (1) comprises a number of fuel guide surfaces (3) arranged at a distance (d1) from a top surface (5) of the piston (1) measured along the central axis (ca), Each fuel guide surface (3) is configured to guide a fuel spray (12) injected onto the fuel guide surface (3), The fuel guide surfaces (3) are arranged with a gap (7) between two adjacent fuel guide surfaces (3), wherein the fuel guide surfaces (3) are inclined at a positive pitch angle (a1) relative to the radial direction (rd) of the piston (1), whereby fuel of a fuel spray (12) impacting the fuel guide surfaces (3) can rebound against the fuel guide surfaces (3) in a direction that reduces the interaction between the flame and the wall of the combustion chamber.

2. The piston (1) according to claim 1, wherein each fuel guide surface (3) comprises a trailing edge (3'), and wherein the gap (7) is formed between the trailing edges (3') of two adjacent fuel guide surfaces (3) along the circumferential direction (cd).

3. The piston (1) according to claim 1 or 2, wherein the piston (1) comprises a piston bowl (9), and wherein the number of fuel guiding surfaces (3) are arranged in the piston bowl (9).

4. The piston (1) according to claim 1 or 2, wherein the number of fuel guiding surfaces (3) is distributed around a central axis (ca) of the piston (1).

5. The piston (1) according to claim 1 or 2, wherein the piston (1) includes a central protrusion (11) protruding from a top surface (5) of the piston (1) at a position between the number of fuel guide surfaces (3).

6. Piston (1) according to claim 5, wherein the central projection (11) is conical or frustoconical.

7. The piston (1) according to claim 1 or 2, at least one of the fuel guide surfaces (3) comprises a curved trailing edge (3'), the radius of curvature (rc1) of the curved trailing edge being smaller than the radial distance (r1) from the center axis (ca) to the curved trailing edge (3').

8. The piston (1) according to claim 7, wherein the radius of curvature (rc1) is less than 70% of the radial distance (r1) from the central axis (ca) to the arcuate trailing edge (3').

9. Piston (1) according to claim 7, wherein the radius of curvature (rc1) is measured in a plane (P) perpendicular to the central axis (ca).

10. The piston (1) according to claim 1 or 2, wherein the radial distance (r1) from the center axis (ca) to the trailing edge (3') of the fuel guide surface (3) is 10%-50% greater than the radial distance (r2) from the center axis (ca) to the radially inner delimiting surface (7') of the gap (7).

11. The piston (1) according to claim 1 or 2, wherein the radial distance (r1) from the central axis (ca) to the trailing edge (3') of the fuel guide surface (3) is in the range of 25%-70% of the radius (r) of the piston (1).

12. The piston (1) according to claim 1, wherein the positive pitch angle (al) is in the range of 3 degrees to 14 degrees.

13. The piston (1) according to claim 1 or 2, wherein a distance (d1) between a trailing edge (3') of the fuel guide surface (3) and a top surface (5) of the piston (1) adjacent to the trailing edge (3') measured along the center axis (ca) is in the range of 3%-25% of a radius (r) of the piston (1).

14. The piston (1) according to claim 1 or 2, wherein the piston (1) is a piston (1) for a compression ignition engine (4).

15. An internal combustion engine (4), comprising: - a cylinder (6), and - A piston (1) according to any one of the preceding claims, The piston (1) is configured to reciprocate in the cylinder (6).

16. The engine (4) according to claim 15, wherein the engine (4) comprises a fuel injector (8), the fuel injector comprising a number of orifices (10), and wherein each orifice (10) is configured to inject a fuel spray (12) onto the fuel guiding surface (3) of the piston (1).

17. The engine (4) according to claim 16, wherein the central axis (ca) of the piston (1) extends through the fuel injector (8).

18. The engine (4) according to any one of claims 15-17, wherein the engine (4) is a compression ignition engine (4).

19. A vehicle (2) comprising an internal combustion engine (4) according to any one of claims 15 to 18.

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