Piston, internal combustion engine, and vehicle

Abstract

A piston (1) for an internal combustion engine (4) is disclosed. The piston (1) comprises a number of fuel guiding surfaces (3) for guiding a fuel spray (12) injected onto the fuel guiding surfaces (3). At least one of the fuel guiding surfaces (3) is inclined relative to a tangential direction (Td) of the piston (1). The disclosure also relates to an engine (4) comprising the piston (1) and a vehicle (2) comprising the internal combustion engine (4).

Description

Technical Field

[0001] This disclosure relates to a piston for an internal combustion engine. This disclosure further relates to an internal combustion engine including a cylinder and a piston configured to reciprocate within the cylinder. Moreover, this disclosure relates to a vehicle including an internal combustion engine. Background Technology

[0002] An internal combustion engine, such as a four-stroke engine, includes one or more cylinders and a piston arranged in each cylinder. The piston is connected to the engine's crankshaft and 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 belts, chains, gears, or similar means. A four-stroke internal combustion engine completes four separate strokes as the crankshaft rotates. A stroke refers to the complete travel of the piston along the cylinder in any direction. The uppermost position of the piston in the cylinder is commonly referred to as top dead center (TDC), and the lowermost position is commonly referred to as bottom dead center (BDC). The strokes are completed in the following order: intake stroke, compression stroke, expansion stroke, and exhaust stroke.

[0003] Compression-ignition engines, such as diesel engines, include fuel injectors arranged in each cylinder of the engine. Additionally, many modern ignition engines, such as gasoline engines, include fuel injectors arranged in each cylinder of the engine. These types of engines are generally referred to as direct-injection engines. Fuel injectors typically include a number of orifices and needles 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 current cylinder. When fuel is injected into the cylinder through the orifices, a slightly cone-shaped fuel spray is formed within the cylinder.

[0004] Fuel consumption is a primary concern for internal combustion engines. Two ways to improve engine fuel efficiency are to reduce heat transfer to the combustion chamber walls and to increase heat release during combustion. However, these requirements are generally conflicting. That is, increasing heat release during combustion generally increases heat transfer to the combustion chamber walls, and vice versa.

[0005] Combustion heat release is a measure of combustion rate (i.e., the rate at which fuel is burning) and can be improved by increasing the air-fuel mixture. Improving the mixture is generally achieved by optimizing the intake swirl motion in the cylinder. However, this method has limitations.

[0006] Furthermore, when fuel spray is injected into the cylinder, a stoichiometric zone is formed around the fuel spray. Within this zone, there is a stoichiometric ratio between fuel and air. This zone 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 injectors and combustion chamber impose limitations on the size of the stoichiometric surface area. Summary of the Invention

[0007] The objective of this invention is to overcome or at least mitigate some of the problems and disadvantages mentioned above.

[0008] According to a first aspect of the invention, this objective is achieved by a piston for an internal combustion engine. The piston includes a number of fuel guiding surfaces for guiding a fuel spray injected onto the fuel guiding surfaces. At least one of the fuel guiding surfaces is inclined relative to the tangential direction of the piston.

[0009] Because at least one of the fuel guiding surfaces is inclined relative to the tangential direction of the piston, a fuel spray angled relative to the tangential direction of the piston is obtained after the fuel spray is guided by the fuel guiding surface. This prevents the merging of fuel sprays with adjacent fuel sprays. As a result, the total stoichiometric surface area of ​​the fuel spray can be increased, which in turn increases the heat release and fuel efficiency of the engine, including the piston.

[0010] Furthermore, because each fuel guide surface is configured to guide the fuel spray injected onto it, each fuel spray acquires 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 orifice, a slightly conical fuel spray is formed in the cylinder. A conical fuel spray has a circular cross-section in the direction 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 provided 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 in the direction perpendicular to the injection direction.

[0011] Therefore, a flat fuel spray has a larger surface area to volume ratio than a conical fuel spray, which provides a larger 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 has the conditions for improving combustion heat release without significantly affecting heat transfer to the combustion chamber walls. Therefore, also for this reason, the provided piston has the conditions for improving engine fuel efficiency.

[0012] Therefore, the provided piston overcomes or at least mitigates some of the problems and disadvantages mentioned above. Thus, the aforementioned objectives are achieved.

[0013] Optionally, the fuel guide surface is positioned at a distance from the piston's top surface, measured along the piston's central axis. This provides conditions for air to efficiently flow from the area between the piston's top surface and the trailing edge of the fuel guide surface into the fuel spray. In this way, the air-fuel mixture ratio can be increased, which in turn increases the heat release and fuel efficiency of the engine, including the piston.

[0014] Optionally, the piston includes a piston cup, and a number of fuel guiding surfaces are arranged within the piston cup. Thus, the provided piston can guide fuel spray into the piston cup while preventing the merging of fuel sprays. Therefore, the provided piston has the capability to improve combustion heat release without significantly affecting heat transfer to the combustion chamber walls.

[0015] Optionally, a number of fuel guide surfaces are distributed around the central axis of the piston. This allows the piston to guide the fuel spray into the combustion chamber in a uniform and well-distributed manner, while preventing the merging of fuel sprays. This provides conditions for improving the air / fuel mixture ratio and thus, consequently, improving the release of combustion heat. Furthermore, it provides conditions for a relatively short distance between the injector orifice and the fuel guide surfaces. This provides conditions for reducing the interaction between the flame and the combustion chamber walls, and thus, reducing heat transfer to the combustion chamber walls that negatively impacts engine fuel efficiency.

[0016] Optionally, the piston includes a central protrusion projecting from the top surface of the piston at a location between a number of fuel guide surfaces. Thus, the provided piston can achieve a high compression ratio in the cylinder and / or provide conditions for a larger piston cup without reducing the compression ratio in the cylinder.

[0017] Alternatively, the central protrusion may be conical or truncated conical. This provides an efficient structure that enables a high compression ratio in the cylinder while allowing fuel spray to be positioned laterally adjacent to the central protrusion. This allows for efficient utilization of the available space in the combustion chamber of an engine, including the piston.

[0018] Optionally, at least one fuel guide surface has an inclination angle between its angle and the tangential direction of the piston in the range of 1-45 degrees, or in the range of 7-21 degrees. This effectively prevents the merging of fuel sprays with adjacent fuel sprays. Consequently, it effectively increases the total stoichiometric surface area of ​​the fuel spray, which in turn increases the heat release and fuel efficiency of the engine, including the piston.

[0019] Optionally, each of the given number of fuel guiding surfaces is inclined relative to the tangential direction of the piston. This results in a fuel spray angled relative to the tangential direction of the piston after the fuel spray has been guided by the fuel guiding surfaces. This further prevents the merging of fuel sprays. Consequently, the total stoichiometric surface area of ​​the fuel spray can be further optimized to increase the heat release and fuel efficiency of the engine, including the piston.

[0020] Optionally, the fuel guiding surface is inclined in the same direction relative to the tangential direction of the piston. This further avoids merging between adjacent fuel sprays. As a result, the total stoichiometric surface area of ​​the fuel spray can be further increased, which in turn increases the heat release and fuel efficiency of the engine, including the piston.

[0021] Optionally, a number of fuel guide surfaces are provided with the same tilt angle relative to the tangential direction of the piston. This further prevents the merging of adjacent fuel sprays. As a result, the total stoichiometric surface area of ​​the fuel spray can be increased, which in turn increases the heat release and fuel efficiency of the engine, including the piston.

[0022] Optionally, the radial distance from the piston's central axis to the trailing edge of the fuel guide surface is in the range of 20%-70% of the piston radius, or in the range of 25%-55% of the piston radius. This provides conditions for a relatively short distance between the injector orifice and the fuel guide surface. This, in turn, provides conditions for reducing the interaction between the flame and the combustion chamber walls, and therefore also reducing heat transfer to the combustion chamber walls.

[0023] Optionally, the distance between the trailing edge of the fuel guide surface and the top surface of the piston adjacent to the trailing edge, measured along the central axis, is in the range of 2%-25% of the piston radius, or in the range of 4%-11% of the piston radius. This provides conditions for air to effectively flow from the region between the top surface of the piston and the trailing edge of the fuel guide surface into the fuel spray. In this way, the air-fuel mixture ratio can be increased, which in turn increases the heat release and fuel efficiency of the engine, including the piston.

[0024] Optionally, the fuel guiding surfaces are arranged with a gap between two adjacent fuel guiding surfaces. Because the fuel guiding surfaces are arranged with a gap between two adjacent fuel guiding surfaces, air can flow through the gap into the fuel spray guided by the fuel guiding surfaces. In this way, a further improved air-fuel mixture is provided. Therefore, the provided piston has the conditions for improving combustion heat release without significantly affecting heat transfer to the combustion chamber walls. Thus, the provided piston has the conditions for improving engine fuel efficiency.

[0025] Optionally, the piston is a piston for a compression ignition engine. Thus, the provided piston for a compression ignition engine has the potential to increase the total stoichiometric surface area of ​​the fuel spray. Therefore, the provided piston has the potential to improve the fuel efficiency of the compression ignition engine.

[0026] According to a second aspect of the invention, this objective is achieved by an internal combustion engine comprising a cylinder and a piston according to some embodiments of the present disclosure. The piston is configured to reciprocate within the cylinder.

[0027] Since the internal combustion engine includes a piston according to some embodiments, the provided engine has the potential to increase the total stoichiometric surface area of ​​the fuel spray. Therefore, the provided internal combustion engine has the potential to improve fuel efficiency.

[0028] Therefore, the provided internal combustion engine overcomes or at least mitigates some of the problems and disadvantages mentioned above. Thus, the aforementioned objectives are achieved.

[0029] Optionally, the engine includes a fuel injector comprising a number of orifices, wherein each orifice is configured to spray a fuel spray onto a fuel guide surface of the piston. Thus, the provided engine is able to guide the fuel spray in an efficient manner to avoid merging between fuel sprays and thereby increase the total stoichiometric surface area of ​​the fuel spray.

[0030] Optionally, the piston's central axis extends through the fuel injector. This allows the provided engine to guide the fuel spray into the combustion chamber in a uniform and well-distributed manner, while avoiding the merging of adjacent fuel sprays. This provides conditions for improving the air / fuel mixture ratio and thus, consequently, improving the release of combustion heat. Furthermore, it provides conditions for a relatively short distance between the injector orifice and the fuel guiding surface. This provides conditions for reducing the interaction between the flame and the walls of the engine's combustion chamber, and thus, also reducing heat transfer to the walls of the combustion chamber.

[0031] Optionally, the engine is a compression ignition engine. Therefore, the provided compression ignition engine has the potential to increase the total stoichiometric surface area of ​​the fuel spray. Consequently, the provided compression ignition engine has the potential to improve fuel efficiency.

[0032] According to a third aspect of the invention, this objective is achieved by a vehicle comprising an internal combustion engine according to some embodiments of the present disclosure.

[0033] Therefore, the provided vehicle possesses the conditions for improving fuel efficiency. Thus, the provided vehicle overcomes or at least mitigates some of the problems and disadvantages mentioned above. Therefore, the aforementioned objectives are achieved.

[0034] Further features and advantages of the invention will become apparent when examined in light of the appended claims and the following detailed description. Attached Figure Description

[0035] Various aspects of the invention, including its particular features and advantages, will be readily understood from the exemplary embodiments discussed in the following detailed description and accompanying drawings, wherein:

[0036] Figure 1 A vehicle according to some embodiments is shown.

[0037] Figure 2 schematically shown Figure 1 The internal combustion engine of the vehicle shown.

[0038] Figure 3 schematically shown Figure 2 The image shows a perspective view of the piston of an internal combustion engine.

[0039] Figure 4 The diagram schematically illustrates what is seen in the radial direction of the piston. Figure 3 The piston shown has a fuel guide surface.

[0040] Figure 5 This schematically illustrates when the injector sprays fuel into... Figure 3 A perspective view of the fuel spray obtained when the piston is on the fuel guide surface, as shown.

[0041] Figure 6 It shows the way Figure 3 The cross-section of a portion of the top surface of the piston shown. Detailed Implementation

[0042] The aspects of the invention will now be described more fully. The same numerals always refer to the same elements. For the sake of brevity and / or clarity, well-known functions or constructions will not be described in detail.

[0043] Figure 1 A vehicle 2 according to some embodiments is shown. The vehicle 2 includes an internal combustion engine 4. The internal combustion engine 4 is configured to provide prime mover power to the vehicle 2 via the wheels 32 of the vehicle 2.

[0044] According to the embodiment shown, vehicle 2 is a truck. However, according to another embodiment, as mentioned herein, vehicle 2 can 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.

[0045] Figure 2 schematically shown Figure 1The internal combustion engine 4 of the vehicle 2 shown herein. For simplicity and clarity, the internal combustion engine 4 is referred to as "engine 4" in some places herein. As indicated above, engine 4 is configured to provide prime mover power to the vehicle including engine 4. However, according to another embodiment, as mentioned herein, engine 4 may be a stationary engine, for example, configured to be powered by a generator to produce electricity. The internal combustion engine 4 includes a number of pistons 1, each piston configured to reciprocate in a corresponding cylinder 6 of the internal combustion engine 4. According to the embodiment shown, engine 4 includes four cylinders 6 and four pistons 1. According to another embodiment, engine 4 may include another number of cylinders 6 and pistons 1.

[0046] The internal combustion engine 4 includes fuel injectors 8 arranged in each cylinder 6. The fuel injectors 8 are configured to inject fuel directly into the cylinders 6 of the internal combustion engine 4. Therefore, the internal combustion engine 4, as mentioned herein, can also be referred to as a "direct injection engine". Furthermore, according to the illustrated embodiment, the internal combustion engine 4 is a four-stroke engine. Therefore, the internal combustion engine 4, as mentioned herein, can also be referred to as a "four-stroke internal combustion engine", "direct injection four-stroke internal combustion engine", etc.

[0047] Furthermore, according to the illustrated embodiment, the internal combustion engine 4 is a diesel engine. According to another embodiment, the internal combustion engine 4, as mentioned herein, may be another type of compression-ignition engine, or an Otto engine with a spark ignition device, wherein the Otto engine may be configured to operate on gas, gasoline, alcohol, similar volatile fuels, or combinations thereof.

[0048] Figure 3 schematically shown Figure 2 The image shows a perspective view of the piston 1 of the internal combustion engine 4. The piston 1 is configured to reciprocate along its central axis ca during operation in the engine. When the piston 1 is positioned in the engine cylinder, its central axis ca coincides with the central axis of the engine cylinder.

[0049] like Figure 3 As can be seen, the piston 1 includes a number of fuel guiding surfaces 3. According to the illustrated embodiment, the fuel guiding surfaces 3 are arranged at a distance d1 from the top surface 5 of the piston 1, measured along the central axis ca. That is, the piston 1 includes a protruding region 16 projecting from the top surface 5 of the piston 1. The fuel guiding surfaces 3 are arranged on the top surface 16' of the protruding region 16. According to another embodiment, the piston 1 may include a protrusion 16 for each fuel guiding surface 3, wherein each fuel guiding surface 3 is arranged on the top surface 16' of the protrusion 16.

[0050] When piston 1 is arranged in the cylinder of the engine, the top surface 5 of piston 1, the top surface 16' of protruding region 16, and fuel guiding surface 3 face the combustion chamber and form their defining surfaces.

[0051] Each fuel guiding surface 3 is configured to guide the fuel spray injected onto the fuel guiding surface 3. Furthermore, as... Figure 3 As seen in the illustrated embodiment, each fuel guide surface 3 is inclined relative to the tangential direction Td of the piston 1. In this way, as further explained herein, a fuel spray angled relative to the tangential direction Td of the piston 1 is obtained. According to some embodiments, one or more of the fuel guide surfaces 3 may be inclined relative to the tangential direction Td of the piston 1. For example, every other fuel guide surface 3 around the circumferential direction cd of the piston 1 may be inclined relative to the tangential direction Td of the piston 1.

[0052] According to the embodiment shown, the piston 1 includes ten fuel guiding surfaces 3. However, for reasons of simplicity and clarity, Figure 3 Only some of the fuel guiding surfaces 3 are marked with reference numeral "3". According to another embodiment, the piston 1 may include another number (e.g., between four and sixteen) of fuel guiding 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 guiding surfaces 3, such that each orifice is configured to spray fuel onto the fuel guiding surface 3 of the piston 1.

[0053] According to the embodiment shown, a certain number of fuel guiding surfaces 3 are distributed around the central axis ca of the piston 1. When the piston 1 is arranged in the cylinder of the engine, the central axis ca of the piston 1 can coincide with the central axis of the fuel injector.

[0054] like Figure 3 As can be seen in the illustrated embodiment, each of the plurality of fuel guiding surfaces 3 is inclined relative to the tangential direction Td of the piston 1. Furthermore, the fuel guiding surfaces 3 are inclined in the same direction relative to the tangential direction Td of the piston 1, wherein each tangential direction Td points to the same direction of rotation, i.e., clockwise or counterclockwise. Moreover, according to the illustrated embodiment, the plurality of fuel guiding surfaces 3 are provided with the same inclination angle α0 relative to the tangential direction Td of the piston 1. However, one or more of the plurality of fuel guiding surfaces 3 may be provided with an inclination angle α0 that differs from the other inclination angles α0 of the other fuel guiding surfaces 3.

[0055] According to the illustrated embodiment, the fuel guiding surfaces 3 are arranged such that a gap 7 is formed between a pair of adjacent fuel guiding surfaces 3. Furthermore, as... Figure 3As seen, each fuel guiding surface 3 includes a trailing edge 3', and a gap 7 is formed along the circumferential direction cd of the piston 1 between the trailing edges 3' of two adjacent fuel guiding surfaces 3. This provides an improved air-fuel mixture because air can flow through the gap 7 into the fuel spray guided by the fuel guiding surfaces 3. As a result, the provided piston 1 has conditions for improving combustion heat release without significantly affecting heat transfer to the combustion chamber walls.

[0056] According to the illustrated embodiment, piston 1 includes piston cup 9. As indicated above, according to the illustrated embodiment, piston 1 is a piston 1 for a compression ignition engine. A number of fuel guide surfaces 3 are arranged in piston cup 9. Furthermore, according to the illustrated embodiment, piston 1 includes a central protrusion 11 projecting from top surface 5 of piston 1 at a position between the number of fuel guide surfaces 3. According to the illustrated embodiment, central protrusion 11 is conical. According to another embodiment, central protrusion 11 may be truncated conical. According to the illustrated embodiment, the central axis of central protrusion 11 coincides with the central axis ca of piston 1.

[0057] Figure 4 It schematically shows, as in Figure 3 The fuel guiding surface 3 is shown as seen in the radial direction rd of the piston 1. Figure 3 As indicated in the diagram, the radial direction rd of piston 1 intersects the central axis ca of piston 1 and is parallel to the plane P that is perpendicular to the central axis ca. Therefore, the radial direction rd of piston 1 is perpendicular to the central axis ca of piston 1.

[0058] like Figure 3 and Figure 4 As indicated, the tangential direction Td of piston 1 is perpendicular to the radial direction rd of piston 1, and extends in a plane P perpendicular to the central axis ca of piston 1. Figure 4 In the diagram, line 3s is drawn across the fuel guide surface 3. Line 3 is drawn in a direction perpendicular to the radial direction rd of the piston. (See diagram for reference.) Figure 4 As can be clearly seen, the fuel guiding surface 3 is inclined relative to the tangential direction Td of the piston 1. In this way, after the fuel spray 12 has been guided by the fuel guiding surface 3, a fuel spray 12 at an angle relative to the tangential direction Td of the piston is obtained. Figure 4 In the diagram, the cross-section of this type of fuel spray 12 is schematically indicated by dashed lines.

[0059] Generally, when fuel is freely injected into the cylinder through the injector orifice, a slightly conical fuel spray is formed in the cylinder. This conical fuel spray has a circular cross-section in a direction perpendicular to the injection direction. However, because the fuel guide surface 3 is configured to guide the fuel spray injected onto it, a flatter fuel spray 12 is provided after the impact between the fuel spray and the corresponding fuel guide surface 3. Figure 4 As can be seen, compared to a conical fuel spray, this type of fuel spray has a more elliptical cross-section in a plane perpendicular to the flow direction.

[0060] According to the embodiment shown, the tilt angle α0 between the fuel guiding surface 3 and the tangential direction Td of the piston 1 is approximately 14 degrees. According to another embodiment, the tilt angle α0 between at least one fuel guiding surface 3 and the tangential direction Td of the piston 1 may be in the range of 1-45 degrees, or in the range of 7-21 degrees.

[0061] like Figure 4 As seen in the illustrated embodiment, the fuel guiding surface 3 is substantially flat along line 3s. Furthermore, according to the illustrated embodiment, the inclination angle α0 between the fuel guiding surface 3 and the tangential direction Td of the piston 1 is substantially constant along the radial direction rd of the piston 1. However, according to some embodiments, the fuel guiding surface 3 may have a varying inclination angle α0 along the radial direction rd of the piston 1 between the fuel guiding surface 3 and the tangential direction Td of the piston 1.

[0062] Furthermore, according to some embodiments, the fuel guiding surface 3 may be curved along a line 3s drawn across the fuel guiding surface 3s in a direction perpendicular to the radial direction rd of the piston. Therefore, according to such embodiments, the fuel guiding surface 3 may have a varying tilt angle α0 between the fuel guiding surface 3 and the tangential direction Td of the piston along the line 3s drawn across the fuel guiding surface 3s in a direction perpendicular to the radial direction rd of the piston. According to such embodiments, the fuel guiding surface 3 may have a positive or negative average tilt angle α0 between the fuel guiding surface 3 and the tangential direction Td of the piston along the line 3s drawn across the fuel guiding surface 3s in a direction perpendicular to the radial direction rd of the piston. In this way, an angled fuel spray 12 can be ensured after the fuel spray is deflected by the fuel guiding surface 3.

[0063] Figure 5 This schematically illustrates when the injector sprays fuel into... Figure 3 A perspective view of the fuel spray 12 obtained when the piston 1 is on the fuel guide surface 3 shown. As mentioned, and as Figure 3As can be seen, each of the certain number of fuel guiding surfaces 3 is inclined relative to the tangential direction Td of the piston 1. Furthermore, the fuel guiding surfaces 3 are inclined in the same direction relative to the tangential direction Td of the piston 1. Moreover, according to the illustrated embodiment, the certain number of fuel guiding surfaces 3 are provided with the same inclination angle α0 relative to the tangential direction Td of the piston 1.

[0064] Due to these features, a set of fuel sprays 12 is provided, wherein the fuel sprays 12 are angled relative to each other in the same direction with respect to the tangential direction of the piston. Furthermore, relatively thin fuel sprays 12 are provided, which are stacked on top of each other in the circumferential direction cd of the combustion chamber. This avoids merging and interaction between the fuel sprays 12 and achieves a large total stoichiometric surface area of ​​the fuel sprays 12. As a result, the available space in the combustion chamber is utilized in a more optimized manner to provide a large total stoichiometric surface area of ​​the fuel sprays 12.

[0065] Figure 6 It shows the way Figure 3 The cross-section of a portion of the top surface 5 of the piston 1 shown. Furthermore, in Figure 6 The cross-section of the fuel injector 8 is schematically shown in the diagram. Figure 6 In this embodiment, the cross-section is taken in a plane including the central axis ca of piston 1. Fuel injector 8 is arranged such that its central axis coincides with the central axis ca of piston 1. In other words, according to the illustrated embodiment, the central axis ca of piston 1 extends through fuel injector 8. Fuel injector 8 includes a needle 34 and a number of orifices 10. The position of the needle 34 controls the fuel flow through the orifices 10. Figure 6 In the image, only one orifice 10 is visible. 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 fuel spray 12 onto the fuel guide surface 3 of the piston 1. Figure 6 The image shows, schematically, such a fuel spray 12.

[0066] According to the illustrated embodiment, the fuel guide surface 3 is inclined relative to the radial direction rd of the piston 1. More specifically, according to the illustrated embodiment, the fuel guide surface 3 is inclined with a positive pitch angle α1 relative to the radial direction rd of the piston 1. As used herein, "positive pitch angle α1" is defined as the angle α1 by which the distance between the fuel guide surface 3 and the top surface 5 of the piston 1 adjacent to the fuel guide surface 3 increases along the fuel guide surface 3 in the radial direction r of the piston 1 pointing from the central axis ca of the piston 1.

[0067] According to the illustrated embodiment, the positive pitch angle a1 is approximately 5 degrees. According to another embodiment, the positive pitch angle a1 can be in the range of 1 to 14 degrees, or in the range of 4 to 7 degrees. In this way, the fuel spray 12 impacting the fuel guide surface 3 can bounce off the fuel guide surface 3 in a direction that reduces the interaction between the flame and the combustion chamber wall. This further reduces heat transfer to the combustion chamber wall. According to yet another embodiment, one or more of the fuel guide surfaces 3 can be tilted relative to the radial direction rd of the piston 1 at a negative pitch angle a1.

[0068] According to the illustrated embodiment, 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', measured along the central axis ca, is approximately 7.5% of the radius r of the piston 1. According to another embodiment, 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', measured along the central axis ca, can be in the range of 2%-25% of the radius r of the piston 1, or in the range of 4%-11% of the radius r of the piston 1. Thus, air can be efficiently delivered into the fuel spray 12, which is deflected by the fuel guide surface 3 from the region between the top surface 5 of the piston 1 and the trailing edge 3' of the fuel guide surface 3.

[0069] Furthermore, 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 guiding surface 3 is approximately 40% of the radius r of the piston 1. According to another embodiment, the radial distance r1 from the central axis ca of the piston 1 to the trailing edge 3' of the fuel guiding surface 3 can be in the range of 20%-70% of the radius r of the piston 1, or in the range of 25%-55% of the radius r of the piston 1.

[0070] It should be understood that the foregoing is a description of various exemplary embodiments, and the invention is defined only by the appended claims. Those skilled in the art will recognize that modifications can be made to the exemplary embodiments without departing from the scope of the invention as defined by the appended claims, and different features of the exemplary embodiments can be combined to produce embodiments other than those described herein.

[0071] As used herein, the term “comprising / comprises” is open-ended and includes one or more of the stated features, elements, steps, components, or functions, but does not exclude the presence 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), wherein the piston (1) comprises a number of fuel guiding surfaces (3) for guiding a fuel spray (12) injected onto the fuel guiding surfaces (3), and wherein at least one of the fuel guiding surfaces (3) is inclined with respect to a tangential direction (Td) of the piston (1), wherein the fuel guiding surface (3) is arranged on a protruding area (16) at a distance (dl) from a top surface (5) of the piston (1) measured along a center axis (ca) of the piston (1), and wherein the fuel guiding surface is inclined with a positive pitch angle with respect to a radial direction of the piston.

2. The piston (1) according to claim 1, 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).

3. The piston (1) according to any one of the preceding claims, wherein the number of fuel guiding surfaces (3) are distributed around a center axis (ca) of the piston (1).

4. The piston (1) according to claim 1 or 2, wherein the piston (1) comprises a center protrusion (11) protruding from a top surface (5) of the piston (1) at a location between the number of fuel guiding surfaces (3).

5. The piston (1) according to claim 4, wherein the center protrusion (11) is conical or frustoconical.

6. The piston (1) according to claim 1 or 2, wherein an inclination angle (ao) between at least one fuel guiding surface (3) and the tangential direction (Td) of the piston (1) is in the range of 1-45 degrees.

7. The piston (1) according to claim 1 or 2, wherein an inclination angle (ao) between at least one fuel guiding surface (3) and the tangential direction (Td) of the piston (1) is in the range of 7-21 degrees.

8. The piston (1) according to claim 1 or 2, wherein each of the number of fuel guiding surfaces (3) is inclined with respect to the tangential direction (Td) of the piston (1).

9. The piston (1) according to claim 8, wherein the fuel guiding surfaces (3) are inclined in the same direction with respect to the tangential direction (Td) of the piston (1).

10. The piston (1) according to claim 8, wherein the number of fuel guiding surfaces (3) are provided with the same inclination angle (ao) with respect to the tangential direction (Td) of the piston (1).

11. The piston (1) according to claim 1 or 2, wherein a radial distance (rl) from a center axis (ca) of the piston (1) to a trailing edge (3’) of the fuel guiding surface (3) is in the range of 20-70% of a radius (r) of the piston (1).

12. The piston (1) according to claim 1 or 2, wherein a radial distance (rl) from a centre axis (ca) of the piston (1) to a trailing edge (3’) of the fuel guiding surface (3) is in the range of 25-55% of a radius (r) of the piston (1).

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

14. The piston (1) according to claim 1 or 2, wherein a distance (dl) between a trailing edge (3’) of the fuel guiding surface (3) measured along the centre axis (ca) and a top surface (5) of the piston (1) adjacent to the trailing edge (3’) is in the range of 4-11% of the radius (r) of the piston (1).

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

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

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

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

19. The engine (4) according to any one of claims 16-18, wherein the engine (4) is a compression ignition engine.

20. A vehicle (2) comprising an internal combustion engine (4) according to any one of claims 16-19.

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