Large engine with longitudinal scavenging

Abstract

The present invention relates to a large longitudinally scavenged engine having at least one cylinder (10) in which a piston (60) is arranged to move back and forth along a cylinder axis (X), the cylinder having a cylinder head (20) that, together with the piston (60), defines a combustion chamber (120) for fuel, the large engine being designed to operate in a gas mode in which a premixed air-fuel mixture is burned in the combustion chamber (120), wherein a plurality of outlet valves (40) are provided in the cylinder head (20) for discharging exhaust gases from the combustion chamber (120), and wherein, in each case, a protrusion is provided on the cylinder head (20) between two adjacent outlet valves (40) that extends into the combustion chamber (120).

Description

Technical Field

[0001] This invention relates to a large engine with longitudinal scavenging. Background Technology

[0002] Large engines, which can be designed as two-stroke or four-stroke engines, such as longitudinally scavenged two-stroke large diesel engines, are typically used as propulsion units for ships or even in stationary operations, such as driving large generators to produce electricity. These engines often operate continuously for considerable periods, placing high demands on operational safety and availability. Therefore, exceptionally long maintenance intervals, low wear, and economical handling of operating materials are central criteria for operators. Large engines typically have cylinders with a bore (cylinder diameter) of at least 200 mm. Currently, large engines with bores up to 960 mm or even larger are also in use.

[0003] Another important aspect is energy efficiency and the quality of exhaust gases, particularly the concentration of nitrogen oxides or sulfur load in the exhaust. Another issue is the escape of unburned hydrocarbons, such as methane.

[0004] Here, legal requirements and corresponding exhaust emission limits are becoming increasingly stringent. As a result, especially in the case of large two-stroke diesel engines, the combustion of not only traditional heavy fuel oils, which are highly polluted by pollutants, but also diesel or other fuels such as natural gas is becoming increasingly problematic, as meeting exhaust emission limits is becoming more difficult, technically more complex, and therefore more expensive.

[0005] Regarding economical and efficient operation, compliance with exhaust emission limits, and resource availability, alternatives to heavy fuel oil, traditionally used as fuel for large engines, are being sought. Here, both liquid fuels (fuels introduced into the combustion chamber in a liquid state) and gaseous fuels (fuels introduced into the combustion chamber in a gaseous state) are being used.

[0006] Examples of liquid fuels known as alternatives to heavy fuel oils include other heavy hydrocarbons, alcohols (especially methanol or ethanol), gasoline, diesel, or emulsions or suspensions, particularly those from refineries. For example, emulsions known as MSAR (Multiphase Ultrafine Atomized Residue) are known to be used as fuels. These are essentially emulsions of heavy hydrocarbons such as bitumen, heavy fuel oil, or the like, and water, produced in specialized processes. Suspensions are well-known examples of pulverized coal and water suspensions, which are also used as fuels in large engines. Natural gas, such as LNG (Liquefied Natural Gas), is known as a gaseous fuel.

[0007] Another well-known alternative to pure operation using heavy fuel oil is to design large engines in a way that allows them to operate on two or more different fuels, where the engine operates using one fuel or another depending on the operating conditions or environment. Such large engines, also known as multi-fuel large engines, can switch during operation from a first mode burning the first fuel to a second mode burning the second fuel, and vice versa.

[0008] The well-known design of a large engine that can operate on two different fuels is the type of engine currently referred to as a "dual-fuel engine." On one hand, these engines can operate in gas mode, where a gaseous fuel, such as natural gas or methane, is introduced into the combustion chamber for combustion; on the other hand, they can operate in liquid mode, where a liquid fuel, such as heavy fuel oil or another liquid fuel, can be burned in the same engine. These large engines can be two-stroke and four-stroke engines, particularly longitudinally scavenged two-stroke large diesel engines.

[0009] Large engines are also known to operate on two different liquid fuels, typically both of which are stored, allowing the engine to operate on either the first or second fuel even during operation. Designs also exist in which both fuels are introduced into the combustion chamber during the same working cycle of the large engine.

[0010] Large engines that can operate on at least two or even more different liquid or gaseous fuels typically operate in different modes depending on the fuel currently in use. In an operating mode commonly referred to as diesel operation, combustion usually occurs based on the principle of compression ignition or auto-ignition. In a mode commonly referred to as Otto operation, combustion occurs by spark ignition of an ignitable fuel-air mixture. This spark ignition can be achieved, for example, by an electric spark, such as with a spark plug, or by auto-ignition of a small amount of fuel injected, which then ignites another fuel. In the case of the aforementioned dual-fuel engines, for example, the known gas mode mixes gaseous gas with scavenging air to create a combustible mixture in the combustion chamber of the cylinder. In this low-pressure process, ignition of the mixture in the cylinder is typically achieved by injecting a small amount of liquid fuel into the combustion chamber or pre-combustion chamber of the cylinder at an appropriate time, which then leads to the ignition of the air-fuel mixture.

[0011] In addition, hybrid forms of Otto operation and diesel operation are also known.

[0012] Furthermore, large engines designed as gas engines are known. These gas engines are designed solely for pure gas operation. For example, a gas engine can be designed such that its operation corresponds to that of a dual-fuel engine in gas mode. Gas engines typically operate under Otto mechanics. For example, natural gas is a preferred fuel for gas engines.

[0013] Within the framework of this application, the term "large diesel engine" refers to those engines capable of operating at least in diesel mode. In particular, the term "large diesel engine" therefore also includes dual-fuel or multi-fuel large engines that can operate in addition to diesel mode, such as Otto mode.

[0014] In large longitudinally scavenged engines, typically each cylinder has a scavenging air inlet and at least one outlet valve for exhausting exhaust gases. The scavenging air inlet is located at the lower end of the cylinder or cylinder liner, and the outlet valve is located at the upper end of the cylinder, for example, in the cylinder head. Fresh scavenging air or booster air is supplied to the combustion chamber of the cylinder through the scavenging air inlet, which is necessary for the combustion process. Normally, the scavenging air inlet of the cylinder is opened or closed by the movement of the piston. As the piston approaches bottom dead center during its working cycle and during its downward movement, the scavenging air inlet is released by the piston, allowing scavenging air or booster air to flow into the cylinder. During the subsequent upward movement of the piston, the piston closes the scavenging air inlet, so that no additional scavenging air can be introduced into the cylinder.

[0015] This means that during scavenging in the cylinder, fresh scavenging air flows into the cylinder through the scavenging air inlet, replacing the hot exhaust gases remaining in the cylinder from the previous combustion process. These exhaust gases are then discharged through the outlet valve. This scavenging process is usually not perfect, meaning that a certain amount of exhaust gas remains in the cylinder. The amount of this residual exhaust gas depends on the flow pattern or flow profile within the cylinder. There is also partial mixing of the hot exhaust gas with the fresh scavenging air, which heats the air in the cylinder that can be used for the next combustion process.

[0016] In particular, if a large engine operates in a gas mode where the premixed air-fuel mixture is spark-ignited in the combustion chamber, this heating of the air can lead to undesirable auto-ignition of the air-fuel mixture in the cylinder, which can result in very high mechanical loads and significantly increased emissions. Furthermore, the increased air temperature in the cylinder can have the effect of the spark-ignition combustion process running too quickly (rapid combustion), which also leads to high mechanical loads and high emissions.

[0017] Therefore, especially for the combustion of premixed air-fuel mixtures, it is essentially possible to control as much of the amount of exhaust gas remaining in the cylinder and the temperature of the scavenging air in the cylinder as possible, in order to ensure the most efficient and low-emission operation of large engines.

[0018] In large longitudinally scavenged engines, the flow profile is primarily determined by the scavenging air inlet and the outlet valve. While the arrangement and design of the scavenging air inlet can be optimized to a great extent, there is still a significant need to improve the exhaust outlet area. Currently, a common design for large longitudinally scavenged engines is to provide an outlet valve centrally located in the cylinder head. This centrally located outlet valve significantly reduces the exhaust gas velocity at the cylinder center, resulting in a considerable amount of exhaust gas accumulating below the outlet valve. Viewed across the cylinder cross-section, the flow velocity at the cylinder center is significantly lower than the flow velocity in the radially outer regions of the cylinder. Summary of the Invention

[0019] To address this issue, attempts have been made to incorporate multiple outlet valves in the longitudinally scavenging cylinder to create a more favorable flow profile that reduces the amount of exhaust gas remaining in the cylinder. However, there is still room for improvement.

[0020] Based on existing technology, the purpose of this invention is to provide a large engine with longitudinal scavenging that enables more reliable scavenging, wherein the amount of exhaust gas remaining in the cylinder can be better controlled and particularly reduced without significantly increasing the amount of scavenging air, so that the large engine can operate as economically as possible and with low emissions.

[0021] According to the present invention, a large longitudinally scavenged engine is thus proposed, the large longitudinally scavenged engine having at least one cylinder in which a piston is arranged to move back and forth along the cylinder axis, the cylinder having a cylinder head that, together with the piston, defines a combustion chamber for fuel, the large engine being designed to operate in a gas mode in which a premixed air-fuel mixture is burned in the combustion chamber, wherein a plurality of outlet valves are provided in the cylinder head for discharging exhaust gases from the combustion chamber, and wherein, in each case, a protrusion is provided on the cylinder head between two adjacent outlet valves, the protrusion extending into the combustion chamber.

[0022] The combination of multiple outlet valves and protrusions arranged therebetween creates a particularly advantageous flow profile within the cylinder, which significantly reduces the amount of exhaust gas remaining in the cylinder. Viewed across the cylinder's cross-section, the flow profile is significantly flatter or more uniform, meaning that regions with very low flow velocities are avoided or at least significantly reduced in the combustion chamber. Because the flow velocity across the cylinder cross-section is substantially uniform, exhaust gas is reliably discharged from all areas of the combustion chamber. Furthermore, the transition region between fresh scavenging air and exhaust gas is much narrower or smaller; that is, the transition from scavenging air to exhaust gas is more abrupt and less blurred. Consequently, heat transfer from exhaust gas to fresh scavenging air is also significantly reduced. This significantly more abrupt transition between fresh scavenging air and exhaust gas also allows for a better adaptation of the outlet valve closing time to this abrupt transition region, resulting in the discharge of more exhaust gas overall from the combustion chamber and the retention of more fresh scavenging air in the cylinder.

[0023] The significantly reduced heat transfer between the hot exhaust gas and the relatively cold purge air results in two additional advantages: on the one hand, the risk of undesirable self-ignition of the air-fuel mixture is significantly reduced, and on the other hand, the higher exhaust gas temperature improves the effectiveness or efficiency of downstream exhaust gas purification systems, such as methane oxidation catalysts or SCR devices (SCR: Selective Catalytic Reduction).

[0024] According to a preferred embodiment, the cylinder has four outlet valves arranged in the cylinder head.

[0025] Preferably, the four outlet valves are arranged in a rectangular structure.

[0026] To effectively reduce the low-flow-rate regions in the combustion chamber, it is advantageous that each protrusion extends radially toward the cylinder axis.

[0027] Preferably, each protrusion is designed such that the height of the protrusion, measured perpendicular to the radial direction, is reduced when viewed toward the cylinder axis.

[0028] Furthermore, preferably, each protrusion is designed such that the width of the protrusion, measured perpendicular to the radial direction, is reduced when viewed toward the cylinder axis.

[0029] For this purpose, preferably, each protrusion is designed to be essentially a tetrahedron, wherein, in each case, the base of the tetrahedron is arranged radially outward and the vertices of the tetrahedron are arranged radially inward, such that the protrusions are arranged such that their vertices face the cylinder axis.

[0030] In a preferred embodiment, an inspection device is provided that actuates multiple outlet valves to minimize the amount of residual exhaust gas in the combustion chamber.

[0031] Furthermore, in a preferred embodiment, each outlet valve has a valve axis, wherein at least one outlet valve is arranged such that its valve axis is aligned parallel to the cylinder axis.

[0032] In some implementations, each outlet valve is arranged such that its valve axis is aligned parallel to the cylinder axis.

[0033] In other embodiments, each outlet valve can be arranged such that its valve axis is angled relative to the cylinder axis. This means that the corresponding valve axis forms an angle greater than zero degrees and less than ninety degrees with the cylinder axis. From an aerodynamic point of view, this angled arrangement can be particularly advantageous.

[0034] Another preferred measure is that multiple outlet valves are arranged such that the outlet valves are arranged symmetrically about the cylinder axis.

[0035] Longitudinal scavenging large engines are preferably designed as longitudinal scavenging large diesel engines.

[0036] If the large longitudinally scavenged engine according to the present invention is designed as a large two-stroke engine with longitudinal scavenging, it is also preferred.

[0037] In particular, the large engine according to the invention can be designed as a longitudinally scavenging two-stroke large diesel engine.

[0038] Particularly preferably, the large engine is designed as a dual-fuel large diesel engine, which can operate in liquid mode, in which liquid fuel is introduced into the combustion chamber for combustion, and the dual-fuel large diesel engine can also operate in gas mode, in which gas is introduced into the combustion chamber as fuel. Attached Figure Description

[0039] The invention will now be explained in more detail with reference to embodiments and accompanying drawings. The drawings show:

[0040] Figure 1 This is a schematic cross-sectional view of an embodiment of a large engine with longitudinal scavenging according to the present invention.

[0041] Figure 2 This is a plan view of the cylinder head of this embodiment, viewed from the combustion chamber, and...

[0042] Figure 3 This is a three-dimensional cross-sectional view of the cylinder head. Detailed Implementation

[0043] Figure 1An embodiment of a large engine with longitudinal scavenging according to the present invention is shown in schematic cross-sectional view, and is generally indicated by reference numeral 1.

[0044] The large engine 1 includes at least one, but usually more, cylinders 10 in which the combustion process takes place.

[0045] The term "large engine" refers to an engine that is typically used as the main propulsion unit of a ship or for stationary operations, such as driving a large generator to produce electrical energy. Typically, the cylinders 10 of a large engine 1 have an inner diameter (cylinder bore) of at least approximately 200 mm.

[0046] The large engine 1 can be designed as a four-stroke or two-stroke engine. In particular, the large engine 1 can be designed as a large diesel engine, especially a longitudinally scavenged two-stroke large diesel engine. The term "large diesel engine" refers to such a large engine 1 that can operate under diesel operation. In an ideal, limiting condition, diesel operation is an isobaric process based on diffusion combustion (isobaric combustion). Under diesel operation, combustion of fuel typically occurs according to the principle of self-ignition. Within the framework of this application, the term "large diesel engine" also refers to those large engines 1 that can alternatively operate under Otto operation in addition to diesel operation. In an ideal, limiting condition, Otto operation is a common-space process (common-space combustion), where combustion typically occurs according to the principle of spark ignition of fuel. Large diesel engines can also operate in a hybrid form of diesel and Otto operation.

[0047] Of course, the term "large engine" also includes engines designed as gas engines. These gas engines are designed solely for pure gas operation; that is, they operate using only gaseous fuels such as natural gas. For example, a gas engine can be designed such that its operation corresponds to the operation of a dual-fuel engine in gas mode.

[0048] Furthermore, the term "spark-ignition fuel" is used to describe fuel that burns as intended in cylinder 10 via spark ignition, i.e., where self-ignition should be avoided as intended. Conversely, the term "self-ignition fuel" refers to fuel that burns as intended in cylinder 10 via self-ignition, such as heavy fuel oil or diesel fuel.

[0049] The term "liquid fuel" refers to fuel introduced into cylinder 10 in a liquid state. The term "gaseous fuel" refers to fuel introduced into cylinder 10 in a gaseous state.

[0050] In the following description of the invention, the case of a large diesel engine 1, which is of practical importance, is mentioned by way of example. This large diesel engine is designed as a longitudinally scavenged two-stroke large diesel engine 1 and is used as the main propulsion unit of a ship. This large diesel engine 1 can, for example, but is not required to, be designed as a dual-fuel large diesel engine, such that it can operate using two different fuels, for example, a liquid fuel such as heavy fuel oil and a gaseous fuel such as natural gas. The dual-fuel large diesel engine 1 can switch from burning the first fuel to burning the second fuel during operation, and vice versa.

[0051] It is understood that the present invention is not limited to this type of large diesel engine and this application, but generally relates to a large engine 1 with longitudinal scavenging. The large engine 1 can also be designed to burn only a single fuel. For example, the large engine 1 can be designed as a gas engine designed to operate only with gas as fuel. The large engine 1 can also be designed as a multi-fuel large engine, which can operate with a first fuel and can operate with at least a second fuel different from the first fuel. Of course, the large engine 1 can also be designed to burn more than two fuels.

[0052] In each case, a piston 60 is provided in each cylinder 10 of the large diesel engine 1. In each case, the piston 60 can move back and forth between an upper reversing point and a lower reversing point in the direction of the cylinder axis X, and its upper side, together with the cylinder head 20, defines the combustion chamber 120.

[0053] The piston 60 is connected to the crosshead (not shown) via a piston rod (not shown) in a manner known per se, and the crosshead is connected to the crankshaft (not shown) via a push rod (not shown), such that the movement of the piston 60 is transmitted to the crankshaft via the piston rod, crosshead and push rod to rotate the crankshaft.

[0054] In the cylinder head 20, a plurality of outlet valves 40 are provided, through which combustion gases can be discharged from the combustion chamber 120 of the cylinder 10 to an exhaust gas collection pipe (not shown) after the combustion process. Each outlet valve 40 extends in the direction of the corresponding valve axis A. In the embodiment described herein, four outlet valves 40 are provided in each cylinder 10 in each case. This is particularly useful in... Figure 2 As seen in the image, this is a plan view of the cylinder head 20 as viewed from the combustion chamber 120. For better understanding, Figure 3 A three-dimensional cross-sectional view of the cylinder head 20 is still shown.

[0055] However, in Figure 2 and Figure 3For better understanding, only cylinder bores 401 are shown, each receiving an outlet valve 40, but not the outlet valves 40 themselves. If an outlet valve 40 is arranged in a corresponding cylinder bore 401, the corresponding valve axis A lies on the corresponding central axis of the cylinder bore 401 in which the outlet valve 40 is arranged.

[0056] In other embodiments, each cylinder 10 may be provided with fewer or more than four outlet valves 40, such as two or three outlet valves or five or more outlet valves.

[0057] To achieve optimal exhaust gas emission from the combustion chamber 120, it is preferable that the multiple outlet valves 40 are arranged symmetrically about the cylinder axis X. For example... Figure 2 As specifically shown, the four outlet valves 40 are arranged in a rectangular structure, and more particularly a square structure. The valve axis A or the central axis of the four cylinder bores 401 is arranged such that the point where they enter the combustion chamber 120 lies on a rectangle, in this case a square, whose center is penetrated by the cylinder axis X.

[0058] In the embodiments described herein, the outlet valve 40 is arranged such that the cylinder bore 401 is designed such that each valve axis A is arranged parallel to the cylinder axis X. In other embodiments, one or more valve axes may extend obliquely to the cylinder axis. Thus, each valve axis extending obliquely relative to the cylinder axis preferably forms an angle greater than 0° and less than 90° with the cylinder axis.

[0059] In a longitudinally scavenging two-stroke large diesel engine 1, scavenging air openings 30, designed as scavenging air slots, are provided in the lower region of each cylinder 10 or cylinder liner in each case for supplying scavenging air to the cylinder 10. The scavenging air openings 30 are periodically closed and opened by the movement of the piston 60 within the cylinder 10, allowing scavenging air supplied by the turbocharger (not shown) in the intake receiver (not shown) under boost pressure to flow through the scavenging air openings 30 into the corresponding cylinder 10, provided these scavenging air openings are open. This is the case when the corresponding piston 60 is in the region of its lower reverse point.

[0060] Furthermore, at least one fuel injection nozzle 50 is disposed in the cylinder head 20. In the embodiment described herein, the fuel injection nozzle is centrally arranged in the cylinder head 20 such that the central axis of the fuel injection nozzle 50 is located on the cylinder axis X. Of course, in other embodiments, more than one fuel injection nozzle 50 may be provided for each cylinder 10.

[0061] The fuel injection nozzle 50 is used to introduce liquid fuel, such as heavy fuel oil or diesel, into the combustion chamber 120 of the cylinder 10, which means that in liquid mode, liquid fuel is injected into the combustion chamber 120 of the cylinder 10 by means of the fuel injection nozzle 50.

[0062] In addition, a gas supply system (not shown) is provided, which allows gas to be introduced into cylinder 10. This gas supply system is preferably designed as a low-pressure system, introducing fuel gas into the cylinder at a pressure of up to 50 bar (5 MPa), preferably up to 20 bar (2 MPa). The gas supply system includes at least one gas inlet nozzle disposed on or within the cylinder wall. Relative to the cylinder axis X, the gas inlet nozzle is preferably disposed approximately midway between the upper and lower reversing points of piston 60.

[0063] In gas mode, gas is introduced into cylinder 10 by means of a gas supply system, mixed with scavenging air, and compressed by the upward movement of piston 60. In this case, a premixed air-fuel mixture is generated in combustion chamber 120, which is then spark-ignited at a predetermined time or at a predetermined crank angle. Spark ignition preferably occurs by injecting a small amount of liquid fuel into combustion chamber 120 or a pre-combustion chamber (not shown) of cylinder 10 at an appropriate time, causing the liquid fuel in combustion chamber 120 or pre-combustion chamber to self-ignite, which then leads to the ignition of the air-gas mixture in combustion chamber 120. Multiple pre-combustion chambers can be arranged in a manner known per se, each in fluid communication with combustion chamber 120. If self-igniting fuel is subsequently introduced into each of these chambers, the air-fuel mixture in combustion chamber 120 can be spark-ignited at different points.

[0064] Instead of spark ignition by introducing self-igniting fuel, spark ignition can also be achieved by means of electric ignition, such as spark plugs.

[0065] The details of other structures and components of large diesel engines, such as injection systems, gas exchange systems, exhaust systems, or turbocharger systems for providing scavenging or boosting air, as well as inspection and control systems for large diesel engines, are well known to those skilled in the art in terms of whether they are designed as two-stroke or four-stroke engines, and therefore need not be described further here.

[0066] The inspection and control system in modern large diesel engines is an electronic system, which typically regulates, controls, or adjusts all engine or cylinder functions, particularly injection (initiation and termination of injection), gaseous fuel introduction, and actuation of outlet valves. In the embodiment described herein, the inspection and control system includes an inspection device by which each outlet valve 40 can be actuated to open or close. Preferably, the inspection device actuates all outlet valves 40 simultaneously, i.e., synchronously, such that all outlet valves 40 move as synchronously as possible.

[0067] Alternatively, the inspection device can actuate each outlet valve 40 individually and independently of the other outlet valves 40.

[0068] According to the invention, in each case, protrusions 7 are provided on the cylinder head 20 between two adjacent outlet valves 40 or between two adjacent cylinder bores 401 for the outlet valves 40. These protrusions 7 help to significantly improve the flow profile in the cylinder 10. The combination of multiple outlet valves 40 and corresponding protrusions 7 arranged therebetween results in at least a significant reduction in areas or stagnant areas with very low flow velocities. The flow velocity distribution across the cross-section of the cylinder 10 becomes more uniform. This means that the flow profile becomes flatter. Exhaust gas can be reliably discharged from all areas of the combustion chamber 120. This also results in a significantly narrower and therefore smaller transition zone between fresh scavenging air and exhaust gas in the cylinder. The transition from fresh scavenging air to exhaust gas is significantly more abrupt, resulting in reduced heat exchange between the hot exhaust gas and the cooler scavenging air. Compared to conventional embodiments, this means that the exhaust gas remains hotter, which is advantageous for the efficiency of downstream exhaust gas purification systems, and that the scavenging air in the cylinder 10 remains cooler, which is a positive effect against undesirable self-ignition or excessively rapid combustion, especially in gas mode.

[0069] A total of four protrusions 7 extend from the cylinder head 20 into the combustion chamber 120 in each case, and each of the protrusions is arranged between two adjacent outlet valves 40 or between two adjacent cylinder bores 401. According to a preferred embodiment, each protrusion 7 extends radially from the cylinder head 20 toward the cylinder axis X.

[0070] Each protrusion 7 is designed such that its height H decreases from the cylinder head 20 in the direction of the cylinder axis X, that is, the height H is greatest at the cylinder head 20, especially in the radially outer region of the cylinder head 20, and then decreases, preferably continuously, wherein the height H represents the extension in the direction of the cylinder axis X.

[0071] Furthermore, in this preferred embodiment, the width B of each protrusion 7 decreases in the direction of the cylinder axis X. Width B represents the extension of the protrusion in a direction perpendicular to both the radial direction and the cylinder axis X. This direction is approximately circumferential. Therefore, the width B of each protrusion 7 is greatest at the cylinder head 20, particularly in the radially outer region of the cylinder head, and then decreases, preferably continuously.

[0072] For example, by the fact that each protrusion 7 is essentially designed as a tetrahedron, i.e., composed of four triangles, two geometric conditions can be achieved, which, of course, cannot be understood in a strictly mathematical sense. In each case, the base of the tetrahedron is arranged radially outward on the cylinder head 20, and the vertices of the tetrahedron are arranged radially inward, such that the protrusions 7 are arranged so that their vertices face the cylinder axis. Preferably, one "edge" of the corresponding tetrahedron extends in the radial direction.

Claims

1. A large longitudinally scavenged engine having at least one cylinder (10) in which a piston (60) is arranged to reciprocate along a cylinder axis (X), the cylinder having a cylinder head (20) that, together with the piston (60), defines a combustion chamber (120) for fuel, the large engine being designed to operate in a gas mode in which a premixed air-fuel mixture is burned in the combustion chamber (120), wherein a plurality of outlet valves (40) are provided in the cylinder head (20) for discharging exhaust gases from the combustion chamber (120), characterized in that, A protrusion is provided on the cylinder head (20) between two adjacent outlet valves (40), the protrusion extending into the combustion chamber (120) to achieve a flow profile in the cylinder. By avoiding or reducing areas with low flow rates in the combustion chamber (120), the amount of exhaust gas remaining in the cylinder can be reduced, thereby exhaust gas is discharged from all areas of the combustion chamber and heat transfer from the exhaust gas to fresh scavenging air is reduced.

2. The large engine with longitudinal scavenging according to claim 1, wherein, The cylinder (10) has four outlet valves (40) arranged in the cylinder head (20).

3. The large engine with longitudinal scavenging according to claim 2, wherein, The four outlet valves (40) are arranged in a rectangular structure.

4. A large engine with longitudinal scavenging according to any one of claims 1 to 3, wherein, Each protrusion (7) extends radially toward the cylinder axis (X).

5. The large engine with longitudinal scavenging according to claim 4, wherein, Each protrusion (7) is designed such that when viewed toward the cylinder axis (X), the height (H) of the protrusion, measured perpendicular to the radial direction, decreases, and the height of the protrusion is greatest in the radially outer region of the cylinder head and then decreases.

6. The large engine with longitudinal scavenging according to claim 4, wherein, Each protrusion (7) is designed such that when viewed toward the cylinder axis (X), the width (B) of the protrusion, measured perpendicular to the radial direction, decreases, and the width of the protrusion is greatest in the radially outer region of the cylinder head, and then decreases.

7. A large engine with longitudinal scavenging according to any one of claims 1 to 3, wherein, Each protrusion (7) is essentially designed as a tetrahedron, wherein the base of each tetrahedron is arranged radially outward and the vertices of the tetrahedron are arranged radially inward, such that the protrusions (7) are arranged such that their vertices face the cylinder axis (X).

8. A large engine with longitudinal scavenging according to any one of claims 1 to 3, wherein, An inspection device is provided that actuates the plurality of outlet valves (40) to minimize the amount of exhaust gas remaining in the combustion chamber (120).

9. A large engine with longitudinal scavenging according to any one of claims 1 to 3, wherein, Each outlet valve (40) has a valve axis (A), and at least one outlet valve (40) is arranged such that its valve axis (A) is aligned parallel to the cylinder axis (X).

10. The large engine with longitudinal scavenging according to claim 9, wherein, Each outlet valve (40) is arranged such that its valve axis (A) is aligned parallel to the cylinder axis (X).

11. A large engine with longitudinal scavenging according to any one of claims 1 to 3, wherein, The plurality of outlet valves (40) are arranged such that the outlet valves (40) are arranged symmetrically about the cylinder axis (X).

12. The longitudinally scavenged large engine according to any one of claims 1 to 3, wherein the longitudinally scavenged large engine is designed as a longitudinally scavenged large diesel engine.

13. The longitudinally scavenged large engine according to any one of claims 1 to 3, wherein the longitudinally scavenged large engine is designed as a longitudinally scavenged two-stroke large engine.

14. The longitudinally scavenged large engine according to any one of claims 1 to 3, wherein the longitudinally scavenged large engine is designed as a longitudinally scavenged two-stroke large diesel engine.

15. The longitudinally scavenged large engine according to any one of claims 1 to 3, wherein the longitudinally scavenged large engine is designed as a dual-fuel large diesel engine, the dual-fuel large diesel engine being capable of operating in a liquid mode in which liquid fuel is introduced into the combustion chamber (120) for combustion, and the dual-fuel large diesel engine also being capable of operating in a gas mode in which gas is introduced into the combustion chamber (120) as fuel.

Images