Longitudinal scavenging large engine

Abstract

To further accurately control a quantity of scavenging air, in a longitudinal scavenging-type crosshead large-sized engine.SOLUTION: An engine comprises cylinders 10 having cylinder liners 5, and cylinder sections 4 having bottom parts 3. A plurality of the cylinder liners are arranged while being aligned in the cylinder sections in a longitudinal direction A. Pistons are arranged in the cylinder liners 5, respectively. A scavenging air opening part 7 is formed while adjoining end parts 51 of the cylinder liners 5, and the scavenging air from a scavenging air receiver 8 is thereby made to flow therein. Piston sub-spaces 11 which are defined by lower faces of the pistons of the cylinders 10 at one side, and defined by the bottom parts 3 of the cylinder sections 4 at the other side are formed for the cylinders 10. A separation wall 12 is arranged so as to separate the adjoining piston sub-spaces 11 from each other. The piston sub-spaces 11 are connected to the scavenging air receiver 8 via a flow connection part 13.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a longitudinally scavenged large engine according to the preamble of the independent patent claims in each category.

Background Art

[0002] [[ID=1--12]]Large engines, which can be designed as two-stroke or four-stroke engines, for example as longitudinally scavenged two-stroke large diesel engines, are often used as marine drive units or in stationary operation, for example to drive large generators for generating electrical energy. This type of engine usually operates in continuous operation for a fairly long period of time, and thus high requirements are placed on operational safety and availability. As a result, in particular, increasing the maintenance intervals, reducing wear, and economically handling the operating materials are central criteria for the operator. Large engines typically have cylinders with an inner diameter (bore) of at least 200 mm. Currently, large engines with bores up to 960 mm or even more are also in use.

[0003] For several years, energy efficiency and the quality of exhaust gases have become another important issue, especially in terms of the concentration of nitrogen oxides or sulfur load in the exhaust gases. Another issue is unburned hydrocarbons such as methane slip.

[0004] Here, the legal requirements and limits regarding the corresponding emission thresholds are becoming increasingly strict. As a result, especially in the case of two-stroke large diesel engines, not only the combustion of conventional heavy fuel oil, which is significantly contaminated with pollutants, but also the combustion of other fuels such as diesel oil or natural gas has become a problem. The reason is that compliance with the emission thresholds is becoming increasingly difficult and technically complex, and thus more costly.

[0005] For economical and efficient operation, compliance with exhaust gas thresholds and the availability of alternative resources to heavy fuel oils conventionally used as fuel in large engines are also required. In this regard, both liquid fuels, i.e., fuels introduced into the combustion chamber in liquid form, and gaseous fuels, i.e., fuels introduced into the combustion chamber in gaseous form, are used.

[0006] Known examples of liquid fuels as alternatives to heavy fuel oil include other heavy hydrocarbons remaining from petroleum refining, alcohols, particularly methanol or ethanol, gasoline, diesel, or emulsions or suspensions. For example, emulsions, known as MSAR (Multiphase Ultrafine Atomized Residue), are known to be used as fuel. These are essentially emulsions produced in special processes from heavy hydrocarbons, such as bitumen, heavy fuel oil, or similar substances, and water. A well-known suspension is that of coal dust and water, which is also used as fuel for large engines. Natural gas, such as LNG (Liquefied Natural Gas), is known as a gaseous fuel.

[0007] Another well-known alternative to pure operation with heavy fuel oil is to design a large engine to be able to operate on two or more different fuels, in which case the engine will operate on one fuel or the other depending on the operating conditions or environment. Such a large engine, also called a multi-fuel large engine, can be switched during operation from a first mode in which a first fuel is burned to a second mode in which a second fuel is burned, and vice versa.

[0008] A known design of a large engine that can operate on two different fuels is the type of engine for which the term “dual-fuel engine” is currently used. On the 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, and on the other hand, 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 both two-stroke and four-stroke engines, and in particular, they can be longitudinal scavenging two-stroke large diesel engines.

[0009] Furthermore, large engines are known that can be operated on two different liquid fuels, in which case both fuels are usually stockpiled, allowing the engine to be operated on either the first or second fuel even while in operation. Designs are also known in which both fuels are introduced into the combustion chamber during the same operating cycle of the large engine.

[0010] Large engines capable of operating on at least two or more different liquid or gaseous fuels are often operated in different operating modes depending on the fuel being used. In the operating mode often called diesel operation, combustion of the fuel is usually carried out according to the principle of compression ignition or autoignition of the fuel. In the mode often called Ott operation, combustion is carried out by spark ignition of the ignitable fuel-air mixture. This spark ignition can also be achieved, for example, by an electric spark, for example using a spark plug, or by causing a small amount of fuel introduced to autoignite, thereby triggering spark ignition of another fuel. In the case of the dual-fuel engines described above, for example, in gas mode, it is known that gaseous gas is mixed with scavenging air to create an ignitable mixture in the combustion chamber of the cylinder. In this low-pressure process, ignition of the mixture in the cylinder is usually carried out by introducing a small amount of liquid fuel into the combustion chamber or pre-chamber of the cylinder at the right moment, thereby causing ignition of the air-gas mixture.

[0011] Furthermore, hybrid forms derived from both Ott and Diesel operation are also known.

[0012] In addition, large engines designed as gas engines are known. These gas engines are designed to operate only with high-purity gases. For example, a gas engine may be designed so that its operation corresponds to that of a gas-mode dual-fuel engine. Gas engines typically operate in Otto mode. A preferred fuel for gas engines is, for example, natural gas.

[0013] Within the framework of this application, the term “large diesel engine” refers to an engine that can be operated by at least diesel operation. The term “large diesel engine” therefore also includes, in particular, dual-fuel or multi-fuel large engines that can be operated not only by diesel operation but also by another operation, such as Otto operation.

[0014] Large engines are often designed with a crosshead configuration, typically having three large assemblies: a base plate with transverse support elements in addition to a bearing saddle with crankshaft main bearings for receiving the crankshaft. A so-called stand is positioned on the base plate, separated by a bottom plate. The stand has multiple support bodies corresponding to the number of cylinders in the large diesel engine, each having two vertically extending sliding surfaces for guiding two adjacent crossheads connected to the crankshaft via push rods. Towards the top, the stand is covered by a cover sheet, which simultaneously forms the bottom of the cylinder section, within which the cylinder liners of the cylinders are arranged side by side in the longitudinal direction.

[0015] In large longitudinal scavenging engines, each cylinder liner typically has a scavenging air opening located at the lower end of the cylinder liner. Each cylinder has at least one outlet valve for releasing exhaust gases, the outlet valve located at the upper end of the cylinder, for example, within the cylinder cover. Fresh scavenging air or filling air required for the combustion process is delivered into the combustion chamber of the cylinder through the scavenging air opening. Typically, the scavenging air opening of the cylinder is opened and closed by the movement of the piston. As the piston approaches bottom dead center during the operating cycle and its downward movement, the scavenging air opening in the cylinder liner is opened by the piston, thereby allowing scavenging air or filling air to flow into the cylinder. Then, during the subsequent upward movement of the piston, the piston closes the scavenging air opening, thereby preventing any further scavenging air from being introduced into the cylinder.

[0016] Cylinder liners are typically arranged side-by-side longitudinally within a cylinder section and terminate above the bottom of the cylinder section. All cylinder liners terminate within a common space of the cylinder section, which is often also designed as a piston subspace. The piston subspace is defined at its lower end by the bottom of the cylinder section and at its upper end by the underside of the piston or the wall of the cylinder section; that is, the piston subspace includes an internal volume within the cylinder liner and an external volume within the cylinder liner.

[0017] Due to the common piston subspace, the scavenging air openings of all these cylinder liners, where the piston is currently positioned above the scavenging air opening, are flow-connected. This is because all of these openings are located within the common piston subspace and below their respective pistons.

[0018] At least one scavenging air receiver, typically also referred to as an inlet receiver, is provided laterally adjacent to the common piston subspace. The scavenging air receiver typically extends longitudinally along all cylinders and contains scavenging air or filling air. Scavenging air is delivered into the scavenging air receiver by a turbocharger via a filling air cooler, where it is available at an adjustable filling pressure. There is at least one scavenging air receiver, but typically several, connected to the common piston subspace via flow couplings, so that as soon as each piston opens its scavenging air slot during its downward movement, scavenging air can flow into each cylinder. During its subsequent upward movement, the piston then closes the scavenging air slot again, so that no more scavenging air can flow into the cylinder, and as soon as the outlet valve of that cylinder is closed, the compression process begins.

[0019] Each piston movement can cause pressure fluctuations or even pressure pulsations within the piston subspace, which can also propagate into the scavenging air receiver. As a result, the scavenging airflow entering each cylinder liner is often not perfectly uniform and is subject to fluctuations. Therefore, it is not possible to adjust the mass of air introduced into the cylinder with very high precision in each operating cycle.

[0020] In particular, when large engines operate in gas mode, where a pre-mixed air-fuel mixture is spark-ignited in the combustion chamber, such inaccuracies in the amount of scavenging air introduced can lead to an uncontrolled or abnormal combustion process.

[0021] If the gas content is too high or the air content is too low, the air-fuel mixture becomes too rich. This can lead to undesirable self-ignition of the air-fuel mixture in the cylinder, for example, which can result in very high mechanical load and a significant increase in emissions. Furthermore, an incorrect ratio in the air-fuel mixture can lead to the spark-ignition combustion process operating too quickly (fast combustion), which also results in high mechanical load and high emissions. If the air content is too high, the air-fuel mixture becomes too lean, which can lead to misfires, and this is also, of course, detrimental to engine efficiency and low-emission operation.

[0022] When plotting the torque generated by a large diesel engine against the air-fuel ratio for a given load, the limit between high-quality combustion and abnormal combustion is given, for example, by two limit curves, namely the knocking limit and the misfire limit, thereby high-quality combustion lies between these two limit curves. [Overview of the project] [Problems that the invention aims to solve]

[0023] Therefore, starting from the current state of the prior art, the object of the present invention is to propose a longitudinal scavenging crosshead large engine that can control, in particular adjust with greater precision the amount of scavenging air introduced into the cylinder liner, in order to operate the large engine as economically as possible and with the emission value reduced. [Means for solving the problem]

[0024] The subject matter of the present invention, which satisfies this objective, is characterized by the features of the independent patent claims.

[0025] Accordingly, according to the present invention, a longitudinal scavenging crosshead large engine comprises a plurality of cylinders, each having a cylinder liner, and a cylinder section defined by a bottom, wherein cylinder liners are arranged adjacent to each other in the longitudinal direction, each cylinder liner having a piston that extends from a first end facing the bottom to a second end facing the combustion chamber of the cylinder and is arranged to be movable back and forth, and a plurality of scavenging air openings are provided in each cylinder liner adjacent to the first end of each cylinder liner, and these A longitudinal scavenging crosshead large engine is proposed, in which scavenging air from a scavenging air receiver can flow into each cylinder liner through a scavenging air opening, a piston subspace is provided for each cylinder, the piston subspace is defined on the one hand by the underside of the piston of the cylinder and on the other hand by the bottom of the cylinder section, a separation wall is provided in the longitudinal direction between two adjacent piston subspaces in either case, this separation wall separates these two piston subspaces from each other, and each piston subspace is connected to a scavenging air receiver via a flow coupling.

[0026] The essential aspect of this invention is to provide each cylinder with its own individual piston subspace, rather than a common piston subspace to which all cylinder liners terminate, with a separation wall in each case between two longitudinally adjacent individual piston subspaces, which prevents scavenging air from one piston subspace from flowing directly into the longitudinally adjacent piston space. Each of these individual piston subspaces is connected to a scavenging air receiver via an individual flow coupling. This method makes it possible to adjust with even greater precision the amount of scavenging air flowing into each cylinder liner with each operating cycle. Thus, the air-fuel ratio of the air-fuel mixture can be adjusted with even greater precision, thereby enabling a high-quality combustion process, particularly in gas mode with spark ignition.

[0027] Preferably, a flow control element is provided within each flow connection section, and this flow control element can adjust the scavenging air flow passing through the flow connection section. Thus, for example, the free flow cross-section within each flow connection section can be adjusted individually for each cylinder, whereby the amount of air introduced into each cylinder for each working cycle can also be adjusted with very high precision.

[0028] According to a preferred embodiment, the flow control element is designed as a throttle or valve, particularly as a flap valve.

[0029] Furthermore, it is a preferred measure that the flow control element is designed as a backflow prevention device for preventing the backflow of scavenging air into the scavenging air receiver. Thus, the scavenging air can flow in only one direction, that is, only in the direction of the individual piston sub-spaces. In this way, in particular, the pressure fluctuations or pressure pulsations within the scavenging air receiver can be at least reduced.

[0030] Designing the flow control element as a pilot valve is a preferred embodiment.

[0031] Particularly preferably, the flow control element is designed as an operable valve, whereby the free flow cross-section within each flow connection section can be adjusted or changed, especially during the operation of a large engine. In this way, for example, the amount of air flowing into each cylinder for each working cycle can be adjusted according to the changed environmental conditions such as air temperature or air humidity, or the amount of air can be adjusted according to the load under which the large engine is operated thereby.

[0032] Preferably, a control device is provided for this purpose, which can control or adjust the scavenging airflow in each of the flow couplings. In the case of adjustment, for example, another parameter that is characteristic of the combustion process in each cylinder, such as the air-fuel ratio, ignition pressure, internal cylinder pressure, or even the ignition rate, can be provided as a control variable. In the case of control, for example, a lookup table can be provided for such or other variables, in which the values ​​to be adjusted are stored according to one or more operating parameters. In this way, it is possible to individually adjust the scavenging airflow from the scavenging air receiver into the cylinder for each cylinder.

[0033] Preferably, each scavenging airflow can be controlled or adjusted according to the operating parameters of the large engine. Particularly suitable such operating parameters are the load on which the large engine is driven, and / or the torque generated, and / or the rotational speed of the large engine.

[0034] A further preferred measure is to provide at least one connecting pipe that connects the piston subspace of the first cylinder to the piston subspace of the second cylinder. In this way, a larger pressure difference between the piston subspace of one first cylinder and the piston subspace of the other second cylinder can be compensated for. Thus, for example, it is possible to relieve the pressure on the lower surface of the piston in one cylinder in order to facilitate the downward movement of the piston in that cylinder.

[0035] In this case, the two individual piston subspaces connected by the connecting pipe are preferably selected such that the piston of the first cylinder and the piston of the second cylinder have a crank angle difference of at least 90°. In particular, the pistons of the first and second cylinders can have a crank angle difference of about 180°. For example, the piston of the first cylinder may be straight at the upper reversal point when the piston of the second cylinder is straight at the lower reversal point.

[0036] In this embodiment, it may also be advantageous to provide a control element that can adjust the flow through the connecting pipe.

[0037] Furthermore, it may be advantageous to provide a damping element within the connecting pipe that can reduce pressure pulsations.

[0038] In particular, in embodiments where the flow control element is designed as a backflow prevention device in the flow coupling between the scavenging air receiver and the individual piston subspaces, it may also be advantageous to provide a cooling device for the piston subspaces. Compression of the air in each piston subspace can cause an increase in the temperature of the enclosed air, for example, during the downward movement of each piston, which results in a temperature increase that is then addressed by the cooling device.

[0039] In particular, a longitudinal scavenging crosshead large engine can be designed as a two-stroke large diesel engine.

[0040] Particularly preferably, the large engine is designed as a dual-fuel large diesel engine that can operate in liquid mode, where liquid fuel is introduced into the combustion chamber for combustion, and can also operate in gas mode, where gas is introduced into the combustion chamber as fuel.

[0041] Further advantageous measures and embodiments of the present invention can be obtained from the dependent claims.

[0042] The present invention will be described in more detail below based on examples and figures. [Brief explanation of the drawing]

[0043] [Figure 1] This is a schematic cross-sectional view of an embodiment of a longitudinal scavenging type large engine according to the present invention, in a section perpendicular to the longitudinal direction. [Figure 2] This is a schematic cross-sectional view of an embodiment in a section along the longitudinal direction. [Modes for carrying out the invention]

[0044] Figure 1 is a schematic cross-sectional view of an embodiment of the longitudinal scavenging crosshead large engine according to the present invention, indicated by reference numeral 1. The cross-section is perpendicular to the longitudinal direction A, defined by the direction in which the crankshaft of the large engine 1 extends. Figure 2 is a schematic cross-sectional view of this embodiment in a cross-section along the longitudinal direction A.

[0045] A large engine 1 has at least one, but usually multiple, cylinders 10, within which the combustion process takes place. In Figure 2, four cylinders are shown by exemplary symbols. Each cylinder 10 has a cylinder liner 5, within which a piston (not shown) is positioned in a manner known to itself, and the piston is positioned to move forward and backward in the direction of the cylinder axis between an upper reversal point and a lower reversal point, and its upper side, together with a cylinder cover (not shown), defines a combustion chamber (not shown). In all cases, the cylinder axis is perpendicular to the longitudinal direction A.

[0046] The term "large engine" typically refers to an engine used as the main propulsion unit for a ship, or in stationary operation to drive, for example, a large generator for generating electrical energy. Typically, each of the cylinders 10 of a large engine 1 has an internal bore of at least about 200 mm.

[0047] The large engine 1 may be designed as a four-stroke or two-stroke engine. In particular, the large engine 1 may be designed as a large diesel engine, specifically as a longitudinal scavenging two-stroke large diesel engine designed in a crosshead design.

[0048] The term "large diesel engine" refers to a large engine 1 that can be operated by diesel operation. In the ideal, limited case, diesel operation is an isobaric process based on diffusion combustion (isobaric combustion). In diesel operation, the combustion of fuel usually occurs according to the principle of autoignition. Within the framework of this application, the term "large diesel engine" also alternatively refers to a large engine 1 that can be operated by Ott operation in addition to diesel operation. In the ideal, limited case, Ott operation is a common space process (common space combustion), where combustion typically occurs according to the principle of spark ignition of fuel. It is also possible to operate a large diesel engine in a hybrid form of diesel operation and Ott operation.

[0049] Naturally, the term "large engine" also includes engines designed as gas engines. These gas engines are designed for high-purity gas operation only; that is, they operate solely on gaseous fuels, such as natural gas. For example, a gas engine may be designed so that its operation corresponds to that of a dual-fuel engine in gas mode.

[0050] Furthermore, the term "spark-ignited fuel" is used to refer to a fuel that burns as intended by spark ignition within cylinder 10; that is, self-ignition must be avoided as intended. In contrast, the term "self-igniting fuel" refers to a fuel that burns as intended by self-ignition within cylinder 10, such as heavy fuel oil or diesel fuel.

[0051] 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.

[0052] In the following description of the present invention, the case of a large diesel engine 1 designed as a longitudinal scavenging crosshead two-stroke large diesel engine 1 and used as the main drive unit of a ship will be referred to by exemplary features that are important in practice. This large diesel engine 1 can be designed, for example, as a dual-fuel large diesel engine, which is not necessarily required, so that the engine can be operated on two different fuels, such as a liquid fuel such as heavy fuel oil and a gaseous fuel such as natural gas. The dual-fuel large diesel engine 1 can be switched during operation from the combustion of the first fuel to the combustion of the second fuel and vice versa.

[0053] It is understood that the present invention is not limited to this type of large diesel engine and its use, but relates to longitudinal scavenging large engines 1 in general. It is also possible to design the large engine 1 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. It is also possible to design the large engine 1 as a multi-fuel large engine that can operate with a first fuel and can operate with at least a second fuel different from the first fuel.

[0054] Naturally, it is also possible to design a large engine 1 to accommodate the combustion of three or more fuels.

[0055] The large diesel engine 1 is designed in a crosshead design and has three large housing segments that form the frame of the large engine 1. A so-called stand 2 is positioned on a base plate (not shown) which has transverse support elements in addition to bearing saddles with crankshaft main bearings for receiving the crankshaft, separated by a bottom plate (not shown). The stand 2 has a plurality of support bodies corresponding to the number of cylinders of the large diesel engine 1, and each support body has two vertically extending sliding surfaces for guiding two adjacent crossheads connected to the crankshaft by push rods. Here, the two opposing vertical pivot surfaces are in each case additionally supported by a central wall.

[0056] The individual support bodies are typically connected by a common cover sheet that forms the bottom 3 of the cylinder section 4. The cylinder section 4 has a cylinder 10 with cylinder liners 5 arranged adjacent to each other in the longitudinal direction A. The base plate, stand 2, and cylinder section 4 are connected to each other by tie rods (not shown) which are screwed into or onto the base plate with considerable pre-tension.

[0057] In each case, the piston of each cylinder 10 is connected to a crosshead (not shown) by a piston rod 6 in a manner known to itself. The piston rod is connected to a crankshaft (not shown) by a push rod (not shown), thereby the movement of each piston is transmitted to the crankshaft via the piston rod 6, the crosshead, and the push rod, causing it to rotate.

[0058] The cylinder liners 5 are arranged adjacent to each other in the longitudinal direction A, in which case each cylinder liner 5 extends from a first end 51 facing the bottom 3 to a second end (not shown) facing the combustion chamber of the cylinder 10. Adjacent to the first end 51 of each cylinder liner 5, a number of scavenging air openings 7, designed, for example, as scavenging air slots, are provided within the cylinder liner 5, and scavenging air from the scavenging air receiver 8 can flow into each cylinder liner 5 through these openings.

[0059] Each of the scavenging air openings 7 is periodically closed and opened by the movement of the piston in the cylinder 10, thereby allowing scavenging air, provided by a turbocharger (not shown) in the scavenging air receiver 8 and below the charging pressure, to flow through the scavenging air openings 7 into each cylinder 10, insofar as the scavenging openings are flow-connected to the combustion chambers of each cylinder 10 by the position of the piston. This is the case when each piston is within the region of its lower inversion point.

[0060] Within the cylinder cover (not shown), which includes the second end of the cylinder liner 5, at least one fuel injection nozzle (not shown) is provided for each cylinder 10, and this injection nozzle is, for example, centrally located within the cylinder cover for each cylinder 10, and through this nozzle, liquid fuel is introduced into the combustion chamber of each cylinder 10 in liquid mode.

[0061] Furthermore, a gas supply system (not shown) is provided, which allows gas to be introduced into the cylinder 10 as fuel in gas mode. The gas supply system is preferably designed as a low-pressure system and introduces the gas to act as fuel into each cylinder 10 at a maximum of 50 bar (5 MPa), preferably a maximum of 20 bar (2 MPa). The gas supply system has at least one, preferably more, gas inlet nozzles, which are located on or within the wall of each cylinder liner 5. In gas mode, the gas is introduced into each cylinder 10 by the gas supply system, where it is mixed with scavenging air and compressed by the upward movement of the piston. In this way, a pre-mixed air-fuel mixture is created in the combustion chamber and then spark-ignited at a predetermined time or predetermined crank angle. Spark ignition is preferably achieved by introducing a small amount of liquid or gaseous fuel into the combustion chamber or pre-chamber (not shown) of cylinder 10 at the correct moment to cause the liquid or gaseous fuel in the combustion chamber or pre-chamber to self-ignite, which then leads to ignition of the air-gas mixture in the combustion chamber. Multiple pre-chambers can be provided in a manner known to itself, each flow-connected to the combustion chamber. If self-igniting fuel is then introduced into each of these chambers, the air-fuel mixture in the combustion chamber can be spark-ignited at various points in time.

[0062] Further details of the structure and individual components of large diesel engines, such as the input system, gas exchange system, exhaust system, or turbocharger system for providing scavenging or charging air, and the check and control system for large diesel engines, are well known to those skilled in the art in both two-stroke and four-stroke engine designs, and therefore no further explanation is needed here.

[0063] In modern large diesel engines, the check and control system is an electronic system that can typically adjust, control, or regulate all engine or cylinder functions, particularly the feeding (start and end of feeding), the introduction of gaseous fuel, and the operation of the outlet valves. In the embodiment described herein, the check and control system has a control device 9 that can control or regulate the supply of scavenging air to the cylinder 10, which will be described in more detail.

[0064] A piston subspace 11 is provided for each individual cylinder 10, and the piston subspace is defined on the one hand by the lower surface of the piston of this cylinder 10 facing outward from the combustion chamber, and on the other hand by the bottom 3 of the cylinder section 4. This piston space 11 includes both a volume located inside the associated cylinder liner 5, i.e., a volume below each piston, and a volume located outside the cylinder liner 5, defined by the bottom 3 of the cylinder section 4, the wall of the cylinder section 4, and a separation wall 12 or two separation walls 12. Viewed in the longitudinal direction A, the separation wall 12 is in any case provided between the piston subspaces 11 of two adjacent cylinders 10, and this separation wall 12 separates these two piston subspaces 11 from each other, thereby preventing air from flowing directly from one piston subspace to an adjacent piston subspace or multiple piston subspaces 11 in the longitudinal direction A. Therefore, each cylinder 10 has its own individual piston subspace 11, which is defined longitudinally A by a separation wall 12 or two separation walls 12. Each individual piston subspace 11 preferably has a volume smaller than the volume of the scavenging air receiver 8.

[0065] In known longitudinal scavenging crosshead large engines, the openings provided between the first ends of adjacent cylinder liners when viewed longitudinally are no longer provided in the large engine according to the present invention. Each cylinder has its own separate piston subspace 11, which is separated longitudinally from its adjacent piston subspace 11 by a separation wall 12.

[0066] Each of the individual piston subspaces 11 of the cylinder is connected to a scavenging air receiver 8 via a separate flow coupling 13, thereby allowing scavenging air to flow into the combustion chamber of the associated cylinder 10 when the piston opens the scavenging air opening 7 of the cylinder liner 5.

[0067] Particularly preferably, a flow control element 14 is provided within each flow connection 13, and the flow control element can adjust the scavenging airflow or scavenging air stream passing through each flow connection 13. The scavenging airflow refers to the amount of scavenging air flowing through the flow connection 13 per unit time.

[0068] The flow control element 14 may be designed as a throttle, flow valve, flap valve, spool valve, or any other device capable of adjusting the scavenging airflow through the flow coupling 13. Thus, by adjusting each flow control element 14, it is possible to individually adjust the free flow cross-section within each flow coupling 13 for each cylinder.

[0069] Furthermore, it can be advantageous if the flow control element 14 is designed as a backflow prevention device, so that the scavenging air can flow through the flow coupling 13 only in the direction of each piston subspace 11, but not in the opposite direction from each piston subspace 11 into the scavenging air receiver 8. For this purpose, the flow control element 14 may be designed, for example, as a backflow prevention valve, particularly as a reed valve. The flow control element 14 may also be designed, for example, as a disc valve or poppet valve, or as a plate valve.

[0070] Preventing backflow from the piston subspace 11 into the scavenging air receiver 8 may, in some cases, lead to an increase in temperature and / or pressure within one or more of the individual piston subspaces. For this reason, it may be advantageous to provide a cooling device that can dissipate heat from the piston subspaces by a fluid heat transfer medium, such as air, water, or coolant.

[0071] The flow control element 14 is preferably designed as an adjustable flow control element 14, so that the free flow cross-section for scavenging air in each flow coupling 13 is adjustable and variable in any case. For this purpose, the flow control element may be designed as a manually adjustable flow guide element 14, or as an actuated valve that can be operated, for example, electrically, hydraulically, or pneumatically.

[0072] A control device 9 is provided for the operation of the flow control element 14, and the control device is designed to control or adjust the scavenging airflow through the scavenging air coupling 13. In this way, the scavenging airflow entering each of the cylinders 10 can be adjusted with very high precision.

[0073] For example, in the case of control, this adjustment may be made based on fixed data for operating parameters stored in the control device 9, for example, in the form of a lookup table.

[0074] Naturally, it is also possible to design the control unit 9 to adjust the scavenging airflow, thereby predetermining a desired value for the control variable, comparing this desired value with a mathematically determined actual value, and then modifying the manipulated variable to bring the actual value to the desired value.

[0075] In particular, the operating variables of the large engine 1, which are characteristic of the combustion process or the quality of the combustion process within the cylinder 10, are suitable as control variables. For example, the air-fuel ratio is suitable as a control variable, as are the ignition pressure, internal cylinder pressure, or ignition rate within each cylinder.

[0076] Naturally, embodiments are also possible in which data stored in a lookup table and mathematically determined variables are used to adjust the scavenging airflow entering each cylinder 10.

[0077] Furthermore, each flow control element 14 can be designed as a door, or incorporated into a door, thereby ensuring free access to the underside of the piston for maintenance work, for example.

[0078] Furthermore, it may be advantageous to provide at least one connecting pipe 15 that connects the piston subspace 11 of the first cylinder 10 to the piston subspace of the second cylinder 10. This connecting pipe 15 primarily works to provide pressure compensation between these two piston subspaces. For example, if the pressure in the piston subspace 11 of the first cylinder is high and counteracts the downward movement of the piston, this pressure can be reduced through the connecting pipe 15 if a lower pressure exists in the piston subspace of the second cylinder 10.

[0079] With respect to this pressure compensation, the first and second cylinders 10, whose piston subspaces are connected by a connecting pipe 15, are selected such that the piston of the first cylinder and the piston of the second cylinder 10 have a crank angle difference of at least 90°. Particularly preferably, the first and second cylinders 10, whose piston subspaces are connected by a connecting pipe 15, are selected such that the piston of the first cylinder and the piston of the second cylinder 10 have the maximum crank angle difference, i.e., about 180°. This means that the piston of the first cylinder is at the upper inversion point when the piston of the second cylinder is at the lower inversion point, and vice versa.

[0080] Each connecting pipe 15 can be designed, for example, as a conduit, a channel, or a bore.

[0081] Naturally, it is also possible to provide a control element 16 for each connecting pipe 15, and this control element can adjust the flow through the connecting pipe 15. Each control element 16 is preferably designed as an actively operable valve.

[0082] Furthermore, it is possible to provide a damping element (not shown) within the connecting pipe 15 that can attenuate pressure pulsations.

[0083] Cooling devices (not shown) may also be provided for each connecting pipe 16.

Claims

1. A longitudinal scavenging crosshead large engine, The longitudinal scavenging crosshead large engine comprises a plurality of cylinders (10), each having a cylinder liner (5), and a cylinder section (4) separated by a bottom (3), wherein the cylinder liners (5) are arranged in a longitudinal direction (A) within the cylinder section (4), Each cylinder liner (5) extends from a first end (51) facing the bottom (3) to a second end facing the combustion chamber of the cylinder (10), A piston, arranged to be movable in a reciprocating manner, is provided within each cylinder liner (5). Multiple scavenging air openings (7) are provided in each case within the cylinder liner (5), adjacent to the first end (51) of each cylinder liner (5), allowing scavenging air from the scavenging air receiver (8) to flow into each of the cylinder liners (5) through the scavenging air openings (7). A piston subspace (11) is provided for each cylinder (10), and the piston subspace is demarcated on the one side by the lower surface of the piston of the cylinder (10) and on the other side by the bottom (3) of the cylinder section (4). In a longitudinal scavenging crosshead large engine, Each piston is connected to a crosshead by a piston rod (6), and each crosshead is located below the bottom (3) of the cylinder section (4), and a separation wall (12) is provided in all cases between two adjacent piston subspaces (11) in the longitudinal direction (A), and the separation wall (12) separates the two piston subspaces (11) from each other. Each piston subspace (11) is connected to the scavenging air receiver (8) via a flow coupling (13), and At least one connecting pipe (15) is provided, and the plurality of cylinders (10) have at least a first cylinder (10) and a second cylinder (10), and the connecting pipe connects the piston subspace (11) of the first cylinder (10) to the piston subspace (11) of the second cylinder (10). A large engine featuring a longitudinal scavenging crosshead.

2. A longitudinal scavenging crosshead large engine according to claim 1, wherein a flow control element (14) is provided in each flow connection portion (13), and the flow control element can adjust the scavenging airflow passing through the flow connection portion (13).

3. The longitudinal scavenging crosshead large engine according to claim 2, wherein the flow control element (14) is designed as a throttle or a valve.

4. The longitudinal scavenging crosshead large engine according to claim 2 or 3, wherein the flow control element (14) is designed as a backflow prevention device to prevent the backflow of the scavenging air into the scavenging air receiver (8).

5. The longitudinal scavenging crosshead large engine according to any one of claims 2 to 4, wherein the flow control element (14) is designed as a reed valve.

6. The longitudinal scavenging crosshead large engine according to any one of claims 2 to 5, wherein the flow control element (14) is designed as an operable valve.

7. A longitudinal scavenging crosshead large engine according to claim 6, comprising a control device (9) which can control or adjust each of the scavenging airflows within the flow coupling section (13).

8. The longitudinal scavenging crosshead engine according to claim 7, wherein each of the scavenging airflows can be controlled or adjusted according to the operating parameters of the engine.

9. A longitudinal scavenging crosshead large engine according to any one of claims 1 to 8, wherein the piston of the first cylinder (10) and the piston of the second cylinder (10) have a crank angle difference of at least 90°.

10. A longitudinal scavenging crosshead large engine according to any one of claims 1 to 9, wherein a control element (16) is provided, and the flow through the connecting pipe (15) can be adjusted by the control element.

11. A longitudinal scavenging crosshead large engine according to any one of claims 1 to 10, wherein a damping element is provided in the connecting pipe (15), and the pressure pulsation can be dampened by the damping element.

12. A longitudinal scavenging crosshead large engine according to any one of claims 1 to 11, wherein a cooling device is provided for the piston subspace.

13. A longitudinal scavenging crosshead large engine according to any one of claims 1 to 12, designed as a two-stroke large diesel engine.

14. A longitudinal scavenging crosshead heavy-duty engine according to any one of claims 1 to 13, designed as a dual-fuel heavy-duty diesel engine that can operate in liquid mode, in which liquid fuel is introduced into the combustion chamber for combustion, and can further operate in gas mode, in which gas is introduced into the combustion chamber as fuel.

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