Modification of valve seat for improving lubricator pump unit and lubrication system of large slow-running two-stroke engine, and improved lubricator pump unit

Abstract

To provide a method for improving a lubrication system with a lubricator, especially an Alpha lubrication system with an Alpha Lubricator.SOLUTION: By modifying the valve-seat (23) of a non-return valve system (102) in a lubricator pump unit (11), especially of the Alpha-type, a lubrication system in a large slow- running two stroke engine is improved.SELECTED DRAWING: Figure 8

Description

[Technical field]

[0001] The present invention relates to a method for improving a lubricator pump unit for a lubrication system in a large, slow-speed, two-stroke engine, by modifying the existing lubrication system to be long-lasting and leak-free, for example a large, slow-speed, two-stroke engine such as a marine engine or a large engine in a power plant. [Background technology]

[0002] The emphasis on environmental protection has led to efforts regarding the reduction of emissions from marine engines. This is accompanied by a steady optimization of the lubrication systems for such engines, especially due to increased competition. One of the economic aspects that has received increasing attention is the reduction of oil consumption, not only for environmental reasons but also because it is a significant part of the operating costs of a ship.

[0003] A lubrication system for a marine engine is disclosed in German patent document DE19743955B4 and the equivalent Danish patent DK173288B1. It discloses a lubrication system in which a central control unit supplies lubricant to a lubricator for each cylinder of the marine engine. The lubricator distributes lubricant to a number of lubricant injectors arranged around the circumference of the cylinder. The lubricator includes a housing in which a number of piston pumps are arranged around a circle and driven in unison and synchronously by a hydraulically driven actuator piston. Each piston pump includes an injection plunger pumping lubricant through a check valve to one of the injectors of a single cylinder. The hydraulically driven actuator piston travels over an adjustable distance between its stationary rear end stop and a front end stop, the adjustable distance being adjustable by an adjustment screw. To turn the adjustment screw, access is provided at an end cap which covers a flange of the housing through which the adjustment screw extends.

[0004] In connection with the injection of compact lubricant jets into marine engine cylinders and for lubricant quilling onto the pistons between the piston rings, this system has become widespread and is sold by MAN B&W Diesel and Turbo under the name Alpha Lubricator Pump Unit.

[0005] FIG. 1 shows an embodiment of a lubricator pump unit for Alpha Lubrication Systems on the internet page (http: / / www.mariness.co.kr / 02_business / Doosan%20Retrofit%20Service.pdf?PHPSESSID=fd56da9de6eaca2f1f446512e84fcf69).

[0006] To explain the principle in more detail, the drawings have been slightly modified with respect to additional reference numbers. For the sake of brevity, the lubricator pump unit for the Alpha lubrication system sold by MAN B&W Diesel and Turbo will be referred to below as "Alpha Lubricator". This terminology is consistent with the terminology normally used in the marine engine technical field and with the relevant publications and technical literature on the Internet.

[0007] Similar to the above mentioned DE19743955B4 and DK173288B1, the alpha lubricator 100 comprises a metal housing 101 in which a number of injection plungers 119 are arranged in a circle and driven together synchronously by a hydraulically driven actuator piston 123. Each injection plunger 119 is slidably arranged in an addition channel 115 which receives lubricant from an internal volume 114 of the housing 101 via an inlet opening 113. The inlet opening 113 is closed by the injection plunger 119 during its forward movement, so that further forward movement by the injection plunger 119 pressurizes the lubricant received in the remaining part of the addition channel 115 and pumps it through the check valve 102 into the pipe 103 and up to one of the single-cylinder injectors. During retraction of the actuator piston 123 caused by the prestressed spring 109, the injection plunger 119 retracts until the front end of the injection plunger 119 retracts beyond the inlet opening 113, creating a vacuum in the additive channel 115 and allowing lubricant to flow into the inlet opening 113 and refill the additive channel 115.

[0008] The volume of lubricant pressurized by the injection plunger 119 in the dosing channel 115 and expelled through the check valve 102 is determined by the distance of movement of the injection plunger 119 from the inlet opening 113 to its maximum forward position before retraction. During movement of the actuator piston 123 through its stroke length, a first portion of the movement of the injection plunger 119 passes through the inlet opening 113, and only when the injection plunger 119 passes through and closes the inlet opening 113 is lubricant pressurized and expelled from the remaining dosing channel distance.

[0009] The hydraulically driven actuator piston 123 travels over an adjustable distance between its stationary rear end stop 104 and front end stop 105, which is adjustable by an adjustment screw. To turn the adjustment screw 121, access is provided at the end cap 106, which covers the flange 107 of the housing 101, through which the adjustment screw 121 extends. The flange 107 in the alpha lubricator 100 supports a spacer 122 and includes a threaded section 110 for adjustment of the adjustment screw 121. The reciprocating actuator piston 123 is driven by hydraulic pressure oscillating in a volume 108 behind the actuator piston 123, and the solenoid valve 116 shifts between two pressure levels in this volume 108 behind the actuator piston 123. The lower the pressure level reached, the more the load of the spring 109 pushes the actuator piston 123 back to the rear end stop. The solenoid valve 116 is regulated by a corresponding signal from the control unit.

[0010] As seen in FIG. 1, a spacer 122 for the base setting of the pump stroke is provided on the flange 107 behind the end cap 106 where the head of the adjustment screw 121 is accessible for adjustment by rotation.

[0011] The Alpha Lubricator differs relatively from the above mentioned patents DE19743955B4 and DK173288B1 in that it uses a capacitive feedback sensor 120 to verify that the stroke length of the hydraulic actuator is long enough.

[0012] This feedback sensor 120 is also shown in FIG. 1. As shown, the hydraulic actuator piston includes two circumferential grooves 111, and if the stroke of the hydraulic actuator piston 123 is long enough relative to the second groove 111 to move past the feedback sensor 120, the feedback sensor 120 gives a confirmation signal of proper lubrication to the central controller. When the feedback sensor 120 passes the first and second grooves 111, the feedback sensor 120 generates a double pulse signal that the central controller receives as confirmation of proper lubrication. If the feedback sensor 120 passes only one of the first grooves 111, a corresponding single pulse signal from the feedback sensor 120 indicates to the central controller the general function of the feedback sensor 120 and that there is not enough movement of the actuator piston 123 for proper lubrication, but at least movement of the actuator piston 123 over a short distance. If the feedback sensor 120 is giving any signal, a warning message is provided by the controller that the stroke was not measured as long enough for proper lubrication.

[0013] The check valve 102 is provided inside the valve chamber 102' and is conventionally constructed by comprising a valve member, in this case a spherical valve member, prestressed against a valve seat by a spring. When the pressure of the lubricant rises beyond a predefined limit value where the force generated by the pressurized lubricant exceeds the prestressing force, the lubricant in the dosing channel 115 displaces the spherical valve member against the prestressing force of the helical spring. Once opened, the check valve 102 provides a passage in the pipe 103 for the flow of lubricant to the injector as long as the pressure remains increased during the injection phase. When the oil pressure in the dosing channel 115 decreases below the predefined limit value, the check valve 102 closes again during the idle phase and remains closed until the next injection phase.

[0014] It has been found that lubrication systems for marine engines equipped with alpha type lubricators are inadequate after a relatively short period of function, and since the overall system including the alpha lubricators is relatively expensive and long term reliability is generally required, it would be desirable to extend proper function for a longer period of time.

[0015] US2013 / 260647 discloses a common rail high pressure fuel injection system where fuel escapes from a control chamber at an elevated velocity at pressures up to 2000 bar. Due to the fact that the distance between the ball and the ball seat of the high pressure valve rises only 50 microns, the fuel will travel at very high velocities and there is a risk of cavitation. To minimise the risk of cavitation, the tool is provided with special chamfer areas, providing a chamfered undercut section in the ball seat diffuser of the valve body. The chamfered section reduces the force of the fuel flow and reduces cavitation.

[0016] In an alpha lubricator, this pressure is well below 100 bar, typically 30 times lower compared to 2000 bar in US2013 / 260647, so a diffuser is not needed either, since cavitation is not present in the alpha lubricator. Thus, this disclosure in US2013 / 260647 of a special method to fine tune a very specific fuel valve in a common rail high pressure fuel injection system to avoid cavitation in the diffuser, gives no clue as to how to repair an alpha type lubricator if it is not functioning properly after a short period of operation. Other considerations apply to provide an improvement in the art for alpha lubricators. Summary of the Invention

[0017] The object of the present invention is to provide an improvement in the art. A particular object is to provide a method for improving a lubrication system equipped with a lubricator of the type described above, in particular an alpha lubrication system equipped with an alpha lubricator.

[0018] The term "lubricator" is used herein for a lubricator pump unit which pressurizes and adds lubricant for the lubricant injectors in a corresponding large slow speed two stroke engine (usually diesel or gas fuelled). The lubricator and its function are explained in detail below with reference to the Alpha Lubricator described above with reference to Figure 1 as an example.

[0019] The term "injection phase" is used for the time during which lubricant is being injected into the cylinder by an injector. The term "idle phase" is used for the time between injection phases. The term "injection cycle" is used for the time it takes to start an injection sequence and before the next injection sequence starts, and typically the injection sequence involves all lubricant injectors during each injection sequence. For example, an injection sequence may include a single injection by each injector, in which case the injection cycle is measured from the start of an injection phase to the start of the next injection phase. The term "timing" of the injection is used for the coordination of the start of an injection phase by an injector relative to a particular position of the piston inside the cylinder.

[0020] In the case of an interval described as being between a first value and a second value, the endpoints are optionally included.

[0021] The surface roughness is expressed as the arithmetic mean roughness value Ra.

[0022] After thorough investigations into the issue of the relatively short lifespan of Alpha lubrication systems, it was discovered that the performance degradation was due to leakage from check valves in the Alpha lubricators. This is surprising as this is not a component that is generally thought to face degradation issues after a relatively short function. These investigations found that the check valves were already leaking after 1 million cycles. While at first glance 1 million cycles may seem like a lot, in reality it is not, as this may correspond to less than the time lapse between subsequent engine maintenance shutdowns.

[0023] This problem becomes more pronounced, particularly when an alpha lubricator is used for injecting lubricant when pressure rises.

[0024] Recognizing that the problem was caused by a leak in the alpha lubricator check valve, the functionality of the entire lubrication system could be improved by changing only a relatively small component, namely the check valve of the lubricator used.

[0025] From the recognition of the leakage problem, a technical solution was not easy. In particular, a simple replacement of the lubricator would not only be an expensive solution but would also limit its functionality to only another 1 million lubricant injection cycles. Therefore, it was a further objective to offer an upgrade to the Alpha lubricator.

[0026] This objective was achieved by modifying a valve seat (usually a metallic valve seat) in a valve chamber by machining the valve seat with a tool. Machining typically removes material, although some techniques result in plastic or melt deformation and some techniques may also add material to the valve seat. Machining produces a modified valve seat with greater precision. Examples of greater precision are lower surface roughness and precise circular symmetry.

[0027] Examples of machining techniques are electro-discharge machining, drilling, milling, welding, grinding, polishing, etching, plating or electrochemical machining. This list is not exclusive.

[0028] For example, the processing advantageously reduces the surface roughness to less than 12.5 μm, optionally less than 6.3 μm or less than 1.6 μm. Optionally, the surface roughness is within the range of 12.5-0.8 μm, 16.3-0.8 μm, or 1.6-0.8 μm.

[0029] In exemplary experiments presented in more detail below, valve seats were modified in a simple manner by simply pressing a deformable member into the valve seat, inducing plastic deformation. Microscopic examination revealed that the impression of such a deformable member onto the valve seat, if performed with sufficient force, substantially reduced the surface roughness of the valve seat.

[0030] Surprisingly, it has been found that this reduction in surface roughness not only provides closer, more intimate contact between the valve member and the valve seat, but also results in a many-fold increase in the life of the check valve, thereby extending the life of the lubricator and improving the overall lubrication system.

[0031] The above mentioned processing techniques allow modification of the valve seat to a higher degree of accuracy than the impression of a deformed part. Also, the presented processing techniques allow a high degree of freedom with regard to the final shape of the valve seat.

[0032] For example, these machining techniques are used to create a concave surface in the valve seat. A useful modification is to make the valve partially spherical, where it follows a portion of a sphere.

[0033] However, it is also possible to machine the valve seat into a conical shape.

[0034] As a further option, this modification is used to create a convex shape of the valve seat. One example is a convex valve seat formed as a circularly symmetric torus, for example with an elliptical or circular cross section. If the valve member is also convex, for example spherical, the valve member and the toroidal valve seat will include a very narrow mutual contact ring due to the tangential contact. A narrow contact ring is also obtained between such a torus and a conical valve member.

[0035] After modification, the valve member is installed in the valve chamber for fastening against the valve seat along the circular ring after modification of the valve seat.

[0036] For example, the method may include modifying the valve seat to achieve a concave shape having a first radius of curvature, the first radius of curvature being measured in a plane perpendicular to the valve seat, the term "perpendicular to the valve seat" being understood as perpendicular to a plane that contains a contact ring between the valve seat and the valve member.

[0037] Optionally, the machined valve seat has a first radius of curvature no less than a second radius of curvature of a convex valve member, typically a ball member, that is prestressed against the valve seat to close the valve.

[0038] For example, the valve member may be the same as that which was inside the valve chamber before the change, or a new valve member may be fitted, for example having a different size and / or shape. A typical valve member is spherical, so that the valve is a ball check valve.

[0039] Typically the valve member is made from a metal, such as steel, or alternatively the valve member is made from a polymer or ceramic.

[0040] In some embodiments, the radius of curvature for the valve seat is the same or approximately the same as the valve member. In other embodiments, the radius of curvature for the valve seat is larger than the radius of curvature of the valve member, e.g., ball member, e.g., within 5-50%. In this case, the curvature of the valve seat is sufficient to guide the curved valve member so that it is centered on the valve seat. However, due to the different curvatures, the contact ring between the convex surface of the valve member and the concave surface of the valve seat is relatively thin, which is advantageous for good sealing and fast response of the check valve.

[0041] For example, if the valve seat has a diameter of 3-10 mm, the thickness of the ring-shaped contact surface between the valve member and the valve seat is in the range of 0.01 to 0.5 mm, optionally in the range of 0.05 to 0.5 mm, or in the range of 0.1 to 0.5 mm. In terms of angular span in polar angles, this corresponds to approximately 0.1 to 10 degrees. In some practical embodiments, useful contact deflection angles are in the range of 0.1 to 5 degrees. For example, the contact surface between the valve member and the valve seat may be 0.1 mm thick or 0.2 mm thick. 2 From 2 mm 2 The area is in the range of

[0042] Typically, the valve member is 30-100% larger than the inside diameter of the valve seat. For example, if the inside diameter of the valve seat is 3 mm, the ball member is in the range of 4-6 mm in diameter. For example, the inside diameter of the valve seat is approximately equal to the diameter of the conduit upstream of the valve seat and closed by the check valve.

[0043] When the radius of curvature of the modified concave valve seat is larger than that of the convex valve member, the accuracy of the radius of curvature between the valve seat and the valve member is not required, which makes the modification process relatively simple.

[0044] The lack of constraint of the valve seat and the valve member having the same radius of curvature also allows for other concave shapes of the valve seat, such as ellipsoid, parabola, or hyperbola. A conical shape may also be used.

[0045] However, for long life it is advantageous for the valve seat to be circularly symmetric, e.g., the circular symmetry varies by less than 0.2 mm, e.g., less than 0.1 mm, when measured across the valve seat.

[0046] In some embodiments, the valve seat in the valve chamber is modified from a non-spherical to a shape that is part-spherical. A part-spherical valve seat resembles the surface of a spherical segment, also called a spherical frustum. In the following, a valve seat having such a shape is referred to as a part-spherical valve seat.

[0047] Optionally, the modified valve seat in the valve chamber has a shape that is part-spherical with a bend radius equal or substantially equal to, but not smaller than, the bend radius of the valve member abutting the valve seat, for example, as already mentioned above, the radius of curvature of the modified valve seat is greater than the radius of curvature of the valve member inserted after the processing procedure.

[0048] Optionally, to further improve the system, an additional check valve is added to the existing check valve to provide a double valve system, which improves the sealing and lifespan of the system. For example, an additional check valve is added in series with the modified check valve. Such an additional check valve may be installed in the lubricator housing at the lubricant outlet.

[0049] For example, the method includes operating a lubricator in the lubrication system for at least 100,000 lubricant injection cycles before the modification, and operating the lubrication system with the lubricator and the modified check valve after the modification.

[0050] However, the change may occur before a new lubricator, such as the alpha lubricator described above, begins its operation.

[0051] More specifically, specific embodiments of the lubrication system are described below.

[0052] The lubrication system provides lubricant to an injector for lubricating one or more cylinders in a large slow speed two stroke engine (e.g. a marine engine or a large engine in a power plant). Typically the engine burns diesel or gas fuel. The engine includes one or more cylinders, each with a reciprocating piston therein, and a number of lubricant injectors disposed along the circumference of the cylinder for injection of lubricant into the cylinder at various positions around the cylinder during an injection phase.

[0053] The lubrication system includes a lubricator that is piped to each injector by lubricant supply conduits, for example one supply conduit per injector, and supplies pressurized lubricant via the lubricant supply conduits to each injector during the injection phase.

[0054] The lubricator is of a type that includes a housing, typically a metal housing, within which a hydraulically-driven actuator piston is disposed to reciprocate with a stroke length along a stroke direction. Optionally, the lubricator further comprises a stroke length adjustment mechanism, the stroke length adjustment mechanism configured to variably adjust the stroke length of the reciprocating hydraulically-driven actuator piston between a minimum stroke length and a maximum stroke length.

[0055] The lubricator further includes a plurality of injection plungers slidably disposed in the corresponding addition channels, the injection plungers being coupled to and moved by the actuator piston and pressurizing the lubricant in the addition channels during said movement. As the actuator piston moves through its stroke length, the injector plunger moves through a corresponding length. Movement of the injection plunger inside the addition channel pressurizes the lubricant in the addition channel while the injection plunger moves through an addition channel distance, which defines a volume of lubricant in the pumping action that is discharged from the addition channel through the check valve and the supply conduit to the injector during the injection phase for injection of the lubricant into the engine cylinder.

[0056] For example, the dosing channel distance is less than or equal to the stroke length, which is determined by the configuration. Optionally, the dosing channel distance is adjustable between a minimum dosing channel distance and a maximum dosing channel distance, which corresponds to a variable stroke length of the actuator piston between the minimum and maximum stroke lengths.

[0057] The lubricator also comprises a valve, typically an electric valve, arranged to switch between hydraulic levels acting on the actuator piston to cause the actuator piston to be hydraulically actuated in reciprocating motion by switching the pressure levels. Typically the actuator piston is prestressed against a rear end stop by a helical spring.

[0058] In some specific embodiments, the lubricator receives high pressure oil for driving the actuator piston, and the valve a) access of pressurized oil to the actuator piston during the injection phase; and b) a connection between the actuator piston and a drain for draining oil from the actuator piston during the injection phase; Switches between.

[0059] The lubrication system further comprises a controller for controlling the switching of the valve. In the case of an electric valve, the controller is electrically connected to the electric valve and a corresponding electrical signal is sent from the controller to the electric valve to control the timing of the switching during the injection phase. Alternatively, the controller operates a high pressure valve upstream of the lubricator to provide switching of high pressure oil to drive the actuator piston.

[0060] According to the above objective, the lubrication system is improved by modifying the check valve of the lubricator, so that the valve seat (usually a metallic valve seat) in the valve chamber is improved, usually after a certain operation time, but can also be improved before the start of operation while the lubricator is still new. The final technical solution turned out to be a simple modification of the existing lubricator at a relatively low cost, but still solved the problem of the short life of the lubrication system.

[0061] For clarity, it is indicated that the term "injector" is used for an injection valve system comprising an injector housing including a lubricant inlet port, which is fluidly connected to a lubricant supply conduit from which it receives lubricant for injection into the cylinder. Moreover, the injector further comprises one single injection nozzle including a nozzle opening as a lubricant outlet extending into the cylinder for injecting the lubricant from this inlet port into the cylinder during the injection phase. Although the injector includes a single nozzle extending into the cylinder through the cylinder wall, the nozzle itself optionally has multiple openings when the injector is properly mounted. For example, a nozzle with multiple openings is disclosed in WO2012 / 126480.

[0062] For example, each injector comprises an outlet valve system at the nozzle, which is configured to open for the flow of lubricant to the nozzle opening during the injection phase and to close the outlet valve system after the injection phase upon a pressure rise at the outlet valve system exceeding a predetermined limit value. The outlet valve system closes due to back pressure from the cylinder and prevents the lubricant from entering the cylinder unless the outlet valve is opened. For example, the outlet valve system comprises an outlet check valve. In the outlet check valve, an outlet valve member, such as a ball, an ellipsoid, a plate or a cylinder, is prestressed against an outlet valve seat by an outlet valve spring. Upon supply of pressurized lubricant into a flow chamber upstream of the outlet valve system, the prestressed force of the spring is counteracted by the pressure of the lubricant, which displaces the outlet valve member from its outlet valve seat if the pressure is higher than the force of the spring, and the outlet check valve opens for the injection of lubricant into the cylinder through the nozzle opening. For example, the outlet valve spring acts on the valve member in a direction away from the nozzle opening, although the opposite movement is also possible.

[0063] For example, the central control device may be of a type that includes a computer or is connected by an electronic wired or wireless connection to a computer that is configured to monitor parameters regarding the actual state and operation of the engine and to control the amount and timing of lubricant injection based on these parameters.

[0064] Optionally, the injector is a SIP injector configured to supply a mist of lubricant to the scavenging air of the cylinder. A spray of atomized droplets, also called oil mist, is important in SIP lubrication, where the spray of lubricant is repeatedly injected by the injector into the scavenging air inside the cylinder before the piston passes the injector during its movement towards TDC. In the scavenging, the atomized droplets are spread and distributed on the cylinder wall when transported in the direction towards TDC due to the swirling motion of the scavenging air towards TDC. Examples of such injectors for SIP injection are disclosed in WO2012 / 126473 and WO2014 / 048438. Additional options for SIP injectors with electric valves can be found in Danish patent applications DK201770936 and DK201770940. For example, the injector includes a nozzle having a nozzle opening between 0.1 and 1 mm, such as between 0.2 and 0.5 mm, and is configured to eject a spray of atomized droplets, also referred to as oil mist. The atomization of the spray is due to the highly pressurized lubricant in the lubricant injector at the nozzle. The pressure from the lubricator is higher than 10 bar, and for this high pressure injection, it is usually between 20 bar and 120 bar. One example is an interval between 30 and 100 bar. Another example is an interval between 60 and 120 bar, such as between 60 and 100 bar. The injection time is short, usually on the order of 5 to 30 milliseconds (msec). However, the injection time can be as short as 1 msec, or even less than 1 msec, for example down to 0.1 msec.

[0065] In case of SIP injection, the lubricator is operated with the corresponding required parameters, in particular the pressure interval. For example, the method includes operating a lubrication system with a modified lubricator in combination with a SIP injector at a lubricant pressure in the range of 20-100 bar, injecting a mist of atomized droplets of lubricant by the SIP injector into the swirling scavenging air inside the engine cylinder, and distributing the droplets to the cylinder wall during the droplets' transport by a swirling motion towards the top dead center (TDC) of the cylinder.

[0066] Viscosity also influences atomization. Lubricants used in marine engines usually have a typical kinematic viscosity of about 220 cSt at 40°C and 20 cSt at 100°C, which translates to a kinematic viscosity between 202 and 37 mPa·s. One example of a useful lubricant is the high performance marine diesel engine cylinder oil ExxonMobil® Mobilgard™ 560VS. Other lubricants useful for marine engines are other Mobilgard™ oils and Castrol® Cyltech oils. Lubricants commonly used in marine engines are all useful for atomization if they have approximately the same viscosity profile in the range of 40-100°C, for example with a nozzle orifice diameter of 0.1-0.8 mm, and the lubricant has a pressure at the orifice of 30-80 bar, and a temperature in the range of 30-100°C or 40-100°C. Also see the published article on this subject by Rathesan Ravendran, Peter Jensen, Jesper de Claville Christiansen, Benny Endelt, Erik Appel Jensen, (2017) "Rheological behaviour of lubrication oils used in two-stroke marine engines", Industrial Lubrication and Tribology, Vol. 69 Issue: 5, pp. 750-753, https: / / doi.org / 10.1108 / ILT-03-2016-0075.

[0067] The invention will now be explained in more detail with reference to the drawings. [Brief description of the drawings]

[0068] [Figure 1] This is a reproduction of the Alpha control device drawings as published on the internet site (http: / / www.mariness.co.kr / 02_business / Doosan%20Retrofit%20Service.pdf?PHPSESSID=fd56da9de6eaca2f1f446512e84fcf69). [Diagram 2] 1 is a sketch of a portion of a cylinder in an engine with a lubrication system. [Diagram 3] 1 shows an embodiment of a modified lubricator. [Figure 4] 1 shows an example of a lubricator before modification. [Figure 5a] Shown are microscopic images of Alpha Lubricator valve seats: a) a new valve containing metal fringes, b) a new valve seat containing edges, and c) a used valve seat showing uneven wear. [Figure 5b] Shown are microscopic images of Alpha Lubricator valve seats: a) a new valve containing metal fringes, b) a new valve seat containing edges, and c) a used valve seat showing uneven wear. [Figure 5c] Shown are microscopic images of Alpha Lubricator valve seats: a) a new valve containing metal fringes, b) a new valve seat containing edges, and c) a used valve seat showing uneven wear. [Figure 6] a) shows measurements of the lubricator's performance before modification after 3850 injection cycles and b) after 1 million cycles. [Figure 7] Measurements of the performance of the modified lubricator after 2 million injection cycles are shown. [Figure 8] 1 shows an embodiment of a modified lubricator. [Figure 9] 1 shows a microscope image of a deformed valve seat. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0069] FIG. 1 is a reproduction of a drawing of the Alpha control device as published on the Internet site (http: / / www.mariness.co.kr / 02_business / Doosan%20Retrofit%20Service.pdf?PHPSESSID=fd56da9de6eaca2f1f446512e84fcf69).

[0070] For the methods described herein, this view of the alpha lubricator serves as an example for a specific embodiment of the modified lubricator, and therefore the explanations given in the introduction apply equally to the explanation of the modification.

[0071] Figure 2 shows half a cylinder of a large, slow-speed, two-stroke engine, such as a marine diesel engine. The cylinder 1 comprises a cylinder liner 2 inside a cylinder wall 3. Inside the cylinder wall 3 are provided a number of injectors 4 for the injection of lubricant into the cylinder 1.

[0072] As shown, the injectors 4 are arranged along a circle with the same angular distance between adjacent injectors 4, although this is not strictly necessary. It will also be appreciated that arrangements using axially shifted injectors are also possible, for example with injectors shifted each second towards top dead centre (TDC) of the piston relative to adjacent injectors, and an arrangement along a circle is not necessary.

[0073] As shown, the injector 4 receives pressurized lubricating oil from a lubricator 11 via a lubricant supply line 9. The oil is typically heated to a particular temperature, e.g., 50-60 degrees. The lubricator 11 supplies pressurized lubricating oil to the injector 4 in precisely timed pulses, synchronized with the piston movement in the engine's cylinder 1. Injection by the lubricator 11 is controlled by a controller 12. For synchronization, the controller 12 monitors parameters about the actual condition and motion of the engine, including crankshaft speed, load, and position, the latter accounting for the position of the piston in the cylinder.

[0074] Each of the injectors 4 is equipped with a nozzle 5 including a nozzle opening 5' from which the lubricant is discharged under high pressure into the cylinder 1, for example in the form of a compact jet or as a finely atomized spray 8 with microdroplets 7 for SIP injection.

[0075] For example, for SIP injection, the nozzle opening has a diameter between 0.1 and 0.8 mm, such as between 0.2 and 0.5 mm, and atomizes the lubricant into a fine spray 8 at high pressure, as opposed to a compact jet of lubricant. The pressure is above 10 bar, for example between 10 and 120 bar, optionally between 20 and 120 bar, or between 20 and 100 bar, between 30 and 80 bar, or between 50 and 80 bar, or between 60 and 120 bar, or even a pressure higher than 120 bar. The swirl 10 of the scavenging air in the cylinder 1 transports and presses the spray 8 against the cylinder liner 2, so that a uniform distribution of the lubricant on the cylinder liner 2 is achieved.

[0076] Optionally, the cylinder liner 2 is provided with a free-out 6 to provide suitable space for the spray 8 or injection from the injector 4 .

[0077] The lubricator 11 is connected to a supply conduit 14 for receiving lubricant from a lubricant supply 15 including an oil pump, and to a return conduit 13 for the return of the lubricant, typically to an oil reservoir, optionally for recirculation of the lubricant. The lubricant pressure in the supply conduit 14 is higher, for example at least two times higher, than the pressure in the return conduit 13. In addition to driving the actuator piston in the lubricator 11, the lubricant supply conduit 14 is also used to supply lubricant for lubrication.

[0078] Figure 3 shows an embodiment of the modified lubricator 11. The numbering is the same as the modified prior art lubricator of Figure 1. Before modification, the valve chamber 102' contains the single check valve 102 of Figure 1.

[0079] FIG. 4 is a more detailed view of the check valve 102 in the valve chamber 102' of the prior art lubricator 11 of FIG. 1. Two enlarged sections B and C show the details at additional magnifications of 3x and 6x, respectively. The check valve 102 includes a spherical valve member 23 that is prestressed against a valve seat 24 by a load from a helical spring 25. When the lubricant in the dosing channel 115 reaches a pressure above a predetermined threshold, the lubricant in the dosing channel 115 displaces the valve member 23 against the prestressing force of the spring 25. As shown, the valve seat 24 is a sharp edge, even though the valve chamber 102' has a generally conical end 27. A thorough investigation of the early failure of the lubricator 11 revealed that the leakage was due to a sealing problem of the sharp edge valve seat 24.

[0080] Improvements are achieved when the valve seat 24 is modified, for example, such that the modified valve seat has a contour that is a portion of a sphere, optionally with the same radius as the spherical valve member.

[0081] FIG. 5 shows some microscopic images of the valve seat of the alpha lubricator before modification. FIG. 5a shows the valve seat of the new alpha lubricator and the noticeable roughness of the metal fringe 35 in the valve seat, which damages the sealing of the check valve. FIG. 5b shows the edge 34 in the valve seat 24 of the new alpha lubricator, which prevents a proper seal between the valve seat 24 and the ball member. FIG. 5c shows a microscopic photograph of the used alpha lubricator, illustrating that due to the oval shape of the valve seat, the cross section 24' of the valve seat appears wider than the other cross sections 24''. The oval valve seat is most likely due to uneven wear during use. It no longer seals properly against the spherical valve member. All of these defects in the valve seat, some from the new alpha lubricator and some from wear during use, prevent adequate sealing, especially when the lubricant pressure is high.

[0082] Figures 6a and 6b show measurements of the lubricator's performance before modification, where the valve seat 24 had sharp edges as shown in Figure 4 and defects as shown in Figure 5. The six graphs in Figures 6a and 6b are made for the six outlets of the Alpha lubricator, each outlet containing one check valve. The measurement in Figure 8a was made after 3850 injection cycles. The peaks indicate the injection and the plateaus indicate the pressure levels during the idle phase. The graph in Figure 8b shows the same measurement after 1 million cycles. The drop in the curve drawn in solid line indicates the pressure loss during the idle phase caused by the leakage of the check valve 102.

[0083] Figure 7 shows the measurement of the performance of the modified lubricator after 2 million injection cycles. The experimental results show the horizontal pressure curve during the idle phase between the spikes of the injection phase. The horizontal pressure level in Figure 7 represents an increased life of the modified check valve 102 by more than double in terms of sealing, in contrast to the decreasing pressure curve in Figure 6b.

[0084] The lubricator 11 in the test experiment of FIG. 7 includes a valve seat 24 that has been modified to a part-spherical configuration with smaller surface roughness and greater precision with respect to circular symmetry.

[0085] The modification of the valve seat for the experiment of Figure 7 was performed by pressing a ball-shaped deformable member of approximately the same size as the ball-shaped valve member 23 onto the sharp-edged valve seat 24 with a force equivalent to 200 kg. This force was sufficient to deform the sharp-edged valve seat 24 from the configuration of Figure 4 to the shape of a portion of a sphere with less surface roughness and more accurate circular symmetry.

[0086] Deformation by pressing a deforming member, such as a steel ball under a force, into the valve chamber is a simple way of modifying the sharp edged valve seat 24 of FIG.

[0087] More advanced are techniques for machining the valve seats, such as EDM, drilling, milling, welding, grinding, polishing, etching, plating, and / or electrochemical machining, and various techniques can be combined for optimal results.

[0088] Figure 8 shows an embodiment in which the valve seat 24 has been modified by machining the valve seat into a dimensionally accurate concave segment, such as a part-spherical segment, similar to that used in the test experiment of Figure 7. This shows a ball-shaped valve member 23 resting against the valve seat 24.

[0089] For greater clarity, the radius of curvature 33 of the valve seat 24 and the radius of curvature 34 of the spherical valve member are measured in a plane perpendicular to and centered on the valve seat, as shown in Figure 8. The two radii of curvature are shown in Figure 8, which is a cross-sectional view, and are therefore drawn onto such a plane.

[0090] Figure 9 shows a microscope image of the modified valve seat, which was deformed using a deformation member. In the experiment, a spherical deformation member with a surface roughness of 0.06 μm (arithmetic mean roughness value Ra) was pressed against the valve seat with a force equivalent to 200 kg, causing deformation and resulting in a change in surface roughness of 0.8 μm. The width of the ring-shaped valve seat was 0.06 mm. The surface area of ​​the valve seat was approximately 0.5 mm. 2 It was.

[0091] As a result of the deformation, the life was significantly improved, but by machining the valve seat using the above method, the dimensional accuracy was further improved and the life was further improved.

[0092] For example, the final valve seat includes a concave shape, typically a partial sphere, having the same or substantially the same radius of curvature as the spherical valve member. Due to this partial spherical valve seat, the contact area 28 between the spherical valve member 23 and the valve seat 24 is smoother than between the spherical valve member 23 and the sharp-edged valve seat 24 of FIG. 4. Alternatively, the valve seat achieves a concave shape with a radius of curvature larger than the radius of curvature for the valve member. As a further alternative, the final valve seat has a conical or convex toroidal shape.

Claims

1. 1. A method of improving a lubrication system in a large, low speed engine, comprising: The engine includes a cylinder (1) with an internal reciprocating piston and a plurality of lubricant injectors (4) arranged along a circumference of the cylinder (1) for injection of lubricant into the cylinder (1) at various positions around the circumference during an injection phase; the lubrication system is configured to supply lubricant to the injector (4) during the injection phase; said lubrication system including a lubricator (11) piped to each injector (4) by a lubricant supply conduit (9) for supplying pressurized lubricant to each injector (4) via said lubricant supply conduit (9) during said injection phase; The lubricator (11) includes a housing (101) in which a hydraulically driven actuator piston (123) is disposed for reciprocating movement along a stroke length; The housing (101) further includes a plurality of injection plungers (119) and a corresponding plurality of addition channels (115), one check valve (102) for each of the addition channels (115); Each injection plunger (119) is slidably disposed in one of the addition channels (115); the injection plunger (119) is coupled to the actuator piston (123) so as to be commonly moved by the actuator piston (123) over the stroke length, and pressurizes the lubricant in the addition channels (115) over an addition channel distance to expel the pressurized lubricant from each addition channel (115) through the corresponding check valve (102) and inject the lubricant into the engine cylinder (1); the dosing channel distance defines a volume of lubricant discharged from the dosing channel (115) through the check valve (102) during the injection phase; Each check valve (102) is mounted in a corresponding valve chamber (102') in said housing (11) and includes a valve member (23) prestressed against a valve seat (24) by the load of a spring (25); The method comprises: removing the spring (25) and the valve member (23) from the valve chamber (102'); modifying the valve seat (24) by machining the valve seat (24) with a machining tool in the valve chamber (102'), the machining tool replacing, removing or adding material to the valve seat and improving the dimensional accuracy of the valve seat (24) by the machining; Thereafter, operating the lubricator (11) in the lubrication system of the engine comprising the modified valve seat (24); A method comprising:

2. The method comprises: machining the valve seat (24) into a circularly symmetric shape; 2. The method of claim 1, wherein the circular symmetry varies by less than 0.2 mm when measured across the different valve seats (24).

3. 3. The method of claim 1 or 2, wherein the method includes machining the valve seat (24) to reduce a surface roughness of the valve seat (24) for intimate contact between the valve member (23) and the valve seat (24).

4. The method of claim 3, wherein the method includes providing a surface roughness of the valve seat (24) by the machining that is less than 12.5 μm.

5. The method comprises: modifying the valve seat (24) to a concave shape having a first radius of curvature (34); providing said valve member (23) having a convex shape with a second radius of curvature (33) less than or equal to said first radius of curvature (34); Including, The method of any one of claims 1 to 4, wherein the first radius of curvature and the second radius of curvature are measured in a plane perpendicular to the valve seat (24).

6. The method of claim 5, wherein the first radius of curvature is between 5 and 50% greater than the second radius of curvature.

7. The method according to any one of claims 1 to 6, wherein the machining comprises at least one of the following: electric discharge machining, drilling, milling, welding, grinding, polishing, etching, plating, and electrochemical machining.

8. The method comprises: operating the lubricator (11) in the lubrication system for at least 100,000 lubricant injection cycles prior to said modification; continuing operation of the lubrication system using the lubricator (11) and the modified valve seat (24) after the modification; and The method according to any one of claims 1 to 7, comprising:

9. operating the lubrication system by supplying lubricant to the injector using the modified lubricator (11) at a lubricant pressure in the range of 20 to 100 bar; injecting a mist of atomized droplets of lubricant into the swirling scavenging air inside the engine cylinder with the injector; distributing the droplets on the cylinder wall during transport of the droplets by pivoting toward a top dead center (TDC) of the cylinder; The method according to any one of claims 1 to 8, comprising:

10. A method for improving a lubricator (11) for a large low speed engine, comprising the steps of: The engine includes a cylinder (1) with an internal reciprocating piston and a plurality of lubricant injectors (4) arranged along a circumference of the cylinder (1) for injection of lubricant into the cylinder (1) at various positions around the circumference during an injection phase; the lubricator (11) is configured to supply pressurized lubricant to the injector (4) during the injection phase; The lubricator (11) includes a housing (101) in which a hydraulically driven actuator piston (123) is disposed for reciprocating movement along a stroke length; The housing (101) further includes a plurality of injection plungers (119) and a corresponding plurality of addition channels (115), one check valve (102) for each of the addition channels (115); Each injection plunger (119) is slidably disposed in one of the addition channels (115); the injection plunger (119) is coupled to the actuator piston (123) so as to be commonly moved by the actuator piston (123) over the stroke length, and pressurizes the lubricant in the addition channels (115) over an addition channel distance to expel the pressurized lubricant from each addition channel (115) through the corresponding check valve (102) and inject the lubricant into the engine cylinder (1); the dosing channel distance defines a volume of lubricant discharged from the dosing channel (115) through the check valve (102) during the injection phase; Each check valve (102) is mounted in a corresponding valve chamber (102') in said housing (11) and includes a spherical valve member (23) prestressed against a valve seat (24) by the load of a spring (25); The method comprises: removing the spring (25) and the valve member (23) from the valve chamber (102'); modifying the valve seat (24) by machining the valve seat with a tool in the valve chamber (102'), the tool replacing, removing or adding material to the valve seat and improving the dimensional accuracy of the valve seat by said machining; Thereafter, operating the lubricator (11) in the lubrication system of the engine comprising the modified valve seat (24); A method comprising:

11. The method comprises: machining the valve seat (24) into a circularly symmetric shape; The method of claim 10, wherein the circular symmetry varies by less than 0.2 mm when measured across the different valve seats (24).

12. 12. The method according to claim 10 or 11, wherein the method includes machining the valve seat (24) to reduce a surface roughness of the valve seat (24) for intimate contact between the valve member (23) and the valve seat (24).

13. The method of claim 12, wherein the method includes providing a surface roughness of the valve seat (24) by the machining that is less than 12.5 μm.

14. The method comprises: modifying the valve seat (24) to a concave shape having a first radius of curvature (34); providing said valve member (23) having a convex shape with a second radius of curvature (33) less than or equal to said first radius of curvature (34); Including, The method of any one of claims 10 to 13, wherein the first radius of curvature and the second radius of curvature are measured in a plane perpendicular to the valve seat (24).

15. The method of claim 14, wherein the first radius of curvature is between 5 and 50% greater than the second radius of curvature.

16. The method according to any one of claims 10 to 15, wherein the machining comprises at least one of the following: electric discharge machining, drilling, milling, welding, grinding, polishing, etching, plating, electrochemical machining.

17. A lubricator (11) for a large low speed engine, comprising: The engine includes a cylinder (1) with an internal reciprocating piston and a plurality of lubricant injectors (4) arranged along a circumference of the cylinder (1) for injection of lubricant into the cylinder (1) at various positions around the circumference during an injection phase; the lubricator (11) is configured to supply pressurized lubricant to the injector (4) during the injection phase; The lubricator (11) includes a housing (101) in which a hydraulically driven actuator piston (123) is disposed for reciprocating movement along a stroke length; The housing (101) further includes a plurality of injection plungers (119) and a corresponding plurality of addition channels (115), one check valve (102) for each of the addition channels (115); Each injection plunger (119) is slidably disposed in one of the addition channels (115); the injection plunger (119) is coupled to the actuator piston (123) so as to be commonly moved by the actuator piston (123) over the stroke length, and pressurizes the lubricant in the addition channels (115) over an addition channel distance to expel the pressurized lubricant from each addition channel (115) through the corresponding check valve (102) and inject the lubricant into the engine cylinder (1); the dosing channel distance defines a volume of lubricant discharged from the dosing channel (115) through the check valve (102) during the injection phase; Each check valve (102) is mounted in a corresponding valve chamber (102') in said housing (11) and includes a spherical valve member (23) prestressed against a valve seat (24) by the load of a spring (25); the valve seat has a diameter of 3 to 10 mm; the thickness of the ring-shaped contact surface between the valve member and the valve seat is in the range of 0.01 mm to 0.5 mm; 10. A lubricator comprising: a valve seat having a circularly symmetric shape, the circular symmetry varying by less than 0.2 mm when measured across the valve seat; and a surface roughness of the valve seat (24) of less than 12.5 μm.

18. the valve seat (24) is concave and has a first radius of curvature (34) at the contact surface; the valve member (23) has a convex shape with a second radius of curvature (33); the first radius of curvature and the second radius of curvature are measured in a plane perpendicular to the valve seat; 18. The lubricator of claim 17, wherein the first radius of curvature is 5 to 50% greater than the second radius of curvature.

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