JP2008002471A - Hydraulic system for two stroke crosshead engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a two stroke crosshead engine in which operation of a hydraulic pressure supply device is simple and reliable and does not consume ineffective high energy, and in which a pump drive body and a valve actuator are operated by system oil. <P>SOLUTION: The two stroke crosshead engine is provided with multiple fuel pumps 13 and multiple exhaust valves 4. The fuel pumps are hydraulically driven piston pumps, and a pump drive body 14 thereof opens the exhaust valve by a hydraulic actuator 7 supplied with pressurized hydraulic fluid. The hydraulic device includes single high pressure supply channel 5. When engine load changes, the high-pressure supply channel supplies hydraulic fluid to the pump drive body 14 and the actuator 7 of the exhaust valve irrespective of substantial difference of required pressure of two types of hydraulic devices. System oil of the engine is used as hydraulic fluid, and hydraulic fluid discharged from the pump drive body 14 and the valve actuator 7 is returned to an oil reservoir of the engine. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention is a piston pump having several fuel pumps and several exhaust valves, and the fuel pump is hydraulically driven, and pressurized hydraulic fluid is supplied to the pump driver. The present invention relates to a hydraulic device for a two-stroke crosshead engine, which is performed by a hydraulic actuator to which a pressurized hydraulic fluid is supplied to open an exhaust valve.

Over the years, it has been known to hydraulically operate the exhaust valves of large two-stroke crosshead engines that are typically used as propulsion engines on ships. In this case, the valve actuator is supplied with hydraulic fluid in the form of a liquid column confined in a conduit between the pressure chamber of the actuator and the pressure chamber in the cylinder containing the camshaft actuating piston. Danish Patent No. 148664 describes an exhaust valve that is electronically controlled and hydraulically actuated, and the exhaust valve actuator is operated at a constant pressure at the start of the valve opening operation. Temporarily connected to a high pressure source of pressurized fluid. The connection time with the high-pressure source can be changed according to the engine load (Patent Document 1).

Over the years, it has been proposed that large crosshead engine fuel pumps should be hydraulically operated rather than very well known camshaft operated. Applicant's Danish Patent No. 41046 after 1929 suggests a hydraulically driven fuel pump (Patent Document 2), and from the recent ones, a piston pump in a hydraulically driven fuel pump has been suggested. Mention is made of Danish Patent No. 151145 relating to a special design (Patent Document 3).

Various known proposals relating to the operation of exhaust valves and fuel pumps in large two-stroke crosshead engines only with hydraulic pressure, combined with the large amount of energy consumption associated with such operation, is the design of the hydraulic pressure supply device. Due to the complexity, at that time, the engine could not be put into practical use. Minimizing energy consumption is essential by design for these large engines, which usually have few, if not all, days of inactivity. This is also evident from the fact that the overall engine efficiency has exceeded 50% in recent years. The following facts can be stated for the two types of devices in terms of energy savings.

For a given valve actuator, it must be a hydraulic fluid pressure that exceeds the minimum pressure required to open the exhaust valve against the pressure of the gas in the engine cylinder at the time of opening. This gas pressure varies with the desired valve opening timing during the engine cycle and the engine load. If the engine is coupled to a fixed pitch propeller, the engine speed will change with the engine load, which also means that the hydraulic fluid discharge will be faster because the valve must open more quickly at high speeds. The pressure needs to be minimal. With respect to the exhaust valve, the amount of hydraulic fluid consumed with each actuation of the valve varies very little.

It is necessary that the discharge pressure of the hydraulic fluid be higher than the minimum pressure that changes with the engine load for a given pump drive. One reason is that at higher loads, fuel must be injected into the engine cylinder for higher combustion pressures, and another reason is that more fuel must be discharged. Because it must. If the engine is coupled to a fixed pitch propeller and therefore increases in speed as the load increases, more fuel must be injected in a shorter period of time, thus requiring a higher minimum pressure. . Also, the amount of hydraulic fluid consumed varies with the amount of fuel.

The minimum pressure required for the pump driver varies more substantially with engine load than the minimum pressure required for the valve actuator, and the discharge rates of the two type devices are significantly different. For this reason, in order to operate optimally in terms of energy, the type 2 device has different characteristics and therefore different requirements for certain individual discharge pressures. This means that it is advantageous to use a completely separate supply device.

On an experimental basis, a common high-pressure pump is used to supply hydraulic fluid to the first supply conduit reaching the valve actuator and to the second supply conduit reaching the pump driver, the common high-pressure pump. Attempts have been made to ensure that the discharge of the pump to the supply conduit, which may be at a low pressure, is always done via a pressure regulating valve. Such hydraulic supply devices have proven to be complex and involve considerable energy loss.
Danish Patent No. 148664 Danish Patent No. 41046 Danish Patent No. 151145

The object of the present invention is that the hydraulic pressure supply device has a high reliability of operation and is appropriately simple, so that the pump drive body and the valve actuator can be hydraulically controlled without causing inefficient high energy consumption. It is to provide a two-stroke crosshead engine that operates solely.

In view of the above, the hydraulic device according to the present invention provides a hydraulic fluid to the pump driver and the hydraulic actuator of the exhaust valve, with a single high-pressure supply conduit providing the system oil for the engine. Is used as the hydraulic fluid, and the hydraulic fluid discharged from the pump driver and the valve actuator is returned to the oil sump of the engine.

By supplying from a common high pressure supply conduit to both the valve actuator and pump drive in accordance with the present invention, the piping of the engine cylinder is very simple, resulting in significant savings when installing the engine. Achieved. However, more importantly, the use of a common high-pressure supply conduit reduces the number of critical equipment if it fails, thus reducing the possibility of failure and increasing engine reliability. . In addition, since the number of high-pressure pipes for the type 2 apparatus is halved, a higher-strength high-pressure pipe can be manufactured more economically as a further measure for preventing failure.

By using system oil as the hydraulic fluid, the engine becomes more independent of external equipment, which increases reliability and also includes a separate tank with associated piping for storing hydraulic fluid, etc. Is no longer necessary. Also, reliability can be increased by avoiding the use of hydraulic oil that can contaminate system oil when leaked into the engine.

By using system oil as the hydraulic fluid, a very advantageous possibility is realized in terms of simplifying the hydraulic device as follows. That is, in one embodiment of the present invention, the drainage pipe from the pump drive body and the valve actuator is connected to the engine at a position below the intermediate bottom portion having the piston rod storage box for each cylinder. A return conduit may be provided that connects with the internal cavity of the frame box. Oil consumed in the pump driver and valve actuator can be drained below the cylinder air supply and at a point of consumption separate from the air supply, and a common return conduit with an associated tank is provided. It becomes unnecessary. This hydraulic device allows the oil to be discharged and used immediately when the oil is drained without requiring any other part of the system oil in the engine . The return conduit preferably opens at a position just below the middle bottom so that its length is as short as possible.

The pressure in the high pressure supply conduit preferably acts on the piston in the pump driver and valve actuator, and the piston area of the piston is compatible with each other for the pump driver and valve actuator so that the piston is 100% A substantially uniform hydraulic pressure is required at the engine load. This means that the amount of hydraulic fluid used per engine cycle is maximum, and when the highest discharge pressure is required, the energy consumption supplied to the hydraulic drive at full engine load is reduced. Enables optimal use.

When the engine load is substantially less than 100%, the discharge pressure in the high pressure supply conduit can be adjusted accordingly according to the required amount of hydraulic pressure of the valve actuator, which is the amount of fuel and hence the injection of fuel. This is because the amount of energy consumption required for reducing the engine load decreases.

The discharge pressure in the high pressure supply conduit is preferably reduced to at most 75% of the discharge pressure at 100% engine load when the engine load is 70% or less. This, in addition to saving energy, makes fuel injection even better at low engine loads when both the pressure to injection and the amount of fuel injected per engine cycle are low. When the hydraulic pressure is reduced, the operating speed of the pump piston becomes slower and the fuel injection is distributed over a longer period of time, which leads to a more favorable combustion state and as a result Heat can be distributed advantageously.

Further savings in energy consumption when discharging hydraulic fluid are realized from the following effects. That is, when the pneumatic spring affects the exhaust valve in the starting direction of the valve closing, the air pressure in the pneumatic spring is adjustable, and when the engine speed decreases and increases, respectively Both the discharge pressure in the high pressure supply conduit and the air pressure in the pneumatic spring are both adjustable downward and upward. This requires that the valve actuator exceeds the upward force acting on the actuator, both due to the action of the cylinder pressure on the underside of the valve disk and the action of the air pressure on the piston of the pneumatic spring. And If the air pressure at low speed drops, as mentioned above, the minimum pressure required to open the exhaust valve to a level close to the minimum required pressure of the pump driver, which drops relatively quickly with speed, drops. .

The air chambers in all of the engine air springs in the exhaust valve can be connected to each other. This means the following. That is, while the exhaust valve is opened downward, the volume of the air chamber decreases accordingly, so that a part of the air leaks into the air chamber and returns to the valve closing operation. Means constant.

In one embodiment, the hydraulic device has the following structure. That is, both the high-pressure supply conduits are formed of two concentric tubes that can withstand the maximum discharge pressure, and only the inner tube carries hydraulic fluid during normal operation of the hydraulic device. In addition, the annular gap defined by the two pipes is provided with a sensor for monitoring leakage in the annular gap. In this design, if the inner tube of two concentric tubes breaks, hydraulic fluid leaks into the annular gap between the tubes and a signal is emitted from the sensor while the outer tube holds the pressure It is possible to provide redundancy to the function of the supply conduit and to monitor for faults in that it assumes the function to do. For this reason, the engine operation can be continued despite the damage of the inner pipe, but the engine monitoring device is informed that the inner pipe is damaged.

Next, embodiments of the present invention will be described in more detail with reference to the accompanying drawings.
The hydraulic device supplies pressurized hydraulic fluid to the hydraulic device of the two-stroke crosshead engine 1. This engine comprises a number of cylinders 2 shown in dotted lines in FIG. 1 around a hydraulic device associated with the cylinders. There are typically many more cylinders than shown, and 4 to 14 cylinders. Each cylinder is provided with at least one, typically two or three fuel injectors 3 and an exhaust valve 4 arranged in the center of the cylinder cover.

The exhaust valve is of the poppet valve type (in the shape of a disc) which moves downward in the cylinder when the high pressure supply conduit 5 is connected to the pressure chamber 6 in the actuator 7. The actuator piston pushes the exhaust valve spindle 8 downward. The air spring 9 includes a piston 10 fixed to the spindle 8 and displaceably disposed in the cylinder. A pressure chamber 12 is disposed at a position below the piston. Pressure always acts on the valve spindle by an upward force acting in the closing direction. The pressure of the hydraulic fluid in the chamber 6 acts on the spindle 8 with a downward force. The conditions required to open the exhaust valve are due in part to the pressure of the gas in the engine cylinder and to the valve actuator 7 rather than the upward force resulting from the action of the air pressure applied to the piston 10. This generated force must be much greater accordingly.

The hydraulically driven fuel pump 13 supplies pressurized fuel to the fuel injector at a desired timing during the engine cycle and in an amount adapted to accommodate the engine load. The pump piston is driven by a pump driver 14 in the form of a cylinder with an actuator piston having a large diameter relative to the pump piston. Thus, the pump device is a stepped piston that discharges fuel at a pressure that is higher than the pressure in the conduit 5 by the ratio of the areas of the large-diameter piston and the small-diameter piston. The fuel is discharged at a pressure that is appropriately much higher than the current gas pressure in the engine cylinder, so that a good spray is made through the hole of the spraying device having a predetermined area. A fuel pump can discharge fuel to several injectors in a single cylinder, which is usually done by discharging at the same time, and the fuel pump is injected in different cylinders. It can also be designed so that fuel can be discharged into the device, in which case the fuel pump discharges fuel to different cylinders at different times.

Discharge of high-pressure hydraulic fluid from the supply conduit 5 to the actuator is controlled via a control valve 15 for the exhaust valve 4 and a control valve 16 for the fuel pump 13. The operation of these control valves is done electronically by at least one electronic control device 17 which can be a central device for several cylinders. It is also possible, for example, to use a control device distributed so as to have one control device per cylinder, or to use a combination of overall and distributed control devices. A signal can be transmitted via a signal communication line, only one of which is shown in the drawing.

The control valves 15, 16 have one position connecting the pressure chamber with the actuator piston to the high pressure conduit 5 and the other position connecting the pressure chamber back to the drain tube in the form of a conduit 18, for example 2 It can be of the position type. These control valves can also have three positions, one of which is a neutral position where both the supply conduit 5 and the return conduit 18 are disconnected from the actuator. Of course, other types of control valves and multiple combinations of several control valves can be used for each actuator device, but such a design is more complex.

The high-pressure supply conduit 5 is supplied with hydraulic fluid from a pump device 19 schematically shown as a single pump in FIG. 1, but in practice the pump device can be driven in different ways. It has several pumps. The supply conduit 20 supplies a relatively low pressure hydraulic fluid, for example 1 bar to 8 bar, to the pump device. The supply conduit 20 derives hydraulic fluid from crosshead engine system oil. A precision filter 21 ensures the filtration of the hydraulic fluid. The pump device 19 can also regulate the discharge pressure to the high-pressure supply conduit 5 over a wide range, for example 150 to 300 bar. This adjustment is controlled by a signal received from the control device 17 via the signal line 22.

FIG. 2 shows a cross-sectional view of the engine. Each engine cylinder 2 includes a cylinder liner 23 that, together with a cylinder cover 24 having an exhaust valve and a piston 25, defines a combustion chamber 26. The piston is connected to a connecting rod journal 30 on an engine crankshaft 31 through a piston rod 27, a crosshead 28 and a connecting rod 29. The crankshaft is pivotally supported on an engine base plate 32 that contains system oil, and an engine frame box 33 is attached to the top of the floor plate to support the guide surface 34 of the crosshead. The top of the guide surface is an intermediate bottom 35 with a piston rod receiving box 36, which comes from the inside of the base plate and from an engine frame box with various moving parts lubricated by system oil. The cylinder part located above the middle bottom is kept completely separated.

The fuel pump 13 is disposed at the uppermost portion of the cylinder 2 and discharges fuel through three high-pressure pipes 37 reaching the respective fuel injection devices 3. A further high-pressure pipe 38 is associated with the control valve 15 and reaches the exhaust valve 4.

Since system oil is used as the hydraulic fluid, the liquid fluid consumed in each cylinder can be discharged from the pump driver and valve actuator to the return conduit, which is located in the lower region of the intermediate bottom 35. The oil extends into the engine frame box 33, from which fluid flows down into the oil sump of the base plate. As illustrated in FIG. 1, each of the cylinders has such a drainage conduit, resulting in the special advantage that a hydraulic device can be formed without using a common return conduit. It is done.

In one embodiment, the high pressure supply conduit 5 may be a double tube structure as illustrated in FIG. Similar to the inner tube 41, the outer tube 40 can withstand the maximum discharge pressure from the pump device. These two tubes are concentric. During normal operation of the hydraulic device, hydraulic fluid is discharged exclusively through the inner tube 41. There is an annular gap 42 between the two tubes, and this annular gap is provided with a sensor 43 that monitors leakage in the annular gap. If the inner tube 41 breaks, the sensor 43 generates an alarm signal to inform the operator that there is no longer any special guarantee to prevent tube breakage. The above-described design of the conduit 5 as a double pipe is not essential, but increases the reliability during operation.

The pump driver and valve actuator are designed to operate optimally only at certain engine loads. This is described in detail below with respect to FIG. The point A of the optimum operating state is selected as the full load point of the engine at 100% load of the engine, but another point can be selected. The pump device 19 is controlled so that hydraulic fluid can be discharged at a pressure of about 250 bar. Curve a in the drawing shows how the need for the exhaust valve to be at a minimum hydraulic pressure varies with engine load when the engine is coupled directly to a fixed pitch propeller. Curve b shows how the need for the exhaust valve to be at a minimum hydraulic pressure changes when the engine is coupled to either a generator or a variable pitch propeller. In these two cases, the engine speed is constant and independent of the load, and the effective average pressure of the cylinder at low load is less than the corresponding engine pressure at variable speed. This means that at low loads, the valve actuator does not require an equally high hydraulic pressure.

Curve c shows a situation where the need for the pump driver to be at a minimum hydraulic pressure varies with engine load. It can be seen that in the upper load region, the required pressure of the pump driver decreases more rapidly than the required pressure of the exhaust valve. The reason is that both the amount of fuel to be injected and the cylinder pressure that needs to be exceeded by injection are reduced. When the engine load is reduced to a level of about 50% or less, the required pressure is constant and the pressure is determined by the lowest pressure that produces the desired spray. There is a significant difference in the trajectory between the pump driver curve and the valve actuator curve, and hydraulic fluid is supplied through the common conduit 5, so the highest need for the lowest discharge pressure at that load. It is necessary to control the discharge pressure of the pump device according to one of the devices having pressure. This device is a valve actuator in the illustrated example. As a result, the discharge pressure to the pump driver at low loads up to about 50 bar is higher than required for a variable speed engine, but part of this pressure is at low loads. It is compensated by the small amount of fuel. Of course, the hydraulic device can be designed for pressure values other than those shown, but this does not change that the relative trajectory of the curve is shown.

In one advantageous embodiment, all air chambers 12 in the exhaust valve air springs are interconnected via a common conduit 44 so that the air pressure in the chamber 12 is controlled by the exhaust valve. There is essentially no rise when opening, so there is no need to use extra hydraulic energy to overcome such pressure rise. Furthermore, the air pressure in the chamber 12 can be adjusted according to the engine speed by the air pressure controller 45 in such a way that the air pressure drops with decreasing speed. This is possible because at low speeds there is more time available to return the valve spindle to the closed position. The low reaction force from the air spring means that the discharge pressure from the pump device 19 can be lowered correspondingly, so that energy can be saved.

1 is a simplified diagram of a hydraulic device for a two-stroke crosshead engine. It is sectional drawing of an engine. FIG. 2 is a partial view of the hydraulic device of FIG. 1 on an enlarged scale. FIG. 6 is a diagram showing the correlation between engine load and the minimum pressure required to open the exhaust valve and drive the fuel pump.

Explanation of symbols

1 2 stroke crosshead engine 2 multiple cylinders 3 fuel injection device 4 exhaust valve 5 supply conduit 6 pressure chamber 7 valve actuator 8 valve spindle 9 air spring 10 piston 12 pressure chamber 13 hydraulically driven fuel pump 14 pump drive device 15 control Valve 16 Control valve 17 Electronic control device 18 Return conduit 19 Pump device 20 Supply conduit 21 Precision filter 22 Signal line 23 Cylinder liner 24 Cylinder cover 25 Exhaust valve and piston 26 Combustion chamber 27 Piston rod 28 Crosshead 29 Connecting rod 30 Connecting rod Journal 31 Crankshaft 32 Base plate 33 Engine frame box 34 Guide surface 35 Intermediate bottom 36 Housing box 37 High pressure pipe 38 High pressure pipe 40 Outer pipe 41 Inner pipe 42 Annular void 43 Leak monitoring sensor 44 Common conduit 45 Air pressure Control unit

Claims (8)

A hydraulic device for a two-stroke crosshead engine (1) having several fuel pumps (13) and several exhaust valves (4), the fuel pump being hydraulically driven piston pump The pump driver (14) is supplied with pressurized hydraulic fluid, and the exhaust valve is opened by the hydraulic actuator (7) supplied with the pressurized hydraulic fluid, Hydraulic fluid is supplied from the pump device (19) to a single high-pressure supply conduit (5), and hydraulic fluid is supplied to both the pump driver (14) and the hydraulic actuator (7) of the exhaust valve. The engine is provided with an oil sump on a base plate 32, and the oil sump contains a system oil for lubricating moving parts in the engine. ) Hydraulic device,
The supply conduit (20) supplies the system oil to the pump device (19) so that the hydraulic fluid supplied by the high pressure supply conduit (5) is the engine system oil and the pump driver ( 14) and the hydraulic fluid discharged from the hydraulic actuator (7) of the exhaust valve are returned to the oil sump of the engine,
Said single high-pressure supply conduit (5) together has two concentric tubes (40, 41) capable of withstanding the maximum discharge pressure;
Only the inner tube (41) of the two concentric tubes (40, 41) carries hydraulic fluid during normal operation of the hydraulic device and is defined by the two concentric tubes (40, 41). A hydraulic device, wherein the annular gap (42) is provided with a sensor (43) for monitoring leakage in the annular gap (42). The hydraulic device according to claim 1,
The control valve (15, 16) is of the form having two positions, one of the two positions returning the pump driver (14) or hydraulic actuator (7) in the form of a conduit (18). A hydraulic device connected to the drain. The hydraulic device according to claim 1 or 2,
For each of the cylinders (2), from the drain pipe from the cylinder pump drive (14) and from the drain pipe from the valve actuator (7), an intermediate bottom with a piston rod storage box (36) ( 35) A hydraulic device provided with a return conduit (18) extending to a height position below, which connects the drain with the internal cavity of the engine frame box. The hydraulic device according to claim 3,
A hydraulic device, wherein the return conduit opens just below the middle bottom. The hydraulic device according to any one of claims 1 to 4,
A hydraulic device in which a precision filter (21) ensures the filtration of hydraulic fluid. In the hydraulic apparatus as described in any one of Claims 1 thru | or 5,
The pressure in the high-pressure supply conduit (5) acts on the piston in the pump driver (14) and in the valve actuator (7);
The piston area of the piston is adapted to be compatible with each other for the pump driver and the valve actuator so that the pump driver and the valve actuator have a substantially uniform hydraulic pressure requirement at 100% engine load. A hydraulic device characterized by having a hydraulic pressure device. In the hydraulic apparatus as described in any one of Claims 1 thru | or 6,
When the engine load is substantially less than 100%, the discharge pressure in the high-pressure supply conduit (5) is adjusted according to the required hydraulic pressure of the valve actuator (7),
Hydraulic device. In the hydraulic apparatus as described in any one of Claims 1 thru | or 7,
Hydraulic device, characterized in that when the engine load is 70% or less, the maximum discharge pressure in the high-pressure supply conduit (5) is at most 75% of the discharge pressure at 100% engine load.

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