EP3015663B1 - Control method for quickly switching over a reciprocating piston engine - Google Patents

Description

The invention relates to a control method for quickly reversing or braking a rotation in a first direction of rotation of a crankshaft of a reciprocating internal combustion engine, in particular slow-running longitudinally flushed two-stroke large diesel engine according to the preamble of independent claim 1.

Large diesel engines are often used as drive units for ships or in stationary operation, eg for driving large generators for generating electrical energy. The engines usually run for long periods in continuous operation, which places high demands on the reliability and availability. Therefore, for the operator in particular long maintenance intervals, low wear and an economical handling of fuels and supplies are central criteria for the operation of the machines. Among other things, the piston running behavior of such large-bore slow-running diesel engines is a determining factor for the length of the maintenance intervals, the availability and the lubricant consumption also directly for the operating costs and thus for the economy. An example of a drive unit of this type is known in the art GB 722,568 provided.

In ocean shipping, there has always been the desire and the need to brake ships in as short a time as possible and thus in the shortest possible distance in an emergency situation from full speed or reverse the engine as quickly as possible, so that the propeller as fast as possible turns in the opposite direction, so that the ship can proceed as soon as possible in the opposite direction. While for relatively small motor boats or motor boats for a long time different proven procedures are available and can often be accomplished simply via gear reversing, is the "emergency braking", ie the fast braking at full speed on large ships, with large reciprocating internal combustion engines, such as For example, equipped with slow-running longitudinally flushed two-stroke large diesel engines are so far largely unresolved problem. This concerns next to the braking of the ships the closely linked problem of rapid reversal of the machine from one direction of rotation in the opposite direction of rotation.

This is a problem not to be underestimated, especially in the slow-running longitudinally-flushed two-stroke large diesel engines, since these motors due to their enormous size and performance, the practical use of a transmission and / or a coupling between the engine and propeller is practically impossible, which is why in ships with such Engines the propeller is rotatably connected via a shaft with the crankshaft of the large diesel engine.

Thus, although the construction of the drive is much simpler compared to a drive in which between the propeller and engine nor a transmission is provided. The disadvantage of such a construction without gear and clutch is, however, that the propeller is always, that is in any operating condition rotatably connected to the engine and at least in the operating condition of the engine, that is, as long as it has not come to a halt completely, not from this can be separated. That is, in an operating condition in which the engine is stopped to decelerate the ship, which in practice means essentially that the fuel supply to the engine is interrupted, the ship does not immediately stop in place, but is due to his enormous Continue inertia initially and gradually lose speed gradually.

The propeller is now no longer driven by the engine; But now, driven by the continuing relative speed between propeller and water by driving through the water. However, since the propeller is rotatably connected to the engine and this can not be separated from the engine, in such an operating state, the engine is now driven by the propeller. That is, in a considerable period of time after stopping the fuel supply to the engine, this will still continue to turn in the original direction because it is now driven by the propeller.

An acceleration of the deceleration of the ship or a reversal of the direction of travel of the ship can only be achieved by restarting the engine in the reverse direction. This can only be achieved in most known marine engines, and in particular in the giant two-stroke, longitudinally-scavenged diesel engines, by providing, at an appropriate time, i. at a suitable crank angle compressed air, also known in the trade as starting air, is pressed under a sufficiently high pressure into the cylinder liner, so that the engine is restarted by the starting air acting on the pistons in the desired reverse direction of rotation.

Due to the enormous forces, which as explained above, the propeller via the crankshaft to the pistons in the cylinder liners of the engine exerts such that the engine rotates in spite of inhibited fuel supply further in the original direction, the engine can then be restarted in the opposite direction at the earliest if the maximum available pressure of the starting air is sufficient to compensate for the forces acting on the piston by the propeller, that the engine can be offset by the starting air in a sufficiently fast rotation in the opposite direction, so that when reactivating the fuel supply, the engine can finally restart independently in the reverse direction. Of course, when the engine is restarted in the opposite direction of rotation, the marine propeller connected to the engine will also be propelled in the opposite direction by the engine, causing the vessel to decelerate progressively until the ship finally stops or, if desired, the vessel can record travel in the opposite direction.

The disadvantages of the above-described and previously customary method for braking or reversing a ship are obvious. On the one hand, the deceleration of a ship, especially a ship with a slow-running longitudinally flushed two-stroke large diesel engine requires a lot of time, because before the engine can be restarted in the opposite direction, first wait until the ship has lost enough speed and has become sufficiently slow, so that the drive of the engine over the propeller can be compensated by the starting air. This still takes a considerable amount of time, which is a great disadvantage especially when the ship has to be decelerated very rapidly, e.g. to prevent a collision with another ship, with an iceberg or with another obstacle reliably and in time in an emergency situation. The catastrophe with the famous Titanic, which among other things failed to slow down the ship in time, is still present in public consciousness. Although the Titanic was not powered by a slow-running, two-stroke, longitudinally-flushed diesel engine, the problem is basically the same.

To minimize the distance traveled by the ship when braking or when reversing in the opposite direction, is common trying to control the engine at the earliest possible time by supplying the starting air in the cylinder liner. The faster the engine, driven by the propeller, but still running in the old direction, the more starting air or starting air energy is needed to initiate the reversal in the opposite direction. This is not only expensive and energy-intensive, because the starting air must first be generated with appropriate compressors and stored in accumulators. But the process also involves the risk that more or less the entire supply of starting air is consumed and it still fails to start the engine in the opposite direction. This not only slows down the deceleration, but can even become a safety risk, because in such a situation, new starting air must first be provided again and in the meantime, the engine can not be started at all, which may have fatal consequences, because the ship is powerless in such a situation.

The object of the invention is therefore to provide a method by which a motor, in particular a slow-running longitudinally flushed two-stroke large diesel engine can be redirected more efficiently and faster in an opposite direction of rotation, the problems described in the prior art are largely avoided, especially from The fatal safety problems known from the state of the art can be circumvented and the reversing of the motor can be carried out more economically and energy-saving.

The objects of the invention solving these objects are characterized by the features of independent claim 1.

The dependent claims relate to particularly advantageous embodiments of the invention.

The invention thus relates to a control method for quickly reversing or braking a rotation in a first rotational direction of a crankshaft of a reciprocating internal combustion engine, in particular slow-running longitudinally flushed two-stroke large diesel engine, comprising a cylinder in which a piston between a top dead center corresponding to a crank angle of 180 ° and a Bottom dead center according to a crank angle of 0 ° or 360 ° is arranged to move back and forth, as well as with an outlet valve, which is hydraulically actuated by means of a standing under a predetermined opening pressure hydraulic medium, preferably hydraulic oil via a valve hydraulics. According to the invention, a fuel supply to the reciprocating internal combustion engine is interrupted in a deceleration phase and the hydraulic medium is supplied at a first maximum opening pressure of a valve hydraulics of a first exhaust valve of a first cylinder at a first crank angle in the region of the top dead center of the first cylinder associated with the first cylinder, so that the first exhaust valve, at the earliest when passing through the first piston through its top dead center position, is automatically opened by the valve hydraulics at a second crank angle.

By the present invention, a method is provided for the first time, with which a motor, in particular a slow-running longitudinally flushed two-stroke large diesel engine can be reversed more efficiently and faster in an opposite direction of rotation, while at the same time valuable starting air can be saved. In a particularly preferred embodiment of a method according to the invention, a restart in the opposite direction of rotation can be initiated even without starting air, for example by utilizing the braking energy transmitted to the engine by the propeller, which of course is not only an economic improvement that should not be underestimated , But especially if the inventive method for reversing or deceleration an engine of a ship is used, also represents an enormous progress from a safety point of view.

In a particularly preferred embodiment, the reciprocating internal combustion engine is a slow-running longitudinally-flushed two-stroke large diesel engine of a ship, such as a container ship with a huge engine, for example, up to twelve cylinders or more and has an output of up to 10,000KW per cylinder, or even greater benefits.

As is well known to those skilled in the art, in a normal operating state of the reciprocating internal combustion engine, a piston reciprocates between top dead center and bottom dead center in a cylinder liner and drives via a crankshaft which is operatively connected to the piston and a propeller Ship propeller. An outlet valve on a cylinder cover of the cylinder liner is hydraulically actuated via valve hydraulics by means of a programmable control device, which may in practice comprise a hydraulic device and an electronic device. In this case, a crank angle, in which the exhaust valve is actuated, can be predetermined in principle as desired by the programmable control device. By actuating a starting air valve, the engine can either be started from standstill or, if the engine speed is sufficiently low, the direction of rotation of the engine can be changed.

For a better understanding of the invention, the per se known general operation of a longitudinally flushed reciprocating internal combustion engine in the normal operating state is briefly briefly recalled below. In the context of this application, a crank angle of 0 ° or 360 ° is identified with the bottom dead center UT and a crank angle of 180 ° with the top dead center OT.

Starting from bottom dead center, corresponding to a crank angle of 0 °, the piston initially moves in the operating state in the direction of TDC, corresponding to a crank angle of 180 °. When the piston is in a position close to the bottom dead center, the scavenging slots in the lower region of the cylinder liner are released in the normal operating state and the outlet valve 5 is opened. As long as the scavenging slots are released from the piston fresh air is supplied to the combustion chamber of the cylinder liner through the scavenging slots and simultaneously combustion residues are flushed out of the combustion chamber by the movement of the piston in the direction of top dead center through the exhaust valve. When the piston has completely passed through the scavenging slots, so that there is no longer any connection between combustion chamber and scavenging ports, the exhaust valve is closed at a predetermined crank angle by means of the control device as the crank angle increases. In the further course, fuel is supplied through an injection valve to the combustion chamber of the engine, which is formed from the upper cylinder region, the cylinder cover located above and the piston crown, which ignites in the air heated by the compression in the region of top dead center, subsequently burned and by this energy release leads to pressure increase in the combustion chamber of the engine.

After passing through the top dead center, the piston moves back toward the bottom dead center corresponding to a crank angle of 360 °. In the normal operating and driving condition of the ship, the outlet valve is then opened again at a crank angle which is significantly greater than 180 °, and a new working stroke of the cylinder is initiated.

In the event that the ship is to be decelerated, in particular, if it is to be braked in an emergency within the shortest possible distance, the reciprocating internal combustion engine was also in the already known method from the normal operating condition as follows Braking or reversing put into another operating state. In a first step, it is known to interrupt the supply of fuel into the cylinder liner of the reciprocating internal combustion engine. By interrupting the fuel supply is achieved that the speed of the engine initially drops, resulting in a first moderate slowdown of the ship. If no further measures are taken, the speed of the ship is reduced substantially due to the friction of the ship in the water. This friction is generally comparatively low, so that the speed of the ship is reduced only very slowly. The propeller, which is no longer driven by the Hubkolbenbrennmaschine after interrupted fuel supply, now works, driven by the remaining kinetic energy of the ship as a turbine and now drives the engine, with which it is rotatably connected via the crankshaft.

If the control of the exhaust valve as previously practiced in normal operation and in the prior art maintained unchanged, while initially a part of the kinetic energy of the ship in the cylinder in the crank angle range between 0 ° and 180 ° is converted into compression energy; However, during the subsequent expansion of the scavenging air trapped in the cylinder liner during the movement of the piston from top dead center to bottom dead center, this compression energy is almost completely returned to the ship in the form of kinetic energy via the propeller.

This is where the invention is based, which is based on the finding that a rapid reversal or deceleration of the engine is essentially possible solely by suitable control of the exhaust valve and this in particular even without starting air, at least with less starting air than before in the state of Technique necessary in the opposite direction of rotation can be restarted, provided that the transmitted via the propeller engine braking energy according to the invention is used skillfully.

In a preferred embodiment of a control method according to the invention, the second crank angle is in a range between the top dead center and the bottom dead center of the first piston at a value between 180 ° and 360 °, preferably at a value between 180 ° and 225 °, or between 180 ° and 200 °, more preferably at a second crank angle, which is between 180 ° and 190 ° after top dead center of the first piston.

In order to achieve a further improvement in the braking effect during reversing, the first exhaust valve is closed again at a third crank angle in the range between the second crank angle and the bottom dead center of the first piston to generate a predetermined negative pressure in the first cylinder.

Depending on in which phase of the reversal of the motor this measure is taken essentially two positive effects can be effected.

If the generation of the negative pressure in the first cylinder in the deceleration phase of the rotation of the reciprocating internal combustion engine is carried out in the first direction of rotation and the third crank angle selected accordingly, by closing the exhaust valve with a suitable choice of the third crank angle such a negative pressure in the first cylinder can be constructed Braking the rotation of the reciprocating internal combustion engine in the first direction of rotation is supported by the structure of the negative pressure. It thus creates an at least slight suction effect on the piston, so that a corresponding braking of the piston movement is effected, which additionally extracts kinetic energy from the engine and thus accelerates the deceleration.

On the other hand, it is also possible that in a following phase of the deceleration phase of the reciprocating internal combustion engine, the third crank angle is selected so that by closing the first exhaust valve at Third crank angle, a negative pressure in the first cylinder is constructed such that a restart in a second cylinder by a fuel supply restart of the reciprocating internal combustion engine in a direction opposite to the first direction of rotation second rotational direction, supported by the structure of the negative pressure in the first cylinder. This means that in the first cylinder, a braking suction effect is generated with respect to the first direction of rotation of the motor, a restart of the engine, so a reversal of the motor in the new of the first direction of rotation opposite second direction of rotation of the motor facilitates or supports, so that an earlier reversal is possible, or possibly necessary starting air can be minimized or even completely saved.

A further additional or alternative measure of an inventive method is that the first exhaust valve is closed at a fourth crank angle between the bottom dead center and top dead center, preferably at a fourth crank angle, which is reached after stopping the supply of purging air into the cylinder ,

Even with the latter measure, it is the case that depending on in which phase of the reversal of the engine, the closing of the exhaust valve at the fourth crank angle is made, essentially two additional positive effects can be effected.

On the one hand, if in the deceleration phase of the rotation of the reciprocating internal combustion engine, the fourth crank angle is selected so that the closure of the first exhaust valve at the fourth crank angle, an overpressure in the first cylinder is constructed, braking the rotation of the reciprocating internal combustion engine in the first direction of rotation by the structure be supported by the overpressure. This is because the pressure built up in the cylinder deprives the motor of kinetic energy by converting the kinetic energy into pressure energy, which causes the engine to lose energy Braking the rotational movement of the motor in the first direction is very effectively supported.

On the other hand, if in the deceleration following Umsteuerphase the reciprocating internal combustion engine, the fourth crank angle is selected so that by closing the first exhaust valve at the fourth crank angle, an overpressure in the first cylinder is constructed such that the building up in the first cylinder pressure with one in a second Cylinder by a fuel supply initiated restart of the reciprocating internal combustion engine is suitably coordinated in a direction opposite to the first direction of rotation second direction of rotation, can be effectively supported by the structure of the pressure in the first cylinder restart in the opposite direction.

This means that in the first cylinder, a braking pressure effect is generated with respect to the first direction of rotation of the engine, a restart of the engine, so a reversal of the motor in the new of the first rotational direction opposite second direction of rotation of the motor facilitates or supports, so that an earlier reversal is possible, or possibly necessary starting air can be minimized or even completely saved.

In particular, when the reversal should take place particularly quickly or when, for example, a need for emergency braking of the ship, or another need for very fast implementation of the inventive method is required, of course, during the Umsteuerphase initiated restart of the reciprocating internal combustion engine the opposite to the first rotational direction of the second rotational direction are additionally supported by introducing a predetermined minimum amount of starting air in at least one cylinder of the reciprocating internal combustion engine, whereby the reversing in the second direction of rotation or braking from the first direction of rotation can be additionally accelerated.

In particular, but not only, if no need for an emergency very fast procedure is required to support the restart in the second direction during the Umsteuerphase the starting air is sequentially introduced only in a part of the cylinder of the reciprocating internal combustion engine, preferably even only in a single selected cylinder and is not introduced into any other cylinder.

The inventive method even allows as already mentioned above, that initiated during the Umsteuerphase restart of the reciprocating internal combustion engine in the opposite direction to the first direction of rotation can be done entirely without the use of starting air by the exhaust valve is so cleverly controlled that the kinetic energy by the propeller is fed back into the engine, optimally exploited.

In practice, the reciprocating internal combustion engine has a plurality of cylinders, which are in a conventional manner at least partially each at different crank angles, so that the measures mentioned here for accelerating the deceleration or reversal of the engine can be taken simultaneously, so that there is a cumulative effect of the different measures.

It is understood that the embodiments of the invention described in this application can also be combined in any suitable manner, depending on the application, and the specific embodiments described are to be understood merely as examples. The person skilled in the art immediately recognizes simple advantageous developments of the described exemplary embodiments of the invention and understands that even such simple developments are, of course, covered by the invention.

Claims (10)

1. A control method for a fast reversal or braking of a rotation in a first direction of rotation of a crankshaft of a reciprocating piston internal combustion engine, in particular a slow-running uniflow-scavenged large two-stroke diesel engine, comprising a cylinder in which a piston is arranged movable to and fro between a top dead center corresponding to a crank angle of 180° and a bottom dead center corresponding to a crank angle of 0° or 360°, respectively, and having an outlet valve which is hydraulically actuable via a valve hydraulics by means of a hydraulic medium, preferably hydraulic oil, at a predefined opening pressure, wherein a fuel supply to the reciprocating piston internal combustion engine is interrupted in a braking phase and the hydraulic medium is provided at a predefined maximum opening pressure of a valve hydraulics of a first outlet valve of a first cylinder at a first crank angle in the region of the top dead center position of the first piston associated with the first cylinder such that the first outlet valve is automatically opened by the valve hydraulics at a second crank angle at the earliest, when the first piston passes through its top dead center position, characterized in that the first outlet valve is closed again at a third crank angle in the region between the second crank angle and the bottom dead center of the first piston to generate a predefined vacuum in the first cylinder, wherein the third crank angle is selected in the braking phase of the rotation of the reciprocating piston internal combustion engine in the first direction of rotation such that a vacuum is built up in the first cylinder by the closing of the first outlet valve at the third crank angle such that the braking of the rotation of the reciprocating piston internal combustion engine in the first direction of rotation is assisted by the build-up of the vacuum.
2. A control method in accordance with claim 1, wherein the second crank angle lies in a range between the top dead center and the bottom dead center of the first piston at a value between 180° and 360°, preferably at a value between 180° and 225°, or between 180° and 200°, particularly preferably at a second crank angle between 180° and 190° after the top dead center of the first piston.
3. A control method in accordance with claim 1 or 2, wherein the third crank angle is selected in a reversal phase of the reciprocating piston internal combustion engine following the braking phase such that a vacuum is built up in the first cylinder by the closing of the first outlet valve at the third crank angle such that a restart of the reciprocating piston internal combustion engine in a second direction of rotation opposite to the first direction of rotation initiated in a second cylinder by a fuel supply is assisted by the build-up of the vacuum in the first cylinder.
4. A control method in accordance with any one of the preceding claims, wherein the first outlet valve is closed at a fourth crank angle between the bottom dead center and the top dead center, preferably at a fourth crank angle, which is reached after a termination of the supply of scavenging air into the cylinder.
5. A control method in accordance with claim 4, wherein the fourth crank angle is selected in the braking phase of the rotation of the reciprocating piston internal combustion engine such that an excess pressure is built up in the first cylinder by the closing of the first outlet valve at the fourth crank angle such that the braking of the rotation of the reciprocating piston internal combustion engine in the first direction of rotation is assisted by the build-up of the excess pressure.
6. A control method in accordance with claim 4, wherein the fourth crank angle is selected in the reversal phase of the reciprocating piston internal combustion engine following the braking phase such that an excess pressure is built up in the first cylinder by the closing of the first outlet valve at the fourth crank angle such that a restart of the reciprocating piston internal combustion engine in a second direction of rotation opposite to the first direction of rotation initiated in a second cylinder by a fuel supply is assisted by the build-up of the excess pressure in the first cylinder.
7. A control method in accordance with any one of the preceding claims, wherein the restart of the reciprocating piston internal combustion engine in the second direction of rotation opposite to the first direction of rotation initiated during the reversal phase is assisted by introducing a predefined minimal amount of starting air into at least one cylinder of the reciprocating piston internal combustion engine.
8. A control method in accordance with claim 7, wherein the starting air is introduced sequentially only into some of the cylinders of the reciprocating piston internal combustion engine, preferably only into one single selected cylinder and not into any other cylinder, to assist the restart in the second direction of rotation during the reversal phase.
9. A control method in accordance with any one of the claims 1 to 6, wherein the restart of the reciprocating piston internal combustion engine in the second direction of rotation opposite to the first direction of rotation initiated during the reversal phase takes place without the use of starting air.
10. A control method in accordance with any one of the preceding claims, wherein the reciprocating piston internal combustion engine is the drive unit of a ship.