JP2020200831A - Large-sized two-stroke uniflow scavenging gas fuel engine, and method of controlling state of combustion chamber - Google Patents

Abstract

To provide a large-size two-stroke turbocharging-type uniflow scavenging internal combustion engine, and a method of controlling the same.SOLUTION: An engine includes a plurality of combustion chambers and at least one controller, and the controller determines an average compression air excess ratio and a bulk compression temperature in starting combustion, to perform a measure to lower the compression air excess ratio when the average compression air excess ratio is lower than a compression air excess ratio lower threshold value, to perform a measures to lower the compression air excess ratio when the average compression air excess ratio is more than the compression air excess ratio upper threshold value, to perform a measure to increase a bulk compression temperature when the determined or measured bulk compression temperature is lower than a bulk compression temperature lower threshold value, and to perform a measure to lower the bulk compression temperature when the determined or measured bulk compression temperature is more than the bulk compression temperature upper threshold value.SELECTED DRAWING: Figure 5

Description

The present specification relates to a large two-stroke internal combustion engine using gas fuel, and more particularly to a crosshead large two-stroke uniflow scavenging internal combustion engine operated by gas fuel injected from a fuel valve arranged in a cylinder liner.

background

The crosshead large 2-stroke uniflow scavenging internal combustion engine is used, for example, as a propulsion system for a large ship or as a prime mover for a power plant. The size of this large two-stroke engine is huge. This large two-stroke engine has a structure different from other internal combustion engines, not only because of its huge size. For example, the weight of the exhaust valve can reach 400 kg and the diameter of the piston can reach 100 cm. The maximum pressure in the combustion chamber during operation is typically hundreds of bars. The force generated by such a high pressure level and piston size is enormous.

Some large two-stroke turbocharged internal combustion engines are operated by gas fuel introduced from a fuel valve provided near the center of the cylinder liner in the longitudinal direction. In this type of engine, the gas fuel is introduced into the cylinder during the ascending stroke of the piston, well before the exhaust valve closes. The engine compresses a mixture of gas fuel and scavenging in the combustion chamber and ignites the compressed mixture by synchronous ignition means (eg, pilot oil ignition means) at or near top dead center (TDC).

In a large two-stroke turbocharged internal combustion engine, when the piston injects gas fuel at or near top dead center (TDC), the compression pressure in the combustion chamber is almost maximum. In comparison, the above-mentioned type of gas introduction using a fuel valve arranged in the cylinder liner has an advantage that a considerably low fuel injection pressure can be used because gas fuel is injected when the pressure in the combustion chamber is relatively low. Has. In the case of a type of engine that injects gas fuel at or near the TDC, it is necessary to realize a fuel injection pressure that is sufficiently higher than the pressure in the combustion chamber, which is already almost the maximum pressure. Fuel systems that can handle gas fuels at such extremely high pressures are expensive and complex. The reasons for this are the volatility of gas fuels and their behavior under high pressure, which can diffuse into (or through) the steel components of the fuel system.

For this reason, the fuel supply system of an engine that injects gas fuel in the middle of the compression stroke is much cheaper than that of an engine that injects gas fuel at or near the TDC.

However, when the gas fuel is injected in the middle of the compression stroke, the piston compresses the mixture of the gas fuel and the scavenging air, which involves a risk of abnormal early ignition (pre-ignition). By operating with a very dilute mixture, the risk of pre-ignition can be reduced. However, using a lean mixture increases the risk of misfire.

Therefore, in a large two-stroke turbocharged internal combustion engine as described above, it is necessary to improve the control of the state of the combustion chamber during compression in order to eliminate or at least reduce the problems of pre-ignition and diesel knock. Exists. In order to prevent the occurrence of pre-ignition and misfire, it is necessary to control the state of the combustion chamber very accurately.

When the engine is running in steady state, the performance design of the engine is usually designed to prevent pre-ignition. This is achieved by careful selection of combustion chamber design, fuel injection timing and exhaust valve timing. However, the condition of driving in the tropics and other external factors (such as the engine not running steadily) are unavoidable, in which case the condition of the combustion chamber induces pre-ignition and misfire. It may end up.

EP2634398 discloses a two-stroke engine that operates on fuel gas as the main fuel. The claim 1 describes that the average air-fuel ratio is controlled by adjusting the air flow rates supplied to a plurality of cylinders by using an air-fuel ratio controller that calculates the air-fuel ratio in the cylinders. It is also described that this air-fuel ratio controller controls the air-fuel ratio by calculating the air-fuel ratio of each cylinder and adjusting the closing timing of the exhaust valve. The air-fuel ratio is maintained between the upper and lower thresholds. However, this is insufficient to prevent pre-ignition under all operating conditions.

Description

One of the objectives is to provide an engine and method that solves or at least alleviates the above problems.

This and other objectives are achieved by embodiments of the present application. The specific implementation form will also be clarified from the detailed description and drawings of the invention.

According to the first aspect, the following engine is provided.

A large two-stroke uniflow scavenging internal combustion engine that operates on gas fuel as the main fuel in the gas operation mode, in order to introduce scavenging into a plurality of combustion chambers defined by a cylinder liner, a piston, and a cylinder cover, and the combustion chamber. A scavenging port, an scavenging port located on the cylinder liner, an exhaust outlet located on the cylinder cover and controlled by an exhaust valve, a variable timing exhaust valve drive system, and at least associated with the engine. The at least one controller comprises one controller.
Determine and control the opening and closing timing of the exhaust valve;
Determine and control the amount of gas fuel introduced into the combustion chamber;
Determine or measure the average compression air excess ratio of the combustion chamber;
Determine or measure the bulk compression temperature of the combustion chamber at the start of combustion;
If the average compressed air excess rate determined or measured above is below the threshold below the compressed air excess rate, at least one measure to increase the compressed air excess rate is implemented;
If the average compressed air excess rate determined or measured above exceeds the compressed air excess rate upper threshold, at least one measure is implemented to reduce the compressed air excess rate;
If the bulk compression temperature determined or measured above is below the bulk compression temperature threshold, at least one measure to raise the bulk compression temperature is implemented;
If the bulk compression temperature determined or measured above exceeds the bulk compression temperature threshold, at least one measure to lower the bulk compression temperature is implemented;
An institution that is structured so that.

By providing the large two-stroke engine with a controller that maintains the bulk compression temperature and excess compressed air ratio between the upper and lower thresholds by adjusting the bulk compression temperature and air-fuel ratio, the combustion chamber during compression The state is prevented from progressing to a state toward pre-ignition or a state toward misfire. This allows a large two-stroke engine with a controller as defined above to operate virtually without the risk of pre-ignition or misfire, regardless of operating conditions.

In an example of the embodiment of the first aspect, the at least one controller comprises a compressed air excess rate observing means for determining the instantaneous average compressed air excess rate of the combustion chamber, or such a compressed air excess rate. Connected to the observation means.

In an example of the implementation of the first aspect, the at least one controller comprises or is connected to a bulk compression temperature observing means that determines the instantaneous bulk compression temperature of the combustion chamber. ..

In an example of the implementation of the first aspect, the compressed air excess rate lower threshold value, the compressed air excess rate upper threshold value, the bulk compression temperature lower threshold value, and the bulk compression temperature upper threshold value all depend on the engine load. It is a parameter.

In an example of the implementation of the first aspect, at least one measure for increasing the excess compressed air rate is selected from the following measures.
-Advance the timing of closing the exhaust valve.
-If the engine is equipped with a scavenging bypass, close the scavenging bypass or increase the throttle of the scavenging bypass.
-If the engine is equipped with a hot cylinder bypass, open the hot cylinder bypass control valve or weaken the throttle of the hot cylinder bypass control valve.
-If the institution is equipped with an auxiliary blower, activate the auxiliary blower.
-If the engine is equipped with a variable geometry turbine, reduce the effective turbine flow path area.
-If the engine is equipped with turbocharger assist, increase the speed of the turbocharger.
-If the engine is equipped with an exhaust gas recirculation system, reduce the rotation speed of the exhaust gas recirculation blower.
-If the engine operates on both gas fuel and liquid fuel, increase the proportion of liquid fuel.

In an example of the implementation of the first aspect, at least one measure for reducing the excess compressed air rate is selected from the following measures.
-Delay the timing to close the exhaust valve.
-If the engine is equipped with a scavenging bypass, open the scavenging bypass or weaken the throttle of the scavenging bypass control valve.
-If the engine is equipped with an exhaust gas recirculation system, activate the exhaust gas recirculation blower in the exhaust gas recirculation pipe or increase the rotation speed of the exhaust gas recirculation blower.
-If the engine is equipped with an exhaust bypass, open the exhaust bypass control valve or weaken the throttle of the exhaust bypass control valve.
-If the engine is equipped with a variable geometry turbine, increase the effective turbine flow path area.
-If the engine is equipped with a liquid fuel ignition system, reduce the proportion of gas fuel and increase the proportion of liquid fuel.
-If the engine is equipped with turbocharger assist, reduce the turbocharger assist.

In an example of the implementation of the first aspect, at least one measure for raising the bulk compression temperature is selected from the following measures.
-If the engine is equipped with a cylinder bypass, open the cylinder bypass or weaken the throttle of the cylinder bypass control valve.
-If the engine is equipped with a hot cylinder bypass, open the hot cylinder bypass control valve or weaken the throttle of the hot cylinder bypass control valve.
-If the engine is equipped with a cold cylinder bypass, open the cold cylinder bypass control valve or weaken the throttle of the cold cylinder bypass control valve.
-If the engine is equipped with a scavenging cooler bypass, open the scavenging cooler bypass control valve or weaken the throttle of the scavenging cooler bypass.
-Advance the timing of closing the exhaust valve.

In an example of the implementation of the first aspect, at least one measure for lowering the bulk compression temperature is selected from the following measures.
-Temporarily suppress changing the timing of closing the exhaust valve.
-Delay the timing to close the exhaust valve.
-If the engine is equipped with a hot cylinder bypass, close the hot cylinder bypass control valve or throttle the hot cylinder bypass control valve.
-If the institution is equipped with an auxiliary blower, activate the auxiliary blower.
-If the engine is equipped with water injection, inject water into the combustion chamber during the compression stroke.

In an example of the embodiment of the first aspect, the at least one controller is determined and measured when the average compressed air excess rate is lower than the minimum compressed air excess rate threshold lower than the compressed air excess rate lower threshold. It is configured to implement further measures to increase the excess compressed air rate.

In an example of the embodiment of the first aspect, if the determined or measured average compressed air excess rate exceeds the maximum compressed air excess rate threshold higher than the compressed air excess rate upper threshold, the at least one controller. It is configured to implement further measures to reduce the excess compressed air rate.

In an example of the embodiment of the first aspect, the at least one controller determines the bulk compression temperature when the determined or measured bulk compression temperature is below the minimum bulk compression temperature threshold lower than the bulk compression temperature threshold. It is configured to implement further measures to raise it.

In an example of the embodiment of the first aspect, the at least one controller determines the bulk compression temperature when the determined or measured bulk compression temperature exceeds the maximum bulk compression temperature threshold higher than the bulk compression temperature upper threshold. It is configured to take further measures to lower it.

In an example of the mounting embodiment of the first aspect, one or more gas fuels are introduced into the cylinder liner in order to introduce the gas fuel supplied from the pressurized gas fuel supply unit through the fuel introduction valve into the combustion chamber. Introductory holes are arranged.

In an example of the implementation of the first aspect, in the gas operation mode, liquid fuel is injected to ignite the air-fuel mixture in the combustion chamber.

In one example of the implementation of the first aspect, the engine is configured to operate the liquid fuel on the liquid fuel in an operating mode.

In an example of the implementation of the first aspect, the excess compressed air ratio is a weight-based ratio.

In an example of the implementation of the first aspect, the controller is for increasing the compressed air excess rate when the determined or measured average compressed air excess rate becomes higher than the threshold value below the compressed air excess rate. Stop implementing at least one measure.

In an example of the implementation of the first aspect, the controller is for lowering the compressed air excess rate when the determined or measured average compressed air excess rate becomes lower than the threshold value on the compressed air excess rate. Stop implementing at least one measure.

In an example of the implementation of the first aspect, the controller has at least one measure for raising the bulk compression temperature when the determined or measured bulk compression temperature is higher than the bulk compression temperature threshold. Stop running.

In an example of the implementation of the first aspect, the controller has at least one measure for lowering the bulk compression temperature when the determined or measured bulk compression temperature is lower than the bulk compression temperature threshold. Stop running.

In an example of the implementation of the first aspect, the controller controls the exhaust valve drive system and the fuel introduction valve according to a predetermined look-up table. This look-up table shows the opening / closing timing of the exhaust valve according to the load of the engine, and also shows the opening / closing of the fuel introduction valve according to the load of the engine.

In an example of the mounting embodiment of the first side surface, the gas introduction hole is arranged at a substantially central portion in the longitudinal direction of the cylinder liner.

In an example of the implementation of the first aspect, the engine is a uniflow scavenging engine.

In an example of the mounting embodiment of the first side surface, the gas introduction hole is directed toward the central portion of the cylinder liner and is located above the upper end portion of the scavenging boat.

In an example of the implementation of the first aspect, the engine has an ignition system for igniting. The ignition system is controlled by the electronic control unit. The ignition system is preferably controlled by the electronic control unit at or near the TDC to initiate ignition. The ignition system may be an electronic ignition system, such as a laser ignition system. The ignition system may also include a liquid ignition system. When the controller determines that ignition should be initiated, the liquid ignition system is electronically controlled to ignite the liquid fuel. The ignition system may have a prechamber into which the liquid fuel is injected.

In an example of the implementation of the first aspect, the minimum compressed air excess rate threshold value, the maximum compressed air excess rate threshold value, the minimum bulk compression temperature threshold value, and the maximum bulk compression temperature threshold value all depend on engine operating conditions. It is a parameter to be used. These are parameters that depend on conditions such as engine load, ambient temperature, ambient humidity, and engine speed.

In an example of the implementation of the first aspect, the engine comprises state observing means for determining the excess compressed air rate. This state observing instrument is a system that provides an estimate of the excess compressed air rate in the combustion chamber based on engine input and output measurements. In one example of an embodiment, the state observing means for determining the excess air rate is implemented by a computer.

In one example of the implementation of the first aspect, the engine comprises state observing means for determining bulk compression temperature. This state observing instrument is a system that provides an estimate of the bulk compression temperature of the combustion chamber based on engine input and output measurements. In one example of an embodiment, the state observing means for determining the bulk compression temperature is implemented by a computer.

According to the second aspect, the following method is provided.

It is a method of controlling a large 2-stroke uniflow scavenging internal combustion engine that operates on gas fuel as the main fuel in the gas operation mode.
The engine includes a plurality of combustion chambers defined by a cylinder liner, a piston, and a cylinder cover, a scavenging port for introducing scavenging into the combustion chamber, and a scavenging port arranged in the cylinder liner. It comprises an exhaust outlet located on a cylinder cover and controlled by an exhaust valve, a variable timing exhaust valve drive system, and at least one controller associated with the engine, by the at least one controller.
To determine and control the opening / closing timing of the exhaust valve;
To determine and control the amount of gas fuel introduced into the combustion chamber;
Determining or measuring the average excess compressed air in the combustion chamber;
To determine or measure the bulk compression temperature of the combustion chamber at the start of combustion;
If the average compressed air excess rate determined or measured is below the threshold below the compressed air excess rate, at least one measure for increasing the compressed air excess rate is to be implemented;
If the average compressed air excess rate determined or measured above exceeds the compressed air excess rate upper threshold, at least one measure for reducing the compressed air excess rate is to be implemented;
If the bulk compression temperature determined or measured is below the bulk compression temperature threshold, then at least one measure to raise the bulk compression temperature is to be implemented;
If the bulk compression temperature determined or measured above exceeds the bulk compression temperature threshold, then at least one measure to lower the bulk compression temperature is to be implemented;
Including methods.

These and other aspects will be further clarified by the examples described below.

Hereinafter, various aspects, embodiments, and implementation examples will be described in detail with reference to the exemplary embodiments shown in the drawings.
FIG. 5 is a front view of a large two-stroke diesel engine according to an exemplary embodiment. It is a side view of the large two-stroke engine of FIG. It is the first schematic representation of the large two-stroke engine of FIG. It is sectional drawing of the cylinder frame and the cylinder liner of the engine of FIG. Cylinder covers and exhaust valves are attached and pistons in TDC and BDC are also depicted. It is the second schematic representation of the institution of FIG. It is a schematic representation of the compressed temperature observing means and the compressed air excess rate observing means. A graph is drawn with the horizontal axis representing the bulk cylinder temperature and the vertical axis representing the excess compressed air ratio. It shows the safe zone and the surrounding zone where some action must be taken to return to the safe zone. It is a figure which has drawn the example of the method of controlling a large two-stroke engine.

Detailed explanation

In the following detailed description, the internal combustion engine will be described with reference to the crosshead type large low-speed 2-stroke turbocharged internal combustion engine of the embodiment. 1 to 3 show an example of a turbocharged large low-speed 2-stroke diesel engine. This engine has a crankshaft 8 and a crosshead 9. FIG. 1 is a front view and FIG. 2 is a side view. FIG. 3 is a schematic representation of the turbocharged large low-speed 2-stroke diesel engine of FIGS. 1 and 2 together with its intake system and exhaust system. In this example, the engine has four cylinders in series. A turbocharged, large, low-speed, two-stroke internal combustion engine typically has 4 to 14 cylinders arranged in series. These cylinders are supported on the engine frame 11. Further, such an engine can be used, for example, as a main engine of a ship or a fixed engine for operating a generator in a power plant. The total output of the engine can be, for example, 1,000 kW to 110,000 kW.

The engine in this embodiment is a two-stroke uniflow scavenging engine, in which a scavenging port 18 is provided in the lower region of the cylinder liner 1, and an exhaust valve 4 is arranged in the center of the top of the cylinder liner 1. The scavenging is guided from the scavenging receiver 2 to the scavenging port 18 of each cylinder 1 when the piston is below the scavenging port 18. The gas fuel is introduced from the gas fuel injection valve 30 under the control of the electronic control unit 60. This is done during the ascending stroke of the piston and before the piston passes through the fuel valve 30. The fuel valves are preferably arranged so as to be evenly spaced over the circumference of the cylinder liner. Further, it is preferably arranged near the center in the longitudinal direction of the cylinder liner. Therefore, the injection / introduction of gas fuel is performed when the compression pressure is relatively low. That is, it is performed when the compression pressure when the piston reaches TDC is much lower than the compression pressure.

The piston 10 compresses a mixture of gas fuel and scavenging in the cylinder liner 1. Compression is performed and ignition begins at or near the TDC. Ignition may be initiated, for example, by injecting pilot oil (or other suitable ignition fluid) from the pilot oil fuel valve 50. The pilot oil fuel valve 50 is preferably arranged on the cylinder cover 22. After that, combustion occurs and exhaust gas is generated. Other forms of ignition systems use prechambers, laser ignitions, glow plugs (neither shown), etc. in place of or in addition to pilot oils to facilitate ignition.

When the exhaust valve 4 is opened, the exhaust gas flows to the exhaust receiver 3 through the exhaust duct provided in the cylinder 1, and further advances to the turbine 6 of the turbocharger 5 through the first exhaust pipe 19. From there, the exhaust gas flows through the second exhaust pipe 25 to the economizer 20 and is further discharged into the atmosphere from the outlet 21. The turbine 6 drives the compressor 7 via a shaft. Outside air is supplied to the compressor 9 through the air intake port 12. The compressor 7 sends the compressed scavenging air to the scavenging pipe 13 connected to the scavenging receiver 2. The scavenging of the pipe 13 passes through the intercooler 14 for cooling the scavenging air.

The cooled scavenging air passes through an auxiliary blower 16 driven by an electric motor 17. The auxiliary blower 16 compresses the scavenging airflow when the compressor 7 of the turbocharger 5 is unable to supply the pressure required for the scavenging receiver 2, that is, when the engine is underloaded or partially loaded. When the engine load is high, the turbocharger compressor 7 can supply a fully compressed scavenger so that the auxiliary blower 16 is bypassed by the check valve 15.

FIG. 4 illustrates a cylinder liner 1 designed for a large crosshead two-stroke engine. Depending on the size of the engine, the cylinder liner 1 can be made in various sizes. Typical sizes are 250 mm to 1000 mm in diameter and the corresponding overall length is 1000 mm to 4500 mm.

In FIG. 4, the cylinder liner 1 is mounted on the cylinder frame 23, and the cylinder cover 22 is mounted on the cylinder liner 1. The cylinder liner 1 and the cylinder cover 22 are connected so that gas does not leak between them. In FIG. 4, the state of the piston 10 at the bottom dead center (BDC) and the top dead center (TDC) is shown by a broken line. Of course, these two states do not occur at the same time, and these two states are separated by 180 degrees by the rotation angle of the crankshaft 8. The cylinder liner 1 is provided with a cylinder lubrication hole 25 and a cylinder lubrication line 24. These supply cylinder lubricating oil as the piston 10 passes through the lubrication line 24. A piston ring (not shown) then distributes the cylinder lubricant over the running surface of the cylinder liner.

The pilot oil valve 50 or the prechamber having the pilot oil valve 50 is usually mounted on the cylinder cover 22. Pilot oil valve 50 Normally, one is mounted on each cylinder. The pilot oil valve 50 is connected to a source of pilot oil (not shown). The injection timing of the pilot oil is controlled by the electronic control unit 60.

The fuel valve 30 is mounted on the cylinder liner 1. The fuel valve 30 has a nozzle located substantially on the same surface as the inner surface of the cylinder liner 1. The rear end of the fuel valve 30 protrudes from the outer wall of the cylinder liner 1. Typically, one or two, at most three or four fuel valves 30, are provided in each cylinder liner 1. These are arranged at equal intervals in the circumferential region of the cylinder liner 1. In this embodiment, the fuel valve 30 is arranged at the center of the cylinder liner 1 in the longitudinal direction.

FIG. 4 shows a schematic diagram of a gas fuel supply system including a pressurized gas fuel source 40 connected to each inlet of a plurality of gas fuel valves 30 through a gas fuel supply pipe 41.

FIG. 5 is a schematic representation of an engine similar to the engine of FIG. 2, but the gas exchange device of the engine is depicted in detail. The outside air is taken in at the same atmospheric pressure and temperature as the surroundings, and is sent to the compressor 7 of the turbocharger 5 through the air inlet 12. From the compressor 7, the compressed scavenging air is sent to the branch point 28 through the scavenging pipe 13.

The branch point 28 allows the scavenging to branch through the hot cylinder bypass pipe 29 to the turbine connection 32 of the first exhaust pipe 19. The flow rate of the hot cylinder bypass pipe 29 is controlled by the hot cylinder bypass control valve 31. The hot cylinder bypass control valve 31 is electronically controlled by the controller 60. Opening the hot cylinder bypass 29 or loosening the throttle of the hot cylinder bypass control valve 31 has the effect of increasing the excess compressed air ratio and also has the effect of increasing the bulk compression temperature. On the other hand, closing the hot cylinder bypass 29 or strengthening the throttle of the hot cylinder bypass control valve 31 has the effect of lowering the excess compressed air ratio and lowering the bulk compression temperature.

The scavenging pipe 13 is provided with a first scavenging control valve 33 upstream of the intercooler 14. A second scavenging control valve 34 is provided downstream of the intercooler 14. The scavenging pipe 13 is connected to the scavenging receiver 2. A pipe provided with the auxiliary blower 16 branches from the intercooler 14.

The cold cylinder bypass pipe 35 connects the scavenging receiver 2 to the turbine connecting portion 32 of the first exhaust pipe 19. The flow rate of the cold cylinder bypass pipe 35 is controlled by the cold cylinder bypass control valve 36. The cold cylinder bypass control valve 36 is electronically controlled by the controller 60. Opening the cold cylinder bypass 35 or loosening the throttle of the cold cylinder bypass control valve 36 has the effect of raising the bulk compression temperature.

The cold scavenging bypass tube 37 allows scavenging to escape from the scavenging tube 2 to the surrounding environment 26. The flow rate of the cold scavenging bypass pipe 37 is controlled by the cold scavenging bypass control valve 38. The cold scavenging bypass control valve 38 is electronically controlled by the controller 60. Opening the cold scavenging bypass control valve 39 or loosening the throttle of the cold scavenging bypass control valve 38 has the effect of lowering the scavenging pressure and the effect of lowering the excess compressed air rate. The cold scavenging bypass pipe 37 does not need to branch from the scavenging receiver 2, and may branch from any position in the scavenging pipe 13 as long as it is downstream of the intercooler 14.

An exhaust gas recirculation pipe 42 is connected between the exhaust receiver 3 and the scavenging receiver 2. The exhaust recirculation pipe 42 includes an exhaust recirculation control valve 45, a recirculation exhaust gas cooler 44, and a recirculation exhaust gas blower 43. Both the recirculation exhaust gas blower 43 and the exhaust recirculation control valve 45 are used to adjust the flow rate of the exhaust recirculation pipe 42 under the electronic control of the controller 60. Under normal operating conditions, no exhaust gas flows through the exhaust gas recirculation pipe 42 unless the recirculation exhaust gas blower 43 is active. However, this is because the pressure in the exhaust receiver 3 is usually lower than the pressure in the scavenging receiver 2. Therefore, when the recirculation exhaust gas blower 43 is not active, the exhaust recirculation control valve 45 must be closed. The exhaust gas recirculation pipe 42 does not have to be directly connected to the exhaust receiver 3, and may be connected to some position in the first exhaust pipe 19. Further, the exhaust gas recirculation pipe 42 does not have to be directly connected to the scavenging receiver 2, and may be connected to any position of the scavenging pipe 13 as long as it is downstream of the intercooler 14.

In the exhaust gas recirculation pipe 42, activating the recirculation exhaust gas blower 43 or increasing the rotation speed of the recirculation exhaust gas blower 43 lowers the excess compressed air rate and slightly lowers the bulk compression temperature.

An exhaust bypass pipe 39 branches from the exhaust receiver 3 or the first exhaust pipe 19 and is connected to the surrounding environment 27 with a given back pressure. The exhaust bypass control valve 40 is used to regulate the flow rate of the exhaust bypass pipe 39 under the electronic control of the controller 60.

Opening the exhaust bypass control valve 39 or loosening the throttle of the exhaust bypass control valve 40 reduces the excess compressed air rate in the cylinder.

In an engine equipped with a selective catalytic reduction (SCR) reactor and a reactor bypass valve, the flow rate from the exhaust receiver 3 to the turbine 6 of the turbocharger 5 that passes through the SCR reactor is under the electronic control of the controller 60. Be adjusted.

In FIG. 5, the connections of all the above elements controlled by the controller 60 to the controller 60 are represented using dashed lines.

FIG. 6 is a diagram for explaining the compressed air excess rate observing means 46 and the bulk compressed temperature observing means 47.

The compressed air excess rate observing means 46 is an algorithm implemented by a computer and uses information on scavenging pressure, exhaust valve closing timing, cylinder geometry, stoichiometric air-fuel ratio, and amount of injected gas. .. The compressed air excess rate observing means 46 may be implemented as a part of the controller 60, or may be implemented as a computer or a controller different from the controller 60. The compressed air excess rate observing means 46 provides an estimated value of the compressed air excess rate for the (fully) compressed air-fuel mixture (that is, the air-fuel mixture when the piston 10 is in the TDC) as an output, which is provided by the controller 60. Send to. This estimated value is based on the ratio of the mass of the outside air trapped in the combustion chamber when the exhaust valve 4 is seated divided by the mass of air required to completely burn the total mass of the injected gas. Is.

The bulk compression temperature observing means 47 is also a computer-implemented algorithm that uses information about scavenging pressure, scavenging temperature, exhaust valve closing timing, and crankshaft speed. The bulk compression temperature observing means 47 may also be implemented as a part of the controller 60, or may be implemented as a computer or a controller different from the controller 60. The bulk compression temperature observing means 47 provides Tcomp (Tc), which is an estimated value of the maximum bulk compression temperature of the combustion chamber in the time window from the start of gas injection to the time of pilot injection, as an output. The bulk compression temperature observing means 47 provides this estimate to the controller 60. In some embodiments, Tcomp refers to an estimate when the piston 10 is in the TDC.

FIG. 7 is a graph of the bulk compression temperature (Tcomp) and the excess compressed air ratio (λ). The zone within the boundary defined by the compressed air excess rate lower threshold value, the compressed air excess rate upper threshold value, the bulk compression temperature lower threshold value, and the bulk compression temperature upper threshold value is the normal operation zone 51. In this normal operation zone 51, the controller 60 only needs to supply the fuel required for the current engine load, and does not need to take any measures for changing the bulk compression temperature and the excess compressed air ratio.

However, when the state in the cylinder liner 1 changes and the vehicle enters the action zone 52 away from the normal operation zone 51, the controller 60 takes measures to prevent such a situation from occurring.

For this purpose, the controller 60 is configured as follows.
-If the determined or measured average excess compressed air ratio is below the lower threshold of excess compressed air ratio, implement at least one measure (Compression Air Excess Ratio Increasing Measure; CAERIM) to increase the excess compressed air ratio.
• If the determined or measured average excess compressed air ratio exceeds the threshold for excess compressed air ratio, implement at least one measure (Compression Air Excess Ratio Decreasing Measure; AERDM) to reduce the excess compressed air ratio.
• If the determined or measured bulk compression temperature is below the bulk compression temperature threshold, implement at least one measure (Bulk Compression Temperature Increasing Measure; BCTIM) to increase the bulk compression temperature.
• If the determined or measured bulk compression temperature exceeds the bulk compression temperature threshold, implement at least one measure (BCTDM) to lower the bulk compression temperature.

By taking these measures, the controller 60 keeps the state in the cylinder liner 1 in the normal zone 51. It is only temporary that the state inside the cylinder liner 1 goes out of the normal zone 51 and enters the action zone 52. The action zone 52 is surrounded by the danger zone 53. The danger zone 53 is a zone where pre-ignition and misfire are likely to occur.

The boundaries of zones 51, 52, and 53 are defined by the upper and lower thresholds of the bulk compression temperature and the excess compressed air ratio. These thresholds can be set empirically and experimentally for individual engines, for example by trial and error or computer simulation of the engine cycle.

If the observation means 46, 47 indicate that both the bulk compression temperature and the excess compressed air rate deviate from the normal operating zone 51, the controller 60 seeks to return the cylinder liner state to the normal operating zone 51. , Both a measure of returning the bulk compression temperature to the normal operation zone 51 and a measure of returning the compressed air excess rate to the normal operation zone 51 are carried out.

Adjust the exhaust bypass control valve 40 (move the exhaust bypass control valve 40 to the open position) and open the exhaust bypass (EGB) pipe 39 (from the inlet of the turbocharger turbine to the turbine outlet or Increasing the flow to the outside environment) results in a significant reduction in scavenging pressure and thus a significant reduction in the mass of air trapped in the combustion chamber. Therefore, this measure is appropriate as a measure for reducing the excess compressed air rate. This measure has only a minor effect on the bulk compression temperature. Even when the engine has a plurality of turbochargers, one EGB may be sufficient by connecting the EGB to the exhaust receiver. However, it is necessary to select and connect a place where multiple flows to the exhaust receiver are properly mixed.

Opening the hot cylinder bypass control valve 31 (increasing the flow from the turbocharger compressor outlet to the turbocharger turbine inlet) results in an increase in the excess compressed air rate and bulk compression temperature in the combustion chamber.

Opening the scavenging bypass control valve 38 creates a flow from the scavenging receiver 2 to the compressor inlet or the external environment. This has a qualitatively similar effect on the compressed air excess rate as the exhaust bypass. However, the scavenging process has different effects (and thus the bulk compression temperature of the combustion chamber). The effect of opening the scavenging bypass control valve 38 on the condition of the combustion chamber appears more quickly than in the exhaust bypass.

Opening the cold cylinder bypass 36 increases the flow from the exhaust receiver to the turbocharger turbine inlet. This results in an increase in bulk compression temperature. However, there is almost no effect on the excess compressed air rate.

The exhaust valve closing timing determines the ratio of the compression pressure to the scavenging pressure in the combustion chamber. Changing this timing has a great effect on both the excess compressed air ratio in the combustion chamber and the bulk compression temperature.

The timing of opening the exhaust valve affects the initial stage of the scavenging process in the combustion chamber. Changing this timing affects engine efficiency and the scavenging process. As the scavenging process changes, so does the bulk temperature. If the exhaust valve 4 opens very quickly, no flow to the scavenging receiver 2 occurs when the piston 10 opens the scavenging port 18. If the exhaust valve 4 opens very slowly, a large flow to the scavenging receiver 2 occurs when the piston 10 opens the scavenging port 18. These measures change the scavenging process and change the rate at which the'dirty / hot'gas produced by combustion mixes into the next combustion stroke.

That is, as the timing of opening the exhaust valve 4 is delayed, the amount of'dirty / hot'gas mixed from the previous combustion increases, the excess compressed air ratio decreases, and the bulk compression temperature rises. Further, as the exhaust valve 4 is opened earlier, the amount of dirty / hot gas mixed from the previous combustion decreases, the excess compressed air ratio increases, and the bulk compression temperature decreases. When the exhaust valve 4 is closed early to increase the compression pressure, the amount of gas flowing out from the exhaust valve 4 is reduced, and a large amount of gas stays in the combustion chamber. This increases the excess air rate. When the compression pressure is high, the amount of work for compression performed by the piston 10 in the combustion chamber increases. This raises the temperature of the gas in the combustion chamber.

Increasing the flow rate of exhaust gas recirculation increases the flow rate of exhaust gas from the exhaust receiver 3 to the outlet (or scavenging receiver) of the turbocharger compressor. The flow rate of the exhaust gas recirculation can be increased by activating the exhaust gas recirculation blower 43 or increasing the rotation speed of the exhaust gas recirculation blower 43. As the flow rate of exhaust gas recirculation increases, the excess compressed air rate decreases, and the bulk compression temperature in the combustion chamber also decreases slightly.

When the rotation speed of the auxiliary blower 16 is increased, the excess compressed air ratio in the combustion chamber is slightly increased, and the bulk compression temperature is decreased.

For engines with water injection, injecting water into the combustion chamber during the compression stroke lowers the bulk compression temperature.

Scavenging cooler bypass (not shown): Bypassing the intercooler 14 significantly increases the bulk compression temperature of the combustion chamber. On the other hand, it has a small effect on the excess compressed air rate.

In an engine with a variable geometry turbine 6, reducing the turbine flow area results in a reduction in scavenging pressure, thus reducing the mass of air trapped in the combustion chamber. Therefore, this measure is appropriate as a measure for reducing the excess compressed air rate. This measure has only a minor effect on the bulk compression temperature.

In the case of an engine equipped with a turbocharger assist, increasing the assist and increasing the speed of the turbocharger 5 brings about an increase in the compressed air excess rate. This measure has only a minor effect on the compression temperature.

Changing the ratio of gas fuel to liquid fuel (for example, marine diesel oil) is one of the measures. Decreasing the proportion of gas fuel in the total fuel energy injected increases the excess compressed air rate. As the proportion of gas fuel decreases, the proportion of liquid fuel increases, which ensures that the crankshaft torque is maintained.

For engines with a heat exchanger inside the exhaust receiver (or for engines with a heat exchanger that receives part of the exhaust gas), increasing the amount of exhaust gas passing through the heat exchanger, ie from the exhaust gas Extracting a lot of heat results in a decrease in scavenging pressure, thus reducing the amount of air trapped in the combustion chamber. Therefore, this measure is appropriate as a measure for reducing the excess compressed air rate. This measure has only a minor effect on the bulk compression temperature. Heat exchangers can be used to generate steam.

For engines with hot scavenging bypass, opening the hot scavenging bypass control valve creates or increases the flow from the compressor outlet to the external environment or compressor inlet. This greatly reduces the scavenging pressure. Therefore, the amount of air trapped in the combustion chamber is reduced. Therefore, this measure is appropriate as a measure for reducing the excess compressed air rate. This measure has only a minor effect on the bulk compression temperature.

In a certain embodiment, the compressed air excess rate lower threshold value, the compressed air excess rate upper threshold value, the bulk compression temperature lower threshold value, and the bulk compression temperature upper threshold value are all parameters depending on the engine operating conditions. Engine operating conditions are determined by parameters such as engine load, ambient temperature, ambient humidity, and engine speed. These operating condition parameters can be used by the controller 60 through, for example, a look-up table, an algorithm, a combination thereof, or the like.

Depending on the embodiment, the controller 60 is configured as follows.
-If the determined or measured average excess compressed air rate is below the minimum excess compressed air rate threshold, which is lower than the lower threshold value of excess compressed air rate, further measures are taken to increase the excess compressed air rate. This further measure may be selected from, for example, the measures described above.
-If the determined or measured average excess compressed air rate exceeds the maximum excess compressed air rate threshold, which is higher than the upper threshold value, then further measures are taken to reduce the excess compressed air rate.
• If the determined or measured bulk compression temperature is below the minimum bulk compression temperature threshold below the bulk compression temperature threshold, further measures are taken to raise the bulk compression temperature.
• If the determined or measured bulk compression temperature exceeds the maximum bulk compression temperature threshold, which is higher than the bulk compression temperature upper threshold, further measures are taken to lower the bulk compression temperature.

These further measures are taken when the state of the combustion chamber moves from the action zone 52 to the danger zone surrounding the action zone. The controller 60 is configured to take as many necessary actions as possible in order to return the state of the combustion chamber to the action zone 52 and further back to the normal operation zone 51.

The controller 60 is configured to minimize taking action (ie, taking the measures described above) to return the operating state of the engine to the normal operating zone 51. Therefore, the controller 60 is configured to stop all of the above measures when the state of the combustion chamber returns to the normal operating zone.

FIG. 8 is a flowchart for explaining a process of operating the engine according to the above-described configuration of the controller 60.

When the process begins, the controller investigates whether the excess compressed air rate is below the lower threshold. If the result of the investigation is No, the controller proceeds to investigate whether the excess compressed air ratio deviates from the upper threshold value. If the result of the investigation is Yes, the controller 60 implements one of the above measures to increase the excess compressed air rate and investigates whether the excess compressed air rate is below the minimum threshold. If the result of the investigation is No, the controller proceeds to investigate whether the excess compressed air ratio deviates from the upper threshold value. If the result of the investigation is Yes, the controller 60 further executes the above-mentioned measures for increasing the excess compressed air ratio, and proceeds to investigate whether the excess compressed air ratio deviates from the upper threshold value.

The controller 60 investigates whether the excess compressed air ratio is higher than the upper threshold value. If the result of the investigation is No, the controller proceeds to investigate whether the bulk compression temperature deviates from the lower threshold. If the result of the investigation is Yes, the controller 60 implements one of the above measures to reduce the excess compressed air rate and investigates whether the excess compressed air rate is higher than the maximum threshold. If the result of the investigation is No, the controller proceeds to investigate whether the bulk compression temperature deviates from the lower threshold. If the result of the investigation is Yes, the controller 60 further implements the above-mentioned measures for increasing the excess compressed air rate, and proceeds to investigate whether the bulk compression temperature deviates from the lower threshold value.

The controller 60 investigates whether the bulk compression temperature is below the lower threshold. If the result of the investigation is No, the controller proceeds to the next step, investigation of whether the bulk compression temperature is higher than the upper threshold. If the result of the investigation is Yes, the controller 60 implements measures to raise the bulk compression temperature and investigates whether the bulk compression temperature is below the minimum threshold. If the result of the investigation is No, the process of the controller 60 proceeds to the step of investigating whether the bulk compression temperature is higher than the upper threshold value. If the result of the investigation is Yes, the controller 60 implements the measures described above for raising the bulk compression temperature and proceeds to the step of investigating whether the bulk compression temperature deviates from the upper threshold.

The controller 60 investigates whether the bulk compression temperature deviates from the upper threshold. If the result of the investigation is No, the controller 60 returns to the step of investigating whether the excess compressed air ratio is lower than the lower threshold value. If the result of the investigation is Yes, the controller 60 implements any of the measures described above for lowering the bulk compression temperature. The controller 60 then investigates whether the bulk compression temperature is higher than the maximum threshold. If the result of the investigation is No, the controller 60 returns to the step of investigating whether the excess compressed air ratio is lower than the lower threshold value. If the result of the investigation is Yes, the controller 60 further implements the above-mentioned measures for lowering the bulk compression temperature, and then moves to the step of investigating whether the excess compressed air ratio is lower than the lower threshold value.

In some embodiments, the controller may have an algorithm or look-up to determine which of the measures available to raise or lower the bulk compression temperature is the best one in the current engine operating conditions. Information such as tables is provided. Further, the controller 60 includes an algorithm, a look-up table, etc. for determining which of the measures available for increasing or decreasing the excess compressed air rate is the optimum measure under the current engine operating conditions. Information is provided.

Many aspects and implementations have been described with some examples. However, considering the specification, drawings, and claims of the present application, those skilled in the art have many variations in carrying out the inventions described in the claims in addition to the described examples. You will be able to understand and embody that. The terms "prepared", "have", and "include" described in the claims do not preclude the existence of elements or steps that are not described. Even if it is not explicitly stated that the number of elements described in the claims is plural, it does not exclude the existence of multiple elements. The functions of some of the elements described in the claims may be performed by a single processor, controller, or other unit. Even if some matters are described in separate dependent claims, it does not exclude the combination of these, and the combination can be profitable.

The codes used in the claims should not be construed as limiting the scope of the invention.

Claims (12)

A large 2-stroke uniflow scavenging internal combustion engine that operates on gas fuel as the main fuel in gas operation mode.
With multiple combustion chambers, each defined by a cylinder liner, piston, and cylinder cover;
A scavenging port for introducing scavenging into the combustion chamber, and a scavenging port arranged in the cylinder liner;
With an exhaust outlet located on the cylinder cover and controlled by an exhaust valve;
With variable timing exhaust valve drive system;
With at least one controller associated with the institution;
The at least one controller comprises
Determine and control the opening and closing timing of the exhaust valve;
Determine and control the amount of gas fuel introduced into the combustion chamber;
Determine or measure the average excess compressed air in the combustion chamber;
Determine or measure the bulk compression temperature of the combustion chamber at the start of combustion;
If the average compressed air excess rate determined or measured above is below the threshold below the compressed air excess rate, at least one measure to increase the compressed air excess rate is implemented;
If the average compressed air excess rate determined or measured above exceeds the compressed air excess rate upper threshold, at least one measure is implemented to reduce the compressed air excess rate;
If the bulk compression temperature determined or measured above is below the bulk compression temperature threshold, at least one measure to raise the bulk compression temperature is implemented;
If the bulk compression temperature determined or measured above exceeds the bulk compression temperature threshold, at least one measure to lower the bulk compression temperature is implemented;
An institution that is structured so that. The at least one controller includes, or is connected to, the compressed air excess rate observing means for determining the instantaneous average compressed air excess rate in the combustion chamber, according to claim 1. The listed institution. The first or second claim, wherein the at least one controller comprises or is connected to a bulk compression temperature observing means for determining the instantaneous bulk compression temperature of the combustion chamber. organ. The institution according to any one of claims 1 to 3, at least one measure for increasing the excess compressed air rate is selected from the following measures:
-Advance the timing of closing the exhaust valve;
-If the engine is equipped with a scavenging bypass, close the scavenging bypass or tighten the throttle of the scavenging bypass valve;
-If the engine is equipped with a hot cylinder bypass, open the hot cylinder bypass control valve or weaken the throttle of the hot cylinder bypass control valve;
-If the institution has an auxiliary blower, activate the auxiliary blower;
• If the engine is equipped with a variable geometry turbine, reduce the effective turbine flow path area;
-If the engine is equipped with turbocharger assist, increase the speed of the turbocharger. The institution according to any one of claims 1 to 4, at least one measure for reducing the excess compressed air rate is selected from the following measures:
・ Delay the timing of closing the exhaust valve;
-If the engine is equipped with a scavenging bypass, open the scavenging bypass or weaken the throttle of the scavenging bypass control valve;
-If the engine is equipped with an exhaust bypass, open the exhaust bypass control valve or weaken the throttle of the exhaust bypass control valve;
-If the engine is equipped with an exhaust gas recirculation pipe, activate the exhaust gas recirculation blower of the exhaust gas recirculation pipe or increase the rotation speed of the exhaust gas recirculation blower;
• If the engine is equipped with a variable geometry turbine, increase the effective turbine flow path area;
-If the engine is equipped with a liquid fuel ignition system, reduce the proportion of gas fuel and increase the proportion of liquid fuel;
-If the engine has a heat exchanger between the exhaust valve and the turbocharger inlet, increase the amount of heat extracted from the exhaust by the heat exchanger;
-If the engine is equipped with turbocharger assist, reduce the turbocharger assist. The institution according to any one of claims 1 to 5, at least one measure for raising the bulk compression temperature is selected from the following measures:
-If the engine is equipped with a cold cylinder bypass, open the cold cylinder bypass control valve or weaken the throttle of the cold cylinder bypass control valve;
-If the engine is equipped with a hot cylinder bypass, open the hot cylinder bypass control valve or weaken the throttle of the hot cylinder bypass control valve;
-If the engine is equipped with a scavenging cooler bypass, open the scavenging cooler bypass control valve or weaken the throttle of the scavenging cooler bypass;
-Advance the timing of closing the exhaust valve. The institution according to any one of claims 1 to 6, at least one measure for lowering the bulk compression temperature is selected from the following measures:
-Temporarily suppress changing the timing of closing the exhaust valve;
・ Delay the timing of closing the exhaust valve;
-If the engine is equipped with a hot cylinder bypass, close the hot cylinder bypass control valve or throttle the hot cylinder bypass control valve;
-If the institution has an auxiliary blower, activate the auxiliary blower;
-If the engine is equipped with water injection, inject water into the combustion chamber during the compression stroke. The at least one controller provides further measures to increase the compressed air excess rate when the determined or measured average compressed air excess rate is below the minimum compressed air excess rate threshold lower than the compressed air excess rate lower threshold. The institution according to any of claims 1 to 7, which is configured to perform. The at least one controller provides further measures to reduce the compressed air excess rate when the determined or measured average compressed air excess rate exceeds the maximum compressed air excess rate threshold higher than the compressed air excess rate upper threshold. The institution according to any of claims 1-8, which is configured to perform. The at least one controller is configured to implement further measures to raise the bulk compression temperature if the determined or measured bulk compression temperature is below the minimum bulk compression temperature threshold below the bulk compression temperature threshold. The institution according to any one of claims 1 to 9. The at least one controller is configured to implement further measures to lower the bulk compression temperature if the determined or measured bulk compression temperature exceeds the maximum bulk compression temperature threshold higher than the bulk compression temperature upper threshold. The institution according to any one of claims 1 to 10. A method of controlling a large two-stroke uniflow scavenging internal combustion engine that operates on gas fuel as the main fuel in the gas operation mode.
With multiple combustion chambers, each defined by a cylinder liner, piston, and cylinder cover;
A scavenging port for introducing scavenging into the combustion chamber, and a scavenging port arranged in the cylinder liner;
With an exhaust outlet located on the cylinder cover and controlled by an exhaust valve;
With variable timing exhaust valve drive system;
With at least one controller associated with the institution;
With
By the at least one controller
To determine and control the opening / closing timing of the exhaust valve;
To determine and control the amount of gas fuel introduced into the combustion chamber;
Determining or measuring the average excess compressed air in the combustion chamber;
To determine or measure the bulk compression temperature of the combustion chamber at the start of combustion;
If the average compressed air excess rate determined or measured is below the threshold below the compressed air excess rate, at least one measure for increasing the compressed air excess rate is to be implemented;
If the average compressed air excess rate determined or measured above exceeds the compressed air excess rate upper threshold, at least one measure for reducing the compressed air excess rate is to be implemented;
If the bulk compression temperature determined or measured above is below the bulk compression temperature threshold, then at least one measure to raise the bulk compression temperature is to be implemented;
If the bulk compression temperature determined or measured above exceeds the bulk compression temperature threshold, then at least one measure to lower the bulk compression temperature is to be implemented;
Including methods.