Marine engine control device

Abstract

To suppress the occurrence of knocking when the load of an engine is rapidly increased in a control device for a marine engine using gas fuel.SOLUTION: The marine engine control device includes an engine 1 using gas fuel, and a control part 20 for controlling the engine 1. A control part 20 can switch a first tuning state and a second tuning state in which fuel economy is worse than the first tuning state, and switches the first tuning state to the second tuning state when detecting a sign of load increase of an engine 1 during operation in the first tuning state.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a control device for a marine engine. [Background technology]

[0002] Marine engines are subject to the SO225 standard in accordance with the international treaty (MARPOL Annex VI) administered by the International Maritime Organization (IMO). X or NO X Emissions of SO are regulated in certain marine areas (Emission Control Areas (ECAs)). X or NO X Emissions of 1,000 tonnes of crude oil are subject to particularly strict regulations. Emission regulations in ECAs are also called Tier 3, and are distinguished from Tier 2, which are emission regulations in other sea areas (general sea areas).

[0003] The following Patent Document 1 describes a method for controlling NOx emissions depending on the tuning state of a marine diesel engine. X In diesel engines, NO emissions are reduced. X There is a trade-off between emissions and fuel efficiency, X Tuning to reduce NO emissions will result in a decrease in fuel efficiency, while tuning to improve fuel efficiency will result in a decrease in NO emissions. X Therefore, in the invention of the same document, the first tuning state is compared with a state in which fuel economy is worse than the first tuning state and NO emissions are increased. X In general waters (Tier 2), the first tuning state allows for good fuel economy, while in ECAs (Tier 3), the second tuning state allows for low NO emissions. X emissions can be reduced to below the Tier 3 standard.

[0004] Marine engines have traditionally used heavy oil, but in response to recent demands for environmental protection, XThe use of gas fuels (e.g., LNG) that emit less carbon dioxide and soot is increasing. It is known that gas engines experience misfire and knocking (abnormal combustion) regions, as shown in Figure 2, where the horizontal axis represents the air-fuel ratio (excess air ratio) and the vertical axis represents the brake mean effective pressure (BMEP). When a ship is sailing, it is necessary to adjust the air-fuel ratio to avoid entering the misfire and knocking regions. It is known that fuel efficiency can be improved by adjusting the air-fuel ratio as fuel-rich as possible. Therefore, fuel efficiency can be improved by lowering the air-fuel ratio as much as possible (increasing the fuel ratio) within the range that does not involve entering the knocking region shown in Figure 2.

[0005] Gas engines such as those described above are not limited to main engines that drive propellers, but are also sometimes used as generator engines to drive onboard loads. In this case, when the onboard load (e.g., an electric motor) is started, power consumption temporarily increases, which in turn temporarily increases the load on the gas engine. At this time, the amount of gas fuel supplied is increased to increase the gas engine's output. At the same time, the amount of air supplied must also be increased to adjust the air-fuel ratio and maintain good combustion conditions. However, because air is supplied to the gas engine by rotating the turbocharger, there is a time lag before the amount of air supplied increases. Therefore, when the load on the gas engine increases as described above, the amount of air supplied temporarily becomes insufficient, causing the air-fuel ratio to decrease (the proportion of fuel increases). If the air-fuel ratio is set low to reduce fuel consumption, the air-fuel ratio decreases as the load on the gas engine increases, as indicated by arrow A in Figure 2, shifting the engine to the left, making it more susceptible to knocking.

[0006] For example, in Patent Document 2 listed below, the ignition timing is delayed when the degree of increase in engine load is relatively large. This increases the excess air ratio margin up to the knocking limit, making it possible to increase the actual fuel injection amount by a large margin, and as a result, it is said that it is possible to improve load responsiveness while suppressing knocking. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Patent Publication No. 2021-32209 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-133464 Summary of the Invention [Problem to be solved by the invention]

[0008] However, when the curve showing the tuning state of the air-fuel ratio is set near the knocking region, it is difficult to prevent the occurrence of knocking by using the technique of delaying the ignition timing as in Patent Document 2.

[0009] SUMMARY OF THE INVENTION It is therefore an object of the present invention to suppress the occurrence of knocking when the engine load increases suddenly in a control device for a marine engine that uses gas fuel. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems, the present invention provides a control device for a marine engine including a gas-fueled engine and a control unit that controls the engine, the control unit is capable of switching between a first tuning state and a second tuning state in which fuel economy is worse than that of the first tuning state, A control device for a marine engine is provided that switches to the second tuning state when a sign of an increase in the load on the engine is detected while the engine is operating in the first tuning state.

[0011] In this way, the control device according to the present invention switches to the second tuning state when a "sign" of an engine load increase is detected while the engine is operating in the first tuning state, which is fuel-efficient. That is, when a sign of an engine load increase is detected, the curve showing the relationship between the air-fuel ratio and the brake mean effective pressure (tuning state) shown in FIG. 2 is shifted toward a side where the air-fuel ratio increases, i.e., toward a side away from the knocking region. This makes it difficult to enter the knocking region even if the air-fuel ratio decreases as the engine load increases, thereby suppressing the occurrence of knocking.

[0012] The control device may include a generator driven by the engine and a drive unit (for example, an electric motor) supplied with power generated by the generator. In this case, if a sign of the drive unit starting is detected while the engine is operating in the first tuning state, the control device may switch to the second tuning state, thereby preventing knocking.

[0013] For example, the control device may include a tank and a pressure detection unit that detects the pressure in the tank, and the pressure detection unit may be configured to detect a reference value and a preliminary reference value that is higher than the reference value. In this case, when the pressure detection unit detects that the pressure in the tank has dropped to the preliminary reference value, the control device may switch from the first tuning state to the second tuning state, thereby suppressing knocking.

[0014] An electric motor of a full voltage start type consumes much more power at startup than other types (for example, star-delta start type). Therefore, when the drive unit is an electric motor of a full voltage start type, the load applied to the engine increases significantly when the electric motor is started, making knocking more likely to occur, and therefore application of the present invention is particularly effective.

[0015] In the above control device, for example, the set value of the air-fuel ratio of the mixture supplied to the engine in the first tuning state can be made lower than the set value of the air-fuel ratio of the mixture supplied to the engine in the second tuning state, thereby improving the fuel efficiency of the engine when operated in the first tuning state.

[0016] Furthermore, in the above control device, by lowering the engine speed in the first tuning state compared to the engine speed in the second tuning state, it is possible to improve the fuel efficiency of the engine when it is operated in the first tuning state. Engine output is calculated by multiplying the break mean effective pressure by the engine speed. When the engine speed is reduced for energy-saving operation, it is necessary to increase the break mean effective pressure in order to maintain constant engine output. In this case, as described above, by shifting the curve showing the relationship between the air-fuel ratio and the break mean effective pressure (tuning state) toward a side where the air-fuel ratio is larger, it becomes more difficult to enter the knocking region, thereby suppressing the occurrence of knocking.

[0017] The above-described control device can be provided in a power generation system that is mounted on a ship, for example, and supplies power to loads on the ship. [Effects of the Invention]

[0018] As described above, according to the present invention, in a control device for a marine engine that uses gas fuel, it is possible to suppress the occurrence of knocking when the engine load increases suddenly. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a block diagram of a control device for a marine engine according to an embodiment of the present invention. FIG. [Figure 2] 1 is a graph showing the relationship between the air-fuel ratio of an engine and the brake mean effective pressure (BMEP). [Figure 3] FIG. 4 is a flowchart showing a procedure for switching between a first tuning state and a second tuning state. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0021] A power generation system having a marine engine control device according to one embodiment of the present invention is installed on a ship and supplies power to onboard loads. As shown in Fig. 1, this power generation system includes an engine 1, a generator 2 driven by the engine 1, and a control unit 20 that controls the engine 1. In this embodiment, a plurality of engines 1 and generators 2 (three in the illustrated example) are provided.

[0022] The engine 1 is a dual-fuel engine that can selectively use gas fuel such as LNG and liquid fuel such as heavy oil. In this embodiment, a case where gas fuel is used as the fuel for the engine 1 will be described. The engine 1 is a power-generating engine that is used only to drive the generator 2. The generator 2 has a rotor and a stator, and by rotating the rotor, electric power is generated in a coil provided in the stator. The rotor of the generator 2 is connected to the output shaft of the engine 1, and the two rotate together.

[0023] The engine 1 is provided with a governor 8. The governor 8 controls the rotation speed of the engine 1 based on instructions from the control unit 20. The governor 8 in this embodiment has a governor motor that adjusts the amount of fuel supplied to the engine 1. In this embodiment, the actual rotation speed of the generator 2 is transmitted to the control unit 20, and the control unit 20 controls the governor 8 based on this information. For example, when the power consumption of the onboard loads increases, the load on the generator 2 increases and the rotation speed decreases. At this time, the governor 8 increases the amount of fuel supplied to the engine 1 to increase the output, thereby maintaining the rotation speed of the generator 2, i.e., the frequency of the power (AC current) generated by the generator 2, constant.

[0024] In this embodiment, a turbocharger 30 is provided to adjust the amount of air supplied to the engine 1. The turbocharger 30 has a turbine 31 and a compressor 32. The turbine 31 is rotated by exhaust air from the engine 1, which rotates the compressor 32 integrally with the turbine 31 to compress the air and supply it to the engine 1. The control unit 20 controls the air-fuel ratio of the engine 1 by adjusting the amount of air supply (air supply pressure) supplied from the turbocharger 30 to the engine 1 and the amount of fuel supplied from the governor 8 to the engine 1.

[0025] The generator 2 is connected to multiple electrical devices (drive units) constituting the ship's loads via a main bus 3 of the switchboard. These electrical devices are directly connected to the main bus 3 without going through a frequency control device such as an inverter. The electrical devices are, for example, electric motors. In the illustrated example, electric motors 4a to 4d that drive a compressor 5 and an electric motor 4e that drives a fan 6 are provided. The compressor 5 compresses gas (air, nitrogen gas, etc.) and stores it in a tank 7. The fan 6 supplies air as needed to a turbocharger 50 that supplies air to the main engine 10. The electric motors 4a to 4e are full-voltage starting (so-called direct start) motors that are directly supplied with power from the main bus 3. This type of motor is relatively small, and at start-up, a starting current that is 5 to 8 times the rated current flows through it. In addition, electrical equipment connected to the main busbar 3 includes an electric pump for supplying lubricating oil and cooling water to the main engine 10, a ventilator for ventilating and air-conditioning the cabin, lighting inside the ship, and a drive motor for operating the bow thruster (not shown).

[0026] Each tank 7 is connected to equipment (not shown) that uses the compressed gas stored therein. Therefore, the compressed gas stored in the tanks 7 gradually decreases as it is used by each equipment, and the pressure inside the tanks 7 drops. When the compressed gas inside any of the tanks 7 falls below a reference amount, the compressor 5 connected to that tank 7 is driven to fill that tank 7 with compressed gas. To this end, the tanks 7 are provided with pressure detection units that detect the internal pressure. In the illustrated example, each tank 7 is provided with a first pressure sensor 41 and a second pressure sensor 42 as pressure detection units. The first pressure sensor 41 detects when the pressure inside the tank 7 has dropped to a reference value. The second pressure sensor 42 detects when the pressure inside the tank 7 has dropped to a preliminary reference value that is higher than the reference value.

[0027] In this embodiment, a turbocharger 50 is provided to supply compressed air to the main engine 10. The turbocharger 50 has a turbine 51 and a compressor 52. The turbine 51 is rotated by exhaust air from the main engine 10, which rotates the compressor 52 integrally to compress the air and supply it to the main engine 10. When the amount of air supplied from the compressor 52 to the main engine 10 falls below a reference value, the fan 6 is driven to supply supplementary compressed air to the compressor 52. For this purpose, an air amount detection unit is provided in the piping 11 connecting the compressor 52 and the main engine 10. In the illustrated example, a first pressure sensor 61 and a second pressure sensor 62 are provided as the air amount detection unit. The first pressure sensor 61 detects when the pressure in the piping 11 drops to a reference value. The second pressure sensor 62 detects when the pressure in the piping 11 drops to a preliminary reference value higher than the reference value.

[0028] The control unit 20 can switch the tuning state of the engine 1 between a first tuning state and a second tuning state. The first tuning state is tuned so that the air-fuel ratio is relatively lower than in the second tuning state, i.e., the proportion of fuel is higher. The first tuning state has lower (better) fuel economy and methane slip than the second tuning state, but has higher NOx emissions than the second tuning state. For example, the first tuning state and the second tuning state can be switched by adjusting one or both of the amount of air supplied from the turbocharger 30 and the amount of fuel supplied from the governor 8.

[0029] FIG. 2 shows the state of engine 1 when the air-fuel ratio (excess air ratio) of the mixture supplied to engine 1 and the break mean effective pressure (load on engine 1) are changed. As shown in the figure, if the air-fuel ratio is too low (too rich), engine 1 will knock, and if the air-fuel ratio is too high (too lean), engine 1 will misfire. The range of air-fuel ratios within which knocking and misfire do not occur is the operable range (scattered region) within which engine 1 can operate. The greater the load on the engine, the smaller the range of air-fuel ratios within the operable range. Within this operable range, a first tuning state is provided in which the air-fuel ratio is set to a relatively low value (i.e., the proportion of fuel in the mixture is high), and a second tuning state is provided in which the air-fuel ratio is set to a relatively high value (i.e., the proportion of fuel in the mixture is low).

[0030] For example, when sailing in an emission control area (ECA), the control unit 20 sets the engine 1 in the second tuning state, and the NO X On the other hand, when sailing in general sea areas, the control unit 20 sets the engine 1 in the first tuning state to improve the fuel efficiency of the engine 1. In this way, by operating the engine 1 in the first tuning state in sea areas other than those subject to emission control, it is possible to reduce fuel consumption and lower fuel costs.

[0031] For example, if the compressed gas in any of the tanks 7 falls below a predetermined level while the vessel is navigating in the first tuning state, i.e., if the first pressure sensor 41 provided in the tank 7 detects that the pressure in the tank 7 has reached a reference value, the electric motor connected to that tank 7 is started, and the compressor 5 compresses the air and fills it into the tank 7. When the electric motor is started, power consumption temporarily increases. In particular, in this embodiment, the electric motor is a full-voltage start type, so a current five to eight times the rated current flows. This temporarily increases the load on the engine 1, so the control unit 20 issues a command to the governor 8 to increase the fuel supplied to the engine 1 in order to increase the output of the engine 1.

[0032] At this time, it is ideal to increase the brake mean effective pressure (BMEP) along the tuning curve for the first tuning state shown in Fig. 2 by increasing the amount of air supplied together with the increase in the amount of fuel supplied (see arrow a). However, in reality, because the turbocharger 30 is rotated to increase the amount of air supplied, a time lag occurs between the increase in the amount of fuel supplied and the increase in the amount of air supplied, causing the air-fuel ratio to temporarily decrease (see arrow A in Fig. 2). At this time, the curve representing the first tuning state is closer to the knocking region than the curve representing the second tuning state, and therefore the temporary decrease in the air-fuel ratio makes it easier for the engine to enter the knocking region.

[0033] Therefore, in this embodiment, a sign detection unit is provided to detect a sign of an increase in the load on the engine 1, specifically, a sign of the start of any of the electrical devices constituting the onboard loads, particularly a sign of the start of any of the electric motors 4a to 4e. In this embodiment, a second pressure sensor 42 is provided in each tank 7 as a sign detection unit (see FIG. 1). The second pressure sensor 42 detects a preliminary reference value higher than the reference value for starting to fill the compressed gas. While the ship is sailing in the first tuning state, if the second pressure sensor 42 provided in any tank 7 detects that the pressure in that tank 7 has dropped to the preliminary reference value, the detection signal is transmitted to the control unit 20, and the control unit 20 automatically switches the tuning state of the engine 1 from the first tuning state to a second tuning state with a higher air-fuel ratio. As a result, the tuning curve (see the dotted line in FIG. 2) indicating the set value of the air-fuel ratio shifts to the right in the figure, moving away from the knocking region.

[0034] Thereafter, the amount of compressed gas in the tank 7 further decreases, and when the first pressure sensor 41 detects that the pressure in the tank 7 has dropped to a reference value, the electric motor is started and the compressor 5 is driven to fill the tank 7 with compressed air. At this time, the air-fuel ratio temporarily drops due to an increase in the load on the engine 1 (see arrow B1 in FIG. 2), but because the state has already switched to the second tuning state, it is less likely to enter the knocking region, and the occurrence of knocking is suppressed. Thereafter, the amount of air charged increases, raising the air-fuel ratio, and the state returns to the second tuning state (see arrow B2).

[0035] Furthermore, in this embodiment, a second pressure sensor 62 is provided as a sign detection means in the pipe 11 that supplies air from the turbocharger 50 to the main engine 10 (see FIG. 1). The second pressure sensor 62 detects a preliminary reference value that is higher than the reference value for starting to replenish air to the compressor 52. If the second pressure sensor 62 provided in the pipe 11 detects that the pressure has dropped to the preliminary reference value while the ship is sailing in the first tuning state, this detection signal is transmitted to the control unit 20, and the control unit 20 switches the tuning state of the engine 1 from the first tuning state to a second tuning state in which the air-fuel ratio is higher than the first tuning state. As a result, the tuning curve (see the dotted line in FIG. 2) that indicates the set value of the air-fuel ratio shifts to the right in the figure, moving away from the knocking region.

[0036] Thereafter, when the first pressure sensor 61 provided in the pipe 11 detects that the pressure in the pipe 11 has dropped to a reference value, the electric motor 4e starts to drive the fan 6. At this time, the air-fuel ratio temporarily drops due to an increase in the load on the engine 1 (see arrow B1 in FIG. 2), but because the engine has already switched to the second tuning state, it is less likely to enter the knocking region, and the occurrence of knocking is suppressed. Thereafter, the amount of air charged increases, raising the air-fuel ratio, and the engine returns to the second tuning state (see arrow B2).

[0037] 3 shows a flow diagram of the above-described switching of tuning states. When the second pressure sensors 42 of the four tanks 7 and the second pressure sensor 62 of the piping 11 are all OFF (step S1), i.e., when the pressures in the four tanks 7 and the piping 11 are all higher than the preliminary reference value and the ship is sailing in a general sea area (step S2), the engine 1 is operated in the first tuning state (step S3). On the other hand, when any of the second pressure sensors 42 of the four tanks 7 and the second pressure sensor 62 of the piping 11 is ON, i.e., when the pressure in any of the four tanks 7 and the piping 11 drops to the preliminary reference value, or when the ship is sailing in an area other than a general sea area (e.g., an area subject to emission control) (step S4), the engine 1 is switched from the first tuning state to the second tuning state (step S5). By repeating the above procedure, the fuel consumption of the engine 1 can be reduced while suppressing the occurrence of knocking of the engine 1.

[0038] The present invention is not limited to the above-described embodiment. Other embodiments of the present invention will be described below, but redundant description of the same points as those in the above-described embodiment will be omitted.

[0039] In the above embodiment, the first pressure sensor 41 and the second pressure sensor 42 are provided in each tank 7, but this is not limiting, and a pressure detection unit capable of continuously detecting a pressure in a range including the reference value and the preliminary reference value may be provided. Similarly, the pipe 11 may be provided with a pressure detection unit capable of detecting a pressure in a range including the reference value and the preliminary reference value.

[0040] In the above embodiment, the first tuning state and the second tuning state are switched by adjusting the set value (tuning state) of the air-fuel ratio supplied to the engine 1, but this is not limiting. For example, the first tuning state and the second tuning state may be switched by adjusting the rotation speed of the engine 1. Normally, the electrical equipment constituting the onboard loads is set to maximize its efficiency at a rated frequency (e.g., 60 Hz), so the engine 1 is kept constant at a rotation speed at which the frequency of the power (AC current) generated by the generator 2 is the rated frequency. However, in this case, the electrical equipment constituting the onboard loads is always operated at maximum efficiency, which may result in operation at excessive capacity in some cases.

[0041] Therefore, when there is a margin of capacity in the electrical equipment that constitutes the onboard load, slightly lowering the rotation speed of the engine 1 reduces the power supplied to all of the electrical equipment connected to the main bus 3 all at once, thereby achieving power saving. Specifically, the rotation speed of the engine 1 can be switched between a second tuning state in which the rotation speed corresponds to the rated frequency (for example, 60 Hz), and a first tuning state in which the rotation speed corresponds to a frequency lower than the rated frequency (for example, 57 Hz).

[0042] When the engine speed of engine 1 is reduced, the load on engine 1 increases in order to maintain the same output. Therefore, the tuning curve in the first tuning state, in which the engine speed is low, is positioned closer to the load side (upper side in FIG. 2), i.e., closer to the knocking region, than the tuning curve in the second tuning state, in which the engine speed is high. Therefore, if a sign of an increase in the load on engine 1 is detected while operating in the first tuning state, specifically if it is detected that either second pressure sensor 42 in tank 7 or second pressure sensor 62 in pipe 11 has dropped to a preliminary reference value, the engine speed is increased and the state is switched to the second tuning state. This reduces the load on engine 1 and moves the tuning curve away from the knocking region, thereby suppressing the occurrence of knocking.

[0043] In the above embodiment, the engine 1 is a dual fuel engine, but the present invention is not limited to this and may be, for example, a gas engine that uses only gas fuel. [Explanation of symbols]

[0044] 1 engine 2. Generator 3 Main busbar 4a-4e Electric motors (electrical equipment) 5 Compressor 6 Fans 7. Tank 8 Governor 10 Main engine 11 Piping 20 Control Unit 30 Turbocharger 31 Turbine 32 Compressor 41, 42 Pressure sensor (pressure detection part) 50 Supercharger 51 Turbine 52 Compressor 61, 62 Pressure sensor (pressure detection part)

Claims

1. A marine engine control device including a gas-fueled engine and a control unit for controlling the engine, the control unit is capable of switching between a first tuning state and a second tuning state in which fuel economy is worse than that of the first tuning state, A marine engine control device that switches to the second tuning state when a sign of an increase in load on the engine is detected while the engine is operating in the first tuning state.

2. a generator driven by the engine and a drive unit supplied with electric power generated by the generator, 2. The marine engine control device according to claim 1, wherein when a sign of starting of the drive unit is detected during operation in the first tuning state, the state is switched to the second tuning state.

3. a tank; and a pressure detection unit that detects the pressure inside the tank; the pressure detection unit is capable of detecting a reference value and a preliminary reference value higher than the reference value, 2. The marine engine control device according to claim 1, wherein the control unit switches from the first tuning state to the second tuning state when the pressure detection unit detects that the pressure in the tank has dropped to the preliminary reference value.

4. 2. The marine engine control device according to claim 1, wherein a set value of the air-fuel ratio of the mixture supplied to the engine in the first tuning state is lower than a set value of the air-fuel ratio of the mixture supplied to the engine in the second tuning state.

5. 2. The marine engine control device according to claim 1, wherein the engine speed in the first tuning state is lower than the engine speed in the second tuning state.

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