JP7129755B2 - marine diesel engine - Google Patents

Description

The present invention relates to marine diesel engines.

A marine diesel engine consists of an engine body and a turbocharger that rotates a turbine with the power of exhaust gas discharged from the engine body and supplies compressed air generated by a compressor that is coaxially connected to the turbine to the engine body. and an EGR unit that recirculates part of the exhaust gas discharged from the engine body to the engine body (see Patent Document 1). Further, Japanese Patent Laid-Open No. 2002-200002 describes control that delays the opening timing of an exhaust valve of an engine body so that part of the burned gas is not discharged from the exhaust valve.

JP 2014-20275 A

As described in Patent Document 1, the balance of air in the combustion chamber can be adjusted by adjusting the timing of opening the exhaust valve. Here, in a marine diesel engine, control can be performed to change the operation timing of the exhaust valve according to the load of the engine body or the like. Marine diesel engines can be operated efficiently under operating conditions by switching the timing of exhaust valve operation according to the load on the engine itself, but combustion becomes unstable and black smoke is generated. Dangerous engine body operating conditions may occur.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-described problems, and to provide a marine diesel engine capable of operating the engine body under better conditions.

To achieve the above object, the present invention provides a marine diesel engine comprising: an engine body for controlling the exhaust of air in a combustion chamber by opening and closing an exhaust valve; and a turbine rotated by the exhaust gas discharged from the engine body. and the turbine and the rotating shaft are connected, the turbocharger includes a compressor that rotates with the rotation of the turbine and generates compressed air, supplies the compressed air to the engine body, and the exhaust gas discharged from the engine body A portion of the EGR system recirculates as combustion gas to the engine body, and the timing of closing the exhaust valve in the combustion cycle is controlled as the engine body speed increases. An engine control device that controls the operation of the exhaust valve and an EGR control device that controls the drive of the EGR system based on the delayed exhaust valve closing timing pattern, wherein the exhaust valve closing timing pattern is the When the operating condition of the engine body is the threshold condition and the timing of closing the exhaust valve when the EGR system is operating is the threshold condition of the operating condition of the engine body and the EGR system is stopped earlier than the timing of closing the exhaust valve.

A marine diesel engine can suppress a decrease in the amount of oxygen relative to the amount of fuel supplied to the combustion chamber while the EGR system is in operation, and can stably burn the fuel. As a result, the engine body can be operated under better conditions. Even when the operating auxiliary compressor is stopped and the EGR system is operating, the amount of air held in the combustion chamber can be increased and the fuel can be stably burned. As a result, the engine body can be operated under better conditions.

Further, in the exhaust valve closing timing pattern, the timing of closing the exhaust valves when the EGR system is operating is earlier than the timing of closing the exhaust valves when the EGR system is stopped. preferable.

An auxiliary compressor for compressing air supplied to the engine body is provided, and the exhaust valve closing timing pattern closes the exhaust valve when the EGR system is operating and the auxiliary compressor is driven. Preferably the timing is constant.

It has an auxiliary compressor that compresses the air supplied to the engine body, and the exhaust valve closing timing pattern includes the timing of closing the exhaust valve when the EGR system is operating and the closing timing of the exhaust valve when the EGR system is stopped. It is preferable that the difference from the timing at which the exhaust valve is closed when the auxiliary compressor is operating is maximized under operating conditions in which the EGR system is operating and the auxiliary compressor is switched from being driven to being stopped.

When the operating condition of the engine body is a condition in which the load is lower than the threshold condition, the air supplied to the engine body is compressed, and when the operating condition of the engine body is a condition in which the load is higher than the threshold condition, Preferably, it also has an auxiliary compressor that shuts off. When the operating auxiliary compressor stops, it is possible to suppress the decrease in the amount of oxygen relative to the amount of fuel supplied to the combustion chamber. As a result, the engine body can be operated under better conditions.

The EGR system includes an exhaust gas recirculation line that recirculates part of the exhaust gas discharged from the engine body to the engine body as combustion gas, an EGR valve provided in the exhaust gas recirculation line, and the exhaust gas recirculation. and a scrubber for injecting a liquid against the combustion gas flowing through the line.

Preferably, the EGR system supplies recirculated exhaust gas to the compressor, which is axially connected to the turbine.

According to the present invention, it is possible to suppress a decrease in the amount of oxygen with respect to the amount of fuel supplied to the combustion chamber while the EGR system is in operation, and to stably burn the fuel. As a result, the engine body can be operated under better conditions.

FIG. 1 is a schematic diagram showing a diesel engine equipped with the EGR system of this embodiment. FIG. 2 is a schematic configuration diagram showing the EGR system of this embodiment. FIG. 3 is a schematic diagram showing a schematic configuration of the engine body of the present embodiment. FIG. 4 is a flowchart showing an example of control of the engine drive system. FIG. 5 is a graph showing the relationship between engine load and exhaust valve closing timing. FIG. 6 is a flowchart showing an example of control of the auxiliary compressor. FIG. 7 is a graph showing the relationship between the in-cylinder oxygen amount and the engine load. FIG. 8 is a graph showing another example of the relationship between engine load and exhaust valve closing timing. FIG. 9 is a graph showing the relationship between scavenging pressure and exhaust valve closing timing.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the present invention is not limited by this embodiment, and when there are a plurality of embodiments, the present invention includes a combination of each embodiment.

FIG. 1 is a schematic diagram showing a marine diesel engine equipped with an EGR system, and FIG. 2 is a schematic configuration diagram showing the EGR system.

As shown in FIG. 1 , a marine diesel engine 10 of this embodiment includes an engine body (engine) 11 , a supercharger 12 and an EGR system 13 .

As shown in FIG. 2, the engine body 11 is a propulsion engine (main engine) that drives and rotates a propulsion propeller via a propeller shaft, although not shown. The engine body 11 is a uniflow sweep-exhaust type crosshead diesel engine, which is a two-stroke diesel engine. It is the one that was made. The engine body 11 includes a plurality of cylinders 21 in which pistons move up and down, a scavenging trunk 22 communicating with each cylinder 21 , and an exhaust manifold 23 communicating with each cylinder 21 . A scavenging port 24 is provided between each cylinder 21 and a scavenging trunk 22 , and an exhaust passage 25 is provided between each cylinder 21 and an exhaust manifold 23 . In the engine body 11, a scavenging trunk 22 is connected to an air supply line G1, and an exhaust manifold 23 is connected to an exhaust line G2.

FIG. 3 is a schematic diagram showing a schematic configuration of the engine body of the present embodiment. FIG. 3 shows a portion of the engine body 11 corresponding to one piston and cylinder 21 . The engine body 11 has a base plate 111 positioned below, a frame 112 provided on the base plate 111 , and a cylinder jacket 113 provided on the frame 112 . The base plate 111, frame 112, and cylinder jacket 113 are integrally fastened and fixed by a plurality of vertically extending tension bolts (tie bolts/connecting members) 114 and nuts 115. As shown in FIG.

A cylinder liner 116 is provided in the cylinder jacket 113 , and a cylinder cover 117 is provided on the upper end of the cylinder liner 116 . The cylinder liner 116 and the cylinder cover 117 define a space 118 , and a piston 119 is provided in the space 118 so as to reciprocate vertically, thereby forming a combustion chamber 120 . Further, the cylinder cover 117 is provided with an exhaust valve (exhaust gas valve) 121 . The exhaust valve 121 opens and closes the combustion chamber 120 and the exhaust pipe 122 . It should be noted that the exhaust valve 121 only needs to have the function of opening and closing the combustion chamber 120 and the exhaust gas pipe 122 and does not necessarily have to be provided in the central portion of the cylinder cover 117 .

Therefore, the fuel supplied from the fuel injection pump and the combustion gas compressed by the supercharger 12 are supplied to the combustion chamber 120 and combusted. The energy generated by this combustion causes the piston 119 to move up and down. Further, at this time, when the combustion chamber 120 is opened by the exhaust valve 121 , the exhaust gas generated by combustion is pushed out to the exhaust gas pipe 122 while the combustion gas is introduced into the combustion chamber 120 from the scavenging port 24 . The exhaust gas pipe 122 is connected to the exhaust manifold 23 .

The piston 119 is connected to the upper end portion of the piston rod 123 and is coupled together with the piston rod 123 so as to be movable in the piston axial direction. The base plate 111 is used as a crankcase, and is provided with bearings 125 that rotatably support the crankshaft 124 . The lower end of a connecting rod 127 is rotatably connected to the crankshaft 124 via a crank 126 . A pair of vertically extending guide plates 128 are fixed to the frame 112 at a predetermined interval, and a crosshead 129 is vertically movably supported between the pair of guide plates 128 . The crosshead 129 is rotatably connected to a crosshead bearing that connects the lower half of a crosshead pin provided at the lower end of the piston rod 123 to the upper end of the connecting rod 127 .

Therefore, the piston 119, to which the energy generated in the combustion chamber of the cylinder jacket 113 is transmitted, moves toward the installation surface of the engine body 11 together with the piston rod 123 (in the direction toward the base plate 111, that is, downward in the axial direction of the piston). down to Then, the piston rod 123 pushes down the crosshead 129 in the axial direction of the piston and rotates the crankshaft 124 via the connecting rod 127 and the crank 126 .

The engine body 11 is provided with a rotation speed detection section 62 , a fuel input amount detection section 64 , and a scavenging pressure detection section 65 . The rotation speed detection unit 62 detects the rotation speed of the engine body 11 (the rotation speed of the rotating shaft connected to the propeller shaft). The rotation speed detection unit 62 may detect the rotation speed of the rotating shaft inserted into the engine body 11, or may detect the rotation speed of the propeller shaft. The fuel input amount detection unit 64 detects the fuel input amount of the engine body 11 . The scavenging pressure detector 65 detects the pressure of the compressed air supplied to the engine body 11 . Specifically, the scavenging pressure detection unit 65 is arranged in the scavenging trunk 22 and detects the pressure in the scavenging trunk 22 .

The engine control device 26 controls the operation of the engine body 11 . The engine control device 26 operates the engine main body 11 based on various input conditions such as the required load and results detected by various sensors such as the rotation speed detection unit 62, the fuel input amount detection unit 64, and the scavenging pressure detection unit 65. to control. The engine control device 26 controls the injection timing and injection amount of fuel to the cylinder 21, and the opening/closing timing of the exhaust valve 121, thereby controlling the fuel input amount and rotation speed of the engine body 11 and combustion in the combustion chamber 120. . The engine control device 26 controls the output of the engine body 11 by controlling the amount of fuel supplied and the rotation speed.

The supercharger 12 is configured by connecting a compressor (compressor) 31 and a turbine 32 by a rotating shaft 33 so as to rotate integrally. In the supercharger 12, the turbine 32 is rotated by the exhaust gas discharged from the exhaust line G2 of the engine body 11, and the rotation of the turbine 32 is transmitted by the rotary shaft 33 to rotate the compressor 31. At least one of the recirculated gases is compressed and supplied to the engine main body 11 from the air supply line G1 as a compressed compressed gas. The compressor 31 is connected to a suction line G6 that draws in air from the outside (atmosphere).

The supercharger 12 is connected to an exhaust line G3 for discharging exhaust gas that has rotated the turbine 32. The exhaust line G3 is connected to a not-shown chimney (funnel). An EGR system 13 is provided between the exhaust line G3 and the air supply line G1.

The EGR system 13 includes exhaust gas recirculation lines G4, G5, G7, a scrubber 42, a demister unit 14, an EGR blower 47, and an EGR controller 60. The EGR system 13 mixes part of the exhaust gas discharged from the engine body 11 with air as a recirculated gas, compresses it by the supercharger 12, and recirculates it as a combustion gas to the marine diesel engine 10. , to suppress the generation of NOx due to combustion. Although part of the exhaust gas is extracted from the downstream side of the turbine 32 here, part of the exhaust gas may be extracted from the upstream side of the turbine 32 .

In the following description, the term "exhaust gas" refers to gas discharged from the engine body 11 to the exhaust line G2 and then to the outside through the exhaust line G3. Recirculated gas refers to a portion of the exhaust gas separated from the exhaust line G3. The recirculated gas is returned to the engine body 11 through exhaust gas recirculation lines G4, G5 and G7.

One end of the exhaust gas recirculation line G4 is connected to an intermediate portion of the exhaust line G3. The exhaust gas recirculation line G4 is provided with an EGR inlet valve (on-off valve) 41A and is connected to the scrubber 42 at the other end. The EGR inlet valve 41A opens and closes the exhaust gas recirculation line G4 to turn ON/OFF the exhaust gas diverted from the exhaust line G3 to the exhaust gas recirculation line G4. Alternatively, the EGR inlet valve 41A may be used as a flow control valve to adjust the flow rate of the exhaust gas passing through the exhaust gas recirculation line G4.

The scrubber 42 is a venturi-type scrubber, and includes a hollow throat portion 43, a venturi portion 44 into which the exhaust gas is introduced, and an enlarged portion 45 for gradually returning to the original flow velocity. The scrubber 42 includes a water injection section 46 that injects water against the recirculated gas introduced into the venturi section 44 . The scrubber 42 is connected to an exhaust gas recirculation line G5 for discharging recirculated gas from which harmful substances such as particulate matter (PM) such as SOx and particulate matter (PM) are removed and waste water containing harmful substances. In this embodiment, the scrubber 42 is of a venturi type, but is not limited to this configuration.

A demister unit 14 and an EGR blower 47 are provided in the exhaust gas recirculation line G5.

The demister unit 14 separates the recycled gas from which harmful substances have been removed by water injection and waste water. The demister unit 14 is provided with a waste water circulation line W<b>1 for circulating waste water to the water injection part 46 of the scrubber 42 . A hold tank 49 for temporarily storing mist (waste water) and a pump 50 are provided in the waste water circulation line W1.

The EGR blower 47 guides the recirculated gas inside the scrubber 42 to the demister unit 14 from the exhaust gas recirculation line G5. The EGR blower 47 sends the recirculated gas that has passed through the demister unit 14 to the compressor 31 .

One end of the exhaust gas recirculation line G7 is connected to the EGR blower 47, and the other end is connected to the compressor 31 via a mixer (not shown). be done. The exhaust gas recirculation line G7 is provided with an EGR outlet valve (on-off valve or flow control valve) 41B. The air from the intake line G6 and the recirculated gas from the exhaust gas recirculation line G7 are mixed in a mixer to generate combustion gas. The mixer may be provided separately from the silencer, or the silencer may be configured to add a function of mixing the recirculated gas and air without providing a separate mixer. The supercharger 12 can supply the combustion gas compressed by the compressor 31 to the engine body 11 through the air supply line G1, and an air cooler 48 is provided in the air supply line G1. The air cooler 48 cools the combustion gas by exchanging heat between the combustion gas compressed by the compressor 31 and having a high temperature and cooling water. Further, the EGR system 13 has an oxygen concentration detector 66 arranged in the air supply line G<b>1 or the scavenging trunk 22 . The oxygen concentration detector 66 of this embodiment is arranged closer to the engine body 11 than the air cooler 48 is. The oxygen concentration detector 66 detects the oxygen concentration of the air supplied to the engine body 11, that is, the oxygen concentration of the combustion gas when the EGR system 13 is in operation.

The EGR control device 60 controls operations of each part of the EGR system 13 . The EGR control device 60 acquires load information from the engine control device 26 . The EGR control device 60 acquires information on the fuel input amount of the engine body 11 from the fuel input amount detection section 64 . The EGR control device 60 acquires information on the oxygen concentration of the combustion gas supplied to the engine body 11 from the oxygen concentration detector 66 . The EGR control device 60 determines the operating state of the EGR blower 47, specifically the EGR blower 47 By controlling the frequency of the motor that rotates the impeller, the amount of recirculated gas supplied from the EGR system 13 to the engine body 11 is controlled. The EGR control device 60 stores the relationship between the load of the engine body 11 and the target value of the oxygen concentration, and calculates the target value of the oxygen concentration according to the load. The EGR control device 60 calculates a target value of oxygen concentration based on the relationship between the load of the engine body 11 and the target value of oxygen concentration, and compares the relationship between the calculated target value of oxygen concentration and the acquired oxygen concentration with the current The frequency (operating frequency) of the EGR blower 47 is calculated based on the frequency of the EGR blower 47 of . The EGR control device 60 rotates the EGR blower 47 at the calculated frequency of the EGR blower 47 . The EGR control device 60 also controls each part other than the EGR blower 47 , such as the opening and closing of the EGR inlet valve 41 A and the EGR outlet valve 41 B, and the operation of the scrubber 42 .

The operation of the EGR system 13 of this embodiment will be described below. As shown in FIG. 2, in the engine body 11, when combustion gas is supplied from the scavenging trunk 22 into the cylinder 21, the combustion gas is compressed by the piston 119, and fuel is supplied to the high-temperature combustion gas. is spontaneously ignited and burned. The generated combustion gas is discharged as exhaust gas from the exhaust manifold 23 to the exhaust line G2. Exhaust gas discharged from the engine body 11 rotates the turbine 32 in the supercharger 12 and is then discharged to the exhaust line G3. It is discharged outside from G3.

On the other hand, when the EGR inlet valve 41A and the EGR outlet valve 41B are open, part of the exhaust gas flows as recirculated gas from the exhaust line G3 to the exhaust gas recirculation line G4. The scrubber 42 removes harmful substances from the recirculated gas that has flowed through the exhaust gas recirculation line G4. That is, when the recirculated gas passes through the venturi section 44 at a high speed, the scrubber 42 injects water from the water injection section 46 to cool the recirculated gas and drop harmful substances together with the water. to remove. Mist (wastewater) containing harmful substances then flows into the demister unit 14 together with the recirculated gas.

The recirculated gas from which harmful substances have been removed by the scrubber 42 is discharged to the exhaust gas recirculation line G5, and after mist (waste water) is separated by the demister unit 14, is sent to the turbocharger 12 through the exhaust gas recirculation line G7. . The recirculated gas is mixed with the air taken in from the intake line G6 to become combustion gas, compressed by the compressor 31 of the turbocharger 12, cooled by the air cooler 48, and supplied to the engine from the air supply line G1. It is supplied to the main body 11 .

The auxiliary compressor 51 is arranged between the air cooler 48 and the scavenging trunk 22 on the air supply line G1. The auxiliary compressor (auxiliary blower) 51 has a bypass line 52 , a blower impeller (compressor) 54 , a blower electric motor (motor) 56 , and a check valve 59 . The auxiliary compressor 51 is controlled based on the pressure in the scavenging trunk 22 detected by the scavenging pressure detector 65 . The bypass line 52 has both ends connected to the air supply line G1 and bypasses the air supply line G1. The blower impeller 54 is provided in the scavenging line G<b>1 and compresses the air flowing through the bypass line 52 . A blower electric motor (motor) 56 rotates a blower impeller 54 . The check valve 59 is provided in the scavenging line G1 to prevent reverse flow of air in the bypass line 52, that is, air from flowing from the end on the scavenging trunk 22 side to the end on the air cooler 48 side.

The auxiliary compressor 51 is driven when the marine diesel engine 10 is started, and after compressing gas such as air taken in from the intake line G6 via the compressor 31, the compressed gas such as air is converted into combustion gas. is pumped to the scavenging trunk 22 side. The auxiliary compressor 51 may be provided with a control valve in the air supply line G1 and the bypass line 52, and the path through which the compressed air flows may be switched by opening and closing the control valve, or the flow rate balance may be controlled. The auxiliary compressor 51 is provided with the bypass line 52 that bypasses the air supply line G1, and the blower impeller 54 is provided in this bypass line 52, but the air supply line G1 and the bypass line 52 need not be provided in parallel. Alternatively, without providing the bypass line 52, only the air supply line G1 may be provided, and the blower impeller 54 may be provided in the air supply line G1.

Next, control of the engine main body 11 and the auxiliary compressor 51 executed by the engine control device 26 of the marine diesel engine 10 will be described with reference to FIG. FIG. 4 is a flowchart showing an example of control of the engine drive system.

The engine control device 26 switches the control conditions of each section between a setting for operating the EGR system 13 and a setting for not operating the EGR system 13, that is, a setting for stopping the EGR system 13 . The setting in which the EGR system 13 is not operated is a state in which recirculation is not performed to supply part of the exhaust gas purified from the EGR system 13 to the engine body 11, and a part of the EGR system 13 such as the scrubber 42 of the EGR system 13 may be in operation.

The engine control device 26 executes control in the EGR mode when the EGR system 13 is set to operate, and executes control in the normal mode when the EGR system 13 is not operated. Description will be made below with reference to FIG. The engine control device 26 determines whether it is set to operate the EGR system 13 (step S12). The setting for operating the EGR system 13 is whether the switch is ON or OFF, if there is a switch for turning the EGR system 13 ON or OFF by the user. In addition, in the case of setting to operate the EGR system 13, the EGR system 13 does not have to be actually operated. For example, in the marine diesel engine 10, when the EGR system 13 is set to operate when the load of the engine body 11 is equal to or higher than the threshold value, even if the EGR system 13 is set to operate, if the load of the engine body 11 is low, the EGR system 13 Not working.

When determining that the EGR system 13 is set to operate (Yes in step S12), the engine control device 26 selects the EGR mode (step S14) and controls each section based on the EGR mode setting. When determining that the EGR system 13 is not set to operate (No in step S12), the engine control device 26 selects the normal mode (step S16) and controls each part based on the normal mode setting.

Next, control of the exhaust valves by the engine control device 26 will be described with reference to FIG. FIG. 5 is a graph showing the relationship between engine load and exhaust valve closing timing. The engine control device 26 changes the exhaust valve closing timing according to the engine load based on the exhaust valve closing timing pattern, which is the relationship between the engine load and the exhaust valve closing timing shown in FIG. The exhaust valve closing timing is the timing at which the exhaust valve closes in the combustion cycle, and can be indicated by the angle of the combustion cycle. Here, the timing at which the exhaust valve 121 is closed is controlled based on the angle where one stroke of the piston 119 of the engine body 11 is 360 degrees, that is, the crank angle, as described above. That is, the engine control device 26 opens the exhaust valve 121 when the crank angle reaches the set angle. When the closing timing of the exhaust valve 121 is delayed, the exhaust valve is closed at a larger crank angle.

An exhaust valve closing timing pattern 202 indicated by a solid line in FIG. 5 indicates the relationship between the engine load and the exhaust valve closing timing in the EGR mode. An exhaust valve closing timing pattern 204 indicated by a dotted line in FIG. 5 indicates the relationship between the engine load and the exhaust valve closing timing in the normal mode. Both of the exhaust valve closing timing patterns 202 and 204 of the present embodiment have a relationship in which the exhaust valve closing timing is retarded as the engine load increases. In the case of the EGR mode in which the EGR system 13 is set to operate, the engine control device 26 detects the engine load, and closes the exhaust valve 121 based on the relationship between the detected engine load and the exhaust valve closing timing pattern 202. Controls certain exhaust valve closing timing. The engine control device 26 detects the engine load in the normal mode, which is set to not operate the EGR system 13, and the timing of closing the exhaust valve based on the relationship between the detected engine load and the exhaust valve closing timing pattern 204. Controls the exhaust valve closing timing.

In the normal mode exhaust valve closing timing pattern 204, the rate of change, which is the amount of change in the exhaust valve closing timing with respect to the amount of change in the engine load, is constant. Although the rate of change is constant in FIG. 5, the rate of change may be changed as long as the exhaust valve closing timing is delayed as the load increases. Here, the exhaust valve closing timing pattern 204 is a setting in which the exhaust gas purified from the EGR system 13 is not supplied. It is the relationship between the engine load and the exhaust valve closing timing, which is the ideal line set by Here, the ideal line first determines the maximum combustion pressure from the design output of the engine. From this, the pressure during combustion of each load is determined, the compression pressure is designed from the pressure during combustion, and the planned closing timing of the exhaust valve is determined so as to achieve the compression pressure. After that, the exhaust valve closing timing is determined so that parameters such as the fuel efficiency and the exhaust gas outlet temperature are optimized by changing and adjusting around the planned exhaust valve closing timing through a test run. The exhaust valve closing timing described above is performed for each load, and the optimal exhaust valve closing timing angle is determined for each load. At this time, the exhaust valve closing timing pattern 204 is determined by performing fine adjustments so that the timings of the loads are smoothly connected.

The exhaust valve closing timing pattern 202 in the EGR mode has an earlier exhaust valve closing timing than the exhaust valve closing timing pattern 204 at the same engine load. The exhaust valve closing timing pattern 202 is set based on the result of calculating the exhaust valve closing timing at which the engine performance such as fuel consumption increases at each engine load, in a setting where exhaust gas purified from the EGR system 13 is supplied. This relationship is set based on the relationship between the engine load and the exhaust valve closing timing, which is an ideal line. For example, in the exhaust valve closing timing pattern 202, the exhaust valve closing timing is constant in the load range 210 in which the auxiliary compressor 51 is operating, that is, in the engine load range lower _than the engine load _A1 . In the high engine load range, the higher the engine load, the later the exhaust valve closing timing. Here, the engine load A1 is the load when the operating condition of the engine body ₁₁ reaches the threshold condition. Various conditions can be set as the threshold conditions. In the exhaust valve closing timing pattern 202 of FIG. 5, the rate of change is constant in the range of the engine load higher _than the engine load A1, but the rate of change may vary. Thus, in the exhaust valve closing timing pattern 202, even if the engine load increases in the load range 210, the exhaust valve closing timing is not delayed. As a result, in the load range 210, the difference between the exhaust valve closing timing pattern 202 and the exhaust valve closing timing pattern 204 increases as the engine load increases.

The engine control device 26 controls the exhaust valve closing timing based on the exhaust valve closing timing pattern 202 in the EGR mode, and controls the exhaust valve closing timing based on the exhaust valve closing timing pattern 204 in the normal mode. . As a result, the engine control device 26 causes the exhaust valve closing timing in the EGR mode to be earlier _than the exhaust valve closing timing in the normal mode under the same load condition, for example, engine load A1 of the threshold condition. Thus, in the case of the EGR mode, by making the exhaust valve closing timing earlier than in the normal mode, the engine body 11 can be operated more stably than in the case where all the controls are performed under the conditions of the normal mode. can.

Specifically, by operating the EGR system 13, the marine diesel engine 10 can reduce the oxygen concentration of the combustion gas, slow the combustion, increase the heat capacity of the combustion gas, and increase the temperature. can be suppressed, and furthermore, the amount of exhaust gas discharged from the marine diesel engine 10 to the outside of the system can be reduced. As a result, the marine diesel engine 10 operates the EGR system 13 to reduce the amount of nitrogen oxide emissions. However, if the marine diesel engine 10 is operated under conditions that slow down combustion, the amount of oxygen in the cylinder will decrease significantly, and the operation may become unstable. In the EGR mode, the engine control device 26 makes the exhaust valve closing timing earlier than in the normal mode, thereby reducing the decrease in the amount of oxygen in the combustion chamber 120 with respect to the decrease in the oxygen concentration of the combustion gas. can. As a result, the engine body 11 can be operated more stably.

The engine control device 26 also sets an exhaust valve closing timing pattern 202 for the EGR mode and an exhaust valve closing timing pattern 204 for the normal mode. By controlling the exhaust valve closing timing according to each mode depending on whether the EGR operation is performed or not, it is possible to stably operate the engine in each mode and improve the operation efficiency.

In addition, the engine control device 26 can simplify the parameter setting by making constant the closing timing of the exhaust valve 121 in the load range 210 of the exhaust valve closing timing pattern 202 in the EGR mode, thereby simplifying the control. can be Since the control can be simplified, the operation of the engine body 11 can be stabilized.

Here, the engine load A1 of the threshold condition is preferably in the range of ₂₀ % or more and 60% or less. Note that the engine load is assumed to be 100% of the rated load. Further, the engine control device 26 of the present embodiment operates under better conditions than the engine body 11 by making the exhaust valve closing timing in the EGR mode earlier than the exhaust valve closing timing in the normal mode at any engine load. can be, but is not limited to. Also, when the engine load is outside the above range, the engine control device 26 preferably makes the exhaust valve closing timing in the EGR mode earlier than the exhaust valve closing timing in the normal mode when compared with the same engine load . That is, it is preferable that the exhaust valve closing timing in the EGR mode is the same as or earlier than the exhaust valve closing timing in the normal mode when compared with the same engine load . As a result, the engine can be operated under better conditions than the main body 11 of the engine. Further, in the above embodiment, the engine load is explained, but it is preferable that the rotation speed of the engine main body 11 is also set in the same range as a ratio to the rotation speed of the rated operation.

Next, the auxiliary compressor 51 controls stoppage of operation based on the pressure detected by the scavenging pressure detector 65 . A description will be given below with reference to FIG. FIG. 6 is a flowchart showing an example of control of the auxiliary compressor. The processing shown in FIG. 6 may be executed only when the engine body 11 is started, or may be executed all the time. The auxiliary compressor 51 determines whether the pressure in the scavenging trunk 22 is below the threshold (step S22). When it is determined that the pressure in the scavenging trunk 22 is equal to or lower than the threshold (Yes in step S22), the auxiliary compressor 51 operates (step S24). That is, the blower motor 56 of the auxiliary compressor 51 is driven, and the blower impeller 54 is driven. When it is determined that the pressure in the scavenging trunk 22 is not equal to or lower than the threshold value (No in step S22), the auxiliary compressor 51 stops the auxiliary compressor 51 (step S26). That is, the blower motor 56 of the auxiliary compressor 51 is stopped, and the blower impeller 54 is stopped. As a result, since the engine load of the auxiliary compressor 51 is low, the pressure of the air compressed by the turbocharger 12 is low, and when the pressure detected by the scavenging pressure detection unit 65 is low, the auxiliary compressor 51 Compressed air can be supplied to the engine body 11 . Thereby, the pressure of the compressed air supplied to the engine main body 11 can be increased.

In this embodiment, the operation and stop of the auxiliary compressor 51 are controlled based on the scavenging pressure detected by the scavenging pressure detector 65, but the operation and stop of the auxiliary compressor 51 are controlled based on the engine load. may

Preferably, the engine control device 26 sets the above-described engine load A1 as _a condition for stopping the auxiliary compressor 51 . In other words, it is preferable to set the threshold condition as a condition for stopping the auxiliary compressor 51 that has been in operation. As a result, the auxiliary compressor 51 is operated when the operating condition of the engine body 11 is lower _than the engine load A1 of the threshold condition. Further, the auxiliary compressor 51 compresses the combustion gas supplied to the engine main body, and is stopped when the operating condition of the engine main body 11 is higher _than the engine load A1, which is the threshold condition. Since the auxiliary compressor 51 may be controlled without using the engine load, there may be a tolerance difference between the threshold condition and the condition for stopping the auxiliary compressor 51 .

_The engine control device 26 controls the exhaust valve closing timing based on the exhaust valve closing timing pattern 202 in the EGR mode, so that the exhaust valve closing timing at the engine load A1 at which the auxiliary compressor 51 is stopped is normal mode. than when operating with the exhaust valve closing timing pattern 204 of . In this way, by advancing the closing timing of the exhaust valve at the engine load A1, the amount of oxygen in the cylinder (the amount of oxygen in the combustion chamber ₁₂₀ ) decreases at the timing when the auxiliary compressor 51 is stopped, and black smoke is emitted. It is possible to prevent the in-cylinder oxygen amount from decreasing to a level that is likely to occur.

FIG. 7 is a graph showing the relationship between the in-cylinder oxygen amount and the engine load. In FIG. 7, the horizontal axis is the engine load, and the vertical axis is the in-cylinder oxygen amount. That is, FIG. 7 shows the relationship between the engine load and the in-cylinder oxygen amount at that load. In FIG. 7, EGR OFF indicates the case where the exhaust valve closing timing is controlled based on the exhaust valve closing timing pattern 204 in the normal mode, and in the EGR mode and based on the exhaust valve closing timing pattern 204, the exhaust valve A case where the closing timing is controlled is indicated by EGR ON (comparative example), and a case where the exhaust valve closing timing is controlled based on the exhaust valve closing timing pattern 202 in the EGR mode is indicated by EGR ON (example).

As shown in FIG. 7, the engine control device 26 executes control according to the exhaust valve closing timing pattern 202 of the present embodiment, so that the auxiliary compressor is It is possible to prevent the in-cylinder oxygen amount from decreasing to the smoke generation level 212 under the condition that 51 is stopped.

In this manner, the engine control device 26 executes control according to the exhaust valve closing timing pattern 202 of the present embodiment, thereby reducing the load (rotational speed) of the engine body 11 while the auxiliary compressor 51 is operating. It is possible to suppress a decrease in the excess oxygen ratio during fuel combustion in the combustion chamber 120 that is proportional to the increase. By suppressing the decrease in the amount of oxygen with respect to the injected fuel, it is possible to increase the amount of air in the combustion chamber 120 under the same load as compared with the case of operating with the exhaust valve closing timing pattern 204 . This makes it possible to increase the amount of oxygen in the combustion chamber 120 when the auxiliary compressor 51 is stopped even when operating in the EGR mode.

The engine control device 26 prevents the amount of air held in the combustion chamber 120 from decreasing even if the load increases in the load range 210, so that the amount of oxygen in the combustion chamber 120 when the auxiliary compressor 51 is stopped is reduced. The amount can be increased, and the fuel can be combusted favorably. As a result, it is possible to prevent the combustion from becoming unstable due to less oxygen in the fuel when the auxiliary compressor 51 is stopped, and to prevent the generation of black smoke due to incomplete combustion. In addition, since the combustion can be stably executed, the desired output can be obtained, and the rotation speed can be preferably increased. In the marine diesel engine 10 of the present embodiment, by operating the EGR system 13, the oxygen concentration of the combustion gas supplied to the combustion chamber 120 becomes low, and the risk of unstable combustion and generation of black smoke increases. By controlling the exhaust valve closing timing based on the exhaust valve closing timing pattern 202, it is possible to suppress the combustion from becoming unstable and suppress the generation of black smoke due to incomplete combustion. In addition, since combustion can be stably executed, a desired output can be obtained, and the rotation speed can be preferably increased or stabilized.

Further, the exhaust valve closing timing pattern 202 is a pattern that matches the exhaust valve closing timing pattern calculated so as to be the ideal line of the EGR mode in a range other than the exhaust valve closing timing at the stage of stopping the auxiliary compressor 51. preferably. As a result, the engine main body 11 can be operated more efficiently within the load range other than the stage in which the auxiliary compressor 51 is stopped. If the exhaust valve closing timing changes rapidly, the control of the engine body ₁₁ becomes unstable. It is preferred that the rate of change is close to zero. As a result, when the load of the engine body 11 increases or decreases in the vicinity of the stage where the auxiliary compressor 51 is stopped, fluctuations in the exhaust valve closing timing become too large, and the operation of the engine body 11 can be suppressed from becoming unstable. .

Moreover, it is preferable that the difference between the exhaust valve closing timing pattern 202 and the exhaust valve closing timing pattern 204 is maximized at the timing when the auxiliary compressor 51 is stopped. That is, the difference between the timing of closing the exhaust valve when the EGR system is operating and the timing of closing the exhaust valve when the EGR system is stopped is the difference between the timing when the EGR system is operating and the auxiliary compressor is driven. It is preferable that the engine load is maximized at engine load _A1 in FIG. As a result, the difference from the exhaust valve closing timing pattern 204 can be reduced in the engine load when the auxiliary compressor 51 is in operation and in the load range where the influence of the EGR system 13 is small, and the engine performance is high. You can drive in any condition. Further, the exhaust valve closing timing pattern 202 maximizes the difference in exhaust valve closing timing from the exhaust valve closing timing pattern 204 at the timing when the auxiliary compressor 51 is stopped, so that after the auxiliary compressor 51 is stopped, The amount of _O2 in the cylinder can be changed according to the state of EGR operation, and the engine can be operated in a state where the engine performance is improved.

Here, the exhaust valve closing timing pattern 202 has constant exhaust valve closing timing in the load range 210, but the present invention is not limited to this. FIG. 8 is a graph showing another example of the relationship between engine load and exhaust valve closing timing. Another example of the exhaust valve closing timing pattern will be described below with reference to FIG. Exhaust valve closing timing patterns 206, 208, and 209 shown in FIG. 8 are all EGR mode exhaust valve closing timing patterns.

In the exhaust valve closing timing pattern 206, when the engine load is low in the load range 210, the exhaust valve closing timing is delayed as the engine load increases. Even if it increases, the exhaust valve closing timing _remains constant, and even if the engine load exceeds A1, the exhaust valve closing timing remains constant until the engine load overlaps with the ideal line of the EGR mode. In this way, the engine control device 26 may have a relationship in which the exhaust valve closing timing is retarded as the engine load increases in the load range 210 .

_In the exhaust valve closing timing pattern 208, in the load range 210, as the engine load increases, the exhaust valve closing timing becomes later. constant. Note that the change rate of the load range 210 is smaller than the exhaust valve closing timing pattern 204 . In this way, the engine control device 26 delays the exhaust valve closing timing as the engine load increases in the load range 210, and the exhaust valve closing timing is delayed until the engine load exceeds the engine load _A1 and overlaps the ideal line in the EGR mode. The relationship may be such that the closing timing is constant.

The exhaust valve closing timing pattern 209 does not overlap with the exhaust valve closing timing pattern 204 when the engine load is in the load range 210 . In the exhaust valve closing timing pattern 209, the exhaust valve closing timing is earlier than in the exhaust valve closing timing pattern 204 even at the position where the engine load is the lowest. As a result, in the load range 210, the in-cylinder oxygen amount of the engine body 11 in the EGR mode can be increased.

The engine control device 26 can set various exhaust valve closing timing patterns in the EGR mode, such as exhaust valve closing timing patterns 206 , 208 , and 209 . The engine control device 26 sets the exhaust valve closing timing pattern in the EGR mode so that the exhaust valve closing timing at the engine load A1 is earlier _than the exhaust valve closing timing in the exhaust valve closing timing pattern 204 in the normal mode. effect can be obtained.

The engine control device 26 sets the exhaust valve closing timing patterns when the load on the engine body 11 increases, when the load on the engine body 11 decreases, and when the load on the engine body 11 decreases, the rotation speed of the engine body ₁₁ at engine load A1, and the exhaust valve closing timing pattern. A relationship different from the timing of closing 121 may be used.

Also, in the above embodiment, the exhaust valve closing timing is controlled based on the engine load, but the present invention is not limited to this. The engine control device 26 may control the exhaust valve closing timing based on the scavenging pressure of the engine body 11 . FIG. 9 is a graph showing the relationship between scavenging pressure and exhaust valve closing timing. An exhaust valve closing timing pattern 222 indicated by a solid line in FIG. 9 indicates the relationship between the scavenging pressure of the engine body 11 and the exhaust valve closing timing in the EGR mode. An exhaust valve closing timing pattern 224 indicated by a dotted line in FIG. 9 indicates the relationship between the scavenging pressure of the engine body 11 and the exhaust valve closing timing in the normal mode. Both of the exhaust valve closing timing patterns 222 and 224 of the present embodiment have a relationship in which the exhaust valve closing timing is retarded when the scavenging pressure of the engine body 11 increases. The engine control device 26 detects the scavenging pressure of the engine body 11 in the case of the EGR mode, which is the setting in which the EGR system 13 operates, and based on the relationship between the detected scavenging pressure of the engine body 11 and the exhaust valve closing timing pattern 222 control the exhaust valve closing timing, which is the timing at which the exhaust valve 121 is closed. The engine control device 26 detects the scavenging pressure of the engine body 11 in the normal mode, which is a setting that does not operate the EGR system 13, and based on the relationship between the detected scavenging pressure of the engine body 11 and the exhaust valve closing timing pattern 224. control the exhaust valve closing timing, which is the timing at which the exhaust valve 121 is closed.

In the normal mode exhaust valve closing timing pattern 224, the rate of change, which is the amount of change in the exhaust valve closing timing with respect to the amount of change in the scavenging pressure of the engine body 11, is constant. Although the rate of change is constant in FIG. 9, the rate of change may be changed as long as the opening timing of the exhaust valve is delayed as the scavenging pressure rises. Here, the exhaust valve closing timing pattern 224 is a setting in which exhaust gas purified from the EGR system 13 is not supplied, and the scavenging pressure of each engine main body 11 calculates the exhaust valve closing timing at which the engine performance such as fuel consumption increases. The relationship between the scavenging pressure of the engine body 11 and the exhaust valve closing timing is an ideal line set based on the result. The method of calculating the ideal line is as described above.

The exhaust valve closing timing pattern 222 in the EGR mode has an earlier exhaust valve closing timing than the exhaust valve closing timing pattern 224 when the scavenging pressure of the engine body 11 is the same. The exhaust valve closing timing pattern 222 is a setting in which the exhaust gas purified from the EGR system 13 is supplied, and the exhaust valve closing timing at which engine performance such as fuel efficiency is improved is calculated by the scavenging pressure of each engine body 11, and the result is This relationship is set based on the relationship between the scavenging pressure of the engine body 11 and the exhaust valve closing timing, which is an ideal line set based on. Specifically, the exhaust valve closing timing pattern 222 corresponds to the load range 210 in which the auxiliary compressor 51 is operating, that is, the pressure of the engine main body 11 lower than the scavenging pressure _B1 of the engine main body 11 at which the auxiliary compressor 51 stops. In the scavenging pressure range, the exhaust valve closing timing is constant, and in the range of the scavenging pressure of the engine body 11 higher than the scavenging pressure _B1 of the engine body 11, the exhaust valve closes as the scavenging pressure of the engine body 11 increases. Timing slows down. Note that the exhaust valve closing timing pattern ₂₂₂ in FIG. The rate of change may be changed as long as the opening timing is delayed. Thus, in the exhaust valve closing timing pattern 222, even if the scavenging pressure of the engine body 11 increases in the load range 210, the exhaust valve closing timing is not delayed. As a result, in the load range 210, the difference between the exhaust valve closing timing pattern 222 and the exhaust valve closing timing pattern 224 increases as the scavenging pressure of the engine body 11 increases.

_The engine control device 26 controls the exhaust valve closing timing based on the exhaust valve closing timing pattern 222 in the EGR mode. is earlier than when operating with the exhaust valve closing timing pattern 224 in the normal mode. In this way, by advancing the closing timing of the exhaust valve at the scavenging pressure _B1 of the engine main body 11, the amount of oxygen in the cylinder (the amount of oxygen in the combustion chamber 120) that occurs when the auxiliary compressor 51 is stopped can be reduced. Therefore, it is possible to prevent the in-cylinder oxygen amount from decreasing to the smoke generation level, which is the in-cylinder oxygen amount at which black smoke may be generated. Thus, even if the engine control device 26 performs control based on the scavenging pressure of the engine main body 11 instead of the engine load, it is possible to obtain the same effect as in the case of the engine load.

In addition to the exhaust valve closing timing, the engine control device 26 may also change the rate of change of the exhaust valve opening timing, which is the timing at which the exhaust valve 121 is opened, between the critical engine speed range and other engine speed ranges.

10 marine diesel engine 11 engine body 12 supercharger 13 EGR system 14 demister unit 26 engine control device 41A EGR inlet valve 41B EGR outlet valve 42 scrubber 47 EGR blower 48 air cooler (cooler)
51 Auxiliary Compressor 60 EGR Control Device 62 Rotational Speed Detector 64 Fuel Input Amount Detector 65 Scavenging Air Pressure Detector 66 Oxygen Concentration Detector 111 Base Plate 112 Frame 113 Cylinder Jacket 114 Tension Bolt (Tie Bolt/Connecting Member)
115 nut 116 cylinder liner 117 cylinder cover 118 space 119 piston 120 combustion chamber 121 exhaust valve 122 exhaust gas pipe 123 piston rod 124 crankshaft 125 bearing 126 crank 127 connecting rod 128 guide plate 129 crosshead

Claims (7)

an engine body that opens and closes an exhaust valve to control the exhaust of air in the combustion chamber;
A turbine that rotates with exhaust gas discharged from the engine body, and a compressor that is connected to the turbine with a rotating shaft and rotates with the rotation of the turbine to generate compressed air, and supplies compressed air to the engine body. a supercharger that supplies
an EGR system that recirculates part of the exhaust gas discharged from the engine body to the engine body as combustion gas;
The drive of the engine body is controlled, and the operation of the exhaust valve is controlled based on an exhaust valve closing timing pattern in which the closing timing of the exhaust valve in the combustion cycle becomes later as the engine load of the engine body increases. an engine controller;
an EGR control device that controls driving of the EGR system;
The exhaust valve closing timing pattern is the relationship between the engine load and the timing of the crank angle of the piston that closes the exhaust valve,
When the operating condition of the engine body is the same engine load, the timing for closing the exhaust valve when the EGR system is operating is the timing for closing the exhaust valve when the EGR system is stopped. It is set earlier than the timing,
When the operating condition of the engine main body is the engine load under the threshold condition, and the timing of closing the exhaust valve when the EGR system is in operation is the engine load under the operating condition of the engine main body under the threshold condition. is set earlier than the timing of closing the exhaust valve when the EGR system is stopped, and
The engine load of the threshold condition is one point of engine load set in the range of 20% or more and 60% or less of the engine load ,
The threshold condition is set to stop the EGR system when the operating condition of the engine main body is lower than the engine load under the threshold condition, and the engine load under the operating condition of the engine main body is the threshold condition. A marine diesel engine, characterized in that the EGR system is set to operate under conditions of a higher load than the above . Regarding the exhaust valve closing timing pattern, when the engine load of the engine body is operated at any load, the timing at which the exhaust valve is closed when the EGR system is operating is determined by comparison with the same engine load. 2. The marine diesel engine according to claim 1, wherein the closing timing of the exhaust valve is set earlier than the closing timing of the exhaust valve when the EGR system is stopped. Having an auxiliary compressor for compressing air to be supplied to the engine body,
The exhaust valve closing timing pattern is characterized in that when the EGR system is operating and the auxiliary compressor is driving, the timing of closing the exhaust valve is constant even if the engine load changes. A marine diesel engine according to claim 2. an engine body that opens and closes an exhaust valve to control the exhaust of air in the combustion chamber;
A turbine that rotates with exhaust gas discharged from the engine body, and a compressor that is connected to the turbine with a rotating shaft and rotates with the rotation of the turbine to generate compressed air, and supplies compressed air to the engine body. a supercharger that supplies
an EGR system that recirculates part of the exhaust gas discharged from the engine body to the engine body as combustion gas;
The drive of the engine body is controlled, and the operation of the exhaust valve is controlled based on an exhaust valve closing timing pattern in which the closing timing of the exhaust valve in the combustion cycle becomes later as the engine load of the engine body increases. an engine controller;
an EGR control device that controls driving of the EGR system;
an auxiliary compressor for compressing air to be supplied to the engine body,
The exhaust valve closing timing pattern is the relationship between the engine load and the timing of the crank angle of the piston that closes the exhaust valve,
When the operating condition of the engine body is the same engine load, the timing for closing the exhaust valve when the EGR system is operating is the timing for closing the exhaust valve when the EGR system is stopped. It is set earlier than the timing,
The timing of closing the exhaust valve when the operating condition of the engine main body is an engine load whose operating condition is a threshold condition and the EGR system is operating is the engine load whose operating condition of the engine main body is a threshold condition. and is set earlier than the timing of closing the exhaust valve when the EGR system is stopped,
The engine load of the threshold condition is one point of engine load set in the range of 20% or more and 60% or less of the engine load,
The threshold condition is set to stop the EGR system when the operating condition of the engine main body is lower than the engine load under the threshold condition, and the engine load under the operating condition of the engine main body is the threshold condition. If the load is higher than the condition, the EGR system will be set to operate,
In the exhaust valve closing timing pattern, the difference between the timing of closing the exhaust valves when the EGR system is operating and the timing of closing the exhaust valves when the EGR system is stopped is determined by the EGR system. is operating and the auxiliary compressor is maximized under operating conditions in which the auxiliary compressor is switched from being driven to being stopped. The auxiliary compressor compresses the air supplied to the engine body when the operating condition of the engine body is lower than the engine load of the threshold condition, and the auxiliary compressor compresses the air supplied to the engine body when the operating condition of the engine body is the threshold value. 5. A marine diesel engine according to claim 3 or 4, which is shut down when operating at a load higher than a conditional engine load. The EGR system includes an exhaust gas recirculation line that recirculates part of the exhaust gas discharged from the engine body to the engine body as combustion gas,
an EGR valve provided in the exhaust gas recirculation line;
A marine diesel engine according to any one of claims 1 to 5, further comprising a scrubber for injecting liquid into the combustion gas flowing through the exhaust gas recirculation line. 7. A marine diesel engine according to any one of claims 1 to 6, wherein the EGR system supplies recirculated exhaust gas to the compressor, which is axially connected to the turbine.

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