JP2023055818A - engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine which can operate while switching between a gas mode and a diesel mode.

SOLUTION: An engine 21 includes a main fuel injection valve 79, a pilot fuel injection valve 82, a liquid fuel supply rail pipe 42, a pilot fuel supply rail pipe 47, and an exhaust manifold 44. The liquid fuel supply rail pipe 42 supplies liquid fuel toward the main fuel injection valve 79 in a diffusion combustion system. The pilot fuel supply rail pipe 47 supplies pilot fuel toward the pilot fuel injection valve 82 in a premixed combustion system. The exhaust manifold 44 collects an exhaust gas generated by combustion in the combustion chamber 110 of each cylinder and discharges the exhaust gas to the outside. The liquid fuel supply rail pipe 42 and the pilot fuel supply rail pipe 47 are disposed at positions lower than the exhaust manifold 44.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2023,JPO&INPIT

Description

The present invention relates to engine construction.

2. Description of the Related Art Conventionally, an engine provided with a load measuring device for measuring engine load is known. Patent Document 1 discloses an engine of this kind. The engine of Patent Document 1 has an engine control device that controls each part of the engine, and the engine control device receives a measurement signal from a load measuring device such as a watt transducer or a torque sensor, and calculates the load of the engine device. It is configured.

Measuring the load applied to the engine as in Patent Document 1 is essential for proper combustion control of the engine. If the engine is operated with the load measuring device malfunctioning, the amount of air necessary for combustion will be excessive or deficient, which will cause the stability of combustion to deteriorate.

Japanese Patent Application Laid-Open No. 2015-230000

SUMMARY OF THE INVENTION An object of the present invention is to provide an engine that can be operated by switching between a gas mode and a diesel mode.

The problems to be solved by the present invention are as described above, and the means for solving the problems will now be described.

According to the aspect of the present invention, an engine having the following configuration is provided. That is, the engine has a premixed combustion method in which gaseous fuel is mixed with air and then flows into the combustion chamber of each cylinder, and a diffusion combustion method in which liquid fuel is injected into the combustion chamber of each cylinder and burned. It is possible. The engine includes a main fuel injector, a pilot fuel injector, a liquid fuel supply rail line, a pilot fuel supply rail line, and an exhaust manifold. The main fuel injection valve supplies liquid fuel to the combustion chamber during diffusion combustion. The pilot fuel injection valve supplies pilot fuel to the combustion chamber for the purpose of igniting gaseous fuel during combustion in the premixed combustion method. The liquid fuel supply rail pipe supplies the liquid fuel toward the main fuel injection valve by the diffusion combustion method. The pilot fuel supply rail pipe supplies pilot fuel toward the pilot fuel injection valve in the premixed combustion system. The exhaust manifold collects exhaust gas generated by combustion in the combustion chamber of each cylinder and discharges it to the outside. The liquid fuel supply rail pipe and the pilot fuel supply rail pipe are arranged at a position lower than the exhaust manifold.

The engine described above preferably has the following configuration. That is, the liquid fuel supplied to the liquid fuel supply rail pipe is distributed and supplied to the fuel supply pumps provided corresponding to the respective cylinders, and supplied to the respective cylinders from the fuel supply pumps. and the main fuel injection valve for injecting liquid fuel. The fuel supply pump and the main fuel injection valve are connected via a liquid fuel supply passage formed in the cylinder head.

The engine preferably includes a covering member that covers the pilot fuel supply rail pipe and the liquid fuel supply rail pipe.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram schematically showing an engine and two fuel supply paths according to an embodiment of the present invention; FIG. 2 is a partial cross-sectional view of the rear side showing in detail the configuration around the combustion chamber; Top view of the engine. FIG. 3 is a schematic front perspective view showing a liquid fuel supply path; The figure which shows the structure of the intake/exhaust system of an engine. FIG. 2 is a block diagram showing an electrical configuration for controlling the engine; FIG. 5 is a graph for explaining adjustment control of the intake air flow rate in the intake manifold when the engine is operated in gas mode; 4 is a flowchart showing determination processing performed by the engine control device to detect an abnormality in the torque sensor; FIG. 4 is a diagram for explaining supply control of fuel gas and fuel oil when switching from a gas mode to a diesel mode as a result of detection of an abnormality in a torque sensor;

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory view schematically showing an engine 21 and two fuel supply paths 30, 31 according to one embodiment of the present invention. FIG. 2 is a partial rear cross-sectional view showing in detail the configuration around combustion chamber 110. As shown in FIG. FIG. 3 is a plan view of the engine 21. FIG. FIG. 4 is a schematic front perspective view showing a liquid fuel supply path.

The engine (multi-cylinder engine) 21 of this embodiment shown in FIG. It is a so-called dual-fuel engine that can handle both the system and the system. The engine 21 of the present embodiment is installed via a base on the inner bottom plate of the engine room of the ship as a drive source for the propulsion and power generation mechanism of the ship (not shown).

A crankshaft 24 as an engine output shaft protrudes rearward from the rear end portion of the engine 21 . A speed reducer (not shown) is connected to one end of the crankshaft 24 so as to be able to transmit power. A propulsion shaft (not shown) of the ship is arranged so as to align with the crankshaft 24 with the speed reducer interposed therebetween. A propeller is attached to the end of the propulsion shaft to generate a propulsion force for the ship. The speed reducer has a PTO shaft, and a shaft-driven generator (not shown) is connected to the PTO shaft so as to be able to transmit power.

With this configuration, the power of the engine 21 is branched and transmitted to the propulsion shaft and the shaft drive generator via the speed reducer. As a result, the propulsion force of the ship is generated, and the electric power generated by driving the shaft-driven generator is supplied to the electric system in the ship.

Next, the engine 21 will be described in detail with reference to the drawings. The engine 21 is a dual-fuel engine as described above, and includes a premixed combustion method in which fuel gas such as natural gas is mixed with air and burned, and a diffusion combustion method in which liquid fuel (fuel oil) such as heavy oil is diffused and burned. It is possible to select and drive either a combustion method or a combustion method.

In the following description, the operation mode by the premixed combustion method (premixed combustion mode) may be called "gas mode", and the operation mode by the diffusion combustion method (diffusion combustion mode) may be called "diesel mode". The gas mode uses natural gas to reduce emissions of substances of concern (nitrogen oxides, sulfur oxides, particulate matter, etc.), making it easier to comply with environmental regulations. Efficient operation can be realized.

In the following description, the positional relationship between the front, rear, left, and right in the configuration of the engine 21 will be described with the side connected to the reduction gear as the rear side. Therefore, the front-rear direction can be rephrased as a direction parallel to the axis of the crankshaft 24 , and the left-right direction can be rephrased as a direction perpendicular to the axis of the crankshaft 24 . However, this description does not limit the orientation of the engine 21, and the engine 21 can be installed in various orientations depending on the application.

As shown in FIG. 1, two systems of fuel supply paths 30 and 31 are connected to the engine 21 . A gas fuel tank 32 that stores liquefied natural gas (LNG) is connected to one fuel supply path 30, and a liquid fuel tank that stores marine diesel oil (MDO) is connected to the other fuel supply path 31. 33 are connected. With this configuration, one fuel supply path 30 supplies fuel gas to the engine 21 and the other fuel supply path 31 supplies fuel oil to the engine 21 .

The fuel supply path 30 includes, in order from the upstream side, a gas fuel tank 32 that stores gaseous fuel in a liquefied state, a vaporization device 34 that vaporizes the liquefied fuel in the gas fuel tank 32, and fuel from the vaporization device 34 to the engine 21. and a gas valve unit 35 for adjusting the amount of gas supplied.

The engine 21 is an in-line multi-cylinder engine configured by assembling a cylinder head 26 on a cylinder block 25, as shown in FIGS. The crankshaft 24 is rotatably supported in the lower portion of the cylinder block 25 with its axis 24c oriented in the longitudinal direction as shown in FIG.

In the cylinder block 25 , a plurality of (six in this embodiment) cylinders are arranged in a row (serially) along the axis of the crankshaft 24 . As shown in FIG. 2, each cylinder accommodates a piston 78 so as to be vertically slidable. The piston 78 is connected to the crankshaft 24 via a rod (not shown).

As shown in FIG. 3, six cylinder heads 26 are attached to the cylinder block 25 so as to cover the respective cylinders from above. A cylinder head 26 is provided for each cylinder and fixed to the cylinder block 25 using a head bolt 99 . As shown in FIG. 2 , in each cylinder, a combustion chamber 110 is formed in a space surrounded by the top surface of the piston 78 and the cylinder head 26 .

As shown in FIG. 3, the plurality of head covers 40 are arranged in a row on the cylinder head 26 along the direction of the axis 24c of the crankshaft 24 (front-rear direction) so as to correspond to each cylinder. As shown in FIG. 2, inside each head cover 40 is housed a valve mechanism including push rods and rocker arms for operating the intake and exhaust valves. When the intake valve is open, intake air from the intake manifold 67 can be taken into the combustion chamber 110 . With the exhaust valve open, the exhaust from the combustion chamber 110 can be discharged to the exhaust manifold 44 .

As shown in FIG. 2, near the right side of the head cover 40, an upper end portion of a pilot fuel injection valve 82, which will be described later, is arranged. The pilot fuel injection valve 82 is inserted inside the cylinder head 26 and extends obliquely downward toward the combustion chamber 110 .

As shown in FIG. 2, on the right side of the cylinder head 26, a gas manifold 41 is provided for distributing and supplying gas fuel to the combustion chamber 110 of each cylinder during operation in gas mode (premixed combustion mode). . The gas manifold 41 is arranged to extend in the front-rear direction along the right side surface of the cylinder head 26 . Six gas branch pipes 41a corresponding to the combustion chambers 110 of the respective cylinders are connected to the gas manifold 41, and, as shown in FIG. A gas injector 98 is provided. The tip of the gas injector 98 faces an intake branch pipe 67a formed inside the cylinder head 26 corresponding to the cylinder. By injecting gas fuel from the gas injector 98 , gas fuel can be supplied to the intake branch pipe 67 a of the intake manifold 67 .

As shown in FIGS. 2 and 4, on the left side of the cylinder block 25 is a liquid fuel supply unit for distributing and supplying liquid fuel to the combustion chamber 110 of each cylinder during operation in diesel mode (diffusion combustion mode). Rail piping 42 is provided. The liquid fuel supply rail pipe 42 is arranged to extend in the front-rear direction along the left side surface of the cylinder block 25 . The liquid fuel supplied to the liquid fuel supply rail pipe 42 is distributed and supplied to the fuel supply pump 89 provided corresponding to each cylinder. Each cylinder is provided with a main fuel injection valve 79 for injecting liquid fuel supplied from a fuel supply pump 89, as shown in FIG. The main fuel injection valve 79 is arranged so as to be vertically inserted into the cylinder head 26 from above, with its upper end located inside the head cover 40 and its lower end facing the combustion chamber 110 of the cylinder. The fuel supply pump 89 and the main fuel injection valve 79 are connected via a liquid fuel supply passage 106 formed in the cylinder head 26 .

A liquid fuel return collecting pipe 48 for collecting excess fuel returned from each fuel supply pump 89 is provided at a position near the bottom of the liquid fuel supply rail pipe 42 . The liquid fuel return aggregate pipe 48 is arranged parallel to the liquid fuel supply rail pipe 42 and connected to the fuel supply pump 89 . A fuel return pipe 115 for returning the liquid fuel to the liquid fuel tank 33 is connected to the end of the liquid fuel return collecting pipe 48 .

As shown in FIGS. 2 and 4, at a position on the left side of the cylinder block 25 and above the rail pipe 42 for supplying liquid fuel, gas fuel ignition is performed during combustion in the gas mode (premixed combustion mode). A pilot fuel supply rail pipe 47 is provided for the purpose of distributing and supplying the pilot fuel to the combustion chamber 110 of each cylinder. The pilot fuel supply rail pipe 47 is arranged to extend in the front-rear direction along the left side surface of the cylinder block 25 . Each cylinder is provided with a pilot fuel injection valve 82 for injecting liquid fuel (pilot fuel) supplied from the pilot fuel supply rail pipe 47, as shown in FIGS. The pilot fuel injection valve 82 is arranged so as to be obliquely inserted into the cylinder head 26 from above, its upper end is arranged immediately on the right side of the head cover 40, and its lower end faces the combustion chamber 110 of the cylinder. As shown in FIG. 4, a pilot fuel branch pipe 109 is provided to branch from the pilot fuel supply rail pipe 47 corresponding to each cylinder. The pilot fuel branch pipe 109 is arranged to pass between the side-by-side head covers 40 and is connected to the upper end of the pilot fuel injection valve 82 . The pilot fuel branch pipe 109 is covered with a branch pipe cover 105 for preventing leaked fuel from scattering.

As shown in FIGS. 2 and 4, a step is formed in the upper part of the left side of the engine 21, which is composed of the cylinder block 25 and the cylinder head 26, and a pilot fuel supply rail pipe 47 is attached to the step. , a liquid fuel supply rail pipe 42 and a fuel supply pump 89 are arranged. A side cover 43 is attached to the cylinder block 25 and the cylinder head 26 so as to cover the stepped portion. The pilot fuel supply rail pipe 47 , the liquid fuel supply rail pipe 42 , and the fuel supply pump 89 are covered with a side cover 43 .

As shown in FIG. 3 and the like, a speed governor 201 for adjusting the fuel injection amount of the fuel supply pump 89 is arranged near one end in the direction in which the fuel supply pumps 89 are arranged. This speed governor 201 can rotate a control transmission shaft 202 arranged in parallel with the liquid fuel supply rail pipe 42 and the like inside the side cover 43 . This control transmission shaft 202 is connected to the control racks of the fuel supply pumps 89 provided for the number of cylinders. The speed governor 201 rotates the control transmission shaft 202 to displace the control rack of the fuel supply pump 89, thereby changing the pumping amount of the fuel supply pump 89 (the injection amount of the main fuel injection valve 79). be able to.

As shown in FIG. 2, at a position on the upper right side of the cylinder head 26 and above the gas manifold 41, there is provided a gas manifold for collecting exhaust gas generated by combustion in the combustion chamber 110 of each cylinder and discharging it to the outside. An exhaust manifold 44 is arranged parallel to the gas manifold 41 . The outer circumference of the exhaust manifold 44 is covered with a heat shielding cover 45 . As shown in FIG. 2, the exhaust manifold 44 is connected to an exhaust branch pipe 44a corresponding to each cylinder. The exhaust branch pipe 44a communicates with the combustion chamber 110 of each cylinder.

An intake manifold 67 for distributing and supplying external air (intake) to the combustion chamber 110 of each cylinder is arranged in parallel with the gas manifold 41 on the right side inside the cylinder block 25 . As shown in FIG. 2 , six intake branch pipes 67 a are formed inside the cylinder head 26 so as to branch from the intake manifold 67 , and each intake branch pipe 67 a communicates with the combustion chamber 110 .

With this configuration, during operation in the diesel mode (diffusion combustion mode), the air supplied from the intake manifold 67 to each cylinder is compressed by the sliding of the piston 78, and the main fuel injection valve 79 is injected into the combustion chamber 110 at an appropriate timing. An appropriate amount of liquid fuel is injected inside. By injecting liquid fuel into the combustion chamber 110, the piston 78 is reciprocated within the cylinder by the propulsive force obtained from the explosion occurring in the combustion chamber 110, and the reciprocating motion of the piston 78 moves the crankshaft 24 through the rod. Power is obtained by converting it into rotational motion.

On the other hand, during operation in the gas mode (premixed combustion method), the gas fuel from the gas manifold 41 is injected from the gas injector 98 into the intake branch pipe 67a, whereby the air supplied from the intake manifold 67 and the gas mixed with fuel. By injecting a small amount of pilot fuel from the pilot fuel injection valve 82 into the combustion chamber 110 at an appropriate timing when the mixture of air and gas fuel introduced into the cylinder is compressed by the sliding of the piston 78, gas fuel is ignited. The piston 78 reciprocates in the cylinder by the propulsive force obtained by the explosion in the combustion chamber 110, and the reciprocating motion of the piston 78 is converted into the rotary motion of the crankshaft 24 through the rod to obtain power.

Exhaust gas generated by combustion is pushed out of the cylinder by the motion of the piston 78, collected in the exhaust manifold 44, and then discharged to the outside, both when operating in the diesel mode and in the gas mode.

A fuel oil pump 56 , a cooling water pump (not shown), and a lubricating oil pump are provided on the front end face (front face) of the engine 21 so as to surround the front end portion of the crankshaft 24 . A cooling water pump, a lubricating oil pump, and a fuel oil pump 56, which are provided on the outer peripheral side of the crankshaft 24, are driven by appropriately transmitting rotational power from the crankshaft 24. As shown in FIG.

The fuel oil pump 56 shown in FIG. 4 is rotationally driven to supply fuel oil (liquid fuel) supplied from the liquid fuel tank 33 of FIG. It is sent to the rail pipe 47 for use. A pilot fuel filter for filtering the fuel oil is provided in the middle of the fuel path from the liquid fuel tank 33 to the fuel oil pump 56 .

In addition, a fuel oil pump (not shown) (other than the fuel oil pump 56) is rotationally driven with the rotation of the crankshaft 24, so that the fuel pump sucks fuel oil from the liquid fuel tank 33, It is sent to the liquid fuel supply rail pipe 42 via the liquid fuel supply main pipe 108 shown in FIG. A main fuel filter for filtering the fuel oil is provided in the middle of the fuel oil supply path from the liquid fuel tank 33 to the liquid fuel supply rail pipe 42 .

As shown in FIG. 4 , the pilot fuel supply main pipe 107 , the liquid fuel supply main pipe 108 , and the fuel return pipe 115 are arranged immediately in front of the cylinder block 25 along the left side surface of the cylinder block 25 . The pilot fuel supply main pipe 107, the liquid fuel supply main pipe 108, and the fuel return pipe 115 are connected to the cylinder block 25 via a plurality of clamp members 111 provided so as to protrude leftward from the front end surface of the cylinder block 25. It is arranged to extend vertically along the left side surface.

An engine control device (control device) 73 that controls the operation of each part of the engine 21 is provided on the rear right side of the cylinder block 25 via a support member (not shown). As shown in FIG. 6, the engine control device 73 acquires data from sensors (pressure sensor, torque sensor, etc.) provided in each part of the engine 21, and performs various operations of the engine 21 (fuel injection, flow rate adjustment, etc.). change in valve opening, etc.).

Next, the configuration for intake and exhaust in the engine 21 will be described with reference to FIG. FIG. 5 is a schematic diagram showing the configuration of the intake and exhaust system of the engine 21. As shown in FIG.

As shown in FIG. 5, in the engine 21, six cylinders are arranged in a line. Each cylinder is connected to an intake manifold 67 via an intake branch pipe 67a, and is connected to the exhaust manifold 44 via an exhaust branch pipe 44a.

The intake manifold 67 is connected to the intake flow path 15 leading to the outside of the engine 21 so that external air can be taken into each cylinder. A compressor 49 b of the supercharger 49 and an intercooler 51 are arranged in the middle of the intake passage 15 .

Between the compressor 49b and the intercooler 51, a main throttle valve (main throttle valve) V1 for adjusting the flow rate of air supplied to the intake manifold 67 is provided. The main throttle valve V<b>1 is configured as a flow control valve, and its opening degree is configured to be controllable by an electric signal from the engine control device 73 .

The intake passage 15 is provided with an intake bypass passage 17 that connects the air outlet side of the intercooler 51 and the air inlet side of the compressor 49b. A portion of the air that has passed through the compressor 49b is recirculated through the intake bypass flow path 17. As shown in FIG. The intake bypass flow path 17 is provided with an intake bypass valve V<b>2 for adjusting the flow rate of air passing through the intake bypass flow path 17 . The intake bypass valve V<b>2 is configured as a flow control valve like the main throttle valve V<b>1 , and its opening degree is configured to be controllable by an electrical signal from the engine control device 73 . By changing the opening degree of the intake bypass valve V2, the flow rate of air supplied to the intake manifold 67 can be adjusted.

The exhaust manifold 44 is connected to the exhaust flow path 16 leading to the outside of the engine 21, and can discharge the air exhausted from each cylinder to the outside. A turbine 49 a of the supercharger 49 is arranged in the middle of the exhaust flow path 16 .

The exhaust passage 16 is provided with an exhaust bypass passage 18 that connects the exhaust outlet side of the exhaust manifold 44 and the exhaust outlet side of the turbine 49a (bypasses the turbine 49a). A part of the exhaust gas sent from the exhaust manifold 44 to the exhaust passage 16 passes through the exhaust bypass passage 18 and reaches downstream from the exhaust outlet side of the turbine 49a, and then is discharged to the outside. The exhaust bypass flow path 18 is provided with an exhaust bypass valve V3 for adjusting the flow rate of the exhaust gas passing through the exhaust bypass flow path 18 . The exhaust bypass valve V<b>3 is configured as a flow control valve like the main throttle valve V<b>1 , and its opening degree is configured to be controllable by an electrical signal from the engine control device 73 . By changing the valve opening degree of the exhaust bypass valve V3, it is possible to adjust the flow rate of the exhaust gas flowing into the turbine 49a and adjust the amount of air compressed in the compressor 49b. That is, the air flow rate supplied to the intake manifold 67 can be adjusted by adjusting the opening degree of the exhaust bypass valve V3.

Next, feedback control on the valve opening degree of the flow control valve will be described with reference to FIGS. 6 and 7. FIG. FIG. 6 is a block diagram showing an electrical configuration for controlling engine 21. As shown in FIG. FIG. 7 is a graph illustrating adjustment control of the intake air flow rate in the intake manifold 67 when the engine 21 is operated in the gas mode.

As shown in FIG. 6 , the engine control device 73 is configured to be able to control the pilot fuel injection valve 82 , the fuel supply pump 89 and the gas injector 98 . The engine control device 73 can supply liquid fuel (pilot fuel) to the combustion chamber 110 by opening and closing the pilot fuel injection valve 82 . The engine control device 73 can supply liquid fuel (main fuel) from the fuel supply pump 89 to the combustion chamber 110 via the main fuel injection valve 79 by opening and closing the control valve of the fuel supply pump 89 . The engine control device 73 can adjust the amount of liquid fuel injected from the main fuel injection valve 79 by controlling the speed governor 201 . The engine control device 73 can supply gas fuel to the intake branch pipe 67 a of the intake manifold 67 by controlling the gas injector 98 .

Further, the engine control device 73 is configured to be able to control the main throttle valve V1, the intake bypass valve V2, and the exhaust bypass valve V3. As described above, the engine control device 73 can adjust the flow rate of air flowing into the intake manifold 67 by controlling the valve opening degrees of the main throttle valve V1, the intake bypass valve V2, and the exhaust bypass valve V3. can.

As shown in FIG. 6 , the engine control device 73 is configured to be able to receive signals from various sensors provided in each part of the engine 21 . Also, the engine control device 73 is configured to be able to communicate with the machine-side operation control device 71 .

In-cylinder pressure sensors 63 are arranged in some or all of the six cylinders of the engine 21 . The in-cylinder pressure sensor 63 includes a piezoelectric element, a strain gauge, or the like, and can detect the pressure inside the cylinder (indicated mean effective pressure, IMEP). The in-cylinder pressure detected by the in-cylinder pressure sensor 63 is output to the engine control device 73 .

An intake manifold 67 of the engine 21 is provided with an intake pressure sensor 39 that measures the air pressure in the intake manifold 67 . The intake pressure sensor 39 can be configured using, for example, a semiconductor strain gauge. The intake pressure detected by the intake pressure sensor 39 is output to the engine control device 73 .

A torque sensor (load detector) 64 is attached to an appropriate position of the engine 21 (for example, near the crankshaft 24). As the torque sensor 64, for example, a flange type sensor that detects torque using a strain gauge can be used. The engine load (engine torque) detected by the torque sensor 64 is output to the engine control device 73 .

An engine speed sensor 65 is attached to an appropriate position of the engine 21 (for example, the cylinder block 25). The engine speed sensor 65 is composed of, for example, a sensor and a pulse generator, and can be configured to generate a pulse signal according to the rotation of the crankshaft 24 . The engine speed detected by the engine speed sensor 65 is output to the engine control device 73 .

When operating the engine 21 in the diesel mode, the engine control device 73 controls the opening and closing of the control valve in the fuel supply pump 89 to generate combustion in each cylinder at a predetermined timing. That is, by opening the control valve of the fuel supply pump 89 in accordance with the injection timing of each cylinder, the fuel oil is injected into each cylinder through the main fuel injection valve 79 and ignited inside the cylinder. On the other hand, injection of fuel gas from the gas injector 98 and injection of pilot fuel from the pilot fuel injection valve 82 are stopped in the diesel mode.

In the diesel mode, the engine control device 73 adjusts the injection timing from the main fuel injection valve 79 in each cylinder based on the engine load detected by the torque sensor 64 and the engine speed detected by the engine speed sensor 65. the feedback control. As a result, the crankshaft 24 of the engine 21 rotates at an engine speed corresponding to the propulsion speed of the ship so that the torque required by the ship's propulsion and power generation mechanism can be obtained. The engine control device 73 also controls the valve opening of the main throttle valve V1 based on the air pressure in the intake manifold 67 detected by the intake pressure sensor 39 . As a result, compressed air is supplied from the compressor 49b to the intake manifold 67 so as to achieve an air flow rate required for engine output.

When the engine 21 is operated in the gas mode, the engine control device 73 controls the opening and closing of the valve in the gas injector 98 to supply the fuel gas to the intake branch pipe 67a, thereby supplying the fuel gas to the air from the intake manifold 67. to supply premixed fuel to each cylinder. In addition, the engine control device 73 controls the opening and closing of the pilot fuel injection valve 82 and injects the pilot fuel into each cylinder at a predetermined timing to generate an ignition source, and in each cylinder to which the premixed gas is supplied, Let it burn. On the other hand, injection of the main fuel from the main fuel injection valve 79 is stopped in the gas mode.

In the gas mode, the engine control device 73 controls the injection flow rate of the fuel gas by the gas injector 98 based on the engine load detected by the torque sensor 64 and the engine speed detected by the engine speed sensor 65. Injection timing by the pilot fuel injection valve 82 in the cylinder is feedback-controlled.

Further, the engine control device 73 controls the main throttle valve V1, intake bypass valve V2, and the exhaust bypass valve V3 are controlled as shown in FIG. 7, for example.

First, control of the main throttle valve V1 will be described with reference to FIG. 7(a). L1, L2, L3, and L4 shown in the graph of FIG. 7 are predetermined engine load values (where L1<L2<L3<L4). This is the engine load corresponding to the boundary with the load area.

When the engine load is less than the predetermined value L1, the engine control device 73 sets the target pressure of the intake manifold 67 based on the relationship shown in FIG. PID control (feedback control) is performed on the valve opening degree of the main throttle valve V1 so that the actual pressure detected by is closer to the target pressure.

When the engine load is equal to or greater than the predetermined value L1 and less than the predetermined value L2, the engine control device 73 refers to the first data table D1 storing the valve opening degree of the main throttle valve V1 with respect to the engine load, and responds to the engine load. Map control is performed so that the valve opening degree of the main throttle valve V1 is adjusted. The first data table D1 is defined to gradually increase the valve opening of the main throttle valve V1 as the engine load increases.

When the engine load is equal to or greater than the predetermined value L2, the engine control device 73 controls the main throttle valve V1 to be fully opened. The predetermined value L2 of the engine load is set lower than the value Lt at which the air pressure of the intake manifold 67 becomes the atmospheric pressure.

Next, control of the intake bypass valve V2 will be described with reference to FIG. 7(b).

When the engine load is less than the predetermined value L3, the engine control device 73 controls the intake bypass valve V2 to be fully closed.

When the engine load is equal to or greater than the predetermined value L3, the engine control device 73 sets the target pressure of the intake manifold 67 according to the engine load based on the relationship shown in FIG. PID control (feedback control) is performed on the valve opening degree of the intake bypass valve V2 so that the actual pressure detected by is closer to the target pressure.

Next, control of the exhaust bypass valve V3 will be described with reference to FIG. 7(c).

When the engine load is less than the predetermined value L1, the engine control device 73 controls the exhaust bypass valve V3 to be fully open.

When the engine load is equal to or greater than the predetermined value L1, the engine control device 73 refers to the second data table D2 storing the valve opening degree of the exhaust bypass valve V3 corresponding to the engine load. Map control is performed so that the valve opening is The second data table D2 gradually decreases the degree of opening of the exhaust bypass valve V3 as the engine load increases from a predetermined value L1 to a predetermined value L2, and closes the exhaust bypass valve V3 from a predetermined value L2 to a predetermined value L3. The exhaust bypass valve V3 is set to be fully closed, and the degree of opening of the exhaust bypass valve V3 is gradually increased as it increases from the predetermined value L3.

As described above, the engine control device 73 adjusts the air pressure of the intake manifold 67 by controlling the main throttle valve V1, the intake bypass valve V2, and the exhaust bypass valve V3. As a result, compressed air is supplied from the compressor 49b to the intake manifold 67 so that the air flow rate required for the engine output is obtained, and the air-fuel ratio of the fuel gas supplied from the gas injector 98 is adjusted to a value corresponding to the engine output. can be adjusted to

By the way, in a dual fuel engine like this embodiment, the air-fuel ratio differs between the diesel mode and the gas mode, and the required air flow rate in the gas mode is higher than that in the diesel mode for the same load. few. Therefore, while the supercharger 49 must be designed based on use in the diesel mode, it is also necessary in the gas mode to supply air at a flow rate suitable for the air-fuel ratio of the gas mode.

In this respect, in the present embodiment, by adopting the above configuration, even if the configuration of the turbocharger 49 is optimized for operation in the diesel mode, during operation in the gas mode, By controlling the valve opening degree of the intake bypass valve V2, the responsiveness of the pressure control of the intake manifold 67 can be enhanced. Therefore, even when the load fluctuates, the amount of air necessary for combustion can be prevented from becoming excessive or insufficient, so even when the supercharger 49 having a configuration optimized for operation in the diesel mode is used, it can be operated satisfactorily in the gas mode. be able to.

Further, by controlling the opening degree of the exhaust bypass valve V3 according to fluctuations in the engine load, it is possible to supply air to the engine 21 in accordance with the air-fuel ratio required for combustion of the fuel gas. In addition, by controlling the intake bypass valve V2 with good response, it is possible to increase the response speed to load fluctuations in the gas mode. knocking or the like caused by

By the way, it is important to properly detect the engine load for proper combustion control of the engine 21. If the engine load cannot be detected by the torque sensor 64 for some reason, the output will decrease, fuel consumption will deteriorate, and so on. cause. In particular, when a dual fuel engine such as that of this embodiment is operated in the gas mode, even if the load fluctuates as described above, in order to avoid knocking and misfiring, it is necessary to accurately detect the engine load and control the air flow. It becomes necessary to control the flow rate.

In this embodiment, the engine load is detected by the torque sensor 64 of FIG. 6 as a signal whose current value increases as the load increases, for example, within the range of 4 mA to 20 mA. Therefore, when the current value of the torque sensor 64 is 4 mA, it means that the engine load is substantially zero. cannot be denied either.

In this regard, in this embodiment, the engine control device 73 calculates the indicated mean effective pressure from a data string obtained by detecting the in-cylinder pressure with the in-cylinder pressure sensor 63, and the obtained indicated mean effective pressure is a predetermined value. If the engine load detection value of the torque sensor 64 indicates no load even though it is equal to or greater than the threshold value, it is determined that an abnormality has occurred in detection of the engine load by the torque sensor 64 .

That is, if the in-cylinder pressure detected by the in-cylinder pressure sensor 63 is equal to or higher than a predetermined level, a load of at least a certain magnitude should be applied to the engine 21, but the torque sensor 64 is not affected. indicates zero, there is a high possibility that some abnormality has occurred in the detection of the engine load by the torque sensor 64 . Using this fact, the engine control device 73 determines that the torque sensor 64 is abnormal when the above situation occurs, and displays that fact on the display 72 provided in the machine-side operation control device 71. is configured to As a result, it is possible to appropriately discover an abnormality related to the detection of the engine load, and to prompt an early response.

Next, specific control for detecting an abnormality in the torque sensor 64 described above will be described in detail mainly with reference to FIG. FIG. 8 is a flowchart showing determination processing performed by the engine control device 73 to detect an abnormality in the torque sensor 64. As shown in FIG. FIG. 9 is a diagram illustrating the supply control of fuel gas and fuel oil when the gas mode is switched to the diesel mode as a result of detection of an abnormality in the torque sensor 64. FIG.

As shown in FIG. 8, in the engine 21 operating in the gas mode, the engine control device 73 controls the amount of fuel gas injected by the gas injector 98 so that the engine speed detected by the engine speed sensor 65 approaches the target value. (speed regulation control, step S101).

Next, the engine control device 73 controls the opening degrees of the main throttle valve V1, the intake bypass valve V2 and the exhaust bypass valve V3 according to the engine load detected by the torque sensor 64 (step S102). As for the control method, as described with reference to FIG. 7, depending on the magnitude of the engine load, any one of control to fix at fully open, control to fix at fully closed, map control, and PID control (feedback control). is selected.

After that, the engine control device 73 determines whether or not the engine load obtained in step S102 is substantially no load (step S103).

If it is determined in step S103 that the detected engine load is not substantially zero, the process returns to step S101 to repeat the process.

If it is determined in step S103 that the detected engine load is substantially zero, the indicated mean effective pressure is calculated from the pressure detected by the in-cylinder pressure sensor 63, and the indicated mean effective pressure is greater than or equal to a predetermined threshold value. It is determined whether or not (step S104).

If it is determined in step S104 that the indicated mean effective pressure is less than the threshold, the process returns to step S101 to repeat the process.

If it is determined in step S104 that the indicated mean effective pressure is equal to or greater than the threshold, the engine control device 73 determines that some abnormality has occurred in the torque sensor 64, and outputs a message to that effect to the machine-side operation control unit. It is displayed on the display 72 of the device 71 (step S105). As a result, the operator of the engine 21 can quickly notice that there is an abnormality in the detection of the engine load and can take appropriate measures.

After that, the engine control device 73 switches the combustion mode to the diesel mode (step S106), and ends the processing in the gas mode. In this way, by switching from the gas mode to the diesel mode when an abnormality occurs in the detection of the engine load, it is possible to ensure the continuity of operation required for large marine engines.

Note that switching from the gas mode to the diesel mode in the dual fuel engine can be done immediately or gradually.

For example, if the engine 21 has been operating in gas mode, but as a result of navigation of the ship, it goes out of the regulated waters where the amount of emissions such as nitrogen oxides is restricted, the gas mode is gradually switched to diesel mode. Switching is preferred. In this case, control is performed to gradually decrease the amount of fuel gas injected from the gas injector 98 and gradually increase the amount of liquid fuel injected from the main fuel injection valve 79 .

On the other hand, if an abnormality occurs during operation in gas mode, it is preferable to immediately switch from gas mode to diesel mode. Possible abnormalities include, for example, a decrease in fuel gas pressure, a decrease in pressure in the intake manifold 67, an increase in gas temperature, an increase in air temperature, or an abnormality in various sensors (including an abnormality in the torque sensor 64 described above). can be mentioned. In this case, the amount of fuel gas injected from the gas injector 98 is abruptly reduced to zero, and almost at the same time, the amount of liquid fuel injected from the main fuel injection valve 79 is rapidly increased from zero.

Also in the present embodiment, switching from the gas mode to the diesel mode (step S106) after detecting that the torque sensor 64 has become abnormal is performed instantaneously, not gradually, as shown in FIG.

Generally, the amount of liquid fuel (main fuel) injected from the main fuel injection valve 79 in the diesel mode is obtained from a map based on the engine speed and the engine load. However, since there is an abnormality in the torque sensor 64 as described above, the torque The engine load sensed by sensor 64 is unreliable. Therefore, the engine control device 73 obtains the indicated mean effective pressure from the pressure inside the cylinder detected by the in-cylinder pressure sensor 63, further calculates the net mean effective pressure (BMEP) from this, and calculates the engine load from the net mean effective pressure. is configured to estimate Since the relationship between the indicated mean effective pressure and the net mean effective pressure and the relationship between the net mean effective pressure and the engine load are well known, a detailed description of calculations will be omitted.

After that, the engine control device 73 obtains the initial injection amount of the main fuel (the fuel oil supply amount FO1 shown in FIG. 9) from the above map using the engine speed and the estimated engine load. of liquid fuel is injected from the main fuel injection valve 79 . By configuring in this way, even in a situation where the torque sensor 64 cannot normally detect the engine load, an appropriate amount of liquid fuel can be injected from the main fuel injection valve 79 immediately after switching to the diesel mode, and the engine Rotation speed can be maintained well.

As described above, the engine 21 of this embodiment includes the in-cylinder pressure sensor 63 , the torque sensor 64 and the engine control device 73 . The in-cylinder pressure sensor 63 detects the pressure inside the cylinder. A torque sensor 64 detects the engine load. A detection result of the in-cylinder pressure sensor 63 and a detection result of the torque sensor 64 are input to the engine control device 73 . The engine control device 73 determines that the load detected by the torque sensor 64 is zero (no load), and the in-cylinder pressure obtained from the detection result of the in-cylinder pressure sensor 63 (specifically, the indicated mean effective pressure) is If it is equal to or greater than the threshold, it is determined that the detection by the torque sensor 64 is abnormal.

As a result, it is possible to determine whether or not there is an abnormality in the torque sensor 64 with a simple configuration by utilizing the fact that there is a certain degree of correlation between the in-cylinder pressure and the engine load. As a result, for example, the operator can be urged early to deal with the abnormality.

The engine 21 of this embodiment also includes an intake manifold 67 , a gas injector 98 , and a main fuel injection valve 79 . An intake manifold 67 supplies air into the cylinder. The gas injector 98 injects and mixes the fuel gas with the air supplied from the intake manifold 67 . The main fuel injection valve 79 injects liquid fuel into the cylinder. The engine 21 has a gas mode (premixed combustion mode) in which the gaseous fuel injected by the gas injector 98 is mixed with air and then flows into the combustion chamber 110 in the cylinder (premixed combustion mode), and the main fuel injection valve 79 injects the liquid fuel into the combustion chamber 110. It is possible to operate by switching between a diesel mode (diffusion combustion mode) that burns by injecting fuel into the interior. When the engine control device 73 determines that there is an abnormality in the detection by the torque sensor 64 during operation in the gas mode, it switches from the gas mode to the diesel mode.

As a result, it is possible to prevent the engine 21 from operating in the gas mode when the torque sensor 64 detects the engine load abnormally. As a result, continuity of operation of the engine 21 can be ensured.

Further, in the engine 21 of the present embodiment, the engine control device 73 determines that there is an abnormality in the detection by the torque sensor 64 during operation in the gas mode, and when switching from the gas mode to the diesel mode, the in-cylinder pressure sensor 63 The engine load is estimated by calculation based on the detected value of , and the amount of liquid fuel injected by the main fuel injection valve 79 immediately after switching to the diesel mode is calculated based on the estimated engine load.

As a result, an appropriate amount of liquid fuel can be injected from the main fuel injection valve 79 at the initial stage of switching from the gas mode to the diesel mode. As a result, it is possible to stably operate the engine 21 by preventing a decrease in the engine speed or the like at the time of mode switching.

Although the preferred embodiments of the present invention have been described above, the above configuration can be modified, for example, as follows.

The torque sensor 64 can be configured to output, for example, a voltage value signal corresponding to the engine load instead of outputting a current value signal corresponding to the engine load.

In S104 shown in the flow of FIG. 8, instead of the indicated mean effective pressure (IMEP), for example, the net mean effective pressure (BMEP) may be compared with the threshold.

The load detector is not limited to the torque sensor 64 described above, and a watt transducer, for example, can be used.

In the above embodiment, ignition of the premixture in gas mode is achieved by injecting a small amount of liquid fuel from the pilot fuel injector 82 (micro-pilot ignition). Alternatively, however, ignition may also take place, for example by means of a spark.

In the above embodiment, the engine 21 is used as a driving source for the propulsion and power generation mechanism of the ship, but it is not limited to this and may be used for other purposes.

21 engine 24 crankshaft 43 side cover (coating member)
63 cylinder pressure sensor 64 torque sensor (load detector)
73 engine control device (control device)
78 Piston 79 Main fuel injection valve (fuel injection valve)
98 gas injector 110 combustion chamber

Claims (3)

In an engine that is compatible with a premixed combustion method in which gaseous fuel is mixed with air and then flows into the combustion chamber of each cylinder, and a diffusion combustion method in which liquid fuel is injected into the combustion chamber of each cylinder and burned,
a main fuel injection valve that supplies liquid fuel to the combustion chamber during combustion in the diffusion combustion method;
A pilot fuel injection valve that supplies pilot fuel to the combustion chamber for the purpose of igniting gaseous fuel during combustion in the premixed combustion method;
a liquid fuel supply rail pipe that supplies liquid fuel toward the main fuel injection valve in the diffusion combustion method;
a pilot fuel supply rail pipe that supplies pilot fuel toward the pilot fuel injection valve in the premixed combustion method;
an exhaust manifold that collects exhaust gas generated by combustion in the combustion chamber of each cylinder and discharges it to the outside;
with
The engine according to claim 1, wherein the liquid fuel supply rail pipe and the pilot fuel supply rail pipe are arranged at a position lower than the exhaust manifold. The engine of claim 1, comprising:
The liquid fuel supplied to the liquid fuel supply rail pipe is distributed to the fuel supply pumps provided corresponding to the cylinders, and the liquid supplied from the fuel supply pump is supplied to each cylinder. The main fuel injection valve for injecting fuel is arranged,
An engine according to claim 1, wherein said fuel supply pump and said main fuel injection valve are connected via a liquid fuel supply passage formed in a cylinder head. 3. The engine according to claim 1 or 2,
An engine comprising a coating member covering the pilot fuel supply rail piping and the liquid fuel supply rail piping.

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