JP2020153353A - Uniflow scavenging type two-cycle engine - Google Patents

Abstract

To suppress a misfire at a low load.SOLUTION: A uniflow scavenging type two-cycle engine includes: a scavenging chamber 146 formed with an inflow port 146a; a cylinder 110 with a scavenging port arranged inside the scavenging chamber 146; a plurality of injection ports 154 that are opened in an inner peripheral surface of the cylinder 110, the inside of the scavenging port, or a radially-outer side of the cylinder 110 than the scavenging port and include a first injection port 154a and a second injection port 154b which is located farther apart from the inflow port 146a than the first injection port 154a; a fuel injection device 152 for supplying a fuel gas to the injection ports 154; and a control unit for controlling the fuel injection device 152 to stop supply of the fuel gas to the first injection port 154a and inject the fuel gas from the second injection port 154b when a required output is equal to or less than a threshold.SELECTED DRAWING: Figure 2

Description

The present disclosure relates to a uniflow scavenging two-stroke engine.

In a uniflow scavenging two-stroke engine, gaseous fuel gas may be used as fuel. For example, Patent Document 1 discloses a configuration in which a fuel injection port is formed on the exhaust port side of the cylinder with respect to the scavenging port. A plurality of fuel injection ports are provided so as to be separated from each other in the circumferential direction of the cylinder. The fuel gas injected into the cylinder from the fuel injection port is compressed by the piston together with the scavenging air, and then burned in the combustion chamber.

Japanese Patent No. 6080224

By the way, when the required output of the engine is small, the injection amount of the fuel gas from each fuel injection port becomes small, the fuel gas diffuses and becomes too dilute, and misfire easily occurs.

An object of the present disclosure is to provide a uniflow scavenging two-stroke engine capable of suppressing a misfire at a low load.

In order to solve the above problems, the uniflow scavenging two-stroke engine of the present disclosure includes a scavenging chamber in which an inflow port is formed, a cylinder in which a scavenging port is arranged inside the scavenging chamber, an inner peripheral surface of the cylinder, and scavenging air. A plurality of injections including a first injection port and a second injection port which is opened inside the port or radially outside the cylinder from the scavenging port and is arranged at a distance from the inflow port from the first injection port. The fuel injection device that supplies fuel gas to the port, the injection port, and the fuel injection device are controlled, and when the required output is below the threshold value, the supply of fuel gas to the first injection port is stopped, and the fuel is supplied from the second injection port. It includes a control unit for injecting gas.

The first injection port may be located on the inlet side with respect to the central axis of the cylinder, and the second injection port may be located on the side separated from the inlet with respect to the central axis of the cylinder.

When the control unit stops the supply of the fuel gas to the first injection port, the control unit may delay the injection timing as compared with the case where the fuel gas is injected from all the injection ports.

When the control unit reduces the amount of fuel gas supplied to the first injection port to be smaller than the amount of fuel gas supplied to the second injection port, the control unit injects the second injection port rather than the injection timing of the first injection port. The timing may be retarded.

When the required output decreases across the threshold value, the control unit stops the supply of fuel gas to the first injection port, and the second injection is less than the decrease that is no longer supplied from the first injection port. The amount of fuel supplied to the mouth may be increased.

According to the uniflow scavenging two-stroke engine of the present disclosure, misfire at low load can be suppressed.

FIG. 1 is an explanatory diagram showing an overall configuration of a uniflow scavenging two-stroke engine. FIG. 2 is a diagram for explaining the arrangement of the fuel injection port. FIG. 3 is a block diagram showing a control system of a uniflow scavenging two-stroke engine. FIG. 4 is a first diagram for explaining the processing of the fuel control unit. FIG. 5 is a second diagram for explaining the processing of the fuel control unit. FIG. 6 is a third diagram for explaining the processing of the fuel control unit. FIG. 7 is a fourth diagram for explaining the processing of the fuel control unit. FIG. 8 is a diagram showing a simulation result of a diffusion state of fuel gas near the crown surface of the piston in the combustion chamber. FIG. 9 is a diagram for explaining a modified example. FIG. 10 is a diagram for explaining the arrangement of the fuel pipes.

An embodiment of the present disclosure will be described in detail below with reference to the accompanying drawings. The dimensions, materials, and other specific numerical values shown in the embodiments are merely examples for facilitating understanding, and the present disclosure is not limited unless otherwise specified. In the present specification and the drawings, elements having substantially the same function and configuration are designated by the same reference numerals to omit duplicate description. In addition, elements not directly related to the present disclosure are not shown.

FIG. 1 is an explanatory diagram showing an overall configuration of a uniflow scavenging two-stroke engine 100. The uniflow scavenging two-stroke engine 100 is used, for example, in ships and the like. A cylinder head 112 is provided on one end side of the cylinder 110. A cylinder jacket 114 is provided on the other end side of the cylinder 110. A piston 116 is arranged in the cylinder 110.

The piston 116 reciprocates in the cylinder 110 in the direction of the central axis of the cylinder 110 (the stroke direction of the piston 116, hereinafter simply referred to as the stroke direction). Exhaust, intake, compression, combustion, and expansion are performed between the ascending stroke and the descending stroke of the piston 116. One end of the piston rod 118 is attached to the piston 116. A crosshead 120 is connected to the other end of the piston rod 118.

The crosshead 120 reciprocates in the stroke direction together with the piston 116. The crosshead shoe 122 regulates the movement of the crosshead 120 in the direction perpendicular to the stroke direction (left-right direction in FIG. 1). The connecting rod 124 is connected to the crosshead 120 and the crankshaft 126. The crankshaft 126 rotates due to the operation of the connecting rod 124 accompanying the reciprocating movement of the crosshead 120.

An exhaust valve box 128 is attached to the cylinder head 112. The combustion chamber 130 is formed inside the cylinder 110 by being surrounded by the cylinder head 112, the exhaust valve box 128, and the piston 116 when the piston 116 is on the top dead center side.

An exhaust port 132 is formed in the exhaust valve box 128. The exhaust port 132 is located vertically above the top dead center of the piston 116. The exhaust valve box 128 is provided with an exhaust valve drive device (not shown). The exhaust valve 134 is moved in the stroke direction by the exhaust valve drive device. The movement of the exhaust valve 134 opens and closes the exhaust port 132.

When the exhaust valve 134 is opened, the exhaust gas is exhausted from the combustion chamber 130 through the exhaust port 132. The exhaust gas rotates the turbine T of the turbocharger 138 through the exhaust pipe 136. By this rotational power, the compressor C of the supercharger 138 compresses the active gas and sends it to the cooler 140. The active gas contains an oxidizing agent such as oxygen and ozone, or an air-fuel mixture thereof (for example, air). The cooler 140 is arranged in the scavenging reservoir 144 formed in the casing 142. The cooler 140 cools the compressed active gas. The cooled active gas is sent to the scavenging reservoir 144.

The casing 142 comes into contact with the cylinder jacket 114. The casing 142 is located outside the cylinder 110 in the radial direction (hereinafter referred to as the radial direction) with respect to the cylinder jacket 114. A scavenging chamber 146 is formed inside the cylinder jacket 114. The scavenging reservoir 144 is located on the outer side in the radial direction with respect to the scavenging chamber 146.

A through hole 142a is formed in the wall portion of the casing 142 on the cylinder jacket 114 side. The through hole 142a penetrates the wall portion of the casing 142 on the cylinder jacket 114 side in the opposite direction between the casing 142 and the cylinder jacket 114.

A through hole 114a is formed in a portion of the cylinder jacket 114 facing the through hole 142a of the casing 142. The through hole 114a of the cylinder jacket 114 penetrates the wall portion of the cylinder jacket 114 in the same direction as the through hole 142a of the casing 142.

The scavenging reservoir 144 and the scavenging chamber 146 communicate with each other through the through holes 114a and 142a. In the scavenging chamber 146, the opening of the through hole 114a serves as an inflow port 146a into which the compressed active gas flows from the scavenging reservoir 144.

The other end of the cylinder 110 is located in the scavenging chamber 146. A scavenging port 148 is formed in a portion of the cylinder 110 located inside the scavenging chamber 146. The scavenging port 148 opens into the scavenging chamber 146.

The scavenging port 148 penetrates from the inner peripheral surface to the outer peripheral surface of the cylinder 110. A plurality of scavenging ports 148 are provided at intervals in the circumferential direction of the cylinder 110 (hereinafter, simply referred to as the circumferential direction). The scavenging port 148 is located on the top dead center side of the cylinder 110 with respect to the bottom dead center of the piston 116.

When the crown surface of the piston 116 moves to the bottom dead center side of the scavenging port 148, the active gas is sucked from the scavenging port 148 into the internal space S of the cylinder 110 due to the differential pressure between the internal pressure of the scavenging chamber 146 and the internal pressure of the cylinder 110. Will be done.

A fuel injection port 150 is formed in the cylinder 110 vertically above the cylinder jacket 114 (on the top dead center side of the piston 116). The fuel injection port 150 penetrates from the inner peripheral surface to the outer peripheral surface of the cylinder 110. Two fuel injection ports 150 are provided. A fuel injection device 152 is provided at each fuel injection port 150.

Here, a case where two fuel injection devices 152 are provided has been described. However, three or more fuel injection devices 152 may be provided at intervals in the circumferential direction. In this case, the cylinder 110 is formed with the same number of fuel injection ports 150 as the fuel injection device 152.

The fuel injection device 152 injects fuel gas supplied from a fuel pipe (not shown). The injected fuel gas is sprayed onto the active gas sucked into the internal space S of the cylinder 110 via the fuel injection port 150. The fuel gas is produced by, for example, gasifying LNG (liquefied natural gas). The fuel gas is not limited to LNG, and for example, gasified LPG (liquefied petroleum gas), light oil, heavy oil, or the like may be used.

Since the fuel injection port 150 is provided on the scavenging port 148 side of the combustion chamber 130, the fuel gas injection pressure can be suppressed to a small value. The injected fuel gas is compressed while flowing toward the combustion chamber 130 as the piston 116 rises while being mixed with the active gas. The cylinder head 112 is provided with a pilot injection valve (not shown). Fuel oil is injected into the combustion chamber 130 from the pilot injection valve. The fuel oil is vaporized by the heat of the gas in the combustion chamber 130. The fuel oil vaporizes and spontaneously ignites, and the temperature of the combustion chamber 130 rises. Then, the air-fuel mixture of the fuel gas and the active gas burns. The piston 116 reciprocates due to the expansion pressure due to the combustion of the fuel gas.

FIG. 2 is a diagram for explaining the arrangement of the fuel injection port 150. In FIG. 2, the cylinder jacket 114 shows a cross section cut by a plane (hereinafter, referred to as a vertical plane) perpendicular to the central axis of the cylinder 110 at a position including the through hole 114a. For the cylinder 110, a section cut in a vertical plane is shown at a position including the fuel injection port 150. Further, the outer shape of the fuel injection device 152 as viewed from the vertical upper side is shown.

As shown in FIG. 2, the two fuel injection ports 150 are arranged so as to sandwich the central axis O of the cylinder 110. Of the fuel injection port 150, the opening on the inner peripheral surface side of the cylinder 110 is an injection port 154 into which the fuel gas flows into the cylinder 110. Of the two injection ports 154, the injection port 154 located on the inflow port 146a side of the scavenging chamber 146 is referred to as the first injection port 154a, and the injection port 154 located on the side separated from the inflow port 146a is referred to as the second injection port 154b.

The first injection port 154a is located on the inflow port 146a side (on the right side in FIG. 2 from the broken line) with respect to the central axis O of the cylinder 110. The first injection port 154a is arranged so as to be displaced in the circumferential direction from the front surface of the inflow port 146a. The second injection port 154b is located on the side separated from the inflow port 146a with respect to the central axis O of the cylinder 110 (on the left side in FIG. 2 from the broken line).

FIG. 3 is a block diagram showing a control system of the uniflow scavenging two-stroke engine 100. FIG. 3 mainly shows a configuration related to control of the fuel injection device 152. As shown in FIG. 3, the uniflow scavenging two-stroke engine 100 includes a control device 200. The control device 200 is composed of, for example, an ECU (Engine Control Unit). The control device 200 is composed of a central processing unit (CPU), a ROM in which programs and the like are stored, a RAM as a work area, and the like, and controls the entire uniflow scavenging two-stroke engine 100. Further, the control device 200 functions as a fuel control unit 202 (control unit).

The fuel control unit 202 controls the fuel injection device 152 to control the injection amount and injection timing of the fuel gas. The crankshaft 126 is provided with a crank angle sensor 204, and the crank angle sensor 204 outputs a crank angle signal indicating the crank angle to the fuel control unit 202. The fuel control unit 202 controls the fuel injection device 152 so that the injection amount and injection timing of the fuel gas are determined according to the operating conditions based on the crank angle signal.

FIG. 4 is a first diagram for explaining the processing of the fuel control unit 202. The figure on the left side in FIG. 4 shows the fuel supply amount to the first injection port 154a, and the figure on the right side shows the fuel supply amount to the second injection port 154b. In the figure below, the threshold value M indicates a required output of 100%. In the range where the required output is larger than the threshold value A, the fuel supply amount increases or decreases in proportion to the increase or decrease in the required output at both the first injection port 154a and the second injection port 154b.

When the required output is equal to or less than the threshold value A, the fuel control unit 202 controls the fuel injection device 152 and stops the supply of fuel gas to the first injection port 154a.

Specifically, it is assumed that the required output decreases across the threshold value A. At this time, the fuel control unit 202 stops the supply of fuel gas to the first injection port 154a. Further, the fuel control unit 202 increases the fuel supply amount to the second injection port 154b by an amount smaller than the decrease amount (fuel supply amount Q) that is no longer supplied from the first injection port 154a. That is, the fuel supply amount Q'when the fuel gas is injected only from the second injection port 154b is smaller than the fuel supply amount 2Q when the fuel gas is injected from the two injection ports 154.

Further, the fuel control unit 202 may perform the processes shown in FIGS. 5, 6 and 7 instead of the above processes shown in FIG.

FIG. 5 is a second diagram for explaining the processing of the fuel control unit 202. The figure on the left side in FIG. 5 shows the fuel supply amount to the first injection port 154a, and the figure on the right side shows the fuel supply amount to the second injection port 154b. In the range where the required output is larger than the threshold value B, the fuel supply amount increases or decreases in proportion to the increase or decrease in the required output at both the first injection port 154a and the second injection port 154b. Here, the threshold value B is larger than the threshold value A.

When the required output is equal to or less than the threshold value A, the fuel control unit 202 controls the fuel injection device 152 and stops the supply of fuel gas to the first injection port 154a.

Specifically, it is assumed that the required output decreases across the threshold value B and the threshold value A. As the required output moves from the threshold value B to the threshold value A, the fuel control unit 202 reduces the supply of the fuel gas to the first injection port 154a, and makes the fuel supply amount 0 when the threshold value A is reached.

Further, as the required output moves from the threshold value B to the threshold value A, the fuel control unit 202 sends the fuel control unit 202 to the second injection port 154b by an amount smaller than the decrease (fuel supply amount Q) that is no longer supplied from the first injection port 154a. Increase the fuel supply of. That is, the fuel supply amount Q'when the fuel gas is injected only from the second injection port 154b is smaller than the fuel supply amount 2Q when the fuel gas is injected from the two injection ports 154.

FIG. 6 is a third diagram for explaining the processing of the fuel control unit 202. The figure on the left side in FIG. 6 shows the fuel supply amount to the first injection port 154a, and the figure on the right side shows the fuel supply amount to the second injection port 154b. In the range where the required output is larger than the threshold value B, the fuel supply amount increases or decreases in proportion to the increase or decrease in the required output at both the first injection port 154a and the second injection port 154b.

When the required output is equal to or less than the threshold value A', the fuel control unit 202 controls the fuel injection device 152 and stops the supply of fuel gas to the first injection port 154a. Here, the threshold value A'is smaller than, for example, the threshold value A.

Specifically, it is assumed that the required output decreases across the threshold value B and the threshold value A'. As the required output moves from the threshold value B to the threshold value A', the fuel control unit 202 reduces the supply of fuel gas to the first injection port 154a, and makes the fuel supply amount 0 when the threshold value A'is reached.

Further, as the required output goes from 0 to the threshold value A', the fuel control unit 202 increases the fuel supply amount to the second injection port 154b. At this time, the amount of fuel supplied to the second injection port 154b is smaller than that in the case where fuel is injected from both the first injection port 154a and the second injection port 154b. For example, when the required output is the threshold value A', the fuel supply amount Q'when the fuel gas is injected only from the second injection port 154b is the fuel supply amount when the fuel gas is injected from the two injection ports 154. Less than 2Q.

When the required output rises from the threshold value A', the fuel supply amount to the second injection port 154b increases to the fuel supply amount 2Q and becomes constant until the required output reaches the threshold value B.

FIG. 7 is a third diagram for explaining the processing of the fuel control unit 202. The figure on the left side in FIG. 7 shows the fuel supply amount to the first injection port 154a, and the figure on the right side shows the fuel supply amount to the second injection port 154b. In the range where the required output is larger than the threshold value B, the fuel supply amount increases or decreases in proportion to the increase or decrease in the required output at both the first injection port 154a and the second injection port 154b.

When the required output is equal to or less than the threshold value A ″, the fuel control unit 202 controls the fuel injection device 152 and stops the supply of fuel gas to the first injection port 154a. Here, the threshold value A ″ is smaller than, for example, the threshold value A ″.

Specifically, it is assumed that the required output decreases across the threshold value B and the threshold value A ″. As the required output moves from the threshold value B to the threshold value A ″, the fuel control unit 202 reduces the supply of fuel gas to the first injection port 154a, and when the threshold value A ″ is reached, the fuel supply amount becomes 0. Let me.

Further, as the required output goes from 0 to the threshold value A ″, the fuel control unit 202 increases the fuel supply amount to the second injection port 154b. At this time, the amount of fuel supplied to the second injection port 154b is smaller than that in the case where fuel is injected from both the first injection port 154a and the second injection port 154b. For example, when the required output is the threshold value A ″, the fuel supply amount Q ′ when the fuel gas is injected only from the second injection port 154b is the fuel supply when the fuel gas is injected from the two injection ports 154. Less than quantity 2Q.

The amount of fuel supplied to the second injection port 154b increases at a substantially constant rate until the required output changes from the threshold value A ″ to the threshold value B.

Further, the control of the fuel supply amount by the fuel control unit 202 may change linearly or curvilinearly with respect to the required output.

FIG. 8 is a diagram showing a simulation result of a diffusion state of fuel gas near the crown surface of the piston 116 in the combustion chamber 130. The figure on the left side in FIG. 8 shows a case where the fuel gas is supplied only from the first injection port 154a. The figure on the right side in FIG. 8 shows a case where the fuel gas is supplied only from the second injection port 154b. In each figure of FIG. 8, the horizontal axis represents the Kelvin temperature, and the vertical axis represents the excess air ratio λ.

In FIG. 8, a large proportion of plots with a small excess air ratio λ indicates that the fuel gas is not diffused and is locally accumulated. The fuel gas is not diffused when the fuel gas is injected only from the second injection port 154b than when the fuel gas is injected only from the first injection port 154a. When the load is low, it is more difficult for misfire to occur if the fuel gas does not diffuse and accumulates locally.

As described above, when the required output is the threshold value A or less, the fuel control unit 202 controls the fuel injection device 152 and stops the supply of the fuel gas to the first injection port 154a. Fuel gas is injected only from the second injection port 154b. The second injection port 154b side is farther from the inflow port 146a than the first injection port 154a side, and the flow velocity of the active gas is suppressed. Therefore, as described above, the fuel gas does not diffuse and accumulates locally, so that misfire is suppressed.

Further, when the fuel control unit 202 stops the supply of the fuel gas to the first injection port 154a during any of the processes shown in FIGS. 4 to 7, the fuel control unit 202 is more likely to inject the fuel gas from all the injection ports 154. Also, the injection timing may be retarded. When the injection timing is retarded, the mixing time of the fuel gas and the active gas becomes shorter. Therefore, it becomes more difficult for the fuel gas to diffuse, and misfire at a low load is further suppressed. Further, in any of the processes shown in FIGS. 5 to 7, when the amount of fuel gas supplied to the first injection port 154a is reduced from the amount of fuel supplied to the second injection port 154b, the first injection port is used. The injection timing of the second injection port 154b may be retarded from the injection timing of 154a. By delaying the injection timing of the second injection port 154b, which has a large amount of fuel supplied, it becomes more difficult for the fuel gas to diffuse.

FIG. 9 is a diagram for explaining a modified example. In FIG. 9, a portion vertically below the uniflow scavenging two-stroke engine 100A of the modified example is extracted and shown. As shown in FIG. 9, the uniflow scavenging two-stroke engine 100A is not provided with the fuel injection port 150. Instead, a fuel pipe 360 is located radially outside the scavenging port 148.

A plurality of fuel pipes 360 are arranged apart from each other in the circumferential direction. One fuel pipe 360 is arranged for each of the plurality of scavenging ports 148, for example. An injection port 354 is formed in the fuel pipe 360. A main pipe 364 is connected to the fuel pipe 360 via a fuel injection valve 362. A plurality of fuel injection valves 362 are arranged apart from each other in the circumferential direction. A plurality of fuel pipes 360 are connected to one fuel injection valve 362. When the fuel injection valve 362 is opened, fuel gas is injected from the injection ports 354 of the plurality of connected fuel pipes 360.

The injected fuel gas joins the flow of the active gas sucked into the scavenging port 148. The fuel gas is sucked into the cylinder 110 from the scavenging port 148 together with the active gas. The fuel gas goes to the combustion chamber 130 while being mixed with the active gas, and is burned in the combustion chamber 130 as in the above embodiment.

FIG. 10 is a diagram for explaining the arrangement of the fuel pipe 360. In FIG. 10, for the cylinder jacket 114, a cross section cut in a vertical plane is shown at a position including the through hole 114a. The outer shape of the fuel pipe 360 as seen from the vertical upper side is shown.

As shown in FIG. 10, the fuel pipe 360 is arranged so as to sandwich the central axis O of the cylinder 110. In FIG. 10, among the fuel pipes 360, the fuel pipe 360 located on the inflow port 146a side of the scavenging chamber 146 is shown in black. The injection port 354 of the fuel pipe 360 located on the inflow port 146a side is referred to as a first injection port 354a, and the injection port 354 of the fuel pipe 360 located on the side separated from the inflow port 146a is referred to as a second injection port 354b.

The first injection port 354a is located on the inflow port 146a side (on the right side in FIG. 10 from the broken line) with respect to the central axis O of the cylinder 110. The second injection port 354b is located on the side (left side in FIG. 10 from the broken line) separated from the inflow port 146a with respect to the central axis O of the cylinder 110.

In the modified example, the same control as in the above-described embodiment is performed. For example, when the required output is the threshold value A or less, the fuel control unit 202 controls the fuel injection device 152 and stops the supply of fuel gas to the first injection port 354a. Fuel gas is injected only from the second injection port 354b. The second injection port 354b side is farther from the inflow port 146a than the first injection port 354a side, and the flow velocity of the active gas is suppressed, so that the fuel gas does not diffuse and tends to accumulate locally. Therefore, misfire is suppressed.

Although one embodiment of the present disclosure has been described above with reference to the accompanying drawings, it goes without saying that the present disclosure is not limited to such an embodiment. It is clear to those skilled in the art that various modifications or modifications can be conceived within the scope of the claims, and it is understood that they also naturally belong to the technical scope of the present disclosure. Will be done.

For example, in the above-described modification, the case where the injection port 354 opens outside the scavenging port 148 in the radial direction of the cylinder 110 has been described. However, the injection port 354 may be opened inside the scavenging port 148.

Further, in the above-described embodiment and modification, the first injection port 154a, 354a is located on the inflow port 146a side with respect to the central axis O of the cylinder 110, and the second injection port 154b, 354b is the center of the cylinder 110. The case where the shaft O is located on the side separated from the inflow port 146a has been described. In this case, the flow velocity of the active gas is slow on the second injection port 154b and 354b side, the diffusion of the fuel gas is suppressed, and the effect of suppressing misfire is high. However, at least the second injection port 154b, 354b may be arranged at a distance from the inflow port 146a than the first injection port 154a, 354a. Here, the separation distance from the inflow port 146a may be a straight line distance or the path length of the flow path. Further, both the first injection port 154a, 354a and the second injection port 154b, 354b may be located on the inflow port 146a side with respect to the central axis O of the cylinder 110. Both the first injection port 154a, 354a, and the second injection port 154b, 354b may be located on the side separated from the inflow port 146a with respect to the central axis O of the cylinder 110.

Further, in the above-described embodiment and modification, when the fuel control unit 202 stops the supply of the fuel gas to the first injection ports 154a and 354a, the fuel gas is injected from all the injection ports 154 and 354. Also described the case of retarding the injection timing. However, such retard angle control is not an essential process.

Further, in the above-described embodiment and modification, when the required output decreases across the threshold value A, the fuel control unit 202 uses the second injection port 154a and 354a by an amount smaller than the decrease that is no longer supplied. The case where the amount of fuel supplied to the injection ports 154b and 354b is increased has been described. When the load is low, the fuel is injected only from the second injection port 154b and 354b, so that the diffusion of the fuel gas is suppressed as described above. Therefore, compared to the case where the fuel gas is also injected from the first injection ports 154a and 354a, combustion is maintained even if the total amount of the fuel gas supplied is small. Such control makes it possible to improve fuel efficiency. However, when the required output decreases across the threshold value A, the fuel control unit 202 supplies fuel to the second injection ports 154b and 354b in an amount equivalent to the decrease that is no longer supplied from the first injection ports 154a and 354a. The amount may be increased.

The present disclosure can be applied to a uniflow scavenging two-stroke engine.

100 Uniflow scavenging two-stroke engine 100A Uniflow scavenging two-stroke engine 110 Cylinder 146 Scavenging chamber 146a Inflow port 148 Scavenging port 152 Fuel injection device 154 Injection port 154a First injection port 154b Second injection port 202 Fuel control unit (control unit)
354 Injection port 354a First injection port 354b Second injection port A Threshold O Central axis

Claims (5)

The scavenging chamber where the inflow port was formed and
A cylinder with a scavenging port inside the scavenging chamber,
It opens on the inner peripheral surface of the cylinder, inside the scavenging port, or radially outside the cylinder from the scavenging port, and is separated from the first injection port and the inflow port from the first injection port. Multiple injection ports including the second injection port arranged in the cylinder,
A fuel injection device that supplies fuel gas to the injection port,
A control unit that controls the fuel injection device, stops the supply of fuel gas to the first injection port, and injects fuel gas from the second injection port when the required output is equal to or less than the threshold value.
Uniflow scavenging two-stroke engine equipped with. Claim that the first injection port is located on the inflow port side with respect to the central axis of the cylinder, and the second injection port is located on the side separated from the inflow port with respect to the central axis of the cylinder. The uniflow scavenging type two-stroke engine according to 1. The first or second aspect of the present invention, wherein when the control unit stops the supply of the fuel gas to the first injection port, the injection timing is retarded as compared with the case where the fuel gas is injected from all the injection ports. Uniflow scavenging 2-cycle engine. When the control unit reduces the amount of fuel gas supplied to the first injection port to be smaller than the amount of fuel gas supplied to the second injection port, the control unit is more than the injection timing of the first injection port. 2. The uniflow scavenging two-stroke engine according to any one of claims 1 to 3, which retards the injection timing of the injection port. When the required output decreases across the threshold value, the control unit stops the supply of fuel gas to the first injection port, and the amount is smaller than the decrease amount that is no longer supplied from the first injection port. The uniflow scavenging two-stroke engine according to any one of claims 1 to 4, which increases the amount of fuel supplied to the second injection port.

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