WO2020179141A1

WO2020179141A1 - Gas engine with turbocharger, and combustion method for same

Info

Publication number: WO2020179141A1
Application number: PCT/JP2019/045230
Authority: WO
Inventors: 雅人仲井; 洋輔野中
Original assignee: 川崎重工業株式会社
Priority date: 2019-03-04
Filing date: 2019-11-19
Publication date: 2020-09-10
Also published as: JP2020143577A; JP7376995B2; CN113544374B; CN113544374A

Abstract

This pilot ignition type gas engine with a turbocharger repeats a combustion cycle comprising an intake stroke for sucking a lean air-fuel mixture including gaseous fuel and air into a combustion chamber, a compression stroke for compressing the lean air-fuel mixture, an expansion stroke in which combustion gas generated through combustion of the lean air-fuel mixture expands, and an exhaust stroke for exhausting the combustion gas from the combustion chamber, wherein first injection for injecting liquid fuel into the combustion chamber is performed at a first timing in the compression stroke, and second injection for injecting liquid fuel into the combustion chamber begins at a second timing in the expansion stroke, in the second half of a combustion period in which the lean air-fuel mixture in the combustion chamber burns by propagation of a flame generated by the first injection.

Description

Gas engine with turbocharger and combustion method thereof

The present invention relates to a gas engine with a turbocharger and a combustion method thereof.

Conventionally, a gas engine with a turbocharger is known. A turbocharger utilizes the flow of exhaust gas from a gas engine to drive a compressor and increase the density of air drawn by the gas engine. A gas engine with a turbocharger of this type is disclosed in Patent Document 1, for example.

The gas engine with a turbocharger disclosed in Patent Document 1 includes a cylinder in which a piston is inserted and a pilot fuel injection valve that injects pilot fuel into the cylinder. The intake port of the cylinder is connected to the compressor of the supercharger via an intake pipe, and the exhaust port of the cylinder is connected to the exhaust turbine of the supercharger via an exhaust pipe. Gas fuel is supplied to the intake pipe, and a mixture of gas fuel and air is formed in the intake pipe. The pilot fuel injection valve is connected to a high pressure fuel pipe that stores pilot fuel whose pressure has been increased. In this gas engine, an air-fuel mixture is introduced into the cylinder when the piston descends, and the piston rises with the intake port and the exhaust port closed, and the air-fuel mixture is compressed. When the air-fuel mixture is compressed, pilot fuel is injected from the pilot fuel injection valve, the air-fuel mixture ignites and combustion occurs, the piston descends as the cylinder internal pressure rises, and the combustion gas is released from the cylinder due to the rise of the piston due to inertia. It is exhausted.

The gas engine of Patent Document 1 employs a direct injection micropilot ignition system in which a small amount of pilot fuel (for example, light oil) is directly injected into the cylinder. Then, in order to appropriately control the ignition timing of the air-fuel mixture and avoid abnormal combustion, the pilot fuel injection can control the pre-injection that assists the flame propagation combustion of the air-fuel mixture and the ignition timing of the air-fuel mixture. It is divided into injection and.

　In ships that navigate the oceans and rivers, there are some ships that use the above-mentioned turbocharged gas engine as the main engine. In the main engine of a ship, the amount of fuel supplied to the main engine is controlled so that the speed of the propulsion shaft connected to the propeller for propelling or the engine directly connected to the propeller is at a given target speed.

FIG. 7 is a graph showing the combustion characteristics of a general gas engine, where the horizontal axis shows the air-fuel ratio (excess air ratio) and the vertical axis shows the net mean effective pressure (BMEP). The net mean effective pressure can be an indicator of the engine output of a gas engine. In the combustion characteristics of a general gas engine, a knocking region exists in a region where the air-fuel ratio of the lean air-fuel mixture in the combustion chamber of the cylinder is low and the engine output is high, and a misfire region exists in a region where the air-fuel ratio is high and the engine output is high. Exists. In order to obtain high output in lean burn, the air-fuel ratio of the lean mixture in the combustion chamber is optimal within the range X (operating window) between the knocking region and the misfire region, that is, the thermal efficiency is high and NOx is emitted. The amount is controlled to be the minimum. In other words, in a gas engine during steady operation, the supply pressure is controlled for the gas fuel supply amount adjusted to maintain the target rotation speed so that the air-fuel ratio of the lean mixture falls between the knocking region and the misfire region. Will be done.

-The speed of the propeller for propelling a ship tends to change in a short period of time depending on the tidal current, waves, and the steering angle of the ship. In such a rapid load change, in a gas engine with a turbocharger, even if the gas fuel supply amount is increased, the supply pressure does not immediately increase due to the turbo lag, so the gas fuel supply amount is rapidly increased. Can't. Therefore, the fuel supply device for the propulsion internal combustion engine (gas engine) of Patent Document 2 obtains the predicted fuel supply amount based on the predicted torque calculated based on the future predicted ship speed of the ship, and obtains the predicted fuel supply amount to obtain the predicted fuel supply amount. Based on this, the pressure of the air-fuel mixture supplied to the engine is controlled.

Japanese Patent No. 5922830 JP, 2016-205270, A

The technique of Patent Document 2 predicts a sudden increase in the load of the gas engine and raises the supply pressure in advance in preparation for it, and is not a technique that increases the supply pressure quickly. Further, it is known that the supercharger is jet-assisted in order to rapidly increase the air supply pressure. In this case, the supercharger needs to be equipped with a jet assist device.

In view of the above, the present invention provides a technique for rapidly increasing the supply air pressure in a gas engine with a turbocharger so that the gas fuel supply amount can be rapidly increased in response to a sudden increase in engine load. The purpose.

A combustion method for a gas engine according to one aspect of the present invention is generated by an intake stroke for sucking a lean air-fuel mixture including gas fuel and air into a combustion chamber, a compression stroke for compressing the lean air-fuel mixture, and a combustion of the lean air-fuel mixture. A combustion method of a gas engine with a turbocharger of a pilot ignition system, wherein an expansion stroke in which combustion gas expands, and a combustion cycle consisting of an exhaust stroke in which the combustion gas is exhausted from the combustion chamber is repeated.
At a first timing in the compression stroke, a first injection for injecting liquid fuel into the combustion chamber is performed,
The liquid fuel is injected into the combustion chamber at the second timing in the expansion stroke, which is the latter half of the combustion period in which the lean air-fuel mixture in the combustion chamber is burning due to the propagation of the flame generated by the first injection. The second injection is started.

Further, the gas engine with a turbocharger according to one aspect of the present invention is
The combustion chamber includes a cylinder and a piston that form a combustion chamber, and an injector that injects liquid fuel into the combustion chamber, and the piston reciprocates in the cylinder to generate a lean mixture of air and gas fuel. A combustion cycle including an intake stroke for sucking in the air, a compression stroke for compressing the lean air-fuel mixture, an expansion stroke for expanding combustion gas generated by combustion of the lean air-fuel mixture, and an exhaust stroke for exhausting the combustion gas from the combustion chamber. Is a pilot ignition type gas engine with turbocharger,
The injector performs the first injection at the first timing in the compression stroke, and is in the latter half of the combustion period in which the lean air-fuel mixture in the combustion chamber is burned by the propagation of the flame generated by the first injection. The second injection is started at the second timing in the expansion stroke.

According to the above turbocharged gas engine and its combustion method, the liquid fuel injected in the second injection is not substantially used for the work of pushing down the piston, but raises the exhaust temperature by combustion. As a result, the temperature of the combustion gas sent to the turbine of the turbocharger becomes higher than that in the case where the second injection is not performed, and more energy can be given to the turbine. As a result, when the operation in which the second injection is not performed is switched to the operation in which the second injection is performed, the supply pressure can be rapidly increased, and the supply amount of the gas fuel can be rapidly increased. .. Such a combustion method is suitable as a combustion method when the load of a gas engine with a turbocharger suddenly rises, and can improve the load response of the gas engine (that is, the followability of the actual output with respect to the required output). ..

In the above turbocharged gas engine and its combustion method, the gas engine may be a four-stroke engine, and the second timing may be in the range of 60° to 180° ATDC.

With this, the temperature of the combustion gas discharged from the combustion chamber can be raised by the additional pilot fuel from the second injection without hindering the normal combustion of the lean air-fuel mixture in the combustion chamber.

In the above turbocharged gas engine and its combustion method, when increasing the engine output from a first output value to a second output value to a third output value, from the first output value to the second output value The injection amount of the liquid fuel in the first injection may be changed so that the output increase rate is higher than the output increase rate from the second output value to the third output value.

In this way, by lowering the air-fuel ratio at a relatively low load to make the fuel rich, it is possible to quickly increase the number of revolutions while avoiding abnormal combustion. By reducing the air-fuel ratio of the lean air-fuel mixture at a relatively high load while maintaining the momentum of the rotation speed increase, it is possible to quickly increase the engine output while avoiding abnormal combustion. Therefore, the load response of the gas engine with a turbocharger can be improved.

According to the present invention, in a gas engine with a turbocharger, it is possible to provide a technique for rapidly increasing the supply air pressure so that the gas fuel supply amount can be rapidly increased in response to a sudden increase in engine load.

FIG. 1 is a schematic configuration diagram of a gas engine with a turbocharger according to an embodiment of the present invention. FIG. 2 is a sectional view showing a structure of one of a plurality of cylinders included in the engine. FIG. 3 is a schematic configuration diagram of the air cooler. FIG. 4 is a diagram showing a configuration of a control system of a gas engine with a turbocharger. FIG. 5 is a timing chart of pilot fuel injection in a sudden load increase operation. FIG. 6 is a chart showing time-series changes in the target engine output and the pilot fuel injection amount when the engine output is increased in response to a sudden increase in engine load. FIG. 7 is a graph showing the combustion characteristics of a general gas engine.

Next, an embodiment of the present invention will be described with reference to the drawings. The gas engine 1 with a turbocharger according to the present embodiment is mounted on a ship as a main engine. However, the gas engine 1 with a turbocharger according to the present invention is not limited to the one mounted on a ship.

[Configuration of gas engine 1 with turbocharger]
FIG. 1 is a schematic configuration diagram of a gas engine 1 with a turbocharger according to an embodiment of the present invention. The gas engine 1 with a turbocharger shown in FIG. 1 includes an engine (engine body) 2, a supercharger 3, an air cooler 43, and a control device 7 (see FIG. 2). In the present embodiment, the gas engine 1 with a turbocharger drives the propulsion shaft 93 to which the propulsion blades 83 are attached.

The engine 2 according to this embodiment is a 4-stroke multi-cylinder gas combustion engine. However, the engine 2 is not limited to the gas-only combustion engine, and may be a dual fuel engine that burns one or both of the gas fuel and the liquid fuel depending on the situation.

FIG. 2 is a cross-sectional view showing the structure of one of the plurality of cylinders 21 included in the engine 2. A piston 22 is reciprocally arranged in the cylinder 21, and a combustion chamber 20 is formed by the cylinder 21 and the piston 22.

The intake port of the cylinder 21 is connected to the air supply pipe 41. An intake valve 23 that opens and closes the intake port is provided in the intake port. The exhaust port of the cylinder 21 is connected to the exhaust pipe 42. The exhaust port is provided with an exhaust valve 24 that opens and closes the exhaust port. The combustion chamber 20 is provided with an in-cylinder pressure sensor 62 that detects the in-cylinder pressure, which is the pressure inside the combustion chamber 20.

The piston 22 is connected to a crankshaft (not shown) by a connecting rod (not shown). The piston 22 reciprocates twice in the cylinder 21 to perform one combustion cycle consisting of intake, compression, expansion, and exhaust. The phase angle of the engine 2 during one combustion cycle in each cylinder 21 is detected by the phase angle detector 63. As the phase angle, the rotation angle (crank angle) of the crankshaft, the position of the piston 22, and the like may be used, and the phase angle detector 63 may be, for example, an electromagnetic pickup, a proximity switch, or a rotary encoder. The phase angle detector 63 also functions as an actual rotation speed detector that detects the actual rotation speed of the engine 2.

Returning to FIG. 1, the supercharger 3 includes a compressor 31 and a turbine 32, which are connected by a shaft. The combustion chamber 20 in the cylinder 21 is connected to the compressor 31 via the air supply pipe 41 and is connected to the turbine 32 via the exhaust pipe 42. The air supply pipe 41 guides the air compressed by the compressor 31 to the combustion chamber 20 of each cylinder 21. The air supply pipe 41 is provided with an air supply blow-off valve 48 that releases gas from the air supply pipe 41 to release the pressure of the air supply pipe 41. The exhaust pipe 42 guides exhaust gas (combustion gas) from the combustion chamber 20 of each cylinder 21 to the turbine 32. The exhaust pipe 42 is provided with an exhaust wastegate valve 49 that regulates the amount of gas flowing into the turbine 32 by dividing a part of the gas from the exhaust pipe 42. The downstream portion of the air supply pipe 41 and the upstream portion of the exhaust pipe 42 are branched from the manifold into the same number of branch paths as the cylinder 21, but in FIG. 1, the air supply pipe 41 and the exhaust pipe are branched to simplify the drawing. 42 is drawn with one flow path.

The air supply pipe 41 is provided with an air cooler 43 for cooling the air compressed by the compressor 31 and having a high temperature (air supply). As shown in FIG. 3, the air cooler 43 is a heat exchanger that exchanges heat between a refrigerant such as water flowing through the refrigerant flow path 44 and the air flowing through the air supply pipe 41. A bypass passage 46 is connected to the refrigerant passage 44 so as to flow the refrigerant to the downstream side of the air cooler 43 without passing through the air cooler 43 (that is, not used for heat exchange in the air cooler 43). Further, the refrigerant flow path 44 is provided with a flow rate adjusting device 45 that adjusts the flow rate of the refrigerant flowing through the bypass path 46, in other words, the flow rate of the refrigerant used for heat exchange in the air cooler 43. The flow rate adjusting device 45 adjusts the flow rate of the refrigerant used for heat exchange in the air cooler 43 so that the cooled air discharged from the air cooler 43 reaches a predetermined temperature.

A supply air pressure sensor 61 and a supply air temperature sensor 65 are provided downstream of the air cooler 43 of the supply air pipe 41. The air supply pressure sensor 61 detects the air supply pressure, which is the discharge pressure of the compressor 31. The air supply pressure sensor 61 may be provided in each of the above-mentioned branch paths on the downstream side of the air supply pipe 41, or may be provided in only one in the above-mentioned manifold. The supply air temperature sensor 65 detects the supply air temperature which is the temperature of the air introduced into the combustion chamber 20 through the supply air pipe 41. Similarly, the supply air temperature sensor 65 may be provided in each of the above-mentioned branch paths on the downstream side of the supply pipe 41, or may be provided in only one in the above-mentioned manifold.

Further, the air supply pipe 41 is provided with a gas fuel supply valve 51 for each cylinder 21. The gas fuel supply valve 51 supplies gas fuel into the air discharged from the compressor 31. The opening degree (or opening time) of the gas fuel supply valve 51 is operated by the gas fuel supply valve driver 50. The supply amount of the gas fuel supplied from the gas fuel chamber (not shown) to the air supply pipe 41 through the gas fuel supply valve 51 changes depending on the opening degree (or opening time) of the gas fuel supply valve 51. The gas fuel supply valve driver 50 and the gas fuel supply valve 51 constitute a gas fuel supply amount adjusting device.

The engine 2 according to the present embodiment employs a direct injection pilot fuel ignition method and includes a pilot fuel injector 52 that ejects pilot fuel into the combustion chamber 20. The pilot fuel is, for example, a liquid fuel such as light oil. The pilot fuel injector 52 is connected to the common rail 53 via a fuel pipe. A high-pressure pilot fuel is stored in the common rail 53, and the pilot fuel injector 52 of each cylinder 21 can inject this pilot fuel at an arbitrary timing and an arbitrary injection pressure. The injection from the pilot fuel injector 52 is operated by the injector driver 54. The injector driver 54 and the pilot fuel injector 52 constitute a pilot fuel injection amount adjusting device.

[Structure of control system of gas engine 1 with turbocharger]
Hereinafter, the configuration of the control system of the gas engine 1 with a turbocharger will be described. FIG. 4 is a diagram showing a configuration of a control system of the gas engine 1 with the turbocharger. The control device 7 is a so-called computer, and has an arithmetic processing unit 7a such as a CPU and a storage unit 7b such as a ROM and RAM. The storage unit 7b stores programs executed by the arithmetic processing unit 7a, various fixed data, and the like. The arithmetic processing unit 7a transmits / receives data to / from an external device. In addition, the arithmetic processing unit 7a inputs detection signals from various sensors and outputs control signals to each control target. The control device 7 performs processing as each functional unit by the arithmetic processing unit 7a reading and executing software such as a program stored in the storage unit 7b. The control device 7 may execute each process by centralized control by a single computer, or may execute each process by distributed control by cooperation of a plurality of computers. Further, the control device 7 may be composed of a microcontroller, a programmable logic controller (PLC), or the like.

The control device 7 is electrically connected to the rudder angle operation tool 73, the marine vessel manipulating operation tool 74, the turning angle sensor 66, and the speedometer 67.

A cockpit (not shown) provided on the hull is provided with a steering angle operating tool 73 for operating and inputting a steering angle, and a ship maneuvering operating tool 74 for operating and inputting the rotation speed of the engine 2 and forward / backward movement. .. The steering angle operation information input by the operator is input to the control device 7 via the steering angle operating tool 73. The ship maneuvering operation information input by the operator is input to the control device 7 via the ship maneuvering operation tool 74. These

operation tools

73 and 74 may be handles or levers, for example. Further, the hull is provided with a turning angle sensor 66 for detecting the turning angle of the hull and a speedometer 67 for detecting the ship speed.

The control device 7 determines a sudden rise in engine load or predicts a sudden rise in engine load. A sudden increase in engine load means an increase in load such that turbo lag occurs (that is, the supercharger 3 does not supercharge sufficiently and a delay time occurs before reaching the required supercharging pressure). To say. Causes of a sudden increase in load include, for example, an increase in ship speed, a change in rudder angle, a strong wind wave received by the hull, a change in propeller pitch, and a change in turning angle when the ship is equipped with an azimuth thruster.

The control device 7 can determine that the load on the engine 2 has rapidly increased by the following method. For example, the rate of increase in gas fuel supply is calculated, and if the rate of increase in gas fuel supply exceeds the threshold, it is determined that the load has increased sharply, and if the rate of increase in gas fuel supply is below the threshold, the load is rapid. It is determined that it has not risen. For example, the deviation between the actual rotation speed and the target rotation speed is calculated, and if the deviation between the actual rotation speed and the target rotation speed exceeds the threshold value, it is determined that the load has increased sharply, and the actual rotation speed and the target rotation speed are If the deviation is below the threshold, it is determined that the load has not risen sharply. Further, for example, the output torque of the engine 2 is detected by a torque meter (not shown), the rising speed of the output torque is calculated, and if the rising speed of the output torque exceeds the threshold value, it is determined that the load has risen sharply, and the output torque is determined. If the speed of increase is below the threshold value, it is determined that the load has not increased rapidly.

Further, the control device 7 is based on the rudder angle operation information, the ship maneuvering operation information, the hull turning angle, the rotation speed of the gas engine 1, the ship speed, and the hull performance model stored in advance in the storage unit 7b. A sudden increase in engine load can be predicted in advance. For example, when the rudder angle of the hull is manipulated by the rudder angle control tool 73, a sharp increase in engine load is expected in the near future. For example, when the ship maneuvering tool 74 is switched from forward to reverse, a sharp increase in engine load is expected in the near future.

The control device 7 includes a gas fuel supply valve driver 50, an injector driver 54, an air supply pressure sensor 61, an in-cylinder pressure sensor 62, a phase angle detector 63, an air supply temperature sensor 65, an air supply blow-off valve 48, and an exhaust waist. It is electrically connected to the gate valve 49. The control device 7 operates the gas fuel supply valve driver 50 and the injector driver 54 for each cylinder 21 based on the phase angle detected by the phase angle detector 63 so that the actual rotation speed becomes the target rotation speed. , Control the supply amount and supply timing of gas fuel and pilot fuel. Further, the control device 7 operates the air supply blow-off valve 48 and the exhaust waistgate valve 49 based on the air pressure detected by the air supply pressure sensor 61, and operates the gas fuel supply amount in the combustion chamber 20. In the range X where the air-fuel ratio of the lean mixture is in the range X shown in FIG. 7, the combustion pressure is optimized, that is, the thermal efficiency is high and the NOx emission amount is controlled to be minimum.

The control device 7 performs steady operation while the engine load hardly changes, and shifts to load rapid increase operation when a sudden increase in engine load is predicted or a sudden increase in engine load is detected during steady operation. Hereinafter, the combustion method of the gas engine 1 during the sudden load increase operation will be described.

In the intake stroke of the combustion cycle, the piston 22 is lowered with the exhaust valve 24 closed and the intake valve 23 open, and the gas fuel injected from the gas fuel supply valve 51 and the air supplied from the supercharger 3 are diluted. The air-fuel mixture is sucked into the combustion chamber 20 through the intake port. In the compression stroke, the piston 22 rises to the top dead center with the intake valve 23 and the exhaust valve 24 closed, and the lean air-fuel mixture in the combustion chamber 20 is compressed. At the timing before the piston 22 reaches top dead center, the pilot fuel is directly injected into the compressed dilute mixture of the combustion chamber 20, and the pilot fuel self-ignites. This flame propagates to the lean air-fuel mixture in the combustion chamber 20, and the air-fuel mixture burns. In the expansion stroke (combustion stroke), the ignited lean air-fuel mixture burns, the combustion gas expands, and the piston 22 is pushed down to the bottom dead center. In the exhaust stroke, the piston 22 rises due to inertia while the intake valve 23 is closed and the exhaust valve 24 is opened, and combustion gas is pushed out to the exhaust pipe 42 through the exhaust port. The combustion gas is introduced into the turbine 32 through the exhaust pipe 42 and used as power to drive the compressor 31.

When the load sudden rise operation is started, the control device 7 operates the flow rate adjusting device 45 so that all the refrigerant flowing in the refrigerant flow path 44 passes through the air cooler 43, referring to FIG. That is, the flow rate adjusting device 45 blocks the flow of the refrigerant in the bypass passage 46. As a result, the supply air temperature can be rapidly lowered by the total cooling capacity of the air cooler 43.

In normal combustion of the engine 2 of the premixed combustion method, the ignited flame propagates in the unburned air-fuel mixture in sequence to complete the combustion. However, when the heat load and the combustion pressure in the combustion chamber 20 increase due to an increase in load or the like, the air-fuel mixture in the unburned portion causes self-ignition without waiting for flame propagation. If this self-ignition occurs in a chain, a strong pressure rise and temperature rise will occur. This is the "knocking" phenomenon. As described above, by lowering the supply air temperature, the heat load in the combustion chamber 20 can be suppressed, and the occurrence of knocking (abnormal combustion) can be suppressed.

FIG. 5 is a timing chart of pilot fuel injection in a sudden load increase operation. In this timing chart, the vertical axis represents the pilot fuel injection amount and the in-cylinder pressure, and the horizontal axis represents the phase angle [ATDC: After Top Dead Center] of the piston 22. As shown in this timing chart, the pilot fuel injector 52 controlled by the control device 7 has at least one first injection (main injection) and at least one second injection (post injection) in one combustion cycle. ) And. The control device 7 measures the injection timing based on the phase angle detected by the phase angle detector 63.

The first injection is performed at a predetermined first timing Ta before the top dead center (TDC) in the compression stroke. More specifically, the pilot fuel injector 52 is opened by the injector driver 54 at the first timing Ta, and a small amount of pilot fuel (around 1% of the total heat input at the rated load) is contained in the lean air-fuel mixture in the combustion chamber 20. Squirt into. The first timing Ta may be in the range of −30° to 0° ATDC.

The high-pressure pilot fuel injected into the combustion chamber 20 in the first injection ignites the lean air-fuel mixture in the combustion chamber 20. That is, the first injection determines the start timing of the combustion period. The combustion pressure of the lean air-fuel mixture in the combustion chamber 20 provides the output of the engine 2.

When the piston 22 exceeds top dead center (TDC), the compression stroke shifts to the expansion stroke. The second injection is performed at a predetermined second timing Tb in the latter half of the combustion period in the expansion stroke. More specifically, the pilot fuel injector 52 is opened by the injector driver 54 at the second timing Tb, and the pilot fuel is ejected into the combustion chamber 20. The latter half of the combustion period means that the lean air-fuel mixture in the combustion chamber 20 is burning and after the time Tc at which the in-cylinder pressure reaches the maximum in-cylinder pressure.

The temperature of the combustion gas in the cylinder rises due to the combustion of the pilot fuel injected in the second injection. Further, the pilot fuel injected in the second injection burns the unburned gas fuel in the combustion gas in the combustion chamber 20 and the exhaust pipe 42 in the expansion stroke and the subsequent exhaust stroke. As a result, the temperature of the combustion gas sent to the turbine 32 of the supercharger 3 becomes higher than that in the case where the second injection is not performed, and more energy can be given to the turbine 32. Therefore, the rotation speed of the turbine 32 can be increased as compared with the case where the second injection is not performed, and the supercharging pressure by the supercharger 3 can be rapidly increased. As a result, it is possible to eliminate or shorten the turbo lag when the engine load rapidly increases.

When the first timing Ta, that is, the start timing of the combustion period is in the range of -30 ° to 0 ° ATDC, the second injection is started before the time point Tc when the in-cylinder pressure reaches the maximum in-cylinder pressure. Then, the maximum in-cylinder pressure may increase and abnormal combustion may occur. On the other hand, if the second injection is started after 180 ° ATDC, the fuel supplied by the second injection may not be combusted. From this point of view, the second timing Tb, that is, the start timing of the second injection may be in the range of 60 ° to 180 ° ATDC. The end timing of the second injection may be determined by the injection capacity of the pilot fuel injector 52.

Also, the injection amount of the second injection is larger than the injection amount of the first injection. The ratio of the injection amount of the second injection to the injection amount of the first injection is larger than 1 and 15 or less, preferably 8 or more and 12 or less. If the ratio is 1 or less, the increase in the exhaust temperature becomes insufficient, and the effect of rapidly increasing the rotation speed of the turbine 32 cannot be obtained. On the other hand, when the ratio is 15 or more, the exhaust temperature rises excessively, and the exhaust temperature may exceed the allowable temperature of the member.

It is known that abnormal combustion such as knocking is unlikely to occur in the range of relatively low engine load, and abnormal combustion is likely to occur in the range of relatively high engine load. Therefore, when the engine load is rapidly increased from a relatively low load, it is desirable to set the rate of change of the engine output in two stages.

FIG. 6 shows when the engine output is increased from the relatively low output first output value Da to the relatively high output third output value Dc via the second output value Db in response to the sudden increase in engine load. 4 is a chart showing a time series change of a target engine output and a pilot fuel injection amount. The second output value Db is an engine output value corresponding to a boundary value between a relatively low load range in which abnormal combustion is unlikely to occur and a relatively high load in which abnormal combustion is likely to occur. In the figure, a change in engine output when the engine output is increased at a constant rate of change in response to an increase in engine load is shown by a fixed rate of change output line L0. Here, the output change rate of the fixed change rate output line L0 is the maximum output change rate at which knocking does not occur even under high load.

In the target output line L of the present invention, the output change rate when the engine output is increased from the first output value Da to the second output value Db is larger than the output change rate of the fixed change rate output line L0 (that is, the tangent line). Has a large inclination). Further, in the target output line L, the output change rate when the engine output is increased from the second output value Db to the third output value Dc is smaller than the output change rate of the fixed change rate output line L0 (that is, the tangent line). The inclination is small) or the same. As a result, in the target output line L, the output can be quickly increased to the third output value Dc as compared with the fixed change rate output line L0.

The target output line L is stored in the control device 7 in advance. When the engine output is rapidly increased from the first output value Da to the third output value Dc, the control device 7 supplies the gas fuel supplied from the gas fuel supply valve 51 along the target output line L and the pilot. The amount of pilot fuel injected from the fuel injector 52 in the first injection is changed.

When the engine output is increased from the first output value Da to the second output value Db, the control device 7 increases the supply amount of gas fuel so as to increase the engine output along the target output line L. , The pilot fuel injection amount is gradually increased from the injection amount Fa to the injection amount Fb. When the engine output is increased by the conventional combustion method, the supply amount of gas fuel is increased, but the injection amount of the pilot fuel is constant at the injection amount Fa. The injection amount Fa and the injection amount Fb are set according to the gas engine 1 and are stored in advance in the control device 7.

When increasing the engine output from the second output value Db to the third output value Dc, the control device 7 increases the supply amount of gas fuel so as to increase the engine output along the target output line L. , Maintain the injection amount of pilot fuel at the injection amount Fb. That is, the injection amount of pilot fuel is maintained in an increased state. When the engine output reaches the third output value Dc, the control device 7 gradually reduces the injection amount of the pilot fuel from the injection amount Fb to the injection amount Fa.

When the engine load suddenly rises from a relatively low load as described above, the combustion chamber 20 responds to a change in engine output by increasing the injection amount of pilot fuel in the first injection along the target output line L. The air-fuel ratio inside changes on the curve Y in FIG. 7. Specifically, in the range where the engine output is low (that is, the range where the engine load is small), the air-fuel ratio is reduced to a range where knocking does not occur, and the fuel is rich. In the range where the engine output is high (that is, the range where the engine load is large), the air-fuel ratio increases to the range where misfire does not occur.

As described above, the gas engine 1 with a turbo supercharger of the present embodiment is a gas engine with a turbo supercharger of a pilot ignition type, and the cylinder 21 and the piston 22 forming the combustion chamber 20 and combustion. An intake stroke in which an injector 52 for injecting liquid fuel (pilot fuel) is provided in the chamber 20 and a lean air-fuel mixture composed of air and gas fuel is sucked into the combustion chamber 20 by reciprocating the piston 22 in the cylinder 21. A combustion cycle consisting of a compression stroke for compressing the lean air-fuel mixture, an expansion stroke for expanding the combustion gas generated by combustion of the lean air-fuel mixture, and an exhaust stroke for exhausting the combustion gas from the combustion chamber is repeated. Then, the injector 52 performs the first injection at the first timing Ta in the compression stroke, and the second half of the combustion period in which the lean air-fuel mixture in the combustion chamber 20 is burned by the propagation of the flame generated by the first injection. It is characterized in that the second injection is started at the second timing Tb in the expansion stroke.

Similarly, in the combustion method of the gas engine 1 with a turbocharger according to the present embodiment, the first injection of liquid fuel into the combustion chamber 20 is performed at the first timing Ta in the compression stroke, and the first injection is performed. In the latter half of the combustion period in which the lean air-fuel mixture in the combustion chamber 20 is burning due to the propagation of the generated flame, at the second timing Tb in the expansion stroke, the second injection for injecting the liquid fuel into the combustion chamber 20 is started. It is characterized by doing.

According to the gas engine 1 with a turbocharger and its combustion method, the pilot fuel (liquid fuel) injected in the second injection is not substantially used for the work of pushing down the piston 22, but is exhausted by combustion. Raise the temperature. As a result, the temperature of the combustion gas sent to the turbine 32 of the supercharger 3 becomes higher than that in the case where the second injection is not performed, and more energy can be given to the turbine 32. As a result, when the operation in which the second injection is not performed is switched to the operation in which the second injection is performed, the supply air pressure sensor 61 can be quickly increased, and the supply amount of the gas fuel can be rapidly increased. it can. Such a combustion method is suitable as a combustion method when the load of the gas engine 1 with a turbocharger suddenly rises, and improves the load responsiveness of the gas engine 1 (that is, the followability of the actual output with respect to the required output). Can be done.

Further, in the gas engine 1 with a turbocharger and the combustion method thereof according to the present embodiment, the gas engine 1 is a 4-stroke engine, and the second timing Tb is in the range of 60 ° to 180 ° ATDC.

Thereby, the temperature of the combustion gas discharged from the combustion chamber 20 by the additional pilot fuel by the second injection can be raised without interfering with the normal combustion of the lean air-fuel mixture in the combustion chamber 20.

Further, in the gas engine 1 with a turbocharger and its combustion method according to the present embodiment, the injection amount of the second injection is larger than the injection amount of the first injection.

Further, in the gas engine 1 with a turbocharger and the combustion method thereof according to the present embodiment, when the engine output is increased from the first output value Da to the third output value Dc via the second output value Db, the first Injection of liquid fuel in the first injection so that the output increase rate from the first output value Da to the second output value Db is larger than the output increase rate from the second output value Db to the third output value Dc. Change the amount.

That is, the pilot ignition type gas engine 1 with a turbocharger includes a cylinder 21 and a piston 22 forming a combustion chamber 20, and an injector 52 for injecting pilot fuel (liquid fuel) into the combustion chamber 20. When the engine output is raised from the first output value Da to the third output value Dc via the second output value Db, 52 performs main injection in a compression stroke for compressing the lean air-fuel mixture sucked into the combustion chamber 20. The injection of pilot fuel in the main injection is performed so that the output increase rate from the first output value Da to the second output value Db is greater than the output increase rate from the second output value Db to the third output value Dc. Change the amount.

In this way, by lowering the air-fuel ratio at a relatively low load to make the fuel rich, it is possible to quickly increase the number of revolutions while avoiding abnormal combustion. Then, while maintaining the momentum of this increase in the number of revolutions, by lowering the air-fuel ratio of the lean air-fuel mixture at a relatively high load, it is possible to quickly increase the engine output while avoiding abnormal combustion. Therefore, the load response of the gas engine 1 with a turbocharger can be improved.

The gas engine 1 with a turbocharger according to this embodiment further includes an air cooler 43 that cools the air sucked into the combustion chamber 20. The air cooler 43 connects the refrigerant flow path 44 through which the refrigerant flows, the bypass passage 46 which is connected to the refrigerant flow path 44 and allows the refrigerant to flow to the downstream side of the refrigerant flow path 44 without heat exchange with air, and the refrigerant flow path 44. It has a flow rate adjusting device 45 that adjusts the flow rate of the refrigerant flowing into the bypass path 46 among the flowing refrigerants, and the flow rate adjusting device 45 blocks the flow of the refrigerant from the refrigerant flow path 44 to the bypass path when the engine load rises. To do.

That is, the gas engine 1 with a turbocharger has an engine 2 that obtains power by burning a dilute mixture of gas fuel and air, a compressor 31 that is connected to the engine 2 by an air supply pipe 41, and an exhaust pipe. A supercharger 3 having a turbocharger 32 connected to an engine 2 by 42, a gas fuel supply device (gas fuel supply valve 51 and a gas fuel supply valve driver 50) for supplying gas fuel to an air supply pipe 41, and an air supply pipe 41. And an air cooler 43 that cools the air passing therethrough. The air cooler 43 is connected to the refrigerant flow path 44 through which the refrigerant flows, the refrigerant flow path 44, and has a bypass path 46 that allows the refrigerant to flow to the downstream side of the refrigerant flow path 44 without heat exchange with air, and a refrigerant flow path 44. The flow rate adjusting device 45 has a flow rate adjusting device 45 that adjusts the flow rate of the refrigerant flowing into the bypass passage 46 among the flowing refrigerant. To do.

In this way, when the engine load rises, the heat load in the combustion chamber 20 is suppressed by cooling the supply air to the engine 2 with the full cooling capacity of the air cooler 43, and the occurrence of knocking (abnormal combustion) is suppressed. be able to.

Although the preferred embodiment of the present invention has been described above, the present invention may include modified details of the specific structure and / or function of the above embodiment without departing from the idea of the present invention. ..

For example, the engine 2 of the gas engine with a turbocharger according to the above embodiment is a 4-stroke engine, but it may be a 2-stroke engine. In the two-stroke engine, exhaust, intake, and compression are performed in the upward stroke of the piston 22, and combustion and exhaust are performed in the downward stroke of the piston 22.

1: Gas engine with turbocharger 2: Engine (engine body)
3: supercharger 7: control device 7a: arithmetic processing unit 7b: storage unit 20: combustion chamber 21: cylinder 22: piston 23: intake valve 24: exhaust valve 31: compressor 32: turbine 41: air supply pipe 42: exhaust gas Pipe 43: Air cooler 44: Refrigerant flow passage 45: Flow rate adjusting device 46: Bypass passage 48: Air supply blow-off valve 49: Exhaust waste gate valve 50: Gas fuel supply valve driver 51: Gas fuel supply valve 52: Pilot fuel injector 53: Common rail 54: Injector driver 61: Air supply pressure sensor 62: In-cylinder pressure sensor 63: Phase angle detector 65: Air supply temperature sensor 66: Turning angle sensor 67: Vessel speed gauge 73: Rudder angle operation tool 74: Ship operation tool 83: Propulsion wing 93: Propulsion shaft

Claims

An intake stroke for sucking a lean air-fuel mixture containing gas fuel and air into a combustion chamber, a compression stroke for compressing the lean air-fuel mixture, an expansion stroke for expanding the combustion gas generated by the combustion of the lean air-fuel mixture, and the combustion gas. It is a combustion method of a gas engine with a turbo supercharger of a pilot ignition system, which repeats a combustion cycle consisting of an exhaust stroke from the combustion chamber.
At a first timing in the compression stroke, a first injection for injecting liquid fuel into the combustion chamber is performed,
The liquid fuel is injected into the combustion chamber at the second timing in the expansion stroke, which is the latter half of the combustion period in which the lean air-fuel mixture in the combustion chamber is burning due to the propagation of the flame generated by the first injection. Start the second injection,
Gas engine combustion method.
The gas engine is a 4-stroke engine, and the second timing is in the range of 60 ° to 180 ° ATDC.
The combustion method for a gas engine according to claim 1.
The injection amount of the second injection is larger than the injection amount of the first injection.
The combustion method for a gas engine according to claim 1.
When increasing the engine output from the first output value to the third output value via the second output value, the output increase rate from the first output value to the second output value is from the second output value to the second output value. 3 The injection amount of the liquid fuel in the first injection is changed so as to be larger than the output increase rate up to the output value.
The method for burning a gas engine according to any one of claims 1 to 3.
The combustion chamber includes a cylinder and a piston that form a combustion chamber, and an injector that injects liquid fuel into the combustion chamber, and the piston reciprocates in the cylinder to generate a lean mixture of air and gas fuel. A combustion cycle including an intake stroke for sucking in the air, a compression stroke for compressing the lean air-fuel mixture, an expansion stroke for expanding combustion gas generated by combustion of the lean air-fuel mixture, and an exhaust stroke for exhausting the combustion gas from the combustion chamber. Is a gas engine with a pilot ignition type turbo supercharger that repeats
The injector performs the first injection at the first timing in the compression stroke, and is in the latter half of the combustion period in which the lean air-fuel mixture in the combustion chamber is burned by the propagation of the flame generated by the first injection. The second injection is started at the second timing in the expansion stroke.
Gas engine with turbocharger.
A four-stroke engine, wherein the second timing is within the range of 60° to 180° ATDC,
The gas engine with a turbocharger according to claim 5.
The injection amount of the second injection is larger than the injection amount of the first injection.
The gas engine with a turbocharger according to claim 5 or 6.
When increasing the engine output from the first output value to the third output value via the second output value, the injector has an output increase rate from the first output value to the second output value, The injection amount of the liquid fuel in the first injection is changed so as to be larger than the output increase rate from the value to the third output value.
A gas engine with a turbocharger according to any one of claims 5 to 7.
Further provided with an air cooler for cooling the air sucked into the combustion chamber,
The air cooler is connected to the refrigerant flow path through which the refrigerant flows, and a bypass path that flows the refrigerant to the downstream side of the refrigerant flow path without heat exchange with the air, and flows through the refrigerant flow path. A flow rate adjusting device for adjusting the flow rate of the refrigerant flowing into the bypass passage among the refrigerant,
The flow rate adjusting device blocks the flow of the refrigerant from the refrigerant flow path to the bypass path when the engine load increases.
A gas engine with a turbocharger according to any one of claims 5 to 8.
The combustion chamber includes a cylinder and a piston that form a combustion chamber, and an injector that injects liquid fuel into the combustion chamber, and the piston reciprocates in the cylinder to generate a lean mixture of air and gas fuel. A combustion cycle consisting of an intake stroke for sucking in, a compression stroke for compressing the lean air-fuel mixture, an expansion stroke for expanding the combustion gas generated by the combustion of the lean air-fuel mixture, and an exhaust stroke for exhausting the combustion gas from the combustion chamber. Is a pilot ignition type gas engine with turbocharger,
When increasing the engine output from the first output value to the third output value via the second output value, the injector performs main injection in the compression stroke, and the injector outputs the first output value to the second output value. The injection amount of the liquid fuel in the main injection is changed so that the output increase rate becomes larger than the output increase rate from the second output value to the third output value.
Gas engine with turbocharger.
An engine that obtains power by burning a lean mixture of gas fuel and air;
A compressor having a compressor connected to the engine by an air supply pipe, and a turbocharger having a turbine connected to the engine by an exhaust pipe.
A gas fuel supply device that supplies the gas fuel to the air supply pipe,
An air cooler for cooling the air passing through the air supply pipe is provided.
The air cooler is a refrigerant passage through which a refrigerant flows, a bypass passage that is connected to the refrigerant passage and flows the refrigerant to the downstream side of the refrigerant passage without heat exchange with the air, and the refrigerant passage. Of the refrigerant, it has a flow rate adjusting device for adjusting the flow rate of the refrigerant flowing into the bypass passage, the flow rate adjusting device, when the engine load rises, the flow of the refrigerant from the refrigerant passage to the bypass passage. Cut off,
Gas engine with turbocharger.