JP2020197198A - Engine system - Google Patents

Abstract

To provide technique capable of obtaining high output or reducing exhaust emission, only by adopting a rational and simple structure, in an engine system performing supercharging in multistage.SOLUTION: An engine system is equipped with a high-pressure stage waist gate valve 1 disposed in a high-pressure stage bypass path 25 bypassing a high-pressure stage turbine in a discharge path and configured to adjust an opening. A control portion 60 executes the high-pressure waist gate valve that controls the opening of the high-pressure waist gate valve V1 on the basis of an output state of the engine 10.SELECTED DRAWING: Figure 2

Description

According to the present invention, a high-pressure turbocharger that takes in fresh air from an intake passage and discharges exhaust gas to an exhaust passage and a high-pressure stage turbine arranged in the exhaust passage rotates a high-pressure stage compressor arranged in the intake passage. A low-pressure turbocharger that rotates a low-pressure stage compressor arranged on the upstream side of the high-pressure stage compressor in the intake passage by a feeder and a low-pressure stage turbine arranged on the downstream side of the high-pressure stage turbine in the exhaust passage. It relates to an engine system including a machine and a control unit for controlling operation.

For example, as an engine system installed on a ship, a high-pressure turbocharger and a low-pressure turbocharger are provided to supercharge the engine in multiple stages (see, for example, Patent Document 1). .). Conventionally, in such an engine system, the maximum combustion pressure has been increased in order to achieve high output.

JP-A-2015-08625

In the engine system, when increasing the maximum combustion pressure for the purpose of achieving high output, it is necessary to strengthen the withstand voltage performance of the engine and each supercharger, so the structure and materials of various parts should be reviewed. Significant man-hours and costs were required to develop the engine.
Further, in such a multi-stage supercharging engine system, the temperature of the exhaust gas discharged from the low-pressure stage turbine is lowered, especially in the medium output range, so that the exhaust gas is sufficiently discharged in the exhaust gas treatment part such as the selective reduction catalyst part. Could not be processed and the exhaust emissions could not be reduced as desired.
In view of this situation, the main subject of the present invention is to provide a technique capable of increasing the output and reducing the exhaust emission by simply adopting a rational and simple configuration in a multi-stage supercharging engine system. There is a point to do.

The first characteristic configuration of the present invention is an engine that takes in fresh air from the intake passage and discharges exhaust gas to the exhaust passage.
A high-pressure turbocharger that rotates a high-pressure compressor arranged in the intake passage by a high-pressure turbine arranged in the exhaust passage.
A low-pressure turbocharger that rotates a low-pressure stage compressor arranged on the upstream side of the high-pressure stage compressor in the intake passage by a low-pressure stage turbine arranged on the downstream side of the high-pressure stage turbine in the exhaust passage.
An engine system equipped with a control unit that controls operation.
It is provided with a high-pressure stage waistgate valve arranged in the high-pressure stage bypass path that bypasses the high-pressure stage turbine in the exhaust path and configured to have an adjustable opening.
The point is that the control unit executes high-pressure stage waistgate valve control that controls the opening degree of the high-pressure stage waistgate valve based on the output state of the engine.

According to this configuration, the control unit executes high-pressure stage waistgate valve control to control the opening degree of the high-pressure stage waistgate valve based on the output state of the engine, so that high pressure is applied from the primary side of the high-pressure stage turbine in the exhaust passage. The flow rate of the exhaust gas extracted to the stage bypass path and bypassing the high-pressure stage turbine can be maintained in an appropriate state that contributes to, for example, high output and reduction of exhaust emissions.

Therefore, according to the present invention, in an engine system for multi-stage supercharging, a rational and simple configuration such as controlling the opening degree of a high-pressure stage waistgate valve based on the output state of the engine is simply adopted. It is possible to provide a technology that can realize high output and reduction of exhaust emissions.

The second characteristic configuration of the present invention is that the control unit controls the high-pressure stage waistgate valve so that the re-inflow destination of the exhaust gas from the high-pressure stage bypass path in the exhaust passage is the low-pressure stage turbine side. The point is to execute high output priority control that increases the opening degree of the high pressure stage waistgate valve as the output of the engine increases.

According to this configuration, when the control unit executes high output priority control, it is extracted from the primary side of the high-pressure stage turbine to the high-pressure stage bypass path in the exhaust passage and re-inflowed into the primary side of the low-pressure stage turbine. The flow rate of exhaust gas increases as the output of the engine increases. Then, even if the exhaust gas from the engine increases excessively as the output of the engine increases, the excess exhaust gas is extracted from the primary side of the high-pressure turbine to reduce the intake pressure of the engine. The exhaust pressure of the engine can be reduced as much as possible while suppressing as much as possible to increase the output. Further, the energy of the extracted exhaust gas can be recovered by the low-pressure stage turbine and used for supercharging the fresh air on the low-pressure side by the low-pressure stage compressor, so that the decrease in the intake pressure of the engine can be further suppressed.

The third characteristic configuration of the present invention includes an exhaust gas treatment unit which is arranged on the downstream side of the low-pressure stage turbine in the exhaust passage and has a selective reduction catalyst unit for reducing nitrogen oxides in the exhaust gas.
As the high-pressure stage waistgate valve control, the control unit sets the re-inflow destination of the exhaust gas from the high-pressure stage bypass path in the exhaust path to the exhaust gas treatment unit side, and the output of the engine decreases. The point is to execute exhaust emission priority control that expands the opening of the high-pressure stage waistgate valve.

According to this configuration, when the control unit executes the exhaust emission priority control, the flow rate of the exhaust gas that is extracted from the primary side of the high-pressure stage turbine to the high-pressure stage bypass path and re-inflowed into the exhaust gas treatment unit side in the exhaust passage. However, it increases as the engine output increases. Then, especially in the medium output region, the temperature of the exhaust gas supplied from the low-pressure stage turbine to the exhaust gas treatment unit decreases as the engine output decreases, and there is a concern that the activity of the selective reduction catalyst unit decreases. Even if there is, it is possible to increase the inflow amount of the relatively high temperature exhaust gas re-inflowing from the high-pressure stage bypass path to the exhaust gas treatment unit side. As a result, it is possible to suppress a decrease in the activity of the selective reduction catalyst portion due to a decrease in the output of the engine and prevent an increase in exhaust emissions.

In the fourth feature configuration of the present invention, in addition to the third feature configuration, the exhaust gas treatment section is arranged on the upstream side of the selective reduction catalyst section in the exhaust passage, and the reducing agent added to the exhaust passage is provided. It has an exhaust gas mixing promotion unit that promotes mixing with exhaust gas.
The exhaust gas re-inflowing from the high-pressure stage bypass path to the exhaust gas treatment unit side can be distributed and supplied to the selective reduction catalyst unit and the exhaust gas mixing promotion unit, and the distribution ratio of the exhaust gas to the exhaust gas mixing promotion unit can be adjusted. Equipped with a distribution ratio adjustment unit
In a state where the control unit sets the re-inflow destination of the exhaust gas from the high-pressure stage bypass path in the exhaust path to the exhaust gas treatment unit side, the exhaust gas mixing is promoted by the distribution ratio adjusting unit as the output of the engine increases. The point is to execute exhaust gas distribution control that increases the distribution ratio of exhaust gas to the unit.

According to this configuration, the exhaust gas mixing promotion unit is configured to supply the exhaust gas sufficiently mixed with the reducing agent to the selective reduction catalyst unit for treatment. Then, in the exhaust passage, the distribution ratio of the exhaust gas extracted from the primary side of the high-pressure turbine to the high-pressure bypass passage and re-inflowed into the exhaust gas treatment section is adjusted by the distribution section adjustment section to the exhaust gas mixing promotion section. As a result, it can be distributed and supplied to the primary side of the selective reduction catalyst section and the primary side of the exhaust gas mixing promotion section.

Further, when the control unit executes the exhaust gas distribution control, the exhaust gas mixing promotion unit of the exhaust gas that is extracted from the primary side of the high-pressure stage turbine to the high-pressure stage bypass path and re-inflowed into the exhaust gas treatment unit side in the exhaust passage. The flow rate of the exhaust gas distributed and supplied to the primary side is increased as the output of the engine increases. Then, even when the amount of the reducing agent added is increased with the increase in the output of the engine, particularly in the medium output region, the reducing agent can be satisfactorily mixed with the exhaust gas in the exhaust gas mixing promoting unit. As a result, it is possible to suppress insufficient mixing with the exhaust gas due to an increase in the amount of the reducing agent added, and prevent an increase in exhaust emissions.

The fifth characteristic configuration of the present invention includes an exhaust gas treatment unit having a selective reduction catalyst unit that is arranged on the downstream side of the low-pressure stage turbine in the exhaust passage and reduces nitrogen oxides in the exhaust gas.
The point is that the re-inflow destination switching portion capable of switching the re-inflow destination of the exhaust gas from the high-pressure stage bypass path in the exhaust passage between the low-pressure stage turbine side and the exhaust gas treatment unit side is provided.

According to this configuration, in a state where the re-inflow destination of the exhaust gas is switched to the low-pressure stage turbine side by the re-inflow destination switching unit, the control unit performs, for example, the high output priority control shown in the second characteristic configuration in the high-pressure stage waist. By executing as gate valve control, the flow rate of the exhaust gas that is extracted from the primary side of the high-pressure stage turbine to the high-pressure stage bypass path and re-inflowed into the primary side of the low-pressure stage turbine in the exhaust passage is adjusted to an appropriate level. It is possible to increase the output by reducing the exhaust pressure of the engine as much as possible while suppressing the decrease of the intake pressure of the engine as much as possible.

Further, in a state where the re-inflow destination of the exhaust gas is switched to the exhaust gas treatment unit side by the re-inflow destination switching unit, the control unit executes, for example, the exhaust emission priority control shown in the third characteristic configuration as the high-pressure stage waistgate valve control. By doing so, the flow rate of the exhaust gas that is extracted from the primary side of the high-pressure stage turbine to the high-pressure stage bypass path and re-inflowed into the exhaust gas treatment section side in the exhaust path is adjusted to an appropriate level, and selection is made based on the decrease in engine output. It is possible to suppress a decrease in the activity of the reduction catalyst portion and prevent an increase in exhaust emissions.

The figure which shows the 1st state of the engine system in embodiment of this invention. The figure which shows the 2nd state of the engine system in embodiment of this invention. The figure which shows the 3rd state of the engine system in embodiment of this invention. The figure which shows the control flow of the engine system in embodiment of this invention. Graph diagram exemplifying the relationship between engine output and high-pressure stage waistgate valve opening target value in high-power priority control Graph diagram illustrating the relationship between the engine output and the opening target value of the high-pressure stage waistgate valve in exhaust emission priority control Graph diagram exemplifying the relationship between engine output and distribution ratio target value in exhaust gas distribution control

An embodiment of the engine system according to the present invention will be described with reference to the drawings.
In the engine system shown in FIGS. 1 to 3, the flow path through which the gas is flowing is indicated by a solid line, and the flow path through which the gas is stopped is indicated by a broken line. Further, in the figure, the valve in the closed state is shown in black, and the valve in the open state is shown in white.

As shown in FIGS. 1 to 3, the engine system of the present embodiment (hereinafter referred to as “the engine system”) takes in fresh air A from the intake passages 12, 13 and 14, and exhaust passages 16 and 17. , 18 includes an engine 10 that discharges exhaust gas E, and a control device 60 (an example of a control unit) that controls the operation of the engines 10.

This engine system is an engine system mounted on a ship, and includes one or more engines 10 for driving a generator 20 that generates power consumption in the ship. The control device 60 provided in this engine system is configured to appropriately operate each engine 10 according to the electric power load in the ship.

This engine system is configured such that a high-pressure turbocharger 30 and a low-pressure turbocharger 40 are connected in series to the engine 10 to perform multi-stage turbocharging. That is, the high-pressure stage compressor 31 of the high-pressure stage turbocharger 30 and the low-pressure stage compressor 41 of the low-pressure stage supercharger 40 are arranged in series in the intake passages 12, 13, and 14. On the other hand, in the exhaust passages 16, 17, and 18, the high-pressure stage turbine 32 of the high-pressure stage supercharger 30 and the low-pressure stage turbine 42 of the low-pressure stage supercharger 40 are arranged in series.

Here, in the intake passages 12, 13 and 14, the intake passage connecting the intake manifold of the engine 10 and the secondary side (fresh air outflow side) of the high-pressure stage compressor 31 is referred to as a high-pressure intake passage 12. The intake passage connecting the primary side (fresh air inflow side) of the high-pressure stage compressor 31 and the secondary side (fresh air inflow side) of the low-pressure stage compressor 41 is called a medium-pressure intake passage 13. Further, the intake passage connecting the primary side (fresh air inflow side) of the low pressure stage compressor 41 and the atmosphere side is referred to as a low pressure intake passage 14. On the other hand, in the exhaust passages 16, 17, and 18, the exhaust passage connecting the exhaust manifold of the engine 10 and the primary side (exhaust gas inflow side) of the high-pressure stage turbine 32 is called a high-pressure exhaust passage 16. The exhaust passage connecting the secondary side (exhaust gas outflow side) of the high-pressure turbine 32 and the primary side (exhaust gas inflow side) of the low-pressure turbine 42 is called a medium-pressure exhaust passage 17. Further, the exhaust passage connecting the secondary side (exhaust gas outflow side) of the low-pressure turbine 42 and the atmosphere side is referred to as a low-pressure exhaust passage 18.

The high-pressure turbocharger 30 is configured as a so-called turbocharger in which the high-pressure stage compressors 31 arranged in the intake passages 12 and 13 are rotated by the high-pressure stage turbines 32 arranged in the exhaust passages 16 and 17. .. Specifically, the energy of the exhaust gas E flowing from the engine 10 into the high-pressure turbine 32 through the high-pressure exhaust passage 16 is recovered, and the high-pressure turbine 32 rotates. Then, the high-pressure stage compressor 31 connected to the high-pressure stage turbine 32 rotates, and the fresh air A flowing into the high-pressure stage compressor 31 from the medium-pressure intake passage 13 is pressurized. Then, the fresh air A pressurized by the high-pressure stage compressor 31 can be sucked into the engine 10 through the high-pressure intake passage 12 provided with the air cleaner 23.

The low-pressure turbocharger 40 is configured as a so-called turbocharger in which the low-pressure stage compressors 41 arranged in the intake passages 13 and 14 are rotated by the low-pressure stage turbines 42 arranged in the exhaust passages 17 and 18. .. Specifically, the energy of the exhaust gas E flowing from the high-pressure stage turbine 32 into the low-pressure stage turbine 42 through the medium-pressure exhaust passage 17 is recovered, and the low-pressure stage turbine 42 rotates. Then, the low-pressure stage compressor 41 connected to the low-pressure stage turbine 42 rotates, and the fresh air A flowing into the low-pressure stage compressor 41 from the low-pressure intake passage 14 is pressurized. Then, the fresh air A pressurized by the low-pressure stage compressor 41 can be supplied to the high-pressure stage compressor 31 through the medium-pressure intake passage 13 provided with the intercooler 24.

The low-pressure exhaust passage 18 on the downstream side of the low-pressure stage turbine 42 in the exhaust passages 16, 17, and 18 is provided with an exhaust gas treatment unit 50 having a selective reduction catalyst unit 54 for reducing nitrogen oxides in the exhaust gas E. .. The selective reduction catalyst unit 54 is configured as an exhaust gas purification unit using SCR (selective reduction catalyst: Selective Catalytic Reduction) that selectively reduces and purifies NOx (nitrogen oxides) in the exhaust gas E. That is, in the selective reduction catalyst unit 54, the reducing agent U such as urea water injected from the reducing agent addition nozzle 51 arranged on the upstream side of the selective reduction catalyst unit 54 in the low pressure exhaust passage 18 is hydrolyzed by the heat of the exhaust gas E. It is disassembled. Then, the NOx in the exhaust gas E is selectively reduced to water and nitrogen by the reducing action of the ammonia produced thereby, and the exhaust gas E is purified.
The exhaust gas treatment unit 50 provided in the low-pressure exhaust passage 18 is arranged on the upstream side of the selective reduction catalyst unit 54 and on the downstream side of the reducing agent addition nozzle 51, and the reduction added to the low-pressure exhaust passage 18 An exhaust gas mixing promoting unit 52 for promoting mixing of the agent U and the exhaust gas E is provided.

In this engine system, as high-pressure stage bypass paths that bypass the high-pressure stage turbine 32 in the exhaust paths 16, 17, and 18, the take-out path 25, the first re-inflow path 26, the second re-inflow path 27, and the first distribution path 28 And the second distribution path 29 are arranged. Further, a high-pressure stage waistgate valve V1, a re-inflow destination switching valve V2 (an example of a re-inflow destination switching unit), and a distribution ratio adjusting valve V3 (an example of a distribution ratio adjusting unit) are arranged in this high-pressure stage bypass path. ing.

The take-out passage 25 is configured as a flow path connecting the high-pressure exhaust passage 16 and the inflow side port Pi of the re-inflow destination switching valve V2. Further, the take-out path 25 is provided with a high-pressure stage waistgate valve V1 configured so that the opening degree can be adjusted.
The high-pressure stage waistgate valve V1 is configured so that the opening degree can be adjusted based on a command signal input from the control device 60.

Then, by adjusting the opening degree of the high-pressure stage waistgate valve V1, the flow rate of the exhaust gas E extracted from the high-pressure exhaust passage 16 to the take-out passage 25 and bypassing the high-pressure stage turbine 32 can be set to an appropriate state. it can.

The first reinflow passage 26 is configured as a flow path connecting the first outflow side port P1 of the reinflow destination switching valve V2 and the medium pressure exhaust passage 17 which is the primary side of the low pressure stage turbine 42.
The second reinflow passage 27 is configured as a flow path connecting the second outflow side port P2 of the reinflow destination switching valve V2 and the inflow side port Pi of the distribution ratio adjusting valve V3.
The re-inflow destination switching valve V2 can switch the port to be opened to the inflow side port Pi of the first outflow side port P1 and the second outflow side port P2 based on the command signal input from the control device 60. It is configured in.

Then, if the state of the re-inflow destination switching valve V2 is set to a state in which the first outflow side port P1 is opened with respect to the inflow side port Pi and the second outflow side port P2 is shut off (the state shown in FIG. 2), high-pressure exhaust is performed. The re-inflow destination of the exhaust gas E extracted from the passage 16 to the take-out passage 25 and bypassing the high-pressure stage turbine 32 can be set to the low-pressure stage turbine 42 side through the first re-inflow passage 26. On the other hand, if the state of the re-inflow destination switching valve V2 is set to a state in which the first outflow side port P1 is shut off and the second outflow side port P2 is opened with respect to the inflow side port Pi (state shown in FIG. 3), high pressure exhaust is performed. The re-inflow destination of the exhaust gas E extracted from the path 16 to the take-out path 25 and bypassing the high-pressure stage turbine 32 may be set to the inflow side port Pi of the distribution ratio adjusting valve V3 through the second re-inflow path 27. it can.

The first distribution path 28 is configured as a flow path connecting the first outflow side port P1 of the distribution ratio adjusting valve V3 and the primary side (exhaust gas inflow side) of the selective reduction catalyst section 54 in the low pressure exhaust path 18.
The second distribution path 29 is configured as a flow path connecting the second outflow side port P2 of the distribution ratio adjusting valve V3 and the primary side (exhaust gas inflow side) of the exhaust gas mixing promotion unit 52 in the low pressure exhaust path 18.

As shown in FIG. 3, the distribution ratio adjusting valve V3 connects the exhaust gas E flowing into the inflow side port Pi from the second reinflow path 27 to the primary side of the selective reduction catalyst section 54 (first distribution path 28 (first)). 1 Outflow side port P1 side) and the second distribution path 29 (second outflow side port P2 side) leading to the primary side of the exhaust gas mixing promotion unit 52 can be distributed and supplied. Further, the distribution ratio adjusting valve V3 is configured to be able to adjust the distribution ratio of the exhaust gas E to the second distribution path 29 leading to the primary side of the exhaust gas mixing promotion unit 52 based on the command signal input from the control device 60. ing.

Therefore, the exhaust gas E extracted from the high-pressure exhaust passage 16 into the take-out passage 25 and flowing into the inflow side port Pi of the distribution ratio adjusting valve V3 through the second reinflow passage 27 is accompanied by the distribution ratio adjustment by the distribution ratio adjusting valve V3. Therefore, it can be distributed and supplied to the primary side of the selective reduction catalyst unit 54 and the primary side of the exhaust gas mixing promotion unit 52 in the low pressure exhaust passage 18. The exhaust gas E extracted from the high-pressure exhaust passage 16 to the extraction passage 25 has a relatively high temperature. Therefore, the high-temperature exhaust gas E distributed and supplied to the primary side of the selective reduction catalyst unit 54 can contribute to the improvement of the activity of the selective reduction catalyst unit 54. On the other hand, the high-temperature exhaust gas E distributed to the primary side of the exhaust gas mixing promoting unit 52 can contribute to the mixing promotion of the reducing agent U in the exhaust gas mixing promoting unit 52.

Detection signals of various sensors are input to the control device 60, and the output and rotation speed of the engine 10 are input from the generator 20 and the like.
The sensors include a pressure sensor 21 that detects the intake pressure of the engine 10, a pressure sensor 22 that detects the exhaust pressure of the engine 10, a temperature sensor 55 that detects the temperature of the selective reduction catalyst unit 54, and the temperature of the exhaust gas mixing promotion unit 52. A temperature sensor 53 or the like for detecting the above is provided.

This engine system adopts the above rational and simple configuration, and only by implementing the characteristic operation control by the control device 60, the output is increased while maintaining low fuel consumption, and especially the medium output. It is configured to make it possible to reduce exhaust emissions in the region.
Hereinafter, the details of the operation control performed by the control device 60 of the engine system will be described along with the control flow and the like shown in FIG.

First, the control device 60 switches the state of the re-inflow destination switching valve V2 using the current position information of the ship on which the engine system is mounted, and is extracted from the high-pressure exhaust passage 16 to the take-out passage 25 to reach the high-pressure stage. The re-inflow destination switching control for switching the re-inflow destination of the exhaust gas E bypassing the turbine 32 is executed (step # 1, step # 2, step # 4 in FIG. 4).
That is, in this re-inflow destination switching control, first, it is determined whether or not the current position of the ship is in the air pollutant release restricted sea area (ECA: Emission Control Area) (step # 1 in FIG. 4).

When the current position of the ship is not in the air pollutant release restricted sea area (NECA in step # 1 in FIG. 4), the state of the re-inflow destination switching valve V2 is the first outflow side port with respect to the inflow side port Pi. A state in which P1 is opened and the second outflow side port P2 is shut off (state shown in FIG. 2) is set (step # 2 in FIG. 4). Then, the exhaust gas E extracted from the high-pressure exhaust passage 16 into the take-out passage 25 and bypassing the high-pressure stage turbine 32 is re-inflowed into the primary side of the low-pressure stage turbine 42 through the first re-inflow passage 26.

On the other hand, when the current position of the ship is in the air pollutant release restricted sea area (ECA in step # 1 in FIG. 4), the state of the re-inflow destination switching valve V2 is the first outflow side port with respect to the inflow side port Pi. A state in which P1 is shut off and the second outflow side port P2 is opened (state shown in FIG. 3) is set (step # 4 in FIG. 4). Then, the exhaust gas E, which is extracted from the high-pressure exhaust passage 16 and bypasses the high-pressure stage turbine 32 and is re-inflowed to the exhaust gas treatment unit 50 side, is supplied to the distribution ratio adjusting valve V3 through the second re-inflow passage 27, and the distribution ratio is increased. The distribution is distributed and supplied to the primary side of the selective reduction catalyst section 54 and the primary side of the exhaust gas mixing promotion section 52 in the low pressure exhaust passage 18 with the distribution rate adjustment by the adjusting valve V3.

In the re-inflow destination switching control for the re-inflow destination switching valve V2 in step # 2 of FIG. 4, the exhaust gas E bypassing the high-pressure stage turbine 32 is re-inflowed to the primary side of the low-pressure stage turbine 42. Then, the control device 60 increases the output of the engine 10 while maintaining low fuel consumption as the high-pressure stage waistgate valve control that controls the opening degree of the high-pressure stage waistgate valve V1 based on the output state of the engine 10. High-voltage priority control (step # 3 in FIG. 4) for attempting is executed.

The high output priority control (step # 3 in FIG. 4) is configured as a control for increasing the opening degree of the high pressure stage waistgate valve V1 as the output of the engine 10 increases.
For example, as shown in FIG. 5, when the output of the engine 10 is less than the first output W1 which is the lower limit of the high output region (for example, 85% of the maximum output Wr1 when the high output priority control is executed), the high voltage is high. The step waistgate valve V1 is fully closed (the state shown in FIG. 1). Then, the entire amount of the exhaust gas E discharged from the engine 10 to the high-pressure exhaust passage 16 is supplied to the high-pressure stage turbine 32.
Since the output of the engine 10 is increased when the high output priority control is executed, the maximum output Wr1 when the high output priority control is executed is the maximum output Wr2 when the exhaust emission priority control is executed, which will be described later. It is set to a value larger than (see FIGS. 6 and 7), and the output difference is set to about 10%, for example.

Further, when the output of the engine 10 is in the high output region within the range of the first output W1 or more and the maximum output Wr1 or less, the opening degree of the high-pressure stage waistgate valve V1 increases as the output of the engine 10 increases. For example, it is expanded to the fully open state. Then, the exhaust gas E is extracted from the high-pressure exhaust passage 16 on the primary side of the high-pressure turbine 32 into the take-out passage 25 and re-inflowed into the medium-pressure exhaust passage 17 on the primary side of the low-pressure turbine 42 through the first re-inflow passage 26. The flow rate of the engine 10 is increased as the output of the engine 10 is increased.

When such high output priority control is executed, the amount of exhaust gas E emitted from the engine 10 to the high-pressure exhaust passage 16 increases excessively in the high output region as the output of the engine 10 increases. Even if there is, the excess exhaust gas E is extracted from the primary side of the high-pressure stage turbine 32, so that the decrease in the intake pressure of the engine 10 is suppressed as much as possible, while the exhaust pressure of the engine 10 is reduced as much as possible, and the intake pressure is reduced. And the exhaust pressure are widened. As a result, the output of the engine 10 can be increased while maintaining low fuel consumption. Further, the energy of the extracted exhaust gas E is recovered by the low-pressure stage turbine 42 and used for supercharging the low-pressure side of the fresh air A by the low-pressure stage compressor 41, so that the intake pressure of the engine 10 is further reduced. It is suppressed.

In the re-inflow destination switching control for the re-inflow destination switching valve V2 in step # 4 of FIG. 4, the exhaust gas E bypassing the high-pressure stage turbine 32 is the primary side of the selective reduction catalyst section 54 and the primary side of the exhaust gas mixing promotion section 52. It will be in a state of being distributed and supplied to. Then, the control device 60 is used as a high-pressure stage waistgate valve control for controlling the opening degree of the high-pressure stage waistgate valve V1 based on the output state of the engine 10, in order to prevent an increase in exhaust emissions particularly in the medium output range. Exhaust gas emission priority control (step # 5 in FIG. 4) and exhaust gas distribution control (step # 6 in FIG. 4) are executed.

The exhaust emission priority control (step # 5 in FIG. 4) is configured as a control for increasing the opening degree of the high-pressure stage waistgate valve V1 as the output of the engine 10 decreases.
For example, as shown in FIG. 6, when the output of the engine 10 is less than the third output W3 (for example, 25% of the maximum output Wr2 when the exhaust emission priority control is executed), or the output of the engine 10 is the second output W2. When it is larger than (for example, 60% of the maximum output Wr2), the high-pressure stage waistgate valve V1 is in a fully closed state (state shown in FIG. 1). Then, the entire amount of the exhaust gas E discharged from the engine 10 to the high-pressure exhaust passage 16 is supplied to the high-pressure stage turbine 32.

Further, when the output of the engine 10 is in the medium output range within the range of the third output W3 or more and the second output W2 or less, the opening degree of the high-pressure stage waistgate valve V1 accompanies the decrease in the output of the engine 10. For example, the opening is increased to 30% of the fully open state. Then, it is extracted from the high-pressure exhaust passage 16 on the primary side of the high-pressure stage turbine 32 to the take-out passage 25 and distributed to the primary side of the selective reduction catalyst section 54 and the primary side of the exhaust gas mixing promotion section 52 through the second re-inflow passage 27. The flow rate of the supplied exhaust gas E is increased as the output of the engine 10 decreases.

Especially in the medium output region, as the output of the engine 10 decreases, the temperature of the exhaust gas E supplied from the low-pressure stage turbine 42 to the exhaust gas treatment unit 50 through the low-pressure exhaust passage 18 decreases, and the activity of the selective reduction catalyst unit 54 becomes active. There is concern about a decline. However, by executing the exhaust emission priority control as described above, the inflow amount of the relatively high temperature exhaust gas E that bypasses the high pressure stage turbine 32 and is re-inflowed to the exhaust gas treatment unit 50 side increases. .. As a result, the decrease in the activity of the selective reduction catalyst unit 54 due to the decrease in the output of the engine 10 is suppressed, and as a result, the increase in exhaust emissions is prevented, especially in the medium output range.

Further, the exhaust gas distribution control (step # 6 in FIG. 4), which is executed at the same time as the exhaust gas emission priority control, is performed in a state where the re-inflow destination of the exhaust gas E bypassing the high-pressure stage turbine 32 is the exhaust gas treatment unit 50 side. As the output of the engine 10 increases, the distribution ratio adjusting valve V3 determines the distribution ratio of the total amount of exhaust gas E distributed and supplied to the selective reduction catalyst unit 54 and the exhaust gas mixing promoting unit 52 to the exhaust gas mixing promoting unit 52. It is configured as a control to increase.
For example, as shown in FIG. 7, when the output of the engine 10 is less than the third output W3 (for example, 25% of the maximum output Wr2), the distribution ratio adjusting valve V3 is placed on the primary side of the selective reduction catalyst unit 54. The first outflow side port P1 that communicates is fully opened, while the second outflow side port P2 that communicates with the primary side of the exhaust gas mixing promotion unit 52 is fully closed. As a result, the entire amount of the relatively high temperature exhaust gas E that bypasses the high-pressure stage turbine 32 and is re-flowed into the exhaust gas treatment unit 50 side is supplied to the primary side of the selective reduction catalyst unit 54, and the selective reduction catalyst unit 54 The temperature rise is promoted.

Further, when the output of the engine 10 is in the medium output range within the range of the third output W3 or more and the second output W2 or less, the first outflow side port P1 and the second outflow side in the distribution ratio adjusting valve V3 The balance of the opening degree of the port P2 is adjusted, bypassing the high-pressure stage turbine 32 and re-flowing into the exhaust gas treatment unit 50 side to the primary side of the exhaust gas mixing promotion unit 52 out of the total amount of the relatively high temperature exhaust gas E. The distribution ratio of the exhaust gas E to be distributed and supplied is increased to, for example, a predetermined ratio R3 (for example, 100%) as the output of the engine 10 increases.

By executing the exhaust gas distribution control in this way, the flow rate of the exhaust gas E distributed and supplied to the exhaust gas mixing promotion unit 52 among the exhaust gas E re-inflowing to the exhaust gas treatment unit 50 side by bypassing the high-pressure stage turbine 32 becomes It is increased as the output of the engine 10 increases. Then, even when the amount of the reducing agent U added increases as the output of the engine 10 increases, particularly in the medium output region, the exhaust gas mixing promoting unit 52 mixes the reducing agent U with the exhaust gas E well. Promoted to. As a result, insufficient mixing with the exhaust gas E due to an increase in the amount of the reducing agent U added is suppressed, and an increase in exhaust emissions is prevented, especially in the medium output range.

[Another Embodiment]
Other embodiments of the present invention will be described. The configurations of the respective embodiments described below are not limited to being applied independently, but can also be applied in combination with the configurations of other embodiments.

(1) In the above embodiment, the control device 60 is configured to execute high output priority control and exhaust emission priority control as high pressure stage waist gate valve control, but the high pressure stage waist is based on the output state of the engine 10. As long as it controls the opening degree of the gate valve V1, it may be configured to execute a high-pressure stage waist gate valve control of a different form from these.

(2) In the above embodiment, the exhaust gas E extracted from the high-pressure exhaust passage 16, bypassing the high-pressure stage turbine 32, and re-flowing into the exhaust gas treatment unit 50 side is the primary of the selective reduction catalyst unit 54 in the low-pressure exhaust passage 18. Although it is configured to distribute and supply to the side and the primary side of the exhaust gas mixing promotion unit 52, the position and number of the re-inflow destinations of the exhaust gas E in such a low pressure exhaust passage 18 can be appropriately changed, and selective reduction can be performed. It is also possible to bypass the high-pressure stage turbine 32 at a specific location on the upstream side of the catalyst unit 54 and re-inflow the entire amount of the exhaust gas E that is re-inflowed to the exhaust gas treatment unit 50 side.

10 Engine 12 High-pressure intake path (intake path)
13 Medium pressure intake path (intake path)
14 Low pressure intake path (intake path)
16 High-pressure exhaust passage (exhaust passage)
17 Medium pressure exhaust passage (exhaust passage)
18 Low pressure exhaust passage (exhaust passage)
25 Take-out route (high-voltage stage bypass route)
26 1st re-inflow path (high pressure stage bypass path)
27 Second re-inflow path (high pressure stage bypass path)
28 First distribution path (high-voltage stage bypass path)
29 Second distribution path (high-voltage stage bypass path)
30 High-pressure stage supercharger 31 High-pressure stage compressor 32 High-pressure stage turbine 40 Low-pressure stage supercharger 41 Low-pressure stage compressor 42 Low-pressure stage turbine 50 Exhaust gas treatment unit 52 Exhaust gas mixing promotion unit 54 Selective reduction catalyst unit 60 Control device (control unit)
A Shinki E Exhaust gas V1 High-pressure stage waistgate valve V2 Re-inflow destination switching valve (re-inflow destination switching part)
V3 distribution ratio adjustment valve (distribution ratio adjustment unit)

Claims (5)

An engine that takes in fresh air from the intake passage and discharges exhaust gas to the exhaust passage,
A high-pressure turbocharger that rotates a high-pressure compressor arranged in the intake passage by a high-pressure turbine arranged in the exhaust passage.
A low-pressure turbocharger that rotates a low-pressure stage compressor arranged on the upstream side of the high-pressure stage compressor in the intake passage by a low-pressure stage turbine arranged on the downstream side of the high-pressure stage turbine in the exhaust passage.
An engine system equipped with a control unit that controls operation.
It is provided with a high-pressure stage waistgate valve arranged in the high-pressure stage bypass path that bypasses the high-pressure stage turbine in the exhaust path and configured to have an adjustable opening.
An engine system in which the control unit executes high-pressure stage waistgate valve control that controls the opening degree of the high-pressure stage waistgate valve based on the output state of the engine. As the high-pressure stage waistgate valve control, the control unit sets the re-inflow destination of the exhaust gas from the high-pressure stage bypass path in the exhaust passage to the low-pressure stage turbine side, and the output of the engine increases. The engine system according to claim 1, wherein the high output priority control for expanding the opening degree of the high pressure stage waistgate valve is executed. An exhaust gas treatment unit having a selective reduction catalyst unit that is arranged downstream of the low-pressure stage turbine in the exhaust passage and reduces nitrogen oxides in the exhaust gas is provided.
As the high-pressure stage waistgate valve control, the control unit sets the re-inflow destination of the exhaust gas from the high-pressure stage bypass path in the exhaust path to the exhaust gas treatment unit side, and the output of the engine decreases. The engine system according to claim 1 or 2, wherein the exhaust emission priority control for expanding the opening degree of the high-pressure stage waistgate valve is executed. The exhaust gas treatment unit has an exhaust gas mixing promoting unit that is arranged on the upstream side of the selective reduction catalyst unit in the exhaust gas passage and promotes mixing of the reducing agent added to the exhaust gas and the exhaust gas.
The exhaust gas re-inflowing from the high-pressure stage bypass path to the exhaust gas treatment unit side can be distributed and supplied to the selective reduction catalyst unit and the exhaust gas mixing promotion unit, and the distribution ratio of the exhaust gas to the exhaust gas mixing promotion unit can be adjusted. Equipped with a distribution ratio adjustment unit
In a state where the control unit sets the re-inflow destination of the exhaust gas from the high-pressure stage bypass path in the exhaust path to the exhaust gas treatment unit side, the exhaust gas mixing is promoted by the distribution ratio adjusting unit as the output of the engine increases. The engine system according to claim 3, wherein the exhaust gas distribution control for increasing the distribution ratio of the exhaust gas to the unit is executed. An exhaust gas treatment unit having a selective reduction catalyst unit that is arranged downstream of the low-pressure stage turbine in the exhaust passage and reduces nitrogen oxides in the exhaust gas is provided.
Claims 1 to 4 provided with a re-inflow destination switching unit capable of switching the re-inflow destination of exhaust gas from the high-pressure stage bypass path in the exhaust path between the low-pressure stage turbine side and the exhaust gas treatment unit side. The engine system according to any one item.

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