WO2015162840A1 - Engine system - Google Patents

Abstract

In this engine system, from a state in which a main supercharger and an auxiliary supercharger operate, the auxiliary turbine inlet valve and the auxiliary compressor outlet valve are closed and the auxiliary supercharger stopped while keeping the main supercharger operating; when reducing the number of superchargers operating, a stop-time reference pressure having a prescribed surge margin is determined on the basis of the rotation speed of the auxiliary supercharger, and a blowoff valve is opened when the outlet pressure of the auxiliary compressor is higher than the stop-time reference pressure and the blowoff valve is closed when the outlet pressure of the auxiliary compressor is lower than the stop-time reference pressure.

Description

Engine system

The present invention relates to an engine system that includes a plurality of superchargers and that can change the number of superchargers to be operated in accordance with operating conditions.

Generally, in an engine system equipped with a supercharger, the supercharger is selected so that efficient operation can be performed when the engine body is heavily loaded. However, an engine system that often operates the engine main body at a medium load and a low load from the viewpoint of fuel consumption or the like may include two superchargers, a main supercharger and a subsupercharger. In this engine system, when the engine body is operated at a high load, both the main supercharger and the sub-supercharger are operated, and when the engine body is operated at a medium load and a low load, only the main turbocharger is operated. Drive. With such a configuration, efficient operation is possible not only when the engine body is operated at a high load, but also when the engine body is operated at a medium load and a low load.

Also, in the case of an engine system equipped with an EGR unit that recirculates exhaust gas to the engine body, the amount of exhaust gas supplied to the turbocharger is smaller during EGR operation than during normal operation. If the number of operating superchargers is changed according to the above, efficient operation is possible while preventing surges in the supercharger.

In order to reduce the number of turbochargers operating while continuing engine operation, the secondary turbocharger must be stopped while the main turbocharger is operating. In this case, since the outside air boosted by the main supercharger flows back to the subsupercharger, an engine system that changes the number of operating superchargers has a valve on the outlet side of the compressor of the subsupercharger. ing. If this valve is closed, backflow can be prevented. However, if the operation of the sub-supercharger continues with the backflow prevention valve closed, a surge occurs because the back pressure of the compressor of the sub-supercharger increases. In view of this, such an engine system includes an air discharge pipe that guides air between the compressor of the sub-supercharger and the backflow prevention valve to the outside, and an air discharge valve provided in the air discharge pipe. And the generation | occurrence | production of a surge is avoided by opening a vent valve before closing the valve for backflow prevention (refer patent documents 1 thru | or 3).

Note that Patent Document 2 discloses a marine diesel engine provided with a check valve that is opened when the outlet pressure of the compressor section of the auxiliary exhaust turbine supercharger is equal to or higher than the pressure of the supply manifold. In the invention described in Patent Document 2, the backflow phenomenon can be prevented, but it is not determined whether or not the condition is such that a surge occurs. The invention described in Patent Document 3 is obtained by replacing the check valve with a control valve in the invention described in Patent Document 2. This control valve is opened when the differential pressure between the outlet pressure of the compressor section and the pressure of the air supply manifold becomes a predetermined value or less. Even in the invention described in Patent Document 3, it is not determined whether the conditions are such that a surge occurs. In either case, the control is limited because of the causal relationship between the differential pressure before and after the valve in the pipe and the number of states in the pipe at a location different from the surge occurrence location of the sub-exhaust turbine turbocharger.

JP-A-60-166716 JP 2009-167799 A JP 2011-47393 A

As described above, in the conventional engine system, in order to surely avoid a surge, the ventilating valve is opened early, and then the backflow prevention valve is closed. Therefore, the air that should be able to be supplied to the engine body is discharged to the outside. As a result, the pressure (scavenging pressure) of the scavenging gas supplied to the engine body is reduced, and the engine body cannot be operated efficiently.

The present invention has been made in view of the circumstances as described above. When changing the number of operating superchargers, the efficiency of the engine main body is improved while preventing a surge from occurring in the supercharger. It aims at providing the engine system which can suppress that it falls.

An engine system according to an aspect of the present invention includes an engine main body, at least one main supercharger having a main turbine and a main compressor, and the engine main body arranged in parallel with the main supercharger. At least one sub-supercharger having a turbine and a sub-compressor; a sub-turbine inlet valve provided on the inlet side of the sub-turbine; a sub-compressor outlet valve provided on the outlet side of the sub-compressor; An air discharge pipe for guiding outside air boosted by a compressor from the upstream side of the sub-compressor outlet valve to the outside, an air discharge valve provided in the air discharge pipe, and a control device. From the state in which the supercharger and the subsupercharger are operated, the subturbine inlet valve and the subcompressor outlet valve are closed while the main supercharger is operated, and the subsupercharger is operated. When stopping and reducing the number of operating turbochargers, determine the reference pressure at stop with a predetermined surge margin based on the sub-supercharger rotation speed, and the sub-compressor outlet pressure is higher than the reference pressure at stop The opening degree of the discharge valve is increased, and the opening degree of the discharge valve is decreased when the sub compressor outlet pressure is lower than the stop-time reference pressure.

According to such a configuration, the discharge valve is closed when the sub compressor outlet pressure is lower than the stop-time reference pressure. That is, when the possibility of occurrence of a surge is low, the outside air boosted by the sub-compressor with the vent valve closed is supplied to the engine body. As a result, it is possible to prevent the air boosted by the sub-compressor from being unnecessarily discharged to the outside, and to suppress a decrease in scavenging air pressure of the engine body. As a result, when the number of operating superchargers is reduced, it is possible to suppress a decrease in the efficiency of the engine body.

In the engine system, when the opening degree of the air discharge valve is increased, the controller increases the opening degree of the air discharge valve as the difference between the sub compressor outlet pressure and the stop-time reference pressure is smaller. The increase amount may be reduced.

According to such a configuration, when the operating point of the sub-compressor is not near the surge region, the increase amount of the opening degree of the discharge valve is small. That is, when the possibility that a surge occurs in the sub-compressor is not high, the outside air boosted by the sub-compressor is not released to the outside. As a result, the engine body can be efficiently operated by increasing the scavenging air pressure while further suppressing the occurrence of a surge in the auxiliary compressor.

An engine system according to an embodiment of the present invention is arranged in parallel with the main supercharger with respect to the engine body, at least one main supercharger having a main turbine and a main compressor, and the engine body. At least one sub-supercharger having a sub-turbine and a sub-compressor; a sub-turbine inlet valve provided on the inlet side of the sub-turbine; and a sub-compressor outlet valve provided on the outlet side of the sub-compressor; A ventilating pipe for guiding outside air boosted by the subcompressor from the upstream side of the subcompressor outlet valve to the outside, a ventilating valve provided in the ventilating pipe, and a control device, the control device, From the state where the main supercharger is operated and the subsupercharger is stopped, the subturbine inlet valve and the subcompressor outlet valve are opened while the main supercharger is operated. When operating the turbocharger and increasing the number of turbochargers to be operated, an operating reference pressure having a predetermined surge margin is determined based on the sub-supercharger speed, and the sub-compressor outlet pressure is set to the operating reference pressure. The opening degree of the discharge valve is increased when the pressure is higher than that, and the opening degree of the discharge valve is decreased when the sub-compressor outlet pressure is lower than the operating reference pressure.

According to such a configuration, when the outlet pressure of the sub compressor is lower than the reference pressure during operation, the opening degree of the air discharge valve decreases. That is, when the possibility of occurrence of a surge is low, a large amount of air boosted by the auxiliary compressor is supplied to the engine body by reducing the opening degree of the discharge valve. As a result, it is possible to prevent the air boosted by the sub-compressor from being unnecessarily discharged to the outside, and to suppress a decrease in scavenging air pressure of the engine body. As a result, when increasing the number of operating superchargers, it is possible to suppress a decrease in the efficiency of the engine body.

In the engine system, when the control device increases the opening degree of the air discharge valve, the smaller the difference between the outlet pressure of the sub-compressor and the reference pressure during operation, the lower the opening degree of the air discharge valve. The increase amount may be reduced.

According to such a configuration, when the operating point of the sub-compressor is not near the surge region, the increase amount of the opening degree of the discharge valve is small. That is, when the possibility that a surge occurs in the sub-compressor is not high, the outside air boosted by the sub-compressor is not released to the outside. As a result, the engine body can be efficiently operated by increasing the scavenging air pressure while further suppressing the occurrence of a surge in the auxiliary compressor.

In the engine system described above, when the control device increases the number of operating superchargers, after starting to open the auxiliary turbine inlet valve, the auxiliary supercharger rotational speed becomes equal to or higher than a predetermined switching rotational speed. The sub-compressor outlet valve starts to be opened, and the switching speed is determined according to the engine load. The switching speed is not determined by comparing the outlet pressure and scavenging pressure of the auxiliary compressor, but the operating curve of the auxiliary compressor (subcompressor flow rate and auxiliary compressor outlet) from just before opening the auxiliary compressor outlet valve to after completion of switching. Pressure relationship) and is determined taking into account that the secondary compressor will not surge.

According to this configuration, when the number of turbochargers to be operated is increased, the sub compressor outlet valve is closed until the sub supercharger rotation speed reaches the switching rotation speed, so that the outside air boosted by the main compressor is supplied to the sub compressor. It can be supplied to the engine body as scavenging gas without backflow. Therefore, the engine body can be operated efficiently. Further, since the switching speed is determined according to the engine load, the engine body can be operated more efficiently while avoiding a surge.

An engine system according to another embodiment of the present invention includes an engine main body, at least one main supercharger having a main turbine and a main compressor, and the main supercharger arranged in parallel to the engine main body. At least one sub-supercharger having a sub-turbine and a sub-compressor, a sub-turbine inlet valve provided on the inlet side of the sub-turbine, and a sub-compressor outlet valve provided on the outlet side of the sub-compressor An air discharge pipe for guiding outside air boosted by the auxiliary compressor from the upstream side of the auxiliary compressor outlet valve to the outside, an air discharge valve provided in the air discharge pipe, and a control device, the control device comprising: From the state where the main supercharger is operated and the subsupercharger is stopped, the subturbine inlet valve and the sub compressor outlet valve are opened while the main supercharger is operated. When operating the supercharger and increasing the number of superchargers to be operated, after opening the auxiliary turbine inlet valve with the discharge valve opened at a predetermined opening, the auxiliary turbocharger rotational speed is increased. When the discharge valve starts to be closed when the predetermined first switching rotational speed is reached, and when the sub-supercharger rotational speed becomes the second switching rotational speed that is greater than the first switching rotational speed The auxiliary compressor outlet valve is configured to start opening.

According to such a configuration, since the auxiliary compressor outlet valve starts to open with the air discharge valve closed to some extent, it is possible to suppress the release of outside air boosted by the auxiliary compressor to the outside through the air discharge valve. Further, it is possible to suppress the outside air boosted by the main compressor from flowing back to the sub compressor. Therefore, it can suppress that the efficiency of an engine main body falls.

In the engine system, the control device determines a first switching operation point (sub compressor flow rate and sub compressor outlet pressure) of the sub compressor having a predetermined surge margin based on an engine load, and the first compressor The sub-supercharger rotation speed of the pressure curve passing through the switching operation point (the relationship between the sub-compressor flow rate and the sub-compressor outlet pressure at each rotation speed of the sub-supercharger) is set as the first switching rotation speed. May be. The first switching speed is not determined by comparing the outlet pressure of the auxiliary compressor and the scavenging pressure, but from the time immediately before starting the closing of the discharge valve based on the engine load to the time immediately before starting the opening of the auxiliary compressor outlet valve. The compressor operating curve is predicted and determined so that the secondary compressor does not surge.

According to this configuration, the first switching operating point is determined based on the engine load, and the first switching rotational speed is determined using the first switching operating point. Therefore, it is possible to control the opening and closing of the air discharge valve without measuring the pressure such as the sub compressor outlet pressure. Therefore, depending on other conditions, a pressure gauge for measuring the pressure such as the sub compressor outlet pressure becomes unnecessary.

In the engine system, the control device determines a second switching operation point of the sub-compressor having a predetermined surge margin based on an engine load, and outputs a sub-pressure curve passing through the second switching operation point. The turbocharger rotational speed may be configured to be the second switching rotational speed. The second switching speed is not determined by comparing the outlet pressure and scavenging air pressure of the auxiliary compressor, but from immediately before the opening of the auxiliary compressor outlet valve based on the engine load to the end of the opening (switching completion). The operation curve is predicted and determined so that the secondary compressor does not surge.

According to such a configuration, the second switching operation point is determined based on the engine load, and further, the second switching rotation speed is determined using the second switching operation point. Therefore, it is possible to determine the timing at which the auxiliary compressor outlet valve starts to be opened without measuring the pressure such as the auxiliary compressor outlet pressure. Therefore, depending on other conditions, a pressure gauge for measuring the pressure such as the sub compressor outlet pressure becomes unnecessary.

Further, in the engine system, the control device acquires a main compressor outlet pressure when increasing the number of operating superchargers, a sub-supercharger rotational speed is equal to or higher than the second switching rotational speed, and The auxiliary compressor outlet valve may be configured to start to open when the acquired main compressor outlet pressure is smaller than the auxiliary compressor outlet pressure at the second switching operation point.

When determining the timing for opening the sub compressor outlet valve based on the engine load, the main compressor outlet pressure may be higher than the assumed pressure in situations where the engine load fluctuates rapidly. There is a risk that the outside air boosted by the main compressor will flow back to the sub compressor. On the other hand, in the above configuration, when the actual main compressor outlet pressure is acquired and there is a possibility of backflow, the subcompressor outlet pressure valve is not opened, so that backflow is prevented from occurring in the subcompressor. it can.

In the engine system, the control device sets a value equal to the acquired main compressor outlet pressure as a second switching pressure, and sets a value obtained by adding a predetermined flow rate to a sub compressor flow rate at which a surge occurs at the second switching pressure. The second switching flow rate, the operating point at the second switching pressure and the second switching flow rate as the second switching operating point, and the sub-supercharger rotation speed of the pressure curve passing through the second switching operating point is the You may be comprised so that it may be set as 2nd switching rotation speed.

According to such a configuration, since the second switching speed is determined based on the main compressor outlet pressure without using the engine load, even if the number of sub-superchargers is increased in a situation where the engine load fluctuates rapidly, Thus, backflow can be prevented from occurring in the auxiliary compressor.

In the engine system, the control device estimates an engine load based on the acquired main compressor outlet pressure, and the first switching operation point of the sub compressor having a predetermined surge margin based on the estimated engine load. And the sub-supercharger rotation speed of the pressure curve passing through the first switching operation point may be set as the first switching rotation speed.

According to such a configuration, since the first switching speed can be determined based on the main compressor outlet pressure, the engine load is directly acquired not only when determining the first switching speed but also the second switching speed. There is no need to do. That is, since the acquisition of the engine load can be omitted in the operation number increase control, the engine system can be simplified if the acquisition of the engine load can be omitted also in the operation number decrease control.

In the engine system, when the air discharge valve is closed, the controller decreases the opening of the air discharge valve as the difference between the sub-supercharger rotation speed and the first switching rotation speed decreases. May be configured to be small.

According to such a configuration, when the possibility of occurrence of a surge in the auxiliary compressor is low, it is possible to quickly close the air discharge valve, so that it is possible to further suppress a decrease in the efficiency of the engine body.

As described above, according to the engine system described above, it is possible to prevent the efficiency of the engine body from being reduced when changing the number of operating superchargers while preventing surges from occurring in the supercharger. Can do.

FIG. 1 is a schematic configuration diagram of the entire engine system according to the first embodiment. FIG. 2 is a block diagram of a control system of the engine system. FIG. 3 is a flowchart showing a supercharger operation number reduction control method. FIG. 4 is a time chart of the opening degree of each valve during supercharger operation number reduction control. FIG. 5 is a graph showing the relationship between the surge line and the stop-time reference pressure. FIG. 6 is a time chart of the sub compressor outlet pressure and scavenging pressure. FIG. 7 is a flowchart showing a method for increasing the number of operating superchargers according to the first embodiment. FIG. 8 is a time chart of the opening degree of each valve during the supercharger operation number increase control of the first embodiment. FIG. 9 is a graph showing the relationship between the engine load and the switching speed. FIG. 10 is an overall schematic diagram of an engine system according to a modification of FIG. FIG. 11 is a flowchart showing a method for increasing the number of operating superchargers according to the second embodiment. FIG. 12 is a time chart of the opening degree of each valve and the number of rotations of the sub-supercharger during the supercharger operation number increase control of the second embodiment. FIG. 13 is a graph showing the relationship between the engine load, the first switching pressure, and the second switching pressure. FIG. 14 is a graph showing the relationship between the engine load, the first switching flow rate, and the second switching flow rate. FIG. 15 is a diagram illustrating a method for determining the first switching rotation speed and the second switching rotation speed according to the second embodiment. FIG. 16 is a schematic configuration diagram of the entire engine system according to the third embodiment. FIG. 17 is a flowchart showing a method for increasing the number of operating superchargers according to the third embodiment. FIG. 18 is a flowchart showing a method for increasing the number of operating superchargers according to the fourth embodiment. FIG. 19 is a graph showing the relationship between the main compressor outlet pressure and the engine load. FIG. 20 is a diagram illustrating a method for determining the second switching rotation speed according to the fourth embodiment. FIG. 21 is an overall schematic diagram of an engine system according to another modification of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Below, the same code | symbol is attached | subjected to the element which is the same or it corresponds through all the drawings, and the overlapping description is abbreviate | omitted.

(First embodiment)
First, the first embodiment will be described.

<Overall configuration of engine system>
First, the overall configuration of the engine system 100 according to the present embodiment will be described. FIG. 1 is a schematic configuration diagram of the entire engine system 100. In FIG. 1, a thick broken line indicates the flow of exhaust gas, and a thick solid line indicates the flow of scavenging gas. As shown in FIG. 1, the engine system 100 includes an engine main body 10, a main supercharger 20, a sub supercharger 30, a sub turbine inlet valve 41, a sub compressor outlet valve 42, and an air discharge valve 43. It is equipped with.

The engine body 10 in the present embodiment is a main propulsion unit for a ship, and is a large two-stroke diesel engine. The engine body 10 is provided with an engine tachometer 11 (see FIG. 2) that measures the number of rotations of the engine body 10 (engine speed). The engine body 10 also includes a fuel supply device 12 (see FIG. 2) that adjusts the fuel injection amount. The engine body 10 may be a 4-stroke engine, a gas engine, or a gasoline engine. In the following description, “scavenging” is read as “supplying air” in the case of a 4-stroke engine.

The main supercharger 20 is a supercharger that always operates regardless of the operating state of the engine body 10. Exhaust gas discharged from the engine body 10 is supplied to the main turbine 22 via the main exhaust pipe 21. The main turbine 22 is rotated by the energy of the supplied exhaust gas. The main turbine 22 and the main compressor 23 are connected by a connecting shaft 24, and the main compressor 23 rotates as the main turbine 22 rotates. When the main compressor 23 rotates, the air (outside air) taken from outside is increased in pressure, and the increased outside air is supplied as scavenging gas to the engine body 10 via the main scavenging piping 25.

The sub-supercharger 30 is a supercharger that is operated or stopped according to the operating state of the engine body 10. The sub supercharger 30 is arranged in parallel with the main supercharger 20 with respect to the engine body 10. The sub-supercharger 30 may have the same specification (capacity) as the main supercharger 20 or a different specification. The exhaust gas discharged from the engine body 10 is supplied to the sub turbine 32 via the sub exhaust pipe 31. The sub turbine 32 is rotated by the energy of the supplied exhaust gas. The auxiliary turbine 32 and the auxiliary compressor 33 are connected by a connecting shaft 34, and the auxiliary compressor 33 also rotates as the auxiliary turbine 32 rotates. When the sub-compressor 33 rotates, the air (outside air) taken from the outside is increased in pressure, and the increased outside air is supplied as scavenging gas to the engine body 10 via the sub-scavenging piping 35 and the main scavenging piping 25.

In the present embodiment, the auxiliary scavenging pipe 35 is connected to the main scavenging pipe 25. An air cooler 50 that cools the scavenging gas is provided downstream of the portion of the main scavenging piping 25 to which the sub-scavenging piping 35 is connected. However, when the scavenging gas is not cooled and when the air cooler 50 is provided for each of the superchargers 20 and 30, the auxiliary scavenging pipe 35 may be directly connected to the engine body 10 without being connected to the main scavenging pipe 25. . The sub-supercharger 30 is provided with a sub-supercharger tachometer 36 that measures the rotation speed of the sub-supercharger 30 (sub-compressor 33). A sub-compressor outlet pressure gauge 37 that measures the pressure of the outside air (sub-compressor outlet pressure) increased by the sub-compressor 33 is provided near the outlet of the sub-compressor 33.

The auxiliary turbine inlet valve 41 is provided in the auxiliary exhaust pipe 31 and is a valve located on the inlet side of the auxiliary turbine 32. The auxiliary compressor outlet valve 42 is provided in the auxiliary scavenging pipe 35 and is a valve located on the outlet side of the auxiliary compressor 33. An air discharge pipe 44 is connected to a portion of the auxiliary scavenging pipe 35 upstream of the auxiliary compressor outlet valve 42. The air discharge pipe 44 is a pipe that guides outside air boosted by the sub compressor 33 to the outside. The air discharge valve 43 is provided in the air discharge pipe 44. Among the valves described above, the auxiliary turbine inlet valve 41 and the auxiliary compressor outlet valve 42 are open / close valves that can be switched to either fully closed or fully open in the present embodiment, but are adjustment valves that can adjust the opening degree. May be. It takes some time to switch between opening and closing these valves (see FIG. 4). On the other hand, the air discharge valve 43 is an adjustment valve capable of adjusting the opening degree in the present embodiment. However, the air discharge valve 43 is an on-off valve, and the opening degree may be adjusted by an inching operation (operation by an open command / close command).

<Control system configuration>
Next, the configuration of the control system of the engine system 100 will be described. FIG. 2 is a block diagram of a control system of engine system 100. As shown in FIG. 2, the engine system 100 includes a control device 60 that controls the entire engine system 100. The control device 60 is configured by, for example, a CPU, a ROM, a RAM, and the like.

The control device 60 is electrically connected to the engine tachometer 11, the fuel supply device 12, the sub supercharger tachometer 36, and the sub compressor outlet pressure gauge 37. The control device 60 acquires the engine speed, the fuel injection amount, the sub supercharger speed, the sub compressor outlet pressure, and the like based on signals transmitted from these devices. The control device 60 performs various calculations based on the input signals from the above devices and controls each part of the engine system 100. In the present embodiment, the control device 60 is electrically connected to the auxiliary turbine inlet valve 41, the auxiliary compressor outlet valve 42, and the ventilating valve 43, and to these devices based on the results of various calculations and the like. Send a control signal.

<Control of number of operating units>
Subsequently, from the state in which the main supercharger 20 and the subsupercharger 30 are operated, the subsupercharger 30 is stopped while the main supercharger 20 is operated, and the control (operation) is performed to reduce the number of operated superchargers. The number reduction control) will be described. FIG. 3 is a flowchart showing a method of operating number reduction control. The calculation and control described below are performed by the control device 60. FIG. 4 is a time chart showing the opening degrees of the auxiliary turbine inlet valve 41, the auxiliary compressor outlet valve 42, and the air discharge valve 43. Note that FIG. 4 is conceptually shown and does not necessarily match the actual value (the same applies to other time charts and graphs described below).

First, when the processing is started, the control device 60 simultaneously closes the auxiliary turbine inlet valve 41 and the auxiliary compressor outlet valve 42 (step S1). Thereby, the exhaust gas discharged from the engine main body 10 is not supplied to the sub turbine 32, and the rotational speed of the sub supercharger 30 gradually decreases. In addition, as shown in FIG. 4, it takes some time until these valves are fully opened to fully closed. For this reason, since it takes some time until the sub-supercharger 30 stops after the sub-turbine inlet valve 41 starts to close, it is assumed that the sub-compressor outlet valve 42 starts to close slightly later than the sub-turbine inlet valve 41. However, it is possible to prevent the outside air boosted by the main compressor 23 from flowing back to the sub compressor 33.

Subsequently, the control device 60 reads signals transmitted from the sub-supercharger tachometer 36 and the sub-compressor outlet pressure gauge 37, and acquires the sub-supercharger rotation speed and the sub-compressor outlet pressure based on these signals ( Step S2).

Subsequently, the control device 60 determines the stop-time reference pressure based on the sub-supercharger rotation speed acquired in Step S2 (Step S3). Here, FIG. 5 is a diagram showing the relationship between the sub compressor flow rate and the sub compressor outlet pressure at each rotation speed of the sub supercharger 30, that is, a diagram (compressor map) showing the pressure curve at each rotation speed. The thick line in the figure indicates a line (surge line) connecting points where a surge occurs at each rotation speed. The broken line in the figure is a stop-time reference pressure line that is preset to have a predetermined interval (surge margin) from the surge line. The above-mentioned “stop-time reference pressure” is a pressure at a point where this pressure curve and the stop-time reference pressure line intersect. The control device 60 stores data on the stop-time reference pressure for each rotation speed of the sub-supercharger 30. Therefore, the stop-time reference pressure can be determined based on the acquired rotation speed of the sub-supercharger 30.

Subsequently, the control device 60 determines whether or not the sub compressor outlet pressure is larger than the stop-time reference pressure (step S4). That is, it is determined whether or not there is a risk of occurrence of a surge in the sub compressor 33. If it is determined that the sub compressor outlet pressure is equal to or lower than the stop-time reference pressure (NO in step S4), the process proceeds to step S5. That is, if it is determined that there is no possibility of a surge occurring in the sub compressor 33, the process proceeds to step S5. On the other hand, if it is determined that the sub-compressor outlet pressure is greater than the stop-time reference pressure (YES in step S4), the process proceeds to step S6. That is, when it is determined that there is a possibility that a surge occurs in the sub compressor 33, the process proceeds to step S6.

When it is determined that there is no possibility of occurrence of a surge in the sub compressor 33, the control device 60 transmits a control signal to the air discharge valve 43 to decrease the opening degree of the air discharge valve 43. On the other hand, when it is determined that a surge may occur in the sub compressor 33 and the process proceeds to step S <b> 6, the control device 60 transmits a control signal to the air discharge valve 43 to increase the opening degree of the air discharge valve 43. In the present embodiment, the amount of change in the opening degree of the air discharge valve 43 is determined according to the difference between the sub compressor outlet pressure and the stop-time reference pressure. That is, the increase / decrease amount of the opening degree of the air discharge valve 43 is made small as the difference between the sub compressor outlet pressure and the stop-time reference pressure becomes small.

Subsequently, after step S5 or S6, the control device 60 determines whether or not the sub-supercharger 30 has stopped (step S7). That is, it is determined whether or not the sub supercharger rotational speed has become zero. If it is determined that the sub-supercharger 30 has stopped (YES in step S7), the process ends. On the other hand, if it is determined that the sub-supercharger 30 has not stopped (NO in step S7), the process returns to step S2 and repeats steps S2 to S8.

4, a time chart of the opening degree of the ventilating valve 43 (lower figure of FIG. 4) shows the opening degree of the ventilating valve 43 in the present embodiment, and the broken line shows the sub turbine inlet valve 41. The opening degree of the air discharge valve 43 when the air discharge valve 43 starts to open simultaneously with the start of closing the sub compressor outlet valve 42 (in the case of early opening) is shown. In addition, the thing of the patent documents 1 thru | or 3 mentioned above has begun to open the ventilation valve 43 at an earlier timing than what is shown with a broken line. As shown in this figure, in the case of the present embodiment, when there is no possibility of occurrence of a surge in the sub compressor 33, the air discharge valve 43 does not start to open. It can be delayed compared to the case. Furthermore, in this embodiment, the opening degree of the ventilating valve 43 does not increase at a constant rate, and the opening degree may be decreased when the possibility of occurrence of a surge is low. Thereby, the opening degree of the air discharge valve 43 can be made as small as possible in the range where a surge does not occur.

FIG. 6 is a diagram showing temporal changes in the sub compressor outlet pressure and scavenging pressure. In FIG. 6, the solid line shows the case of this embodiment, and the broken line shows the case of early opening (see the lower figure of FIG. 4). First, paying attention to the graph showing the time variation of the sub compressor outlet pressure in FIG. 6 (upper diagram in FIG. 6), in the case of this embodiment, the start of opening of the discharge valve 43 is slower than in the case of early opening. From this, it can be seen that the sub-compressor outlet pressure begins to decrease.

Subsequently, paying attention to the figure showing the time variation of the scavenging air pressure in FIG. 6 (the lower diagram in FIG. 6), the scavenging air pressure decreases less in the case of this embodiment than in the case of early opening. This is because in the case of the present embodiment, even after the sub compressor outlet valve 42 starts to close, the outside air increased in pressure by the sub compressor 33 can be used as the scavenging gas.

Thus, according to the present embodiment, when the number of superchargers to be operated is reduced, the sub-supercharger 30 is compared to the case where the ventilator valve 43 is opened early in consideration of the occurrence of a surge as in the prior art. It is possible to suppress a decrease in scavenging air pressure not only during stopping but also after stopping. Therefore, according to the present embodiment, the engine body 10 can be operated more efficiently than in the conventional case.

<Operating number increase control>
Subsequently, from the state where the main supercharger 20 is operated and the subsupercharger 30 is stopped, the subsupercharger 30 is operated while the main supercharger 20 is operated, and the number of superchargers operated is determined. The increasing control (control for increasing the number of operating units) will be described. FIG. 7 is a flowchart showing a method for controlling the number of operating units. The calculation and control described below are performed by the control device 60. FIG. 8 is a time chart showing the opening degrees of the auxiliary turbine inlet valve 41, the auxiliary compressor outlet valve 42, and the air discharge valve 43.

First, when the process is started, the control device 60 opens the sub turbine inlet valve 41 (step S11). Thereby, the exhaust gas is supplied to the auxiliary turbine 32 and the auxiliary supercharger 30 starts to operate. The sub compressor outlet valve 42 does not open simultaneously with the sub turbine inlet valve 41. This is because if the sub-compressor outlet valve 42 is opened with the sub-supercharger 30 having a low rotation speed and a low sub-compressor outlet pressure, the outside air increased in pressure by the main compressor 23 flows back to the sub-compressor 33.

Subsequently, the control device 60 reads signals transmitted from the engine tachometer 11, the fuel supply device 12, the sub-supercharger tachometer 36, and the sub-compressor outlet pressure gauge 37, and based on these signals, loads the engine load (engine (Estimated from rotation speed and fuel injection amount), sub-supercharger rotation speed, and sub-compressor outlet pressure are acquired (step S12).

Subsequently, the control device 60 determines the switching rotation speed (step S13). The “switching rotation speed” here is the sub-supercharger rotation speed when the sub-compressor outlet valve 42 starts to be opened. The switching speed is determined according to the engine load. Specifically, the control device 60 stores map data corresponding to the graph shown in FIG. 9, and determines the switching speed based on the acquired engine load. As shown in FIG. 9, the switching speed increases as the engine load increases.

Subsequently, the control device 60 determines whether or not the sub-supercharger rotation speed acquired in step S12 is equal to or higher than the switching rotation speed determined in step S13 (step S14). When it is determined that the sub-supercharger rotational speed is equal to or higher than the switching rotational speed (YES in step S14), the sub-compressor outlet valve 42 is opened (step S15), and then the process proceeds to step S16. On the other hand, when it is determined that the sub-supercharger rotational speed is smaller than the switching rotational speed (NO in step S14), the process proceeds to step S16 without passing through step S15.

Subsequently, the control device 60 determines an operating reference pressure based on the sub-supercharger rotation speed acquired in Step S12 (Step S16). The reference pressure during operation is a pressure having a predetermined amount of surge margin set in advance in the same manner as the reference pressure during stoppage (see step S3 in FIG. 3). The control device 60 stores data on the operation reference pressure for each sub-supercharger rotation speed. Therefore, the operating reference pressure can be determined based on the acquired sub supercharger rotation speed. In each sub-supercharger rotation speed, the reference pressure during operation and the reference pressure during stop may be set to the same value.

Subsequently, the control device 60 determines whether or not the sub compressor outlet pressure is larger than the operation reference pressure (step S17). That is, it is determined whether or not there is a risk of occurrence of a surge in the sub compressor 33. If it is determined that the sub compressor outlet pressure is equal to or lower than the operating reference pressure (NO in step S17), the process proceeds to step S18. That is, if it is determined that there is no possibility of a surge occurring in the sub compressor 33, the process proceeds to step S18. On the other hand, if it is determined that the sub compressor outlet pressure is greater than the operating reference pressure (YES in step S17), the process proceeds to step S19. That is, when it is determined that there is a possibility that a surge occurs in the sub compressor 33, the process proceeds to step S19.

When it is determined that there is no possibility of occurrence of a surge in the sub compressor 33, the control device 60 transmits a control signal to the air discharge valve 43 to decrease the opening degree of the air discharge valve 43. On the other hand, when it is determined that a surge may occur in the sub compressor 33 and the process proceeds to step S <b> 19, the control device 60 transmits a control signal to the air discharge valve 43 to increase the opening degree of the air discharge valve 43. In addition, when increasing the opening degree of the air discharge valve 43, the increase / decrease amount of the opening degree of the air discharge valve 43 is made small as the difference between the sub compressor outlet pressure and the reference pressure during operation becomes small.

Subsequently, after step S18 or S19, the control device 60 determines whether or not the sub compressor outlet valve 42 is fully opened (step S20). Whether or not the sub-compressor outlet valve 42 is fully opened can be determined by the fully closed / full-opening limit switch of the sub-compressor outlet valve 42, the time after the opening is started, or the like. If it is determined that the sub compressor outlet valve 42 is fully opened (YES in step S20), the process is terminated. On the other hand, when it is determined that the sub compressor outlet valve 42 is not fully opened (NO in step S20), the process returns to step S12 and steps S12 to S20 are repeated.

As described above, according to the operation number increase control of the present embodiment, the opening degree (including the fully closed position) of the discharge valve 43 is controlled to be as small as possible within a range where no surge occurs. Therefore, the outside air boosted by the auxiliary compressor 33 is suppressed from being discharged to the outside, and is supplied to the engine body 10 as scavenging gas as soon as the auxiliary compressor outlet valve 42 starts to open. Therefore, the scavenging pressure can be increased and the engine body 10 can be operated efficiently.

In the control for increasing the number of operating units of this embodiment, the timing for opening the auxiliary compressor outlet valve 42 is determined based on the engine load and the auxiliary supercharger rotation speed. However, the timing for opening the sub compressor outlet valve 42 is not limited to this. For example, as shown in FIG. 10, a differential pressure gauge 38 for measuring the differential pressure across the auxiliary compressor outlet valve 42 may be provided, and the timing for opening the auxiliary compressor outlet valve 42 may be determined based on the differential pressure before and after. Specifically, the sub compressor outlet valve 42 may be opened when the pressure on the upstream side of the sub compressor outlet valve 42 becomes higher than the pressure on the downstream side.

Further, as shown in FIG. 10, a scavenging meter 39 for measuring scavenging air pressure is provided between the air cooler 50 and the engine body 10, and when the differential pressure between the sub compressor outlet pressure and scavenging air pressure exceeds a predetermined threshold value, The sub compressor outlet valve 42 may be opened. Further, as the auxiliary compressor outlet valve 42, a check valve may be employed so that the outside air increased in pressure by the auxiliary compressor 33 flows to the engine body 10, but the outside air increased in pressure by the main compressor 23 does not flow to the auxiliary compressor 33.

(Second Embodiment)
Next, a second embodiment will be described. In this embodiment, the method for controlling the number of operating units is different from that in the first embodiment. Hereinafter, the operation number increase control of this embodiment will be described.

FIG. 11 is a flowchart showing a method of increasing the number of operating units according to this embodiment. FIG. 12 is a time chart showing the opening degree of the auxiliary turbine inlet valve 41, the auxiliary compressor outlet valve 42, and the air discharge valve 43, and the rotation speed of the auxiliary supercharger 30.

As shown in FIG. 11, when the process of increasing the number of operating units is started, the control device 60 starts opening the air discharge valve 43 so as to reach a predetermined opening degree (step S21), and after a predetermined time, the auxiliary device 43 Opening of the turbine inlet valve 41 is started (step S22). By starting to open the auxiliary turbine inlet valve 41, the auxiliary supercharger 30 starts to operate (see FIG. 12).

Subsequently, the control device 60 reads signals transmitted from the engine tachometer 11, the fuel supply device 12, and the sub-supercharger tachometer 36, and based on these signals, loads the engine load (engine speed and fuel injection amount). And the sub-supercharger rotation speed are acquired (step S23).

Subsequently, the control device 60 determines a first switching operation point (sub compressor flow rate and sub compressor outlet pressure) (step S24). The “first switching operation point” is an operation point of the sub compressor 33 having a predetermined surge margin, and is a point at which the air discharge valve 43 starts to close. Since the operating point of the sub-compressor 33 is greatly changed by opening and closing the air discharge valve 43, the operation curve (the locus of the operation point) of the sub-compressor 33 is different if the timing at which the air discharge valve 43 starts to close is different. In this embodiment, if the discharge valve 43 starts to close when the auxiliary compressor 33 reaches a certain operating point, a surge occurs immediately before the start of closing the discharge valve 43 and immediately before the opening of the auxiliary compressor outlet valve 42. No operating point that satisfies the condition that the operating curve does not reach the surge region is set as the first switching operating point. However, the first switching operation point changes according to the engine load. Note that the sub-compressor outlet pressure and the sub-compressor flow rate at the first switching operation point are set as a first switching pressure and a first switching flow rate, respectively (see FIG. 15). The control device 60 stores map data corresponding to the graph of the first switching pressure shown in FIG. 13, and determines the first switching pressure based on this map data and the engine load acquired in step S23. Similarly, the control device 60 stores map data corresponding to the graph of the first switching flow rate shown in FIG. 14, and determines the first switching flow rate based on the map data and the engine load acquired in step S23. . As shown in FIGS. 13 and 14, the first switching pressure and the first switching flow rate increase as the engine load increases.

Subsequently, the control device 60 determines the first switching rotational speed (step S25). In the present embodiment, the sub supercharger rotation speed of the pressure curve passing through the first switching operation point of the sub compressor 33 is set as the first switching rotation speed. For example, as shown in FIG. 15, when the pressure curve of the X% rotation speed passes through the point A which is the first switching operation point, the first switching rotation speed is set to X% rotation speed. Depending on the operating condition of the engine, the operating point of the sub compressor 33 when the sub supercharger rotation speed reaches the first switching rotation speed may be different from the first switching operation point. However, since the first switching operating point has a predetermined surge margin, even if the actual operating point slightly deviates from the first switching operating point, the sub compressor outlet valve 42 immediately before starting to close the discharge valve 43. The surge of the sub-compressor 33 can be avoided until just before starting to open.

Subsequently, the control device 60 determines whether or not the sub supercharger rotational speed is equal to or higher than the first switching rotational speed (step S26). When it is determined that the sub-supercharger rotational speed is equal to or higher than the first switching rotational speed (YES in step S26), the closing of the air discharge valve 43 is started (step S27; see FIG. 12). On the other hand, when it is determined that the sub-supercharger rotational speed is smaller than the first switching rotational speed (NO in step S26), the process returns to step S23 and steps S23 to S26 are repeated.

After starting the closing of the discharge valve 43 through step S27, the control device 60 reads signals transmitted from the engine tachometer 11, the fuel supply device 12, and the sub-supercharger tachometer 36 again. Based on this signal, the engine load and the sub-supercharger speed are acquired (step S28).

Subsequently, the control device 60 determines a second switching operation point (step S29). The “second switching operation point” is an operation point of the sub compressor 33 having a predetermined surge margin, and is a point at which the sub compressor outlet valve 42 starts to be opened. The second switching operation point is determined in the same manner as the first switching operation point. That is, if the auxiliary compressor outlet valve 42 starts to open when the auxiliary compressor 33 reaches a certain operating point, no surge will occur between immediately before the auxiliary compressor outlet valve 42 starts to open and to completion of opening (switching completion). The operating point that satisfies the condition that the operating curve does not reach the surge region is set as the second switching operating point. Similarly to the first switching operation point, the second switching operation point changes according to the engine load. The auxiliary compressor outlet pressure and the auxiliary compressor flow rate at the second switching operation point are set as the second switching pressure and the second switching flow rate, respectively (see FIG. 15). The control device 60 determines the second switching pressure and the second switching flow rate based on the graph of the second switching pressure shown in FIGS. 13 and 14, the map data corresponding to the second switching flow rate, and the engine load. When the engine load is the same, the second switching pressure and the second switching flow rate are determined to be higher than the first switching pressure and the first switching flow rate, respectively.

Subsequently, the control device 60 determines the second switching rotation speed (step S30). As in the case of the first switching speed, the sub-supercharger speed of the pressure curve passing through the second switching operating point of the sub-compressor 33 is set as the second switching speed. For example, as shown in FIG. 15, when the pressure curve of the Y% rotation speed passes through the point B that is the second switching operation point, the second switching rotation speed is set to Y% rotation speed. Since the second switching pressure and the second switching flow rate are larger than the first switching pressure and the first switching flow rate, respectively, the second switching rotational speed is higher than the first switching rotational speed. Further, depending on the operating condition of the engine, the operating point of the sub compressor when the sub supercharger rotational speed reaches the second switching rotational speed may be different from the second switching operating point. However, since the second switching operation point has a predetermined surge margin, even if the actual operation point is slightly deviated from the second switching operation point, the time from immediately before the sub compressor outlet valve 42 is opened to until the opening is completed. During this time, the surge of the sub compressor 33 can be avoided.

Subsequently, the control device 60 determines whether or not the sub-supercharger rotation speed is equal to or higher than the second switching rotation speed (step S31). When it is determined that the sub-supercharger rotational speed is equal to or higher than the second switching rotational speed (YES in step S31), the opening of the sub-compressor outlet valve 42 is started (step S32; see FIG. 12), and the processing thereafter Exit. On the other hand, when it is determined that the sub-supercharger rotational speed is smaller than the second switching rotational speed (NO in step S31), the process returns to step S28 and steps S28 to S31 are repeated.

The operation number increase control of this embodiment is as described above. By performing the operation number increase control as described above, as shown in FIG. 12, after the sub-turbine inlet valve 41 is opened in a state where the discharge valve 43 is opened at a predetermined opening, the discharge valve 43 starts to be closed, and thereafter the opening of the sub compressor outlet valve 42 is started. In other words, since the opening of the sub compressor outlet valve 42 is started with the air discharge valve 43 closed to some extent, it is possible to prevent the outside air boosted by the sub compressor 33 from being released to the outside through the air discharge valve 43. it can. In addition, since the outside air is sufficiently boosted by the sub compressor 33, it is possible to suppress the outside air boosted by the main compressor 23 from flowing back to the sub compressor 33. Therefore, it can suppress that the efficiency of the engine main body 10 falls. In addition, in the control for increasing the number of operating units according to the present embodiment, the opening and closing of the sub compressor outlet valve 42 and the air discharge valve 43 are controlled based on the sub supercharger rotation speed, and therefore acquisition of the sub compressor outlet pressure is omitted. Can do. Therefore, for example, when the auxiliary compressor outlet pressure gauge 37 in FIG. 1 is not used not only in the operating unit increase control but also in the operating unit decrease control, such as performing the operating unit decrease control based on the time schedule, Can be omitted.

In the above description, it has been described that when it is determined that the sub-supercharger rotational speed is equal to or higher than the first switching rotational speed, the air discharge valve 43 starts to be closed (steps S26 and S27). The speed at which the wind valve 43 is closed, that is, the decrease rate (change rate) of the opening degree of the discharge valve 43 may not be constant. For example, the speed at which the air discharge valve 43 is closed may be increased as the difference between the sub-supercharger rotation speed and the first switching rotation speed is increased, that is, the amount of decrease in the opening degree of the air discharge valve 43 may be increased. According to such a configuration, when the possibility of occurrence of a surge in the sub compressor 33 is low, the air discharge valve 43 can be closed more quickly, so that a decrease in the efficiency of the engine body 10 can be further suppressed.

(Third embodiment)
Next, a third embodiment will be described. The present embodiment is obtained by adding a predetermined step to the operation number increase control in the second embodiment. The following description will focus on the differences of this embodiment from the second embodiment.

FIG. 16 is a schematic configuration diagram of the entire engine system 200 according to the present embodiment. As shown in FIG. 16, in the engine system 200 according to the present embodiment, the main scavenging pipe 25 is provided with a main compressor outlet pressure gauge 40, but otherwise, the first embodiment and the second embodiment shown in FIG. 1. This is the same configuration as the engine system 100 according to FIG. The main compressor outlet pressure gauge 40 is located on the outlet side of the main compressor 23 and upstream of the air cooler 50. The main compressor outlet pressure gauge 40 is electrically connected to the control device 60, and the control device 60 acquires the main compressor outlet pressure based on a signal transmitted from the main compressor outlet pressure gauge 40.

FIG. 17 is a flowchart showing a method for controlling the number of operating units of the present embodiment, and corresponds to FIG. 11 of the second embodiment. As can be seen by comparing FIG. 17 and FIG. 11, the operation number increase control of this embodiment is obtained by adding steps S41 and S42 to the operation number increase control of the second embodiment. In the second embodiment, when the control device 60 determines in step S29 that the sub-supercharger rotation speed is equal to or higher than the second switching rotation speed, the sub-compressor outlet valve 42 has started to be opened. If it is determined in step S31 that the sub supercharger rotational speed is equal to or higher than the second switching rotational speed, the process proceeds to step S41 without immediately starting to open the sub compressor outlet valve 42.

In step S41, the control device 60 reads a signal transmitted from the main compressor outlet pressure gauge 40, and acquires the main compressor outlet pressure based on this signal.

Subsequently, the control device 60 determines whether or not the main compressor outlet pressure acquired in step S41 is equal to or lower than the second switching pressure used when determining the second switching operating point in step S29 (step S42). ). If the main compressor outlet pressure is equal to or lower than the second switching pressure (YES in step S42), opening of the sub compressor outlet valve 42 is started (step S32), and then the process is terminated. On the other hand, when it is determined that the main compressor outlet pressure is greater than the second switching pressure (NO in step S42), the process returns to step S28 and steps S28 to S31, S41, and S42 are repeated.

As described above, in the present embodiment, in addition to the sub-supercharger rotational speed being equal to or higher than the second switching rotational speed, when the main compressor outlet pressure is equal to or lower than the second switching pressure, the auxiliary compressor outlet valve 42 is not turned on for the first time. Start opening.

Here, even if the ship navigates at a constant speed, the engine load may fluctuate greatly depending on the sea conditions. Although the main compressor outlet pressure is controlled to decrease when the engine load decreases, it takes some time until the main compressor outlet pressure decreases after the engine load decreases. Therefore, when the operation number increase control is performed at the same time as the engine load is reduced, the main compressor outlet pressure is still in a high state, so that the outside air boosted by the main compressor 23 may flow back to the sub compressor 33 side.

In contrast, in this embodiment, the opening of the sub compressor outlet valve 42 is started only when the main compressor outlet pressure is equal to or lower than the second switching pressure. Originally, the opening of the sub compressor outlet valve 42 is started when the sub compressor outlet pressure becomes the second switching pressure, so that the sub compressor outlet pressure when the opening of the sub compressor outlet valve 42 is started is changed to the second switching pressure. Pressure. Therefore, as in the present embodiment, if the main compressor outlet pressure is equal to or lower than the second switching pressure, the main compressor outlet pressure is smaller than the sub compressor outlet pressure when the opening of the sub compressor outlet valve 42 is started. . Therefore, according to this embodiment, even when the engine load fluctuates, the outside air boosted by the main compressor 23 does not flow back to the sub compressor 33 side.

In the present embodiment, the main compressor outlet pressure is acquired using the main compressor outlet pressure gauge 40. For example, a scavenging pressure gauge (see reference numeral 39 in FIG. 10) is provided downstream of the air cooler 50 of the main scavenging pipe 25. The main compressor outlet pressure may be acquired (estimated) based on the scavenging pressure measured by the scavenging pressure gauge. This also applies to the case of a fourth embodiment described later.

(Fourth embodiment)
Next, a fourth embodiment will be described. The present embodiment is different from the second embodiment in the method of determining the first switching rotation speed and the second switching rotation speed. Hereinafter, the determination method of the first switching rotation speed and the second switching rotation speed in the present embodiment will be mainly described.

The overall configuration of the engine system according to the present embodiment is basically the same as the engine system 200 of the third embodiment shown in FIG. That is, in the engine system according to this embodiment, the main compressor outlet pressure gauge 40 is provided in the main scavenging piping 25.

FIG. 18 is a flowchart showing a method for controlling the number of operating units of the present embodiment, and corresponds to FIG. 11 of the second embodiment. As can be seen from a comparison between FIG. 18 and FIG. 11, the operation number increase control of the present embodiment changes steps S23, S28, and S29 of the operation number increase control of the second embodiment to steps S51, S53, and S54. Step S52 is added.

In the second embodiment, after passing through step S22, the engine load and the sub-supercharger speed are acquired (see step S23 in FIG. 11). In this embodiment, the main compressor outlet pressure gauge 40 and the sub-supercharger are obtained. The signals transmitted from the tachometer 36 are read, and the “main compressor outlet pressure” and the sub-supercharger rotation speed are acquired based on these signals (step S51). Thereafter, the control device 60 estimates the engine load based on the main compressor outlet pressure acquired in step S51 (step S52). Specifically, the control device 60 stores map data corresponding to the graph shown in FIG. 19, and estimates the engine load based on this map data and the acquired compressor outlet pressure. As shown in FIG. 19, the estimated engine load increases as the compressor outlet pressure increases.

Thereafter, similarly to the second embodiment, the first switching operation point is determined based on the estimated engine load (step S24), and the first switching rotational speed is determined (step S24). Although there is a slight error between the engine load estimated in step S52 and the actual engine load, as described above, the first switching operating point has a predetermined surge margin. Even if the actual operating point slightly deviates from the first switching operating point, it is possible to avoid the surge of the sub compressor 33 from immediately before the start of closing the air discharge valve 43 to just before starting to open the sub compressor outlet valve 42. .

In this embodiment, after passing through step S27, the main compressor outlet pressure and the sub-supercharger rotation speed are acquired in the same manner as in step S51 (step S53). Thereafter, the control device 60 determines the second switching operation point (step S54). Specifically, the control device 60 sets a value equal to the main compressor outlet pressure acquired in step S53 as the second switching pressure. A value obtained by adding a predetermined flow rate (margin flow rate) to the flow rate of the sub-compressor 33 that generates a surge at the second switching pressure is defined as a second switching flow rate. Further, an operating point at which the sub compressor outlet pressure is the second switching pressure and the sub compressor flow rate is the second switching flow rate is defined as a second switching operating point. That is, as shown in FIG. 20, a point C which is the point (surge point) of the second switching pressure (main compressor outlet pressure) in the surge line is taken, and the auxiliary compressor flow rate is increased from this point C by a predetermined margin flow rate. The point D shifted to the side is set as the second switching operation point.

Subsequently, in step S30 of FIG. 18, the sub-supercharger rotation speed of the pressure curve passing through the second switching operation point of the sub-compressor 33 is set as the second switching rotation speed. For example, as shown in FIG. 20, when the pressure curve of the Z% rotation speed passes through the point D that is the second switching operation point, the second switching rotation speed is set to the Z% rotation speed. The processing (steps S31 and S32) after determining the second switching rotational speed is the same as in the second embodiment.

In addition, the value of the above margin flow rate is not particularly limited. The margin flow rate may be constant or may be varied such as increasing as the main compressor outlet pressure increases. In the above description, the point D shifted from the surge point C to the increase side of the auxiliary compressor flow rate by a predetermined margin flow rate is set as the second switching operation point. However, the direction of the shift is the increase direction of the auxiliary compressor flow rate. Not limited to only. For example, the second switching operation point may be a point that is shifted from the surge point (point C) by a predetermined margin flow rate toward the increase side of the sub compressor flow rate and shifted by a predetermined margin pressure toward the decrease side of the sub compressor pressure. .

As described above, in the present embodiment, the first switching rotational speed and the second switching rotational speed are determined based on the main compressor outlet pressure instead of the engine load, and the sub supercharger rotational speed is equal to or higher than the first switching rotational speed. At a certain time, closing of the air discharge valve 43 is started, and when the rotation speed is equal to or higher than the second switching rotational speed, opening of the sub compressor outlet valve 42 is started. As described above, the timing for closing the air discharge valve 43 and the timing for opening the sub compressor outlet valve 42 are not affected by the engine load, and thus are effective when the operation number increase control is performed in a situation where the engine load varies. Further, when the engine load is not used not only in the operation number increase control but also in the operation number decrease control, such as the operation number decrease control according to the first embodiment, the control device 60, the engine tachometer 11 and the fuel in FIG. The connection with the supply device 12 can be omitted.

The first to fourth embodiments have been described above. Although the case where the engine systems 100 and 200 include one main supercharger 20 and one sub-supercharger 30 has been described above, the engine systems 100 and 200 include a plurality of main superchargers 20. Alternatively, a plurality of sub-superchargers 30 may be provided. For example, in the first embodiment, the engine system 100 may include one main supercharger 20 and two auxiliary superchargers 30 as shown in FIG.

According to the engine system of the present invention, it is possible to prevent the efficiency of the engine body from being lowered when changing the number of operating superchargers while preventing surges from occurring in the supercharger. . Therefore, it is useful in the technical field of an engine system that changes the number of superchargers operated in accordance with the operating conditions.

DESCRIPTION OF SYMBOLS 10 Engine main body 20 Main supercharger 22 Main turbine 23 Main compressor 30 Subsupercharger 32 Subturbine 33 Subcompressor 41 Subturbine inlet valve 42 Subcompressor outlet valve 43 Air discharge valve 44 Air discharge piping 60 Control apparatus 100, 200 Engine system

Claims (12)

1. The engine body,
   At least one main turbocharger having a main turbine and a main compressor;
   At least one sub-supercharger disposed in parallel with the main supercharger with respect to the engine body and having a sub-turbine and a sub-compressor;
   A sub-turbine inlet valve provided on the inlet side of the sub-turbine;
   An auxiliary compressor outlet valve provided on the outlet side of the auxiliary compressor;
   A discharge pipe for guiding outside air boosted by the sub compressor from the upstream side of the sub compressor outlet valve to the outside;
   A discharge valve provided in the discharge pipe;
   A control device,
   The controller is
   From the state in which the main turbocharger and the subsupercharger are operated, the subturbine is stopped by closing the subturbine inlet valve and the subcompressor outlet valve while operating the main supercharger, When reducing the number of operating turbochargers,
   Determining a stop-time reference pressure having a predetermined surge margin based on the sub-supercharger rotation speed, and increasing the opening of the discharge valve when the sub-compressor outlet pressure is higher than the stop-time reference pressure; An engine system configured to decrease the opening degree of the air discharge valve when a sub compressor outlet pressure is lower than the stop-time reference pressure.
2. The controller is configured to reduce the increase amount of the opening of the air discharge valve as the difference between the sub compressor outlet pressure and the stop-time reference pressure is smaller when increasing the opening of the air discharge valve. The engine system according to claim 1.
3. The engine body,
   At least one main turbocharger having a main turbine and a main compressor;
   At least one sub-supercharger disposed in parallel with the main supercharger with respect to the engine body and having a sub-turbine and a sub-compressor;
   A sub-turbine inlet valve provided on the inlet side of the sub-turbine;
   An auxiliary compressor outlet valve provided on the outlet side of the auxiliary compressor;
   A discharge pipe for guiding outside air boosted by the sub compressor from the upstream side of the sub compressor outlet valve to the outside;
   A discharge valve provided in the discharge pipe;
   A control device,
   The controller is
   The sub-supercharger is operated by opening the sub-turbine inlet valve and the sub-compressor outlet valve while operating the main supercharger from the state where the main supercharger is operated and the sub-supercharger is stopped. And increase the number of turbochargers
   An operating reference pressure having a predetermined surge margin is determined based on the sub-supercharger rotational speed, and when the sub-compressor outlet pressure is higher than the operating reference pressure, the opening of the discharge valve is increased, An engine system configured to reduce the opening degree of the discharge valve when a sub compressor outlet pressure is lower than a reference pressure during operation.
4. When increasing the opening degree of the discharge valve, the control device reduces the increase amount of the opening degree of the discharge valve as the difference between the outlet pressure of the sub-compressor and the reference pressure during operation decreases. The engine system according to claim 3, which is configured.
5. The controller, when increasing the number of operating turbochargers, starts opening the auxiliary turbine inlet valve, and then the auxiliary compressor outlet valve when the auxiliary turbocharger rotational speed becomes equal to or higher than a predetermined switching rotational speed. The engine system according to claim 3 or 4, wherein opening of the engine is started and the switching rotational speed is determined according to an engine load.
6. The engine body,
   At least one main turbocharger having a main turbine and a main compressor;
   At least one sub-supercharger disposed in parallel with the main supercharger with respect to the engine body and having a sub-turbine and a sub-compressor;
   A sub-turbine inlet valve provided on the inlet side of the sub-turbine;
   An auxiliary compressor outlet valve provided on the outlet side of the auxiliary compressor;
   A discharge pipe for guiding outside air boosted by the sub compressor from the upstream side of the sub compressor outlet valve to the outside;
   A discharge valve provided in the discharge pipe;
   A control device,
   The controller is
   The sub-supercharger is operated by opening the sub-turbine inlet valve and the sub-compressor outlet valve while operating the main supercharger from the state where the main supercharger is operated and the sub-supercharger is stopped. And increase the number of turbochargers
   After the opening of the auxiliary turbine inlet valve with the opening of the discharging valve opened at a predetermined opening degree, the discharging valve when the auxiliary supercharger rotational speed becomes equal to or higher than a predetermined first switching rotational speed Is configured to start opening the sub compressor outlet valve when the sub supercharger rotational speed becomes equal to or higher than a second switching rotational speed greater than the first switching rotational speed. Engine system.
7. The control device determines a first switching operation point of the sub-compressor having a predetermined surge margin based on an engine load, and determines a sub-supercharger rotation speed of a pressure curve passing through the first switching operation point. The engine system according to claim 6, wherein the engine system is configured to have one switching speed.
8. The control device determines a second switching operation point of the sub-compressor having a predetermined surge margin based on an engine load, and determines a sub-supercharger rotation speed of a pressure curve passing through the second switching operation point. The engine system according to claim 6 or 7, wherein the engine system is configured to have two switching speeds.
9. The controller acquires the main compressor outlet pressure when increasing the number of operating superchargers, the sub-supercharger rotation speed is equal to or higher than the second switching rotation speed, and the acquired main compressor outlet pressure is The engine system according to claim 8, wherein the engine system is configured to start opening the sub compressor outlet valve when the pressure is lower than the sub compressor outlet pressure at the second switching operation point.
10. The control device acquires a main compressor outlet pressure, sets a value equal to the acquired main compressor outlet pressure as a second switching pressure, and sets a value obtained by adding a predetermined flow rate to a sub compressor flow rate at which a surge occurs at the second switching pressure. The second switching flow rate, the operating point at the second switching pressure and the second switching flow rate as the second switching operating point, and the sub-supercharger rotation speed of the pressure curve passing through the second switching operating point is the The engine system according to claim 6, wherein the engine system is configured to have a second switching speed.
11. The control device estimates an engine load based on the acquired main compressor outlet pressure, determines a first switching operating point of the sub compressor having a predetermined surge margin based on the estimated engine load, and performs the first switching The engine system according to claim 10, wherein the engine system is configured such that a sub-supercharger rotational speed of a pressure curve passing through an operating point is the first switching rotational speed.
12. The control device is configured to reduce the amount of decrease in the opening degree of the air discharge valve as the difference between the sub-supercharger rotation speed and the first switching rotation speed decreases when the air discharge valve is closed. The engine system according to any one of claims 6 to 11.

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