JP2015108312A - Engine system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine system ensuring safe stop at a time of quick stop of the engine system.SOLUTION: An engine system 100 according to the present invention includes: an engine main body 10; a supercharger 20 including a turbine 21 and a compressor 22; an exhaust gas channel 30 introducing exhaust gas from the engine main body 10 to the turbine 21; a supply channel 40 introducing supply gas from the compressor 22 of the supercharger 20 to the engine main body 10; an EGR channel 50 extracting part of the exhaust gas from upstream of the turbine 21 and introducing the extracted exhaust gas to the engine main body 10; an EGR blower 60 provided in the EGR channel 50 for increasing a pressure of the extracted exhaust gas; and a safe stop mechanism 80 avoiding excessive rotation of the supercharger 20 after quick stop of the engine system 100.

Description

  The present invention relates to a large engine system including an internal combustion engine such as a marine or power generation diesel engine or gas engine, and more particularly to an engine system having a relatively complicated structure including a supercharger and an EGR blower.

  In recent years, as with automobiles, NOx emission regulations tend to be strengthened for ships and the like. As a method of suppressing the generation of NOx, there is an exhaust gas recirculation (hereinafter referred to as “EGR”) that returns a part of the exhaust gas discharged from the engine body to the combustion chamber and reduces the oxygen concentration in the cylinder. is there. By recirculating the exhaust gas to the engine body, the oxygen concentration is reduced, the combustion temperature is suppressed, and the generation of NOx can be suppressed (see Patent Document 1).

  When performing EGR with a large engine system, the structure is similar to that of a car engine that performs EGR in the same way, including a turbocharger and an EGR blower for boosting exhaust gas (EGR gas). It becomes complicated. For this reason, the EGR technology adopted in automobiles cannot be applied to a large engine system as it is. In addition, EGR for large engine systems is a technology that has been developed in accordance with the recent tightening of NOx emission regulations, and is relatively new, and is currently being studied for practical use.

JP 2011-157959 A

  One of the matters that should be considered for the practical use of a large engine system that performs EGR is the behavior of the engine system in a sudden change in the situation. In particular, the inventors of the present invention have paid attention to a technique for safely stopping an engine system when the engine system is suddenly stopped due to a forced stop or power failure due to abnormality detection.

  The present invention has been made in view of such circumstances, and provides an engine system having a complicated structure including a supercharger and an EGR blower, and capable of performing a safe stop in the case of a sudden stop. For the purpose.

  An engine system according to an aspect of the present invention includes an engine main body, a supercharger having a turbine part and a compressor part, an exhaust passage for introducing exhaust gas from the engine main body to the turbine part of the supercharger, and the supercharger. A supply flow path for introducing supply gas from the compressor section of the feeder to the engine body, an EGR flow path for extracting a part of exhaust gas from upstream of the turbine section and leading to the engine body, and the EGR flow path And an EGR blower that boosts the extracted exhaust gas, and further includes a safety stop mechanism that avoids excessive rotation of the supercharger after the engine system is suddenly stopped.

  Here, even after a sudden stop of the engine system, the engine body continues to rotate due to inertial energy and discharges air to the exhaust passage. The EGR blower also rotates in the same manner, but the rotation stops earlier than the engine body because the inertia is small. If it does so, all the air which was flowing into the EGR channel will flow into the turbine part of a supercharger, and there exists a possibility that a supercharger may be overrotated and may be damaged. On the other hand, according to the configuration of the engine system described above, since the turbocharger is prevented from over-rotating after the engine system is suddenly stopped, the engine system can be safely stopped when the engine system is suddenly stopped.

  In the engine system, the safety stop mechanism may include a safety stop control unit that drives the EGR blower for a predetermined time after the engine system suddenly stops. According to such a configuration, air continues to flow through the EGR flow path even after the engine system is suddenly stopped. Therefore, it is possible to suppress the amount of air flowing to the supercharger and to avoid excessive rotation of the supercharger.

  In the above engine system, the safety stop control unit may gradually reduce the rotational speed of the EGR blower after the engine system suddenly stops. According to such a configuration, unnecessary rotation of the EGR blower can be suppressed.

  In the engine system, the safety stop control unit is configured to control the EGR blower after a sudden stop of the engine system based on one or both of the rotation speed of the turbocharger and the suction pressure of the turbine unit of the turbocharger. The number of rotations may be determined. According to such a configuration, it is possible to prevent the EGR blower from rotating more than necessary while avoiding excessive rotation of the supercharger.

  In the engine system, the EGR blower may be driven by an electric motor, and the engine system may include a power storage device that stores electric power in advance and supplies electric power to the electric motor at the time of a power failure. According to such a configuration, it is possible to stop safely even during a power failure.

  In the engine system described above, the EGR blower is driven by a hydraulic motor, and the engine system includes a pressure accumulating device that accumulates hydraulic oil that has been boosted in advance and supplies the hydraulic fluid that has been boosted to the hydraulic motor in the event of a power failure. May be. Even in such a configuration, it can be safely stopped in the event of a power failure.

  In the above engine system, the safety stop mechanism includes a bypass passage that branches from the exhaust passage, and a bypass valve that is provided in the bypass passage and is opened after the engine system is suddenly stopped. Also good. According to such a configuration, since the amount of air flowing into the turbine portion of the supercharger after the engine system is suddenly stopped can be reduced, it is possible to avoid excessive rotation of the supercharger.

  In the engine system described above, the safety stop mechanism is configured so that the bypass valve of the bypass valve after a sudden stop of the engine system is based on one or both of the rotational speed of the supercharger and the suction pressure of the turbine section of the supercharger. You may further have the safe stop control part which determines opening and closing or an opening degree. According to this configuration, it is possible to perform more accurate control.

  In the engine system, the supercharger includes a variable nozzle provided at an inlet of the turbine unit, and the safety stop mechanism is configured to reduce the efficiency of the turbine unit after a sudden stop of the engine system. You may have the safe stop control part which adjusts the nozzle area of a variable nozzle. According to such a configuration, since the efficiency of the supercharger can be reduced after the engine system suddenly stops, it is possible to avoid overspeeding of the supercharger.

  In the engine system, the safety stop control unit may be configured such that the variable nozzle after a sudden stop of the engine system is based on one or both of the rotation speed of the turbocharger and the suction pressure of the turbine unit of the turbocharger. The nozzle area may be determined. According to this configuration, it is possible to perform more accurate control.

  The engine system includes a plurality of superchargers, and the safety stop mechanism is provided at an inlet of a turbine section of at least one supercharger, and suddenly stops when the engine system is in a closed state when the engine system is suddenly stopped. You may have the on-off valve opened later. According to this configuration, it is possible to reduce the amount of air that flows into the turbine section of the supercharger that was being driven when the engine system was suddenly stopped, and thus it is possible to avoid excessive rotation of the supercharger.

  According to the engine system described above, it is possible to avoid over-rotation of the supercharger at the time of sudden stop, so that safe stop can be performed.

FIG. 1 is a block diagram of an engine system according to the first embodiment. FIG. 2 is a flowchart of control of the EGR blower shown in FIG. FIG. 3 is a flowchart of another control of the EGR blower shown in FIG. FIG. 4 is a diagram showing the relationship between the measured rotational speed and the first deceleration value and the relationship between the measured suction pressure and the second deceleration value in FIG. FIG. 5 is a block diagram of an engine system according to a modification of FIG. FIG. 6 is a block diagram of an engine system according to the second embodiment. FIG. 7 is a flowchart of control of the bypass valve shown in FIG. FIG. 8 is a block diagram of an engine system according to the third embodiment. FIG. 9 is a flowchart of control of the variable nozzle shown in FIG. FIG. 10 is a block diagram of an engine system according to the fourth embodiment.

  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)
<Overall configuration of engine system>
First, the engine system 100 according to the first embodiment will be described. FIG. 1 is a block diagram of the engine system 100. A thick solid line in FIG. 1 indicates the flow of the supply gas supplied to the engine main body 10, and a thick broken line indicates the flow of the exhaust gas discharged from the engine main body 10. As will be described later, since the engine body 10 of the present embodiment is a two-stroke engine, the “supply gas” is a so-called “scavenging gas”. However, when the engine body 10 is a four-stroke engine, it becomes a so-called “supply gas”.

  The engine system 100 according to the present embodiment is mounted on a large ship, and includes an engine body 10, a supercharger 20, an exhaust passage 30, a supply passage 40, an EGR passage 50, An EGR blower 60 and a control device 70 are provided. Hereinafter, each of these components will be described in order.

  The engine body 10 in the present embodiment is a main propulsion unit for a ship and is a two-stroke diesel engine. However, the engine body 10 may be a 4-stroke engine or a gas engine. Further, the engine body 10 is not limited to the one used in the marine vessel propulsion device, but may be one used in the power generation facility or the like.

  The supercharger 20 is a device that boosts fresh air taken from outside and supplies it to the engine body 10. The supercharger 20 has a turbine part 21 and a compressor part 22. The turbine unit 21 is rotated by the energy of exhaust gas discharged from the engine body 10. The turbine part 21 and the compressor part 22 are connected by a shaft part 23, and the compressor part 22 also rotates as the turbine part 21 rotates. Further, the supercharger 20 is provided with a tachometer 24 that measures the rotation speed of the supercharger 20 and a pressure gauge 25 that measures the suction pressure at the inlet of the turbine section 21.

  The exhaust passage 30 is a passage that connects the engine body 10 and the turbine section 21 of the supercharger 20 and guides exhaust gas discharged from the engine body 10 to the turbine section 21 of the supercharger 20.

  The supply flow path 40 connects the engine body 10 and the compressor unit 22 of the supercharger 20, and a flow for introducing fresh air (supply gas) boosted by the compressor unit 22 of the supercharger 20 to the engine body 10. Road.

  The EGR flow path 50 is a flow path that extracts a part of the exhaust gas from the upstream side of the turbine section 21 and guides it to the engine body 10. In addition, there is EGR (low pressure EGR) in which exhaust gas is extracted from the downstream of the turbine unit 21 and returned to the upstream of the compressor unit 22, but the exhaust gas is extracted from the upstream of the turbine unit 21 as in this embodiment. EGR (high pressure EGR) is effective in reducing the size of the engine system 100 because the exhaust gas can be handled with a small volume. In this embodiment, the EGR flow path 50 is branched from the exhaust flow path 30 and connected to the supply flow path 40. However, exhaust gas is directly extracted from the engine body 10 via an exhaust pipe (not shown). Alternatively, the exhaust gas may be directly supplied to the engine body 10 via a scavenging pipe (not shown).

  The EGR blower 60 is disposed in the EGR flow path 50 and is a device that boosts the extracted exhaust gas (EGR gas) and supplies it to the engine body 10. The EGR blower 60 is driven by an EGR drive motor 61. The EGR drive motor 61 of this embodiment is a so-called electric motor. Electric power is supplied to the EGR drive motor 61 through a blower control panel 63 from a power supply device 62 such as a generator mounted on the hull. The engine system 100 according to this embodiment includes a power storage device 64 such as an uninterruptible power supply (UPS) between the power supply device 62 and the blower control panel 63. Therefore, even when power is not supplied from the power supply device 62, that is, when a power failure occurs, power is supplied to the EGR drive motor 61 for a predetermined time after the power failure by the power stored in the power storage device 64.

  The control device 70 is a device that controls the entire engine system 100 and includes a CPU, a ROM, a RAM, and the like. The control device 70 is electrically connected to the tachometer 24 and the pressure gauge 25. The control device 70 acquires the rotational speed of the supercharger 20 and the suction pressure at the inlet of the turbine unit 21 of the supercharger 20 based on the measurement signals transmitted from these instruments. The control device 70 is electrically connected to the blower control panel 63 and transmits a control signal to the blower control panel 63 to control the EGR blower 60. The control device 70 has a safe stop control unit 71 as a functional configuration. In the present embodiment, the safety stop mechanism 80 is configured by the safety stop control unit 71.

<Behavior when engine system suddenly stops>
Here, the behavior when the engine system 100 is suddenly stopped will be described. The sudden stop of the engine system 100 here includes a forced stop of the engine system 100 due to detection of an emergency stop factor (a decrease in lubricating oil pressure or an excessive rotation of the engine body) and a stop of the engine system 100 due to a power failure. In the conventional forced stop control, the fuel supply to the engine body 10 is stopped, and at the same time, the rotary drive device such as a motor is also stopped. Therefore, according to the conventional control, when the forced stop is performed, the EGR drive motor 61 (EGR blower 60) is also stopped. Further, at the time of a power failure, the fuel pump stops and fuel is not supplied to the engine body 10, and the EGR drive motor 61 (EGR blower 60) also stops. However, in the case of a ship, an auxiliary power supply device (such as a DC24V power supply backed up by a battery) is activated during a power failure, and a control device, a control valve, an actuator, The sensors can be operated for a predetermined period (for example, 30 minutes).

  As described above, when the engine system 100 is suddenly stopped, the fuel supply to the engine body 10 is stopped. However, even after the engine system 100 is suddenly stopped, the engine body 10 rotates for a while due to inertial energy, and air is discharged into the exhaust passage 30. The EGR blower 60 also rotates for a while after the engine system 100 is suddenly stopped. However, since the inertia is smaller than that of the engine body 10, the EGR blower 60 stops rotating earlier than the engine body 10. When the rotation of the EGR blower 60 stops, all of the air discharged from the engine body 10 that has flowed into the EGR flow path 50 flows to the supercharger 20 via the exhaust flow path 30. As a result, the supercharger 20 is over-rotated and there is a risk of breakage.

  Based on the above, the safety stop mechanism 80 is configured to avoid over-rotation of the supercharger 20 after the engine system 100 suddenly stops. By providing this safety stop mechanism 80, the engine system 100 can be safely stopped when the engine system 100 is suddenly stopped. In the case of the present embodiment, the safe stop control unit 71 configuring the safe stop mechanism 80 drives the EGR blower 60 for a predetermined time after the engine system 100 suddenly stops. As a result, the air exhausted from the engine body 10 after the engine system 100 has stopped suddenly can continue to flow through the EGR flow path 50. Therefore, it is possible to suppress an increase in the air supplied to the turbine unit 21 of the supercharger 20 and to prevent the supercharger 20 from over-rotating.

<Control method 1 of EGR blower>
Next, a specific control method of the EGR blower 60 will be described. In the present embodiment, the EGR blower 60 is driven for a predetermined time from the sudden stop of the engine system 100 as described above, but the rotational speed may be constant or may be reduced at a constant rate. However, in this embodiment, the rotational speed of the EGR blower 60 is determined by the control method shown in FIG. FIG. 2 is a flowchart showing a method for controlling the EGR blower 60 after the engine system 100 is suddenly stopped. This control is performed by the safe stop control unit 71.

  First, the safety stop control unit 71 acquires the rotational speed of the supercharger 20 (hereinafter referred to as “measured rotational speed”) and the suction pressure at the inlet of the turbine unit 21 (hereinafter referred to as “measured suction pressure”). (Step S1). Note that the rotation speed of the EGR blower 60 at the start of control is the rotation speed immediately before the engine system 100 is suddenly stopped.

  Subsequently, the safe stop control unit 71 determines whether or not the measured rotational speed is smaller than a preset dangerous rotational speed (step S2). When the measured rotational speed is smaller than the critical rotational speed (YES in step S2), the process proceeds to step S4. When the measured rotational speed is equal to or higher than the critical rotational speed (NO in step S2), the process proceeds to step S3. Here, the “dangerous rotation speed” is the rotation speed of the supercharger 20 when there is a possibility that the supercharger 20 is over-rotated.

  In step S <b> 3, the safety stop control unit 71 transmits a predetermined control signal to the blower control panel 63 and maintains the rotational speed of the EGR blower 60 as it is. As described above, when the measured rotational speed is larger than the critical rotational speed, that is, when there is a possibility that the supercharger 20 is over-rotated, the current rotational speed is maintained without reducing the rotational speed of the EGR blower 60. .

  In step S4, the safe stop control unit 71 determines whether or not the measured suction pressure is smaller than a preset dangerous suction pressure. When the measured suction pressure is smaller than the dangerous suction pressure (YES in step S4), the process proceeds to step S5. When the measured suction pressure is higher than the dangerous suction pressure (NO in step S4), the process proceeds to step S3. Here, the “dangerous suction pressure” is a suction pressure at the inlet of the turbine section 21 when the turbocharger 20 may be over-rotated. In the present embodiment, assuming that the downstream side of the turbine unit 21 of the turbocharger 20 is open to the atmosphere via a funnel (chimney), the supercharger 20 is based on the suction pressure of the turbine unit 21. Although it is determined whether or not there is a possibility of over-rotation, if any device is provided on the downstream side of the turbine unit 21 of the supercharger, the suction pressure and discharge pressure of the turbine unit 21 The determination may be performed based on the differential pressure.

  In step S3, as described above, the safety stop control unit 71 transmits a predetermined control signal to the blower control panel 63, and maintains the rotational speed of the EGR blower 60 as it is. As described above, when the measured suction pressure is equal to or higher than the dangerous suction pressure, that is, when there is a possibility that the supercharger 20 is over-rotated, the current rotational speed is maintained without reducing the rotational speed of the EGR blower 60.

  In step S5, the safe stop control unit 71 transmits a predetermined control signal to the blower control panel 63, and reduces the rotational speed of the EGR blower 60 by a certain value from the current state. As described above, when the measured rotational speed is smaller than the critical rotational speed and the measured suction pressure is smaller than the critical suction pressure, that is, when there is no possibility that the supercharger 20 becomes overrotated, the rotational speed of the EGR blower 60 is Is reduced from the current state by a certain value.

  After passing through the above steps, the process returns to step S1 again, and the above steps are repeated until the rotational speed of the EGR blower 60 becomes zero. As described above, according to the control method shown in FIG. 2, since the rotational speed of the EGR blower 60 after the engine system 100 is suddenly stopped is determined based on the measured rotational speed and the measured suction pressure, the supercharger 20 is excessively charged. While avoiding rotation, it is possible to suppress the EGR blower 60 from rotating more than necessary.

<Control method 2 of EGR blower>
Next, another control method of the EGR blower 60 will be described. FIG. 3 is a flowchart showing a control method for the EGR blower 60 after the engine system 100 is suddenly stopped, which is different from the control method shown in FIG. This control is performed by the safe stop control unit 71.

  First, the safety stop control unit 71 acquires a measured rotational speed (the rotational speed of the supercharger 20) and a measured suction pressure (suction pressure at the inlet of the turbine unit 21) (step S11). Note that the rotation speed of the EGR blower 60 at the start of control is the rotation speed immediately before the engine system 100 is suddenly stopped.

  Subsequently, the safe stop control unit 71 calculates a first deceleration value based on the measured rotational speed (step S12). The first deceleration value is a value that does not cause the turbocharger 20 to overspeed even if the number of rotations of the EGR blower 60 is reduced by that value from the viewpoint of the measured speed. The first deceleration value is calculated from a mathematical formula or map prepared in advance with the measured rotational speed as a variable.

  The first deceleration value tends to decrease when the measured rotational speed is large. For example, as shown in the left diagram of FIG. 4, when the measured rotational speed is N2 or more, the first deceleration value is zero, and when the measured rotational speed is N1 or less, the first deceleration value is R1, and the measured rotational speed is N1. When N2 or less, the relationship between the two may be set so that the first deceleration value gradually increases from zero to R1 as the measured rotational speed decreases.

  Subsequently, the safe stop control unit 71 calculates a second deceleration value based on the measured suction pressure (step S13). From the viewpoint of the measured suction pressure, the second deceleration value is a value that does not cause the turbocharger 20 to overspeed even if the number of revolutions of the EGR blower 60 is reduced by that value. The second deceleration value is calculated from a mathematical formula or map prepared in advance with the measured suction pressure as a variable.

  The second deceleration value tends to decrease when the measured suction pressure is large. For example, as shown in the right diagram of FIG. 4, when the measured suction pressure is P2 or more, the second deceleration value is zero, and when the measured rotational speed is P1 or less, the second deceleration value is R2, and the measured suction pressure is P1. When P2 or less, the relationship between the two may be set so that the second deceleration value gradually increases from zero to R2 as the measured suction pressure decreases.

  Subsequently, the safety stop control unit 71 transmits a predetermined control signal to the blower control panel 63 to reduce the rotation speed of the EGR blower 60 by the smaller one of the first deceleration value and the second deceleration value. And decelerate (step S14). In the control method shown in FIG. 2 described above, the reduction value when the rotation speed of the EGR blower 60 is reduced is constant, whereas in the control method shown in FIG. 3, the rotation speed of the supercharger 20 and the supercharger are reduced. A reduction value (deceleration value) is determined based on the suction pressure of 20 turbine parts 21. Therefore, according to the control method shown in FIG. 3, unnecessary rotation of the EGR blower 60 can be suppressed as compared with the control method shown in FIG.

  In the above description, whether or not to reduce the rotation speed of the EGR blower 60 is determined or the amount of reduction is determined based on both the measurement rotation speed and the measurement suction pressure. Either one of the measurement rotation speed and the measurement suction pressure is determined. The decision may be made based on

  Instead of the configuration of engine system 100 shown in FIG. 1, the configuration shown in FIG. 5 may be adopted. In the engine system 100 shown in FIG. 5, the EGR drive motor 61 is a hydraulic motor, and the hydraulic oil boosted by the hydraulic power source device 65 is supplied to the EGR drive motor 61 via the pressure accumulator 66 and the hydraulic control device 67. According to this configuration, even if the hydraulic power source device 65 stops due to a power failure, the EGR drive motor 61 (EGR blower 60) can be rotated using the hydraulic oil accumulated in the pressure accumulator 66 as a power source. Therefore, even after a power failure, the above-described EGR blower 60 can be controlled.

(Second Embodiment)
<Overall configuration of engine system>
Next, an engine system 200 according to the second embodiment will be described. FIG. 6 is a block diagram of the engine system 200 according to the present embodiment. As shown in FIG. 6, the engine system 200 according to the present embodiment includes a bypass passage 31 that branches from the exhaust passage 30 and a bypass valve 32 provided in the bypass passage 31. The control device 70 is electrically connected to the bypass valve 32 and transmits a control signal to the bypass valve 32. In the present embodiment, the safety stop mechanism 80 is configured by the bypass flow path 31, the bypass valve 32, and the safety stop control unit 71 of the control device 70.

  In the second to fourth embodiments, power is not supplied to the EGR drive motor 61 due to a sudden stop of the engine system, and the EGR blower 60 is not controlled after the engine system suddenly stops. To do. Therefore, the engine system 200 does not include the power storage device 64 as shown in FIG. 1 or the pressure storage device 66 as shown in FIG. The bypass valve 32 can be operated for a predetermined time after the power failure by the power supplied from the auxiliary power supply device described above even at the time of the power failure.

<Bypass valve control method>
Next, a method for controlling the bypass valve 32 will be described. FIG. 7 is a flowchart showing a method of controlling the bypass valve 32 after the engine system 200 has been suddenly stopped. This control is performed by the safe stop control unit 71.

  First, the safety stop control unit 71 acquires a measured rotational speed (the rotational speed of the supercharger 20) and a measured suction pressure (suction pressure at the inlet of the turbine unit 21) (step S21).

  Subsequently, the safe stop control unit 71 determines whether or not the measured rotational speed is smaller than a preset dangerous rotational speed (step S22). When the measured rotational speed is smaller than the critical rotational speed (YES in step S22), the process proceeds to step S24, and when the measured rotational speed is equal to or higher than the critical rotational speed (NO in step S22), the process proceeds to step S23. The “dangerous rotation speed” is as described above.

  In step S23, the safe stop control unit 71 transmits a control signal to the bypass valve 32, and opens the bypass valve 32. Thus, when the measured rotational speed is larger than the critical rotational speed, that is, when there is a possibility that the supercharger 20 is over-rotated, the bypass valve 32 is opened. Thereby, a part of the air discharged from the engine main body 10 is guided to the bypass flow path 31, and the air flowing to the turbine unit 21 of the supercharger 20 is reduced to avoid over-rotation of the supercharger 20. Can do. A throttle valve whose opening degree is reduced in conjunction with the opening of the bypass valve 32 or a closing valve (not shown) that is closed in conjunction with the opening may be provided at the inlet of the turbine unit 21 of the supercharger 20. . According to such a configuration, it is possible to further suppress the air flow to the turbine unit 21 of the supercharger 20 and to avoid over-rotation of the supercharger 20.

  In step S24, the safe stop control unit 71 determines whether or not the measured suction pressure is smaller than a preset dangerous suction pressure. When the measured suction pressure is smaller than the dangerous suction pressure (YES in step S24), the process returns to step S21. When the measured suction pressure is higher than the dangerous suction pressure (NO in step S24), the process proceeds to step S23. The “dangerous suction pressure” is as described above.

  In step S23, as described above, the safety stop control unit 71 transmits a control signal to the bypass valve 32 and opens the bypass valve 32. Thus, when the measured suction pressure is equal to or higher than the dangerous suction pressure, that is, when there is a possibility that the supercharger 20 is over-rotated, the bypass valve 32 is opened. Thereby, the overspeed of the supercharger 20 can be avoided.

  After step S23, the process returns to step S21 again to repeat each step. As described above, according to the control method shown in FIG. 7, the bypass valve 32 after the engine system 200 suddenly stops based on both the rotational speed of the supercharger 20 and the suction pressure of the turbine section 21 of the supercharger 20. Therefore, it is possible to reliably avoid over-rotation of the supercharger 20.

(Third embodiment)
<Overall configuration of engine system>
Next, an engine system 300 according to the third embodiment will be described. FIG. 8 is a block diagram of the engine system 300 according to the present embodiment. As shown in FIG. 8, in the engine system 300 according to this embodiment, the supercharger 20 sets the variable nozzle 26 provided at the inlet of the turbine unit 21 and the variable nozzle 26 to a predetermined nozzle area (the angle is set). The nozzle actuator 27 is changed. The safety stop control unit 71 of the control device 70 is electrically connected to the nozzle actuator 27 and controls the variable nozzle 26 by transmitting a control signal to the nozzle actuator 27. In the present embodiment, a safety stop mechanism 80 is configured by the variable nozzle 26, the nozzle actuator 27, and the safety stop control unit 71. The nozzle actuator 27 can be operated for a predetermined time after the power failure by the power supplied from the auxiliary power supply device described above even during a power failure.

<Turbine nozzle control method>
Next, a method for controlling the variable nozzle 26 will be described. FIG. 9 is a flowchart showing a method for controlling the variable nozzle 26 after the engine system 300 has been suddenly stopped. This control is performed by the safe stop control unit 71.

  First, the safety stop control unit 71 acquires a measured rotational speed (the rotational speed of the supercharger 20) and a measured suction pressure (suction pressure at the inlet of the turbine unit 21) (step S41).

  Subsequently, the safe stop control unit 71 calculates the first nozzle area based on the measured rotation speed (step S42). The first nozzle area is a nozzle area in which there is no possibility that the supercharger 20 will be over-rotated even if the variable nozzle 26 is set to the area from the viewpoint of the measurement rotation speed. The first nozzle area is calculated from a mathematical formula or map prepared in advance with the measured rotation speed as a variable.

  Subsequently, the safe stop control unit 71 acquires the second nozzle area based on the measured suction pressure (step S43). From the viewpoint of the measured suction pressure, the second nozzle area is a nozzle area in which the supercharger 20 is not likely to be over-rotated even if the variable nozzle 26 is set to the area. The second nozzle area is obtained from a mathematical formula or map prepared in advance with the measured suction pressure as a variable.

  Subsequently, the safety stop control unit 71 transmits a control signal to the nozzle actuator 27, selects a nozzle area of the first nozzle area and the second nozzle area, which has a lower efficiency of the turbine unit 21, and a variable nozzle. 26 is set to be the nozzle area (step S44). As described above, according to the control method shown in FIG. 9, when there is a possibility that the supercharger 20 is over-rotated, the over-rotation of the supercharger 20 is avoided by reducing the efficiency of the turbine unit 21. be able to. The safety stop mechanism 80 of the present embodiment is configured by the variable nozzle 26, the nozzle actuator 27, and the safety stop control unit 71. In addition, the safety stop mechanism 80 includes the bypass flow path 31 and the bypass valve 32 shown in FIG. May be added. That is, you may combine the safety stop mechanism 80 of this embodiment, and the safety stop mechanism 80 of 2nd Embodiment.

  In the above description, the nozzle area of the variable nozzle 26 is determined based on both the measurement rotation speed and the measurement suction pressure. However, the nozzle of the variable nozzle 26 is determined based on either the measurement rotation speed or the measurement suction pressure. The area may be determined.

(Fourth embodiment)
<Overall configuration of engine system>
Next, an engine system 400 according to the fourth embodiment will be described. FIG. 10 is a block diagram of the engine system 400 according to the present embodiment. As shown in FIG. 10, the engine system 400 according to the present embodiment includes a first supercharger 20 and a second supercharger 29 arranged in parallel. The exhaust passage 30 extending from the engine body 10 branches at a predetermined branch point and reaches the turbine part 21 of the first supercharger 20 and the turbine part 21 of the second supercharger 29. Further, the supply flow path 40 extending from the compressor unit 22 of the first supercharger 20 and the compressor unit 22 of the second supercharger 29 merges at a predetermined merge point and reaches the engine body 10. Further, in the supply passage 40, an air discharge passage 36 communicating with the atmosphere is connected between the compressor unit 22 of the second supercharger 29 and the junction.

  An opening / closing valve 28 is provided between the branch point of the exhaust passage 30 and the turbine section 21 of the second supercharger 29. Further, a communication valve 34 is provided between a portion of the supply passage 40 to which the air discharge passage 36 is connected and the junction. Further, an air discharge valve 38 is provided in the air discharge passage 36.

  The safety stop control unit 71 of the control device 70 is electrically connected to the on-off valve 28 and transmits a control signal to the on-off valve 28. In the present embodiment, a safety stop mechanism 80 is configured by the on-off valve 28 and the safety stop control unit 71.

<Control method of on-off valve>
Next, a method for controlling the on-off valve 28 will be described. Here, when the engine system 400 is suddenly stopped, the first supercharger 20 is driven, while the second supercharger 29 is in a state in which the on-off valve 28 and the communication valve 34 are closed and the air discharge valve 38 is in an open state. It is assumed that it has been stopped. The control method of the on-off valve 28 is basically the same as the control method of the bypass valve 32 described in FIG. That is, on the basis of the measured rotational speed and the measured suction pressure of the first supercharger 20, when the first supercharger 20 is likely to be over-rotated, the on-off valve 28 is opened after the engine system 400 suddenly stops. . According to this configuration, air flows into the turbine section 21 of the second supercharger 29 that was stopped when the engine system 400 was suddenly stopped, and the air flows into the turbine section 21 of the first supercharger 20 that was being driven. By reducing the amount, the overspeed of the first supercharger 20 can be avoided. It is assumed that the communication valve 34 and the air discharge valve 38 maintain the open / closed state immediately before the engine system 400 is suddenly stopped.

  As described above, the embodiments of the present invention have been described with reference to the drawings. However, the specific configuration is not limited to these embodiments, and even if there is a design change or the like without departing from the gist of the present invention. It is included in the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, the engine system which has a supercharger and an EGR blower can be stopped safely at the time of a sudden stop. Therefore, it is useful in the technical field of engine systems.

10 Engine body 20 Turbocharger (first turbocharger)
21 Turbine part 22 Compressor part 26 Variable nozzle 28 On-off valve 29 Second supercharger 30 Exhaust flow path 31 Bypass flow path 32 Bypass valve 40 Supply flow path 50 EGR flow path 60 EGR blower 61 EGR drive motor 64 Power storage device 66 Accumulator 70 Control Device 71 Safe Stop Control Unit 80 Safe Stop Mechanism 100, 200, 300, 400 Engine System

Claims (11)

The engine body,
A turbocharger having a turbine section and a compressor section;
An exhaust passage for leading exhaust gas from the engine body to the turbocharger turbine section;
A supply flow path for introducing a supply gas from the compressor section of the supercharger to the engine body;
An EGR flow path that extracts a part of exhaust gas from the upstream side of the turbine section and guides it to the engine body;
An EGR blower that is provided in the EGR flow path and boosts the extracted exhaust gas,
An engine system further comprising a safety stop mechanism for avoiding over-rotation of the supercharger after a sudden stop of the engine system.   The engine system according to claim 1, wherein the safety stop mechanism includes a safety stop control unit that drives the EGR blower for a predetermined time after the engine system suddenly stops.   The engine system according to claim 2, wherein the safety stop control unit gradually reduces the rotational speed of the EGR blower after the engine system suddenly stops.   The safety stop control unit determines the number of revolutions of the EGR blower after the engine system is suddenly stopped based on one or both of the revolution number of the supercharger and the suction pressure of the turbine part of the supercharger. The engine system according to claim 3. The EGR blower is driven by an electric motor,
The engine system according to any one of claims 2 to 4, further comprising a power storage device that stores power in advance and supplies power to the electric motor in the event of a power failure. The EGR blower is driven by a hydraulic motor,
The engine according to any one of claims 2 to 4, wherein the engine system includes a pressure accumulating device that accumulates pre-pressurized hydraulic oil and supplies the pressurized hydraulic oil to the hydraulic motor during a power failure. system. The safety stop mechanism is
A bypass flow path branched from the exhaust flow path;
The engine system according to claim 1, further comprising: a bypass valve provided in the bypass flow path and opened after a sudden stop of the engine system.   The safety stop mechanism determines the opening / closing or opening degree of the bypass valve after a sudden stop of the engine system based on one or both of the rotation speed of the supercharger and the suction pressure of the turbine section of the supercharger. The engine system according to claim 7, further comprising a safety stop control unit. The supercharger has a variable nozzle provided at the inlet of the turbine section,
2. The engine system according to claim 1, wherein the safety stop mechanism includes a safety stop control unit that adjusts a nozzle area of the variable nozzle so that efficiency of the turbine unit decreases after a sudden stop of the engine system.   The safety stop control unit determines a nozzle area of the variable nozzle after a sudden stop of the engine system based on one or both of a rotation speed of the supercharger and a suction pressure of a turbine unit of the supercharger. The engine system according to claim 9. A plurality of the superchargers;
The safety stop mechanism is provided at an inlet of a turbine section of at least one of the superchargers, and has an on-off valve that is opened after the engine system is suddenly stopped when the engine system is in a closed state. Item 4. The engine system according to Item 1.

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