Slipmethane treatment system and engine system

Abstract

To provide a slip methane treatment system which can treat slip methane discharged from an engine, and can suppress the lowering of engine efficiency caused by the lowering of supercharger rotation number.SOLUTION: A slip methane treatment system comprises: a supercharger including an exhaust gas line connected to a discharge side of an engine, an air supply line connected to an air supply side of the engine, a turbine arranged at the exhaust gas line, and a compressor arranged at the air supply line; an exhaust gas catalyst device arranged at a downstream side of the turbine in the exhaust gas line, and including a methane oxidation catalyst which promotes the oxidation of methane; a turbine bypass line which is branched from the exhaust gas line at an upstream side of the turbine in the exhaust gas line, and merged with the exhaust gas line in a position between the turbine in the exhaust gas line and the exhaust gas catalyst device while bypassing the turbine; and a motor for assisting in the rotation of the supercharger.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a slip methane treatment system and an engine system.

Background Art

[0002] Patent Document 1 discloses an engine system including an engine, a supercharger including a turbine disposed downstream of the engine, an exhaust gas catalyst device for purifying exhaust gas disposed downstream of the turbine, and a bypass line provided so as to bypass the turbine in an exhaust gas line. In this configuration, in order to reach the operating temperature of the exhaust gas catalyst device in a short time, the waste gate valve of the bypass line is controlled according to the measured value of the exhaust gas temperature upstream of the turbine.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when a part of the exhaust gas of the engine bypasses the turbine of the supercharger and is supplied to the exhaust gas catalyst device, the energy that the turbine can recover from the exhaust gas of the engine decreases. Therefore, there is a risk that the scavenging pressure of the engine decreases due to a decrease in the supercharger rotation speed, and the engine efficiency decreases.

[0005] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide a slip methane treatment system that can treat slip methane discharged from an engine and suppress a decrease in engine efficiency due to a decrease in the supercharger rotation speed, and an engine system including the same.

Means for Solving the Problems

[0006] To achieve the above objectives, the slip methane treatment system according to at least one embodiment of this disclosure is: A slip methane treatment system for treating exhaust gas containing slip methane discharged from an engine, The exhaust gas line connected to the exhaust side of the aforementioned engine, An intake line connected to the intake side of the aforementioned engine, A supercharger including a turbine provided in the exhaust gas line and a compressor provided in the intake air line, An exhaust gas catalyst device provided downstream of the turbine in the exhaust gas line, which includes a methane oxidation catalyst that promotes the oxidation of methane, A turbine bypass line that branches off from the exhaust gas line upstream of the turbine in the exhaust gas line, bypasses the turbine, and rejoins the exhaust gas line at a position between the turbine and the exhaust gas catalyst in the exhaust gas line, A motor for assisting the rotation of the supercharger, It is equipped with.

[0007] To achieve the above objective, an engine system according to at least one embodiment of this disclosure comprises an engine and the slip methane treatment system. [Effects of the Invention]

[0008] According to at least one embodiment of the present disclosure, a slip methane treatment system and an engine system equipped therewith are provided that can treat slip methane discharged from an engine and suppress a decrease in engine efficiency due to a decrease in turbocharger rotational speed. [Brief explanation of the drawing]

[0009] [Figure 1] This diagram shows a schematic configuration of an engine system 1 according to one embodiment, and indicates that the engine 3 is operating in gas mode. [Figure 2]This diagram shows a schematic configuration of an engine system 1 according to one embodiment, and indicates that the engine 3 is operating in diesel mode. [Figure 3] This diagram illustrates an example of the hardware configuration of the motor control unit 26, the turbine bypass valve control unit 28, and the catalyst bypass control unit 30. [Figure 4] This figure shows an example of the control flow of the motor control unit 26 and the turbine bypass valve control unit 28 when engine 3 is operating in gas mode. [Figure 5] This figure shows another example of the control flow of the motor control unit 26 and the turbine bypass valve control unit 28 when engine 3 is operating in gas mode. [Modes for carrying out the invention]

[0010] Hereinafter, several embodiments of this disclosure will be described with reference to the attached drawings. However, the dimensions, materials, shapes, relative arrangements, etc., of the components described or shown in the drawings as embodiments are not intended to limit the scope of the invention, but are merely illustrative examples. For example, expressions describing relative or absolute arrangements such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" should not only strictly describe such arrangements, but also describe states of relative displacement with tolerances or angles or distances that allow for the same function to be achieved. For example, expressions such as "identical," "equal," and "homogeneous" that describe things being in an equal state not only describe a state of being strictly equal, but also describe a state in which there is a tolerance or a difference that is sufficient to achieve the same function. For example, expressions describing shapes such as squares or cylinders shall not only represent geometrically precise shapes such as squares or cylinders, but also shapes that include protrusions, chamfers, etc., to the extent that the same effect can be achieved. On the one hand, the expressions "comprising", "having", "including", or "containing" a component do not exclude the presence of other components.

[0011] (Engine system) FIG. 1 is a diagram showing a schematic configuration of an engine system 1 according to an embodiment. The engine system 1 includes an engine 3, an engine control unit 11 that controls the engine 3, and a slip methane processing system 2.

[0012] Hereinafter, a case where the engine 3 is a marine dual-fuel engine (DF engine) that can use liquefied natural gas (LNG) and diesel fuel as fuels will be described as an example. The engine 3 is configured to be capable of operating in a gas mode in which natural gas (fuel gas containing methane) vaporized from liquefied natural gas is lean premixed and burned, and in a diesel mode in which diesel fuel is injected into compressed air and burned. The engine control unit 11 is configured to control the engine 3 to select and execute either the gas mode or the diesel mode.

[0013] (Slip methane processing system) The slip methane processing system 2 is configured to be able to process slip methane, which is unburned methane discharged from the engine 3. In the exemplary form shown in FIG. 1, the slip methane processing system 2 includes an intake air line 4, an exhaust gas line 6, a supercharger 8, an exhaust gas catalyst device 10, a turbine bypass line 12, a turbine bypass valve 14, a catalyst device bypass line 16, a catalyst device bypass valve 18, a catalyst device side valve 20, a motor 22, an automatic engagement / disengagement clutch 23, a pressure sensor 24, a temperature sensor 25, a motor control unit 26, a turbine bypass valve control unit 28, and a catalyst bypass control unit 30.

[0014] The intake air line 4 is connected to the intake air side of the engine 3 and is configured to supply air to the engine 3.

[0015] The exhaust gas line 6 is connected to the exhaust side of the engine 3 and is configured to send the exhaust gas discharged from the engine 3. The exhaust gas line 6 is configured to supply the exhaust gas of the engine 3 from the engine 3 to, for example, an exhaust gas economizer (not shown).

[0016] The supercharger 8 includes a turbine 32 provided in the exhaust gas line 6 and a compressor 34 provided in the intake air line 4. The turbine 32 and the compressor 34 are connected via a shaft (not shown).

[0017] The exhaust gas catalytic device 10 is provided on the downstream side of the turbine 32 in the exhaust gas line 6. The exhaust gas catalytic device 10 includes a methane oxidation catalyst that promotes the oxidation of methane, and is configured to oxidize at least a part of methane (slip methane) in the exhaust gas using the methane oxidation catalyst and remove it from the exhaust gas. As the methane oxidation catalyst, for example, a catalyst containing a noble metal such as Pt (platinum), Ru (ruthenium) or Ir (iridium) can be used.

[0018] The turbine bypass line 12 branches from the exhaust gas line 6 at a position A1 upstream of the turbine 32 in the exhaust gas line 6, bypasses the turbine 32, and merges into the exhaust gas line 6 at a position A2 between the turbine 32 and the exhaust gas catalytic device 10 in the exhaust gas line 6. The turbine bypass line 12 is provided with a turbine bypass valve 14 as a flow rate adjustment valve that can adjust the flow rate of the exhaust gas flowing through the turbine bypass line 12. The temperature of the exhaust gas flowing through the turbine bypass line 12 is higher than the temperature of the exhaust gas immediately after doing work by the supercharger 8 (the temperature of the exhaust gas in the section between the supercharger 8 and the position A2 in the turbine bypass line 12). Therefore, the temperature of the exhaust gas flowing through the exhaust gas line 6 rises at the position A2 by being mixed with the exhaust gas that has passed through the turbine bypass line 12.

[0019] The catalytic converter bypass line 16 branches off from the exhaust gas line 6 at position A3 between the turbine 32 and the exhaust gas catalytic converter 10, bypasses the exhaust gas catalytic converter 10, and rejoins the exhaust gas line 6 at position A4 downstream of the exhaust gas catalytic converter 10. The catalytic converter bypass line 16 is provided with a catalytic converter bypass valve 18. A catalytic converter side valve 20 is also provided at a position between position A3 where the catalytic converter bypass line 16 branches off in the exhaust gas line 6 and position A2. The catalytic converter bypass valve 18 and the catalytic converter side valve 20 may each be, for example, an on / off valve or a flow control valve such as a damper valve.

[0020] Motor 22 is a motor that assists the rotation of the supercharger 8, and is configured as, for example, an inverter motor. In the illustrated example, the output shaft 22a of motor 22 is connected to the input shaft 34a of the compressor 34 of the supercharger 8 via an automatic engagement / disengagement clutch 23. The automatic engagement / disengagement clutch 23 is configured to automatically connect the output shaft 22a of motor 22 to the input shaft 34a of the supercharger 8 when the rotational speed of motor 22 reaches the rotational speed of the supercharger 8, enabling power transmission from motor 22 to the supercharger 8, and to automatically disengage the connection between the output shaft 22a of motor 22 and the input shaft 34a of the supercharger 8 when the rotational speed of motor 22 falls below the rotational speed of the supercharger 8.

[0021] The pressure sensor 24 is configured to measure the engine scavenging pressure P, which is the pressure of the intake air to the engine 3 pre-pressurized by the supercharger 8, at a position downstream of the compressor 34 in the intake air line 4. The engine scavenging pressure P is a parameter related to the operating state of the engine.

[0022] The temperature sensor 25 is configured to measure the catalyst inlet temperature T, which is the temperature of the exhaust gas at the inlet of the exhaust gas catalyst device 10. In the illustrated example, the temperature sensor 25 measures the catalyst inlet temperature T, which is the temperature of the exhaust gas at a position between the exhaust gas line 6 where the turbine bypass line 12 merges and the exhaust gas catalyst device 10.

[0023] The motor control unit 26 is configured to control the rotational speed of the supercharger 8 by controlling the motor 22. The motor control unit 26 is configured to be able to execute an electric assist mode in which the motor 22 assists the rotation of the supercharger 8. The motor control unit 26 executes the electric assist mode (turns the electric assist mode "on") when the engine 3 is operating in gas mode, and stops the operation of the motor 22 (turns the electric assist mode "off") when the engine 3 is operating in diesel mode. Details of the control of the motor control unit 26 will be described later.

[0024] The turbine bypass valve control unit 28 is configured to control the valve opening of the turbine bypass valve 14. When the engine 3 is operating in gas mode (see Figure 1), the turbine bypass valve control unit 28 controls the valve opening of the turbine bypass valve 14 based on the measurement results of the temperature sensor 25, and when the engine 3 is operating in diesel mode (see Figure 2), it closes the turbine bypass valve 14. Details of the control of the turbine bypass valve control unit 28 will be described later.

[0025] In Figures 1 and 2, the symbols for valves 14, 18, and 20 are shown as follows: a black-filled valve indicates that the valve is closed (fully closed), while a white-outlined valve indicates that the valve is at least partially open.

[0026] The catalytic converter bypass control unit 30 is configured to open and close the catalytic converter bypass valve 18 and the catalytic converter side valve 20, respectively. As shown in Figure 1, when the engine 3 is operating in gas mode, the catalytic converter bypass control unit 30 opens the catalytic converter side valve 20 and closes the catalytic converter bypass valve 18. Also, as shown in Figure 2, when the engine 3 is operating in diesel mode, the catalytic converter bypass control unit 30 opens the catalytic converter bypass valve 18 and closes the catalytic converter side valve 20.

[0027] Therefore, as shown in Figure 1, when engine 3 is operating in gas mode, a portion of the exhaust gas from engine 3 is supplied to the exhaust gas catalyst 10 through the turbine 32 of the supercharger 8, and a portion of the exhaust gas from engine 3 (the portion of the total engine exhaust gas that is not supplied to the turbine 32) is supplied to the exhaust gas catalyst 10 through the turbine bypass line 12.

[0028] Furthermore, as shown in Figure 2, when engine 3 is operating in diesel mode, the entire amount of exhaust gas from engine 3 flows through the turbine 32 of the supercharger 8 to the catalytic converter bypass line 16 and is not supplied to the exhaust gas catalytic converter 10.

[0029] (Hardware configuration of each control unit) Figure 3 is a diagram illustrating an example of the hardware configuration of the engine control unit 11, motor control unit 26, turbine bypass valve control unit 28, and catalyst bypass control unit 30.

[0030] As shown in Figure 3, each of the engine control unit 11, motor control unit 26, turbine bypass valve control unit 28, and catalyst bypass control unit 30 may be configured using a computer that includes, for example, a processor 72, RAM (Random Access Memory) 74, ROM (Read Only Memory) 76, HDD (Hard Disk Drive) 78, input I / F 80, and output I / F 82, which are connected to each other via a bus 84. In this case, each of the engine control unit 11, motor control unit 26, turbine bypass valve control unit 28, and catalyst bypass control unit 30 is configured by the computer executing a program that realizes the respective functions of the engine control unit 11, motor control unit 26, turbine bypass valve control unit 28, and catalyst bypass control unit 30. The respective functions of the engine control unit 11, motor control unit 26, turbine bypass valve control unit 28, and catalyst bypass control unit 30, as described below, are realized by, for example, loading a program held in ROM 76 into RAM 74 and executing it with the processor 72, as well as reading and writing data in RAM 74 and ROM 76.

[0031] However, the hardware configurations of the engine control unit 11, motor control unit 26, turbine bypass valve control unit 28, and catalyst bypass control unit 30 are not limited to those described above and may be configured as a combination of a control circuit and a memory device. Furthermore, two or more of the engine control unit 11, motor control unit 26, turbine bypass valve control unit 28, and catalyst bypass control unit 30 may share some or all of their hardware configurations, or each of the control units 11, 26, 28, and 30 may be implemented with separate hardware configurations.

[0032] (Control flow in gas mode) Figure 4 shows the control flow of the motor control unit 26 and the turbine bypass valve control unit 28 when the engine 3 is operating in gas mode.

[0033] As shown in Figure 4, the turbine bypass valve control unit 28 includes a subtraction unit 36 ​​and a valve control panel 38. The subtraction unit 36 ​​calculates the deviation ΔT (=Ts-Tm) between the set value Ts (target value of the catalyst inlet temperature T) and the measured value Tm measured by the temperature sensor 25 by subtracting the measured value Tm of the catalyst inlet temperature T from the set value Ts (target value of the catalyst inlet temperature T) of the catalyst inlet temperature T.

[0034] The valve control panel 38 performs feedback control to control the valve opening of the turbine bypass valve 14 in order to reduce the deviation ΔT calculated by the subtraction unit 36. The valve control panel 38 may, for example, send a valve opening instruction signal to the turbine bypass valve 14 to instruct it to open the valve, such as increasing the valve opening of the turbine bypass valve 14 if the deviation ΔT is greater than 0, and decreasing the valve opening of the turbine bypass valve 14 if the deviation ΔT is less than 0. The set value Ts of the catalyst inlet temperature T may be the activation temperature of the methane oxidation catalyst at which a predetermined reduction rate of slip methane can be expected in the exhaust gas catalyst 10, or it may be a temperature higher than the activation temperature. The set value Ts is stored in a storage device (for example, the ROM 76 or HDD 78 described above), read from the storage device, and used to calculate the deviation ΔT.

[0035] As shown in Figure 4, the motor control unit 26 includes a subtraction unit 40 and a motor control panel 42. The subtraction unit 40 calculates the deviation ΔP (=Ps-Pm) between the set value Ps (target value for the engine 3's scavenging pressure P) and the measured value Pm, measured by the pressure sensor 24, by subtracting the measured value Pm of the engine 3's scavenging pressure P from the set value Ps (target value for the engine 3's scavenging pressure P).

[0036] The motor control panel 42 performs feedback control to control the rotational speed of the supercharger 8, based on the deviation ΔP calculated by the subtraction unit 40, in order to reduce the deviation ΔP. For example, if the deviation ΔP is greater than 0, the rotational speed of the motor 22 is increased to increase the rotational speed of the supercharger 8, and if the deviation ΔP is less than 0, the rotational speed of the motor 22 is decreased to decrease the rotational speed of the supercharger 8. A rotational speed instruction signal is sent to the motor 22 to instruct the rotational speed of the motor 22 (i.e., the rotational speed of the supercharger 8). The set value Ps of the scavenging pressure P of the engine 3 is, for example, the required scavenging pressure to achieve a predetermined engine efficiency. The set value Ps is stored in a storage device (for example, the ROM 76 or HDD 78 mentioned above) and read from the storage device to be used in calculating the deviation ΔP.

[0037] Furthermore, when engine 3 is operating in gas mode, the motor control panel 42 may send a stop signal from the motor control unit 26 to motor 22 to stop the rotation of motor 22 and disengage the automatic engagement / disengagement clutch 23 if the flow rate of exhaust gas flowing through the turbine bypass line 12 is small and the scavenging pressure P is sufficiently secured for engine 3 (for example, if the above deviation ΔP is less than or equal to a predetermined value).

[0038] (Control flow in diesel mode) In diesel mode, engine 3 uses a low-sulfur fuel oil such as MGO as diesel fuel. In this case, the exhaust gas from engine 3 does not contain slip methane, so it is not necessary to pass the exhaust gas through the exhaust gas catalyst 10. Therefore, as shown in Figure 2, in diesel mode, the turbine bypass valve control unit 28 closes the turbine bypass valve 14, and the catalyst bypass control unit 30 opens the catalyst bypass valve 18 and closes the catalyst side valve 20. As a result, the entire amount of exhaust gas from engine 3 passes through the turbine 32 of the turbocharger 8, bypasses the exhaust gas catalyst 10, and is led to an exhaust gas economizer (not shown). Also, in diesel mode, there is no decrease in the rotational speed of the turbocharger 8 due to the bypass of exhaust gas to the turbine bypass line 12, so the motor control unit 26 turns off the above-mentioned electric assist mode and does not execute the above-mentioned electric assist mode. For this reason, the connection between the motor 22 and the turbocharger 8 via the automatic engagement / disengagement clutch 23 is released.

[0039] (Effects of the slip methane treatment system) The following describes the effects of the above-mentioned slip methane treatment system 2. According to the slip methane treatment system 2, when a portion of the exhaust gas from the engine 3 is supplied to the exhaust gas catalyst 10 via the turbine bypass line 12, the decrease in the temperature of the exhaust gas supplied to the exhaust gas catalyst 10 can be suppressed more effectively than when all of the exhaust gas from the engine 3 is supplied to the exhaust gas catalyst 10 via the turbine 32 of the supercharger 8. As a result, the methane oxidation catalyst of the exhaust gas catalyst 10 can function effectively in a high-temperature atmosphere, effectively oxidizing and removing the slip methane contained in the exhaust gas.

[0040] Furthermore, when a portion of the exhaust gas from engine 3 is supplied to the exhaust gas catalyst device 10 via the turbine bypass line 12, although the energy that the turbocharger 8's turbine 32 can recover from the exhaust gas decreases, the motor 22 can assist the rotation of the turbocharger 8. This suppresses a decrease in the engine 3's scavenging pressure P and thus suppresses a decrease in engine efficiency. Therefore, it is possible to oxidize and remove slip methane contained in the engine 3's exhaust gas while suppressing a decrease in engine efficiency due to a decrease in turbocharger rotation speed.

[0041] Furthermore, by measuring the catalyst inlet temperature T with the temperature sensor 25 and controlling the valve opening of the turbine bypass valve 14 to minimize the deviation ΔT between the set value Ts and the measured value Tm of the catalyst inlet temperature T, the catalyst inlet temperature T can be controlled to an appropriate temperature for oxidizing and removing slip methane with the methane oxidation catalyst. Therefore, slip methane contained in the exhaust gas can be properly oxidized and removed.

[0042] Furthermore, when a portion of the exhaust gas from engine 3 is supplied to the exhaust gas catalyst device 10 via the turbine bypass line 12, the amount of energy that the turbocharger 8's turbine 32 can recover from the exhaust gas decreases. However, by controlling the motor 22 based on the deviation ΔP (=Ps-Pm) between the set value Ps of the scavenging pressure and the measured value Pm of the scavenging pressure, at least a portion of the energy lost by the turbocharger 8's turbine 32 can be compensated for by the motor 22. This allows the scavenging pressure P of engine 3 to be brought closer to the set value Ps, thereby suppressing a decrease in engine efficiency.

[0043] Furthermore, in diesel mode, where diesel fuel is used, the exhaust gas from engine 3 does not contain slip methane, so there is no need to pass the exhaust gas through the exhaust gas catalyst device 10. Therefore, in diesel mode, as described above, the turbine bypass valve control unit 28 keeps the turbine bypass valve 14 closed, and only in gas mode is the aforementioned control of the valve opening of the turbine bypass valve 14 based on the measurement results of the temperature sensor 25 performed. This suppresses the reduction in the energy that the turbine 32 of the supercharger 8 can recover from the exhaust gas, and saves the driving energy of the motor 22 that assists the rotation of the supercharger 8. In addition, when engine 3 is operating in diesel mode, the exhaust gas is passed through the catalyst device bypass line 16, thereby avoiding pressure loss in the exhaust gas catalyst device 10. Also, since the exhaust gas does not pass through the catalyst of the exhaust gas catalyst device 10, poisoning of the catalyst by sulfur in the exhaust gas can be prevented.

[0044] In some embodiments, the motor control unit 26 and the turbine bypass valve control unit 28 may execute the control flow shown in Figure 5 instead of the control flow shown in Figure 4. In the control flow shown in Figure 5, reference numerals common to each component in the control flow shown in Figure 4 indicate the same components as in the control flow shown in Figure 4, unless otherwise specified, and their explanation is omitted.

[0045] In the control flow shown in Figure 5, the turbine bypass valve 14 or the turbine bypass valve control unit 28 transmits a lead signal Sb indicating the valve opening of the turbine bypass valve 14 to the motor control panel 42 of the motor control unit 26 as a lead signal for controlling the rotational speed of the turbocharger 8. The motor control panel 42 of the motor control unit 26 receives the lead signal Sb indicating the valve opening of the turbine bypass valve 14 from the turbine bypass valve 14 or the turbine bypass valve control unit 28. Then, the motor control panel 42 performs feedforward control with the rotational speed of the turbocharger 8 as the target of control based on the received lead signal Sb.

[0046] The motor control panel 42 calculates an estimated value Nd of the turbocharger 8's rotational speed from the valve opening of the turbine bypass valve 14 indicated by the received preceding signal Sb. It then determines an adjustment amount ΔN for the turbocharger 8's rotational speed to compensate for the deficiency ΔN (=Ns-Nd) between the estimated value Nd and the set value Ns (target value for the turbocharger 8's rotational speed), and adjusts the turbocharger 8's rotational speed by the adjustment amount ΔN. The motor control panel 42 then transmits a rotational speed instruction signal to the motor 22 to instruct it to set its rotational speed (i.e., the rotational speed of the turbocharger 8) to achieve the rotational speed of the turbocharger 8 adjusted by the adjustment amount ΔN. The set value Ns of the turbocharger 8's rotational speed is a predetermined rotational speed of the turbocharger 8 required to achieve the set value Ps of the scavenging pressure mentioned above. The set value Ns is calculated by a computing device (e.g., the processor 72 mentioned above) based on the load of the engine 3 and is used to calculate the deviation ΔN.

[0047] In the above flow, the estimated rotational speed Nd of the turbocharger 8 can be calculated, for example, as follows. First, correlation information K1 between the flow rate of exhaust gas supplied to the turbocharger 8 and the rotational speed of the turbocharger 8 is determined in advance and stored in a memory device (for example, the ROM 76 or HDD 78 mentioned above). Also, correlation information K2 between the valve opening of the turbine bypass valve 14 and the flow rate of exhaust gas flowing through the turbine bypass line 12 (hereinafter referred to as "turbine bypass amount F1") is determined in advance and stored in a memory device (for example, the ROM 76 or HDD 78 mentioned above). Then, the flow rate F2 of exhaust gas supplied to the turbocharger 8 is calculated by subtracting the turbine bypass amount F1, which is estimated based on the valve opening of the turbine bypass valve 14 and the correlation information K2 read from the memory device, from the flow rate of exhaust gas discharged from the engine 3. Then, the rotational speed of the turbocharger 8 can be estimated based on the calculated exhaust gas flow rate F2 and the correlation information K1 read from the memory device. Furthermore, the exhaust gas flow rate emitted from engine 3 may be an estimated flow rate based on the actual load on engine 3 and the correlation information between the load on engine 3 and the exhaust gas flow rate emitted from engine 3.

[0048] As described above, the motor control unit 26 performs feedforward control, using the valve opening of the turbine bypass valve 14, which affects the rotational speed of the turbocharger 8, as a preceding signal to control the rotational speed of the turbocharger 8. This allows the motor control unit 26 to compensate for at least a portion of the decrease in rotational speed of the turbocharger 8 caused by exhaust gas bypassing the turbine 32 and flowing into the turbine bypass line 12. Therefore, the decrease in rotational speed of the turbocharger 8 when exhaust gas flows into the turbine bypass line 12 can be suppressed. If there were no feedforward control based on the preceding signal, the electric assist control could only be performed after the scavenging pressure was measured by the pressure sensor 24 (after a decrease in scavenging pressure was detected), resulting in a temporary decrease in turbocharger rotational speed when exhaust gas is bypassed. In contrast, by performing feedforward control based on the preceding signal, the electric assist control can be started before the pressure sensor 24 detects a decrease in scavenging pressure, thus suppressing the temporary decrease in turbocharger rotational speed during bypass.

[0049] This disclosure is not limited to the embodiments described above, but also includes modified forms of the embodiments described above, as well as forms that combine these forms as appropriate. For example, in the embodiments shown in Figures 1 and 2, a configuration is illustrated in which the supercharger 8 and the motor 22 are connected via an automatic engagement / disengagement clutch 23. However, the configuration for connecting the supercharger 8 and the motor 22 does not have to be an automatic engagement / disengagement clutch 23. For example, an electromagnetic clutch or the like may be used instead of the automatic engagement / disengagement clutch 23. In this case, for example, the motor control unit 26 may control the electromagnetic clutch to connect the supercharger 8 and the motor 22 when the electric assist mode is executed, and control the electromagnetic clutch to release the connection between the supercharger 8 and the motor 22 when the electric assist mode is not executed. Furthermore, the supercharger 8 and the motor 22 may be separate components as described above, or the motor 22 may be built into the supercharger 8.

[0050] The contents described in each of the above embodiments can be understood, for example, as follows:

[0051] (1) A slip methane treatment system according to at least one embodiment of the present disclosure (for example, the slip methane treatment system 2 described above is A slip methane treatment system for treating exhaust gas containing slip methane discharged from an engine (for example, engine 3 described above), The intake line connected to the intake side of the engine (for example, the intake line 4 described above), An exhaust gas line connected to the exhaust side of the engine (for example, the exhaust gas line 6 described above), A turbocharger (e.g., the turbocharger 8) includes a turbine (e.g., the turbine 32 described above) provided in the exhaust gas line and a compressor (e.g., the compressor 34 described above) provided in the intake air line, An exhaust gas catalyst device (for example, the exhaust gas catalyst device 10 described above) is provided downstream of the turbine in the exhaust gas line and includes a methane oxidation catalyst for promoting the oxidation of methane, A turbine bypass line (for example, the turbine bypass line 12 described above) branches off from the exhaust gas line upstream of the turbine in the exhaust gas line, bypasses the turbine, and rejoins the exhaust gas line at a position between the turbine and the exhaust gas catalyst in the exhaust gas line, A motor (for example, the motor 22 described above) for assisting the rotation of the supercharger, It is equipped with.

[0052] According to the slip methane treatment system described in (1) above, when a portion of the engine exhaust gas is supplied to the exhaust catalytic converter via the turbine bypass line, the temperature drop of the exhaust gas supplied to the exhaust catalytic converter can be suppressed more effectively than when all of the engine exhaust gas is supplied to the exhaust catalytic converter via the turbocharger turbine. As a result, the methane oxidation catalyst can function effectively in a high-temperature atmosphere, effectively oxidizing and removing the slip methane contained in the exhaust gas. Furthermore, when a portion of the engine's exhaust gas is supplied to the exhaust gas catalytic converter via a turbine bypass line, the amount of energy that the turbocharger's turbine can recover from the exhaust gas decreases. However, since the motor can assist the rotation of the turbocharger, a decrease in engine scavenging pressure can be suppressed, and a decrease in engine efficiency can be suppressed. Therefore, it is possible to process the slip methane contained in the exhaust gas while suppressing the decrease in engine efficiency due to a decrease in turbocharger rotation speed.

[0053] (2) In some embodiments, in the slip methane treatment system described in (1) above, The system further includes a motor control unit (e.g., the motor control unit 26 described above) configured to control the motor based on parameters relating to the operating state of the engine (e.g., the scavenging pressure P described above).

[0054] According to the slip methane treatment system described in (2) above, the motor control unit can control the motor to suppress the decrease in engine efficiency based on parameters related to the engine's operating state.

[0055] (3) In some embodiments, in the slip methane treatment system described in (2) above, The aforementioned parameter is the scavenging pressure of the engine, The motor control unit is configured to control the motor based on the deviation (e.g., the deviation ΔP) between the set value of the scavenging pressure (e.g., the set value Ps mentioned above) and the measured value of the scavenging pressure (e.g., the measured value Pm mentioned above) when supplying a portion of the exhaust gas to the exhaust gas catalyst device via the turbine bypass line.

[0056] According to the slip methane treatment system described in (3) above, when a portion of the engine's exhaust gas is supplied to the exhaust gas catalyst via the turbine bypass line, the amount of energy that the turbocharger's turbine can recover from the exhaust gas decreases. However, by controlling the motor based on the deviation between the set value of the scavenging pressure and the measured value of the scavenging pressure, at least a portion of the energy that the turbocharger's turbine can recover from the exhaust gas can be compensated for by the motor. This makes it possible to suppress the engine's scavenging pressure from deviating from the set value and to suppress a decrease in engine efficiency.

[0057] (4) In some embodiments, in the slip methane treatment system described in any of (1) to (3) above, A turbine bypass valve (for example, the turbine bypass valve 14 described above) is provided in the turbine bypass line, A temperature sensor (for example, the temperature sensor 25 described above) configured to measure the temperature of the exhaust gas at the inlet of the exhaust gas catalyst device, A turbine bypass valve control unit (for example, the turbine bypass valve control unit 28 described above) is configured to control the valve opening of the turbine bypass valve based on the measurement results of the temperature sensor, It is further equipped with [this feature].

[0058] According to the slip methane treatment system described in (4) above, the valve opening of the turbine bypass valve can be controlled based on the temperature of the exhaust gas at the inlet of the exhaust gas catalyst, thereby controlling the temperature of the exhaust gas supplied to the exhaust gas catalyst to an appropriate temperature for oxidizing and removing slip methane with the methane oxidation catalyst. Therefore, slip methane contained in the exhaust gas can be properly oxidized and removed.

[0059] (5) In some embodiments, in the slip methane treatment system described in (4) above, The engine is configured to operate in a gas mode, which burns a fuel gas containing methane, and in a diesel mode, which burns diesel fuel. The turbine bypass valve control unit is configured to control the valve opening of the turbine bypass valve based on the measurement result of the temperature sensor when the engine is operating in the gas mode, and to close the turbine bypass valve when the engine is operating in the diesel mode.

[0060] According to the slip methane treatment system described in (5) above, in diesel mode using diesel fuel, the engine exhaust gas does not contain slip methane, so it is not necessary to pass the exhaust gas through the exhaust gas catalyst. Therefore, in diesel mode, as described above, the turbine bypass valve control unit keeps the turbine bypass valve closed, and only in gas mode does it perform the above-described control of the valve opening of the turbine bypass valve based on the measurement results of the temperature sensor. This suppresses the reduction in the energy that the turbocharger turbine can recover from the exhaust gas and saves the driving energy of the motor that assists the rotation of the turbocharger.

[0061] (6) In some embodiments, in the slip methane treatment system described in any of (1) to (5) above, The engine is configured to operate in both gas mode, which burns fuel gas containing methane, and diesel mode, which burns diesel fuel. The system further includes a catalyst bypass line (for example, the catalyst bypass line 16 described above) that branches off from the exhaust gas line at a position between the turbine and the exhaust gas catalyst in the exhaust gas line, bypasses the exhaust gas catalyst, and connects to the downstream side of the exhaust gas catalyst in the exhaust gas line.

[0062] According to the slip methane treatment system described in (6) above, in diesel mode using diesel fuel, the engine exhaust gas does not contain slip methane, so it is not necessary to pass the exhaust gas through the exhaust gas catalytic converter. Therefore, by flowing the exhaust gas through the catalytic converter bypass line when the engine is operating in diesel mode, pressure loss in the exhaust gas catalytic converter can be avoided, and since the exhaust gas does not pass through the catalyst of the exhaust gas catalytic converter 10, poisoning of the catalyst by sulfur in the exhaust gas can be prevented.

[0063] (7) In some embodiments, in the slip methane treatment system described in (6) above, A catalyst bypass valve (for example, the catalyst bypass valve 18 described above) is provided in the catalyst bypass line, A catalytic converter side valve (for example, the catalytic converter side valve 20 described above) is provided at a position between the point where the catalytic converter bypass line branches off in the exhaust gas line and the exhaust gas catalytic converter, It is further equipped with [this feature].

[0064] According to the slip methane treatment system described in (7) above, when the engine is operating in gas mode, the catalytic converter side valve is opened and the catalytic converter bypass valve is closed, thereby guiding the exhaust gas containing slip methane discharged from the engine to the exhaust gas catalytic converter, where the methane can be oxidized and removed. Furthermore, when the engine is operating in diesel mode, opening the catalytic converter bypass valve and closing the catalytic converter side valve avoids pressure loss in the exhaust gas catalytic converter, preventing exhaust gas from passing through the catalyst of the exhaust gas catalytic converter 10, and thus preventing the catalyst from being poisoned by sulfur in the exhaust gas.

[0065] (8) In some embodiments, in the slip methane treatment system described in (7) above, The system further includes a catalyst bypass control unit (for example, the catalyst bypass control unit 30 described above) that controls the catalyst bypass valve and the catalyst side valve, respectively. The engine is configured to operate in a gas mode, which burns a fuel gas containing methane, and in a diesel mode, which burns diesel fuel. The catalyst bypass control unit is configured to open the catalyst side valve and close the catalyst bypass valve when the engine is operating in gas mode, and to open the catalyst bypass valve and close the catalyst side valve when the engine is operating in diesel mode.

[0066] According to the slip methane treatment system described in (8) above, when the engine is operating in gas mode, the catalytic converter side valve is opened and the catalytic converter bypass valve is closed, thereby guiding the exhaust gas containing slip methane discharged from the engine to the exhaust gas catalytic converter, where the methane can be oxidized and removed. Furthermore, when the engine is operating in diesel mode, opening the catalytic converter bypass valve and closing the catalytic converter side valve avoids pressure loss in the exhaust gas catalytic converter, preventing exhaust gas from passing through the catalyst of the exhaust gas catalytic converter 10, and thus preventing the catalyst from being poisoned by sulfur in the exhaust gas.

[0067] (9) In some embodiments, in the slip methane treatment system described in any of (1) to (8) above, A turbine bypass valve (for example, the turbine bypass valve 14 described above) is provided in the turbine bypass line, The system includes a motor control unit (for example, the motor control unit 26 described above) configured to control the rotational speed of the supercharger by controlling the motor, The motor control unit is configured to receive a signal indicating the valve opening degree of the turbine bypass valve as a preceding signal (for example, the preceding signal Sb described above) for controlling the rotational speed of the supercharger, and to perform feedforward control with the rotational speed of the supercharger as the target of control based on the preceding signal.

[0068] According to the slip methane treatment system described in (9) above, by performing feedforward control that controls the turbocharger rotation speed using the opening degree of the turbine bypass valve, which affects the turbocharger rotation speed, as a preceding signal, it is possible to compensate for at least a portion of the decrease in turbocharger rotation speed caused by exhaust gas bypassing the turbine and flowing into the turbine bypass line, thereby suppressing the decrease in turbocharger rotation speed when exhaust gas flows into the turbine bypass line. If there is no feedforward control based on the preceding signal, the above-mentioned electric assist control can only be performed after measuring the scavenging pressure (after detecting a decrease in scavenging pressure), so the turbocharger rotation speed will temporarily decrease when the exhaust gas is bypassed. In contrast, by performing feedforward control based on the preceding signal, the above-mentioned electric assist control can be started before detecting a decrease in scavenging pressure, thus suppressing the temporary decrease in turbocharger rotation speed when bypassing.

[0069] (10) An engine system according to at least one embodiment of the present disclosure (e.g., the engine system 1 described above) The system comprises an engine (for example, engine 3 described above) and a slip methane treatment system described in any of (1) to (9) above (for example, slip methane treatment system 2 described above).

[0070] According to the engine system described in (10) above, since it is equipped with the slip methane treatment system described in any of (1) to (9) above, it is possible to oxidize and remove slip methane contained in the exhaust gas while suppressing a decrease in engine efficiency. [Explanation of Symbols]

[0071] 1. Engine System 2. Slip Methane Treatment System 3 Engines 4. Air intake line 6. Exhaust gas line 8. Supercharger 10 Exhaust gas catalytic converter 11 Engine Control Unit 12 Turbine Bypass Line 14. Turbine bypass valve 16. Catalytic converter bypass line 18 Catalytic converter bypass valve 20 Catalytic converter side valve 22 motors 22a Output shaft 23 Clutch 24 Pressure Sensors 25 Temperature Sensor 26 Motor control unit 28 Turbine Bypass Valve Control Unit 30 Catalyst bypass control unit 32 Turbines 34 Compressor 34a Input axis 36 Subtraction Unit 38 Valve control panel 40 Subtraction section 42 Motor control panel 72 processors 74 RAM 76 ROM 78 HDD 80 Input Interfaces 82 Output Interfaces 84 Bus

Claims

1. A slip methane treatment system for treating exhaust gas containing slip methane discharged from an engine, The exhaust gas line connected to the exhaust side of the aforementioned engine, An intake line connected to the intake side of the aforementioned engine, A supercharger including a turbine provided in the exhaust gas line and a compressor provided in the intake air line, An exhaust gas catalyst device provided downstream of the turbine in the exhaust gas line, which includes a methane oxidation catalyst for promoting the oxidation of methane, A turbine bypass line that branches off from the exhaust gas line upstream of the turbine in the exhaust gas line, bypasses the turbine, and rejoins the exhaust gas line at a position between the turbine and the exhaust gas catalyst in the exhaust gas line, A motor for assisting the rotation of the supercharger, Equipped with, The system further includes a motor control unit configured to control the motor based on parameters relating to the operating state of the engine, The aforementioned parameter is the scavenging pressure of the engine, The motor control unit is configured to control the motor based on the deviation between a set value of the scavenging pressure calculated as the necessary scavenging pressure to achieve a predetermined engine efficiency based on the engine load, and a measured value of the scavenging pressure when a portion of the exhaust gas is supplied to the exhaust gas catalyst, when a portion of the exhaust gas is supplied to the exhaust gas catalyst, when a portion of the exhaust gas is supplied to the exhaust gas catalyst. Slip methane treatment system.

2. A turbine bypass valve provided in the turbine bypass line, A temperature sensor configured to measure the temperature of the exhaust gas at the inlet of the exhaust gas catalyst device, A turbine bypass valve control unit is configured to control the valve opening of the turbine bypass valve based on the measurement results of the temperature sensor, The slip methane treatment system according to claim 1, further comprising the following:

3. A slip methane treatment system for treating exhaust gas containing slip methane discharged from an engine, The exhaust gas line connected to the exhaust side of the aforementioned engine, An intake line connected to the intake side of the aforementioned engine, A supercharger including a turbine provided in the exhaust gas line and a compressor provided in the intake air line, An exhaust gas catalyst device provided downstream of the turbine in the exhaust gas line, which includes a methane oxidation catalyst for promoting the oxidation of methane, A turbine bypass line that branches off from the exhaust gas line upstream of the turbine in the exhaust gas line, bypasses the turbine, and rejoins the exhaust gas line at a position between the turbine and the exhaust gas catalyst in the exhaust gas line, A motor for assisting the rotation of the supercharger, Equipped with, A turbine bypass valve provided in the turbine bypass line, A temperature sensor configured to measure the temperature of the exhaust gas at the inlet of the exhaust gas catalyst device, A turbine bypass valve control unit is configured to control the valve opening of the turbine bypass valve based on the measurement results of the temperature sensor, Furthermore, The engine is configured to operate in a gas mode, which burns a fuel gas containing methane, and in a diesel mode, which burns diesel fuel. A slip methane treatment system comprising a turbine bypass valve control unit configured to control the valve opening of the turbine bypass valve based on the measurement result of the temperature sensor when the engine is operating in the gas mode, and to close the turbine bypass valve when the engine is operating in the diesel mode.

4. The slip methane treatment system according to claim 1 or 3, further comprising a catalyst bypass line that branches off from the exhaust gas line at a position between the turbine and the exhaust gas catalyst in the exhaust gas line, bypasses the exhaust gas catalyst, and connects to the downstream side of the exhaust gas catalyst in the exhaust gas line.

5. A catalyst bypass valve provided in the catalyst bypass line, A catalytic converter side valve is provided at a position between the location where the catalytic converter bypass line in the exhaust gas line branches off and the exhaust gas catalytic converter, The slip methane treatment system according to claim 4, further comprising the above.

6. The system further comprises a catalyst bypass control unit that controls the catalyst bypass valve and the catalyst side valve, respectively. The engine is configured to operate in a gas mode, which burns a fuel gas containing methane, and in a diesel mode, which burns diesel fuel. The slip methane treatment system according to claim 5, wherein the catalyst bypass control unit is configured to open the catalyst side valve and close the catalyst bypass valve when the engine is operating in the gas mode, and to open the catalyst bypass valve and close the catalyst side valve when the engine is operating in the diesel mode.

7. A slip methane treatment system for treating exhaust gas containing slip methane discharged from an engine, The exhaust gas line connected to the exhaust side of the aforementioned engine, An intake line connected to the intake side of the aforementioned engine, A supercharger including a turbine provided in the exhaust gas line and a compressor provided in the intake air line, An exhaust gas catalyst device provided downstream of the turbine in the exhaust gas line, which includes a methane oxidation catalyst for promoting the oxidation of methane, A turbine bypass line that branches off from the exhaust gas line upstream of the turbine in the exhaust gas line, bypasses the turbine, and rejoins the exhaust gas line at a position between the turbine and the exhaust gas catalyst in the exhaust gas line, A motor for assisting the rotation of the supercharger, Equipped with, The exhaust gas line further comprises a catalyst bypass line that branches off from the exhaust gas line at a position between the turbine and the exhaust gas catalyst in the exhaust gas line, bypasses the exhaust gas catalyst, and connects to the downstream side of the exhaust gas catalyst in the exhaust gas line. A catalyst bypass valve provided in the catalyst bypass line, A catalytic converter side valve is provided at a position between the location where the catalytic converter bypass line in the exhaust gas line branches off and the exhaust gas catalytic converter, Furthermore, The system further comprises a catalyst bypass control unit that controls the catalyst bypass valve and the catalyst side valve, respectively. The engine is configured to operate in a gas mode, which burns a fuel gas containing methane, and in a diesel mode, which burns diesel fuel. A slip methane treatment system wherein the catalyst bypass control unit is configured to open the catalyst side valve and close the catalyst bypass valve when the engine is operating in the gas mode, and to open the catalyst bypass valve and close the catalyst side valve when the engine is operating in the diesel mode.

8. The slip methane treatment system according to claim 2, wherein the motor control unit is configured to receive a signal indicating the valve opening degree of the turbine bypass valve as a preceding signal for controlling the rotational speed of the supercharger, and to perform feedforward control with the rotational speed of the supercharger as the target of control based on the preceding signal.

9. An engine system comprising an engine and a slip methane treatment system according to any one of claims 1, 3, or 7.

Images