JP6062277B2 - Engine exhaust gas energy recovery system - Google Patents

Description

  The present invention relates to an engine exhaust gas energy recovery system including an exhaust gas aftertreatment device that purifies exhaust gas by reducing and removing harmful substances such as PM and NOx contained in the exhaust gas.

  Technology has been developed to recover the energy of exhaust gas from power generation and general-purpose engines with a turbine and effectively use it as exhaust gas energy. Technologies for recovering the exhaust gas energy and improving the fuel efficiency of the engine include a turbo compound, a hybrid turbo, and a power turbine for power generation. As a conventional technique related to turbo compound, for example, Patent Document 1 discloses a control apparatus for a turbo compound engine by combining a transmission and a turbo compound. In addition, as a conventional technique for recovering exhaust gas energy of an engine with a supercharger with a power turbine, for example, a turbocharger that can control exhaust pressure according to the rotational speed and load of the recovery device engine to improve fuel consumption and smoke An exhaust gas recirculation device for an attached engine is disclosed in Patent Document 2.

Japanese Utility Model Publication No. 63-035168 Japanese Patent Application Laid-Open No. 08-240156

  In recent years, there has been a demand to reduce and remove harmful substances such as PM and NOx contained in exhaust gas, and DPF (Diesel Particulate Filter: diesel particulate filter) and urea SCR (Selective Catalytic Reduction: selective reduction) are contained in the exhaust pipe of the engine. An exhaust gas aftertreatment device such as a catalyst) is installed. Conventionally, as shown in FIG. 6, the exhaust gas aftertreatment device 10 is often installed on the downstream side of the power turbine 14 which is the most downstream side of the exhaust pipe 12. However, on the downstream side of the power turbine 14, the exhaust gas temperature is generally as low as about 250 to 300 ° C., and it is a problem that proper exhaust gas aftertreatment performance cannot be exhibited. In particular, in the case of a turbo compound system, since the exhaust gas energy is small, the exhaust gas temperature is lowered to about 100 to 200 ° C., and this problem is remarkable.

  On the other hand, when installed upstream of the turbine section 16a of the turbocharger 16 having a high temperature, the upstream side is generally a high-pressure section, and the pressure resistance of the exhaust gas aftertreatment device needs to be increased. It becomes cost. If the exhaust gas aftertreatment device is installed upstream of the turbine section 16a, there is a risk that the exhaust gas aftertreatment device may destroy the downstream power turbine when the exhaust gas aftertreatment device is damaged. Although the conventional techniques disclosed in Patent Document 1 and Patent Document 2 described above can improve the fuel efficiency of the engine, there remains a problem in measures to ensure the exhaust gas treatment function of the exhaust gas aftertreatment device.

  The present invention has been made in view of the above problems, and an object thereof is to provide a new and improved engine exhaust gas energy recovery system capable of ensuring the exhaust gas treatment function of an exhaust gas aftertreatment device. .

One aspect of the present invention is an exhaust gas energy recovery system for an engine, which is a turbine section driven by exhaust gas guided from the engine body, and a compressor section that is driven by the turbine section and pumps outside air to the engine body. An exhaust turbine supercharger, a power turbine driven by the exhaust gas guided from the engine body, an energy recovery device that recovers energy of the exhaust gas by driving the power turbine, and the engine body An exhaust manifold that communicates with the power turbine through the turbine section and guides the exhaust gas to the outside, and a middle-stage exhaust pipe between the turbine section and the power turbine in the exhaust pipe Exhaust gas aftertreatment device for purifying the exhaust gas flowing in the exhaust pipe When the tube of the middle exhaust pipe, said to be a high temperature atmosphere that is required to exhibit the exhaust gas purification performance for exhaust gas aftertreatment device, the middle pressure control for controlling the pressure within the pipe of the middle exhaust pipe to a proper value And a section.

  According to one aspect of the present invention, an exhaust gas aftertreatment device is provided in a high-temperature exhaust gas atmosphere after setting a suitable pipe pressure for providing the exhaust gas aftertreatment device in the middle exhaust pipe. The exhaust gas treatment function can be ensured, and the cost for improving the pressure resistance of the exhaust gas aftertreatment device can be reduced.

  Further, in one aspect of the present invention, the middle-stage pressure control unit is provided in the middle-stage exhaust pipe, and the middle-stage pressure estimation unit that estimates a pressure inside the middle-stage exhaust pipe and the middle-stage pressure estimation unit It is good also as providing the rotation speed control part which controls the rotation speed of the said power turbine based on the pressure in a pipe | tube.

  In this way, the internal pressure of the intermediate exhaust pipe can be set to an appropriate value by controlling the rotational speed of the power turbine.

In one aspect of the present invention, the energy recovery device is a power transmission mechanism including a transmission that transmits a rotational force of the power turbine to a drive shaft of the engine and changes a rotational speed of the power turbine, The rotation speed control unit may control the transmission so that the inside of the middle exhaust pipe has a high temperature atmosphere required for the exhaust gas aftertreatment device to exhibit exhaust gas purification performance .

  In this way, the internal pressure of the middle exhaust pipe can be set to an appropriate value by controlling the transmission.

Further, in one aspect of the present invention, the middle-stage pressure control unit is provided in the middle-stage exhaust pipe, and the middle-stage pressure estimation unit that estimates a pressure inside the middle-stage exhaust pipe and the middle-stage pressure estimation unit Based on the pressure in the pipe, the pressure in the pipe on the upstream side of the power turbine and the power so that the inside of the middle stage exhaust pipe has a high temperature atmosphere required for the exhaust gas aftertreatment device to exhibit exhaust gas purification performance. It is good also as providing the pressure ratio control part which controls the pressure ratio with the pipe internal pressure of the downstream of a turbine.

  In this way, by controlling the pressure ratio between the upstream pipe pressure and the downstream pipe pressure of the power turbine, the pipe pressure of the middle exhaust pipe can be set to an appropriate value.

In one aspect of the present invention, the pressure ratio control unit controls a waste gate valve provided between the exhaust gas aftertreatment device and the power turbine, so that the inside of the middle exhaust pipe is in the exhaust gas. Controlling the pressure ratio between the pressure inside the pipe upstream of the power turbine and the pressure inside the pipe downstream of the power turbine so that the aftertreatment device has a high-temperature atmosphere required to exhibit exhaust gas purification performance. Also good.

  In this way, the internal pressure of the middle exhaust pipe can be set to an appropriate value by controlling the waste gate valve.

  As described above, according to the present invention, the exhaust gas aftertreatment device is provided in the middle exhaust pipe of the high temperature exhaust gas atmosphere by setting a suitable internal pressure for provision in the middle exhaust pipe. An exhaust gas treatment function can be secured.

1 is a schematic configuration diagram of an exhaust gas energy recovery system for an engine according to an embodiment of the present invention. It is a schematic block diagram of the exhaust gas energy recovery system of the engine which concerns on other embodiment of this invention. It is a flowchart which shows the control method of the middle stage pressure by the exhaust gas energy recovery system of the engine which concerns on other embodiment of this invention. It is a schematic block diagram of the exhaust gas energy recovery system of the engine which concerns on other embodiment of this invention. It is a flowchart which shows the control method of the middle stage pressure by the exhaust gas energy recovery system of the engine which concerns on other embodiment of this invention. It is a schematic block diagram of the exhaust gas energy recovery system of the conventional engine.

  Hereinafter, preferred embodiments of the present invention will be described in detail. The present embodiment described below does not unduly limit the contents of the present invention described in the claims, and all the configurations described in the present embodiment are essential as means for solving the present invention. Not necessarily.

(First embodiment)
First, the configuration of an exhaust gas energy recovery system for an engine according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram of an exhaust gas energy recovery system for an engine according to an embodiment of the present invention.

  The engine exhaust gas energy recovery system 100 of the present embodiment is a system that recovers energy from exhaust gas of an engine with a supercharger, and in order to ensure the exhaust gas treatment function of the exhaust gas aftertreatment device, the exhaust gas aftertreatment device is used. It is provided on the middle side of the exhaust pipe. As shown in FIG. 1, the exhaust gas energy recovery system 100 of the present embodiment includes an engine main body 102, an exhaust turbine supercharger 104, a power turbine 106, an energy recovery device 108, an exhaust gas aftertreatment device 110, and a middle stage. Pressure control unit 112.

  The engine body 102 is a diesel engine, and a screw propeller (not shown) is directly or indirectly attached to the crankshaft 114 via a propeller shaft (not shown). The engine body 102 is provided with a cylinder portion 116 including a cylinder liner (not shown), a cylinder cover (not shown), and the like. In each cylinder portion 116, a piston ( (Not shown) is arranged. The exhaust port 118 of each cylinder part 116 is connected to the exhaust manifold 120.

  The exhaust manifold 120 is mounted on the engine body 102 and is connected to the inlet side of the turbine section 104a of the exhaust turbine supercharger 104 via the first exhaust pipe L1. And it connects with the inlet side of the power turbine 106 via the 2nd exhaust pipe L2, and exhaust gas is guide | induced outside from the exit side of the power turbine 106 via the 3rd exhaust pipe L3. That is, the exhaust gas discharged from the exhaust manifold 120 is discharged to the outside via the first exhaust pipe L1, the turbine section 104a, the second exhaust pipe L2, the power turbine 106, and the third exhaust pipe L3. The In the present embodiment, the second exhaust pipe L2 is provided with an exhaust gas aftertreatment device 110 that purifies the exhaust gas flowing through the exhaust pipes L1 and L2.

  On the other hand, the air supply port 122 of each cylinder part 116 is connected to the air supply manifold 124, and the air supply manifold 124 is connected to the compressor part 104b of the exhaust turbine supercharger 104 via the air supply pipe L4. . A silencer (not shown) is disposed in the middle of the air supply pipe L3 connected to the inlet side of the compressor unit 104b, and the outside air that has passed through the silencer is guided to the compressor unit 104b. Yes. In addition, an air cooler (intercooler) 126, a surge tank (not shown), and the like are connected in the middle of an air supply pipe L4 connected to the outlet side of the compressor unit 104b. The air that has passed through the compressor section 104b is supplied to the air supply manifold 124 of the engine body 102 after passing through the air cooler 126, the surge tank, and the like.

  The exhaust turbine supercharger 104 is a turbocharger, and is driven by an exhaust gas (combustion gas) guided from the engine main body 102 via the first exhaust pipe L1, and driven by the turbine unit 104a. The compressor unit 104b that pumps outside air to the engine body 102 and a casing (not shown) that is provided between the turbine unit 104a and the compressor unit 104b and supports them are provided. The casing is inserted with a rotating shaft 104c having one end projecting toward the turbine section 104a and the other end projecting to the compressor section 104b. One end of the rotating shaft 104c is attached to a turbine disk (not shown) of a turbine rotor (not shown) constituting the turbine portion 104a, and the other end of the rotating shaft 104c is connected to the compressor portion 104b. It is attached to a hub (not shown) of a compressor impeller (not shown).

  The power turbine 106 is driven by the exhaust gas introduced from the engine body 102 via the first exhaust pipe L1 and the second exhaust pipe L2. The power turbine 106 is rotationally driven by exhaust gas, whereby the energy of the exhaust gas is recovered by the energy recovery device 108. In the present embodiment, the energy recovery device 108 is a generator that generates electric power by the rotational force of the rotor shaft 107.

  In the present embodiment, after the exhaust gas such as DPF, urea SCR, oxidation catalyst, etc. is placed in the middle stage exhaust pipe (second exhaust pipe) L2 located in the middle stage between the turbine section 104a of the exhaust turbine supercharger 104 and the power turbine 106. A processing apparatus 110 is installed. That is, the exhaust gas aftertreatment device 110 is provided in a middle exhaust pipe L2 included between the turbine section 104a and the power turbine 106 in the exhaust pipe, and purifies the exhaust gas flowing through the exhaust pipes L1, L2, and L3.

  In the case where the exhaust gas aftertreatment device 110 is a DPF, special exhaust gas temperature control (regeneration control) of about 600 ° C. is required in order to exhibit exhaust gas purification performance. On the other hand, when the exhaust gas aftertreatment device 110 is a urea SCR or an oxidation catalyst, regeneration control is not required, so that the exhaust gas purification performance is exhibited at a temperature of about 200 ° C. That is, when the exhaust gas aftertreatment device 110 is a DPF, it is preferable to install the exhaust gas aftertreatment device 110 in a high-temperature atmosphere of about 600 ° C., in particular, in order to exhibit exhaust gas purification performance.

  According to the examination result of the present inventor, the internal pressure of the first exhaust pipe L1 before the turbine section 104a is as high as about 3 bar, whereas the internal pressure of the middle exhaust pipe L2 in the same high-temperature atmosphere is 1 It was found that the pressure was about 4 bar, which was lower than the pressure in the first exhaust pipe L1. For this reason, by installing the exhaust gas aftertreatment device 110 in the middle exhaust pipe L2, the pressure in the pipe can be kept low while maintaining the exhaust gas treatment function while maintaining the exhaust gas treatment function while maintaining the exhaust gas purification performance. The cost increase associated with the improvement in performance can be minimized.

  Further, if the rotational speed of the power turbine 106 is increased, the pressure in the middle exhaust pipe L2 increases, so in this embodiment, the pressure in the middle exhaust pipe L2 is set to an appropriate value of about 1.4 bar. Further, a middle pressure control unit 112 is provided. That is, in order to install the exhaust gas aftertreatment device 110 in the intermediate exhaust pipe L2, the pressure resistance of the exhaust gas aftertreatment device 110 is improved by providing the middle pressure control unit 112 that controls the internal pressure of the middle exhaust pipe L2 to an appropriate value. Reduce the need for

  Further, when the exhaust gas aftertreatment device 110 is a DPF, if the fuel is burned in the exhaust gas aftertreatment device 110 during the forced regeneration of the DPF, energy can be recovered by the power turbine 106 on the downstream side by the increased temperature. . Conventionally, since the DPF is provided on the downstream side of the power turbine 106, the heat generation energy from the fuel additionally supplied at the time of forced regeneration is wasted. On the other hand, in this embodiment, since the DPF (exhaust gas aftertreatment device 110) is installed in the middle exhaust pipe L2, the heat turbine 106 can recover the heat generation energy from the fuel additionally charged at the time of forced regeneration. The fuel consumption rate is improved.

(Second Embodiment)
Next, the configuration of an exhaust gas energy recovery device for an engine according to another embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a schematic configuration diagram of an exhaust gas energy recovery system for an engine according to another embodiment of the present invention.

  The engine exhaust gas energy recovery system 200 according to the present embodiment is applied to a turbo compound in which an energy recovery device 240 is used as a power transmission mechanism 240 that transmits the rotational force of a power turbine 206 to an engine drive shaft 214. Similarly to the first embodiment, this embodiment is also characterized in that the exhaust gas aftertreatment device 210 is provided in the middle exhaust pipe L2 of the exhaust pipe in order to ensure the exhaust gas treatment function of the exhaust gas aftertreatment device 210. . As shown in FIG. 2, the exhaust gas energy recovery system 200 of the present embodiment includes an engine main body 202, an exhaust turbine supercharger 204, a power turbine 206, an energy recovery device 240, an exhaust gas aftertreatment device 210, and a middle stage. A pressure control unit 212. The present embodiment is applied to an engine with a supercharger equipped with an EGR function in which an exhaust gas recirculation device 230 that supplies exhaust gas discharged from the engine body 202 to the intake pipe L4 is provided.

  The energy recovery device 240 of this embodiment is a power transmission mechanism that transmits the rotational force of the power turbine 206 to the drive shaft 214 of the engine. The energy recovery device 240 is provided with a plurality of gears 240a, 240b, 240c, 240d for transmitting the rotational energy of the power turbine 206 to the engine drive shaft 214, and between the gear 240b and the gear 240c, A transmission 242 for changing the rotational speed is included.

  In the present embodiment, in order to keep the in-pipe pressure of the intermediate exhaust pipe L2 at an appropriate value, the intermediate pressure control unit 212 controls the rotational speed of the power turbine 206 by adjusting the transmission 242 to thereby control the intermediate exhaust pipe L2. Set the pressure in the pipe to an appropriate value. As shown in FIG. 2, the middle pressure control unit 212 includes a middle pressure estimation unit 211 and a rotation speed control unit 213. The middle-stage pressure estimation unit 211 is a device that can estimate and measure a pipe pressure such as a pressure sensor provided in the middle-stage exhaust pipe L2, and estimates the pipe pressure of the middle-stage exhaust pipe L2. The rotation speed control unit 213 adjusts the transmission 242 to control the rotation speed of the power turbine 206 based on the pipe pressure estimated by the middle stage pressure estimation unit 211, thereby appropriately adjusting the pipe pressure of the middle exhaust pipe L2. Set to value.

  Next, a method for controlling the middle pressure by the engine exhaust gas energy recovery system according to the present embodiment will be described with reference to the drawings. FIG. 3 is a flowchart showing a control method of the middle pressure by the engine exhaust gas energy recovery system according to another embodiment (second embodiment) of the present invention.

  In order to set the internal pressure of the intermediate exhaust pipe L2 to an appropriate value, first, the intermediate pressure estimation unit 211 measures the internal pressure (intermediate pressure) of the intermediate exhaust pipe L2 (step S10). 4 bar), the middle pressure control unit 212 determines (step S12). When the middle pressure control unit 212 determines that the middle pressure is not an appropriate value, the rotation speed control unit 213 controls the transmission 242 to adjust the rotation speed of the power turbine 206 (step S14), and the middle pressure Is controlled to be an appropriate value.

  As described above, in this embodiment, even when the internal pressure of the intermediate exhaust pipe L2 deviates from an appropriate value due to an environmental change or the like, the intermediate pressure can be controlled to be set to an appropriate value. That is, by installing the exhaust gas post-treatment device 210 in the middle exhaust pipe L2, the pressure in the pipe can be kept low while maintaining the exhaust gas treatment function while maintaining the exhaust gas treatment function while maintaining the same high-temperature atmosphere that can ensure the exhaust gas purification performance. Cost increase accompanying improvement can be suppressed to the minimum necessary.

(Third embodiment)
Next, the configuration of an exhaust gas energy recovery device for an engine according to another embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a schematic configuration diagram of an exhaust gas energy recovery system for an engine according to another embodiment of the present invention.

  The engine exhaust gas energy recovery system 300 according to the present embodiment is applied to a generator in which the energy recovery device 308 generates electric power by the rotational force of the rotor shaft 307 to adjust the internal pressure of the middle exhaust pipe L2 to the waste gate valve. 340 is performed. That is, the middle stage pressure control unit 312 controls the internal pressure (middle stage pressure) of the middle stage exhaust pipe L2 by controlling the waste gate valve 340 provided between the exhaust gas aftertreatment device 310 and the power turbine 306.

  As shown in FIG. 4, the exhaust gas energy recovery system 300 of the present embodiment includes an engine main body 302, an exhaust turbine supercharger 304, a power turbine 306, an energy recovery device 308, an exhaust gas aftertreatment device 310, and a middle stage. A pressure control unit 312. This embodiment is applied to an engine with a supercharger equipped with an EGR function in which an exhaust gas recirculation device 330 that supplies exhaust gas discharged from the engine main body 302 to the intake pipe L4 is provided.

  In the present embodiment, the intermediate pressure control unit 312 controls the waste gate valve 340 in order to set the in-pipe pressure of the intermediate exhaust pipe L2 to an appropriate value. As shown in FIG. 4, the middle stage pressure control unit 312 includes a middle stage pressure estimation unit 311 and a pressure ratio control unit 313. The middle-stage pressure estimation unit 311 is a device that can estimate and measure a pipe pressure such as a pressure sensor provided in the middle-stage exhaust pipe L2, and estimates the pipe pressure of the middle-stage exhaust pipe L2. Based on the in-pipe pressure estimated by the middle-stage pressure estimation unit 311, the pressure ratio control unit 313 determines the in-pipe pressure of the exhaust pipe L 2 upstream of the power turbine 306 and the in-pipe pressure of the exhaust pipe L 3 downstream of the power turbine 306. Is adjusted by a waste gate valve 340 to control the middle stage pressure. In other words, in the present embodiment, by adjusting the waste gate valve 340, the pressure ratio between the upstream pipe pressure and the downstream pipe pressure of the power turbine 306 is adjusted, and the pipe pressure of the middle exhaust pipe L2 is adjusted appropriately. Set to value.

  Next, a method for controlling the middle pressure by the engine exhaust gas energy recovery system according to the present embodiment will be described with reference to the drawings. FIG. 5 is a flowchart showing a control method of the middle pressure by the engine exhaust gas energy recovery system according to another embodiment (third embodiment) of the present invention.

  In order to set the internal pressure of the intermediate exhaust pipe L2 to an appropriate value, first, the intermediate pressure estimation unit 311 measures the internal pressure (intermediate pressure) of the intermediate exhaust pipe L2 (step S20), and the intermediate pressure is determined to be an appropriate value (1. 4 bar), the middle pressure control unit 312 determines whether or not (step S22). If the intermediate pressure control unit 312 determines that the intermediate pressure is not an appropriate value, the pressure ratio control unit 313 adjusts the waste gate valve 340 (step S24), so that the internal pressure of the intermediate exhaust pipe L2 becomes an appropriate value. To control.

  As described above, in this embodiment, even when the internal pressure of the intermediate exhaust pipe L2 deviates from an appropriate value due to an environmental change or the like, the intermediate pressure can be controlled to be set to an appropriate value. That is, by installing the exhaust gas aftertreatment device 310 in the middle exhaust pipe L2, the pressure inside the pipe can be kept low while maintaining the exhaust gas purification function while maintaining the exhaust gas purification performance while maintaining the exhaust gas purification performance. Cost increase accompanying improvement can be suppressed to the minimum necessary.

  Although the present embodiment has been described in detail as described above, those skilled in the art can easily understand that many modifications can be made without departing from the novel matters and effects of the present invention. Let's go. Therefore, all such modifications are included in the scope of the present invention.

  For example, a term described with a different term having a broader meaning or the same meaning at least once in the specification or the drawings can be replaced with the different term in any part of the specification or the drawings. Further, the configuration and operation of the engine exhaust gas energy recovery system are not limited to those described in the present embodiment, and various modifications can be made.

DESCRIPTION OF SYMBOLS 100 Exhaust gas energy recovery system 102 Engine main body 104 Exhaust turbine supercharger 104a Turbine part 104b Compressor part 106,206,306 Power turbine 108,308 Energy recovery apparatus 110 Exhaust gas post-processing apparatus 112,212,312 Middle pressure control part 120 Exhaust manifold 211, 311 Middle pressure estimation unit 213 Rotational speed control unit 214 (Engine) drive shaft 240 Power transmission mechanism (energy recovery device)
242 Transmission 313 Pressure ratio control unit 340 Wastegate valve L1 Exhaust pipe (first exhaust pipe)
L2 Middle exhaust pipe (second exhaust pipe)
L3 exhaust pipe (third exhaust pipe)
L4 Intake pipe

Claims (6)

An exhaust turbine supercharger having a turbine section driven by exhaust gas guided from the engine body, and a compressor section driven by the turbine section to pump outside air to the engine body;
A power turbine driven by the exhaust gas guided from the engine body;
An energy recovery device that recovers the energy of the exhaust gas by driving the power turbine;
An exhaust pipe that communicates the exhaust manifold of the engine body and the power turbine via the turbine section and guides the exhaust gas to the outside;
An exhaust gas aftertreatment device that is provided in a middle stage exhaust pipe between the turbine section and the power turbine of the exhaust pipe and purifies the exhaust gas flowing in the exhaust pipe;
Middle pressure control for controlling the pressure in the middle exhaust pipe to an appropriate value so that the inside of the middle exhaust pipe has a high temperature atmosphere required for the exhaust gas aftertreatment device to exhibit exhaust gas purification performance. And an exhaust gas energy recovery system for an engine. The middle pressure controller is
A middle-stage pressure estimating unit that is provided in the middle-stage exhaust pipe and estimates a pressure inside the middle-stage exhaust pipe;
The engine exhaust gas energy recovery system according to claim 1, further comprising: a rotation speed control unit that controls a rotation speed of the power turbine based on the in-pipe pressure estimated by the middle-stage pressure estimation unit. . The energy recovery device is a power transmission mechanism including a transmission that transmits a rotational force of the power turbine to a drive shaft of the engine and changes a rotational speed of the power turbine,
The rotation speed control unit controls the transmission so that the inside of the middle stage exhaust pipe has a high temperature atmosphere required for the exhaust gas aftertreatment device to exhibit exhaust gas purification performance. The engine exhaust gas energy recovery system according to claim 2. The middle pressure controller is
A middle-stage pressure estimating unit that is provided in the middle-stage exhaust pipe and estimates a pressure inside the middle-stage exhaust pipe;
Based on the in-pipe pressure estimated by the middle-stage pressure estimation unit, the power of the middle-stage exhaust pipe is set to a high temperature atmosphere required for the exhaust gas aftertreatment device to exhibit exhaust gas purification performance. 2. The engine exhaust gas energy recovery system according to claim 1, further comprising: a pressure ratio control unit configured to control a pressure ratio between a pipe internal pressure upstream of the turbine and a pipe internal pressure downstream of the power turbine. The pressure ratio control unit controls a waste gate valve provided between the exhaust gas aftertreatment device and the power turbine, so that the inside of the middle exhaust pipe exhibits exhaust gas purification performance for the exhaust gas aftertreatment device. The pressure ratio between the pipe pressure upstream of the power turbine and the pipe pressure downstream of the power turbine is controlled so as to obtain a high-temperature atmosphere required for the operation. Engine exhaust gas energy recovery system. The exhaust gas energy recovery system for an engine according to any one of claims 1 to 5, wherein the exhaust gas aftertreatment device is a renewable DPF.

Images