JP2013032751A - Engine system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an engine system having an improved energy efficiency of the entire system by recovering thermal energy of high-temperature EGR gas exhausted to the outside as electric power or power.SOLUTION: The system includes: a turbo supercharger 4 including an exhaust turbine 43 driven by an exhaust gas exhausted from engine 1 and a compressor 42 driven by the exhaust turbine 43 and compressing air sucked from the outside to discharge the compressed air; and an EGR passage 5 re-circulating some of the exhaust gas exhausted from the engine 1 as EGR gas to an intake part of the engine 1. The system further includes: a branch air passage 6 circulating some of the compressed air discharged from the compressor 42; a gas-gas heat exchanger 7 transferring thermal energy of high-temperature EGR gas circulating in the EGR passage 5 to the compressed air circulating in the branch air passage 6 to heat the compressed air circulating in the branch air passage 6; and an air turbine 8 driven by the compressed air heated by the gas-gas heat exchanger 7.

Description

  The present invention relates to an engine system with a turbocharger equipped with an EGR (Exhaust Gas Recirculation) mechanism.

  2. Description of the Related Art Conventionally, in an internal combustion engine system mounted on a vehicle or the like, a part of exhaust gas exhausted from the exhaust part of the engine is returned to the intake part of the engine to reduce the oxygen concentration of the intake air, thereby reducing the combustion temperature of the engine. EGR is performed to reduce the generation of NOx (nitrogen oxide). As a mechanism for performing EGR, an engine system is provided with an EGR passage that connects an exhaust portion and an intake portion of the engine. In addition, an EGR cooler is provided in the EGR passage in order to prevent a reduction in engine intake charging efficiency due to a portion of the high-temperature exhaust gas being taken into the engine again as EGR gas. The high-temperature EGR gas flowing through the EGR cooler is cooled by, for example, the engine coolant diverted for the EGR cooler, and the thermal energy of the high-temperature EGR gas is supplied from the radiator for radiating the engine coolant via the engine coolant. Released outside (in the atmosphere). An engine system with a turbocharger equipped with an EGR mechanism that recovers the thermal energy of high-temperature EGR gas that has been cooled by the EGR cooler and discarded to the outside as electric power and improves the energy efficiency of the entire system is provided. ing. According to this, an evaporator of a water circulation circuit is disposed in the EGR passage, and liquid water whose pressure has been increased by the circulation pump is heated by high-temperature EGR gas flowing through the EGR passage to form steam, and the high-temperature and high-pressure steam. The steam turbine is driven to rotate, and power is generated by a generator connected to the steam turbine. The water vapor whose pressure and temperature are reduced by driving the steam turbine is cooled by a condenser, returned to liquid water, and sucked into a circulation pump (Patent Document 1). Thereby, the thermal energy of the high-temperature EGR gas that has been conventionally cooled by the EGR cooler and discarded to the outside can be recovered as electric power, and the energy efficiency of the entire system can be improved.

JP 2010-242726 A

  According to the engine system according to Patent Document 1 described above, it is essential to circulate water as a working medium. Therefore, in the water circulation circuit, in addition to the evaporator and the steam turbine, a condenser that cools the water vapor discharged from the steam turbine and returns it to liquid water, and a circulation pump that boosts the liquid water and sends it to the evaporator In addition, the water circulation circuit is required to have high airtightness to avoid leakage of water and water vapor. This inevitably increases the size, weight and cost of the system as a whole.

  Furthermore, water is used as a working medium. In a cold environment, water freezes when the engine is stopped, and the system cannot be started, or the system may be damaged due to volume expansion accompanying ice generation.

  The present invention has been made in view of the above circumstances, and recovers thermal energy of high-temperature EGR gas, which is a part of exhaust gas discharged from an engine, as electric power or power, thereby improving the energy efficiency of the entire system. It is an object of the present invention to provide an engine system that is small, light, and low in cost, and that can suppress the possibility of the system becoming unable to start or being damaged even in a cold environment. .

  An engine system according to aspect 1 of the present invention includes an engine having an intake portion and an exhaust portion, an intake passage that supplies intake air including air sucked from outside to the intake portion of the engine, and exhausted from the exhaust portion of the engine An exhaust passage that exhausts exhaust gas to the outside, an exhaust turbine that is provided in the exhaust passage and is driven by exhaust gas discharged from the exhaust part of the engine, and an exhaust passage that is provided in the intake passage and is driven by the exhaust turbine, EGR which recirculates a part of the exhaust gas discharged from the exhaust part of the engine as EGR gas to the intake part of the engine as a turbocharger having a compressor that compresses the air sucked into the passage and discharges the compressed air And is further branched from the intake passage downstream of the turbocharger compressor and discharged from the turbocharger compressor. A compressed air that circulates the high-temperature heat energy of the EGR gas that is provided between the EGR passage and the branch air passage that circulates a part of the compressed air that is circulated, and the EGR passage. The gas-gas heat exchanger that heats the compressed air that flows through the branch air passage and cools the EGR gas that flows through the EGR passage, and the downstream branch air passage from the gas-gas heat exchanger And an air turbine connected to a generator or driven mechanism and driven by compressed air heated in a gas-gas heat exchanger.

  According to this aspect, in the gas-gas heat exchanger provided between the EGR passage and the branch air passage, a part of the compressed air discharged from the turbocharger compressor is circulated through the branch air passage. The thermal energy of the EGR gas is transferred to the compressed air flowing through the branch air passage, and the air turbine is rotated by the compressed air heated to a high temperature to recover it as electric power or power, improving the energy efficiency of the entire system To do.

  Further, according to this aspect, the heat energy of the high-temperature EGR gas is transmitted, and a part of the compressed air discharged from the compressor of the turbocharger is used as the compressed air that rotationally drives the air turbine. For this reason, unlike the system according to the conventional Patent Document 1, a device corresponding to a circulation pump for boosting the working medium is unnecessary, and the system can be reduced in size, weight, and cost. The power required for driving is also reduced, and the energy efficiency of the entire system is improved.

  Furthermore, according to this aspect, unlike the system according to the conventional Patent Document 1, the working medium is not water but air, which is sucked in from the outside, driven to the air turbine, and then discharged to the outside. For this reason, the apparatus equivalent to the condenser in the water circulation circuit which concerns on the conventional patent document 1 is unnecessary, and a system can be reduced in size, weight, and cost. Further, unlike the case of water, high airtightness is not necessary, which is advantageous for reducing the size, weight and cost of the system.

  Furthermore, according to this aspect, unlike the system according to Patent Document 1, the working medium is air different from water and does not freeze even in a cold environment, and the system can be started even in a cold environment. It is possible to suppress the possibility of breakage.

  The engine system according to aspect 2 of the present invention includes the intake air diversion valve for adjusting the flow rate of the compressed air flowing from the intake passage into the branch air passage in the above aspect. In this case, the intake pressure of the engine is set to a predetermined value with respect to the exhaust pressure by controlling the opening of the intake branch valve and adjusting the flow rate of the compressed air flowing into the branch air passage according to changes in the engine speed. EGR is enabled by maintaining the pressure of only low, and the thermal energy of hot EGR gas can be recovered as electric power or power using the compressed air flowing into the branch air passage, improving the energy efficiency of the entire system To do.

  According to the engine system according to aspect 3 of the present invention, in the above aspect, the driven mechanism is a turbocharger. In this case, in an engine system having a high EGR ratio in which EGR gas accounts for a large proportion of the intake air supplied to the engine, the compressor of the turbocharger is reduced by reducing the exhaust gas flow rate discharged from the engine and flowing into the exhaust turbine. The amount of decrease in the power of the exhaust turbine that rotationally drives the engine can be supplemented by the power of the air turbine that is heated to high temperature by the EGR gas having an increased flow rate and that is rotationally driven by the compressed air flowing through the branch air passage. For this reason, the flow rate of the compressed air required for the engine is secured, operation at a high intake pressure is possible, the specific output of the engine is improved, and the energy efficiency of the entire system is improved.

  According to the engine system according to aspect 4 of the present invention, in the above aspect, the gas-gas heat exchanger is a counter-current heat exchanger. In this case, the temperature difference at each position along the gas-gas heat exchanger between the EGR gas and the compressed air that conducts heat while flowing in opposite directions can be reduced, and the heat of the EGR gas can be reduced. The temperature drop in the process of transferring energy to the compressed air can be kept small. For this reason, the thermal energy of high-temperature EGR gas can be efficiently transmitted to the compressed air and recovered as electric power or power, and the energy efficiency of the entire system is improved.

  According to the engine system according to aspect 5 of the present invention, in the above aspect, the air turbine is a radial flow turbine having a variable capacity mechanism. In this case, the flow rate characteristic of the turbine can be changed according to the change in the flow rate of the compressed air flowing through the branch air passage, and the air turbine can be operated efficiently with a wide range of compressed air flow rates. For this reason, the thermal energy of high-temperature EGR gas can be efficiently recovered as electric power or power for a wide range of engine speeds, and the energy efficiency of the entire system is improved.

  ADVANTAGE OF THE INVENTION According to this invention, the thermal energy of high temperature EGR gas is collect | recovered as electric power or motive power, and the engine system which is small, light weight, and low cost which improved the energy efficiency of the whole system can be provided. Furthermore, unlike the prior art, water is eliminated as the working medium and air is used, so that the possibility that the system cannot be started or damaged even in a cold environment can be suppressed.

1 is a circuit diagram illustrating an engine system according to Embodiment 1. FIG. 4 is a graph schematically showing a relationship between an engine speed, a pressure, and an intake air diversion valve opening according to the first embodiment. FIG. 6 is a circuit diagram illustrating an engine system according to a second embodiment.

(Embodiment 1)
FIG. 1 shows the concept of Embodiment 1 of the present invention. As shown in FIG. 1, the engine system includes an engine 1, an intake passage 2, an exhaust passage 3, a turbocharger 4, and an EGR passage 5, and further includes a branch air passage 6, a gas-gas A heat exchanger 7 and an air turbine 8 are provided.

  The engine 1 is a reciprocating piston type internal combustion engine in which a plurality of cylinders are arranged in series, and is either a compression ignition type using light oil or the like as a fuel, or a spark ignition type using gasoline, liquefied petroleum gas, natural gas or the like as a fuel. Good. The engine 1 includes an engine structure 11 including a cylinder block, a cylinder head, and the like, an intake manifold 12 (intake unit) that distributes intake air sucked into each cylinder, and an exhaust manifold that collects exhaust gas discharged from each cylinder. 13 (exhaust section), and a crank mechanism and a valve operating mechanism (not shown). The power output from the engine 1 is used for driving the vehicle and driving a compressor or the like via a power transmission mechanism (not shown), or converted into electric power by driving a generator (not shown). Used.

  The intake passage 2 is a passage for supplying intake air including air sucked from outside to the intake manifold 12 of the engine 1, one end being opened to the outside, and the other end being connected to the intake manifold 12 of the engine 1. In the intake passage 2, in order from the upstream side, an air cleaner 21 that removes foreign matters such as dust from the air sucked from the outside, a centrifugal compressor 42 that compresses the air sucked from the outside and discharges the compressed air, and a compression An intercooler 22 is provided for cooling the compressed air whose temperature has been increased and improving the intake charging efficiency of the engine 1. The compressed air flowing through the intercooler 22 is cooled by the intercooler coolant flowing through the intercooler coolant passage 92.

  The exhaust passage 3 is a passage for discharging exhaust gas discharged from the exhaust manifold 13 of the engine 1 to the outside. One end of the exhaust passage 3 is connected to the exhaust manifold 13 of the engine 1 and the other end is opened to the outside. In the exhaust passage 3, in order from the upstream side, a radial flow type exhaust turbine 43 that is rotationally driven by the exhaust gas discharged from the engine 1, and an exhaust purification device such as a catalyst that purifies harmful components contained in the exhaust gas. 31 and a silencer 32 for reducing exhaust noise are provided.

  A compressor 42 provided in the intake passage 2 and an exhaust turbine 43 provided in the exhaust passage 3 are connected by a first connecting shaft 41 to constitute the turbocharger 4. The exhaust turbine 43 is rotationally driven by the exhaust gas discharged from the engine 1, and the compressor 42 is rotationally driven by the exhaust turbine 43.

  The EGR passage 5 is a passage that recirculates a part of the high-temperature exhaust gas discharged from the exhaust manifold 13 of the engine 1 to the intake manifold 12 of the engine 1 as EGR gas. One end on the upstream side of the EGR passage 5 is connected to the exhaust branch 3 a of the exhaust passage 3, and the other end on the downstream side of the EGR passage 5 is connected to the intake merging portion 2 b of the intake passage 2. Note that a throttle valve (not shown) for adjusting the output of the engine 1 may be provided in the intake passage 2 between the intercooler 22 and the intake merging portion 2b.

  A branch air passage 6 is branched from an intake branch portion 2 a of the downstream intake passage 2 that extends from the compressor 42 of the turbocharger 4. A part of the compressed air discharged from the compressor 42 is circulated through the branch air passage 6. The intake branch portion 2a is not particularly limited, but is preferably provided upstream of the intake merging portion 2b in the intake passage 2. The intake branch 2a is preferably provided on the upstream side of the intercooler 22 in the intake passage 2. The intercooler 22 may be provided in the intake passage 2 on the downstream side of the intake merging portion 2b.

  A gas-gas heat exchanger 7 is provided between the branch air passage 6 and the EGR passage 5. The gas-gas heat exchanger 7 is configured to transmit the thermal energy of the high-temperature EGR gas flowing through the EGR passage 5 to the compressed air flowing through the branch air passage 6 to heat the compressed air and cool the EGR gas. It is a flow type heat exchanger. A counter-flow heat exchanger is a heat exchanger in which the flow directions of two media performing heat transfer are opposite to each other. In the gas-gas heat exchanger 7, EGR gas flows through the tube side passage 71 from the tube side passage inlet 71a toward the tube side passage outlet 71b, and the compressed air passes through the shell side passage 72 and the shell side passage inlet 72a. To the shell side passage outlet 72b. At each position along the gas-gas heat exchanger 7, the thermal energy of the EGR gas having a temperature higher than that of the relatively compressed air flowing through the tube side passage 71 is relatively lower than that of the EGR gas flowing through the shell side passage 72. Is transmitted to the compressed air. Since the gas-gas heat exchanger 7 is a counter-current heat exchanger, each of the gas-gas heat exchangers along the gas-gas heat exchanger between the EGR gas and the compressed air that transfers heat while flowing in opposite directions to each other. The temperature difference at the position can be reduced, and the temperature drop in the process of transmitting the thermal energy of the EGR gas to the compressed air can be suppressed to a small value. Thereby, the thermal energy of high temperature EGR gas can be efficiently transmitted to compressed air.

  An EGR cooler 51 for further cooling the EGR gas cooled in the gas-gas heat exchanger 7 is provided in the EGR passage 5 downstream from the gas-gas heat exchanger 7. The EGR gas flowing through the EGR cooler 51 is cooled by the engine coolant flowing through the EGR cooler coolant passage 91. In the gas-gas heat exchanger 7, the high-temperature EGR gas is cooled by the compressed air, so that the required amount of cooling heat of the EGR gas in the EGR cooler 51 is greatly reduced as compared with the conventional case. For this reason, the EGR cooler used conventionally can be reduced in size, weight, and cost. In some cases, the EGR cooler that has been conventionally used can be eliminated.

  An air turbine 8 is provided in the branch air passage 6 on the downstream side of the gas-gas heat exchanger 7. The air turbine 8 is driven to rotate by hot compressed air heated by EGR gas in the gas-gas heat exchanger 7. The air turbine 8 is a radial flow turbine having a variable capacity mechanism (not shown) inside. As a variable capacity mechanism of the air turbine 8, a movable flap type in which the area of the scroll inlet is continuously variable by a movable flap, or a variable nozzle blade type in which the nozzle area is changed by swinging a variable nozzle blade provided around the impeller. Etc. are exemplified. The air turbine 8 can change the flow rate characteristic of the turbine according to the flow rate fluctuation of the compressed air flowing through the branch air passage 6, and can efficiently operate the air turbine for a wide range of compressed air flow rates.

  A generator 82 is connected to the air turbine 8 via a second connecting shaft 81, and the generator 82 is rotationally driven by the air turbine 8 to generate power. The generated electric power is stored in an electric storage device 84 such as a storage battery or a capacitor via an inverter 83, or is supplied to a motor 85 that drives auxiliary machinery 86. Between the intake merging portion 2b of the intake passage 2 and the intake manifold 12, an intake oxygen concentration sensor 24 for detecting the oxygen concentration of intake air sucked into the engine 1 and an intake pressure sensor 23 for detecting intake pressure are provided. It has been. Between the exhaust manifold 13 and the exhaust branch 3a of the exhaust passage 3, an exhaust oxygen concentration sensor 34 for detecting the oxygen concentration of the exhaust gas discharged from the engine 1, an exhaust pressure sensor 33 for detecting the exhaust pressure, An exhaust temperature sensor 35 for detecting the exhaust temperature is provided.

  An EGR valve 52 that adjusts the flow rate of EGR gas flowing through the EGR passage 5 is provided in the EGR passage 5 between the EGR cooler 51 and the intake merging portion 2b. The opening degree of the EGR valve 52 is determined based on the actual EGR rate calculated from the measured values of the intake oxygen concentration sensor 24 and the exhaust oxygen concentration sensor 34 (the ratio of EGR gas in the intake air sucked into the engine 1). Is controlled by a control device (not shown) so that the target EGR rate calculated from the number of rotations and the amount of fuel supplied to the engine 1 is obtained.

  An intake branch valve 61 is provided in the branch air passage 6 on the downstream side from the intake branch portion 2a. FIG. 2 shows an intake pressure (characteristic line a) measured by the intake pressure sensor 23, an exhaust pressure (characteristic line b) measured by the exhaust pressure sensor 33, and an intake shunt valve when the rotation speed of the engine 1 changes. This shows the opening degree 61 (characteristic line c). In order to perform EGR, it is necessary that the intake pressure is lower than the exhaust pressure by a predetermined pressure, and as shown by the characteristic line c in the figure, the change in the rotational speed of the engine 1 occurs. Accordingly, the opening degree of the intake air diversion valve 61 is controlled by a control device (not shown). By controlling the opening degree of the intake air diversion valve 61, the flow rate of the compressed air flowing into the branch air passage 6 is adjusted to enable EGR, and excess compressed air is circulated through the branch air passage 6 to increase the temperature. The thermal energy of the EGR gas is recovered as electric power. Note that the intake air diversion valve 61 is fully closed when a warm-up operation is performed at a cold start or the like of the engine system. When the temperature of the exhaust gas measured by the exhaust temperature sensor 35 provided in the exhaust passage 3 rises to a predetermined temperature or more and it is determined that the engine system has been warmed up, the intake air diversion valve 61 is opened.

  Next, the operation of the engine system of this embodiment will be described. During normal operation of the engine system according to the present embodiment (during non-idling operation after completion of warm-up), for example, 50 kW is input as heat due to fuel combustion, and from the engine 1, for example, as power 15 kW is output, and 20 kW of heat is discharged as an exhaust gas at a temperature of 800 ° C. The energy efficiency (= power output / heat input) of the engine 1 at this time is 30%.

  By controlling the opening degree of the EGR valve 52 and the intake diversion valve 61, the exhaust pressure is, for example, 0.35 MPa in absolute pressure (hereinafter, the pressure indicates the absolute pressure), and the intake pressure is increased. For example, 30% of the exhaust gas adjusted to 0.30 MPa and discharged from the engine 1 flows into the EGR passage 5 as EGR gas, and the exhaust turbine 43 is rotationally driven by the remaining 70%. In this case, 6 kW of heat flows into the EGR passage as EGR gas. Then, the compressed air is discharged from the compressor 42 rotated by the exhaust turbine 43 at, for example, a pressure of 0.32 MPa and a temperature of 150 ° C., and for example, 70% of the compressed air is directed to the engine 1 to the intercooler. The excess 30% flows into the branch air passage 6.

  The EGR gas that has flowed into the EGR passage 5 flows into the tube side passage inlet 71a of the gas-gas heat exchanger 7 at, for example, 750 ° C., and the compressed air that has flowed into the branch air passage 6 becomes a gas-gas heat exchanger. 7 flows into the shell side passage inlet 72a at 7O <0> C, for example. At each position along the gas-gas heat exchanger 7, the thermal energy of the EGR gas flowing through the tube side passage 71 having a relatively high temperature is transferred to the compressed air flowing through the shell side passage 72 having a relatively low temperature. Then, the compressed air is heated to, for example, 650 ° C. and flows out from the shell side passage outlet 72b, and the EGR gas is cooled to, for example, 200 ° C. and flows out from the tube side passage outlet 71b. Thereby, in the gas-gas heat exchanger 7, heat of, for example, 5 kW is transmitted from the EGR gas to the compressed air while being maintained at a high temperature of 650 ° C. Since the gas-gas heat exchanger 7 is a counter-current heat exchanger, the temperature drop can be suppressed to 100 ° C. in the process of transferring the thermal energy of the EGR gas to the compressed air, and the thermal energy can be efficiently used. Can communicate.

  The compressed air heated to a high temperature of 650 ° C. flows into the air turbine 8 from the branch air passage 6 and rotationally drives the air turbine 8. The pressure of the compressed air before flowing into the air turbine 8 is, for example, 0.3 MPa, and the pressure of the compressed air discharged from the air turbine 8 is, for example, 0.1 MPa. At this time, the theoretical efficiency of heat-power conversion in the air turbine 8 is 40%. The air turbine 8 can be operated at a turbine efficiency of, for example, 85% under the control of the internal variable displacement mechanism, and the actual heat-power conversion efficiency of the air turbine 8 is 34%. As a result, 1.7 kW of 5 kW heat transferred from the EGR gas to the compressed air is converted into power.

  Further, the air turbine 8 rotates the generator 82 to generate power. The generator efficiency of the generator 82 can be, for example, 88%, and 1.5 kW of power is output from the generator 82. This electric power is 3% of the heat input 50 kW to the engine 1, and when combined with 30% of the energy efficiency of the engine 1, the energy efficiency of the entire system is 33%. Based on 30% of the energy efficiency of the engine 1, the energy efficiency of the entire system is improved by 10% by recovering the thermal energy of the high-temperature EGR gas as electric power.

  The air whose pressure and temperature are reduced by driving the air turbine 8 is discharged from the air branch passage 6 to the outside.

  The EGR gas that has flowed into the EGR cooler 51 is cooled to, for example, a temperature of 100 ° C. by the engine coolant that flows through the EGR cooler coolant passage 91. The EGR gas cooled by the EGR cooler 51 passes through the EGR valve 52, merges with the compressed air cooled by the intercooler 22 in the intake air merging portion 2b, and is sucked into the engine 1.

  According to the above-described embodiment, the following operational effects can be obtained.

  In the gas-gas heat exchanger 7 provided between the EGR passage 5 and the branch air passage 6, a part of the compressed air discharged from the compressor 42 of the turbocharger 4 is circulated through the branch air passage 6. The thermal energy of the EGR gas is transmitted to the compressed air flowing through the branch air passage 6, and the air turbine 8 can be rotationally driven by the compressed air heated to a high temperature to be recovered as electric power or power. Will improve.

  Further, according to the present embodiment, a part of the compressed air discharged from the compressor 42 of the turbocharger 4 is used as the compressed air for rotating and driving the air turbine 8 by transmitting the thermal energy of the high-temperature EGR gas. To do. For this reason, unlike the system according to the conventional Patent Document 1, a device corresponding to a circulation pump for boosting the working medium is unnecessary, and the system can be reduced in size, weight, and cost. The power required for driving is also reduced, and the energy efficiency of the entire system is improved.

  Furthermore, according to the present embodiment, unlike the system according to the conventional Patent Document 1, the working medium is not water but air, which is sucked from the outside and driven to the air turbine 8 and then discharged to the outside. . For this reason, the apparatus equivalent to the condenser in the water circulation circuit which concerns on the conventional patent document 1 is unnecessary, and a system can be reduced in size, weight, and cost. Further, unlike the case of water, high airtightness is not necessary, which is advantageous for reducing the size, weight and cost of the system. Further, according to the present embodiment, unlike the system according to Patent Document 1, the working medium is air different from water and does not freeze even in a cold environment, and the system is started even in a cold environment. It is possible and the possibility of breakage can be suppressed.

(Embodiment 2)
FIG. 3 shows the concept of the second embodiment. In the engine system of the present embodiment, the air turbine 8 in the engine system of the first embodiment described above is connected to the turbocharger 4 (driven mechanism) via the second connecting shaft 81 as shown in FIG. The other configurations are the same as those of the first embodiment. The compressor 42 of the turbocharger 4 is rotationally driven by the exhaust turbine 43 of the turbocharger 4 and is also rotationally driven by the air turbine 8.

  For example, when the EGR rate is set to a large value of about 50%, the flow rate of the exhaust gas flowing into the exhaust turbine 43 of the turbocharger 4 decreases, so that the power of the exhaust turbine 43 decreases and the compressor 42 is driven. Lack of power. On the other hand, since the flow rate of the EGR gas flowing into the EGR passage 5 increases, in the gas-gas heat exchanger 7, the thermal energy transmitted to the compressed air flowing through the branch air passage 6 increases and is generated in the air turbine 8. The power to do increases.

  According to the present embodiment, in an engine system with a high EGR rate, the exhaust turbine 43 that rotationally drives the compressor 42 of the turbocharger 4 by reducing the flow rate of exhaust gas discharged from the engine 1 and flowing into the exhaust turbine 43. The decrease in power can be supplemented by the power of the air turbine 8 that is rotationally driven by compressed air heated to a high temperature with EGR gas having an increased flow rate. For this reason, the flow rate of the compressed air required for the engine 1 is ensured, operation at a high intake pressure is possible, the specific output of the engine 1 is improved, and the energy efficiency of the entire system is improved. Other functions and effects are basically the same as those of the first embodiment.

(Other)
The present invention is not limited to the embodiment described above and shown in the drawings, and can be implemented with appropriate modifications without departing from the scope of the invention. The engine system may be used for vehicles, ships, or stationary such as gas heat pumps or cogeneration. The vehicle may be a normal vehicle that uses only power from the engine as a drive source, or may be a hybrid vehicle that has both an engine and a driving motor (electric motor).

  1 is an engine, 11 is an engine structure, 12 is an intake manifold (intake part), 13 is an exhaust manifold (exhaust part), 2 is an intake passage, 2a is an intake branching part, 2b is an intake merging part, 21 is an air cleaner, 22 Is an intercooler, 23 is an intake pressure sensor, 24 is an intake oxygen concentration sensor, 3 is an exhaust passage, 3a is an exhaust branch, 31 is an exhaust purification device, 32 is a silencer, 33 is an exhaust pressure sensor, and 34 is an exhaust oxygen concentration sensor. , 35 is an exhaust temperature sensor, 4 is a turbocharger (driven mechanism), 41 is a first connecting shaft, 42 is a compressor, 43 is an exhaust turbine, 5 is an EGR passage, 51 is an EGR cooler, 52 is an EGR valve, 6 is a branch air passage, 61 is an intake air diversion valve, 7 is a gas-gas heat exchanger, 71 is a tube side passage, 71 a is a tube side passage inlet, 71 b is a tube side passage outlet, 72 Shell side passage, 72a is shell side passage inlet, 72b is shell side passage outlet, 8 is an air turbine, 81 is a second connecting shaft, 82 is a generator, 83 is an inverter, 84 is an electricity storage device, 91 is cooling for EGR cooler A liquid passage 92 is an intercooler coolant passage.

Claims (5)

An engine having an intake portion and an exhaust portion;
An intake passage for supplying intake air including air sucked from outside to the intake portion of the engine;
An exhaust passage for exhausting exhaust gas exhausted from the exhaust part of the engine to the outside;
An exhaust turbine provided in the exhaust passage and driven by exhaust gas discharged from the exhaust portion of the engine, and provided in the intake passage, driven by the exhaust turbine, and sucked into the intake passage from the outside A turbocharger having a compressor for compressing air and discharging compressed air;
An EGR passage that recirculates a part of the exhaust gas discharged from the exhaust portion of the engine to the intake portion of the engine as EGR gas, and
A branched air passage that is branched from the intake passage downstream of the compressor of the turbocharger and that circulates a part of the compressed air discharged from the compressor of the turbocharger;
The branch air passage is provided between the EGR passage and the branch air passage, and transmits the high-temperature heat energy of the EGR gas flowing through the EGR passage to the compressed air flowing through the branch air passage. A gas-gas heat exchanger that heats the compressed air flowing through the EGR passage and cools the EGR gas flowing through the EGR passage;
An air turbine provided in the branch air passage downstream from the gas-gas heat exchanger, connected to a generator or a driven mechanism and driven by the compressed air heated in the gas-gas heat exchanger; An engine system comprising:   The engine system according to claim 1, further comprising an intake air diversion valve that adjusts a flow rate of the compressed air that flows from the intake passage into the branch air passage.   The engine system according to claim 1, wherein the driven mechanism is the turbocharger.   The engine system according to any one of claims 1 to 3, wherein the gas-gas heat exchanger is a countercurrent heat exchanger.   5. The engine system according to claim 1, wherein the air turbine is a radial flow turbine having a variable capacity mechanism.

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