JP2004084564A - Exhaust heat recovering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To take out exhaust heat energy from a process of isothermal expansion wherein working fluid is expanded by exhaust heat, based on the principle of the Ericsson cycle whereby isothermal expansion, isothermal compression, isobaric heating and isobaric cooling are repeated. <P>SOLUTION: This exhaust heat collecting device is equipped with a heat engine 10 to discharge exhaust, a compressor part 1 to discharge working fluid sucked by applying isothermal compression to it, a reproducer 2 to apply isobaric heating to the working fluid by heat of the exhaust and to apply isobaric cooling to the exhaust by the working fluid, and an expander part 3 to apply isobaric expansion to the working fluid by heat of the exhaust, which is obtained by heat exchange between the working fluid and the exhaust. Kinetic energy of a moving body 16 actuated by expansion of the working fluid in the expander part 3 is taken out from an output part 4. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an exhaust heat recovery device.
[0002]
[Prior art]
In general, an exhaust turbine driven by using the exhaust gas as a working medium, and an internal combustion engine that operates by rotating the exhaust turbine to pressurize intake air to use the energy of exhaust gas of an internal combustion engine mounted on a vehicle or the like. Turbochargers equipped with a compressor for supplying the exhaust gas are widely used, but when the load of the internal combustion engine is a partial load or at a low speed, the amount of exhaust is small, and it is difficult to efficiently use exhaust energy.
[0003]
Further, Japanese Patent Application Laid-Open No. 6-288242 discloses a turbocharger having a turbine driven by exhaust gas energy and a compressor attached to a shaft provided in the turbine. In this turbocharger, an outer shaft rotatable independently of a shaft provided on the same central axis on the outer periphery of the shaft, a power generation turbine driven by exhaust gas energy provided on the outer shaft, and a power generator provided on the outer shaft There is disclosed a generator having a generator rotor, wherein the turbine and the power generation turbine are arranged in series in an exhaust gas flow.
[0004]
According to the turbocharger having such a configuration, the first-stage turbine and the second-stage turbine are provided on the same central axis in the exhaust system. An exhaust pipe to be connected is not required, heat is not dissipated through the exhaust pipe, and no mechanical loss occurs, and highly efficient exhaust energy can be recovered as electric energy.
[0005]
[Problems to be solved by the invention]
However, in the exhaust energy recovery mechanism such as the turbocharger, since the turbine is rotated by the flow of the exhaust gas, the flow of the exhaust gas is hindered by the resistance of the turbine and the smooth flow is stopped. . In such a case, since the exhaust pressure increases and pumping loss of the heat engine occurs, the efficiency of the heat engine itself decreases.
[0006]
Comparing the recovered energy with the loss due to the decrease in the efficiency of the heat engine, the amount of exhaust energy that can be effectively used as a whole is small. It is.
[0007]
The present invention focuses on recovering the thermal energy of the exhaust without obstructing the flow of the exhaust, and has been completed to realize efficient exhaust heat recovery without reducing the efficiency of the heat engine. It was done. That is, an object of the present invention is to provide an exhaust heat recovery device capable of efficiently recovering exhaust heat.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is based on the principle of the Ericsson cycle in which isothermal expansion, isothermal compression, isothermal heating, and isostatic cooling are repeated. It extracts heat energy and is configured as follows to solve the above technical problem.
[0009]
That is, a heat engine that discharges exhaust gas,
A compressor section for isothermally compressing and sucking out the sucked working fluid,
A regenerator that contacts the working fluid and the exhaust gas that have been isothermally compressed and heats the working fluid with the heat of the exhaust gas at the same pressure, and simultaneously cools the exhaust gas with the working fluid and then discharges the exhaust gas to the outside;
The heat exchange between the working fluid heated at the same pressure and the exhaust gas discharged from the heat engine causes the working fluid to expand at a constant pressure by the heat of the exhaust gas. An expander section discharging to the regenerator;
An output unit for extracting the kinetic energy of the moving body that performs a predetermined operation by expanding and discharging the working fluid in the expander unit;
With
A part of the exhaust heat energy obtained from the output section is used for isothermally compressing the working fluid in the compressor section.
[0010]
The working fluid sucked into the device expands due to the heat of the exhaust gas discharged from the heat engine, and the exhaust heat energy can be extracted from the expander unit that performs such an isothermal expansion process. For example, the alternator connected thereto can be moved by the operation of the piston reciprocating by the exhaust heat energy. The electric power generated by the alternator can be supplied to each part of the vehicle, and the alternator directly driven by the rotation of the conventional internal combustion engine is eliminated, the generated electricity is used for driving a cooling device, or the electric power is used. It is possible to reuse exhaust heat energy by storing electricity in a battery. In particular, in a hybrid car, that is, a vehicle driven by mounting both a traveling motor and an internal combustion engine, the generated electricity can be directly supplied to the motor and used for driving the motor.
[0011]
As the heat engine, various types of internal combustion engines such as a gasoline engine and a diesel engine, or various types of exhaust gas having heat energy, such as a gas turbine, can be used.
[0012]
The compressor section and the expander section each include a cylinder, a reciprocating piston provided in the cylinder, an intake valve for sucking a working fluid into the cylinder, and a discharge valve for discharging the working fluid. Can be provided.
[0013]
In this case, the intake valve and the exhaust valve can be set so as to be opened and closed by a valve mechanism linked to a crankshaft rotating via a crankshaft connected to a piston. That is, similar to the operation of the intake / exhaust valve provided in the cylinder of a normal internal combustion engine, the opening / closing of the intake / exhaust valve is synchronized with the movement of the piston so that the intake valve is opened in the intake stroke and the exhaust valve is opened in the exhaust stroke. be able to.
[0014]
In addition, since the operating body is a piston that rotates the crankshaft, power may be generated by operating an alternator or the like connected to the crankshaft.
[0015]
The expander unit is in contact with the exhaust immediately after being discharged from the heat engine on the outer wall of the cylinder where the working fluid is sucked, and the heat of the exhaust is transmitted to the working fluid via fins provided on the outer wall, It is preferable to adopt a structure in which heat exchange is performed between the working fluid and the exhaust gas, and the working fluid in the cylinder expands.
[0016]
Further, by controlling the output pressure of the compressor section based on the exhaust gas temperature and / or the exhaust gas flow rate of the heat engine so as to optimize the exhaust heat recovery efficiency, the operation is performed in a region where the exhaust heat recovery efficiency is highest. be able to.
[0017]
The output pressure of the compressor section can be controlled by changing the opening / closing timing of an intake / exhaust valve provided in a cylinder. For example, by making the timing of closing the intake valve earlier or later than the piston in the compressor reaching the bottom dead center, the amount of air to be compressed decreases, so the pressure in the cylinder decreases and the compressor section Output pressure can be reduced.
[0018]
Further, when the exhaust valve is opened early when the piston in the compressor is located near the top dead center, the output pressure of the compressor section increases.
[0019]
In order to perform such control, it is possible to use a valve mechanism in which the opening / closing degree and the opening / closing timing are variable. Alternatively, a device for opening and closing an independent valve such as an electromagnetically driven valve can be separately provided.
[0020]
According to the present invention, it is possible to recover the heat energy of the exhaust gas without obstructing the flow of the exhaust gas. Therefore, it is possible to efficiently recover the exhaust heat without significantly reducing the operation efficiency of the heat engine itself. Is possible.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an exhaust heat recovery apparatus of the present invention will be described in detail with reference to an embodiment shown in the drawings.
[0022]
FIG. 1 is an overall view showing an outline of an exhaust heat recovery device.
[0023]
The exhaust heat recovery apparatus 30 includes an internal combustion engine 10 that discharges exhaust gas, a compressor unit 1 that compresses and discharges a suctioned working fluid at an isothermal temperature, a regenerator that performs constant pressure cooling of the exhaust gas, and heats the working fluid at a constant pressure. 2, an expander unit 3 for isothermally expanding the working fluid, and an output unit 4 for extracting thermal energy of exhaust gas from the expander unit 3.
[0024]
Here, the internal combustion engine 10 is a gasoline engine mounted on a vehicle. Of course, the internal combustion engine 10 may be a diesel engine or any other engine, as long as it exhausts exhaust gas after burning fuel to an exhaust pipe.
[0025]
The compressor section 1 includes a reciprocating compression piston 5 provided in a cylindrical cylinder 6. For the operation of the piston 5, a part of the energy extracted from the exhaust gas discharged from the internal combustion engine 10 via the output unit 4 is used as described later. The piston 5 can reciprocate up and down in the cylinder 6 via an electric motor (not shown) and a crankshaft 12 connected to a rotating shaft thereof.
[0026]
The cylinder 6 is connected to an intake pipe 12 for sucking a working fluid into the cylinder 6 and a delivery pipe 13 for sending the working fluid from the cylinder. Further, an intake valve 7 for opening and closing the opening of the intake pipe 12 and a discharge valve 8 for opening and closing the opening of the delivery pipe 13 are provided in the cylinder 6.
[0027]
Each of the intake valve 7 and the exhaust valve 8 is set to open and close by a valve mechanism that operates in conjunction with the rotation of a crankshaft 15 that rotates via a crankshaft 14 connected to the piston 5.
[0028]
That is, similarly to the operation of the intake and exhaust valves provided in the cylinder of the internal combustion engine, the intake valve 7 opens during the intake stroke, and the intake valve 7 and the exhaust valve 8 close during the compression stroke. In the exhaust stroke, the exhaust valve 8 is opened and opened and closed in synchronization with the movement of the piston 5 by the rotation of the crankshaft 15.
[0029]
In this way, when the piston 5 moves toward its bottom dead center, the intake valve 7 opens to suck working fluid, here air, from the outside into the cylinder 6 via the intake pipe 12. Next, when the piston 5 reaches the bottom dead center, the intake valve 7 is closed. Thereafter, the piston 5 moves toward the top dead center, and the air in the cylinder 6 is compressed.
[0030]
When the piston 5 approaches the top dead center, the exhaust valve 8 opens, and the compressed air is discharged to the delivery pipe 13. By repeating such an operation, the compressor unit 1 isothermally compresses the sucked air.
[0031]
The compressed air flows toward the expander section 3 via the delivery pipe 13, and the delivery pipe 13 intersects the exhaust pipe 11 discharged from the internal combustion engine 10 at an intermediate portion with the expander section 3. Thus, a regenerator 2 for performing heat exchange is formed.
[0032]
The regenerator 2 has a structure similar to a normal heat exchanger as shown in FIG. In the regenerator 2, the delivery pipe 13 is reciprocated and bent a number of times, and the outer periphery thereof is covered by a shield 27 that is connected to the exhaust pipe 11 upstream and downstream, respectively, and that forms a space shielded from the outside air. . A large number of fins 9 having a heat transfer function are provided on the outer periphery of the delivery pipe 13 covered by the shield 27.
[0033]
Therefore, the heat of the exhaust gas flowing in the shield 27 is transferred to the air, which is the working fluid flowing in the delivery pipe 13, via the fins 9, so that heat can be exchanged between them.
[0034]
With the regenerator 2 having such a structure, the air as the working fluid is heated at the same pressure and, at the same time, the exhaust gas is cooled at the same pressure.
[0035]
Next, the structure of the expander unit 3 will be described. This has a reciprocating compression second piston 16 provided in a cylindrical cylinder 17 similarly to the structure of the compressor section 1 described above. The operation of the second piston 16 is transmitted to the rotation shaft of the alternator 4 via the second crankshaft 18.
[0036]
The second cylinder 17 is connected to a delivery pipe 13 for sucking air serving as a working fluid into the second cylinder 17, and a discharge path for discharging the air from the second cylinder 17. 19 are connected.
[0037]
Further, the second cylinder 17 is provided with a second intake valve 20 for opening and closing an opening of the delivery pipe 13 and a second exhaust valve 20 for opening and closing an opening of the discharge passage 19.
[0038]
The second intake valve 20 and the second exhaust valve 21 are, similarly to the intake / exhaust valve of the compressor section 1 described above, a valve mechanism that is linked to a second piston 16 and that is linked to a second crankshaft 18 that rotates. It is set to open and close.
[0039]
Therefore, when the second intake valve 20 opens and the second piston 16 descends from the top dead center, the working fluid is sucked into the second cylinder 17 and both the second intake valve 20 and the second exhaust valve 21 are closed. In this state, the second piston 16 further descends to the bottom dead center due to the expansion of the working fluid due to heat exchange. Thereafter, the second exhaust valve 21 is opened to discharge the expanded working fluid to the outside of the second cylinder 17.
[0040]
A large number of second fins 23 are provided on the outer peripheral surface of the second cylinder 17. Further, a heat exchange part 24 to which the exhaust pipe 11 is connected is formed, and this heat exchange part 24 covers the periphery of the upper part of the second cylinder 17. The heat exchange section 24 is provided with an exhaust inlet 25 into which exhaust gas flows from the exhaust pipe 11 and an outlet 26 through which exhaust gas flows out into the exhaust pipe 11.
[0041]
Since the expander section 3 has such a structure, the expander section 3 flows from the delivery pipe 13 to the outer wall of the second cylinder 17 into which the working fluid is sucked via the second intake valve 20, and flows from the exhaust pipe 11 to the heat exchange section 24. Exhaust exhaust contacts. This exhaust gas has a high temperature because it is immediately after being exhausted from the internal combustion engine 10. The heat of the exhaust gas is transmitted to the working fluid via the second fins 23 provided on the outer wall of the second cylinder 17, so that heat can be exchanged between the working fluid and the exhaust gas.
[0042]
As a result, the working fluid in the second cylinder 17 expands, and the second piston 16 is pushed down, so that the alternator 4 rotates, so that power can be generated. Electricity from the alternator 4 is supplied to external parts of the vehicle (not shown) as indicated by an arrow C, and a surplus is charged to a battery. That is, in this embodiment, the conventional alternator that is connected to the rotation shaft of the internal combustion engine 10 and that is rotated by directly transmitting the rotation of the internal combustion engine 10 is eliminated, and the reciprocating motion of the second piston 16 that operates by exhaust heat. Only the alternator 4 rotating by the rotation is provided.
[0043]
Part of the electricity generated by the alternator 4 is used to operate the piston 5 of the compressor unit 1 via a motor (not shown) to compress the working fluid drawn into the cylinder 6.
(Flow and action of exhaust and working fluid)
Next, the operation of each part will be described while explaining the flow of exhaust gas and working fluid in this embodiment.
[0044]
The flow of exhaust gas discharged from the internal combustion engine 10 is indicated by an arrow A, and the flow of working fluid is indicated by an arrow B.
[0045]
Exhaust gas discharged from the internal combustion engine 10 passes through the exhaust path 11 and contacts the outer peripheral surface of the second cylinder 17 constituting the expander unit 3. On the other hand, when the second intake valve 20 is opened, the working fluid is sucked into the second cylinder 17. After the intake, when the second intake valve 20 is closed, the working fluid is heated by the heat of the exhaust transmitted through the second fins 23 and expands in the second cylinder 17, so that the second piston 16 Depressed. When the second piston 16 is depressed, its kinetic energy is transmitted to the second crankshaft 18 via the second connecting rod 22 to operate the alternator 4 as described above.
[0046]
The expanded working fluid is discharged into the discharge passage 19 by opening the second exhaust valve 21, the working fluid flows from the discharge passage 19 into the exhaust pipe 11, and mixes with the exhaust discharged from the internal combustion engine 10. The exhaust pipe 11 flows down. The exhaust gas mixed with the working fluid is discharged to the outside through equal pressure cooling by heat exchange in the regenerator 2.
[0047]
On the other hand, air as a working fluid is sucked into the cylinder 6 of the compressor section 1, is isothermally compressed, and reaches the regenerator 2 via the discharge pipe 13. As described above, in the regenerator 2, the working fluid is heated into the cylinder 17 of the expander unit 3 after the working fluid is heated at the same pressure. By such an operation, circulation of isothermal expansion, isothermal heating, isostatic cooling, and isothermal compression is formed, and exhaust heat from the internal combustion engine is recovered.
[0048]
Further, there is a relationship as shown in FIG. 3 between the exhaust gas temperature Tf or the exhaust gas flow rate Gex discharged from the internal combustion engine 10, the output pressure P1 of the compressor unit 1, and the recovery efficiency. That is, when the exhaust gas temperature Tf is high or the exhaust gas flow rate Gex is large, the recovery efficiency is high. However, by controlling the output pressure P1, the area inside the cylinder 6 is controlled so that the most efficient exhaust heat recovery can be performed. By changing the pressure, the operation of the exhaust heat recovery device can be controlled.
[0049]
Therefore, the pressure in the cylinder 6 is changed by adjusting the opening / closing timing or the opening / closing degree of the intake valve 7 and the exhaust valve. Here, for example, if the opening of the intake valve 7 is reduced during intake of the working fluid, the pressure in the cylinder 6 is reduced. Further, by opening the exhaust valve 8 at the time of suction, the pressure in the cylinder 6 can be reduced. The output pressure P1 of the cylinder 6 can be controlled by such adjustment of the intake and exhaust valves. Such adjustment of the intake valve 7 and the exhaust valve 8 is performed by storing a map of the relationship between the exhaust gas temperature Tf, the exhaust gas flow rate Gex, and the output P1 as shown in FIG. 3 in an electronic control unit (ECU) of the vehicle (not shown). In addition, by adopting a variable valve operating mechanism or an electromagnetically driven valve, the modification timing and the degree of opening and closing of the intake and exhaust valves are adjusted by an instruction of the ECU, and the most efficient output is performed based on the operating state of the internal combustion engine 10. It is preferable to set the pressure P1.
[0050]
In this embodiment, the generated exhaust heat is used to generate electric power and supply the electric power to various parts of the vehicle. However, this electric power can be used for the operation of the cooler or used for other purposes. Needless to say. Further, the operation of the piston by the exhaust heat taken out from the expander unit 3 can be used in another form without converting it into electricity.
[0051]
By using the exhaust heat recovery device of this embodiment, the heat of the exhaust gas that has been conventionally discarded to the outside can be effectively used, and the energy efficiency of the entire vehicle equipped with the internal combustion engine can be increased. .
[0052]
Further, regardless of the operation state of the internal combustion engine, exhaust heat recovery is possible if the exhaust gas temperature is equal to or higher than a predetermined temperature. In particular, even if the internal combustion engine is at a low rotation speed, effective exhaust energy can be recovered.
[0053]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the thermal energy which exhaust has can be effectively collect | recovered. At that time, the exhaust pressure is increased by obstructing the flow of the exhaust gas, and the efficiency of the heat engine is not reduced.
[0054]
Further, by controlling the output pressure of the compressor section, it is possible to perform operation control with the highest recovery efficiency.
[Brief description of the drawings]
FIG. 1 is a view schematically showing an exhaust heat recovery device according to an embodiment of the present invention.
FIG. 2 is a view showing a structure of a regenerator of the exhaust gas recovery apparatus according to one embodiment of the present invention.
FIG. 3 is a map diagram showing a relationship between an exhaust gas temperature Tf, an exhaust gas flow rate Gex, and an output P1 of a compressor section.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Compressor part 2 Regenerator 3 Expander part 4 Output part 5 Piston 6 Cylinder 7 Intake valve 8 Exhaust valve 9 Fin 10 Internal combustion engine 11 Exhaust pipe 12 Intake pipe 13 Delivery pipe 14 Connecting rod 15 Crankshaft 16 Second piston 17 Second cylinder 18 Second crankshaft 19 Discharge path 20 Second intake valve 21 Second exhaust valve 22 Second connecting rod 23 Second fin 24 Heat exchange unit 25 Inlet 26 Outlet 27 Shield 30 Exhaust heat recovery device

Claims (5)

A heat engine that emits exhaust gas,
A compressor section for isothermally compressing and sucking out the sucked working fluid,
A regenerator that contacts the working fluid and the exhaust gas that have been isothermally compressed and heats the working fluid with the heat of the exhaust gas at the same pressure, and simultaneously cools the exhaust gas with the working fluid and then discharges the exhaust gas to the outside;
The heat exchange between the working fluid heated at the same pressure and the exhaust gas discharged from the heat engine causes the working fluid to expand at a constant pressure by the heat of the exhaust gas. An expander section discharging to the regenerator;
An output unit that extracts a kinetic energy of a moving body that performs a predetermined operation by expanding and discharging the working fluid in the expander unit;
With
A part of the exhaust heat energy obtained from the output part is used for isothermally compressing the working fluid in the compressor part. The compressor section and the expander section,
A cylinder,
A reciprocable piston provided in the cylinder,
An intake valve for sucking a working fluid into the cylinder,
An exhaust valve for discharging the working fluid;
The exhaust heat recovery device according to claim 1, further comprising: In the expander section, the exhaust gas comes into contact with the outer wall of the cylinder that sucks the working fluid, and the heat of the exhaust gas is transmitted to the working fluid via the fins provided on the outer wall, thereby exchanging heat between the working fluid and the exhaust gas. The exhaust heat recovery device according to claim 2, wherein the operation is performed, and the working fluid in the cylinder expands. The exhaust gas according to any one of claims 1 to 3, wherein the output pressure of the compressor unit is controlled based on the exhaust gas temperature and / or the exhaust gas flow rate of the heat engine so that the exhaust heat recovery efficiency is optimized. Heat recovery device. The exhaust heat recovery device according to claim 4, wherein the output pressure of the compressor unit is controlled by changing the opening / closing timing of an intake valve and an exhaust valve provided in a cylinder.

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