JP2012007500A - Exhaust heat recovery device of internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To further improve thermal efficiency by efficiently recovering exhaust heat loss and regenerating it as power in an internal combustion engine equipped with a turbocharger and an EGR system, although having a relatively simple and inexpensive configuration. Provided is an exhaust heat recovery device for an internal combustion engine.
The present invention relates to an exhaust supercharger 1100 interposed in an exhaust passage of an internal combustion engine 100, and a part of the exhaust as EGR gas by branching from an exhaust passage upstream of the exhaust supercharger 1100. An exhaust heat recovery apparatus for an internal combustion engine comprising an EGR system for recirculation to a combustion chamber of the internal combustion engine, a first heat exchanger 200 for exchanging heat between the EGR gas and the working medium, The second heat exchanger 300 that exchanges heat between the working medium flowing out from the heat exchanger 200 and the exhaust flowing out from the exhaust supercharger, and the expander 400 by the working medium flowing out from the second heat exchanger 300. The exhaust heat of the internal combustion engine is recovered by driving the engine.
[Selection] Figure 1

Description

  The present invention relates to an exhaust heat recovery device for an internal combustion engine. More specifically, the present invention relates to a technique for recovering exhaust heat of an internal combustion engine by a Rankine cycle.

  Conventionally, as this type of apparatus, for example, there is an exhaust gas waste heat recovery apparatus for an internal combustion engine as described in Patent Document 1.

  However, the exhaust gas waste heat recovery device for an internal combustion engine described in Patent Document 1 does not include a turbocharger (exhaust supercharger), and does not assume that EGR (Exhaust Gas Recirculation) is performed.

  For this reason, the technique described in Patent Document 1 cannot be applied as it is to an internal combustion engine having a turbocharger and an EGR system, and even if it can be applied as it is, exhaust heat is effectively recovered. There is a fact that it cannot be done.

  Furthermore, for example, Patent Document 2 describes an internal combustion engine having an EGR system with an energy recovery device (exhaust heat recovery device) provided with a turbocharger in the exhaust passage.

  In the internal combustion engine energy recovery device (exhaust heat recovery device) described in Patent Document 2, as shown in FIG. 2, a turbocharger 3, a downstream first heat exchanger 4, and a first heat exchanger 4. Cools the EGR control valve 7 disposed downstream, the water separator 8 provided in the intake system that sends exhaust gas from the EGR control valve 7 to the compressor 21, and the EGR gas and air sent from the compressor 21 In addition, a second heat exchanger 5 that generates steam to be fed to the first heat exchanger 4 and a steam turbine 35 that is driven by high-temperature steam generated in the first heat exchanger 4 are provided.

  In other words, the energy recovery device for an internal combustion engine described in Patent Document 2 uses hot water (using hot EGR gas compressed by the turbocharger 3 and the heat of the supply air in the second heat exchanger 5). The Rankine cycle working medium) is changed to steam, and this steam is discharged from the turbocharger 3 and recirculated to the combustion chamber of the engine, using the heat of the EGR gas in the first heat exchanger 4. The steam turbine 35 is driven by the high-temperature steam to drive the generator / motor 8 to generate power, and the steam energy is converted into electric energy to be recovered.

  Here, EGR gas refers to the concentration (exhaust amount) of nitrogen oxides (hereinafter referred to as NOx) in the exhaust gas by lowering the combustion temperature by recirculating part of the exhaust gas from the engine into the combustion chamber and recombusting it. In the so-called EGR (Exhaust Gas Recirculation) system for reducing the exhaust gas, the exhaust gas is recirculated into the combustion chamber.

Japanese Utility Model Publication No. 63-19683 JP 2001-132442 A

  However, in the energy recovery device for an internal combustion engine described in Patent Document 2, the heat of the supply air (fresh air + EGR gas) compressed by the turbocharger 3 is used in the second heat exchanger 5 for the steam turbine. Since the working medium (hot water) of 35 is vaporized into steam, it is difficult to say that exhaust heat can be effectively recovered.

  In the energy recovery device for an internal combustion engine described in Patent Document 2, a steam turbine is used in the first heat exchanger 4 by utilizing the heat of EGR gas that flows out from the turbocharger 3 and is returned to the combustion chamber of the internal combustion engine. The drive medium 35 (the steam) is a high-temperature steam, and a relatively large amount of heat is required to make the high-temperature steam, but the flow rate of the EGR gas itself is relatively small. Therefore, there is a possibility that a sufficient amount of heat cannot be supplied. In other words, there is a possibility that exhaust heat cannot be sufficiently recovered.

  The present invention has been made in view of such a situation, and efficiently recovers exhaust heat loss in an internal combustion engine equipped with a turbocharger (exhaust supercharger) and an EGR system while having a relatively simple and inexpensive configuration. It is an object of the present invention to provide an exhaust heat recovery device for an internal combustion engine that can further improve thermal efficiency by regenerating as power.

For this reason, the exhaust heat recovery device for an internal combustion engine according to the present invention is
An exhaust supercharger interposed in the exhaust passage of the internal combustion engine;
An EGR system that branches from the exhaust passage upstream of the exhaust supercharger and recirculates a part of the exhaust as EGR gas to the combustion chamber of the internal combustion engine;
An exhaust heat recovery device for an internal combustion engine comprising:
A first heat exchanger that exchanges heat between the EGR gas and the working medium;
A second heat exchanger that exchanges heat between the working medium flowing out from the first heat exchanger and the exhaust flowing out from the exhaust supercharger;
The exhaust heat of the internal combustion engine is recovered by driving the expander with the working medium flowing out from the second heat exchanger.

  In the present invention, a power generator is connected to the expander, an electric motor is driven by electric energy obtained by driving the power generator, and the output of the electric motor is regenerated as power to the shaft output of the internal combustion engine. It can be characterized by that.

  According to the present invention, in an internal combustion engine equipped with a turbocharger (exhaust supercharger) and an EGR system, the exhaust heat loss is efficiently recovered and regenerated as power in a relatively simple and inexpensive configuration. An exhaust heat recovery device for an internal combustion engine and an exhaust heat power regeneration device for the internal combustion engine that can further improve the thermal efficiency can be provided.

It is the figure which showed roughly an example of the whole structure of the exhaust-heat-recovery apparatus of the internal combustion engine provided with the turbocharger and EGR system which concern on one embodiment of this invention. It is the figure which showed roughly an example of the whole structure of the exhaust-heat-recovery apparatus of the internal combustion engine provided with the conventional turbocharger and the EGR system.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. The present invention is not limited to the embodiments described below.

FIG. 1 shows an overall configuration of an internal combustion engine 100 provided with an exhaust heat recovery device (exhaust heat power regeneration device) according to the present embodiment.
A device that recovers exhaust heat of the internal combustion engine is referred to as an exhaust heat recovery device of the internal combustion engine, and a device including a configuration that regenerates the exhaust heat of the internal combustion engine as power is referred to as an exhaust heat power regeneration device of the internal combustion engine.

  In FIG. 1, an inline four-cylinder diesel combustion engine (engine) is illustrated as the internal combustion engine 100, but is not limited thereto.

  In the internal combustion engine 100 provided with the exhaust heat recovery apparatus according to the present embodiment, exhaust heat loss is recovered by Rankine cycle and used for power generation, and an electric motor is driven by the electric energy obtained by this power generation to drive the internal combustion engine. It is configured to regenerate as 100 shaft outputs (crankshaft outputs).

  More specifically, as shown in FIG. 1, in the present embodiment, a part of the exhaust gas of the internal combustion engine 100 is led as an EGR gas to an evaporator 200 that is a first heat exchanger. It is like that.

  In the evaporator 200, the compressed liquid (for example, hot water) that is the working medium of the exhaust heat recovery system (Rankine vacuum) is evaporated using the heat of the EGR gas.

  Note that the EGR gas that has been deprived of heat by the evaporator 200 and is cooled is led to the intake passage of the internal combustion engine 100 and led to the combustion chamber along with the supply air to be recombusted. However, such EGR is performed. Thus, the combustion temperature is reduced and the NOx emission amount in the exhaust gas is reduced.

  In the exhaust heat recovery apparatus for the internal combustion engine 100 according to the present embodiment, the working medium is compressed by the compressor (electric pump or the like) 600, and the evaporator 200, the superheater 300, the expander (steam turbine) 400, and the condenser 500. Is circulated in the exhaust heat recovery system (Rankine cycle), in which the steam as the working medium is cooled by the condenser 500 to be compressed (hot water). After the hot water is vaporized into steam and further converted into superheated steam by the superheater 300, the steam is sent to the expander (steam turbine) 400 and the generator 700 is driven to convert the steam energy into electrical energy. The generated electric energy is regenerated as power of the internal combustion engine 100 by the electric motor 800.

  In superheater 300 (second heat exchanger) according to the present embodiment, exhaust heat is applied to the steam sent from evaporator 200 to superheat the superheated steam. Here, a turbocharger (exhaust supercharger) is used. ) 1100 is used for the supercharging work, and the heat of the exhaust gas flowing out from the turbocharger (exhaust supercharger) 1100 is used.

  The working medium converted to superheated steam by the superheater 300 is guided to an expander (steam turbine) 400, where the turbine is driven to rotate to drive the generator 700.

  In the present embodiment, steam energy (exhaust heat) is converted into electrical energy in the generator 700, while the electric motor 800 is driven by this electrical energy, whereby exhaust heat is efficiently recovered and the shaft output of the internal combustion engine 100 is output. It is regenerated as power connected to (crankshaft output).

  Note that the condenser 500 (third heat exchanger) according to the present embodiment includes an intercooler (heat exchanger) 1000 for cooling the high-temperature supply air compressed by the turbocharger 1100, and an internal combustion engine. 100, a cooling medium (cooling water), and a radiator (heat exchanger) 1200 that cools the cooling medium (cooling water), and can be cooled by a cooling fan 900 driven by the internal combustion engine 100.

  However, the condenser 500 according to the present embodiment can also be configured to be cooled by an electric fan (not shown) or / and a cooling structure by blowing cooling water.

  As shown in FIG. 1, the cooling medium (cooling water) cooled by the radiator 1200 is pumped by the water pump 1300 and cools the internal combustion engine 100 through a cooling passage such as a water jacket of the internal combustion engine 100. Then, it is circulated again to the radiator 1200.

  Of course, a thermostat (not shown) may be interposed in the circulation path of the cooling medium, and the structure in which the warming-up of the internal combustion engine 100 is promoted can be configured to bypass the radiator 1200 when the cooling medium is at a predetermined temperature or lower. It is.

  As described above, in the exhaust heat recovery apparatus for the internal combustion engine 100 according to the present embodiment, the compressed liquid, which is the working medium of the Rankine cycle, is evaporated by the heat of the EGR gas in the evaporator 200, and then the superheater 300 Then, it is superheated by the heat of the exhaust gas to form superheated steam, and the superheated steam is expanded by the expander 400 to regenerate the exhaust heat of the internal combustion engine 100 as power, and the expander 400 expands the superheated steam to expand. Since it becomes steam and is cooled by the condenser 500 to be liquefied into a condensate, and the condensate is compressed by the compressor 600 to become a compressed liquid again, the EGR gas is effective in the evaporator 200. The heat of the EGR gas can be effectively recovered while being cooled, and the heat of the exhaust gas flowing out from the turbocharger 1100 is effectively recovered by the superheater 300. Can, it is possible to realize an exhaust heat recovery apparatus can be recovered efficiently exhaust heat loss in the internal combustion engine provided with a turbocharger and (exhaust turbocharger) and EGR system Te Tsu.

  Further, according to the exhaust heat recovery apparatus for the internal combustion engine 100 according to the present embodiment, the exhaust heat can be efficiently recovered as described above. Therefore, the recovered exhaust heat can be efficiently regenerated as power. As a result, the thermal efficiency of the internal combustion engine 100 can be further improved.

  In the present embodiment, the EGR gas can be effectively cooled by the evaporator 200, so that an EGR gas cooler system (a heat exchanger, a cooling medium passage, etc.) provided separately in the past is omitted. Therefore, the configuration can be simplified, the apparatus can be reduced in size and weight, and the production efficiency can be promoted by reducing the cost and reducing the number of parts.

  By the way, in the present embodiment, the recovered exhaust heat is used to drive the expander (steam turbine) 400 and then the generator 700, and the electric energy obtained thereby is transferred to the internal combustion engine 100 via the electric motor 800. However, the present invention is not limited to this. For example, the power can be regenerated as power of PTO (Power Take Off).

  Further, the present invention is not limited to the above-described configuration, and without converting the recovered exhaust heat into electric energy and regenerating it to the shaft output (crankshaft output) of the internal combustion engine 100 via the electric motor 800, For example, the rotation of an expander (steam turbine) 400 that is driven using the recovered exhaust heat is directly applied to the crankshaft (output shaft) of the internal combustion engine via a speed reducer, speed increaser, continuously variable transmission, or the like. Or it can also be set as the structure which regenerates as motive power of PTO (Power Take Off).

  In the present embodiment, the case where water (utilizing phase change such as hot water, steam, superheated steam, etc.) is used as the working medium of the exhaust heat recovery device (Rankine cycle) is described. The working medium is not limited, and other working media can be adopted according to demands.

  The internal combustion engine 100 is not limited to a diesel engine. For example, the internal combustion engine 100 can be a gasoline engine or another internal combustion engine, and the present invention is applicable to all mobile and stationary internal combustion engines regardless of the combustion system. Is possible.

  In addition, the fuel supplied to the internal combustion engine is not particularly limited. In addition to fossil fuels such as light oil, gasoline, alcohol, and LNG (Liquid Natural Gas), for example, biofuel or fuel mixed with biofuel (for example, The present invention can also be applied to a combustion apparatus that uses biofuel mixed light oil, biofuel mixed gasoline, etc.) as fuel.

  In the present embodiment, the case where the EGR gas cooling (cooler) system is omitted is illustrated, but the present invention is not limited to this, and an EGR gas cooler system is appropriately installed according to demands and the like. Is also possible.

  Incidentally, in the exhaust heat recovery apparatus for the internal combustion engine 100 according to the present embodiment, the EGR control valve interposed in the EGR gas passage through which the EGR gas flows is omitted in FIG. An EGR control valve (an opening adjusting valve for adjusting the amount of EGR gas flowing through the EGR gas passage) or a one-way valve that suppresses the supply air from flowing into the EGR gas passage can be installed in the passage. It is.

  The embodiment described above is merely an example for explaining the present invention, and changes can be appropriately made without departing from the gist of the present invention.

  The exhaust heat recovery device for an internal combustion engine according to the present invention is an arrangement that is relatively simple and inexpensive, but efficiently recovers exhaust heat loss in an internal combustion engine equipped with a turbocharger (exhaust supercharger) and an EGR system. It is beneficial to improve the thermal efficiency by regenerating as power.

100 Internal combustion engine 200 Evaporator (first heat exchanger)
300 Superheater (second heat exchanger)
400 Expander (steam turbine)
500 Condenser (third heat exchanger)
600 Compressor 700 Generator 800 Electric motor 900 Cooling fan 1000 Intercooler 1100 Turbocharger (exhaust supercharger)
1200 Radiator 1300 Water Pump

Claims (2)

An exhaust supercharger interposed in the exhaust passage of the internal combustion engine;
An EGR system that branches from the exhaust passage upstream of the exhaust supercharger and recirculates a part of the exhaust as EGR gas to the combustion chamber of the internal combustion engine;
An exhaust heat recovery device for an internal combustion engine comprising:
A first heat exchanger that exchanges heat between the EGR gas and the working medium;
A second heat exchanger that exchanges heat between the working medium flowing out from the first heat exchanger and the exhaust flowing out from the exhaust supercharger;
An exhaust heat recovery apparatus for an internal combustion engine that recovers exhaust heat of the internal combustion engine by driving the expander with a working medium flowing out from the second heat exchanger.   A generator is connected to the expander, an electric motor is driven by electric energy obtained by driving the generator, and the output of the electric motor is regenerated as power to the shaft output of the internal combustion engine. The exhaust heat recovery device for an internal combustion engine according to claim 1, wherein the exhaust heat recovery device is an internal combustion engine.

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