JP6298370B2 - Waste heat recovery device - Google Patents

Description

  The present invention relates to a waste heat recovery apparatus.

  Waste heat recovery technology in vehicles and the like is an effective means for improving fuel efficiency, and conventionally, a waste heat recovery apparatus using a Rankine cycle system that recovers waste heat from engine coolant is known. As this type of technology, for example, Patent Document 1 below discloses a Rankine cycle system mounted on a vehicle, which uses an evaporator that heats and evaporates a working medium, and a working medium that is evaporated by the evaporator. An expander for generating power, a condenser for cooling and condensing the working medium used for power generation by the expander, and a pump for compressing the working medium condensed by the condenser and sending it to the evaporator Are listed.

JP 2014-37774 A

  In the meantime, in the above-described waste heat recovery apparatus, the working medium can be cooled to the outside temperature by the condenser of the Rankine cycle system, but it is not easy to cool the working medium to a temperature lower than that. For this reason, in the above-described waste heat recovery apparatus, it is required to increase the condensation capacity of the working medium in the Rankine cycle system and improve the waste heat recovery efficiency.

  This invention is made | formed in view of the said situation, and makes it a subject to provide the waste heat recovery apparatus which can improve waste heat recovery efficiency.

  In order to solve the above problems, a waste heat recovery apparatus according to the present invention includes a Rankine cycle system that uses the heat of cooling water of an engine and an EGR cooler as a heat source, and a sound wave in the acoustic tube using the heat of the exhaust gas of the engine as a heat source. And a thermoacoustic cooling device that cools the first room temperature heat exchanger with the cooling heat exchanger disposed via the first stack, the cooling heat exchanger being a working medium for the Rankine cycle system. Allow to cool and condense.

  In this waste heat recovery device, the thermal energy of the engine exhaust gas can be converted into cooling energy by the thermoacoustic cooling device. The cooling energy can be used to cool and condense the working medium of the Rankine cycle system (that is, the cooling heat exchanger of the thermoacoustic cooling device can function as a condenser of the Rankine cycle system). It becomes. Therefore, in the Rankine cycle system, it is possible to cool the working medium to a temperature lower than the outside air temperature and increase its condensing capacity. As a result, waste heat recovery efficiency can be improved.

  Specifically, the thermoacoustic cooling device inputs the heat of the exhaust gas of the engine to the high-temperature heat exchanger, and the high-temperature heat exchanger and the second room-temperature heat exchanger A sound wave may be generated in the acoustic tube by applying a temperature difference to the second stack disposed between the two.

  In the Rankine cycle system, the working medium may be cooled and condensed only by the cooling heat exchanger. In this case, a so-called conventional condenser (for example, a condenser using cooling water cooled by a sub-radiator as a cooling heat source) can be eliminated, and the apparatus can be miniaturized.

  ADVANTAGE OF THE INVENTION According to this invention, the waste heat recovery apparatus which can improve waste heat recovery efficiency can be provided.

It is a schematic block diagram which shows the waste heat recovery apparatus which concerns on one Embodiment of this invention. It is a schematic block diagram which shows the modification of the waste heat recovery apparatus of FIG.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals, and redundant description will be omitted.

  FIG. 1 is a schematic configuration diagram showing a waste heat recovery apparatus according to an embodiment of the present invention. As shown in FIG. 1, the waste heat recovery apparatus 100 of the present embodiment further combines a thermoacoustic cooling apparatus 30 that performs cooling using a thermoacoustic phenomenon in a system that combines a Rankine cycle system 20 with an engine 10. It is mounted on the vehicle.

  Examples of the vehicle to be applied include commercial vehicles such as trucks and buses. The vehicle is not particularly limited, and may be a large vehicle, a medium vehicle, a normal passenger vehicle, a small vehicle, a light vehicle, or the like. For example, a diesel engine or a gasoline engine is used as the engine 10. The engine 10 here is a vehicle driving engine, but may be a dedicated engine different from that.

  The engine 10 has an EGR system that returns a part of the exhaust gas to the intake side as EGR (Exhaust Gas Recirculation) gas, for example, in order to reduce NOx (nitrogen oxide) in the exhaust gas and improve fuel efficiency. The engine 10 is provided with an EGR cooler 11 that is a heat exchanger for cooling the EGR gas. Cooling water W for cooling the engine 10 and cooling the EGR gas is circulated through the engine 10 and the EGR cooler 11 so as to circulate. The circulating cooling water W is radiated by the radiator 12 and cooled.

  The Rankine cycle system 20 is a power generation system using the Rankine cycle, and operates using the cooling water W of the engine 10 and the EGR cooler 11 as a heat source. The Rankine cycle system 20 includes at least an evaporator 21, an expander 22, a first condenser 23, a second condenser 24, and a pump 25, and circulates a working medium Q through these. Various working media Q can be used. Here, R134a which is a low boiling point medium is used.

  The evaporator 21 is supplied with cooling water W of the engine 10 and the EGR cooler 11. The evaporator 21 evaporates the working medium Q using the heat of the cooling water W. Specifically, in the evaporator 21, high-temperature cooling water W after cooling the engine 10 and the EGR cooler 11 and before radiating heat from the radiator 12 is introduced, and the working medium Q is used with the cooling water W as a heat source. Is evaporated. The expander 22 is a turbine that expands the working medium evaporated in the evaporator 21. The expander 22 is connected to a generator (not shown) that generates power by rotating the expander 22.

  The sub-cooling water cooled by the sub-radiator 26 is circulated through the first condenser 23 so as to circulate. The first condenser 23 uses the sub cooling water to cool and condense the working medium Q used for power generation in the expander 3. The second condenser 24 is a cooling heat exchanger 32a of the thermoacoustic cooling device 30, and cools and condenses the working medium Q using a thermoacoustic phenomenon, as will be described later. The pump 6 compresses the condensed working medium Q and sends it to the evaporator 2.

  The thermoacoustic cooling device 30 includes an acoustic tube 31, and a cooling unit 32 and a heat input unit 33 provided on the acoustic tube 31. The thermoacoustic cooling device 30 performs cooling in the cooling unit 32 by inputting heat of exhaust gas of the engine 10 into the heat input unit 33 and generating sound waves in the acoustic tube 31.

  The acoustic tube 31 is configured by looping a circular tube. The tube length of the acoustic tube 31 is set to a predetermined length at which the propagating sound wave resonates, for example. The acoustic tube 31 is filled with a high-pressure gas as a working gas. Examples of the high pressure gas include helium gas and argon gas.

  The cooling unit 32 includes a cooling heat exchanger 32a, a first stack 32b, and a first room temperature heat exchanger 32c, which are arranged in this order along the propagation direction of sound waves. As described above, the cooling heat exchanger 32a functions as the second condenser 24, and the working medium Q condensed by the first condenser 23 is circulated. The cooling heat exchanger 32a is connected to the first room temperature heat exchanger 32c via the first stack 32b. The cooling heat exchanger 32a moves heat from the distributed working medium Q to one end side of the first stack 32b to cool and condense the working medium Q.

  The first stack 32b is a heat accumulator having a mesh laminated body in which a plurality of mesh structures are laminated, a honeycomb structured body, or a columnar body having a plurality of small through holes. The first stack 32b is made of, for example, ceramic or metal. The first normal temperature heat exchanger 32c moves the heat on the other end side of the first stack 32b to the external atmosphere, and dissipates the other end side of the first stack 32b so as to be maintained at a constant temperature. The first room temperature heat exchanger 32c is, for example, an air-cooled type.

  The heat input section 33 includes an exhaust gas heat exchanger (high temperature heat exchanger) 33a, a second stack 33b, and a second room temperature heat exchanger 33c, which are arranged in this order along the propagation direction of sound waves. Is arranged in. The exhaust gas of the engine 10 is circulated through the exhaust gas heat exchanger 33a. The exhaust gas heat exchanger 33a is connected to the second room temperature heat exchanger 33c via the second stack 33b. The exhaust gas heat exchanger 33a heats one end side of the second stack 33b by transferring heat from the circulated exhaust gas to one end side of the second stack 33b.

  The second stack 33b is a heat accumulator configured similarly to the first stack 32b. The second room temperature heat exchanger 33c moves the heat on the other end side of the second stack 33b to the external atmosphere and dissipates the other end side of the second stack 33b so as to be maintained at a constant temperature. The second room temperature heat exchanger 33c is, for example, an air-cooled type, similarly to the first room temperature heat exchanger 32c.

  In the thermoacoustic cooling device 30 configured as described above, the exhaust gas of the engine 10 flows through the exhaust gas heat exchanger 33a of the heat input section 33, and the heat of the exhaust gas is input to the exhaust gas heat exchanger 33a. One end side of the second stack 33b is heated. Thereby, since the other end side of the second stack 33b is radiated by the second room temperature heat exchanger 33c, a temperature difference is generated between one end side and the other end side of the second stack 33b. Due to the temperature difference, vibration of a predetermined wavelength resonates in the acoustic tube 31, and a sound wave (self-excited vibration) is generated.

  The sound wave propagating through the acoustic tube 31 is a sparse / dense wave, and adiabatically compresses from the sparse part to the dense part, while adiabatic expansion from the dense part to the sparse part. Therefore, when the sound wave passes through the first stack 32b, one end side of the first stack 32b as a low-pressure sparse part is cooled and the temperature is lowered, and the other end side of the first stack 32b as a high-pressure dense part is heated and becomes high temperature. As a result, a temperature gradient (temperature difference) is formed in the first stack 32b. Then, heat is radiated to the outside from the other end side of the heated first stack 32b through the first normal temperature heat exchanger 32c, and one end side of the first stack 32b is lowered to the outside air temperature or lower. Is done.

  Therefore, in the cooling heat exchanger 32a (second condenser 24) on the one end side of the first stack 32b, the heat of the working medium Q flowing is absorbed, and the heat of the working medium Q is externally absorbed by the thermoacoustic cooling device 30. As a result, the working medium Q is cooled to below the outside air temperature and condensed.

  Next, the operation of the waste heat recovery apparatus 100 of this embodiment will be described. The high-temperature working medium Q sent from the expander 22 is first cooled and condensed in the first condenser 23 by the sub cooling water cooled by the sub radiator 8. The working medium Q condensed in the first condenser 23 is further cooled and condensed in the second condenser 24, which is a cooling heat exchanger 32a, by cooling using the above-described thermoacoustic phenomenon in the thermoacoustic cooling device 30. The The working medium Q is sent to the evaporator 21 side by the pump 6, and then is heated and evaporated by the cooling water W from the engine 10 and the EGR cooler 11 in the evaporator 21, and is supplied to the expander 3. The

  As described above, in the waste heat recovery apparatus 100 of the present embodiment, the thermoacoustic cooling apparatus 30 can be combined for cooling the Rankine cycle system 20, and the cooling heat exchanger 32a of the thermoacoustic cooling apparatus 30 is replaced with the Rankine. It functions as the second condenser 24 of the cycle system 20. Thereby, the thermal energy (loss energy) of the exhaust gas of the engine 10 is converted into cooling energy by the thermoacoustic cooling device 30, and the working medium Q of the Rankine cycle system 20 can be cooled and condensed with this cooling energy.

  Therefore, in the Rankine cycle system 20, the working medium can be cooled to a temperature lower than the outside air temperature, and the condensing capacity (condenser capacity) can be increased. As a result, the energy can be efficiently regenerated and the waste heat recovery efficiency can be improved. For example, the power generation efficiency (theoretical efficiency) of the Rankine cycle system 20 can be improved by 10% or more.

  In the waste heat recovery apparatus 100, for example, when the second condenser 24, which is the cooling heat exchanger 32a of the thermoacoustic cooling apparatus 30, has a sufficient condenser capability, the second as shown below. The working medium Q may be cooled and condensed only by the condenser 24 (only by the thermoacoustic cooling device 30).

  FIG. 2 is a schematic configuration diagram showing a modification of the waste heat recovery apparatus of FIG. As shown in FIG. 2, the waste heat recovery apparatus 200 according to the modified example does not include the first condenser 23 with respect to the waste heat recovery apparatus 100 (see FIG. 1), and is a cooling heat exchanger 32 a. Only the condenser 24 is provided. In this case, the hot working medium Q sent from the expander 22 is cooled and condensed by cooling using the above-described thermoacoustic phenomenon in the second condenser 24, and then sent out to the evaporator 21 side by the pump 6. In the waste heat recovery apparatus 100 according to such a modification, the first condenser 23 can be unnecessary (omitted), and the apparatus can be downsized.

  The preferred embodiments of the present invention have been described above. However, the present invention is not limited to the above-described embodiments. The present invention can be modified without departing from the scope described in the claims or applied to other embodiments. May be.

  For example, in the above-described embodiment, the thermoacoustic cooling device 30 is a single-loop type in which the cooling unit 32 and the heat input unit 33 are connected by the acoustic tube 31 of one loop. The cooling section 32 and the heat input section 33 may be provided in separate loop acoustic tubes, and the two loop acoustic tubes may be connected). In addition, the Rankine cycle system 20 of the above embodiment may include a reserve tank that stores the condensed working medium Q, or may include other configurations.

  DESCRIPTION OF SYMBOLS 10 ... Engine, 11 ... EGR cooler, 20 ... Rankine cycle system, 30 ... Thermoacoustic cooling device, 31 ... Acoustic tube, 32a ... Cooling heat exchanger, 32b ... First stack, 32c ... First normal temperature heat exchanger, 33a ... exhaust gas heat exchanger (high temperature heat exchanger), 33b ... second stack, 33c ... second room temperature heat exchanger, 100 ... waste heat recovery device, Q ... working medium, W ... cooling water.

Claims (3)

A Rankine cycle system that uses the heat of the cooling water of the engine and the EGR cooler as a heat source;
A thermoacoustic cooling device that performs cooling with a cooling heat exchanger disposed in the first normal temperature heat exchanger via the first stack by generating sound waves in the acoustic tube using the heat of the exhaust gas of the engine as a heat source; With
The cooling heat exchanger is a waste heat recovery apparatus that cools and condenses the working medium of the Rankine cycle system.   The thermoacoustic cooling device inputs heat of the exhaust gas of the engine to a high temperature heat exchanger, and generates a temperature difference in a second stack disposed between the high temperature heat exchanger and a second room temperature heat exchanger. The waste heat recovery apparatus according to claim 1, wherein the sound wave is generated in the acoustic tube by applying.   The waste heat recovery apparatus according to claim 1 or 2, wherein the Rankine cycle system cools and condenses the working medium only by the cooling heat exchanger.

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