JP2009133210A - Waste heat recovery device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve exhaust heat recovery efficiency by recovering exhaust heat of an engine which cannot be recovered by a Rankine cycle and is discharged. <P>SOLUTION: This exhaust heat recovery device 1 forms the Rankine cycle to carry out motive power regeneration of a compressor 6 and electric power regeneration of a generator 7 by driving a turbine 5 by steam to which the exhaust heat is given in the engine 3 and a superheater 9, converts the exhaust heat that cannot be recovered by the Rankine cycle to electric energy by heat-electricity converting elements 15a to 15e installed in the engine 3, the superheater 9, a catalyst device 11, a condenser 12 and an air conditioner 14, and recovers the electric energy in a battery device 8. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a waste heat recovery apparatus that recovers waste heat in an engine via steam.

  2. Description of the Related Art Conventionally, there is known a waste heat recovery device that recovers waste heat generated by driving an internal combustion engine (engine) using a Rankine cycle. In such a waste heat recovery device, for example, the water cooling cooling system of the engine has a sealed structure, and the refrigerant evaporated by the waste heat in the engine, that is, the expander (turbine) is driven by the steam, and the thermal energy of the steam Is recovered by converting it into electrical energy. An example of such a waste heat recovery apparatus is disclosed in Patent Document 1, for example.

JP 2000-345835 A

  Such a waste heat recovery device includes an engine main body that vaporizes the refrigerant by waste heat generated from the engine, a superheater that superheats the steam by exchanging heat between the exhaust gas and the refrigerant, and heat energy of the steam. An expander that converts electric energy or power into power and a condenser that returns the refrigerant in the vapor state to the refrigerant in the liquid phase again form a Rankine cycle. These engine main body and superheater receive waste heat from the engine and exhaust gas and have waste heat. Such an engine main body and a superheater are examples of a waste heat holding part. The heat which such a waste heat holding part has can be provided to a refrigerant | coolant. Thereby, a refrigerant | coolant is vaporized and waste heat can be collect | recovered.

  By the way, such a waste heat holding part may still have waste heat even after giving heat to the refrigerant. That is, there may be thermal energy that cannot be recovered from the refrigerant in the waste heat holding unit. In addition, the energy of the steam recovered by the expander is a part of the thermal energy of the steam, and the remaining heat energy that cannot be recovered by the expander is released to the atmosphere by the condenser. As described above, the waste heat recovery by the Rankine cycle cannot recover the exhaust heat of the engine, so there is room for improvement in the waste heat recovery device.

  Therefore, an object of the present invention is to improve the waste heat recovery efficiency by recovering the waste heat of the engine that has been released and cannot be recovered by the Rankine cycle.

  The waste heat recovery apparatus of the present invention that solves such a problem includes a thermoelectric conversion element attached to a waste heat holding unit included in the Rankine cycle, and a power storage device that stores electric energy converted by the thermoelectric conversion element. (Claim 1). By adopting such a configuration, it is possible to recover the thermal energy that has not been recovered by the Rankine cycle and has been released to the atmosphere. Thereby, the waste heat recovery apparatus can improve waste heat recovery efficiency. This waste heat holding unit is used to generate excess heat from waste heat, such as an engine body that generates heat, a superheater that exchanges heat between exhaust gas and steam, and a condenser that dissipates heat to return to the liquid phase. It is a part that may have heat.

  Further, such a waste heat recovery apparatus includes a temperature measurement unit that measures the temperature of the waste heat holding unit, and an electrical connection between the thermoelectric conversion element and the power storage device based on temperature information acquired by the temperature measurement unit. And a control means for switching between normal connection and disconnection (claim 2). By setting it as such a structure, according to the temperature of a waste-heat holding part, implementation and a stop of the waste-heat recovery by a thermoelectric conversion element are controllable. For example, when the temperature of the waste heat holding unit is high, the waste heat can be recovered, and when the temperature of the waste heat holding unit is low, the recovery of the waste heat can be stopped.

  By mounting the thermoelectric conversion element in the waste heat holding part of the Rankine cycle, the present invention can recover the waste heat of the engine that has been released without being recovered by the Rankine cycle, and can improve the waste heat recovery efficiency. .

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing a schematic configuration of the waste heat recovery apparatus 1 of the present embodiment.

  In the waste heat recovery apparatus 1, a refrigerant passage 2 through which a refrigerant in a vapor state and a refrigerant in a liquid phase flow is formed in a loop shape. The refrigerant in the vapor state and the refrigerant in the liquid phase circulate in the refrigerant passage 2. The refrigerant passage 2 is formed in the engine 3 and includes a water jacket through which the refrigerant flows. The refrigerant is vaporized when heated by the combustion heat of the engine 3. The refrigerant passage 2 is provided with an expander driven by the refrigerant vapor, that is, a turbine 5. This turbine 5 is connected to a compressor 6. The compressor 6 is driven by the turbine 5 and sends compressed air to an intake port (not shown) of the engine 3. The turbine 5 is further connected to a generator 7. The generator 7 is driven by the turbine 5 to convert the heat energy of the steam into electric energy and collect it in the power storage device 8. Further, the waste heat recovery apparatus 1 includes a superheater 9 between the engine 3 and the turbine 5 on the refrigerant passage 2. The superheater 9 recovers heat from the exhaust gas flowing in the exhaust passage 10 and further adds heat to the steam supplied to the turbine 5, and improves the recovery efficiency of waste heat. In this way, the turbine 5 is driven by the steam that has become high temperature and high pressure by the superheater 9. The exhaust passage 10 is provided with a catalyst device 11 for purifying exhaust gas. The refrigerant passage 2 is provided with a condenser 12 on the downstream side of the turbine 5 for returning the refrigerant, which has become vapor, to liquid again. The refrigerant returned to the liquid by the condenser 12 is again supplied to the water jacket in the engine 3 by the pump (W / P) 13. In this embodiment, the refrigerant is vaporized by the combustion heat. Here, it can also be set as the structure which vaporizes a refrigerant | coolant by spraying a refrigerant | coolant on a cooling site | part. In short, what is necessary is just to be the structure which can implement | achieve what is called Rankine cycle. The waste heat recovery apparatus 1 includes an air conditioner 14. A liquid phase refrigerant moves between the air conditioner 14 and the engine 3 to exchange heat. Thus, the waste heat recovery apparatus 1 constitutes a Rankine cycle, and recovers the waste heat of the engine 3 through steam.

  Such a waste heat recovery apparatus 1 further includes thermoelectric conversion elements 15a to 15e. The thermoelectric conversion elements 15a to 15e are attached to the engine 3, the superheater 9, the catalyst device 11, the condenser 12, and the air conditioner 14 corresponding to the waste heat holding unit of the present invention. That is, the thermoelectric conversion element 15 a is attached to the engine 3, and the thermoelectric conversion element 15 b is attached to the superheater 9. Similarly, the thermoelectric conversion element 15 c is attached to the catalyst device 11, the thermoelectric conversion element 15 d is attached to the condenser 12, and the thermoelectric conversion element 15 e is attached to the air conditioner 14. Such a waste heat holding part is a part that has excessive waste heat even after applying heat to the refrigerant, or other part that receives heat from the refrigerant and has excessive heat. But you can.

  Next, a schematic configuration of such a thermoelectric conversion element 15a will be described. FIG. 2 is an explanatory diagram showing a schematic configuration of the thermoelectric conversion element 15a. The thermoelectric conversion element 15a is a power generation device using the Seebeck effect, and a plurality of n-type semiconductors 151 and p-type semiconductors 152 are alternately arranged. The one end 151 a of the n-type semiconductor 151 and the end 152 a of one p-type semiconductor 152 adjacent to the n-type semiconductor 151 are coupled by the first coupling electrode 153. Further, the second coupling electrode 154 couples the other end 151 b of the n-type semiconductor 151 and the end 152 b of another p-type semiconductor 152 adjacent to the n-type semiconductor 151. A hot junction substrate 155 is bonded to the outside of the first coupling electrode 153. In addition, a cold junction substrate 156 is bonded to the outside of the second coupling electrode 154. In such a thermoelectric conversion element 15 a, when a temperature difference occurs between the first coupling electrode 153 and the second coupling electrode 154, a potential difference is generated between the first coupling electrode 153 and the second coupling electrode 154. Furthermore, a large potential difference is obtained by combining a plurality of n-type semiconductors 151 and p-type semiconductors 152 in this way. Thus, the thermoelectric conversion element 15a converts thermal energy into electrical energy. Further, each of the thermoelectric conversion elements 15b to 15e has the same configuration as the thermoelectric conversion element 15a.

  Such thermoelectric conversion elements 15a to 15e are mounted so that the hot junction substrate 155 side contacts each part of the engine 3, the superheater 9, the catalyst device 11, the condenser 12, and the air conditioner 14. Further, the thermoelectric conversion element 15 a and the power storage device 8 form a circuit 19 a. Further, the thermoelectric conversion element 15 b forms a circuit 19 b together with the power storage device 8. Similarly, a circuit 19c, a circuit 19d, and a circuit 19e are respectively formed. In these circuits 19a to 19e, when each waste heat holding part becomes higher than the ambient temperature, a temperature difference is generated between the first coupling electrode 153 and the second coupling electrode 154 of the thermoelectric conversion elements 15a to 15e, Current flows. When the current flows in this way, the power is stored in the power storage device 8.

  Further, switches 16a and 16b for switching between ON and OFF are incorporated in the circuit 19a and the circuit 19b, respectively. When the switch 16a is turned on, a circuit is formed and a current is generated. On the other hand, when the switch 16a is OFF, the circuit is disconnected. In this way, the switch 16a is turned on, and current flows through the circuit. The switch 16b switches the circuit in the same manner as the switch 16a.

  Further, temperature sensors 17a and 17b corresponding to the temperature measuring means of the present invention are respectively attached to the part where the thermoelectric conversion element 15a is attached and the part where the thermoelectric conversion element 15b is attached. The switch 16a and the temperature sensor 17a are electrically connected to an ECU (Electronic Control Unit) 18 corresponding to the control means of the present invention. The switch 16b and the temperature sensor 17b are also electrically connected to the ECU 18. ECU18 acquires the temperature information of each measurement part from temperature sensor 17a, 17b, and switches ON / OFF of switch 16a, 16b based on the acquired temperature information.

  Next, control performed by the ECU 18 will be described. The ECU 18 performs control for each waste heat holding unit equipped with the thermoelectric conversion element 15. FIG. 3 is a flowchart illustrating an example of control performed by the ECU 18 based on the temperature information of the temperature measurement unit acquired by the temperature sensor 17 attached to one of the waste heat holding units. The ECU 18 starts control when the engine 3 is started.

  The ECU 18 acquires information about the temperature T from the temperature sensor 17 in step S1. The ECU 18 proceeds to step S2 after completing the process of step S1.

ECU18 in step S2, compares the temperature T and the reference temperature _{T 0} obtained in step S1, the temperature T is to determine the high-temperature or not than the reference temperature _{T 0.} Here, the reference temperature T ₀ is a temperature that becomes a threshold value determined to have excess heat. This reference temperature T ₀ varies depending on the part where the temperature sensor 17 is mounted. For example, if the temperature sensor 17b mounted on the superheater 9, reference temperature _{T 0} which ECU18 determines is higher than the temperature _{T 1.} Here, the temperature T1 is the temperature of the superheater when the turbine 5 is driven and steam that can regenerate power is generated in the generator 7. At this time, even if the superheater 9 applies heat to the refrigerant, the superheater 9 is in a state of retaining excess heat. ECU18 If determines YES in step S2, namely, if the temperature T is higher than the reference temperature _{T 0,} the process proceeds to step S3.

When the temperature T is higher than the reference temperature T ₀ , the waste heat holding unit has excess heat. Therefore, the ECU 18 turns on the switch 16 in step S3. Thereby, a circuit including the thermoelectric conversion element 15 and the power storage device 8 is formed. When the circuit is formed, electric energy is converted from heat energy by the thermoelectric conversion element 15 in the waste heat holding section. The converted electrical energy is stored in the power storage device 8. The ECU 18 returns after completing the process of step S3.

Meanwhile, ECU 18 when it is determined that NO in the step S2, i.e., if the temperature T is not higher than the room temperature _{T 0,} the process proceeds to step S4.

If ECU18 reaches step S4, i.e., when the temperature T is equal to or lower than the reference temperature, T _0, the waste heat held unit has no excess heat. In step S4, the ECU 18 turns off the switch 16. Thereby, the circuit including thermoelectric conversion element 15 and power storage device 8 is disconnected. When the circuit is thus disconnected, the recovery of waste heat by the thermoelectric conversion element 15 is stopped. As a result, the waste heat recovery device 1 promotes the temperature of the waste heat holding unit from rising due to the waste heat of the engine 3. The ECU 18 returns after completing the process of step S4. In the above description of the control flow, the switch 16 is replaced with the switch 16a and the temperature sensor 17 is replaced with 17a when the circuit 19a is controlled. In the case of control of the circuit 19b, the switch 16 is read as the switch 16b, and the temperature sensor 17 is read as 17b.

  The above control is performed independently in each of the circuit 19a and the circuit 19b. Thereby, according to the temperature state of each waste heat holding part, waste heat can be collect | recovered. Thus, the waste heat recovery apparatus 1 of the present invention recovers the waste heat of the engine 3 by the Rankine cycle and recovers the remaining waste heat that cannot be recovered by the Rankine cycle using the thermoelectric conversion element 15. . Thereby, the waste heat recovery efficiency of the waste heat recovery apparatus 1 is improved.

  The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited thereto. Various modifications of these embodiments are within the scope of the present invention. It is apparent from the above description that various other embodiments are possible within the scope.

It is explanatory drawing which showed schematic structure of the waste heat recovery apparatus. It is explanatory drawing which showed schematic structure of the thermoelectric conversion element. It is explanatory drawing which showed an example of the control flow of ECU.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Waste heat recovery device 2 Refrigerant passage 3 Engine 5 Turbine 6 Compressor 7 Generator 8 Power storage device 9 Superheater 11 Catalytic device 12 Condenser 14 Air conditioner 15a thru 15e Thermoelectric conversion element 16a, 16b Switch 17a, 17b Temperature sensor 18 ECU
151 n-type semiconductor 152 p-type semiconductor 153 first coupling electrode 154 second coupling electrode 155 hot junction substrate 156 cold junction substrate

Claims (2)

A thermoelectric conversion element attached to the waste heat holding part included in the Rankine cycle;
A power storage device that stores electrical energy converted by the thermoelectric conversion element;
A waste heat recovery device comprising: The waste heat recovery apparatus according to claim 1,
Temperature measuring means for measuring the temperature of the waste heat holding unit;
Control means for switching between electrical connection and disconnection between the thermoelectric conversion element and the power storage device based on temperature information acquired by the temperature measurement means;
A waste heat recovery device comprising:

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