JP2017155612A - Waste heat recovery device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the flow of liquid-phase refrigerant into an expander while avoiding an internal combustion engine from being insufficiently cooled, in a waste heat recovery device using a Rankine cycle for recovering waste heat from the internal combustion engine.SOLUTION: The waste heat recovery device includes a boiler for vaporizing refrigerant, the expander for expanding gas-phase refrigerant to recover thermal energy, a condenser for condensing the gas-phase refrigerant passing through the expander to restore it into liquid-phase refrigerant, and a pump for returning the liquid-phase refrigerant delivered from the condenser into the boiler. The waste heat recovery device, where the outlet of the expander and the inlet of the condenser are connected via a first pipe, further includes a condensed water tank provided to be communicated through its position lower than the expander with the first pipe, a heater for heating the liquid-phase refrigerant flowing into the condensed water tank, and a second pipe for delivering the gas-phase refrigerant vaporized in the heater into the condenser or the first pipe.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a waste heat recovery apparatus, and more particularly to a waste heat recovery apparatus that recovers waste heat of an internal combustion engine using a Rankine cycle system.

  Patent Document 1 discloses a technique related to a Rankine cycle system that recovers waste heat accompanying the operation of an internal combustion engine. In this Rankine cycle system, an internal combustion engine that generates steam by evaporating the working fluid, a turbine that recovers the thermal energy of the generated steam as power, a condenser that condenses the steam that has passed through the turbine, and an operation that is liquefied by the condenser A tank for storing fluid and a recirculation unit for recirculating the liquid-phase working fluid in the tank to the internal combustion engine are provided. In this Rankine cycle system, the lowermost part of the passage connecting the turbine outlet and the condenser inlet is connected to the tank via the passage, and the reflux part is placed in the middle of the passage. A heat exchanger for exchanging heat with the circulating working fluid is provided.

Japanese Patent Laying-Open No. 2015-108339

  According to the system of Patent Document 1, since the liquid-phase working fluid generated at the turbine outlet can be guided into the tank, the inflow of the liquid-phase working fluid into the turbine is avoided. However, in the system of Patent Document 1, the liquid-phase working fluid stored in the tank is heated by the heat exchanger and then returned to the internal combustion engine. In this case, the temperature of the working fluid recirculated to the internal combustion engine may increase excessively, and the internal combustion engine may not be sufficiently cooled.

  The present invention has been made in view of the above-described problems. In a waste heat recovery apparatus that recovers waste heat of an internal combustion engine by a Rankine cycle, the expander avoids insufficient cooling of the internal combustion engine. An object of the present invention is to provide a waste heat recovery device capable of suppressing the inflow of a liquid-phase refrigerant into the water.

  The present invention expands a vaporizer that evaporates refrigerant, a superheater that superheats the gas-phase refrigerant delivered from the boiler by heat exchange with the exhaust of the internal combustion engine, and the gas-phase refrigerant that has passed through the superheater. An expander that recovers thermal energy, a condenser that condenses the gas-phase refrigerant that has passed through the expander and returns it to the liquid-phase refrigerant, and the liquid-phase refrigerant sent from the condenser to the boiling device And a return heat pump. The waste heat recovery apparatus includes a first pipe, a second pipe, a condensed water tank, and a heating device. The first pipe is configured as a refrigerant pipe that connects the outlet portion of the expander and the inlet portion of the condenser. The condensed water tank is provided so as to communicate with the first pipe from a position lower than the expander, and is configured such that liquid-phase refrigerant generated in the expander or the first pipe flows in. The heating device is configured to heat the liquid-phase refrigerant that has flowed into the condensed water tank. And the gaseous-phase refrigerant | coolant vaporized in the heating apparatus is sent to a condenser or 1st piping via 2nd piping.

  According to the present invention, the liquid-phase refrigerant generated in the expander or the first pipe is guided to the condensed water tank by gravity. Thereby, it is possible to avoid the liquid-phase refrigerant from flowing into the expander. Further, according to the configuration of the present invention, the refrigerant heated in the heating device is returned to the internal combustion engine after being cooled by the condenser. For this reason, it becomes possible to suppress the inflow of the liquid phase refrigerant to the expander while avoiding insufficient cooling of the internal combustion engine.

It is a figure which shows the characteristic structure of the Rankine cycle system of Embodiment 1. FIG. It is a figure which shows the structure of the comparative example of Rankine cycle system of Embodiment 1. FIG.

  Embodiments of the present invention will be described below with reference to the drawings. However, the same reference numerals are given to common elements in the drawings, and redundant description is omitted. In addition, in the embodiment shown below, when referring to the number of each element, quantity, quantity, range, etc., unless otherwise specified or clearly specified in principle, the reference However, the present invention is not limited to these numbers. Further, the structures described in the embodiments described below are not necessarily essential to the present invention unless otherwise specified or clearly specified in principle.

Embodiment 1 FIG.
1. Basic Configuration of Rankine Cycle System FIG. 1 is a diagram illustrating a characteristic configuration of a Rankine cycle system 100 according to the first embodiment. FIG. 2 is a diagram illustrating a configuration of a Rankine cycle system 200 as a comparative example of the Rankine cycle system 100 according to the first embodiment. Since the basic system configuration of Rankine cycle system 200 is the same as Rankine cycle system 100 of the first embodiment, the basic configuration and basic operation of Rankine cycle system 100 are the same as Rankine cycle system 200 of FIG. The description will be given with reference.

  As shown in FIG. 2, the Rankine cycle system 200 of the comparative example includes an internal combustion engine (engine) 10 and is configured as a waste heat recovery device that recovers waste heat of the engine 10. There is no limitation on the type and structure of the engine 10. However, the refrigerant block 12 through which the refrigerant circulating in the engine 10 flows is formed in the cylinder block and the cylinder head of the engine 10. The refrigerant flow path 12 includes a water jacket surrounding the cylinder. The engine 10 is cooled by heat exchange with the refrigerant flowing through the refrigerant flow path 12. In the present embodiment, water is used as the refrigerant.

  The engine 10 is cooled by boiling the refrigerant flowing through the refrigerant flow path 12 with the waste heat of the engine 10 and evaporating a part thereof. That is, the refrigerant flow path 12 functions as a boiling device that boiles the liquid-phase refrigerant flowing through the inside by the heat of the engine 10. The configuration of the coolant channel 12 is not particularly limited as long as the coolant channel 12 is a passage that can flow through the engine 10. Moreover, the refrigerant | coolant distribute | circulated to a refrigerant | coolant flow path should just be a liquid phase fluid at normal temperature, should just be boiled with the heat | fever of the engine 10 and change to a gaseous phase fluid, and is not limited to water.

  The refrigerant flow path 12 of the engine 10 is connected to a gas-liquid separator 16 via a refrigerant pipe 14. When the refrigerant is boiled by the heat of the engine 10, the liquid phase refrigerant is discharged from the refrigerant flow path 12 together with the gas phase refrigerant. The gas-liquid separator 16 separates the gas-liquid two-phase refrigerant flowing into the gas-liquid separator 16 into a liquid-phase refrigerant and a gas-phase refrigerant (vapor). The gas-liquid separator 16 is connected to the second water pump 20 (WP2) via the refrigerant pipe 18. The liquid-phase refrigerant separated by the gas-liquid separator 16 flows into the second water pump 20 via the refrigerant pipe 18 and is sent to the refrigerant flow path 12 by the second water pump 20.

  The Rankine cycle system 200 includes an exhaust heat steam generator 13. The exhaust heat steam generator 13 is provided in the exhaust passage 22 of the engine 10. The lower part of the gas-liquid separator 16 is also connected to the exhaust heat steam generator 13 via the refrigerant pipe 18 and the refrigerant pipe 11. A liquid phase refrigerant is introduced into the exhaust heat steam generator 13 from the gas-liquid separator 16. The introduced liquid-phase refrigerant is superheated by heat exchange with the exhaust gas flowing through the exhaust passage 22 and boiled, and a part thereof becomes steam. The vapor-phase refrigerant that has become vapor is reintroduced into the gas-liquid separator 16 through the refrigerant pipe 15.

  The gas-liquid separator 16 is connected to the superheater 30 via the refrigerant pipe 28. The superheater 30 is provided upstream of the exhaust heat steam generator 13 in the exhaust passage 22 of the engine 10. In the gas-liquid separator 16, the gas-phase refrigerant and the liquid-phase refrigerant coexist, so the gas-phase refrigerant is saturated vapor. The gas-phase refrigerant that has entered the superheater 30 becomes superheated steam by heat exchange with the exhaust gas flowing through the exhaust passage 22.

  The superheater 30 is connected to a turbine 34 that is an expander via a refrigerant pipe 32. The turbine 34 recovers thermal energy by expanding the gas-phase refrigerant (superheated steam) sent from the superheater 30. A supersonic nozzle 35 is provided at a connection portion between the refrigerant pipe 32 and the turbine 34. The gas-phase refrigerant is sprayed from the supersonic nozzle 35 to the turbine 34 to rotate the turbine 34. The rotation of the turbine 34 is transmitted to the rotation shaft of the engine 10 via the clutch 33. That is, the thermal energy recovered by the turbine 34 is used for assisting the engine 10. However, it is also possible to drive the generator by the turbine 34 and store the generated electricity in the storage battery.

  The Rankine cycle system 100 includes a refrigerant pipe 37 that connects the upper end of the gas-liquid separator 16 and the refrigerant pipe 36. The refrigerant pipe 37 is provided with a relief valve 38. When the relief valve 38 is opened, the gas-phase refrigerant in the gas-liquid separator 16 is introduced into the relief valve 38. The introduced gas phase refrigerant is decompressed when passing through the relief valve 38 and then introduced into the condenser (condenser) 40.

  The outlet portion of the turbine 34 and the inlet portion of the condenser 40 are connected by a refrigerant pipe 36 (first pipe). The gas-phase refrigerant expanded by the turbine 34 is sent to the condenser 40 via the refrigerant pipe 36. The gas-phase refrigerant sent to the condenser 40 is cooled and condensed by the condenser 40 and returned to the liquid-phase refrigerant. The liquid-phase refrigerant generated by the condensation of the gas-phase refrigerant is sent from the condenser 40 to the catch tank 44 through the refrigerant pipe 42 and temporarily stored in the catch tank 44. The catch tank 44 is connected to the middle of the refrigerant pipe 18 via the refrigerant pipe 46. The refrigerant pipe 46 is provided with a first water pump 48 (WP1). The first water pump 48 is a pump for sending the liquid-phase refrigerant stored in the catch tank 44 to the gas-liquid separator 16 or the engine 10 via the refrigerant pipe 18. A check valve 47 is provided between the first water pump 48 and the refrigerant pipe 18 in the refrigerant pipe 46 to prevent the backflow of the liquid-phase refrigerant from the refrigerant pipe 18 side to the catch tank 44 side. The catch tank 44 and the turbine 34 are connected by a refrigerant pipe 50. The refrigerant pipe 50 is for discharging the liquid phase refrigerant accumulated at the outlet of the turbine 34 to the catch tank 44.

2. Next, the basic operation of boiling cooling performed in the Rankine cycle system 200 will be described. In FIG. 2, the flow of the liquid-phase refrigerant is represented by a thick solid line, and the gas-phase refrigerant (vapor) is represented by a thick broken line.

  In the Rankine cycle system 200, energy from waste heat of the engine 10 is recovered as rotational energy of the turbine 34 to assist rotation of the rotating shaft of the engine 10. That is, the refrigerant flow path 12 and the exhaust heat steam generator 13 function as a boiling device that receives the waste heat of the engine 10 and boiles the liquid-phase refrigerant. When the liquid-phase refrigerant boils, a part of the liquid-phase refrigerant changes to a gas-phase refrigerant (vapor). The gas-phase refrigerant generated in the refrigerant flow path 12 is introduced into the gas-liquid separator 16 via the refrigerant pipe 14. The gas-phase refrigerant generated in the exhaust heat steam generator 13 is introduced into the gas-liquid separator 16 via the refrigerant pipe 15. The gas-phase refrigerant in the gas-liquid separator 16 is introduced into the superheater 30 via the refrigerant pipe 14. The gas-phase refrigerant changes into higher-temperature and higher-pressure superheated steam by further receiving exhaust heat of the engine 10 in the process of passing through the superheater 30. The superheated steam that has passed through the superheater 30 is introduced into the turbine 34 via the refrigerant pipe 32.

  In the turbine 34, the introduced superheated steam is decompressed by the supersonic nozzle 35 and expanded, and then sprayed onto the turbine blade. Thereby, the thermal energy of the superheated steam is taken out as the rotational motion of the turbine 34. The low-pressure gas-phase refrigerant that has passed through the turbine 34 is introduced into the condenser 40 via the refrigerant pipe 36. The introduced gas-phase refrigerant is cooled in the condenser 40 to be changed into a liquid-phase refrigerant, and is temporarily stored in the catch tank 44 via the refrigerant pipe 42. When the first water pump 48 is driven, the liquid-phase refrigerant in the catch tank 44 is introduced into the gas-liquid separator 16 or the engine 10 through the refrigerant pipe 46 and the refrigerant pipe 18.

3. Problems of Rankine Cycle System of Comparative Example Since the steam temperature is reduced at the outlet of the turbine 34, liquid phase refrigerant (condensed water) may be generated by condensation. When the generated condensed water flows back into the turbine 34, the internal components are adversely affected. Therefore, it is desirable that the generated condensed water is quickly discharged. In the Rankine cycle system 200 of the comparative example described above, the condensed water generated at the outlet of the turbine 34 is introduced into the catch tank 44 through the refrigerant pipe 50, so that the turbine 34 can be protected from the inflow of condensed water. it can.

  Here, as shown in FIG. 2, when the Rankine cycle is operated by the Rankine cycle system 200, the normal pressure region where the refrigerant is overheated (the region of −40 to 100 kPa_G), and the low pressure region where the refrigerant is condensed. (Region of −90 to −70 kPa_G) is formed. In the low pressure region, the boiling point of the refrigerant also decreases as the pressure decreases. For this reason, in the Rankine cycle system 200 of the comparative example in which relatively high-temperature condensed water is introduced into the catch tank 44, there is a risk that the refrigerant will boil due to the reduced pressure in the vicinity of the refrigerant suction port of the first water pump 48. In this case, the gas phase is caught in the first water pump 48, and the water supply performance is deteriorated.

  In this regard, for example, in the technique disclosed in Patent Document 1 described above, in order to suppress decompression boiling of the refrigerant, the liquid-phase working fluid staying at the turbine outlet is cooled by a heat exchanger and then introduced into the tank. . However, the liquid-phase working fluid stored in the tank is heated by the heat exchanger and then returned to the internal combustion engine. For this reason, in the technique of Patent Document 1, there is a possibility that the temperature of the working fluid recirculated to the internal combustion engine excessively increases and the internal combustion engine cannot be sufficiently cooled.

4). Characteristic Configuration of Rankine Cycle System of Embodiment 1 Next, a characteristic configuration of Rankine cycle system 100 of Embodiment 1 will be described with reference to FIG. Although only the characteristic configuration of the Rankine cycle system 100 is illustrated in FIG. 1, the Rankine cycle system 100 is assumed to have the configuration of the Rankine cycle system 200 excluding the refrigerant pipe 50.

  As shown in FIG. 1, a condensed water tank 52 is provided in the refrigerant pipe 36 near the outlet of the turbine 34. The condensed water tank 52 is disposed at a position lower than the turbine 34 and communicates with the lowest part of the refrigerant pipe 36. A heating device 56 is connected to a position lower than the condensed water tank 52 via a refrigerant pipe 54. The heating device 56 is a device for heating the condensed water by heat exchange with an exhaust passage (not shown). The upper part of the heating device 56 is connected to the refrigerant pipe 36 in the vicinity of the inlet of the condenser 40 via a refrigerant pipe 58 (second pipe).

  According to the configuration of the Rankine cycle system 100 shown in FIG. 1, the condensed water generated in the refrigerant pipe 36 flows into the condensed water tank 52 by the action of gravity, and further flows from the condensed water tank 52 to the heating device 56 below. And flows in. Thereby, it is possible to avoid the condensed water generated in the refrigerant pipe 36 from flowing into the turbine 34.

  The condensed water flowing into the heating device 56 is heated by heat exchange with the exhaust. The refrigerant that has been heated and becomes vapor again flows through the refrigerant pipe 58 and the refrigerant pipe 36 and is introduced into the condenser 40. As described above, according to the configuration of the Rankine cycle system 100, the refrigerant (vapor) heated by the heating device 56 is returned to the engine 10 after being cooled by the condenser 40. As a result, it is possible to prevent the high-temperature refrigerant from being returned to the engine 10, thereby suppressing the inflow of the liquid-phase refrigerant into the turbine 34 while avoiding insufficient cooling of the engine 10. Is possible.

  By the way, in Rankine cycle system 100 of Embodiment 1 mentioned above, although heating device 56 using exhaust heat was explained, other heat sources, such as a heating wire, may be used. In addition, since the inside of the heating apparatus 56 is a low pressure area | region, condensed water boils at about 45-70 degreeC. Further, since the steam introduced into the turbine 34 is basically sufficiently heated so that condensed water is not generated, the amount of condensed water introduced into the condensed water tank 52 is relatively small. For this reason, the energy required for heating the condensed water in the heating device 56 is much smaller than the exhaust energy, and the heating device 56 can cope with even a small one. In addition, in the heating device 56 using exhaust heat, it is preferable to ground the exhaust passage downstream of the catalyst so as not to affect the warm-up of the catalyst.

  Further, in the Rankine cycle system 100 of the first embodiment described above, the heating device 56 and the refrigerant tube 36 are connected via the refrigerant tube 58, but the heating device 56 and the condenser 40 are connected via the refrigerant tube 58. The structure which connects with an inlet_port | entrance part directly may be sufficient.

10 Internal combustion engine
12 Refrigerant flow path (boiler)
13 Exhaust heat steam generator (boiler)
11, 14, 15, 18, 28, 32, 37, 42, 50, 54 Refrigerant pipe 16 Gas-liquid separator 20 Second water pump 22 Exhaust passage 30 Superheater 33 Clutch 34 Turbine (expander)
35 Supersonic nozzle 36 Refrigerant pipe (first pipe)
38 Relief valve 40 Condenser
44 Catch tank 46 Refrigerant pipe (refrigerant path)
47 Check valve 48 First water pump (pump)
52 Condensed water tank 56 Heating device 58 Refrigerant pipe (second pipe)
100,200 Rankine cycle system

Claims (1)

A boiler that vaporizes the refrigerant, a superheater that superheats the gas-phase refrigerant delivered from the boiler by heat exchange with the exhaust of the internal combustion engine, and the gas-phase refrigerant that has passed through the superheater is expanded. An expander that recovers thermal energy, a condenser that condenses the vapor-phase refrigerant that has passed through the expander and returns it to a liquid-phase refrigerant, and a liquid-phase refrigerant that is sent from the condenser to the boiling device A waste heat recovery device comprising a return pump,
The outlet portion of the expander and the inlet portion of the condenser are connected by a first pipe,
A condensed water tank provided to communicate with the first pipe from a position lower than the expander, and into which a liquid-phase refrigerant generated in the expander or the first pipe flows;
A heating device for heating the liquid-phase refrigerant flowing into the condensed water tank;
A second pipe for sending the vapor-phase refrigerant vaporized in the heating device to the condenser or the first pipe;
A waste heat recovery device comprising:

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