JP2013068137A - Waste heat utilization device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste heat utilization device improved in output of an internal combustion engine and having high durability, while improving an energy recovery amount in a rankine cycle.SOLUTION: A waste heat utilization device includes: an engine 5; a turbocharger 7 supplying a compressed air to the engine 5; a driving system 1 having pipes 15, 16 as an exhaust return passage; and a rankine cycle 3 for use in the same. The rankine cycle 3 is provided with a first boiler 27, a second boiler 28, and a third boiler 29. The rankine cycle 3 is further provided with a bypass passage 41 for causing a hydraulic fluid to bypass the second boiler 28 and a three-way valve 43. In this waste heat utilization device, the hydraulic fluid may be sufficiently heated by the first to third boilers 27-29, and the temperature of the hydraulic fluid flowing into the third boiler 29 may be lowered by causing the hydraulic fluid to flow into the bypass passage 41.

Description

  The present invention relates to a waste heat utilization apparatus.

  FIG. 2 of Patent Document 1 discloses a conventional waste heat utilization apparatus. This waste heat utilization device is used in a drive system, and includes a Rankine cycle that has first and second boilers and circulates a working fluid. The drive system includes an engine and a turbocharger that supplies pressurized air to the engine. The first boiler in the Rankine cycle heats the working fluid by exchanging heat between the pressurized air and the working fluid. The second boiler heats the working fluid by exchanging heat between the engine coolant and the working fluid. The second boiler is located downstream of the first boiler in the circulating direction of the working fluid. An expander is provided downstream of the second boiler.

  In such a waste heat utilization apparatus, since the working fluid can be heated by the first and second boilers, the temperature of the working fluid flowing into the expander can be increased. Moreover, in this waste heat utilization apparatus, since it becomes possible to cool pressurized air and cooling water by the heat exchange in a 1st, 2nd boiler, it is also possible to improve the output of an engine.

JP 2008-8224 A

  By the way, in order to increase the amount of energy that can be recovered in the Rankine cycle, the working fluid expanded and depressurized in the expander needs to be suitably vaporized. This is also required from the viewpoint of protecting the expander and improving the durability of the waste heat utilization device. If the expansion of the working fluid in the expander is incomplete, not only will the amount of energy that can be recovered be reduced, but there may also be a liquid back phenomenon in which the liquid working fluid flows out of the expander, which may damage the expander. This is because it occurs.

  Therefore, in order to suitably expand the working fluid in the expander, it is preferable to sufficiently heat the working fluid that flows into the expander to a superheated steam temperature (superheat) that exceeds the temperature that becomes saturated steam.

  However, in the conventional waste heat utilization device, although the working fluid can be heated by the first and second boilers, the temperature of the working fluid flowing into the expander is the amount of heat radiated in the second boiler, that is, the engine It depends on the temperature of the cooling water of the internal combustion engine. In particular, when the temperature of the cooling water is low, the working fluid heated by the first boiler radiates heat to the cooling water in the second boiler, so that the temperature of the working fluid flowing into the expander There may also be a situation in which the value of A decreases. For these reasons, in the above-described waste heat utilization apparatus, it is difficult to heat the working fluid to the superheat state, the amount of energy that can be recovered in the Rankine cycle becomes insufficient, and there is a concern that its durability may be lowered. Note that if the evaporation pressure in the first boiler and the second boiler is lowered, superheat can be secured even with a relatively low temperature heat source, but in this case, the recovered energy is reduced.

  The present invention has been made in view of the above-described conventional situation, and realizes an improvement in output of an internal combustion engine while improving an energy recovery amount in a Rankine cycle, and has high durability, and a waste heat utilization device having high durability. Providing is an issue to be solved.

The waste heat utilization apparatus of the present invention recirculates to the internal combustion engine, a supercharger that supplies pressurized air to the internal combustion engine, and a part of the exhaust gas generated by the internal combustion engine as recirculated exhaust gas. A waste heat utilization device having a Rankine cycle that is used in a drive system having an exhaust gas recirculation path and circulates a working fluid by using a boiler,
The boiler exchanges heat between the first boiler that exchanges heat with the pressurized air, the second boiler that exchanges heat with cooling water for the internal combustion engine, and the reflux exhaust. A third boiler to perform,
The third boiler is located downstream of the first boiler in the circulating direction of the working fluid (Claim 1).

  The waste heat utilization apparatus of the present invention includes a Rankine cycle. This Rankine cycle is used for a drive system and has a boiler to circulate a working fluid. The drive system includes an internal combustion engine, a supercharger that supplies pressurized air to the internal combustion engine, and an exhaust gas recirculation passage that recirculates a part of the exhaust gas generated in the internal combustion engine to the internal combustion engine as recirculation exhaust gas. ing. The boiler has first to third boilers.

  Therefore, this waste heat utilization device can heat the working fluid by heat exchange in the first to third boilers, and can cool the pressurized air, the cooling water for the internal combustion engine, and the recirculated exhaust gas by the working fluid, respectively. It is. In particular, since the density of the recirculated exhaust gas is increased by being cooled, the recirculated exhaust gas is preferably recirculated to the internal combustion engine, that is, taken into the internal combustion engine. For this reason, it becomes possible to operate an internal combustion engine suitably. Furthermore, by recirculating the cooled exhaust gas thus cooled to the internal combustion engine, the content of nitrogen oxides in the exhaust gas when released into the atmosphere can be reduced.

  At this time, according to the knowledge of the inventors, the temperature of the pressurized air is about 150 ° C., whereas the temperature of the exhaust gas generated in the internal combustion engine is about 500 ° C. In the Rankine cycle according to the present invention, since the third boiler is located downstream of the first boiler in the circulation direction of the working fluid, the working fluid is sufficiently heated by the third boiler. Thereby, it becomes possible to make the working fluid which flows into an expander into the state of a superheat or a state close | similar to a superheat, without reducing an evaporation pressure. For this reason, it is possible to increase the pressure energy generated by the expansion and decompression of the working fluid in the expander. In addition, since the working fluid is sufficiently heated in this way, the working fluid is kept vaporized in the expander and is prevented from being liquefied in the expander. For these reasons, in this waste heat utilization apparatus, the amount of energy that can be recovered in the Rankine cycle increases, and the liquid back phenomenon is suppressed, so that the expander is hardly damaged.

  In this waste heat utilization device, the temperature of the working fluid flowing into the first boiler is lower than the temperature of the working fluid flowing out of the third boiler. For this reason, it becomes possible to cool pressurized air suitably in the 1st boiler, and it becomes possible to supply more pressurized air to an internal-combustion engine.

  Therefore, according to the waste heat utilization apparatus of the present invention, the output of the internal combustion engine can be improved and the durability can be increased while improving the amount of energy recovered in the Rankine cycle.

  As the internal combustion engine, various types of engines can be employed in addition to a gasoline engine, a diesel engine, and the like. These engines may be hybrid engines combining motors. On the other hand, a turbocharger, a supercharger, or the like can be employed as the supercharger. There may be a plurality of internal combustion engines and superchargers.

  Here, when a gasoline engine or a hybrid engine in which a gasoline engine and a motor are combined is adopted as an internal combustion engine, pumping loss is suppressed in each of these engines by sucking cooled exhaust gas (recirculation exhaust gas). It becomes. In addition, when a diesel engine or a hybrid engine in which a diesel engine and a motor are combined is adopted as an internal combustion engine, the exhaust gas (reflux exhaust gas) that has been cooled is sucked into the exhaust gas when it is finally released into the atmosphere. It becomes possible to reduce the content of nitrogen oxides.

  Rankine cycle consists of a pump, a first boiler, a second boiler, a third boiler, an expander, a condenser, and a pump through a first boiler, a second boiler, a third boiler, and an expander. It is preferable to have a pipe for circulating the working fluid. In this case, among the first to third boilers, the first boiler is located on the most upstream side in the circulation direction of the working fluid, so that the temperature of the working fluid flowing into the first boiler is the lowest. For this reason, it becomes possible to cool pressurized air suitably, and it becomes possible to improve the output of an internal combustion engine more. Further, since the third boiler is located on the most downstream side in the circulating direction of the working fluid, the working fluid heated by the third boiler is not radiated in the other first and second boilers. For this reason, the temperature of the working fluid flowing into the expander becomes sufficiently high, the working fluid expands suitably in the expander, the amount of energy that can be recovered increases, and the expander is suitably prevented from being damaged. Is done.

  As described above, in the Rankine cycle, when the first boiler, the second boiler, and the third boiler are sequentially arranged in the circulation direction of the working fluid, the working fluid is heated by heat exchange in the second boiler. The temperature of the working fluid flowing into the boiler becomes high. In this case, in the third boiler, there is a concern that the recirculated exhaust gas in the exhaust gas recirculation path is not sufficiently cooled, and that nitrogen oxides contained in the exhaust gas cannot be sufficiently reduced.

  For this reason, in this waste heat utilization apparatus, it bypasses from the piping downstream of the first boiler, bypasses the second boiler and joins the piping, and the flow rate of the working fluid flowing into the second boiler and the bypass passage It is preferable to include a flow rate adjustment valve capable of adjusting the flow rate of the working fluid flowing in, and an adjustment valve control means for controlling the flow rate adjustment valve.

  In this case, it is possible to avoid heat exchange in the second boiler with respect to the working fluid by flowing the working fluid that has flowed out of the first boiler into the bypass passage. Thereby, the temperature of the working fluid flowing into the third boiler can be lowered. For this reason, the recirculated exhaust gas in the exhaust gas recirculation path can be sufficiently cooled, and the nitrogen oxides contained in the exhaust gas can be sufficiently reduced.

  Further, in this waste heat utilization apparatus, the flow rate of the working fluid flowing into the second boiler and the flow rate of the working fluid flowing into the bypass passage can be adjusted by the regulating valve control means controlling the flow rate regulating valve. is there. For this reason, it is possible to suitably cool the internal combustion engine and the recirculated exhaust gas in the exhaust gas recirculation path by adjusting the temperature of the working fluid flowing into the third boiler while cooling the internal combustion engine. It becomes.

  It is preferable that the regulating valve control means controls the flow regulating valve according to the output demand in the drive system or the content of nitrogen oxides in the exhaust.

  For example, in addition to the case where an output request exceeding a predetermined value is made in the drive system, when the content of nitrogen oxides in the exhaust gas exceeds a threshold value, sufficient cooling is performed on the recirculated exhaust gas in the exhaust gas recirculation path. Desired. For this reason, in these cases, the temperature of the working fluid flowing into the third boiler is lowered by increasing the flow rate of the working fluid flowing into the bypass passage rather than the flow rate of the working fluid flowing into the second boiler. Is possible. Thereby, in the third boiler, it becomes possible to sufficiently cool the reflux exhaust in the exhaust gas recirculation path. For this reason, since the intake air temperature in the internal combustion engine decreases and the combustion temperature in the internal combustion engine decreases, the content of nitrogen oxides in the exhaust gas can be reduced.

  According to the waste heat utilization apparatus of the present invention, it is possible to improve the output of the internal combustion engine and improve the durability while improving the amount of energy recovered in the Rankine cycle.

It is a schematic structure figure which shows the waste heat utilization apparatus of an Example. FIG. 3 is a schematic structural diagram showing a state in which a working fluid flows into the second boiler through the first boiler in the waste heat utilization apparatus of the example. It is a schematic structure figure which shows the state which concerns on the waste-heat utilization apparatus of an Example, and a working fluid flows in into a 3rd boiler via a bypass path.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments embodying the present invention will be described below with reference to the drawings.

(Example)
The waste heat utilization apparatus of the embodiment is mounted on a vehicle and is used in a drive system 1 of the vehicle as shown in FIG. The waste heat utilization apparatus includes a Rankine cycle 3, a bypass passage 41, a three-way valve 43, and a control device 11.

  The drive system 1 includes an engine 5 as an internal combustion engine, a turbocharger 7 as a supercharger, a radiator 9, and pipes 15 and 16 as exhaust pipe passages.

  The engine 5 is a known water-cooled diesel engine. A water jacket (not shown) through which cooling water can flow is formed inside the engine 5. The engine 5 is formed with an outlet 5a and an inlet 5b communicating with the water jacket. Further, the engine 5 is formed with an exhaust port 5c for exhausting exhaust gas and an intake port 5d for sucking pressurized air described later.

  The turbocharger 7 and the radiator 9 are also made of public goods. The turbocharger 7 is operated by exhaust generated from the engine 5 and supplies the engine 5 with pressurized air obtained by pressurizing air outside the vehicle. Further, the radiator 9 is formed with an inlet 9a for allowing cooling water to flow into the radiator 9 and an outlet 9b for allowing cooling water to flow out. The radiator 9 performs heat exchange between the cooling water flowing through the radiator 9 and the air outside the vehicle. Further, an electric fan 9 c is provided in the vicinity of the radiator 9. The electric fan 9 c is electrically connected to the control device 11.

  The engine 5 and the turbocharger 7 are connected by a pipe 13, a pipe 17 and a pipe 18. Further, a first boiler 27 described later is connected to the pipe 17 and the pipe 18. The pipe 13 is capable of circulating exhaust gas and is connected to the exhaust port 5 c of the engine 5 and the turbocharger 7. In addition, the piping 17 is capable of circulating pressurized air, and the piping 18 is capable of circulating pressurized air and reflux exhaust. The pipe 17 is connected to the turbocharger 7 and the first inlet 27 a of the first boiler 27. The pipe 18 is connected to the first outlet 27 b of the first boiler 27 and the inlet 5 d of the engine 5.

  Further, the turbocharger 7 is connected to one end sides of the pipes 14 and 19. The other end side of the pipe 14 is connected to a muffler (not shown). The other end of the pipe 19 is open to an air intake of a vehicle (not shown). The pipe 14 communicates with the pipe 13 via the turbocharger 7. Similarly, the pipe 19 communicates with the pipe 17 via the turbocharger 7.

  The pipes 15 and 16 are capable of circulating reflux exhaust, which is part of the exhaust. One end side of the pipe 15 is connected to the pipe 13. Similarly, one end side of the pipe 16 is connected to the pipe 18. The other end of the pipe 15 is connected to a fifth inlet 29a of a third boiler 29 described later. The other end side of the pipe 16 is connected to the fifth outlet 29 b of the third boiler 29. Further, the pipe 15 is provided with a variable valve 21. This variable valve 21 is electrically connected to the control device 11. The pipes 15 and 16 are combined with the pipe 18 through the third boiler 29 for the recirculated exhaust, so that a part of the exhaust discharged from the exhaust 5c of the engine 5 is used as the recirculated exhaust from the intake 5d to the inside of the engine 5. To reflux. Note that one end side of the pipe 15 may be connected to the pipe 14. In this case, one end side of the pipe 16 is connected to the pipe 19.

  On the other hand, the engine 5 and the radiator 9 are connected by pipes 23 to 25. Further, a second boiler 28 described later is connected to the pipe 23 and the pipe 24. The pipes 23 to 25 are capable of circulating cooling water inside. The pipe 23 is connected to the outlet 5 a of the engine 5 and the third inlet 28 a of the second boiler 28. The pipe 24 is connected to the third outlet 28 b of the second boiler 28 and the inlet 9 a of the radiator 9. The pipe 25 is connected to the outlet 9 b of the radiator 9 and the inlet 5 b of the engine 5. The pipe 24 is provided with a first electric pump P1. The first electric pump P1 is electrically connected to the control device 11. The first electric pump P1 may be provided in the pipe 23 or the pipe 24.

  Rankine cycle 3 has the 2nd electric pump P2, the 1st boiler 27, the 2nd boiler 28, the 3rd boiler 29, the expander 31, the condenser 33, and piping 35-40. . In the Rankine cycle 3, the bypass passage 41 and the three-way valve 43 are integrally assembled. An HFC 134a as a working fluid can be circulated in the pipes 35 to 40 and the bypass passage 41. The second electric pump P2 and the three-way valve 43 correspond to a pump and a flow rate adjustment valve, respectively.

  The first boiler 27 is formed with a first inlet 27a and a first outlet 27b, and a second inlet 27c and a second outlet 27d. Further, in the first boiler 27, a first passage 27e communicating with the first inlet 27a and the first outlet 27b at both ends, respectively, and a second inlet 27c and a second outlet 27d at both ends, respectively. The 2nd channel | path 27f which connects is provided. In the first boiler 27, the pressurized air is cooled and the working fluid is heated by exchanging heat between the pressurized air in the first passage 27e and the working fluid in the second passage 27f. In the first boiler 27 and the second boiler 28, the heat source (pressurized air and cooling water) and the working fluid are shown to flow in the same direction. However, in order to more efficiently exchange heat, Both may be in different directions (opposite flow) as in the case of the three boiler 29.

  The second boiler 28 is formed with a third inlet 28a and a third outlet 28b, and a fourth inlet 28c and a fourth outlet 28d. Further, in the second boiler 28, a third passage 28e communicating with the third inlet 28a and the third outlet 28b at both ends, respectively, and a fourth inlet 28c and a fourth outlet 28d at both ends, respectively. A fourth passage 28f that communicates is provided. In the second boiler 28, the cooling water is cooled and the working fluid is heated by exchanging heat between the cooling water in the third passage 28e and the working fluid in the fourth passage 23f.

  The third boiler 29 is formed with a fifth inlet 29a and a fifth outlet 29b, and a sixth inlet 29c and a sixth outlet 29d. Further, in the third boiler 29, a fifth passage 29e communicating with the fifth inlet 29a and the fifth outlet 29b on both ends, respectively, and a sixth inlet 29c and a sixth outlet 29d on both ends, respectively. The 6th channel | path 29f which connects is provided. The third boiler 29 cools the reflux exhaust and heats the working fluid by exchanging heat between the reflux exhaust in the fifth passage 29e and the working fluid in the sixth passage 29f.

  The expander 31 is formed with an inlet 31a through which a working fluid flows in and an outlet 31b through which the working fluid flows out. In the expander 31, the working fluid heated through the third boiler 29 is expanded to generate a rotational driving force. A known generator (not shown) is connected to the expander 31. The generator generates power by the driving force of the expander 31 and charges the battery (not shown) with electric power.

  The condenser 33 is formed with an inflow port 33a through which the working fluid flows in and an outflow port 33b through which the working fluid flows out. The condenser 33 exchanges heat between the working fluid flowing through the inside of the condenser 33 and air outside the vehicle, and cools and liquefies the working fluid decompressed by the expansion in the expander 31. An electric fan 33 c is provided in the vicinity of the condenser 33. The electric fan 33 c is electrically connected to the control device 11.

  The bypass channel 41 causes the working fluid to bypass the second boiler 28 by circulating the working fluid therein. The three-way valve 43 is a switching valve that can selectively switch between a case where all the working fluid flows into the second boiler 28 and a case where all the working fluid flows into the bypass passage 41. The three-way valve 43 is electrically connected to the control device 11.

  These 1st-3rd boilers 27-29, the expander 31, the condenser 33, the bypass path 41, and the three-way valve 43 are connected by the piping 35-40. Specifically, the outlet 33 b of the condenser 33 and the second inlet 27 c of the first boiler 27 are connected by a pipe 35. The second outlet 27 d of the first boiler 27 and the three-way valve 43 are connected by a pipe 36. The three-way valve 43 and the fourth inlet 28 c of the second boiler 28 are connected by a pipe 37. The fourth outlet 28 d of the second boiler 28 and the sixth inlet 29 c of the third boiler 29 are connected by a pipe 38. The sixth outlet 29 d of the third boiler 29 and the inlet 31 a of the expander 31 are connected by a pipe 39. The outlet 31 b of the expander 31 and the inlet 33 a of the condenser 33 are connected by a pipe 40. In addition, one end side of the bypass passage 41 is connected to the three-way valve 43, and the other end side is connected to the pipe 38.

  The second electric pump P2 is provided in the pipe 35. By operating the second electric pump P2, the working fluid is supplied from the second electric pump P2 to the first boiler 27, the second boiler 28 or the bypass passage 41, the third boiler 29, as shown in FIGS. And it circulates in the piping 35-40 in the order which reaches the condenser 33 through the expander 31. That is, among the first to third boilers 27 to 29, the first boiler 27 is located on the most upstream side in the circulating direction of the working fluid in the flowing direction of the working fluid in the Rankine cycle 3. The second boiler 28 is positioned downstream of the first boiler 27, and the third boiler 29 is positioned downstream of the second boiler 28. The bypass path 41 is located on the upstream side of the third boiler 29. Similarly, the three-way valve 43 is located downstream of the first boiler 27 and upstream of the second boiler 28 and the bypass passage 41.

  As shown in FIG. 1, the control device 11 adjusts the amount of heat that the cooling water or the working fluid radiates to the outside air by controlling the operation of the electric fans 9 c and 33 c. Further, the control device 11 controls the operation of the first and second electric pumps P1 and P2. Furthermore, the control device 11 stores a map based on a detection value such as an output request from the drive system 1, and performs opening / closing control of the variable valve 21 and switching control of the three-way valve 43 based on this map. Thereby, the control apparatus 11 functions as a regulating valve control means. The control device 11 is not based on the output request from the drive system 1 as described above, but is detected by directly or indirectly detecting that the content of nitrogen oxides in the exhaust gas exceeds a threshold value. It is also possible to perform opening / closing control of the valve 21 and switching control of the three-way valve 43.

  The waste heat utilization apparatus configured as described above operates as follows by driving the vehicle.

  As shown in FIG. 2, the engine 5 operates in the drive system 1 by driving the vehicle. Thereby, the exhaust discharged from the exhaust port 5 c circulates in the pipe 13. At this time, the control device 11 controls the opening of the variable valve 21 to allow a part of the exhaust gas flowing through the pipe 13 to flow into the pipe 15 (see the one-dot chain arrow in the same figure). The control device 11 controls the opening degree of the variable valve 21 so that more exhaust gas flows into the pipe 15 as the output demand in the drive system 1 increases.

  Exhaust gas flowing through the pipe 13 without flowing into the pipe 15 is discharged from the muffler to the outside of the vehicle through the turbocharger 7 and the pipe 14 (see the same dotted line arrow). At this time, the turbocharger 7 is operated by the exhaust. As a result, air outside the vehicle is sucked into the turbocharger 7 from the pipe 19 and compressed. This air is sucked as pressurized air into the engine 5 from the intake port 5d of the engine 5 through the pipe 17, the first passage 27e of the first boiler 27, and the pipe 18 (see the two-dot chain line arrow in the figure).

  On the other hand, the exhaust gas flowing into the pipe 15, that is, the recirculated exhaust gas, reaches the pipe 18 through the fifth passage 29 e and the pipe 16 of the third boiler 29 and is sucked into the engine 5 together with the pressurized air in the pipe 18.

  The control device 11 operates the first and second electric pumps P1 and P2 and the electric fans 9c and 33c, respectively. As a result, in the drive system 1, the cooling water that has cooled the engine 5 flows out from the outlet 5 a, and passes through the pipe 23, the third passage 28 e of the second boiler 28, and the pipe 24 from the inlet 9 a of the radiator 9. It reaches the inside of the radiator 9. And the cooling water inside the radiator 9 is heat-exchanged with the air around the radiator 9, that is, radiated and cooled. At this time, the control device 11 appropriately changes the operation amount of the electric fan 9c to suitably radiate the cooling water. The cooling water radiated and cooled flows out from the outlet 9b, flows into the engine 5 from the inlet 5b of the engine 5 through the pipe 25, and cools the engine 5 (see the broken line arrow in the figure).

  In the Rankine cycle 3, the control device 11 performs switching control of the three-way valve 43. Specifically, when the output request by the drive system 1 is below a predetermined value, the three-way valve 43 connects the pipe 36 and the pipe 37 and the pipes 36 and 37 and the bypass path 41 are not connected.

  Thereby, as shown by the solid line arrow in the figure, the working fluid discharged by the second electric pump P2 reaches the second passage 27f from the second inlet 27c of the first boiler 27 via the pipe 35. The working fluid exchanges heat with the pressurized air in the first boiler 27. At this time, since the pressurized air flowing through the first passage 27e is compressed by the turbocharger 7 and has a heat of about 150 ° C., the working fluid flowing through the second passage 27f is at a high temperature. Heated. On the other hand, the pressurized air flowing through the first passage 27e radiates heat to the working fluid flowing through the second passage 27f, and thus reaches the engine 5 in a state where it is cooled to a certain degree.

  The working fluid heated in the first boiler 27 flows out from the second outlet 27d, reaches the fourth passage 28f from the fourth inlet 28c of the second boiler 28 via the pipe 36 and the pipe 37. The working fluid exchanges heat with cooling water in the second boiler 28. At this time, the cooling water flowing through the third passage 28 e has a heat of about 80 to 90 ° C. due to the waste heat of the engine 5. Further, since the working fluid flowing through the fourth passage 28 f is already heated to a certain degree in the first boiler 27, it is further heated in the second boiler 28. On the other hand, since the cooling water flowing through the third passage 28e radiates heat to the working fluid flowing through the fourth passage 28f, the cooling water reaches the radiator 9 while being cooled to a certain extent.

  The working fluid heated in the second boiler 28 flows out of the fourth outlet 28d and reaches the sixth passage 29f from the sixth inlet 29c of the third boiler 29 via the pipe 38. The working fluid is heat-exchanged with the recirculated exhaust gas in the third boiler 29. At this time, the recirculated exhaust gas flowing through the fifth passage 29 e has a heat of about 500 ° C. depending on the operating state of the engine 5. For this reason, the working fluid heated in the first and second boilers 27 and 28 is sufficiently heated in the third boiler 29. On the other hand, the recirculated exhaust gas flowing through the fifth passage 29e radiates heat to the working fluid flowing through the sixth passage 29f, and thus returns to the engine 5 together with the pressurized air in a state where it is cooled to a certain extent.

  Thus, by being sufficiently heated by the first to third boilers 27 to 29, the working fluid flows out from the sixth outlet 27d in a superheated state or a state of high temperature and pressure close to superheat, and the piping 39 It goes from the inflow port 31a of the expander 31 into the expander 31 through the above. The high-temperature and high-pressure working fluid expands in the expander 31 and is depressurized. The generator connected to the expander 31 generates power by the pressure energy at this time.

  The working fluid depressurized in the expander 31 flows out from the outlet 31b and reaches the condenser 33 from the inlet 33a of the condenser 33 via the pipe 40. The working fluid of the condenser 33 is cooled by releasing heat to the air around the condenser 33. At this time, the control device 11 appropriately changes the operation amount of the electric fan 33c to suitably dissipate the working fluid and liquefy it. The cooled working fluid flows out from the outflow port 33 b and reaches the first boiler 27 again through the pipe 35.

  On the other hand, when the output request by the drive system 1 is equal to or greater than a predetermined value, for example, when the accelerator opening is equal to or greater than the predetermined value, the control device 11 performs switching control of the three-way valve 43. Thereby, as shown in FIG. 3, the pipe 36 and the bypass path 41 are communicated, and the pipe 36, the bypass path 41 and the pipe 37 are not communicated.

  As a result, the working fluid that has passed through the first boiler 27 flows into the bypass passage 41 as indicated by solid line arrows in FIG. The working fluid in the bypass passage 41 bypasses the second boiler 28 and reaches the sixth passage 29 f of the third boiler 29 from the pipe 38.

  Here, the working fluid that has flowed through the bypass passage 41 flows into the third boiler 29 at a lower temperature than the state shown in FIG. 2 because heat exchange in the second boiler 28 is not performed. . For this reason, in the heat exchange in the third boiler 29, the working fluid receives more heat radiation from the reflux exhaust. As a result, the reflux exhaust in the fifth passage 29c is further cooled.

  The working fluid heated by the third boiler 29 flows out from the sixth outlet 29d, and is expanded and depressurized by the expander 31 and then radiated by the condenser 33, as in the case shown in FIG. .

  As described above, in the Rankine cycle 3 in this waste heat utilization apparatus, the working fluid can be heated by heat exchange in the first to third boilers 27 to 29, and the pressurized air, the cooling water, and the recirculated exhaust are respectively discharged by the working fluid. It is possible to cool.

  Of these first to third boilers 27 to 29, in the third boiler 29, the exhaust gas having a temperature of about 500 ° C. is exchanged with the working fluid for heat exchange. Fully heated. Further, as shown in FIG. 2, in the Rankine cycle 3, among the first to third boilers 27 to 29, the first boiler 27 is located on the most upstream side in the circulation direction of the working fluid, and therefore flows into the first boiler 27. The temperature of the working fluid is the lowest. Thereby, it becomes possible to cool pressurized air suitably, and it becomes possible to supply more pressurized air to the engine 5 by the density of pressurized air increasing. For this reason, it is possible to further improve the output of the engine 5.

  In particular, in this waste heat utilization apparatus, pipes 15 and 16 as exhaust gas recirculation paths are connected to a pipe 13 and a pipe 18, respectively. For this reason, in this waste heat utilization apparatus, it is possible to recirculate the cooled recirculated exhaust gas and cause the engine 5 to intake air. At this time, the density of the reflux exhaust flowing through the pipe 16 and the pipe 18 is increased by the cooling by the heat exchange in the third boiler 29. Therefore, the reflux exhaust in the pipe 16 and the pipe 18 is preferably returned to the engine 5. Will be. By recirculating the reflux exhaust cooled in this way to the engine 5, in this waste heat utilization apparatus, the content of nitrogen oxides in the exhaust when finally discharged into the atmosphere through the pipe 14 and the muffler Can be sufficiently reduced.

  Further, since the variable valve 21 is controlled to open by map control using several detection values such as output requests in the drive system 1, the amount of recirculated exhaust gas recirculated to the engine 5 becomes large under specific conditions. There is. At this time, the flow rate of the recirculated exhaust gas flowing through the fifth passage 29e increases, and it is required that the recirculated exhaust gas be suitably cooled and recirculated by heat exchange in the third boiler 29. For this reason, it is necessary to reduce the temperature of the working fluid flowing into the third boiler 29 as much as possible.

  Here, as described above, in the Rankine cycle 3, when the first boiler 27, the second boiler 28, and the third boiler 29 are positioned in this order in the circulation direction of the working fluid, the working fluid is exchanged by heat exchange in the second boiler 28. As a result, the temperature of the working fluid flowing into the third boiler 29 is increased.

  For this reason, in this waste heat utilization apparatus, when the output request in the drive system 1 becomes high and the output request exceeds a predetermined value, as shown in FIG. With respect to the fluid, it is possible to bypass the second boiler 28.

  Thus, in this waste heat utilization apparatus, it is possible to reduce the temperature of the working fluid flowing into the third boiler 29 by avoiding heat exchange in the second boiler 28 with respect to the working fluid. Thereby, in this waste heat utilization apparatus, in the 3rd boiler 29, it is possible to fully cool the recirculated exhaust gas in the 5th passage 29e. For this reason, in this waste heat utilization apparatus, in the drive system 1, aiming at low fuel consumption, increasing the air density in order to realize the output at low rotation, and sufficiently reducing the nitrogen oxides contained in the exhaust gas Is possible.

  Here, by bypassing the second boiler 28 for the working fluid in this way, the cooling water in the third passage 28e cannot be cooled by heat exchange in the second boiler 28. For this reason, in such a case, the control device 11 increases the amount of heat of the cooling water in the radiator 9 by increasing the amount of operation of the electric fan 9c. Thereby, in this waste heat utilization apparatus, even if the output request in the drive system 1 exceeds a predetermined value, the engine 5 can be suitably cooled. Even when heat exchange is not performed in the second boiler 28, the recirculated exhaust gas in the fifth passage 29e is very hot as described above, so that there is sufficient working fluid in the third boiler 29. Will be heated.

  And even if it is a case where the 2nd boiler 28 is detoured about a working fluid like these and it is a case where the 2nd boiler 28 is not detoured (refer to Drawing 2), in this waste heat utilization device, The third boiler 29 is located on the most downstream side in the circulation direction of the working fluid. For this reason, in this waste heat utilization apparatus, the working fluid heated by the 3rd boiler 29 is not radiated in the other 1st, 2nd boilers 27 and 28. For this reason, in this waste heat utilization apparatus, it becomes possible to make the working fluid which flows into the expander 31 into the state of a superheat or a state close to a superheat. For this reason, it is possible to increase the pressure energy generated by the expansion and decompression of the working fluid in the expander 31. In addition, since the working fluid is sufficiently heated in this way, in this waste heat utilization apparatus, the working fluid is kept vaporized in the expander 31 and liquefied in the expander 31. It is prevented. For these reasons, in this waste heat utilization device, the amount of electric power that can be recovered in the Rankine cycle 3 is increased, and the liquid back phenomenon is suppressed, and the expander 31 is hardly damaged. If the evaporation pressure in the first to third boilers 27 to 29 is lowered, superheat can be secured even with a relatively low temperature heat source (pressurized air, cooling water, and reflux exhaust), but in this case, expansion is performed. The energy collected by the machine 31 is reduced. In this regard, according to this waste heat utilization apparatus, it is possible to ensure superheat of the working fluid without a decrease in the evaporation pressure.

  Therefore, according to this waste heat utilization apparatus, it is possible to improve the output of the engine 5 and improve the durability while improving the amount of power recovered in the Rankine cycle 3.

  In particular, in this waste heat utilization device, since the control device 11 performs switching control of the three-way valve 43 based on an output request greater than or equal to a predetermined value in the drive system 1, an improvement in the amount of electric power recovered in the Rankine cycle 3 and the engine It is easy to achieve both the improvement of the output of 5.

  While the present invention has been described with reference to the embodiments, it is needless to say that the present invention is not limited to the above-described embodiments and can be appropriately modified and applied without departing from the spirit thereof.

  For example, instead of the three-way valve 43, a flow rate adjusting valve that can arbitrarily change the ratio of the working fluid flowing into the second boiler 28 and the ratio of the working fluid flowing into the bypass passage 41 may be adopted. In this case, the working fluid that has passed through the second boiler 28 and the working fluid that has passed through the bypass passage 41 merge in the pipe 38 and then flow into the third boiler 29. At this time, the temperature of the working fluid flowing into the third boiler 29 can be adjusted by the ratio of the working fluid heated in the second boiler 28. Thereby, it becomes possible to make the temperature of the recirculated exhaust gas recirculated to the engine 5 more appropriate in response to the output request in the drive system 1.

  Furthermore, the pipe 40 may be provided with a known receiver. In this case, since the working fluid is suitably liquefied by the receiver, the working fluid that has passed through the condenser 33 is suitably discharged by the second electric pump P2, and is preferably circulated through the pipes 35 to 40 and the bypass passage 41. It becomes.

  The present invention is applicable to vehicles and the like.

DESCRIPTION OF SYMBOLS 1 ... Drive system 3 ... Rankine cycle 5 ... Engine (internal combustion engine)
7 ... Turbocharger (supercharger)
11. Control device (regulating valve control means)
15, 16 ... piping (exhaust gas recirculation path)
DESCRIPTION OF SYMBOLS 27 ... 1st boiler 28 ... 2nd boiler 29 ... 3rd boiler 31 ... Expander 33 ... Condenser 35-40 ... Piping 41 ... Bypass path 43 ... Three-way valve (flow control valve)
P2 ... Second electric pump (pump)

Claims (4)

A drive system having an internal combustion engine, a supercharger that supplies pressurized air to the internal combustion engine, and an exhaust gas recirculation path that recirculates a part of the exhaust gas generated in the internal combustion engine as recirculation exhaust gas A waste heat utilization device having a Rankine cycle that is used and circulates a working fluid with a boiler,
The boiler exchanges heat between the first boiler that exchanges heat with the pressurized air, the second boiler that exchanges heat with cooling water for the internal combustion engine, and the reflux exhaust. A third boiler to perform,
The waste heat utilization apparatus, wherein the third boiler is located downstream of the first boiler in the circulation direction of the working fluid.   The Rankine cycle includes a pump, the first boiler, the second boiler, the third boiler, an expander, a condenser, the pump, the first boiler, the second boiler, and the third boiler. The waste heat utilization apparatus according to claim 1, further comprising a pipe for circulating the working fluid through the boiler and the expander to the condenser. A bypass path that branches from the pipe downstream of the first boiler, bypasses the second boiler and joins the pipe, a flow rate of the working fluid that flows into the second boiler, and a flow path that flows into the bypass path A flow rate adjustment valve capable of adjusting the flow rate of the working fluid;
The waste heat utilization apparatus according to claim 2, further comprising an adjustment valve control means for controlling the flow rate adjustment valve.   The waste heat utilization apparatus according to claim 3, wherein the regulating valve control means controls the flow regulating valve in accordance with an output request in the drive system or a nitrogen oxide content in the exhaust.

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