JP2017066918A - Waste heat recovery device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste heat recovery device that can suppress lowering of output even when an outside air temperature decreases.SOLUTION: A waste heat recovery device 1 includes: a Rankine cycle device 20 having an evaporator 24 for evaporating a working medium M by using cooling water C of an engine 10 as a heat source, an expander 26 for recovering power by expanding the working medium M made to flow out from the evaporator 24 and a condenser 28 for condensing the working medium M made to flow out from the expander 26 by using outer air A as a heat source; an outside air temperature detection section 60 for detecting an outside air temperature; water temperature lowering means 42, 48 for lowering a water temperature of the cooling water C to be supplied to the evaporator 24; and a control section 70 for controlling the operation of the water temperature lowering means 42, 48. When the outside air temperature detected by the outside air temperature detection section 60 is lower than a prescribed determination temperature, the control section 70 controls the water temperature lowering means 42, 48 so as to lower the water temperature of the cooling water C to be supplied to the evaporator 24.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a waste heat recovery device, and more particularly to a waste heat recovery device including a Rankine cycle device.

  As a waste heat recovery apparatus including a Rankine cycle device, for example, a waste heat recovery apparatus described in Patent Document 1 is known. In the waste heat recovery apparatus described in Patent Document 1, the Rankine cycle apparatus uses an engine cooling water as a heat source for heating (a high temperature side heat source) to evaporate the working medium, and an operation that flows out of the evaporator An expander that recovers power by expanding the medium, and a condenser that condenses the working medium that has flowed out of the expander using outside air as a heat source for cooling (low-temperature side heat source).

JP 2014-234007 A

  In the waste heat recovery apparatus as described above, the pressure of the working medium at the inlet of the expander (inlet pressure) increases as the temperature of the working medium in the evaporator increases. Further, the lower the temperature of the working medium in the condenser, the smaller the pressure of the working medium at the outlet of the expander (outlet pressure). Therefore, as the temperature difference between the high temperature side heat source and the low temperature side heat source increases, the ratio of the inlet pressure to the outlet pressure of the expander (expansion ratio) can be increased, and the cycle efficiency can be improved and output (recovered). It is considered that the power can be increased. However, for example, when the waste heat recovery device is used in an extremely cold environment, the outside air temperature is extremely lowered, the expansion ratio becomes too large, and the heat insulation efficiency of the expander may be lowered. In this case, the influence of the reduction in the heat insulation efficiency becomes larger than the influence of the improvement in cycle efficiency due to the increase in the expansion ratio, and as a result, the output may be reduced.

  An object of this invention is to provide the waste-heat recovery apparatus which can suppress the fall of an output even when external temperature falls.

  A waste heat recovery apparatus according to the present invention includes an evaporator that evaporates a working medium using engine cooling water as a heat source, an expander that recovers power by expanding the working medium flowing out of the evaporator, and outside air. A Rankine cycle device having a condenser that is used as a heat source and that condenses the working medium that has flowed out of the expander, an outside air temperature detector that detects the outside air temperature, and a water temperature that lowers the water temperature of the cooling water supplied to the evaporator And a control unit that controls the operation of the water temperature lowering unit. The control unit is a cooling unit that is supplied to the evaporator when the outside air temperature detected by the outside air temperature detecting unit is lower than a predetermined determination temperature. The water temperature lowering means is controlled so that the water temperature decreases.

  In this waste heat recovery apparatus, when the outside air temperature falls below the determination temperature, the temperature of the cooling water supplied to the evaporator is lowered. Thereby, the inlet pressure of the expander can be lowered, and as a result, the expansion ratio of the expander can be lowered to an appropriate range where the influence of the decrease in the heat insulation efficiency does not increase. Therefore, according to this waste heat recovery apparatus, it is possible to suppress a decrease in output even when the outside air temperature decreases.

  The waste heat recovery apparatus according to the present invention further includes an inlet pressure detector that detects an inlet pressure of the expander, and an outlet pressure detector that detects an outlet pressure of the expander, and the controller When the outside air temperature detected by the detection unit is lower than the determination temperature, until the ratio of the inlet pressure detected by the inlet pressure detection unit to the outlet pressure detected by the outlet pressure detection unit is smaller than a predetermined set value, The water temperature lowering means may be controlled so that the temperature of the cooling water supplied to the evaporator is lowered. In this waste heat recovery device, when the outside air temperature falls below the judgment temperature, the temperature of the cooling water supplied to the evaporator is lowered until the expansion ratio of the expander becomes smaller than the set value, and the heat insulation efficiency decreases. The expansion ratio of the expander can be reliably lowered to an appropriate range where the influence does not increase. Therefore, even when the outside air temperature decreases, it is possible to reliably suppress a decrease in output.

  The waste heat recovery apparatus according to the present invention further includes a cooling water passage for circulating the cooling water so as to circulate between the engine and the evaporator, and the water temperature lowering means has a cooling water temperature higher than the valve opening temperature. Including a thermostat that allows the cooling water to flow out from the engine to the cooling water flow path when the temperature becomes high, and the control unit, when the outside air temperature detected by the outside air temperature detecting unit is lower than the judgment temperature, the valve opening temperature of the thermostat May be reduced. According to this waste heat recovery apparatus, when the outside air temperature falls below the judgment temperature, the opening temperature of the thermostat is lowered, and the cooling water having a lower water temperature is circulated through the cooling water flow path, whereby the evaporator The water temperature of the cooling water supplied to can be lowered.

  In the waste heat recovery apparatus according to the present invention, the cooling water flow path is provided with a radiator for cooling the cooling water, the cooling water flow path has a bypass flow path for bypassing the radiator, and the water temperature lowering means is a bypass. The control unit includes a bypass valve that adjusts the flow rate of the cooling water flowing through the flow path, and the control unit reduces the flow rate of the cooling water flowing through the bypass flow path when the outside air temperature detected by the outside air temperature detection unit is lower than the determination temperature. As such, the bypass valve may be controlled. According to this waste heat recovery device, when the outside air temperature is lower than the determination temperature, the flow rate of the cooling water flowing through the bypass flow path is decreased, and the flow rate of the cooling water supplied to the radiator is increased. The water temperature of the cooling water supplied to can be lowered.

  The waste heat recovery apparatus according to the present invention further includes a cooling water passage for circulating cooling water so as to circulate between the engine and the evaporator, and the cooling water passage is provided with a radiator for cooling the cooling water. The cooling water flow path has a bypass flow path that bypasses the radiator, the water temperature lowering means includes a bypass valve that adjusts the flow rate of the cooling water flowing through the bypass flow path, and the control unit is detected by the outside air temperature detection unit. When the outside air temperature is lower than the determination temperature, the bypass valve may be controlled so that the flow rate of the cooling water flowing through the bypass channel is reduced. According to this waste heat recovery device, when the outside air temperature is lower than the determination temperature, the flow rate of the cooling water flowing through the bypass flow path is decreased, and the flow rate of the cooling water supplied to the radiator is increased. The water temperature of the cooling water supplied to can be lowered.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the Rankine-cycle apparatus which can suppress the fall of an output even when external temperature falls.

It is a schematic block diagram of the waste heat recovery apparatus which concerns on embodiment. It is a typical graph showing the relationship between the expansion ratio and heat insulation efficiency in an expander. It is a flowchart which shows the process of the normal mode in the waste heat recovery apparatus of FIG. It is a flowchart which shows the process of the suppression control mode in the waste heat recovery apparatus of FIG. It is a flowchart which shows the process of the bypass control mode in the waste heat recovery apparatus of FIG. It is a schematic block diagram of the waste heat recovery apparatus which concerns on a modification.

  Hereinafter, embodiments according to the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals are used for the same or corresponding elements, and duplicate descriptions are omitted.

  FIG. 1 is a schematic configuration diagram of a waste heat recovery apparatus 1 according to the embodiment. As shown in FIG. 1, the waste heat recovery apparatus 1 is mounted on a vehicle including an engine 10. The applied vehicle is, for example, a commercial vehicle such as a truck and a bus, and may be a large vehicle, a medium vehicle, a normal passenger vehicle, a small vehicle, a light vehicle, or the like. The engine 10 is an engine for driving a vehicle, and is, for example, a diesel engine or a gasoline engine.

  The waste heat recovery apparatus 1 includes a Rankine cycle apparatus 20. The Rankine cycle apparatus 20 includes a working medium pump 22, an evaporator 24, an expander 26, and a condenser 28 on the working medium flow path 30. The working medium channel 30 circulates the working medium M so as to circulate among the working medium pump 22, the evaporator 24, the expander 26, and the condenser 28. Various working media M may be used, and in this example, alternative chlorofluorocarbon, which is a low boiling point medium, is used.

  The working medium pump 22 compresses and sends out the working medium M (pressure feeding), and circulates it in the working medium flow path 30. The evaporator 24 is provided on the downstream side of the working medium pump 22 in the working medium flow path 30. The evaporator 24 is a heat exchanger that uses the cooling water C of the engine 10 as a heat source for heating, and heats and evaporates the working medium M by heat exchange with the cooling water C. The cooling water C is supplied to the evaporator 24 via a cooling water channel 40 described later.

  The expander 26 is provided on the downstream side of the evaporator 24 in the working medium flow path 30. The expander 26 recovers power by expanding the working medium M that has flowed out of the evaporator 24. The expander 26 here is a turbine, rotates while expanding the working medium M evaporated by the evaporator 24, and collects kinetic energy as power. The recovered kinetic energy may be output as a machine output, or may be converted by a generator and output as an electrical output.

  An inlet pressure detector 32 that detects the pressure (inlet pressure) of the working medium M at the inlet of the expander 26 is provided on the upstream side of the expander 26 in the working medium flow path 30 and on the downstream side of the evaporator 24. Yes. In addition, an outlet pressure detector 34 that detects the pressure (outlet pressure) of the working medium M at the outlet of the expander 26 is provided on the downstream side of the expander 26 in the working medium flow path 30 and on the upstream side of the condenser 28. It has been. The inlet pressure detection part 32 and the outlet pressure detection part 34 are comprised by the pressure sensor which can measure the pressure of a liquid and gas, for example.

  The condenser 28 is provided on the downstream side of the expander 26 in the working medium flow path 30. The condenser 28 uses the outside air A as a heat source for cooling, and cools and condenses the gas phase working medium M flowing out from the expander 26. In this example, the condenser 28 cools the working medium M by heat exchange with the refrigerant R. The refrigerant R is cooled using the outside air A and is supplied to the condenser 28 via a refrigerant flow path 50 described later. As the outside air A, for example, traveling wind when the vehicle travels is used.

  The waste heat recovery apparatus 1 further includes a cooling water passage 40 through which the cooling water C is circulated between the engine 10 and the evaporator 24. A thermostat 42 is provided on the downstream side (exit) of the engine 10 in the cooling water passage 40. The thermostat 42 is, for example, an electronically controlled thermostat. The thermostat 42 detects the water temperature of the cooling water C at the outlet of the engine 10, and opens when the detected water temperature of the cooling water C becomes higher than the valve opening temperature, from the engine 10 to the cooling water flow path 40. Allow the cooling water C to flow out. On the other hand, the thermostat 42 is closed when the detected water temperature of the cooling water C is equal to or lower than the valve opening temperature, and blocks (blocks) the outflow of the cooling water C from the engine 10 to the cooling water channel 40.

  The valve opening temperature of the thermostat 42 is set by the control unit 70 described later. In the normal state (normal mode described later), the valve opening temperature is such that the water temperature of the cooling water C is within a range in which the reliability of the engine 10 is ensured in order to keep the cycle efficiency of the Rankine cycle device 20 as high as possible. Set to remain as high as possible. The normal valve opening temperature is set to 80 ° C., for example.

  In the waste heat recovery apparatus 1 of the present embodiment, as will be described later, in the suppression control mode, the valve opening temperature of the thermostat 42 is changed to a value lower than the normal valve opening temperature. When the valve opening temperature decreases, the cooling water C having a lower water temperature flows through the cooling water passage 40. Thereby, the water temperature of the cooling water C flowing through the cooling water flow path 40 is lowered, and as a result, the water temperature of the cooling water C supplied to the evaporator 24 is lowered. That is, the thermostat 42 constitutes a water temperature lowering unit that lowers the water temperature of the cooling water C supplied to the evaporator 24.

  A radiator 44 is provided on the cooling water flow path 40 on the downstream side of the evaporator 24. The radiator 44 cools the cooling water C by, for example, traveling wind (outside air) when the vehicle travels. The cooling water channel 40 has a bypass channel 46 that bypasses the radiator 44. The bypass channel 46 is provided with a bypass valve 48 that adjusts the flow rate of the cooling water C flowing through the bypass channel 46. The bypass valve 48 is, for example, an electromagnetic valve or an electric valve, and adjusts the flow rate of the cooling water C flowing through the bypass flow path 46 by changing the opening according to a control signal input from the control unit 70 described later. In the present specification, the “flow rate” may be a volume flow rate or a mass flow rate.

  As the opening degree of the bypass valve 48 decreases, the flow rate of the cooling water C flowing through the bypass channel 46 decreases, and the flow rate of the cooling water C flowing into the radiator 44 increases. Therefore, when the opening degree of the bypass valve 48 is decreased, the water temperature of the cooling water C flowing through the cooling water flow path 40 is lowered, and consequently the water temperature of the cooling water C supplied to the evaporator 24 is lowered. That is, the bypass valve 48 constitutes a water temperature lowering unit that lowers the water temperature of the cooling water C supplied to the evaporator 24. It should be noted that the opening degree of the bypass valve 48 is set so that the water temperature of the cooling water C is maximized within a range in which the reliability of the engine 10 is ensured in order to keep the cycle efficiency of the Rankine cycle device 20 as high as possible. Controlled to keep high.

  In the present embodiment, the waste heat recovery apparatus 1 further includes a sub-radiator (heat exchanger) 52 and a refrigerant pump 54 on the refrigerant flow path 50. The refrigerant flow path 50 circulates the refrigerant R so as to circulate among the condenser 28, the sub radiator 52, and the refrigerant pump 54. The sub-radiator 52 cools the refrigerant R by heat exchange with the outside air A. The refrigerant pump 54 pumps the refrigerant R and circulates it in the refrigerant flow path 50.

  The waste heat recovery apparatus 1 further includes an outside air temperature detection unit 60 that detects the temperature of the outside air A (outside air temperature). The outside air temperature detection unit 60 is configured by a temperature sensor that can measure the outside air temperature, for example. The outside air temperature detection unit 60 only needs to be provided at a position where the outside air temperature can be detected.

  The waste heat recovery apparatus 1 further includes a control unit 70 that is electrically connected to at least the inlet pressure detection unit 32, the outlet pressure detection unit 34, the thermostat 42, the bypass valve 48, and the outside air temperature detection unit 60. . The control part 70 performs the process shown by the flowchart of FIGS. 3-5 mentioned later. The control unit 70 is configured by a computer including, for example, a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and the like. The control unit 70 may be further electrically connected to elements other than those described above.

  Next, the influence which the fall of external temperature may have on the waste heat recovery apparatus 1 is demonstrated. FIG. 2 is a schematic graph showing the relationship between the ratio of the inlet pressure to the outlet pressure (expansion ratio) in the expander 26 and the heat insulation efficiency. In the waste heat recovery apparatus 1, the inlet pressure of the expander 26 increases as the temperature of the working medium M in the evaporator 24 increases. Moreover, the outlet pressure of the expander 26 decreases as the temperature of the working medium M in the condenser 28 decreases. Therefore, the expansion ratio of the expander 26 can be increased and the cycle efficiency can be improved as the outside air temperature decreases and the temperature difference between the cooling water C (high temperature side heat source) and the outside air A (low temperature side heat source) increases. It is also considered that the output (power recovered) can be increased.

  However, in general, the heat insulation efficiency becomes high in the expansion ratio range corresponding to all the outside air temperature range (for example, −20 ° C. to 30 ° C.) from the midsummer to the extreme cold environment such as the midwinter in the cold region. Thus, it is difficult to design the expander 26. Therefore, as shown in FIG. 2, the expander 26 has an expansion ratio range (appropriate range) P in which the heat insulation efficiency can be kept relatively high. That is, when the temperature difference between the high temperature side heat source and the low temperature side heat source is small and the expansion ratio becomes smaller than the appropriate range P, the heat insulation efficiency is lowered due to insufficient expansion. On the other hand, when the temperature difference between the high temperature side heat source and the low temperature side heat source is large and the expansion ratio exceeds the appropriate range P, the heat insulation efficiency is reduced due to overexpansion.

  Therefore, when a general waste heat recovery device is used in an extremely cold environment, the outside air temperature is extremely lowered, and the expansion ratio of the expander 26 increases beyond the appropriate range P, so that the heat insulation efficiency of the expander 26 is increased. May decrease. In this case, the influence of the reduction in the heat insulation efficiency becomes larger than the influence of the improvement in cycle efficiency due to the increase in the expansion ratio, and as a result, the output may be reduced.

  On the other hand, the waste heat recovery apparatus 1 according to the present embodiment performs the processing described below, so that the expansion ratio of the expander 26 is maintained to an appropriate appropriate range P that can maintain high heat insulation efficiency even when the outside air temperature decreases. It is comprised so that can be reduced. Below, the process by the waste heat recovery apparatus 1 is demonstrated. 3-5 is a flowchart which shows each process by the waste heat recovery apparatus 1. FIG. These processes are performed by the control unit 70. In the initial state, the control mode is the normal mode.

  As shown in FIG. 3, first, it is determined whether or not the rotational speed of the engine 10 is larger than a predetermined threshold (S11). This threshold is set to 500 min−1, for example. If the rotational speed of the engine 10 is greater than the threshold value (YES in S11), the process proceeds to step S12. If the rotational speed of the engine 10 is equal to or less than the threshold value (NO in S11), the process proceeds to step S14.

  In step S12, it is determined whether or not the outside air temperature detected by the outside air temperature detecting unit 60 is lower than a predetermined determination temperature. If the outside air temperature is lower than the determination temperature (YES in S12), the process proceeds to step S13. If the outside air temperature is equal to or higher than the determination temperature (NO in S11), the process proceeds to step S14. In step S13, the control mode is switched to the suppression control mode, and the normal mode is terminated. In the suppression control mode, a process for lowering the water temperature of the cooling water C is performed as described later.

  The determination temperature in step S12 is a value set in advance in order to appropriately determine whether or not to start the process for reducing the water temperature of the cooling water C. The determination temperature may be determined based on experiments, past results and experiences, simulations, and the like, and is set to −5 ° C., for example. Note that the determination temperature may be a fixed value or a fluctuating value.

  In step S14, the opening temperature of the thermostat 42 is set to a normal value, and the opening degree of the bypass valve 48 is set to a normal opening degree. Then, it returns to step S11 and performs each process of normal mode again.

  As shown in FIG. 4, in the suppression control mode, first, the expansion ratio of the expander 26 is calculated from the inlet pressure detected by the inlet pressure detector 32 and the outlet pressure detected by the outlet pressure detector 34 ( S21). Next, it is determined whether or not the calculated expansion ratio is greater than a predetermined set value (S22). When the expansion ratio is equal to or lower than the set value (NO in S22), the control mode is switched to the normal mode (S23), and the suppression control mode is terminated. On the other hand, when the expansion ratio is larger than the set value (YES in S22), the process proceeds to step S24.

  The set value in step S22 is a value set in advance in order to appropriately determine whether or not the expansion ratio has decreased to the appropriate range P. This set value may be determined based on experiments, past results and experience, simulation, and the like, and is set to 10, for example. The set value may be a fixed value or a variable value.

  In step S24, it is determined whether the valve opening temperature of the thermostat 42 is higher than a predetermined lower limit temperature. When the valve opening temperature of the thermostat 42 is higher than the lower limit temperature (YES in S24), the process proceeds to step S25. On the other hand, when the valve opening temperature is equal to or lower than the lower limit temperature (NO in S24), it is determined that the valve opening temperature cannot be further reduced, and the process proceeds to step S26. The lower limit temperature in step S24 is a value for appropriately determining whether to end the suppression control mode and start the bypass control mode, and is set to 70 ° C., for example.

  In step S25, the valve opening temperature of the thermostat 42 is lowered. For example, the valve opening temperature of the thermostat 42 is decreased by a predetermined value (for example, 5 ° C.). Thereby, the water temperature of the cooling water C flowing through the cooling water flow path 40 is lowered, and as a result, the water temperature of the cooling water C supplied to the evaporator 24 is lowered. Then, it returns to step S21 and performs each process of suppression control mode again. In step S26, the control mode is switched to the bypass control mode, and the suppression control mode is terminated.

  As shown in FIG. 5, in the bypass control mode, first, similarly to steps S21 and S22, an expansion ratio is calculated (S31), and it is determined whether or not the calculated expansion ratio is larger than a predetermined set value. (S32). If the expansion ratio is less than or equal to the set value (NO in S32), the control mode is switched to the normal mode (S36), and the bypass control mode is terminated. On the other hand, when the expansion ratio is larger than the set value (YES in S32), the process proceeds to step S33. As the set value in step S32, for example, the same value as the set value in step S22 is used.

  In step S33, it is determined whether or not the opening degree of the bypass valve 48 is larger than a predetermined minimum opening degree. If the opening is larger than the minimum opening (YES in S33), the process proceeds to step S34. On the other hand, when the opening degree is equal to or smaller than the minimum opening degree (NO in S33), it is determined that the opening degree of the bypass valve 48 cannot be further reduced, and the process proceeds to step S35. This minimum opening is a value for appropriately determining whether or not to terminate the bypass control mode by executing the waste heat recovery suppression process described later, and is set to 50%, for example.

  In step S34, the bypass valve 48 is controlled so that the flow rate of the cooling water C flowing through the bypass flow path 46 is decreased by changing the opening degree of the bypass valve 48. For example, the opening degree of the bypass valve 48 is decreased by a predetermined value (for example, 5%). Thereby, the water temperature of the cooling water C flowing through the cooling water flow path 40 is lowered, and as a result, the water temperature of the cooling water C supplied to the evaporator 24 is lowered. Then, it returns to step S31 and performs each process of bypass control mode again.

  In step S35, waste heat recovery suppression processing is executed. For example, the operation of the working medium pump 22 is stopped, or the discharge amount of the working medium pump 22 is decreased. Thereby, waste heat recovery by the waste heat recovery apparatus 1 is suppressed. After execution of the waste heat recovery suppression process, the control mode is switched to the normal mode (S36), and the bypass control mode is terminated.

  As described above, in the waste heat recovery apparatus 1, when the outside air temperature is lower than the determination temperature, the water temperature of the cooling water C supplied to the evaporator 24 is lowered. As a result, the inlet pressure of the expander 26 can be lowered, and as a result, the expansion ratio of the expander 26 can be lowered to an appropriate range P where the influence of a decrease in the heat insulation efficiency does not increase. Therefore, according to the waste heat recovery apparatus 1, it is possible to suppress a decrease in output even when the outside air temperature decreases.

  Further, in the waste heat recovery apparatus 1, when the outside air temperature is lower than the determination temperature, the water temperature of the cooling water C supplied to the evaporator 24 is lowered until the expansion ratio of the expander 26 becomes smaller than a set value. The expansion ratio of the expander 26 can be reliably reduced to an appropriate range P where the influence of the decrease in the heat insulation efficiency does not increase. Therefore, according to the waste heat recovery apparatus 1, it is possible to reliably suppress a decrease in output even when the outside air temperature decreases.

  Further, according to the waste heat recovery apparatus 1, when the outside air temperature falls below the determination temperature, the valve opening temperature of the thermostat 42 is lowered, and the cooling water C having a lower water temperature flows through the cooling water passage 40. Thereby, the water temperature of the cooling water C supplied to the evaporator 24 can be reduced.

  Further, according to the waste heat recovery apparatus 1, when the outside air temperature is lower than the determination temperature, the flow rate of the cooling water C flowing through the bypass channel 46 is decreased, and the flow rate of the cooling water C supplied to the radiator 44 is increased. By doing so, the water temperature of the cooling water C supplied to the evaporator 24 can be lowered.

  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.

  FIG. 6 is a schematic configuration diagram of a waste heat recovery apparatus according to a modification. For example, as shown in FIG. 6, the present invention may be configured as a waste heat recovery apparatus 1A. The waste heat recovery apparatus 1 </ b> A of the modified example has the waste heat recovery of the above embodiment in that a bypass valve 48 </ b> A is provided at a branching position between the flow path upstream of the radiator 44 and the bypass flow path 46 in the cooling water flow path 40. Different from the device 1. The bypass valve 48A is, for example, a three-way valve, and switches the flow path of the cooling water C between the flow path on the upstream side of the radiator 44 and the bypass flow path 46, thereby allowing the cooling water C flowing through the bypass flow path 46 to flow. Adjust the flow rate. That is, in the waste heat recovery apparatus 1 </ b> A, in the process corresponding to step S <b> 34, the control unit 70 switches the flow path for the cooling water C through the bypass valve 48, thereby changing the cooling water C flowing through the bypass flow path 46. The bypass valve 48 is controlled so that the flow rate decreases.

  Even with the waste heat recovery apparatus 1A, similarly to the above embodiment, it is possible to suppress a decrease in output even when the outside air temperature decreases. Further, by flowing the entire amount of the cooling water C flowing through the cooling water channel 40 into the bypass channel 46, the cooling water C is prevented from being cooled by the radiator 44, and the water temperature of the cooling water C flowing through the cooling water channel 40 is Can be suppressed. As a result, the water temperature of the cooling water C that is the high-temperature side heat source can be kept high, and the working medium M that has flowed into the evaporator 24 can be more suitably heated and evaporated.

  In the above embodiment, both the thermostat 42 and the bypass valve 48 are used as the water amount reducing means, but only one of them may be used. When only the thermostat 42 is used as the water amount lowering means, the radiator 44, the bypass passage 46, or the bypass valve 48 may be omitted.

  In the above embodiment, the suppression control mode (see FIG. 4) for lowering the valve opening temperature of the thermostat 42 is executed first, and the opening degree of the bypass valve 48 is changed when the expansion ratio is still larger than the set value. Although the mode (see FIG. 5) is further executed, on the contrary, the bypass control mode may be executed first, or the suppression control mode and the bypass control mode may be executed simultaneously.

  In the above embodiment, when the outside air temperature is lower than the determination temperature, the water amount is decreased so that the temperature of the cooling water C supplied to the evaporator 24 is decreased until the expansion ratio of the expander 26 becomes smaller than the set value. Although the means is controlled, the present invention is not limited to this. The water amount reducing means may be controlled without determining whether or not the expansion ratio has actually decreased to the appropriate range P. In short, when the outside air temperature detected by the outside air temperature detecting unit 60 is lower than the determination temperature, the water temperature of the cooling water C supplied to the evaporator 24 may be lowered.

  In the above embodiment, the working medium M is cooled by heat exchange between the outside air A and the refrigerant R in the condenser 28. However, the condenser 28 only needs to use the outside air A as a heat source for cooling. An air-cooling type that directly cools the working medium M using A may be used. Further, when the water temperature of the cooling water C does not decrease to the appropriate range P even when the suppression control mode is performed, control for limiting the output of the engine 10 may be performed.

  In the above embodiment, when the temperature of the cooling water C becomes higher than the valve opening temperature, the opening degree of the thermostat 42 is changed from 0% (closed) to 100% (opened), and the cooling water flow path from the engine 10 is changed. Although the outflow of the cooling water C to 40 is permitted, the opening degree of the thermostat 42 may be changed continuously or stepwise. For example, the opening degree of the thermostat 42 is increased continuously or stepwise (for example, three or more) so that the opening degree of the thermostat 42 increases as the difference between the water temperature of the cooling water C and the valve opening temperature increases. It may be changed (between set values).

DESCRIPTION OF SYMBOLS 1 ... Waste heat recovery apparatus, 10 ... Engine, 20 ... Rankine cycle apparatus, 24 ... Evaporator, 26 ... Expander, 28 ... Condenser, 32 ... Inlet pressure detection part, 34 ... Outlet pressure detection part, 40 ... Cooling water flow Road, 42 ... Thermostat, 44 ... Radiator, 46 ... Bypass flow path, 48 ... Bypass valve, 60 ... Outside air temperature detection part, 70 ... Control part, A ... Outside air, C ... Cooling water, M ... Working medium.

Claims (5)

An evaporator that evaporates the working medium using engine cooling water as a heat source, an expander that recovers power by expanding the working medium that has flowed out of the evaporator, and an outside air that is used as a heat source from the expander A Rankine cycle device having a condenser for condensing the outflowing working medium;
An outside air temperature detector for detecting outside air temperature,
Water temperature lowering means for lowering the temperature of the cooling water supplied to the evaporator;
A controller for controlling the operation of the water temperature lowering means,
The controller is
When the outside air temperature detected by the outside air temperature detecting unit is lower than a predetermined determination temperature, the waste heat recovery device controls the water temperature lowering means so that the water temperature of the cooling water supplied to the evaporator is lowered. . An inlet pressure detector for detecting an inlet pressure of the expander;
An outlet pressure detector that detects an outlet pressure of the expander,
The controller is
When the outside air temperature detected by the outside air temperature detecting unit is lower than the determination temperature, a ratio of the inlet pressure detected by the inlet pressure detecting unit to the outlet pressure detected by the outlet pressure detecting unit is a predetermined value. The waste heat recovery apparatus according to claim 1, wherein the water temperature lowering unit is controlled so that a temperature of the cooling water supplied to the evaporator is lowered until the temperature becomes smaller than a set value. A cooling water flow path for circulating the cooling water to circulate between the engine and the evaporator;
The water temperature lowering means includes a thermostat that allows the cooling water to flow out from the engine to the cooling water flow path when the temperature of the cooling water becomes higher than the valve opening temperature,
The waste heat recovery apparatus according to claim 1 or 2, wherein the controller reduces the valve opening temperature of the thermostat when the outside air temperature detected by the outside air temperature detecting unit is lower than the determination temperature. The cooling water flow path is provided with a radiator for cooling the cooling water,
The cooling water flow path has a bypass flow path that bypasses the radiator,
The water temperature lowering means includes a bypass valve for adjusting a flow rate of the cooling water flowing through the bypass flow path,
The said control part controls the said bypass valve so that the flow volume of the said cooling water which flows through the said bypass flow path may be reduced, when the outside air temperature detected by the said outside air temperature detection part is lower than the said determination temperature. 3. The waste heat recovery apparatus according to 3. A cooling water flow path for circulating the cooling water to circulate between the engine and the evaporator;
The cooling water flow path is provided with a radiator for cooling the cooling water,
The cooling water flow path has a bypass flow path that bypasses the radiator,
The water temperature lowering means includes a bypass valve for adjusting a flow rate of the cooling water flowing through the bypass flow path by changing an opening degree,
The said control part controls the said bypass valve so that the flow volume of the said cooling water which flows through the said bypass flow path may be reduced, when the outside air temperature detected by the said outside air temperature detection part is lower than the said determination temperature. The waste heat recovery apparatus according to 1 or 2.

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