JP2011231703A - Engine exhaust heat regeneration system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly efficient engine exhaust heat regeneration system.SOLUTION: The engine exhaust heat regeneration system includes a heat exchanger that vaporizes coolant by heating with exhaust heat from the engine, an expansion machine that expands the vaporized coolant to generate output, a condenser that cools and condenses the coolant vapor discharged from the expansion machine, and a coolant pump that pressure-sends and circulates the liquid coolant. The heat exchanger includes a first heat exchanger in which flow of the coolant and flow of engine cooling fluid become parallel, and a second heat exchanger connected to the downstream of the first heat exchanger regarding coolant flow, and in which flow of the coolant and flow of the engine cooling fluid become counterflow. A flow rate adjusting valve that adjusts cooling water flow rate or a bypass flow passage of the second heat exchanger can be provided.

Description

  The present invention relates to an engine exhaust heat regeneration system that regenerates exhaust heat discharged to the outside as cooling water or exhaust gas of an internal combustion engine such as an automobile engine as power or the like by a Rankine cycle.

  In an internal combustion engine (hereinafter referred to as an engine), an exhaust heat regeneration system that regenerates exhaust heat discharged outside through cooling water as power by Rankine cycle is an engine coolant and Rankine cycle refrigerant (for example, R134a). Heat is exchanged between the two and power is generated in the Rankine cycle. The exhaust heat regeneration system is a heat exchanger that heats and evaporates the refrigerant with the exhaust heat of the cooling water from the engine, an expander that expands the vaporized refrigerant that is heated and vaporized, and generates an output. It is composed of a condenser that cools and condenses the refrigerant vapor discharged after generation, and a refrigerant pump that pumps and circulates liquid refrigerant. In such an exhaust heat regeneration system, the heat exchanger that exchanges heat between the engine coolant and the refrigerant is configured to exchange heat between the coolant and the refrigerant as an opposing flow. (For example, refer to Patent Document 1).

Japanese Patent Laying-Open No. 2005-337063 (page 6, FIG. 1)

  When an automobile is in operation, the engine coolant at about 90 ° C. is generally circulated at a rate of several liters to several tens of liters per minute. The engine cooling water exchanges heat with the refrigerant in the heat exchanger, the temperature drops to about several degrees Celsius, returns to the engine, and circulates to cool the engine. On the other hand, the refrigerant (for example, R134a) is heated by engine cooling water in a heat exchanger, becomes steam, is led to an expander, and expands to generate power. The engine coolant and the refrigerant exchange heat with each other. The liquid refrigerant pumped by the refrigerant pump is heated by the engine cooling water of about 90 ° C. in the heat exchanger, heated to near that temperature (about 90 ° C.), boils, and starts to evaporate. Since the pressure is constant, the temperature of the evaporating refrigerant that starts and evaporates is constant. At this time, the temperature difference between the evaporating temperature of the refrigerant and the engine cooling water is as small as only a few degrees C or less, extremely 1 C or less, and the heat exchange temperature between the engine cooling water and the refrigerant after the evaporation of the refrigerant starts. Since the difference is small, it is difficult to obtain sufficient heat exchange. As described above, conventionally, it is difficult to sufficiently transfer and recover the exhaust heat of the engine coolant to the refrigerant, and the refrigerant may not be completely vaporized, and sufficient power is generated by the expander. There was a problem that it was not possible to achieve high efficiency as an exhaust heat regeneration system. In addition, in order to perform sufficient heat exchange with a small temperature difference, it is necessary to provide a large heat exchanger having a large heat exchange area, and it becomes difficult to apply the exhaust heat regeneration system to an automobile having a limited installation space. There was also a problem.

  Therefore, the object of the present invention is a compact heat exchanger applicable to automobiles with limited space, which recovers exhaust heat of engine cooling water and sufficiently heats and evaporates the refrigerant to generate large power in the expander. And to obtain an engine exhaust heat regeneration system that achieves high efficiency.

  An engine exhaust heat regeneration system according to the present invention includes a heat exchanger that heats and vaporizes a refrigerant with exhaust heat from the engine, an expander that expands the vaporized refrigerant to generate an output, and the expander In the exhaust heat regeneration system comprising a condenser that cools and condenses the refrigerant vapor discharged from the refrigerant and a refrigerant pump that pumps and circulates the liquid refrigerant, the heat exchanger is configured so that the refrigerant and the engine cooling water flow in parallel. A first heat exchanger, and a second heat exchanger connected downstream of the refrigerant flow with respect to the first heat exchanger, wherein the refrigerant and the engine coolant are opposed to each other are provided. Is.

  According to the engine exhaust heat regeneration system of the present invention, the heat exchange temperature difference between the refrigerant and the engine coolant becomes large, the refrigerant is sufficiently heated and vaporized, and a large expander work is obtained to achieve high efficiency. Can do.

1 is a configuration diagram showing an engine exhaust heat regeneration system according to Embodiment 1 of the present invention. FIG. FIG. 2 is a Mollier diagram of the engine exhaust heat regeneration system of FIG. 1. It is a figure which shows the structure of the conventional general exhaust heat regeneration system. It is a Mollier diagram of a conventional general exhaust heat regeneration system. It is a block diagram which shows the engine exhaust-heat regeneration system by Embodiment 2 of this invention. It is a figure of the experimental result which shows the relationship between the flow volume of engine cooling water, and refrigerant | coolant evaporation temperature. It is a block diagram which shows the engine exhaust-heat regeneration system by Embodiment 3 of this invention. It is a figure which shows an example of the heat exchanger which can be used for the engine waste heat regeneration system by Embodiment 4 of this invention. It is a figure which shows another example of the heat exchanger which can be used for the engine exhaust-heat regeneration system by Embodiment 4 of this invention. It is a figure which shows another example of the heat exchanger which can be used for the engine exhaust-heat regeneration system by Embodiment 4 of this invention. It is a block diagram which shows the engine exhaust heat regeneration system by Embodiment 5 of this invention.

  DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings in order to explain the present invention in more detail. In addition, in each figure, the same code | symbol is attached | subjected to the part which is the same or it corresponds, The duplication description is simplified or abbreviate | omitted suitably.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing an engine exhaust heat regeneration system according to Embodiment 1 of the present invention. The engine 1 is, for example, an internal combustion engine that generates driving force for driving a car. The cooling water circuit 2 for cooling the engine 1 is provided with a cooling water pump 3, a first heat exchanger 7, and a second heat exchanger 8 in a circulation passage 2a for circulating the engine cooling water. The cooling water is circulated in the order of the second heat exchanger 8 and the first heat exchanger 7 by the cooling water pump 3, and circulates back to the engine 1.

  The exhaust heat regenerator 5 is a circulation channel 11 in which a refrigerant is circulated by connecting a refrigerant pump 6, a first heat exchanger 7, a second heat exchanger 8, an expander 9, and a condenser 10 in order. It is configured. A power generator 12 driven by the output is connected to the expander 9. The condenser 10 is provided with a fan 13 for cooling the air. The inside of the circulation flow path 11 of the exhaust heat regeneration device 5 is filled with a refrigerant, for example, R134a, and the refrigerant pump 6 pumps the liquid refrigerant to the first heat exchanger 7 for circulation. In the first heat exchanger 7, the engine cooling water and the refrigerant from the engine 1 are configured to exchange heat in parallel flow, and in the second heat exchanger 8, the cooling water and the refrigerant from the engine 1 are opposed to each other. Heat exchange.

  Next, the operation of the exhaust heat regeneration system in the present embodiment will be described. Here, a description will be given by taking a specific example of a case where a small vehicle of 1300 cc class is traveling at a vehicle speed of 40 km / h that is normally used. The engine cooling water circulating through the cooling water circuit 2 by the cooling water pump 3 is about 93 ° C., and the heat radiation from the engine to the cooling water is about 5600 W. When the engine coolant flow rate is 20 L / min, if this heat is dissipated, the engine coolant decreases by 4 ° C. and returns to the engine at 89 ° C., and the engine operation is continued.

  FIG. 2 is a Mollier diagram showing the state of the refrigerant in the exhaust heat regeneration system according to Embodiment 1 of the present invention. The operation of the exhaust heat regeneration system according to the first embodiment of the present invention will be described with reference to FIGS. The low-pressure refrigerant (state A) at 30 ° C. cooled and liquefied by the condenser 10 becomes high-pressure liquid (state B) by the refrigerant pump 6 and is sent to the first heat exchanger 7. In the first heat exchanger 7, as described later, the refrigerant exchanges heat in parallel with the engine cooling water that has reached about 91 ° C. after heat exchange with the refrigerant in the second heat exchanger 8, up to 86 ° C. It is heated and begins to evaporate (state C), while the engine cooling water drops to 89 ° C. and returns to the engine.

  The refrigerant that has started to evaporate (state C) enters the second heat exchanger, exchanges heat with the 93 ° C. engine cooling water discharged from the engine 1, and completely evaporates (state D). Heated to 92.9 ° C. (state E), while the engine cooling water drops to about 91 ° C. and enters the first heat exchanger 7. The high-temperature and high-pressure refrigerant vapor (state E) expands in the expander 9 to generate work, and is discharged from the expander 9 as low-pressure vapor refrigerant (state F).

  The refrigerant vapor discharged from the expander 9 is radiated to the atmosphere by the condenser 10 and becomes a low-temperature liquid again (state A) and enters the refrigerant pump 6, which is repeated and continuously works from the expander 9. Can be taken out. In the example shown in FIG. 1, the expander 9 is connected to the generator 12 and can be taken out as electric power, which can cover the electric power required by the automobile, and the fuel efficiency is improved by about 5%. To do.

  As described above, the engine exhaust heat regeneration system according to the present invention includes a heat exchanger (first heat exchanger 7 and second heat exchanger 8) that heats the refrigerant with exhaust heat from the engine 1 and vaporizes the steam, An expander 9 that expands the converted refrigerant to generate an output, a condenser 10 that cools and condenses the refrigerant vapor discharged from the expander 9, and a refrigerant pump 6 that pumps and circulates liquid refrigerant are provided. In the exhaust heat regeneration system, the heat exchangers 7 and 8 are disposed on the downstream side of the refrigerant flow with respect to the first heat exchanger 7 in which the refrigerant and the engine coolant flow in parallel, and the first heat exchanger 7. The second heat exchanger 8 is connected and the refrigerant and the engine cooling water are opposed to each other.

  With this configuration, the heat exchange temperature difference between the refrigerant and the engine coolant is increased, sufficient heat exchange can be performed, and the refrigerant is sufficiently heated and vaporized to obtain large expander work and achieve high efficiency An exhaust heat regeneration system can be obtained. In addition, since the heat exchange temperature difference becomes large, a large heat exchange area is not required, and it is possible to perform sufficient heat exchange with a compact heat exchanger with a small heat exchange area. Application of heat regeneration system becomes easy.

Comparative Example 1
For comparison with the present invention, FIG. 3 shows a configuration of a conventional general engine exhaust heat regeneration system in which engine coolant and refrigerant exchange heat only with a counterflow heat exchanger. 4 is a Mollier diagram showing the state of the operation. In FIG. 3, in order to facilitate comparison with the first embodiment of the present invention, the heat exchanger that exchanges heat between the engine cooling water and the refrigerant in the opposite flow is used as the first heat exchanger 14 and the second heat exchange. It is drawn in two parts with the container 15.

  The 30 ° C. low-pressure refrigerant (state A0) liquefied by the condenser 10 becomes high-pressure liquid (state B0) by the refrigerant pump 6 and is sent to the first heat exchanger 14. In the first heat exchanger 14, the refrigerant exchanges heat with the engine cooling water that has reached about 92 ° C. after the heat exchange with the refrigerant in the second heat exchanger 15, and heat-exchanges to 89 ° C. to evaporate. (State C0), on the other hand, the engine cooling water drops to 90 ° C. and returns to the engine. The refrigerant that has started to evaporate enters the second heat exchanger 15 and exchanges heat with the 93 ° C. engine cooling water exiting the engine 1 as a counter flow.

  In the exhaust heat regeneration system of the present invention described above and shown in FIGS. 1 and 2, the average temperature difference between the engine coolant and the refrigerant in the second heat exchanger 8 is about 6 ° C. On the other hand, in the exhaust heat regeneration system of the comparative example shown in FIGS. 3 and 4, the average temperature difference between the engine coolant and the refrigerant in the second heat exchanger 15 becomes as small as about 3.5 ° C. In proportion to this, the heat exchange amount here is also reduced by about 40%. Therefore, in the second heat exchanger 15, a part of the refrigerant evaporates (state E0), while the engine cooling water decreases to about 92 ° C. and enters the first heat exchanger.

  The refrigerant vapor (state E0), which is partly in liquid high temperature and high pressure, expands in the expander 9 to generate work, and becomes low-pressure vapor refrigerant and is discharged from the expander 9 (state F0). The refrigerant vapor discharged from the expander 9 is dissipated to the atmosphere by the condenser 10 to become a low-temperature liquid again (state A0) and enters the refrigerant pump 6, and this process is repeated to continuously work from the expander 9. Can be taken out.

  Thus, in the exhaust heat regeneration system using the counterflow heat exchanger of Comparative Example 1, the amount of heat transferred from the engine coolant to the refrigerant is about 20 than that in the exhaust heat regeneration system according to the first embodiment of the present invention. %, The work generated by the expander 9 is also reduced by about 20%.

  As described above, according to the present invention, the refrigerant can perform sufficient heat exchange with the engine cooling water, and the refrigerant is sufficiently heated and vaporized to obtain a large expander work and achieve high efficiency. You can get a system. In addition, since the heat exchange temperature difference becomes large, a large heat exchange area is not required, and it is possible to perform sufficient heat exchange with a compact heat exchanger with a small heat exchange area. There is also an effect that the application of the heat regeneration system becomes easy.

Embodiment 2. FIG.
In the exhaust heat regeneration system shown in FIG. 5, a flow rate control valve 4 is provided in a cooling water circuit 2 for cooling the engine 1. In the illustrated example, the flow control valve 4 is connected to a circulation flow path 2 a between the cooling water pump 3 of the cooling water circuit 2 and the second heat exchanger. Other configurations are the same as those shown in FIG.

  FIG. 6 shows the refrigerant when the flow rate of the engine cooling water is changed by the flow rate control valve 4 under the condition that the temperature of the engine cooling water discharged from the engine in the 1300 cc engine in the exhaust heat regeneration system shown in FIG. It is a figure which shows the experimental result which investigated the change of evaporation temperature. When the flow rate of the engine coolant is changed from 12 L / min to 30 L / min by the flow rate control valve 4, the evaporation temperature of the refrigerant changes from 90 ° C. to 93 ° C., and the flow rate of the engine coolant is changed by the flow rate control valve 4. It can be seen that the refrigerant evaporation temperature can be controlled.

  According to this exhaust heat regeneration system, the flow rate control valve is connected between the engine 1 and the second heat exchanger 8 and adjusts and controls the flow rate of the cooling water supplied from the engine 1 to the second heat exchanger 8. 4, the refrigerant evaporating temperature can be controlled by changing the flow rate of the engine cooling water by the flow rate control valve 4, and the heat exchange temperature difference can be appropriately controlled according to the engine operating conditions and the refrigerant circulation amount. As in the case of the first embodiment, the refrigerant can perform sufficient heat exchange with the engine cooling water, and the refrigerant is sufficiently heated and vaporized to obtain a large expander work and to achieve high efficiency. A regenerative system can be obtained.

Embodiment 3 FIG.
In the exhaust heat regeneration system shown in FIG. 7, the configuration shown in FIG. 5 includes a bypass passage 16 through which engine coolant bypasses the second heat exchanger 8 and a flow rate adjustment valve 21 provided in the bypass passage 17. It is added and provided. Other configurations are the same as those shown in FIG.

  Generally, when the pressure of the refrigerant discharged from the refrigerant pump 6 is high and the evaporation temperature is high, the amount of heat exchange with the refrigerant with the engine cooling water is less after the evaporation than the amount of heat exchange until the evaporation. However, according to this configuration, since the bypass flow path 16 having the flow rate adjusting valve 17 that connects the engine to the first heat exchanger 7 without the second heat exchanger is provided, the engine operating conditions and the refrigerant circulation are provided. Depending on the amount, the engine cooling water can bypass the second heat exchanger 8 by the flow rate adjusting valve 17 and can flow to the first heat exchanger 7 to efficiently exchange heat with the refrigerant without waste. Thus, a large expander work can be obtained and high efficiency can be realized.

Embodiment 4 FIG.
In the above Embodiments 1 to 3, the first heat exchanger 7 and the second heat exchanger 8 are illustrated as separate ones. However, as shown in FIGS. The second heat exchanger 8 can be combined to form a single integrated unit, and in this case, the same effect can be obtained. In the example shown in FIG. 8, the two cooling water circulation channels 2 a are arranged in a heat exchange relationship along the common refrigerant circulation channel 11 so that the flow directions are opposite to each other. In the example shown in FIG. 9, two cooling water circulation channels 11 are provided outside the two cooling water circulation channels 2 a that are folded and overlapped so that the flow directions are opposite to each other. The other is arranged in a heat exchange relationship so as to be parallel flow. In the example shown in FIG. 10, two refrigerant circulation channels 11 are arranged in a heat exchange relationship along a common cooling water circulation channel 2 a so that the flow directions are opposite to each other.

Embodiment 5 FIG.
In the exhaust heat regeneration system shown in FIG. 11, an exhaust gas heat exchanger 18 provided in the exhaust pipe 1 a of the engine 1 and heated by exhaust gas is connected between the second heat exchanger 8 and the expander 9. Has been. As described above, the exhaust gas heat exchanger 18 can be configured to further recover heat from the engine exhaust gas by the refrigerant recovered from the engine cooling water. With this configuration, more heat can be recovered and the refrigerant vapor can be heated to a higher temperature, and a greater fuel efficiency improvement effect can be obtained.

  The exhaust heat regeneration system illustrated and described above is merely an example, and various modifications can be made, and the features of each specific example can be used altogether or selectively combined.

  The present invention can be used as an engine exhaust heat regeneration system.

  DESCRIPTION OF SYMBOLS 1 Engine, 1a Exhaust pipe, 2 Cooling water circuit, 2a Cooling water circulation flow path, 3 Cooling water pump, 4 Flow control valve, 5 Waste heat regeneration device, 6 Refrigerant pump, 7 1st heat exchanger, 8 2nd Heat exchanger, 9 expander, 10 condenser, 11 refrigerant circulation channel, 12 generator, 13 fan, 14 first heat exchanger, 15 second heat exchanger, 16 bypass channel, 17 flow rate adjusting valve, 18 Exhaust gas heat exchanger.

Claims (5)

A heat exchanger that heats and vaporizes the refrigerant with exhaust heat from the engine, an expander that expands the vaporized refrigerant to generate output, and a condenser that cools and condenses the refrigerant vapor discharged from the expander And an exhaust heat regeneration system including a refrigerant pump that circulates by pumping liquid refrigerant,
The heat exchanger is connected downstream of the flow of the refrigerant with respect to the first heat exchanger in which the refrigerant and the engine cooling water flow in parallel, and the first heat exchanger, and the refrigerant and the engine cooling water are in a counterflow. An engine exhaust heat regeneration system comprising: a second heat exchanger.   A flow rate adjusting valve is provided between the engine and the second heat exchanger and adjusts the flow rate of cooling water supplied from the engine to the second heat exchanger. Item 4. The engine exhaust heat regeneration system according to Item 1.   3. The engine exhaust heat regeneration according to claim 1, further comprising a bypass flow path having a flow rate adjusting valve that connects the engine to the first heat exchanger without passing through the second heat exchanger. system.   The engine exhaust heat regeneration system according to any one of claims 1 to 3, wherein the first heat exchanger and the second heat exchanger are combined into a single unit.   5. An exhaust gas heat exchanger connected between the second heat exchanger and the expander and provided in an exhaust pipe of the engine and heated by exhaust gas is provided. The engine exhaust heat regeneration system according to any one of the above.

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