JP4573912B1 - Engine exhaust heat recovery device - Google Patents

Abstract

To improve exhaust heat recovery efficiency by recovering latent heat of exhaust gas without adversely affecting engine durability and performance.
An engine cooling circuit that circulates engine cooling water between an engine cooling section that cools an engine and an exhaust heat recovery heat exchanger is provided. The exhaust heat recovery circuit includes an exhaust heat recovery circuit. The exhaust gas heat exchanger 19 for exchanging heat between the exhaust gas C of the engine 1 and the exhaust heat recovery medium A, and the engine cooling water B that has passed through the engine cooling unit 12 and the exhaust gas heat exchanger in order from the upstream side in the flow direction of the medium A An exhaust heat recovery heat exchanger 13 for exchanging heat with the exhaust heat recovery medium A that has passed through 19 is provided, and the temperature of the exhaust heat recovery medium A introduced into the exhaust gas heat exchanger 19 is below the dew point of the exhaust gas C of the engine 1. Is set.
[Selection] Figure 1

Description

  The present invention relates to an engine exhaust heat recovery apparatus including an exhaust heat recovery circuit for passing an exhaust heat recovery medium for recovering engine exhaust heat.

In a conventional exhaust heat recovery device for an engine, for example, in order to recover the exhaust heat from an engine used as a power source in a cogeneration device, between an engine cooling water and an exhaust heat recovery medium of an engine cooling circuit. An exhaust heat recovery heat exchanger that directly exchanges heat is provided in the exhaust heat recovery circuit. The engine cooling circuit includes an exhaust gas heat exchanger that exchanges heat between the engine cooling water and the exhaust gas of the engine, and an engine cooling unit that cools the engine with the engine cooling water that has passed through the exhaust gas heat exchanger, The exhaust heat of the engine is recovered by the engine cooling water in the exhaust gas heat exchanger and the engine cooling section, and the exhaust heat recovery medium such as the engine cooling water having the recovered exhaust heat and the hot water of the hot water storage tank is recovered. The exhaust heat of the engine is directly recovered by the exhaust heat recovery medium by exchanging heat with the vessel (see, for example, Patent Document 1).
In the apparatus described in Patent Document 1, the latent heat of exhaust gas is recovered by setting the temperature of engine cooling water introduced into the exhaust gas heat exchanger to be lower than the dew point of the exhaust gas of the engine subjected to heat exchange. , Improving the efficiency of exhaust heat recovery.

Japanese Patent No. 3767785

In the apparatus described in Patent Document 1, the temperature of the engine cooling water introduced into the exhaust gas heat exchanger is set low in order to recover the latent heat of the exhaust gas. The temperature of the engine coolant introduced into the cooling unit is also lowered. For example, in order to use the recovered exhaust heat for hot water supply or heating, the engine coolant temperature at the engine outlet is preferably high (for example, about 80 ° C.). Therefore, in the apparatus described in Patent Document 1, it is required that the inlet temperature to the exhaust gas heat exchanger be made lower than the dew point of the exhaust gas for the engine cooling water, and the temperature at the engine outlet should be increased. Desired. However, since there is a limit to the amount of heat that can be recovered by the engine cooling water in the exhaust gas heat exchanger and the engine cooling section, in order to satisfy both requirements, the circulation flow rate of the engine cooling water is reduced and the exhaust gas heat is reduced. There is no choice but to increase the temperature difference between the engine cooling water at the inlet to the exchanger and the engine outlet. As a result, the temperature difference between the engine cooling water at the engine inlet and the engine outlet increases, so the temperature of the engine cooling water at the engine inlet decreases, and the temperature of the engine cooling water introduced into the engine cooling section is low. It becomes.
Thus, when the temperature of the engine coolant introduced into the engine cooling unit is lowered, the moisture in the combustion gas mixed into the crankcase from the combustion chamber is likely to condense. When the condensed water is mixed with the engine oil and stirred, the engine oil is emulsified to form mayonnaise sludge, the lubrication performance is significantly deteriorated, and the engine durability is problematic. In addition, the temperature gradient between the engine combustion chamber and the engine cooling section is increased, the thermal stress on the material is increased, and there is a problem in durability. In addition, when the engine coolant is introduced into the engine oil cooler and then introduced into the exhaust gas heat exchanger, the engine coolant introduced into the oil cooler has a low temperature. Viscosity increases, leading to poor lubrication performance and reduced engine efficiency.

  The present invention has been made paying attention to such a point, and the object thereof is to improve the exhaust heat recovery efficiency by recovering the latent heat of the exhaust gas without adversely affecting the durability and performance of the engine. It is in providing an engine exhaust heat recovery device.

To achieve this object, the engine exhaust heat recovery device according to the present invention is characterized in that the exhaust heat recovery of the engine is provided with an exhaust heat recovery circuit for passing an exhaust heat recovery medium for recovering the exhaust heat of the engine. In the device
An engine cooling circuit that circulates engine cooling water between an engine cooling unit that cools the engine and an exhaust heat recovery heat exchanger; and the exhaust heat recovery circuit includes an upstream of a flow direction of the exhaust heat recovery medium The exhaust gas heat exchanger for exchanging heat between the exhaust gas of the engine and the exhaust heat recovery medium, the engine cooling water that has passed through the engine cooling unit, and the exhaust heat recovery medium that has passed through the exhaust gas heat exchanger are sequentially heated from the side. The exhaust heat recovery heat exchanger to be replaced is provided, the temperature of the exhaust heat recovery medium to be introduced into the exhaust gas heat exchanger is set below the dew point of the exhaust gas of the engine ,
A power generator driven by the engine and power generated by the power generator can be supplied to a power load, and surplus power that is a surplus of the power generated by the power generator with respect to the power load can be converted into heat. And an electric power supply means that can be supplied to the electric heater, wherein the electric heater is arranged to freely heat the exhaust heat recovery medium that has passed through the exhaust heat recovery heat exchanger in the exhaust heat recovery circuit. .

According to this characteristic configuration, in the exhaust heat recovery circuit, the exhaust heat recovery medium is introduced into the exhaust gas heat exchanger and heated by the exhaust gas, and the exhaust heat recovery medium that has passed through the exhaust gas heat exchanger is the exhaust heat recovery heat exchanger. The exhaust heat of the engine is recovered by the exhaust gas heat exchanger and the exhaust heat recovery heat exchanger. Since the temperature of the exhaust heat recovery medium introduced into the exhaust gas heat exchanger is set to be equal to or lower than the dew point of the exhaust gas, the exhaust gas latent heat of the exhaust gas can also be recovered in the exhaust gas heat exchanger. Further, in the engine cooling circuit, the exhaust heat recovery medium introduced into the exhaust heat recovery heat exchanger can be heated by increasing the temperature of the engine coolant at the engine outlet to the inlet temperature to the exhaust heat recovery heat exchanger. Can be high temperature. Therefore, according to the present invention, it is only required to raise the engine coolant temperature at the engine outlet for the engine coolant, so that it is not necessary to reduce the circulation flow rate of the engine coolant as in Patent Document 1 described above. The temperature difference between the engine cooling water at the engine inlet and the engine outlet does not increase, and the engine cooling water temperature at the engine inlet can be prevented from decreasing. And by making the engine cooling water temperature of an engine exit high, for example, it can be made suitable also when using the collect | recovered waste heat for hot water supply or heating. From the above, it is possible to recover the exhaust heat latent heat as exhaust heat of the engine without adversely affecting the durability and performance of the engine by preventing excessive temperature drop of the engine coolant introduced into the engine cooling section. An exhaust heat recovery device for an engine that can improve exhaust heat recovery efficiency can be realized.
Furthermore, according to this characteristic configuration, when surplus power is generated, the surplus power can be converted into heat by the electric heater, and the exhaust heat recovery medium can be heated by the converted heat. Therefore, in addition to the exhaust heat of the engine, surplus power can be recovered as heat, and heat recovery efficiency can be improved. Moreover, since the electric heater heats the exhaust heat recovery medium that has passed through the exhaust heat recovery heat exchanger in the exhaust heat recovery circuit, the heat generated by the electric heater can be directly applied to the exhaust heat recovery medium. It is possible to efficiently supply the heat generated in the exhaust heat recovery medium.

  According to a further characteristic configuration of the exhaust heat recovery apparatus for an engine according to the present invention, the engine has an excess air ratio of an air-fuel mixture combusted in a combustion chamber within a stoichiometric range, and a three-way catalyst is provided in the exhaust gas heat exchanger. Or a three-way catalyst is disposed upstream of the exhaust gas heat exchanger in the exhaust gas flow direction of the engine.

  According to this configuration, the excess air ratio of the air-fuel mixture is set within the stoichiometric range and the engine is stoichiometrically combusted. Therefore, it is disposed in the exhaust gas heat exchanger or upstream of the exhaust gas heat exchanger. In addition, the three-way catalyst can simultaneously remove the three substances of hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxide (NOx). As a result, even if the exhaust gas from which the three substances of hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxide (NOx) are removed in the exhaust gas heat exchanger is condensed and the latent heat of the exhaust gas is recovered, the exhaust gas There is no problem of corrosion or the like in the condensed water obtained by condensing water, which is useful.

A further characteristic configuration of the exhaust heat recovery device for an engine of the present invention is as follows:
The exhaust heat recovery circuit has an upstream end between the exhaust gas heat exchanger and the exhaust heat recovery heat exchanger and a downstream end downstream of the exhaust heat recovery heat exchanger. With a bypass to bypass the heat exchanger,
A flow distribution means is provided that distributes and guides the flow rate of the exhaust heat recovery medium flowing through the exhaust heat recovery circuit to one or both of the exhaust heat recovery heat exchanger and the bypass passage. It is in.

As described so far, in the present invention, the exhaust heat recovery medium flowing through the exhaust heat recovery circuit recovers exhaust heat of the exhaust gas with the exhaust gas heat exchanger and the engine with the exhaust heat recovery heat exchanger. The exhaust heat of the cooling water is recovered to improve the exhaust heat recovery efficiency.
When the engine coolant circulates through the engine cooling circuit and its temperature is higher than the temperature of the exhaust heat recovery medium introduced into the exhaust heat recovery heat exchanger, the engine coolant is supplied to the exhaust heat recovery heat exchanger. Then, the engine is cooled in such a manner that the heat is recovered in the exhaust heat recovery medium and the exhaust heat of the engine is recovered in the engine cooling unit.
Here, when the engine is warming up at a low temperature and it is desired to shorten the warm-up time of the engine, it is necessary to prevent the engine cooling water from collecting the engine exhaust heat from the engine cooling unit. On the other hand, in order to suppress a decrease in exhaust heat recovery efficiency, it is desired to appropriately recover exhaust heat of exhaust gas even during the warm-up operation.
According to the above characteristic configuration, when the engine is warmed up at a low temperature and it is desired to shorten the warm-up time of the engine, the flow rate distribution means includes the exhaust heat recovery medium flowing through the exhaust heat recovery circuit. By reducing the flow rate of the exhaust heat recovery medium that is distributed and guided to the exhaust heat recovery heat exchanger, the amount of engine cooling water recovered by the exhaust heat recovery heat exchanger is reduced to the flow rate of the exhaust heat recovery medium. It can be reduced by the reduction amount. As a result, the amount of heat of the engine cooling water whose recovery is suppressed by the exhaust heat recovery heat exchanger is used for engine warm-up, giving priority to engine warm-up and shortening the warm-up time. be able to.
Further, as described above, even if the flow distribution means distributes the flow rate of the exhaust heat recovery medium between the exhaust heat recovery heat exchanger side and the bypass path side, the exhaust heat recovery that flows through the exhaust gas heat exchanger. Since the flow rate of the medium does not change, the exhaust heat of the exhaust gas can be appropriately recovered by the exhaust heat recovery medium in the exhaust gas heat exchanger.
As described above, during engine warm-up operation, it is possible to realize an engine exhaust heat recovery apparatus that can appropriately recover exhaust gas exhaust heat and suppress a decrease in exhaust heat recovery efficiency while shortening the warm-up time. .

A further characteristic configuration of the exhaust heat recovery device for an engine of the present invention is as follows:
The flow distribution means is a three-way valve;
The three-way valve includes a first flow state in which the flow state of the exhaust heat recovery medium flowing through the exhaust heat recovery circuit is introduced into the exhaust heat recovery heat exchanger, and the bypass of the exhaust heat recovery medium It is in the point which can be switched to the 2nd flow state made to flow through a path.

According to the above characteristic configuration, the first flow state in which the exhaust heat recovery medium flowing through the exhaust heat recovery circuit is introduced into the exhaust heat recovery heat exchanger by the relatively simple configuration of providing a three-way valve, and the bypass Switching to the second flow state for flowing through the road can be realized.
Thereby, for example, when the engine is in a warm-up operation state at a low temperature, when the engine warm-up is prioritized and the engine warm-up time is to be shortened, the exhaust heat recovery medium flowing through the exhaust heat recovery circuit is The open / close state of the three-way valve is switched so that the second flow state that flows through the bypass path is set so that the heat quantity of the engine cooling water by the exhaust heat recovery heat exchanger is not recovered. Thereby, it is possible to prevent the heat quantity of the engine cooling water from being recovered by the exhaust heat recovery heat exchanger. As a result, the heat quantity of the engine cooling water, which is prevented from being recovered by the exhaust heat recovery heat exchanger, is used for warming up the engine, and the warming up time can be shortened by giving priority to warming up the engine. .
On the other hand, even when the flow state of the exhaust heat recovery medium flowing through the exhaust heat recovery circuit is changed to the second flow state passing through the bypass path, it is introduced into the exhaust gas heat exchanger. Since the flow rate of the exhaust heat recovery medium does not fluctuate, the exhaust heat of the exhaust gas is appropriately recovered by the exhaust heat recovery medium by the exhaust gas heat exchanger, and the reduction of the exhaust heat recovery efficiency can be suppressed.
When the engine is in a steady operation state other than the warm-up operation state, the exhaust heat recovery medium flowing through the exhaust heat recovery circuit is used as an exhaust heat recovery heat exchanger in order to appropriately recover the exhaust heat of the engine. By switching the open / close state of the three-way valve so as to be in the first flowing state, the exhaust heat recovery heat exchanger can appropriately recover the exhaust heat of the engine cooling water by the exhaust heat recovery medium.

A further characteristic configuration of the exhaust heat recovery device for an engine of the present invention is as follows:
The temperature of the engine oil, the temperature of the engine cooling water between the engine cooling part of the engine cooling circuit and the exhaust heat recovery heat exchanger, and the heat exchanged with the exhaust gas in the exhaust gas heat exchanger A temperature measuring means for measuring at least one of the temperatures of the exhaust heat recovery medium, an operating state determining means for determining the operating state of the engine based on the measured temperature of the temperature measuring means,
When the operation state determination means determines that the engine operation state is a warm-up operation state, the three-way valve is opened and closed so that the flow state of the exhaust heat recovery medium is the second flow state. Switching control means for switching the state.

The temperature of the engine oil, the temperature of the engine cooling water between the engine cooling part of the engine cooling circuit and the exhaust heat recovery heat exchanger, and the temperature of the exhaust heat recovery medium after exchanging heat with the exhaust gas in the exhaust gas heat exchanger are as follows: It changes with the operating state of the engine. Specifically, when the engine is in a warm-up operation state, those temperatures are relatively low, and when the engine is in a steady operation state other than the warm-up operation state, these temperatures are relatively high. It is.
That is, according to the above characteristic configuration, the operating state determining means is based on the measured temperature of the temperature measuring means for measuring the temperature of the engine oil, the temperature of the engine cooling water, and the temperature of the exhaust heat recovery medium. It is possible to determine whether or not the operation state is a warm-up operation state. When the operation state determination means determines that the engine operation state is the warm-up operation state, the switching control means controls the open / close state of the three-way valve to change the flow state of the exhaust heat recovery medium to the first state. Switch to the two-flow state. Thereby, the flow state of the exhaust heat recovery medium flowing through the exhaust heat recovery circuit can be appropriately switched in a state according to the operation state of the engine, and particularly when the engine is in a warm-up operation state. The engine warm-up can be prioritized and the warm-up time can be shortened by setting the exhaust heat recovery medium flowing through the exhaust heat recovery circuit to the second flow state in which the exhaust heat recovery medium flows through the bypass path.

A further characteristic configuration of the exhaust heat recovery device for an engine of the present invention is as follows:
The three-way valve includes a temperature-sensitive three-way valve that senses the temperature of the exhaust heat recovery medium and switches between open and closed states, and the temperature-sensitive three-way valve exchanges heat with the exhaust gas in the exhaust gas heat exchanger. When the temperature of the exhaust heat recovery medium after the above is higher than a predetermined value, the first flow state is set, and when the temperature is equal to or lower than the predetermined value, the second flow state is set.

  According to the above characteristic configuration, the temperature-sensitive three-way valve directly detects the temperature of the exhaust heat recovery medium after exchanging heat with the exhaust gas in the exhaust gas heat exchanger, and flows through the exhaust heat recovery circuit. Since the exhaust heat recovery medium to be switched is switched between the first flow state and the second flow state, it is necessary to apply electrical control from the other while the switching follows the operating state of the engine. It can be carried out independently.

It is a figure showing a schematic structure of a cogeneration system showing a 1st embodiment of the present invention. It is a figure which shows schematic structure of the cogeneration system which shows 2nd Embodiment of this invention.

A first embodiment of a cogeneration system to which an exhaust heat recovery apparatus for an engine according to the present invention is adapted will be described with reference to the drawings.
As shown in FIG. 1, the cogeneration system includes a power generation device 2 that generates electric power that is driven by the engine 1 and that is supplied to the electric power load 3, and an exhaust heat recovery medium A that recovers exhaust heat of the engine 1. And an exhaust heat recovery circuit 4 that is allowed to flow. The heat recovered by the exhaust heat recovery medium A of the exhaust heat recovery circuit 4 is configured to be freely supplied to the heat load 5.

  On the output side of the power generation device 2, an inverter 6 for grid connection is provided, and the inverter 6 sets the output power of the power generation device 2 to the same voltage and the same frequency as the power supplied from the commercial system 7. It is configured. The commercial system 7 is electrically connected to a power load 3 such as a television, a refrigerator, or a washing machine via a power supply line 8.

  The inverter 6 is electrically connected to the power supply line 8 via the cogeneration power supply line 9, and the generated power from the power generator 2 can be supplied to the power load 3 via the inverter 6 and the cogeneration power supply line 9. It is configured. Although not shown, the power supply line 8 is provided with power load measuring means for measuring the load power of the power load 3, and this power load measuring means generates a reverse power flow in the current flowing through the power supply line 8. It is configured to detect whether or not. And the electric power supplied to the electric power supply line 8 from the electric power generating apparatus 2 is controlled by the inverter 6 so that a reverse power flow does not arise, and the surplus electric power of the generated electric power is converted into the electric heater 10 which can convert the surplus electric power into heat freely. It is configured to be supplied. As a result, the power supply means includes the inverter 6 and the cogeneration power supply line 9.

  The electric heater 10 is provided so that the exhaust heat recovery medium A flowing through the exhaust heat recovery circuit 4 can be freely heated. The electric heater 10 increases the amount of heating of the exhaust heat recovery medium A according to the amount of surplus power so that the power consumption increases and the amount of heating of the exhaust heat recovery medium A increases as the amount of surplus power increases. It is configured to be adjustable.

  The operation of the engine 1 is controlled by the control device 11. The engine 1 has a configuration similar to that of a normal four-cycle engine. After the air-fuel mixture of fuel gas (for example, natural gas) and air is sucked into the combustion chamber, the air-fuel mixture is compressed in the combustion chamber. The air-fuel mixture is ignited and expanded in the combustion chamber, and the exhaust gas C generated by the combustion is exhausted to the exhaust passage 22. Although not shown, the exhaust passage 22 of the engine 1 is provided with an oxygen sensor for detecting the oxygen concentration of the exhaust gas C. The control device 11 adjusts the supply amount of the fuel gas so that the oxygen concentration of the exhaust gas C detected by the oxygen sensor becomes substantially zero. Thus, in the engine 1, the excess air ratio of the air-fuel mixture supplied to the combustion chamber is set within a stoichiometric range of about 1.0. Here, the excess air ratio indicates the air-fuel ratio of the air-fuel mixture divided by the stoichiometric air-fuel ratio.

  As a circuit for circulating the engine cooling water B for cooling the engine 1, an engine cooling circuit 14 for circulating the engine cooling water B between the engine cooling unit 12 and the exhaust heat recovery heat exchanger 13 is provided. The engine cooling unit 12 is configured to cool the engine 1 by allowing the engine cooling water B to flow through, for example, a cylinder head or a cylinder block. The engine cooling circuit 14 includes an engine cooling unit 12, an exhaust heat recovery heat exchanger 13, an expansion tank 15 that can store the engine cooling water B, and an engine cooling water circulation pump in order from the upstream side in the flow direction of the engine cooling water B. 16 is provided.

  The exhaust heat recovery circuit 4 uses the hot water in the hot water storage tank 17 as the exhaust heat recovery medium A, passes the exhaust heat recovery medium A taken out from the hot water storage tank 17 to recover the exhaust heat of the engine 1, and has the exhaust heat. The exhaust heat recovery medium A is returned to the hot water storage tank 17. In the exhaust heat recovery circuit 4, the exhaust heat recovery medium circulating pump 18, the exhaust gas C of the engine 1 and the exhaust heat recovery medium A are subjected to heat exchange in order from the upstream side in the flow direction of the exhaust heat recovery medium A. A heat exchanger 19, an exhaust heat recovery heat exchanger 13 for exchanging heat between the engine coolant B and the exhaust heat recovery medium A, and an electric heater 10 are provided.

  The exhaust gas heat exchanger 19 exchanges heat between the exhaust gas C exhausted from the engine 1 to the exhaust path 22 and the exhaust heat recovery medium A taken out from the hot water storage tank 17. The exhaust gas heat exchanger 19 is, for example, a catalyst-integrated heat exchanger in which a three-way catalyst 23 formed by supporting a noble metal component such as platinum, palladium, and rhodium on an inorganic carrier such as alumina is integrally disposed. Configured. As described above, the engine 1 is arranged integrally with the exhaust gas heat exchanger 19 because the excess air ratio of the air-fuel mixture supplied to the combustion chamber is set within a stoichiometric range of about 1.0. The three-way catalyst 23 can remove three substances of hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxide (NOx) from the exhaust gas C at the same time.

  The exhaust heat recovery circuit 4 heats the exhaust heat recovery medium A with the exhaust gas C of the engine 1 in the exhaust gas heat exchanger 19, and then converts the exhaust heat recovery medium A into the engine coolant B that has passed through the engine cooling unit 12 in the exhaust heat recovery heat exchanger 13. The exhaust heat recovery medium A is further heated to raise the temperature of the exhaust heat recovery medium A to a desired temperature (for example, 75 ° C.), and the exhaust heat recovery medium A at the desired temperature is returned to the upper part of the hot water storage tank 17. Further, in the exhaust heat recovery circuit 4, the exhaust heat recovery medium A that has passed through the exhaust heat recovery heat exchanger 13 can be freely heated by the electric heater 10, and surplus power is converted in addition to the exhaust heat of the engine 1. The exhaust heat recovery medium A is also configured to be freely heated by heat. The hot water storage tank 17 is configured to store hot water in a state where temperature stratification is formed, and the exhaust heat recovery circuit 4 is heated by the exhaust heat of the engine 1 and heated to a desired temperature to recover the exhaust heat. The medium A is configured to store hot water in the hot water storage tank 17.

  The hot water storage tank 17 has a water supply path 20 for supplying water to the hot water storage tank 17, and a heat load supply for supplying the high-temperature exhaust heat recovery medium A stored in the hot water storage tank 17 to the heat load 5 such as a floor heating device or a bathroom heating device. A path 21 is provided. Thus, the exhaust heat recovery medium A having the exhaust heat of the recovered engine 1 is configured to be freely supplied to the heat load 5 through the heat load supply path 21.

  The control device 11 is configured to control the operation of the engine 1 and the like by executing a predetermined computer program. For example, for the required power amount at the power load 3 and the required heat amount at the heat load 5, the control device 11 can predict the future required power amount and the required heat amount based on the past required power amount and the past required heat amount. It is configured. The control device 11 controls the operation of the engine 1 according to the predicted future required power amount or required heat amount in order to cover the required power amount at the power load 3 or the required heat amount at the heat load 5. It is configured. The control device 11 is configured to recover the exhaust heat of the engine 1 by the exhaust heat recovery medium A by operating the engine cooling water circulation pump 16 and the exhaust heat recovery medium circulation pump 18 when the engine 1 is operated. ing.

  By operating the exhaust heat recovery medium circulation pump 18, the exhaust heat recovery medium A taken out from the bottom of the hot water storage tank 17 is passed through the exhaust heat recovery circuit 4. The exhaust heat recovery medium A passes through the exhaust gas heat exchanger 19, the exhaust heat recovery heat exchanger 13, and the electric heater 10 in this order, and the exhaust heat recovery medium A that has passed through the electric heater 10 is returned to the upper part of the hot water storage tank 17. Exhaust gas C flowing through the exhaust passage 22 is introduced into the exhaust gas heat exchanger 19, and the exhaust heat recovery medium A is heated by the exhaust gas C. Since the hot water storage tank 17 stores the exhaust heat recovery medium A in a state where temperature stratification is formed, the low temperature exhaust heat recovery medium A exists in the lower part of the hot water storage tank 17. As a result, the amount of hot water stored in the hot water storage tank 17 is exhausted from the bottom of the hot water storage tank 17 until the amount of hot water stored is full (a state where substantially the entire amount of the exhaust heat recovery medium A stored in the hot water storage tank 17 is at a desired temperature). The heat recovery medium A becomes a low temperature. Therefore, the exhaust heat recovery circuit 4 introduces the low-temperature exhaust heat recovery medium A taken out from the bottom of the hot water storage tank 17 into the exhaust gas heat exchanger 19, and the exhaust heat recovery medium A introduced into the exhaust gas heat exchanger 19. The temperature is set to a temperature (for example, about 20 ° C.) that is lower than the dew point (for example, 60 ° C.) of the exhaust gas C of the engine 1. Thereby, in the exhaust gas heat exchanger 19, the latent heat of the exhaust gas C can be recovered by the exhaust heat recovery medium A, and the exhaust heat recovery efficiency can be improved.

  In the engine cooling circuit 14, the engine cooling water B is circulated between the engine cooling unit 12 and the exhaust heat recovery heat exchanger 13 by the operation of the engine cooling water circulation pump 16. In the exhaust heat recovery heat exchanger 13, engine cooling water B heated by cooling the engine 1 in the engine cooling unit 12 is introduced, and the exhaust heat recovery medium A that has passed through the exhaust gas heat exchanger 19 is introduced. The exhaust heat recovery medium A is introduced and heated by the engine coolant B.

  As described above, the control device 11 controls the operation of the engine 1 according to the predicted future required power amount or required heat amount in order to cover the required power amount at the power load 3 or the required heat amount at the heat load 5. However, for example, when the so-called main heat operation is performed in which the operation of the engine 1 is controlled according to the predicted future required heat amount in order to cover the required heat amount at the heat load 5, Surplus power that is a surplus for the load 3 is generated. At this time, surplus power is supplied to the electric heater 10 by the inverter 6. As a result, the electric heater 10 heats the exhaust heat recovery medium A that has passed through the exhaust heat recovery heat exchanger 13 with surplus power, and in addition to recovering the exhaust heat of the engine 1, It is configured to be able to recover the converted heat.

  The control device 11 is configured such that the circulation amount of the engine coolant B in the engine cooling circuit 14 is adjustable by adjusting the rotational speed of the engine coolant circulation pump 16. Further, the control device 11 is configured to adjust the amount of circulation of the exhaust heat recovery medium A in the exhaust heat recovery circuit 4 by adjusting the rotational speed of the exhaust heat recovery medium circulation pump 18. Thereby, by adjusting the circulation amount of the engine cooling water B in the engine cooling circuit 14 and the circulation amount of the exhaust heat recovery medium A in the exhaust heat recovery circuit 4, the exhaust heat recovery medium A that has passed through the exhaust gas heat exchanger 19 is adjusted. The temperature and the temperature of the exhaust heat recovery medium A and the engine coolant B that have passed through the exhaust heat recovery heat exchanger 13 are adjustable.

Hereinafter, the exhaust heat recovery device for an engine according to the present invention will be described while illustrating the temperatures of the exhaust heat recovery medium A, the engine cooling water B, and the exhaust gas C.
For example, the temperature of the exhaust gas C exhausted from the engine 1 that performs stoichiometric combustion is 500 to 600 ° C., and the exhaust gas C of 500 to 600 ° C. is introduced into the exhaust gas heat exchanger 19. On the other hand, when the hot water storage tank 17 hardly stores the exhaust heat recovery medium A at the desired temperature, the temperature of the exhaust heat recovery medium A taken out from the bottom of the hot water storage tank 17 is about 20 ° C. below the dew point of the exhaust gas C. The exhaust heat recovery medium A of about 20 ° C. is introduced into the exhaust gas heat exchanger 19. The exhaust gas heat exchanger 19 also recovers the latent heat of the exhaust gas C, and the temperature of the exhaust gas C that has passed through the exhaust gas heat exchanger 19 decreases to about 25 ° C. On the other hand, the temperature of the exhaust heat recovery medium A that has passed through the exhaust gas heat exchanger 19 is raised to about 60 ° C., and the exhaust heat recovery medium A at about 60 ° C. is introduced into the exhaust heat recovery heat exchanger 13. The engine cooling water B that has passed through the engine cooling unit 12 is raised to about 80 ° C., and the engine cooling water B at about 80 ° C. is introduced into the exhaust heat recovery heat exchanger 13. The temperature of the exhaust heat recovery medium A that has passed through the exhaust heat recovery heat exchanger 13 is raised to about 75 ° C., and the exhaust heat recovery medium A of about 75 ° C. is supplied to the upper part of the hot water storage tank 17 and stored. On the other hand, the temperature of the engine coolant B that has passed through the exhaust heat recovery heat exchanger 13 is reduced to about 78 ° C., and the engine coolant B at about 78 ° C. is introduced into the engine cooling unit 12.

The exhaust heat recovery medium A introduced into the exhaust heat recovery heat exchanger 13 has already recovered the latent heat of the exhaust gas C in the exhaust gas heat exchanger 19 and has reached a relatively high temperature (for example, about 60 ° C.). Since it is the medium A, the temperature of the engine coolant B that has passed through the exhaust heat recovery heat exchanger 13 can be prevented from becoming excessively low due to a relatively high temperature (for example, about 78 ° C.). Therefore, the engine cooling water B introduced into the engine cooling unit 12 can be prevented from becoming excessively low in temperature, and the durability and performance of the engine 1 can be prevented from being adversely affected.
Regarding the temperature of the engine coolant B introduced into the engine cooling section 12, the amount of the engine coolant B that has passed through the exhaust heat recovery heat exchanger 13 is adjusted by adjusting the circulation amount of the engine coolant B in the engine cooling circuit 14. It can be adjusted by adjusting the temperature. And the control apparatus 11 becomes the temperature range (for example, temperature range of 65 to 85 degreeC) in which the temperature of the engine cooling water B introduce | transduced into the engine cooling part 12 does not have a bad influence on the durability and performance of the engine 1. As described above, the rotational speed of the engine coolant circulation pump 16 is controlled to adjust the circulation amount of the engine coolant B in the engine cooling circuit 14.

  Next, a second embodiment of the cogeneration system to which the exhaust heat recovery apparatus for the engine 1 according to the present invention is adapted will be described with reference to FIG. In the following description of the second embodiment, the same components as those in the first embodiment will be denoted by the same reference numerals, and the description thereof may be omitted. In the cogeneration system according to the second embodiment, when the engine 1 is in a warm-up operation state, it is intended to suppress a reduction in exhaust heat recovery efficiency while shortening the warm-up time of the engine 1. Is.

In this cogeneration system, the exhaust heat recovery circuit 4 has an upstream end (branch portion) between the exhaust gas heat exchanger 19 and the exhaust heat recovery heat exchanger 13 and at the downstream side of the exhaust heat recovery heat exchanger 13 ( A bypass passage 30 is provided on the upstream side of the electric heater 10 and on the upstream side of the hot water storage tank 17) to bypass the exhaust heat recovery heat exchanger 13 with a downstream end (merging portion). A three-way valve 31 (an example of a flow distribution means) that distributes and guides the flow rate of the exhaust heat recovery medium A flowing to the exhaust heat recovery heat exchanger 13 and the bypass passage 30 is provided at the upstream end of the bypass passage 30. Yes.
More specifically, the three-way valve 31 is composed of an electromagnetic valve whose opening / closing state can be controlled by a control signal from the control device 11 by switching its opening / closing state, and exhaust heat that circulates in the exhaust heat recovery circuit 4. As for the flow state of the recovery medium A, a first flow state (a state indicated by a dotted line in FIG. 2) to be introduced into the exhaust heat recovery heat exchanger 13 and a second flow state (FIG. 2) to flow through the bypass passage 30. In a state indicated by a two-dot chain line).

As described above, the cogeneration system of the second embodiment determines whether or not the engine 1 is in the warm-up state in order to shorten the warm-up time when the engine 1 is in the warm-up operation state. It has a function to do. Hereinafter, a configuration for exerting the function will be described.
The engine cooling circuit 14 is provided with a temperature sensor 32 (temperature measuring means) that measures the temperature of the engine coolant B between the engine cooling unit 12 and the exhaust heat recovery heat exchanger 13. The measured temperature of fluctuates with the operating state of the engine 1. Specifically, when the operation state of the engine 1 is a warm-up operation state, the temperature is relatively low (for example, a temperature of 65 ° C. or less), and when the engine 1 is in a steady operation state other than the warm-up operation state, It becomes about high temperature (for example, temperature higher than 65 degreeC).
Based on the temperature measured by the temperature sensor 32, the control device 11 functions as an operation state determination unit that determines the operation state of the engine 1. Specifically, the control device 11 compares the measured temperature of the engine coolant B measured by the temperature sensor 32 with a warm-up operation determination threshold (for example, 65 ° C.) in a state where the engine 1 is activated. When the measured temperature of the engine coolant B is equal to or lower than the warm-up operation determination threshold, it is determined that the engine 1 is in the warm-up operation state, and the measured temperature of the engine coolant B is higher than the warm-up operation determination threshold. When it is temperature, it is determined that the engine 1 is in a steady operation state other than the warm-up operation state.

Hereinafter, description will be added regarding switching of the flow state of the exhaust heat recovery medium A based on the operation state of the engine 1. In the following description, it is assumed that the engine 1 is in a state after being activated.
The control device 11 determines that the engine 1 is in the warm-up operation state when the measured temperature of the engine coolant B measured by the temperature sensor 32 is a temperature equal to or lower than the warm-up operation determination threshold (for example, 65 ° C.). The flow state of the exhaust heat recovery medium A flowing through the exhaust heat recovery circuit 4 is changed to a second flow state (state indicated by a two-dot chain line in FIG. 2) flowing through the bypass passage 30. The open / close state of the three-way valve 31 is switched. As a result, the exhaust heat recovery medium A is not passed through the exhaust heat recovery heat exchanger 13. As a result, the engine cooling circuit 14 prevents the heat quantity of the engine cooling water B circulating between the engine cooling unit 12 and the exhaust heat recovery heat exchanger 13 from being recovered by the exhaust heat recovery heat exchanger 13. it can. As a result, the amount of heat exhausted from the engine 1 can be suppressed while the amount of heat that the engine cooling water B is prevented from being recovered by the exhaust heat recovery heat exchanger 13 is used to warm up the engine 1, and You can prioritize the machine and shorten its warm-up time.
As described above, the control device 11 changes the flow state of the exhaust heat recovery medium A flowing through the exhaust heat recovery circuit 4 to the second flow state (two points in FIG. 2). Even if the open / close state of the three-way valve 31 is controlled as shown by the chain line), the flow rate of the exhaust heat recovery medium A introduced into the exhaust gas heat exchanger 19 does not fluctuate. The heat is appropriately recovered by the exhaust heat recovery medium A in the exhaust gas heat exchanger 19, and the reduction of the exhaust heat recovery efficiency can be suppressed.

On the other hand, when the measured temperature of the engine coolant B measured by the temperature sensor 32 is higher than the warm-up operation determination threshold (for example, 65 ° C.), the control device 11 is in a steady operation state other than the warm-up operation state. And the flow state of the exhaust heat recovery medium A flowing through the exhaust heat recovery circuit 4 is a first flow state introduced into the exhaust heat recovery heat exchanger 13 (indicated by a dotted line in FIG. 2). The open / close state of the three-way valve 31 is switched so that the state shown in FIG. That is, the control device 11 sets the circuit state of the exhaust heat recovery circuit 4 to the same state as the circuit state in the cogeneration system of the first embodiment, and the exhaust heat recovery medium A flowing through the exhaust heat recovery circuit 4 The exhaust heat recovery heat exchanger 13 properly recovers the exhaust heat of the engine cooling water B, while the exhaust gas heat exchanger 19 also appropriately recovers the exhaust heat of the exhaust gas C, resulting in high exhaust heat recovery efficiency. Can be maintained.
As described above, the control device 11 allows the exhaust heat recovery medium A flowing through the exhaust heat recovery circuit 4 to flow through the bypass passage 30 when the operation state of the engine 1 is the warm-up operation state. Function as switching control means for switching to the second flow state (the state indicated by the two-dot chain line in FIG. 2).

[Another embodiment]
(1) In the first and second embodiments, the engine cooling circuit 14 is provided with the oil cooler of the engine 1 upstream of the engine cooling unit 12 in the flow direction of the engine cooling water B. The engine cooling water B that has passed through the oil cooler after being introduced into the oil cooler can be introduced into the engine cooling unit 12.

(2) In the first embodiment, the engine 1 sets the excess air ratio of the air-fuel mixture supplied to the combustion chamber within the stoichiometric range of about 1.0. It can also be set within a lean range greater than .0.

(3) In the first and second embodiments, the exhaust heat recovery circuit 4 uses the hot water in the hot water storage tank 17 as the exhaust heat recovery medium A, and the exhaust gas heat exchanger 19, the exhaust heat recovery heat exchanger 13, and the electric heater 10. However, the exhaust heat recovery medium A is not limited to the hot water in the hot water storage tank 17, and other heat media can be applied.
Further, the exhaust heat recovery medium A is passed through the operation of the exhaust heat recovery medium circulation pump 18 provided in the exhaust heat recovery circuit 4. For example, the exhaust heat recovery is performed using the water pressure of the clean water in the water supply channel 20. The medium A can also be passed.

(4) In the first embodiment, the exhaust gas heat exchanger 19 is a catalyst-integrated heat exchanger in which the three-way catalyst 23 is integrally disposed, and the three-way catalyst 23 is disposed in the exhaust gas heat exchanger 19. However, the three-way catalyst 23 can also be arranged in the middle of the exhaust passage 22 upstream of the exhaust gas heat exchanger 19 in the flow direction of the exhaust gas C.

(5) In the second embodiment, the control device 11 passes the exhaust heat recovery medium A flowing through the exhaust heat recovery circuit 4 based on the temperature measured by the temperature sensor 32 that measures the temperature of the engine coolant B. The open / close state of the three-way valve 31 is controlled so that the flow state is switched between a first flow state (state indicated by a dotted line in FIG. 2) and a second flow state (state indicated by a two-dot chain line in FIG. 2). The configuration to do was shown.
However, even if the control device 11 controls the open / close state of the three-way valve 31 based on the temperature other than the engine coolant B as long as the temperature varies with the warm-up state of the engine 1, the function of the present invention is achieved. To perform well. For example, the open / close state of the three-way valve 31 can be controlled based on the temperature of the engine oil of the engine 1 or the like.

(6) In the second embodiment, the three-way valve 31 is an electric type controlled by the control device 11. For example, the three-way valve 31 may be constituted by a temperature-sensitive three-way valve that senses the temperature of the exhaust heat recovery medium A flowing through the exhaust heat recovery circuit 4 and switches its open / close state. The temperature-sensitive three-way valve is configured such that its open / closed state is autonomously switched in such a manner that the internal wax element expands and contracts with the temperature of the exhaust heat recovery medium A flowing therethrough. That is, by making the three-way valve 31 temperature-sensitive, a first flow state (state indicated by a dotted line in FIG. 2) in which the exhaust heat recovery medium A is introduced into the exhaust heat recovery heat exchanger 13, and a bypass path Based on the temperature of the exhaust heat recovery medium A flowing through the temperature-sensitive three-way valve, the second flow state (the state indicated by the two-dot chain line in FIG. 2) through which the exhaust heat recovery medium A flows through 30 is used. Can switch autonomously. When performing such independent switching, the temperature-sensitive three-way valve has a predetermined temperature at which the temperature of the exhaust heat recovery medium A reaching the valve is the temperature of the exhaust heat recovery medium A when the warm-up operation is completed. What is necessary is just to comprise so that it may become said 1st flow state when it is higher than a value (for example, 60 degreeC), and will become said 2nd flow state when below a predetermined value.

(7) In the second embodiment, the three-way valve 31 (an example of the flow distribution means) is provided at the upstream end (branch portion) of the bypass passage 30, but is separately provided at the downstream end (confluence portion) of the bypass passage 30. ) May be provided. Even in this case, the exhaust heat recovery medium A can be distributed and guided to the exhaust heat recovery heat exchanger 13 and the bypass passage 30.

  The present invention includes an exhaust heat recovery circuit for passing an exhaust heat recovery medium that recovers exhaust heat of the engine, and recovers exhaust heat latent heat without adversely affecting the durability and performance of the engine. It is applicable to various engine exhaust heat recovery devices that can increase efficiency.

DESCRIPTION OF SYMBOLS 1 Engine 2 Electric power generating apparatus 3 Electric power load 4 Waste heat recovery circuit 10 Electric heater 12 Engine cooling part 13 Waste heat recovery heat exchanger 14 Engine cooling circuit 19 Exhaust gas heat exchanger 30 Bypass path 31 Three-way valve (an example of switching means)
32 Temperature sensor (example of temperature measurement means)
A Waste heat recovery medium B Engine cooling water C Exhaust gas

Claims (6)

In an engine exhaust heat recovery apparatus having an exhaust heat recovery circuit for passing an exhaust heat recovery medium for recovering engine exhaust heat,
An engine cooling circuit that circulates engine cooling water between an engine cooling unit that cools the engine and an exhaust heat recovery heat exchanger; and the exhaust heat recovery circuit includes an upstream of a flow direction of the exhaust heat recovery medium The exhaust gas heat exchanger for exchanging heat between the exhaust gas of the engine and the exhaust heat recovery medium, the engine cooling water that has passed through the engine cooling unit, and the exhaust heat recovery medium that has passed through the exhaust gas heat exchanger are sequentially heated from the side. The exhaust heat recovery heat exchanger to be replaced is provided, the temperature of the exhaust heat recovery medium to be introduced into the exhaust gas heat exchanger is set below the dew point of the exhaust gas of the engine ,
A power generator driven by the engine and power generated by the power generator can be supplied to a power load, and surplus power that is a surplus of the power generated by the power generator with respect to the power load can be converted into heat. And an electric power supply means that can be supplied to the electric heater, wherein the electric heater is an exhaust of an engine in which the exhaust heat recovery medium that has passed through the exhaust heat recovery heat exchanger is freely heated in the exhaust heat recovery circuit. Heat recovery device. In the engine, the excess air ratio of the air-fuel mixture combusted in the combustion chamber is set within a stoichiometric range, and a three-way catalyst is disposed in the exhaust gas heat exchanger, or the exhaust gas heat in the exhaust gas flow direction of the engine The exhaust heat recovery device for an engine according to claim 1, wherein a three-way catalyst is disposed upstream of the exchanger . The exhaust heat recovery circuit has an upstream end between the exhaust gas heat exchanger and the exhaust heat recovery heat exchanger and a downstream end downstream of the exhaust heat recovery heat exchanger. With a bypass to bypass the heat exchanger,
A flow rate distribution means for distributing and guiding the flow rate of the exhaust heat recovery medium flowing through the exhaust heat recovery circuit to one or both of the exhaust heat recovery heat exchanger and the bypass passage is provided. Item 3. The engine exhaust heat recovery apparatus according to Item 1 or 2 . The flow distribution means is a three-way valve;
The three-way valve includes a first flow state in which the flow state of the exhaust heat recovery medium flowing through the exhaust heat recovery circuit is introduced into the exhaust heat recovery heat exchanger, and the bypass of the exhaust heat recovery medium The exhaust heat recovery device for an engine according to claim 3 , wherein the exhaust heat recovery device for the engine is configured to be switchable to a second flow state to flow through the road . The temperature of the engine oil, the temperature of the engine cooling water between the engine cooling part of the engine cooling circuit and the exhaust heat recovery heat exchanger, and the heat exchanged with the exhaust gas in the exhaust gas heat exchanger A temperature measuring means for measuring at least one of the temperatures of the exhaust heat recovery medium, an operating state determining means for determining the operating state of the engine based on the measured temperature of the temperature measuring means,
When the operation state determination means determines that the engine operation state is a warm-up operation state, the three-way valve is opened and closed so that the flow state of the exhaust heat recovery medium is the second flow state. The exhaust heat recovery apparatus for an engine according to claim 4 , further comprising switching control means for switching the state . The three-way valve includes a temperature-sensitive three-way valve that senses the temperature of the exhaust heat recovery medium and switches between open and closed states, and the temperature-sensitive three-way valve exchanges heat with the exhaust gas in the exhaust gas heat exchanger. The exhaust heat of the engine according to claim 4 , wherein when the temperature of the exhaust heat recovery medium after the operation is higher than a predetermined value, the first flow state is set, and when the temperature is equal to or lower than the predetermined value, the second flow state is set. Recovery device.

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