JP5600307B2 - Engine exhaust heat recovery device - Google Patents

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.

  A conventional engine exhaust heat recovery device includes, for example, an engine cooling circuit that passes engine cooling water that cools the engine in order to recover the exhaust heat from an engine used as a power source in a cogeneration system, and the engine An exhaust heat recovery heat exchanger for exchanging heat between the cooling water and the exhaust heat recovery medium, an exhaust heat recovery circuit for passing the exhaust heat recovery medium to lead to the exhaust heat recovery heat exchanger, and an exhaust heat recovery heat exchanger Is provided with a hot water storage tank capable of storing hot water in the exhaust heat recovery medium after heat exchange with engine cooling water (see Patent Document 1).

Japanese Patent No. 3767785

By the way, there are two types of heat loads in houses, such as low-temperature heat loads that do not require high-temperature heat supply such as hot water supply to baths, and high-temperature heat loads that require high-temperature heat supply such as the start of floor heating. is there. If the temperature of the exhaust heat recovery medium stored in the hot water storage tank of the exhaust heat recovery device is increased to cope with the high temperature heat load, the temperature difference between the stored exhaust heat recovery medium and the surrounding environment will increase. A part of the heat of the exhaust heat recovery medium stored while waiting for the heat demand is lost due to heat dissipation, and there is a problem that heat dissipation loss increases.
The present invention has been made in view of the above problems, and an object of the present invention is to provide an exhaust heat recovery device for an engine that can suppress a heat dissipation loss by performing an exhaust heat recovery operation according to a temperature required by a thermal load. Is to provide.

In order to achieve the above object, an exhaust heat recovery apparatus for an engine according to the present invention comprises:
An exhaust heat recovery device for an engine having an exhaust heat recovery circuit for passing an exhaust heat recovery medium for recovering the exhaust heat of the engine.
An engine cooling circuit that circulates engine cooling water is provided in an engine cooling section that exchanges heat between the engine cylinder block and engine cooling water, and an exhaust gas heat exchanger that exchanges heat between exhaust gas and engine cooling water of the engine. ,
The exhaust heat recovery circuit includes an exhaust heat recovery heat exchanger that exchanges heat between the engine cooling water and the exhaust heat recovery medium after flowing through both the engine cooling unit and the exhaust gas heat exchanger,
Comprising a high-temperature heat load presence / absence determining means capable of determining the presence or absence of heat demand in the period from the present time at which heat dissipation of the current or exhaust heat recovery medium can be suppressed,
The first operation state in which the engine cooling water flows through the exhaust gas heat exchanger and then the engine cooling section can be executed, and the engine cooling water flows through the engine cooling section and then the exhaust gas heat exchanger. It is configured to be able to execute a second operation state that is one of an operation state of a serial operation state of flowing or a parallel operation state of flowing the engine cooling unit and the exhaust gas heat exchanger in parallel,
Comprising an operation control means for switching between the first operation state and the second operation state;
When the high temperature heat load presence / absence determining means determines that there is a heat demand associated with the high temperature heat load in the current period or the period from the present time at which heat dissipation of the exhaust heat recovery medium can be suppressed, the operation control means performs the second control. The point is to switch to the driving state.

In the engine exhaust heat recovery device of the present invention, when the exhaust heat recovery efficiency of the engine is increased, the operation control means switches to the first operation state, and the exhaust gas heat exchange is performed before the low-temperature engine coolant is led to the engine cooling section. The heat is recovered by exchanging heat between the engine coolant and the exhaust gas with a large temperature difference between them.
On the other hand, when the temperature of the exhaust heat recovery medium is increased to perform high-temperature heat recovery, the operation control means switches to the second operation state and guides the engine cooling water to the engine cooling unit or to the engine cooling unit. At the same time, it is led to an exhaust gas heat exchanger that can be expected to have a high recovery temperature, and the temperature of the engine cooling water is increased to perform high-temperature heat recovery.
In the exhaust heat recovery device for an engine according to the present invention, the execution of the second operating state in which priority is given to high temperature heat recovery is particularly close to the present time, particularly from the viewpoint of suppressing heat dissipation loss from the high temperature exhaust heat recovery medium. In the future (the future within a period in which the heat dissipation of the exhaust heat recovery medium can be suppressed), it is performed when there is a heat demand with a high temperature heat load.
Specifically, when the high temperature heat load existence determining means determines that there is a heat demand associated with the high temperature heat load in the current period or the period from the present when heat dissipation of the exhaust heat recovery medium can be suppressed, the operation control means performs the second operation. Switch to state. Thereby, after performing the 2nd operation state which gives priority to high temperature heat recovery, and making an exhaust heat recovery medium high temperature, the time until the said high temperature exhaust heat recovery medium is used by high temperature heat load can be shortened, Heat dissipation loss can be suppressed.
As described above, in particular, only when there is a heat demand associated with the high temperature heat load, the high temperature heat recovery is executed as the second operation state, and the exhaust heat recovery operation corresponding to the temperature required by the heat load is performed, thereby dissipating heat. An engine exhaust heat recovery device capable of suppressing loss can be realized.

A further characteristic configuration of the exhaust heat recovery device for an engine of the present invention is as follows:
When the high temperature heat load existence determining means determines that there is no heat demand associated with the high temperature heat load in the period from the present when the current or the heat dissipation of the exhaust heat recovery medium can be suppressed, the operation control means is the The point is to switch to the first operating state.

  According to the above characteristic configuration, when the high temperature heat load existence determination means determines that there is no heat demand associated with the high temperature heat load at present or in the near future from the present, the operation control means gives priority to the exhaust heat recovery efficiency. Since the operation state is switched, it is possible to efficiently use the recovered heat by supplying a relatively low-temperature exhaust heat recovery medium to a heat load that does not require a high temperature while performing an operation with improved exhaust heat recovery efficiency. it can.

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 includes a hot water storage tank capable of storing the exhaust heat recovery medium,
Comprising a temperature measuring means capable of measuring the temperature of the exhaust heat recovery medium stored in the hot water tank,
When the high temperature heat load existence determination means determines that there is a heat demand associated with the high temperature heat load in the period from the present when the heat dissipation of the current or exhaust heat recovery medium can be suppressed,
The operation control means switches to the second operation state when the hot water storage temperature of the hot water storage tank is higher than the hot water storage temperature threshold, and when the operation control means is less than the hot water storage temperature threshold, the first operation state. It is in the point to switch to.

According to the above characteristic configuration, when the high temperature heat load existence determining means determines that there is a heat demand accompanying the high temperature heat load at present or in the near future from the present, the temperature of the stored exhaust heat recovery medium is equal to or higher than the hot water temperature threshold. Only when the amount of heat stored in the hot water storage tank is sufficient, the high temperature heat recovery is performed by switching to the second operation state. On the other hand, when the temperature of the stored hot heat recovery medium is lower than the hot water storage temperature threshold and the amount of heat stored in the hot water storage tank is insufficient, the first heat state is switched to give priority to the exhaust heat recovery efficiency.
That is, according to the above-described characteristic configuration, even when there is a heat demand associated with a high-temperature heat load, the exhaust heat recovery operation is switched in consideration of the amount of heat stored in the hot water storage tank. The balance with recovery can be maintained appropriately.

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 includes a hot water storage tank capable of storing the exhaust heat recovery medium,
An exhaust heat recovery medium supply path that guides the exhaust heat recovery medium that has passed through the exhaust heat recovery heat exchanger and is not stored in the hot water storage tank to the heat load terminal that generates a high temperature heat load in the exhaust heat recovery circuit; Prepared,
A switching valve for switching the flow of the exhaust heat recovery medium circulating in the exhaust heat recovery circuit to the flow through the exhaust heat recovery medium supply path,
When the high-temperature heat load presence determination means determines that there is a heat demand associated with a high-temperature heat load in the period from the present when the current or the exhaust heat recovery medium can suppress heat dissipation, the operation control means, While switching to a 2nd driving | running state, it exists in the point which switches the said switching valve so that an exhaust heat recovery medium may be guide | induced to the said exhaust heat recovery medium supply path.

According to the above characteristic configuration, the high-temperature heat load is directly applied to the exhaust heat recovery medium, which has become high temperature in the second operation state in which priority is given to high-temperature heat recovery, through the exhaust heat recovery medium supply path without storing the hot water in the hot water storage tank. Can be led to a heat load terminal that generates heat, and heat dissipation loss can be suppressed.
In addition, according to the above characteristic configuration, when the high temperature heat load existence determining means determines that there is a heat demand associated with the high temperature heat load in the current period or the period from the present when the heat dissipation of the exhaust heat recovery medium can be suppressed. In addition, since the operation control means switches to the second operation state and the switching valve is switched so as to guide the exhaust heat recovery medium to the exhaust heat recovery medium supply path, the temperature becomes high in the second operation state where priority is given to high temperature heat recovery. The exhaust heat recovery medium can be directly led to the heat load terminal that generates the high temperature heat load via the exhaust heat recovery medium supply path without storing the hot water in the hot water storage tank, so that the heat dissipation loss can be suppressed.

A further characteristic configuration of the exhaust heat recovery device for an engine of the present invention is as follows:
The present is a first setting period which is the setting period including the present time among time-series setting periods obtained by dividing a day by unit time,
The period from the present time in which the heat dissipation of the exhaust heat recovery medium can be suppressed is a second set period that is the next set period following the first set period.

  According to the above characteristic configuration, in the exhaust heat recovery apparatus for an engine of the present invention, the first set period including the current time or the first set period among the time-series set periods obtained by dividing the day into unit times. In the subsequent second setting period, since it is determined whether or not there is a heat demand associated with the high temperature heat load, whether or not there is a heat demand associated with the high temperature heat load is determined in the present or near future.

A further characteristic configuration of the exhaust heat recovery device for an engine of the present invention is as follows:
A thermal load storage unit that stores actual thermal load data in the set period for each set period;
The high temperature thermal load presence / absence determining means is configured to generate heat with a high temperature thermal load in the first setting period or the second setting period based on the past thermal load data in the setting period stored in the thermal load storage unit. The point is to predict the demand and determine the presence or absence of the heat demand accompanied by the high-temperature heat load based on the prediction.

  According to the above characteristic configuration, the high-temperature thermal load presence / absence determining means is based on the past actual thermal load data stored in the thermal load storage unit, and the heat demand accompanied by the high-temperature thermal load in the first setting period or the second setting period. Therefore, it is possible to appropriately predict the heat demand accompanying the high temperature heat load at the present or near future from the present in a state in accordance with the past actual heat load. And based on the said prediction, the heat demand accompanying the high temperature heat load of the present or near future can be determined appropriately.

A further characteristic configuration of the exhaust heat recovery device for an engine of the present invention is as follows:
The heat demand accompanying the high temperature heat load is that it is a heat demand accompanying the rise of the heating heat load terminal.

  According to the above characteristic configuration, as the heat demand accompanying the high temperature heat load, the second operation that prioritizes the high temperature heat recovery with respect to the heat demand that requires very high temperature heat due to the rise of the heating heat load terminal. By appropriately supplying the high-temperature heat recovered depending on the state, the time required for starting up the heating heat load terminal can be shortened.

It is a schematic block diagram in the 1st driving | running state in embodiment of this invention. It is a schematic block diagram in the 2nd driving | running state in embodiment of this invention. It is a driving | operation control flowchart of this invention. It is a schematic block diagram in the 1st driving | running state in another embodiment of this invention. It is a schematic block diagram in the 2nd driving | running state in another embodiment of this invention.

An embodiment of a cogeneration system to which an exhaust heat recovery device for an engine 11 according to the present invention is applied will be described with reference to the drawings. The present invention is configured to be switchable between a first operation state that prioritizes exhaust heat recovery efficiency of the engine 11 and a second operation state that prioritizes high-temperature heat recovery. When there is a high-temperature heat load at the load 15, there is a feature in that the heat dissipation loss is suppressed by switching to the second operation state where priority is given to high-temperature heat recovery.
Below, after demonstrating the basic composition of the said cogeneration system first, the structure which suppresses the said heat dissipation loss is demonstrated.

As shown in FIGS. 1 and 2, the cogeneration system of the present invention includes a power generation device 13 that generates power to be supplied to an electric power load 12 driven by the engine 11, an engine cooling unit 30 of the engine 11, and an engine 11. An engine cooling circuit 10 for causing the engine cooling water W to flow through the exhaust gas heat exchanger 27 and the exhaust heat recovery heat exchanger 26 for recovering the exhaust heat of the exhaust gas E, and an exhaust heat recovery medium M for recovering the exhaust heat of the engine 11 And an exhaust heat recovery circuit 14 that passes the exhaust heat recovery heat exchanger 26 to the exhaust heat recovery heat exchanger 26, and the heat recovered by the exhaust heat recovery medium M of the exhaust heat recovery circuit 14 can be supplied to the heat load 15.
The heat load 15 includes a low-temperature heat load terminal 15a that requires only a low-temperature heat supply such as hot water supply, and a high-temperature heat load terminal 15b that requires a high-temperature heat supply at the start-up, such as floor heating. .

  On the output side of the power generation device 13, an inverter 16 for grid connection is provided, and the inverter 16 sets the output power of the power generation device 13 to the same voltage and the same frequency as the power supplied from the commercial system 17. It is configured. The commercial system 17 is electrically connected to a power load 12 such as a television, a refrigerator, or a washing machine via a power supply line 18.

  The inverter 16 is electrically connected to the power supply line 18 via the cogeneration power supply line 19, and the generated power from the power generator 13 can be supplied to the power load 12 via the inverter 16 and the cogeneration power supply line 19. It is configured. Although not shown in the figure, the power supply line 18 is provided with power load measuring means for measuring the load power of the power load 12, and this power load measuring means generates a reverse power flow in the current flowing through the power supply line 18. It is configured to detect whether or not. And the electric power supplied to the electric power supply line 18 from the electric power generating apparatus 13 is controlled by the inverter 16 so that a reverse power flow does not occur, and the surplus electric power of the generated electric power is converted into the electric heater 20 that can convert the surplus electric power into heat. It is configured to be supplied.

  The electric heater 20 is provided so as to freely heat engine cooling water W flowing through an engine cooling circuit 10 described later. The electric heater 20 can adjust the heating amount of the engine cooling water W according to the amount of surplus power so that the power consumption increases and the heating amount of the engine cooling water W increases as the amount of surplus power increases. It is configured.

  The operation of the engine 11 is controlled by the control device 22. The engine 11 has a configuration similar to that of a normal four-cycle engine. After an air-fuel mixture of fuel gas (for example, natural gas) and air is sucked into a combustion chamber (not shown), the air-fuel mixture is discharged in the combustion chamber. Then, the air-fuel mixture is ignited and combusted and expanded in the combustion chamber, and the exhaust gas E generated by the combustion is exhausted to the exhaust passage 23. Although not shown, the exhaust passage 23 of the engine 11 is provided with an oxygen sensor that detects the oxygen concentration of the exhaust gas E. The control device 22 adjusts the supply amount of the fuel gas so that the oxygen concentration of the exhaust gas E detected by the oxygen sensor becomes substantially zero. Thereby, the excess air ratio of the air-fuel mixture supplied to the combustion chamber of the engine 11 is set within a stoichiometric range of approximately 1.0. Here, the excess air ratio indicates the air-fuel ratio of the air-fuel mixture divided by the stoichiometric air-fuel ratio.

  The exhaust path 23 of the engine 11 includes an exhaust gas heat exchanger 27 that exchanges heat between the exhaust gas E exhausted from the engine 11 to the exhaust path 23 and engine cooling water W that flows through the engine cooling circuit 10 described later. . The exhaust gas heat exchanger 27 is, for example, a catalyst-integrated heat exchanger in which a three-way catalyst 34 formed by supporting a noble metal component such as platinum, palladium, or rhodium on an inorganic carrier such as alumina is integrally provided. It is composed of. As described above, since the excess air ratio of the air-fuel mixture supplied to the combustion chamber (not shown) is set within the stoichiometric range of about 1.0, the engine 11 is connected to the exhaust gas heat exchanger 27. The three-way catalyst 34 disposed integrally can simultaneously remove three substances of hydrocarbon (HC), carbon monoxide (CO), and nitrogen oxide (NOx) from the exhaust gas E.

The exhaust heat recovery circuit 14 uses the hot water in the hot water storage tank 24 as the exhaust heat recovery medium M, passes the exhaust heat recovery medium M taken out from the hot water storage tank 24, recovers the exhaust heat of the engine 11, and has the exhaust heat. The waste heat recovery medium M is returned to the hot water storage tank 24. The exhaust heat recovery circuit 14 includes, in order from the upstream side in the flow direction of the exhaust heat recovery medium M, exhaust heat recovery medium circulation pump 25, engine cooling water W flowing through an engine cooling circuit 10 described later, and exhaust heat. An exhaust heat recovery heat exchanger 26 that exchanges heat with the recovery medium M and a hot water storage tank 24 are provided.
The hot water storage tank 24 is provided with a water supply path 28 that can supply water to the hot water storage tank 24 from the outside so that the hot water storage tank 24 is appropriately supplied with water.

The exhaust heat recovery circuit 14 heats the exhaust heat recovery medium M via a third three-way valve 50 (an example of a switching valve) downstream of the exhaust heat recovery heat exchanger 26 and upstream of the hot water storage tank 24. An exhaust heat recovery medium supply path 51 that leads to the load 15 is provided.
The third three-way valve 50 is configured to guide the exhaust heat recovery medium M from the exhaust heat recovery heat exchanger 26 to the hot water storage tank 24, to guide the exhaust heat recovery medium M from the exhaust heat recovery heat exchanger 26 to the heat load 15, The three states of the state in which the heat recovery medium M is guided from the hot water storage tank 24 to the heat load 15 can be switched. The above switching of the third three-way valve 50 is executed by the control device 22 described later based on the prediction of the heat demand at the present or near future heat load 15 from the present.

  The exhaust heat recovery medium supply path 51 is switched at the exhaust heat recovery heat exchanger 26 by switching the third three-way valve 50 to guide the exhaust heat recovery medium M from the exhaust heat recovery heat exchanger 26 to the heat load 15. The exhaust heat recovery medium M that has reached a high temperature functions as a flow path that directly supplies the heat load 15 without storing it in the hot water storage tank 24. The exhaust heat recovery medium supply path 51 is switched so that the third three-way valve 50 guides the exhaust heat recovery medium M from the hot water storage tank 24 to the thermal load 15, so that the exhaust heat recovery medium M stored in the hot water storage tank 24 is switched. Is supplied to the heat load 15.

The engine cooling circuit 10 includes an exhaust gas heat exchanger 27 that exchanges heat between the exhaust gas E of the engine 11 and the engine coolant W, an engine cooling unit 30 that exchanges heat between the cylinder block of the engine 11 and the engine coolant W, The exhaust heat recovery heat exchanger 26 that exchanges heat between the engine coolant W and the exhaust heat recovery medium M after passing through all of the heater 20, the engine cooling unit 30, the exhaust gas heat exchanger 27, and the electric heater 20. In addition, the engine cooling water W is arranged to circulate.
The engine cooling circuit 10 includes an expansion tank 32 that can store engine cooling water W downstream of the exhaust heat recovery heat exchanger 26 and upstream of the four-way valve 33, and an engine that can pump engine cooling water W. A cooling water circulation pump 36 is provided. The engine coolant circulation pump 36 is appropriately driven and controlled by the control device 22.

The engine cooling circuit 10 is provided with a four-way valve 33. When the control device 22 switches the four-way valve 33, the engine cooling circuit 10 has a first circuit C1 indicated by a thick line in FIG. 2 and the second circuit C2 indicated by a bold line in FIG. 2, and the control device 22 functions as an operation control means 22c for controlling the switching.
That is, in the first operation state in which the exhaust heat recovery efficiency of the engine 11 is increased, the four-way valve 33 supplies the engine cooling water W to the exhaust gas heat exchanger 27, the engine cooling unit 30, and the electric heater 20 in series in the order described. A first circuit C1 (a circuit indicated by a thick line in FIG. 1) is made to flow and collect heat, and then is guided to the exhaust heat recovery heat exchanger 26 to exchange heat with the exhaust heat recovery medium M. On the other hand, in the second operation state in which high-temperature heat recovery is prioritized in the hot water storage tank 24, the engine cooling water W is passed through the engine cooling unit 30, the exhaust gas heat exchanger 27, and the electric heater 20 in series in the order of the heat. Then, the second circuit C2 (circuit shown by a thick line in FIG. 2) is introduced to the exhaust heat recovery heat exchanger 26 to exchange heat with the exhaust heat recovery medium M.

Thereby, in the first operation state in which the exhaust heat recovery efficiency is increased, the engine cooling water W having a relatively low temperature is first led to the exhaust gas heat exchanger 27 where a high recovery temperature can be expected, and then the engine cooling unit By leading to 30 and recovering the exhaust heat, the temperature difference between the engine cooling water W and the exhaust gas E is increased to improve the exhaust heat recovery efficiency.
On the other hand, when the hot water storage tank 24 is in the second operation state where priority is given to high-temperature heat recovery, after the engine cooling water W is first preheated in the engine cooling unit 30, an exhaust gas heat exchanger that can be expected to have a high recovery temperature. By leading to 27 and further recovering the exhaust heat, the temperature of the engine cooling water W can be made sufficiently high, and high-temperature heat recovery is realized.

The switching of the four-way valve 33 is configured to be switched by the control device 22 (an example of the operation control means 22c) according to the temperature required by the thermal load 15.
The control device 22 includes a thermal load storage unit 22 a that stores past actual thermal load data in the thermal load 15. The actual heat load data is stored for each time-series setting period (for example, 1 hour) obtained by dividing one day into unit times.
And the control apparatus 22 is the next setting following the 1st setting period or the 1st setting period which is a setting period including the present time based on the performance heat load data in the past setting period memorize | stored in the heat load memory | storage part 22a. The heat demand in the second setting period, which is a period, is predicted, and based on the prediction, it is configured to work as the high-temperature heat load presence / absence determining means 22b that determines the presence / absence of the heat demand accompanying the high-temperature heat load. And the exhaust heat recovery apparatus of this invention is comprised so that a driving | operation may be switched as follows based on the determination of the high temperature heat load presence determination means 22b.
That is, the operation control means 22c is configured to control each device in accordance with the determination of the high temperature heat load presence determination means 22b.

[Switch to the second operating state that prioritizes high-temperature heat recovery]
When the control device 22 (an example of the high-temperature heat load existence determination unit 22b) determines that there is a heat demand associated with the high-temperature heat load in the present or near future (the first setting period or the second setting period). In this case, the four-way valve 33 is controlled to switch from the first circuit C1 (the circuit indicated by the bold line in FIG. 1) to the second circuit C2 (the circuit indicated by the thick line in FIG. 2), giving priority to the exhaust heat recovery efficiency. The control is switched from the first operation state to the second operation state where priority is given to high-temperature heat recovery. As a result, when there is a high-temperature heat load at present or in the near future, high-temperature heat recovery is performed to supply the high-temperature exhaust heat recovery medium M to the high-temperature heat load terminal 15b to suppress heat dissipation loss. .
In addition, when it determines with the control apparatus 22 having the heat demand accompanying a high temperature heat load in the present or the near future from the present, the 3rd three-way valve 50 and the waste heat recovery medium M from the waste heat recovery heat exchanger 26 are determined. The control is switched to the state leading to the high temperature heat load terminal 15b. Thereby, the high-temperature exhaust heat recovery medium M is directly guided to the high-temperature heat load terminal 15b without being stored in the hot water storage tank 24, thereby further reducing the heat dissipation loss.

[Switch to the first operating state that prioritizes exhaust heat recovery efficiency]
The control device 22 (an example of the high temperature heat load existence determination unit 22b) determines that there is no heat demand associated with the high temperature heat load in the present or the near future from the present (the first setting period or the second setting period). In this case, the four-way valve 33 is controlled to switch from the second circuit C2 (a circuit indicated by a thick line in FIG. 2) to the first circuit C1 (a circuit indicated by a thick line in FIG. 1), and priority is given to high-temperature heat recovery. The control is switched from the second operation state to the first operation state in which exhaust heat recovery efficiency is prioritized. As a result, when there is no high-temperature heat load at present or in the near future, the heat demand for the low-temperature heat load terminal 15a that does not require high-temperature heat supply while giving priority to exhaust heat recovery efficiency. A low-temperature exhaust heat recovery medium M suitable for the above is supplied.

[Switching between the first operation state and the second operation state based on the temperature of the exhaust heat recovery medium of the hot water tank]
Furthermore, in the exhaust heat recovery device for the engine 11 of the present invention, the control device 22 (an example of the high temperature heat load existence judging means 22b), as described above, the presence or absence of the present high temperature heat load in the near future from the present. The exhaust heat recovery state is switched based on the control, and the exhaust heat recovery state is switched and controlled in consideration of the temperature of the exhaust heat recovery medium M stored in the hot water storage tank 24. .
In other words, the hot water storage tank 24 is provided with a temperature sensor 35 (an example of temperature measuring means) that measures the temperature of the exhaust heat recovery medium M stored in the hot water.
In the case where the control device 22 (an example of the high temperature heat load existence determination unit 22b) determines that there is a heat demand associated with the high temperature heat load in the present or the near future (the first setting period or the second setting period), When the temperature of the exhaust heat recovery medium M measured by the temperature sensor 35 is equal to or higher than the hot water storage temperature threshold (for example, 40 ° C.) that is the temperature of the hot water storage tank 24 on the higher hot water storage temperature side, the four-way valve 33 is turned on. Switching control is performed to switch from the first circuit (the circuit indicated by the thick line in FIG. 1) to the second circuit (the circuit indicated by the thick line in FIG. 2), thereby setting the second operation state in which high-temperature heat recovery is prioritized. On the other hand, when the control device 22 (an example of the operation control unit 22c) determines that there is a heat demand associated with a high-temperature heat load in the present or in the near future from the present, the exhaust heat recovery measured by the temperature sensor 35 is performed. When the temperature of the medium M is lower than the hot water storage temperature threshold value, the four-way valve 33 is controlled to be switched from the second circuit to the first circuit, and the first operation state in which exhaust heat recovery efficiency is prioritized is set.
As a result, even if it is determined that there is a heat demand associated with a high temperature heat load in the present or in the near future, the amount of heat stored in the hot water storage tank 24 is not sufficient, instead of simply performing high temperature heat recovery. In this case, priority is given to exhaust heat recovery efficiency, and the operation is controlled so that high temperature heat recovery is performed only when the heat storage capacity is sufficient, so the balance between exhaust heat recovery efficiency and high temperature heat recovery should be kept appropriate. Can do.

Next, the flow of control in the exhaust heat recovery apparatus of the present invention will be described based on the control flow of FIG.
When the exhaust heat recovery operation is started, the control device 22 (an example of the operation control unit 22c) drives the engine 11 and causes the engine cooling water circulation pump 36 to work to flow the engine cooling water W to the engine cooling circuit 10. Then, the exhaust heat recovery medium circulation pump 25 is operated to pass the exhaust heat recovery medium M through the exhaust heat recovery circuit 14 (# 01).

  The control device 22 (an example of the high-temperature thermal load presence / absence determining unit 22b) extracts past actual thermal load data to the thermal load storage unit 22a, and based on the extracted actual thermal load data, the present or the near future from the present ( Presence / absence of a high-temperature heat load in the first setting period or the second setting period) is predicted and determined (# 02, 03).

When the control device 22 (an example of the high temperature heat load existence determination unit 22b) determines that there is no high temperature heat load at the present time or in the near future (the first setting period or the second setting period), the exhaust heat recovery is performed. Switch to the first operating state giving priority to efficiency (# 04, 05).
On the other hand, when it is determined that a high-temperature heat load is present at present or in the near future from the present, the hot water storage temperature and the hot water temperature threshold of the exhaust heat recovery medium M stored in the hot water storage tank 24 measured by the temperature sensor 35 are calculated. Compare (# 04, 06).

  The control device 22 (an example of the operation control unit 22c) switches to the second operation state where priority is given to high-temperature heat recovery when the hot water storage temperature of the exhaust heat recovery medium M is equal to or higher than the hot water storage temperature threshold and the heat storage amount is sufficient. When the hot water storage temperature of the exhaust heat recovery medium M is lower than the hot water storage temperature threshold and the amount of stored heat is insufficient, the first operation state in which the exhaust heat recovery efficiency is prioritized is switched (# 07, 08).

  The control device 22 (an example of the operation control means 22c) executes the above-described flow of # 02 to # 08 until the exhaust heat recovery operation is stopped, and when the exhaust heat recovery operation is stopped, the engine 11 is turned off. The engine cooling water circulation pump 36 is stopped, and the exhaust heat recovery medium circulation pump 25 is stopped (# 09, 10).

[Example of temperature in the first operating state]
Here, an example of the temperature in each part of the present invention is shown in the first operation state. In the following description, it is assumed that surplus power is not supplied to the electric heater 20 and the electric heater 20 is not heating the engine coolant W.
The engine 11 is performing rated operation, the temperature of the cylinder head is 100 ° C., the temperature of the exhaust gas E at the inlet of the exhaust gas heat exchanger 27 is 500 ° C., and the temperature of the exhaust gas E at the outlet of the exhaust gas heat exchanger 27 is 75. When the temperature of the exhaust heat recovery medium M led from the hot water storage tank 24 to the inlet of the exhaust heat recovery heat exchanger 26 is 20 ° C. and the flow rate of the exhaust heat recovery medium M is 5 L / min, the engine cooling is performed. The temperature of the water W is 70 ° C. at the outlet of the exhaust heat recovery heat exchanger 26 and the inlet of the exhaust gas heat exchanger 27, and 77 ° C. at the outlet of the exhaust gas heat exchanger 27 and the inlet of the engine cooling unit 30. 80 ° C. at the outlet of the unit 30 and the inlet of the electric heater 20, and 80 ° C. at the outlet of the electric heater 20 and the inlet of the exhaust heat recovery heat exchanger 26. As described above, it is assumed that the electric heater 20 does not heat the engine coolant W in the present embodiment.
At this time, the temperature of the exhaust heat recovery medium M at the outlet of the exhaust heat recovery heat exchanger 26 is 75 ° C., and the temperature of the exhaust heat recovery medium M stored in the hot water storage tank 24 is also 75 ° C.

[Example of temperature in the second operation state]
On the other hand, in the second operation state, an example of the temperature at each part of the present invention is shown. The engine 11 is performing the rated operation, the temperature of the cylinder head is 100 ° C., and the exhaust gas at the inlet of the exhaust gas heat exchanger 27. When the temperature of E is 500 ° C. and the temperature of the exhaust gas E at the outlet of the exhaust gas heat exchanger 27 is 75 ° C., the exhaust heat recovery medium M led from the hot water storage tank 24 to the inlet of the exhaust heat recovery heat exchanger 26 When the temperature is 20 ° C. and the flow rate of the exhaust heat recovery medium M is 5 L / min, the temperature of the engine cooling water W is 77 ° C. at the outlet of the exhaust heat recovery heat exchanger 26 and the inlet of the engine cooling unit 30. 80 ° C. at the outlet of the section 30 and the inlet of the exhaust gas heat exchanger 27, 85 ° C. at the outlet of the exhaust gas heat exchanger 27 and the inlet of the electric heater 20, the outlet of the electric heater 20 and the inlet of the exhaust heat recovery heat exchanger 26 At 85 ℃ .
At this time, the temperature of the exhaust heat recovery medium M at the outlet of the exhaust heat recovery heat exchanger 26 is 80 ° C., and the temperature of the exhaust heat recovery medium M stored in the hot water storage tank 24 is also 80 ° C.

[Another embodiment]
Another embodiment of the present invention is the same as the above embodiment with respect to the basic configuration, and the configuration related to the engine cooling circuit 10 is different. Therefore, in the following, this point will be particularly described with reference to FIGS. 3 and 4, and the same components as those in the embodiment will be denoted by the same reference numerals and description thereof will be omitted.

The engine cooling circuit 10 is provided with two first three-way valves 37a and a second three-way valve 37b as valve mechanisms. The engine cooling circuit 10 includes a third circuit C3 indicated by a bold line in FIG. 4 when the control device 22 (an example of the operation control means 22c) switches the first three-way valve 37a and the second three-way valve 37b. 5 is configured to be switchable between a fourth circuit C4 indicated by a thick line.
Here, the first three-way valve 37a receives the engine cooling water W after flowing through the exhaust heat recovery heat exchanger 26 from the upstream side thereof, and also transfers the engine cooling water W to the exhaust gas heat exchanger 27 on the downstream side thereof. It is provided so as to lead to either one of the engine cooling units 30. The second three-way valve 37b receives the engine cooling water W after flowing through the exhaust gas heat exchanger 27 from the upstream side thereof, and the engine cooling water W is sent to either the engine cooling unit 30 or the bypass path 38 on the downstream side. It is provided so that it may guide to either.
In other words, the first three-way valve 37a and the second three-way valve 37b are configured so that the engine cooling water W is discharged from the exhaust gas heat exchanger 27, the engine cooling unit 30, in the first operation state in which the exhaust heat recovery efficiency of the engine 11 is increased. A third circuit C3 (a circuit indicated by a bold line in FIG. 4) is caused to flow through the electric heater 20 in series in the order described so as to recover the heat, and then conduct heat to the exhaust heat recovery heat exchanger 26 to exchange heat with the exhaust heat recovery medium M. And On the other hand, in the second operation state in which high-temperature heat recovery is prioritized, the engine cooling water W is passed through both the exhaust gas heat exchanger 27 and the engine cooling water W in parallel, and then the electric heater 20 is passed. The fourth circuit C4 (circuit shown by a bold line in FIG. 5) is made to flow and collect heat, and then is guided to the exhaust heat recovery heat exchanger 26 to exchange heat with the exhaust heat recovery medium M.

Thereby, in the first operation state in which the exhaust heat recovery efficiency is increased, the engine cooling water W having a relatively low temperature is first led to the exhaust gas heat exchanger 27 where a high recovery temperature can be expected, and then the engine cooling unit By exhausting to 30 and recovering exhaust heat, exhaust heat recovery efficiency is improved in the exhaust gas heat exchanger 27 in a form in which the temperature difference between the engine cooling water W and the exhaust gas E is increased.
On the other hand, in the second operation state in which high-temperature heat recovery is prioritized, the engine cooling water W is guided in parallel to the exhaust gas heat exchanger 27 and the engine cooling unit 30 that can be expected to have a high recovery temperature to recover exhaust heat. Thus, the temperature of the engine cooling water W can be sufficiently increased, and high-temperature heat recovery is performed.

Also in the present embodiment, the control device 22 (an example of the high temperature thermal load presence / absence determining unit 22b) is configured to perform the first operation state and the second operation based on the presence / absence of heat demand accompanied by the high temperature heat load in the present or near future. The switching control with respect to the state is performed. Since the switching control is the same control as in the present embodiment, the description thereof is omitted here.
Also in the present embodiment, the control device 22 is based on the temperature of the exhaust heat recovery medium M stored in the hot water storage tank 24 when there is a heat demand with a high temperature heat load in the present or near future. The switching control between the first operating state and the second operating state is performed, but the switching control is also the same control as that of the present embodiment, and thus the description thereof is omitted here.

[Example of temperature in the first operating state]
Here, in the first operating state, an example of the temperature at each part of the exhaust heat recovery device is shown. The engine 11 is performing rated operation, the temperature of the cylinder head is 100 ° C., and the exhaust gas heat exchanger 27 When the temperature of the exhaust gas E at the inlet is 500 ° C. and the temperature of the exhaust gas E at the outlet of the exhaust gas heat exchanger 27 is 75 ° C., the exhaust heat recovery led from the hot water storage tank 24 to the inlet of the exhaust heat recovery heat exchanger 26. When the temperature of the medium M is 20 ° C. and the flow rate of the exhaust heat recovery medium M is 5 L / min, the temperature of the engine cooling water W is 70 at the outlet of the exhaust heat recovery heat exchanger 26 and the inlet of the exhaust gas heat exchanger 27. 80 ° C. at the outlet of the exhaust gas heat exchanger 27 and the inlet of the engine cooling unit 30, 80 ° C. at the outlet of the engine cooling unit 30 and the inlet of the electric heater 20, and the exhaust heat recovery heat exchanger from the outlet of the electric heater 20 8 at the entrance of 26 ° C., and the temperature of the exhaust heat recovery medium M at the outlet of the exhaust heat recovery heat exchanger 26 becomes 75 ° C., temperature 75 ° C. of the exhaust heat recovery medium M is guided to the hot water storage tank 24.

[Example of temperature in the second operation state]
On the other hand, in the second operation state, an example of the temperature at each part of the exhaust heat recovery apparatus is shown. The engine 11 is performing the rated operation, the temperature of the cylinder head is 100 ° C., and the inlet of the exhaust gas heat exchanger 27 The exhaust heat recovery medium is introduced from the hot water storage tank 24 to the inlet of the exhaust heat recovery heat exchanger 26 when the temperature of the exhaust gas E is 500 ° C. and the temperature of the exhaust gas E at the outlet of the exhaust gas heat exchanger 27 is 75 ° C. When the temperature of M is 20 ° C. and the flow rate of the exhaust heat recovery medium M is 5 L / min, the temperature of the engine cooling water W is the outlet of the exhaust heat recovery heat exchanger 26, the inlet of the exhaust gas heat exchanger 27, and the engine cooling unit. 30 ° C. at the inlet of 30, 87 ° C. at the outlet of the exhaust gas heat exchanger 27, 83 ° C. at the outlet of the engine cooling unit 30, 85 ° C. at the inlet of the electric heater 20, 85 ° C. at the outlet of the electric heater 20 It becomes. As described above, it is assumed that the electric heater 20 does not heat the engine coolant W in the present embodiment.
At this time, the temperature of the exhaust heat recovery medium M at the outlet of the exhaust heat recovery heat exchanger 26 is 80 ° C., and the temperature of the exhaust heat recovery medium M guided to the hot water storage tank 24 is 80 ° C.

(2) In the above embodiment, the engine 11 has the excess air ratio of the air-fuel mixture supplied to the combustion chamber set within a stoichiometric range of approximately 1.0. Can be set within a large lean range.

(3) The exhaust heat recovery medium M is circulated by the operation of the exhaust heat recovery medium circulation pump 25 provided in the exhaust heat recovery circuit 14. For example, the exhaust heat recovery medium M is exhausted using the water pressure of the supply water in the water supply path 28. The collection medium M can also be passed.

(4) In the above embodiment, the electric heater 20 heats the engine cooling water W when surplus power is generated. However, in the second operation state in which high-temperature hot water is stored, regardless of the presence or absence of surplus power. The engine coolant W may be heated.

(5) In the above embodiment, when the temperature of the exhaust heat recovery medium M stored in the hot water storage tank 24 is low, the control device 22 (an example of the operation control unit 22c) prioritizes the exhaust heat recovery efficiency. The control for setting the first operation state is performed. However, when giving priority to high-temperature hot water storage, the control device 22 performs control for setting the second operation state even when the temperature of the exhaust heat recovery medium M stored in the hot water storage tank 24 is low. It doesn't matter.

(6) In the above embodiment, when the control device 22 (an example of the operation control unit 22c) has a heat demand associated with a high-temperature heat load at the present time or in the near future from the present time, the stored heat recovery medium M is stored. A configuration is shown in which control is performed to switch between the first operation state and the second operation state in accordance with the hot water storage temperature.
However, in addition to the hot water storage temperature of the stored exhaust heat recovery medium M, the control device 22, for example, according to the temperature of the exhaust heat recovery medium M at the outlet of the exhaust heat recovery heat exchanger 26 of the exhaust heat recovery circuit 14, You may control to switch a 1st driving | running state and a 2nd driving | running state.
Further, the control device 22 (an example of the high-temperature heat load existence determination unit 22b) directly acquires information on the heat demand of the high-temperature heat load terminal 15b, and determines whether there is currently a heat demand associated with the high-temperature heat load. You may comprise so that it may control.

(7) In the above embodiment, the configuration in which the exhaust heat recovery medium supply path 51 is connected between the exhaust heat recovery heat exchanger 26 of the exhaust heat recovery circuit 14 and the hot water storage tank 24 is shown. However, the exhaust heat recovery medium supply path 51 is provided so as to guide the exhaust heat recovery medium M from the outlet of the exhaust heat recovery heat exchanger 26 to the high temperature heat load terminal 15b in a state independent of the exhaust heat recovery circuit 14. It doesn't matter.

  The engine exhaust heat recovery apparatus according to the present invention can be effectively used as an engine exhaust heat recovery apparatus capable of suppressing heat dissipation loss by performing an exhaust heat recovery operation according to a temperature required by a heat load. .

M: exhaust heat recovery medium W: engine cooling water E: exhaust gas 10: engine cooling circuit 11: engine 14: exhaust heat recovery circuit 15b: high temperature heat load terminal (an example of a heat load terminal)
22: Control device 22a: Thermal load storage unit 22b: High temperature thermal load existence determining unit 22c: Operation control unit 24: Hot water storage tank 26: Waste heat recovery heat exchanger 27: Exhaust heat exchanger 30: Engine cooling unit 33: Four-way valve 35: Temperature sensor 37a: First three-way valve 37b: Second three-way valve 50: Third three-way valve 51: Waste heat recovery medium supply path

Claims (7)

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 is provided in an engine cooling section that exchanges heat between the engine cylinder block and engine cooling water, and an exhaust gas heat exchanger that exchanges heat between exhaust gas and engine cooling water of the engine. ,
The exhaust heat recovery circuit includes an exhaust heat recovery heat exchanger that exchanges heat between the engine cooling water and the exhaust heat recovery medium after flowing through both the engine cooling unit and the exhaust gas heat exchanger,
Comprising a high-temperature heat load presence / absence determining means capable of determining the presence or absence of heat demand in the period from the present time at which heat dissipation of the current or exhaust heat recovery medium can be suppressed,
The first operation state in which the engine cooling water flows through the exhaust gas heat exchanger and then the engine cooling section can be executed, and the engine cooling water flows through the engine cooling section and then the exhaust gas heat exchanger. It is configured to be able to execute a second operation state that is one of an operation state of a serial operation state of flowing or a parallel operation state of flowing the engine cooling unit and the exhaust gas heat exchanger in parallel,
Comprising an operation control means for switching between the first operation state and the second operation state;
When the high temperature heat load presence / absence determining means determines that there is a heat demand associated with the high temperature heat load in the current period or the period from the present time at which heat dissipation of the exhaust heat recovery medium can be suppressed, the operation control means performs the second control. An engine exhaust heat recovery device that switches to an operating state.   When the high temperature heat load existence determining means determines that there is no heat demand associated with the high temperature heat load in the period from the present when the current or the heat dissipation of the exhaust heat recovery medium can be suppressed, the operation control means is the The exhaust heat recovery device for an engine according to claim 1, wherein the exhaust heat recovery device is switched to a first operation state. The exhaust heat recovery circuit includes a hot water storage tank capable of storing the exhaust heat recovery medium,
Comprising a temperature measuring means capable of measuring the temperature of the exhaust heat recovery medium stored in the hot water tank,
When the high temperature heat load existence determination means determines that there is a heat demand associated with the high temperature heat load in the period from the present when the heat dissipation of the current or exhaust heat recovery medium can be suppressed,
The operation control means switches to the second operation state when the hot water storage temperature of the hot water storage tank is higher than the hot water storage temperature threshold, and when the operation control means is less than the hot water storage temperature threshold, the first operation state. The exhaust heat recovery device for an engine according to claim 1 or 2, wherein the exhaust heat recovery device is switched to. The exhaust heat recovery circuit includes a hot water storage tank capable of storing the exhaust heat recovery medium,
An exhaust heat recovery medium supply path that guides the exhaust heat recovery medium that has passed through the exhaust heat recovery heat exchanger and is not stored in the hot water storage tank to the heat load terminal that generates a high temperature heat load in the exhaust heat recovery circuit; Prepared,
A switching valve for switching the flow of the exhaust heat recovery medium circulating in the exhaust heat recovery circuit to the flow through the exhaust heat recovery medium supply path,
When the high-temperature heat load presence determination means determines that there is a heat demand associated with a high-temperature heat load in the period from the present when the current or the exhaust heat recovery medium can suppress heat dissipation, the operation control means, 3. The engine exhaust heat recovery device according to claim 1, wherein the engine is switched to the second operation state and the switching valve is switched so as to guide the exhaust heat recovery medium to the exhaust heat recovery medium supply path. The present is a first setting period which is the setting period including the present time among time-series setting periods obtained by dividing a day by unit time,
5. The period from the present time at which heat dissipation of the exhaust heat recovery medium can be suppressed is a second set period that is the next set period subsequent to the first set period. 6. Engine exhaust heat recovery device. A thermal load storage unit that stores actual thermal load data in the set period for each set period;
The high temperature thermal load presence / absence determining means is configured to generate heat with a high temperature thermal load in the first setting period or the second setting period based on the past thermal load data in the setting period stored in the thermal load storage unit. The engine exhaust heat recovery apparatus according to claim 5, wherein a demand is predicted and whether or not there is a heat demand accompanied by a high-temperature heat load is determined based on the prediction.   The exhaust heat recovery apparatus for an engine according to any one of claims 1 to 6, wherein the heat demand accompanying the high temperature heat load is a heat demand accompanying a rise of a heating heat load terminal.

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