JPH0694843B2 - Exhaust heat recovery device for engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Field of Industrial Application> The present invention absorbs exhaust heat of an engine through engine cooling water with a water jacket and an exhaust heat absorbing heat exchanger, and absorbs the absorbed heat from the engine. This is a technique for preventing engine overheat even when the exhaust heat recovery load is a partial load or no load, with respect to an engine exhaust heat recovery device that is recovered by a heat recovery heat exchanger.

<< Prior Art >> An exhaust heat recovery device for an engine of this type is conventionally described in US Pat. No. 4,226,214.

As shown in FIG. 4, the engine 1 drives a generator G to supply electric power, and exhaust heat of the engine 1 is recovered to an external heat load 100 such as a water heater. It is configured as follows.

That is, in the water jacket 2 of the engine 1, the exhaust heat absorption path 4 of the exhaust heat absorption heat exchanger 3, the hot water path 5, the heat recovery heat transfer path 7 of the engine exhaust heat recovery heat exchanger 6, and the chiller. 8
The cold water channel 8
・ Water jacket 2 ・ Exhaust heat absorption path 4 and hot water path 5
Constitutes the engine cooling water channel 101. The exhaust heat of the engine 1 is passed through the engine cooling water in the engine cooling water passage 101 to the water jacket 2 and the heat exchanger 3 for absorbing exhaust heat.
In addition to being absorbed, the absorbed heat is radiated to the external heat load 100 via the heat receiving path 38 of the engine exhaust heat recovery heat exchanger 6.

<< Problems to be Solved by the Invention >> In the above-mentioned conventional technology, when the exhaust heat recovery load of the external heat load 100 becomes a partial load or no load, the heat receiving path of the exhaust heat recovery heat exchanger 6 There is a problem that the temperature of the engine cooling water in the engine cooling water passage 101 rises and the engine 1 overheats because the amount of heat radiation from the 38 decreases or disappears.

An object of the present invention is to prevent engine overheating even when the exhaust heat recovery load is a partial load or no load.

<< Means for Solving the Problem >> The present invention is characterized in that the exhaust heat recovery device is configured as follows in order to achieve the above object.

For example, as shown in FIG. 1 and FIG. 2, the water jacket 2 of the engine 1 is provided with the exhaust heat absorption path 4, the hot water path 5, and the engine exhaust heat recovery heat exchanger 6 of the exhaust heat absorption heat exchanger 3. The heat recovery heat transfer path 7 and the cold water path 8 are connected in series in a serial circulation manner, and an exhaust heat recovery liquid inlet path 41 and an exhaust heat recovery liquid outlet path are connected to the heat receiving path 38 of the engine exhaust heat recovery heat exchanger 6. In an engine exhaust heat recovery device in which 42 is connected to form an exhaust heat recovery path 45, a heat recovery heat transfer path 7 of an engine exhaust heat recovery heat exchanger 6 and a heat dissipation path 10 of a radiator 9 are connected in parallel. Then, the heat recovery heat transfer passage 7 and the heat radiation passage 10 are switched and connected by the switching valve 12 to the engine cooling water passage 11 including the cold water passage 8, the water jacket 2, the exhaust heat absorption passage 4, and the hot water passage 5. The temperature sensor 13 is installed in the engine cooling water channel 11
The switching valve 12 is linked to the switching control device 14 via the valve switching control device 14 so that the switching valve 12 can be switch-controlled. The temperature sensor 13 detects the temperature of the engine cooling water passing through the engine cooling water passage 11. When the detected temperature T _{1 of the} water temperature becomes equal to or higher than the heat radiation start set temperature T _1H , the valve switching control device 14 switches the switching valve 12 from the heat recovery state to the heat radiation state to provide the heat recovery transfer. When the heat passage 7 is closed and the heat radiation passage 10 is opened, and the detected temperature T ₁ of the engine cooling water temperature is equal to or lower than the heat radiation end setting temperature T _1L lower than the heat radiation start setting temperature T _1H , The switching valve 12 is switched from the heat dissipation state to the heat recovery state, the heat dissipation path 10 is closed, and the heat recovery heat transfer path 7 is opened. Is provided with a means 47 for detecting the decrease in the amount of liquid to be sent, and the exhaust heat recovery liquid flowing in the exhaust heat recovery passage 45 When the liquid amount abnormally decreases or disappears, based on this being detected by the liquid supply amount decrease detecting means 47, the valve switching control device 14 is controlled to operate by giving priority to the command signal from the temperature sensor 13. In this way, the switching valve 12 is configured to be held in a heat radiation state.

As shown in FIG. 1, the following means is conceivable as the above-mentioned means 47 for detecting the decrease in the amount of delivered liquid.

(1) A device for detecting whether or not the recovery pump 37 for the exhaust heat recovery liquid in the exhaust heat recovery passage 45 is in an operating state.

(2) Detection pressure P _S of the pressure sensor 49 provided in the exhaust heat recovery passage 45
Due to.

(3) Flow rate F _S detected by the flow rate sensor 50 provided in the exhaust heat recovery passage 45
Due to.

(4) A temperature sensor 51 for detecting the liquid temperature of the exhaust heat recovery liquid in the heat receiving path 38 of the engine exhaust heat recovery heat exchanger 6 is provided to determine whether the amount of the exhaust heat recovery liquid sent is abnormally reduced or eliminated. In case,
It utilizes that the temperature of the exhaust heat recovery liquid that stays in the heat receiving passage 38 or flows only in a small amount rises due to the heat received from the engine cooling water.

<< Operation >> The present invention operates as follows, for example, as shown in FIG. 1 and FIG.

During the period in which the temperature of the engine cooling water rises from the heat radiation end set temperature T _1L to the heat release start set temperature T _1H , the switching valve 12 is switched to the heat recovery state, and the engine cooling water is cooled by the cooling water passage 8. The water jacket 2, the exhaust heat absorption path 4, and the heat recovery heat transfer path 7 of the engine exhaust heat recovery heat exchanger 6 circulate. As a result, the exhaust heat of the engine 1 is radiated from the engine exhaust heat recovery heat exchanger 6 to the recovered liquid in the exhaust heat recovery passage 45 to cool the engine cooling water and prevent the engine 1 from overheating.

In this exhaust heat recovery state, the exhaust heat recovery load becomes a partial load or no load, the amount of heat released from the heat receiving path 38 of the engine exhaust heat recovery heat exchanger 6 decreases, and the temperature of the engine cooling water begins to release heat. When the temperature rises above the set temperature T _1H for the engine, the switching valve 12 is switched to the heat radiating state, and the engine cooling water is routed through the cold water passage 8, the water jacket 2, the exhaust heat absorption passage 4, and the radiator 9 heat radiation passage 10. Circulate. As a result, the exhaust heat of the engine 1 is radiated from the heat radiation path 10 of the radiator 9 to cool the engine cooling water and prevent the engine 1 from overheating.

Further, when the amount of the exhaust heat recovery liquid flowing through the exhaust heat recovery passage 45 abnormally decreases or disappears during the operation of the exhaust heat recovery device, the liquid transfer amount decrease detecting means 47 is used. On the basis of the detection by the temperature sensor 13, the control signal for the valve switching control device 14 is prioritized over the command signal from the temperature sensor 13, and the switching valve 12 is held in the heat radiation state. It is possible to prevent hunting from occurring when switching to the heat recovery state.

That is, by only switching the switching valve 12 between the heat recovery state and the heat radiation state only by the command signal from the temperature sensor 13,
When the amount of the exhaust heat recovery liquid delivered abnormally decreases or disappears during operation in the heat recovery state, the amount of heat released from the engine exhaust heat recovery heat exchanger 6 abnormally decreases or disappears, so engine cooling is performed. The water temperature of the water rises rapidly to reach the heat radiation start set temperature T _1H or higher in a short time, and the switching valve 12 is switched from the heat recovery state to the heat radiation state. In this heat dissipation state, the engine cooling water is cooled by the radiator 9 and rapidly drops to a temperature equal to or lower than the heat dissipation end set temperature T _1L, so that the switching valve 12 heats up from the heat dissipation state in a short time. It is switched to the recovery state. Then, the switching valve 12 is switched from the heat recovery state to the heat dissipation state again within a short time due to insufficient heat dissipation of the engine exhaust heat recovery heat exchanger 6 due to the abnormal reduction of the exhaust heat recovery liquid or water interruption. By repeating this, hunting of the switching valve 12 occurs.

According to the present invention, when the transfer amount of the exhaust heat recovery liquid abnormally decreases or disappears, if the switching valve 12 is in the heat recovery state, it is switched to the heat dissipation state, and the switching valve 12 releases the heat. Since it is controlled so that the heat radiation state is maintained as it is in the usage state, the above hunting can be prevented.

<< Effects of the Invention >> The present invention has the following effects because it is configured and operates as described above.

In the exhaust heat recovery state, the switching valve is switched to the recovery state,
The engine exhaust heat is radiated from the heat receiving path of the engine exhaust heat recovery heat exchanger to cool the engine cooling water and prevent the engine from overheating.

In this exhaust heat recovery state, the exhaust heat recovery load becomes a partial load or no load, and the amount of heat released from the heat receiver of the engine exhaust heat recovery heat exchanger decreases or disappears, depending on the temperature of the engine cooling water. When the temperature rises above the set temperature for heat radiation, the switching valve is switched to the heat radiation state, radiating the exhaust heat of the engine from the radiator's heat radiation path to cool the engine cooling water and prevent engine overheating. .

During operation of the above-mentioned exhaust heat recovery device, if the amount of exhaust heat recovery liquid to be sent is abnormally reduced or eliminated, if the switching valve is in the heat recovery state, switch it to the heat dissipation state,
When the switching valve is in the heat dissipation state, the heat dissipation state is maintained as it is, so that hunting can be prevented from occurring in switching between the heat recovery state and the heat dissipation state.

Therefore, since the switching valve does not frequently switch, wear of the valve seat and the valve surface is prevented, and the service life is extended.

Further, since the frequent switching between the heat radiation state and the heat recovery state does not occur, the temperature change range of the engine cooling water can be small. Therefore, the cylinder of the engine and the heat exchanger for absorbing exhaust heat need less thermal fatigue, and the durability is improved.

«Examples» Examples of the present invention will be described below with reference to the drawings.

FIG. 1 is an overall system diagram of an exhaust heat recovery system for an engine, in which an engine 1 driven by fuel gas drives a generator C to supply electric power, and exhaust heat of the engine 1 consists of a water heater. The external heat load 100 is configured to be recovered.

First, the cooling water circuit of the engine 1 will be described.

In the water jacket 2 of the engine 1, the exhaust heat absorption path 4, the hot water path 5, the heat recovery heat transfer path 7 of the engine exhaust heat recovery heat exchanger 6, and the cold water path 8 of the exhaust heat absorption heat exchanger 3 are provided. The engine cooling water circulation pump 20 is installed in the cold water passage 8 while being connected in series and connected in series. The engine cooling water circulation pump 20 is electrically driven and is driven by the electric power of the battery 27. Further, the heat recovery heat transfer path 7 of the engine exhaust heat recovery heat exchanger 6 is connected to the heat dissipation path 10 of the radiator 9.
Are connected in parallel. Cooling air is blown to the radiator 9 by an electric radiator fan 28. A thermostat valve 29 is provided on the downstream side of the exhaust heat absorption path 4 of the exhaust heat absorption heat exchanger 3, and when the engine 1 is cold-started, the engine cooling water collects the engine exhaust heat recovery heat exchanger. 6
Also, the radiator 9 is bypassed and the temperature is rapidly raised to a steady temperature.

The cold water channel 8, the water jacket 2, the exhaust heat absorption channel 4, and the warm water channel 5 constitute an engine cooling water channel 11. The heat recovery heat transfer passage 7 and the heat radiation passage 10 are configured to be switchably connectable to the engine cooling water passage 11 by a switching valve 12. This switching valve 12 includes a heat recovery solenoid valve 31 and a heat radiation solenoid valve.
It consists of two solenoid valves with 32.

On the other hand, the exhaust gas of the engine 1 is discharged from the muffler 35 to the outside through the exhaust gas flow path 34 of the heat exchanger 3 for absorbing exhaust heat.

Next, the circuit of the exhaust heat recovery liquid will be described. In this system, the exhaust heat recovery liquid stored in the external heat load 100 is returned from the recovery pump 37 to the external heat load 100 via the heat receiving path 38 of the engine exhaust heat recovery heat exchanger 6. The heat receiving path 38, the exhaust heat recovery liquid inlet path 41, and the exhaust heat recovery liquid outlet path 42 form an exhaust heat recovery path 45.
Is configured.

The structure of the electric control device of the above-mentioned exhaust heat recovery device is as follows. In FIG. 1 of the above, reference numeral 40 is a control panel for inputting control power. Further, a temperature sensor 13 is provided on the downstream side of the thermostat valve 29 in the middle of the engine cooling water passage 11, and a temperature sensor 43 is provided in the exhaust heat recovery liquid outlet passage 42.
Is provided. The temperature sensors 13, 43, respectively, detects the detected temperature T ₂ of the detected temperature T _1, the exhaust heat recovery liquid of the engine cooling water, so that switching control of the switching valve 12 via a valve switching control unit 14 It has become. Further, the exhaust heat recovery passage 45 is provided with a means 47 for detecting a decrease in the amount of the exhaust heat recovery liquid to be sent. The liquid feed amount decrease detection means 47 controls the valve switching control device 14 by prioritizing the command signal from the temperature sensor 13 based on electrically detecting whether or not the recovery pump 37 is operating. In this way, the switching valve 12 is held in the heat radiation state.

The control device described above is adapted to execute the control program shown in FIG.

When the exhaust heat recovery device starts operating (S1), the recovery pump 37
Is determined to be operating (S2), and if it is in the operating state, the detected temperature T ₁ of the engine cooling water is the set temperature T for starting heat radiation.
_It is determined whether it is lower than _1H (here 90 ° C) (S
3). If the temperature is lower than the set temperature T _1H (90 ° C), the detected temperature T ₂ of the recovered liquid is the set temperature T _2H (80
C)) is determined (S4). Set temperature T
_{When the} temperature is lower than _2H (80 ° C), the switching valve 12 is switched to the heat recovery state (S5), and is returned to the stage of S2.

If the recovery pump 37 is not operating in the step S2, the detected temperature T ₁ of the engine cooling water is equal to or higher than the set temperature T _1H (90 ° C) in the step S3, the detected temperature of the recovered liquid in the step S4. When T ₂ is equal to or higher than the preset temperature T _2H (80 ° C) for heat radiation, the switching valve 12 is switched to the heat radiation state (S
6). Next, it is determined whether the recovery pump 37 is in operation (S7). In the case of operation, it is determined whether the detected temperature T ₁ of the engine cooling water is equal to or lower than the heat radiation end set temperature T _1L (here, 82 ° C.). Is determined (S8). If the set temperature is less than T _1L (82 ℃), the detected temperature T ₂ of the recovered liquid is the set temperature for ending heat dissipation.
It is determined whether the temperature is T _2L (72 ° C in this case) or lower (S9).
If the temperature is lower than the set temperature T _2L (72 ℃), the process returns to the step S2.

If the recovery pump 37 is not operating in the above step S7, and if the detected temperature T ₁ of the engine cooling water is higher than the heat radiation end set temperature T _1L (82 ° C) in the step S8, the recovery liquid in the step S9 The detected temperature T ₂ of the
If the temperature is higher than _2L (72 ℃), it is returned to the stage of S6 and kept in the heat dissipation state.

With this configuration, the switching valve 12 including both solenoid valves 31 and 32
By switching between the heat recovery state and the heat radiation state, as shown in Fig. 3, the engine cooling water temperature is set to heat radiation start temperature _T1H (90 ° C) and heat radiation end temperature _T1L.
(82 ℃) and the temperature of the recovered liquid is
Heat dissipation start set temperature T _2H (80 ℃) and heat release end set temperature T
_Keep between _2L (72 ℃). As a result, the engine cooling water can be kept within a certain range to prevent overheating of the engine 1, and the recovered liquid can be taken out at a desired temperature within a certain range regardless of the load fluctuation of the external heat load 100.

Further, since the exhaust heat recovery device is switched to the heat radiation state and kept in that state when the recovery pump 37 is not in the operating state, even if the engine cooling water is cooled by the radiator 9 and the temperature drops, it is switched to the recovery state. It will not be replaced. As a result, when the recovery pump 37 is stopped, frequent switching between the heat radiation state and the heat recovery state is eliminated.

The lowermost liquid feeding detecting means 47 can be modified as follows instead of detecting the operating state of the recovery pump 37 (see FIG. 1).

(First Modification) A pressure sensor 49 is provided at the exhaust heat recovery liquid outlet passage 42 of the exhaust heat recovery passage 45, and the amount of the exhaust heat recovery liquid sent is abnormally reduced or eliminated at the detection pressure P _S of the pressure sensor 49. If a command signal is output,

(Second Modification) The exhaust heat recovery liquid outlet passage 42 of the exhaust heat recovery passage 45 is provided with the flow rate sensor 50, and the detected flow rate F _S of the flow rate sensor 50 causes the amount of exhaust heat recovery fluid to be abnormally reduced or eliminated. If a command signal is output,

(Third Modification) A temperature sensor 51 for detecting the liquid temperature of the exhaust heat recovery liquid in the heat receiving passage 38 of the engine exhaust heat recovery heat exchanger 6 is provided to determine whether the amount of the exhaust heat recovery liquid sent is abnormally reduced. In case of disappearing, heat receiving path
A command signal is issued by utilizing the fact that the exhaust heat recovery liquid that stagnates or flows in a small amount inside the 38 rises in temperature due to the heat received from the engine cooling water.

In order to prevent hunting for switching between recovery and heat dissipation when the amount of exhaust heat recovery liquid sent is abnormally reduced or eliminated, the temperature control of the exhaust heat recovery liquid is controlled by the exhaust heat recovery liquid outlet path 42.
It is also possible to use the above temperature sensor 51 instead of the temperature sensor 43. That is, the temperature T ₃ detected by the temperature sensor 51 in the heat receiving path 38 is determined by the heat transfer from the engine cooling water in the heat recovery state even when the amount of the exhaust heat recovery liquid sent is abnormally reduced or eliminated. It is difficult for the temperature to drop. Therefore, it is possible to secure a sufficient time for the temperature to drop to the heat radiation end set temperature (72 ° C.), and the heat radiation state is maintained for a relatively long time, so that frequent switching can be prevented.

Further, switching between the heat recovery state and the heat radiation state is performed when it is not necessary to keep the temperature of the exhaust heat recovery liquid within a predetermined temperature range.
It is also possible to omit the temperature sensor 43 and use only the temperature sensor 13.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention, FIG. 1 is an overall system diagram, FIG. 2 is a control program diagram, and FIG. 3 is a diagram showing temperature changes of engine cooling water and recovered liquid. . FIG. 4 is an overall system diagram showing a conventional example. 1 ... Engine, 2 ... Water jacket, 3 ... Exhaust heat absorption heat exchanger, 4 ... Exhaust heat absorption path, 5 ... Hot water path, 6 ... Engine exhaust heat recovery heat exchanger, 7 ... … Heat recovery heat transfer channel, 8 …… Cold water channel, 9 …… Radiator, 10 …… Radiation channel, 11 …… Engine cooling water channel, 12 …… Switching valve, 13 …… Temperature sensor, 14 …… For valve switching controller, 38 ...... heat-receiving passage, 41 ...... exhaust heat recovery fluid inlet passage, 42 ...... exhaust heat recovery fluid outlet passage, 45 ...... exhaust heat recovery passage, 47 ...... feed rate reduction detector, T ₁ ... … Detected temperature of engine cooling water temperature, T _1H …… Set temperature for starting heat dissipation, T _1L …… Set temperature for ending heat dissipation.

Claims (1)

[Claims] 1. A water jacket (2) of an engine (1) is provided with an exhaust heat absorption path (4), a hot water path (5) and an engine exhaust heat recovery heat exchanger of an exhaust heat absorption heat exchanger (3). The heat recovery heat transfer path (7) and the cold water path (8) of (6) are connected in series in a serial circulation manner, and exhaust heat is transferred to the heat reception path (38) of the engine exhaust heat recovery heat exchanger (6). A heat exchanger (6) for recovering exhaust heat of an engine in an exhaust heat recovery apparatus for an engine, wherein an exhaust heat recovery path (45) is formed by connecting a recovered liquid inlet path (41) and an exhaust heat recovered liquid outlet path (42). The heat radiation path (7) for heat recovery of the radiator is connected with the heat radiation path (10) of the radiator (9) in parallel to form a cold water path (8), a water jacket (2), an exhaust heat absorption path (4), and hot water. Heat recovery heat transfer path (7) and heat dissipation path (10) for engine cooling water path (11) consisting of path (5)
And the switch valve (12) are switchably connectable, the engine cooling water passage (11) is provided with a temperature sensor (13), and the temperature sensor (13) is provided with a valve switching control device (14). The temperature sensor (13) detects the temperature of the engine cooling water passing through the engine cooling water channel (11), and detects the engine cooling water temperature (T ₁ ) _Becomes equal to or higher than the heat radiation start set temperature (T _1H ), the valve switching control device (14) switches the switching valve (12) from the heat recovery state to the heat radiation state to recover the heat. The heat transfer path (7) is closed and the heat dissipation path (10) is opened, and the detected temperature (T ₁ ) of the engine coolant temperature is lower than the heat dissipation start setting temperature (T _1H ). (T _1L )
When the following occurs, the switching valve (12) is switched from the heat radiation state to the heat recovery state to close the heat radiation path (10) and open the heat recovery heat transfer path (7). The exhaust heat recovery passage (45) is provided with a means for detecting a decrease in the amount of exhaust heat recovery liquid (47), and the amount of exhaust heat recovery liquid flowing in the exhaust heat recovery passage (45) is abnormally reduced. In the case of disappearance, it is based on the fact that the liquid feed amount decrease detecting means (47) detects this.
The engine is characterized in that the valve switching control device (14) is controlled and operated by giving priority to the command signal from the temperature sensor (13) to hold the switching valve (12) in a heat radiating state. Exhaust heat recovery device.