JPH02102354A - Exhaust heat recovery device for engine - Google Patents

Abstract

PURPOSE:To prevent the overheat of an engine by cooling the engine cooling water with a heat exchanger for recovery of the exhausted heat of the engine in the exhaust heat recovery cycle and radiating the exhausted heat with a radiator when the temperature of the cooling water is elevated over a preset temperature for the sake of the reduction of the radiated heat from the heat exchanger. CONSTITUTION:In the titled device, a water jacket 2 of an engine 1, a heat exchanger 3 for absorption of the exhausted heat and a heat exchanger 6 for recovery of the exhausted heat of the engine are connected successively in series circulatively. In this case, a radiator 9 is connected to the heat exchanger 6 in parallel, and a heat supplying path 7 for heat recovery and a heat radiating path 10 are connected to an engine cooling water path 11 freely switchable with a heat recovering valve 31 and a heat radiating valve 32. When the temperature T1 of the engine cooling water detected with a temperature sensor 13 is elevated over a preset temperature T1H for starting of the heat radiation the valves 31 and 32 are controlled so as to be closed and opened respectively, and when the temperature T1 is lowered below a preset temperature T1L (<T1H) for ending of the heat radiation the valves 31 and 32 are controlled so as to be opened and closed respectively.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention absorbs engine exhaust heat through engine cooling water using a water jacket and an exhaust heat absorption heat exchanger, and also absorbs the absorbed heat from the engine exhaust heat. This technology relates to an engine exhaust heat recovery device that recovers heat using a heat recovery heat exchanger, and can prevent engine overheating even when the exhaust heat recovery load is partial or no load.

(Prior Art) Conventionally, this type of engine exhaust heat recovery device is described in US Pat. No. 4,226,214.

As shown in FIG. 6, the engine 1 drives the generator G to supply electricity, and the exhaust heat of the engine 1 is recovered to an external heat load 100 such as a water heater. It is structured as follows.

That is, the water jacket 2 of the engine 1 is provided with the exhaust heat absorption path 4 of the exhaust heat absorption heat exchanger 3, the hot water channel 5, the heat recovery heat transfer path 7 of the engine exhaust heat recovery heat exchanger 6, and cold water. Road 8
By sequentially connecting the cold water channels 8 in a series circulation manner,
・Water jacket 2 ・Exhaust heat absorption path 4 and hot water channel 5
This constitutes the engine cooling water channel 101. The exhaust heat of the engine 1 is absorbed by the water tank jacket 2 and the exhaust heat absorption heat exchanger 3 through the engine cooling water of the engine cooling waterway 101, and the absorbed heat is absorbed by the engine exhaust heat recovery heat exchanger 6. External heat load 100 via the heat receiving path 38 of
It dissipates heat.

(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 Since the amount of heat radiated from 38 is reduced or eliminated, there is a problem that the temperature of the engine cooling water in the engine cooling water channel 101 increases, causing the engine 1 to overheat.

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 Problems) In order to achieve the above object, the present invention is characterized in that an exhaust heat recovery device is configured as follows.

For example, as shown in FIGS. 1 and 2, the water jacket 2 of the engine 1 is connected to the exhaust heat absorption path 4 of the exhaust heat absorption heat exchanger 3, the hot water channel 5, and the engine exhaust heat recovery heat exchanger 6. The heat transfer path 7 for heat recovery and the cold water channel 8 are serially connected in a circulating manner, and the engine cooling water is circulated to the engine cooling channel 11 consisting of the cold water channel 8, the water jacket 2, the exhaust heat absorption channel 4, and the hot water channel 5. In the engine exhaust heat recovery device configured by interposing the pump 20, the heat radiation path 10 of the radiator 9 is connected in parallel to the heat transfer path 7 for heat recovery of the engine exhaust heat recovery heat exchanger 6, and the engine cooling is performed. The heat transfer path 7 for heat recovery and the heat radiation path 10 are configured to be switchable and connectable to the water channel 11 by switching open/close of the heat recovery valve 31 and the heat radiation valve 32, and a temperature sensor is installed in the engine cooling water path 11. 13 is provided, and the heat recovery valve 3 is connected to the temperature sensor 13 via the valve switching control device 14.
The temperature sensor 13 detects the temperature of the engine cooling water passing through the engine cooling water passage 11, and the detected temperature T of the engine cooling water temperature is , when the set temperature for heat radiation start reaches T107 or higher, the valve switching control device 14 or the heat recovery valve 31 is closed and the heat transfer path 7 for heat recovery is closed.
At the same time, the heat radiation valve 32 is opened to open the heat radiation path 10, and the detected temperature T of the engine cooling water temperature is
, is lower than the set temperature for heat dissipation start T IH, which is lower than the set temperature T for heat dissipation end 1L, the heat dissipation valve 3
2 to close the heat radiation path 10, and open the heat recovery valve 31 to open the heat recovery heat transfer path 7, and set the temperature sensor 13 or the set temperature T for starting heat radiation. , 1. that's all,
Or, based on detecting that the temperature has become lower than the set temperature T1L for ending heat radiation, the valve switching control device 14 switches one of the heat recovery valve 31 and the heat radiation valve 32, which has been closed so far. After opening both valves 31 and 32, the other valve, which had been open before, is closed.

In the above case, to set the simultaneous opening time from when both the heat recovery valve 31 and the heat radiation valve 32 are opened to when one of the valves 31 and 32 is closed. Possible ways to do this include:

(1) An electric timer is provided in the valve switching control device 14,
By setting this electric timer to a predetermined time, the simultaneous valve opening time Δt is set.

(2) A pressure sensor 21 is provided on the discharge side of the engine coolant circulation pump 20, and the detected pressure P1 of the pressure sensor 21 increases or decreases as the engine coolant temperature changes during engine operation.
The valve switching control device 14 increases or decreases the simultaneous valve opening time Δt in accordance with the increase or decrease in . That is, as shown in FIG. 3, when the engine cooling water temperature is high and the detected pressure P1 is high, the simultaneous valve opening time Δt is lengthened, and when the engine cooling water temperature is low and the detected pressure P1 is low, the simultaneous valve opening time Δt is increased.
It shortens.

(3) As shown in FIG. 4, the detected pressure P1 of the pressure sensor 21 is at a predetermined pressure P during switching between recovery and heat radiation. The time when the pressure is higher than that is detected, and the time when the pressure is high is defined as the simultaneous valve opening time Δt.

(4) Of the pressure P1 detected by the pressure sensor 21,
The pressure before switching when only one of the heat recovery valve 31 and the heat radiation valve 32 is open is detected, and both the valves 3 and 32 are open.
Detects the pressure during switching when both valves 1 and 32 are open.

As shown in FIG. 5, the time during which the differential pressure P between the two is equal to or higher than a predetermined differential pressure ΔPo is defined as the simultaneous valve opening time Δt.

(Operation) The present invention operates as follows, as shown in FIGS. 1 and 2, for example.

The temperature of the engine cooling water is the set temperature for finishing heat radiation T 1L
In the period from 1 to 2, the heat recovery valve (heat recovery solenoid valve) 31 is opened and the heat radiation valve (heat radiation solenoid valve) 32 is closed until the temperature rises to the set temperature T for starting heat radiation. The cooling water flows through the cold water channel 8, the water jacket 2, the exhaust heat absorption path 4, and the heat transfer path 7 for heat recovery of the engine exhaust heat recovery heat exchanger 6.
It circulates along the route of

As a result, the exhaust heat of the engine 1 is radiated from the engine exhaust heat recovery heat exchanger 6 to the recovery liquid in the exhaust heat recovery path 45, thereby cooling the engine cooling water and preventing the engine 1 from overheating.

In this exhaust heat recovery state, the exhaust heat recovery load becomes partial load or no load, the amount of heat radiated from the heat receiving path 38 of the engine exhaust heat recovery heat exchanger 6 decreases, and the temperature of the engine cooling water starts to radiate heat. When the temperature rises to 1 or more (set temperature TI), the heat recovery valve (heat recovery solenoid valve) 31 closes and the heat radiation valve (heat radiation solenoid valve) 32 opens, and the engine cooling water flows into the cold water channel. 8・Water jacket 2・Exhaust heat absorption path 4
- Circulate through the heat radiation path 10 of the radiator 9. Thereby, 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.

At the time of switching between heat recovery and heat dissipation as described above, after opening one of the heat recovery valves 31 and the heat dissipation valve 32, which had been closed until then, and opening both valves 31 and 32, Since the configuration is such that the other valve that was previously open is closed, even if the time required to close one valve is shorter than the time required to open the other valve, the valves will be closed simultaneously. As a result, abnormal pressure increases due to water hammer do not occur in the engine cooling water circulation circuit. Thereby, the engine 1 can prevent engine cooling water from spewing out from the radiator cap, etc., and can prevent overheating due to insufficient cooling water.

(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 heat recovery valve opens and the heat radiation valve closes, and 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. , prevent engine 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 receiving path of the engine exhaust heat recovery heat exchanger decreases or disappears.
When the temperature of the engine cooling water rises to a temperature equal to or higher than the set temperature for starting heat radiation, the heat recovery valve closes and the heat radiation valve opens, radiating the exhaust heat from the engine from the heat radiation path of the radiator. Cools the engine coolant and prevents the engine from overheating.

Since the heat recovery valve and the heat radiation valve are prevented from being closed simultaneously at the time of switching between recovery and heat radiation, an abnormal pressure increase due to water leakage does not occur in the engine coolant circulation circuit. As a result, the engine can prevent engine cooling water from spewing out from the radiator cap, etc., and can prevent overheating due to insufficient cooling water.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

Fig. 1 shows an overall system diagram of the engine exhaust heat recovery device, in which an engine 1 operated with fuel gas drives a generator G to supply electric power, and the exhaust heat of the engine 1 is used by a water heater. It is configured to be recovered to an external heat load 100.

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

The water jacket 2 of the engine 1 is connected to the exhaust heat absorption path 4 of the exhaust heat absorption heat exchanger 3, the hot water channel 5, the heat recovery heat transfer path 7 of the engine exhaust heat recovery heat exchanger 6, and the cold water channel 8. The engine cooling water circulation pump 20 is interposed in the cold water channel 8 while being serially connected to each other in a serial circulation manner. This engine coolant circulation pump 20 is configured to be electric, and is driven by electric power from a battery 27. Further, the heat radiation path IO of the radiator 9 is connected in parallel to the heat transfer path 7 for heat recovery of the heat exchanger 6 for engine exhaust heat recovery. Cooling air is blown to the radiator 9 by an electric radiator fan 28. Note that a thermostatic valve 29 is provided on the downstream side of the exhaust heat absorption path 4 of the exhaust heat absorption heat exchanger 3, so that when the engine 1 is started cold, engine cooling water is transferred to the exhaust heat recovery heat exchanger 3. 6 and the radiator 9 are bypassed, and the temperature is rapidly raised to a steady state temperature.

The above-mentioned cold water channel 8, water jacket 2, exhaust heat absorption channel 4, and warm water channel 5 constitute an engine cooling water channel 11. A heat transfer path 7 for heat recovery and a heat radiation path 10 are configured to be switchable and connectable to the engine cooling water path 11 using a switching valve 12 . This switching valve 12 consists of two solenoid valves: a heat recovery solenoid valve 31 that is a heat recovery valve, and a heat radiation solenoid valve 32 that is a heat radiation valve.

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

Next, the exhaust heat recovery liquid circuit will be explained. This transfers the exhaust heat recovery liquid stored in the external heat load 100 to the recovery pump 37.
The heat is then returned 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 recovered liquid inlet path 41, and the recovered liquid outlet path 42 constitute an exhaust heat recovery path 45.

The configuration of the electric control device of the above-mentioned exhaust heat recovery device is as follows. In FIG. 1, reference numeral 40 denotes a control panel for inputting control power. In addition, the engine cooling water
A temperature sensor 13 is provided on the downstream side of the thermostatic valve 29 in the middle.

This temperature sensor 13 detects the temperature of engine cooling water and controls switching of the switching valve 12 via a valve switching control device 14.

That is, the detected temperature T of the engine cooling water temperature of the temperature sensor 13
1 becomes equal to or higher than the set temperature T1H for starting heat radiation, the valve switching control device 14 closes the heat recovery solenoid valve 31 and opens the heat radiation solenoid valve 32 to set the switching valve 12 to the heat recovery state. Switch from to the heat dissipation state. As a result, the heat transfer path 7 for heat recovery of the engine exhaust heat recovery heat exchanger 6 is closed, and the heat radiation path 10 of the radiator 9 is opened.

On the other hand, the detected temperature T of the engine cooling water temperature of the crystallinity sensor 13
, or when the set temperature for heat dissipation end T1L, which is lower than the set temperature for heat dissipation start TIH, is lower, the heat dissipation solenoid valve 3
2 is closed and the recovery solenoid valve 31 is opened to switch the switching valve 12 from the heat radiation state to the heat recovery state. As a result, the heat radiation path 10 of the radiator 9 is closed, and the heat transfer path 7 for heat recovery of the engine exhaust heat recovery heat exchanger 6 is opened.

By opening and closing both the solenoid valves 31 and 32 in this way, the temperature of the engine cooling water changes to the heat radiation start temperature T, H (90°C) and the heat radiation end temperature T1L, as shown in FIG. (82°C).

” When switching between heat recovery and heat dissipation, the heat recovery solenoid valve 31 and the heat dissipation solenoid valve 32 are both opened for a predetermined time using an electric timer attached to the valve switching control device 14. controlled.

That is, as shown in FIG. 2, in the recovery state, the heat recovery solenoid valve 31 is open and the heat radiation solenoid valve 32 is closed. When switching from the recovery state to the heat radiation state, the heat radiation solenoid valve 32 is first opened, and then, after the simultaneous valve time Δt has elapsed, the heat recovery solenoid valve 31 is closed. Furthermore, when switching from this heat dissipation state to the recovery state,
First, the heat recovery solenoid valve 31 is opened, and then, after the simultaneous valve time Δt has elapsed, the heat radiation solenoid valve 32 is closed.

As mentioned above, when switching between heat recovery and heat dissipation, the heat recovery solenoid valve 31 and the heat dissipation solenoid valve 32 are configured to open simultaneously for a set time, so water hammer can be prevented when switching, and the engine cooling water pressure can be prevented from rising abnormally.

Note that the means for setting the same time valve time Δt can be modified as shown in FIGS. 3 to 5, instead of the above-mentioned electric timer.

FIG. 3 shows a first modification. This is achieved by installing a pressure sensor 21 on the discharge side of the engine coolant circulation pump 20 (
(see Figure 1), the engine cooling water temperature is high and the detected pressure is P1.
When P1 is high, the simultaneous valve time Δt is lengthened, and when the engine cooling water temperature is low and the detected pressure P1 is low, the simultaneous valve time Δt is shortened. As a result, the simultaneous valve time Δt, or the minimum time required to prevent water hammer, is sufficient, and the delay in switching between heat recovery and heat radiation can be shortened.

FIG. 4 shows a second modification. This means that the pressure P detected by the pressure sensor 21 during switching between recovery and heat radiation is the predetermined pressure P. The delay in switching between recovery and heat radiation is shortened by detecting the time when the pressure is high and setting the time of the pressure high as the simultaneous valve time Δt.

FIG. 5 shows a third modification. This detects the pressure before switching when only one of the heat recovery valve 31 and the heat radiation valve 32 is open among the detected pressure P of the pressure sensor 21, and also detects the pressure before switching when only one of the heat recovery valve 31 and the heat radiation valve 32 is open. The pressure in the middle of switching when both valves 32 and 32 are open is detected, and the differential pressure Δ between these two is detected.
By setting the time during which P is equal to or higher than a predetermined pressure difference ΔPo as the simultaneous valve time Δt, the delay in switching between recovery and heat radiation is shortened.

Note that instead of switching between recovery and heat radiation using the temperature sensor 13 described above, it is also possible to perform the following switching. That is, as shown in FIG.
1 is provided with a temperature sensor 13, and the recovered liquid outlet path 4
2 is provided with another temperature sensor 43. One temperature sensor 13 controls the temperature of the engine cooling water, and the other temperature sensor 43 controls the temperature of the exhaust heat recovery liquid. In this case, for example, the detected temperature T of the engine cooling water is maintained between the set temperature T,H for the start of heat radiation (90°C) and the set temperature T,I, (82°C) for the end of heat radiation, and The detected temperature T of the heat recovery liquid is the set temperature T20 (80'C) for the start of heat radiation and the set temperature T2L (70'C) for the end of heat radiation.
It may be possible to control the temperature to maintain the temperature between 2°C and 2°C.

[Brief explanation of drawings]

1 to 5 show embodiments of the invention. FIG. 1 and FIG. 2 show one embodiment of the present invention. FIG. 1 is an overall system diagram, and FIG. 2 is a diagram showing changes over time in engine cooling water temperature and the opening and closing states of valves. FIGS. 3 to 5 are diagrams each showing a modification for setting the simultaneous amount valve time. FIG. 6 is an overall system diagram showing a conventional example. 20... Engine coolant circulation pump, 31 Heat recovery valve (heat recovery solenoid valve), 32... Heat radiation valve (heat radiation solenoid valve), T1... Detection temperature of engine cooling water temperature, T I) I・Set temperature for heat radiation start, T1L... Set temperature for heat radiation end. 1...Engine, 2...Water jacket, 3.
...Exhaust heat absorption heat exchanger, 4...Exhaust heat absorption path, 5.
...Hot water channel, 6...Heat exchanger for engine exhaust heat recovery, 7
... Solenoid valve for heat recovery, 8... Cold water channel, 9... Radiator, 10... Heat radiation path, 11... Engine cooling channel, 13... Temperature sensor, 14... Valve switching control Equipment, Figure 3, Figure 2

Claims (1)

[Claims] 1. The water jacket (2) of the engine (1) includes an exhaust heat absorption path (4) of the exhaust heat absorption heat exchanger (3), a hot water channel (5), and an engine exhaust heat recovery path. The heat transfer path (7) for heat recovery of the heat exchanger (6) and the cold water channel (8) are serially connected in a serial circulation manner, and the cold water channel (8), water jacket (2),
An engine cooling water circulation pump (20) is connected to an engine cooling water channel (11) consisting of an exhaust heat absorption channel (4) and a hot water channel (5).
In an engine exhaust heat recovery device configured by interposing
Heat transfer path for heat recovery of engine exhaust heat recovery heat exchanger (6)
7), the heat radiation path (10) of the radiator (9) is connected in parallel, and the heat transfer path (7) and the heat radiation path (10) for heat recovery are connected to the engine cooling water channel (11). Valve (31)
The engine cooling water channel (11) is provided with a temperature sensor (13), and the temperature sensor (13) is equipped with a valve switching control device (14). The heat recovery valve (31) and the heat dissipation valve (32) are linked to enable switchable opening/closing control through the heat recovery valve (31) and the heat radiation valve (32), and the temperature sensor (13) detects the temperature of the engine cooling water passing through the engine cooling water channel (11). If the detected temperature of the cooling water (T_1) exceeds the set temperature for starting heat radiation (T_1_H), the valve switching control device (14) closes the heat recovery valve (31). to close the heat transfer path (7) for heat recovery, and close the heat radiation valve (3).
2) Open the valve to open the heat radiation path (10), and set the temperature at which the detected cooling water temperature (T_1) is lower than the set temperature for heat radiation start (T_1_H) (T
_1_L) or less, the heat radiation valve (32) is closed to close the heat radiation path (10), and the heat recovery valve (31) is opened to close the heat recovery heat transfer path ( 7) is configured to open, and the temperature sensor (13) detects the set temperature for starting heat radiation (T_1_
H) or lower than the set temperature for ending heat radiation (T_1_L), the valve switching control device (14) switches between the heat recovery valve (31) and the heat radiation valve (32).
One of the valves (31) and (32), which had been closed, was opened and both valves (31) and (32) were once opened, and then the other valve, which had been open, was closed. Features: Engine exhaust heat recovery device.