JPH0647973B2 - Exhaust heat recovery device for engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a device for recovering exhaust heat of an engine that drives a working device such as a generator or an air compressor for use in hot water supply or heating.

<< Prior Art >> As an example of an exhaust heat recovery device for an engine, USP4226
The one disclosed in Japanese Patent No. 214 is known.

As shown in FIG. 7, this is the exhaust heat absorber (3) whose engine heat source is engine cooling water derived from the water jacket (1) of the engine (E) that drives the generator (G). To the exhaust heat recovery device (4) to radiate heat to the heat absorbing liquid (water) supplied here, and lower the temperature by this heat dissipation. Store engine cooling water in the bottom of the engine
It is supplied to the heat absorbing part (13) installed in (12) to endothermicly cool the lubricating oil accumulated therein, and then the water pump (7)
The engine cooling water circulation flow path is configured to return to the water jacket (1) of the engine (E) via the heat exchanger, and the heat absorbing liquid heated by the heat absorption in the exhaust heat recovery device (4) is used for heating equipment or hot water supply. It is adapted to be guided to a heat load device (5) such as equipment.

Furthermore, the engine cooling water flow path on the inlet side of the exhaust heat recovery unit (4)
(m) and the engine cooling water flow path (n) on the outlet side are formed with a bypass flow path (o), and this bypass flow path is formed.
At the outlet of (o), when the engine cooling water temperature is low, the bypass flow path (o) is opened to circulate the engine cooling water from the exhaust heat absorber (3) without passing through the exhaust heat recovery device (4). The engine cooling water is made to flow and the temperature of the engine cooling water is quickly raised during the warm-up operation of the engine (E).

<Problems to be Solved by the Invention> However, in the above conventional configuration, when the heat load device (5) in which the required heat load fluctuates greatly is connected, the engine cooling water is greatly reduced when the required heat load is greatly reduced or eliminated. The heat dissipation is insufficient and the engine (E) is overheated, and it can be used only under the condition where the engine load and the required heat load are always balanced.

Therefore, in order to enable the use of the heat load device (5) in which the required heat load fluctuates greatly, a heat dissipation cooling water flow path using a radiator is provided in parallel with the engine cooling water circulation flow path for exhaust heat recovery. At the same time, a valve mechanism that switches between an exhaust heat recovery operation mode that guides the engine cooling water discharged from the exhaust heat absorber to the exhaust heat recovery device and a heat radiation operation mode that guides it to the radiator is provided, and this valve mechanism is also used. The applicant of the present invention has previously proposed a configuration including a control device that performs switching control based on the temperature detection of the endothermic liquid that emerges from the outlet of the.
In the proposed configuration, when the outlet temperature (T ₁ ) of the heat absorbing liquid is lower than the first set temperature (T _1L ), the exhaust heat recovery operation mode is set, and the outlet temperature (T ₁ ) is set to the first set temperature. (T _1L )
When the temperature becomes higher than the second set temperature (T _1H ), which is higher than that, the exit temperature (T ₁ ) of the liquid for heat absorption is controlled by switching to heat dissipation operation mode
_Was maintained within a range where the first set temperature (T _1L ) was the lower limit and the second set temperature (T _1H ) was the upper limit (see FIG. 6).

By performing the mode switching control as described above, it is possible to operate the engine without overheating by releasing heat to the liquid for absorbing the engine cooling water or the atmosphere according to the required load fluctuation of the heat load device. However, it has been found that when the engine is in the exhaust heat recovery operation mode under high load operation, the valve mechanism for switching the flow path may cause hunting.

In other words, in the high load operation state of the engine, the amount of exhaust heat generated is large, so the temperature of the engine cooling water supplied to the exhaust heat recovery device is considerably high, and therefore the heat absorbing liquid is rapidly heated. The outlet temperature immediately changes to the second set temperature.
(T _1H ) and above, the valve mechanism switches to the heat dissipation operation mode. As a result of stopping the heating of the heat absorbing liquid by this mode switching, the outlet temperature thereof falls below the first set temperature (T _1L ), the mode is switched to the exhaust heat recovery operation mode again, and this is repeated at short intervals. The so-called hunting phenomenon is brought about and the durability of the valve mechanism is reduced. This phenomenon is more likely to occur as the width of the outlet temperature of the endothermic liquid, that is, the difference (ΔT ₁ ) between the second set temperature (T _1H ) and the first set temperature (T _1L ) is smaller. It was

Therefore, by setting the temperature range (ΔT ₁ ) to be sufficiently large, it is possible to suppress hunting of the flow path switching valve mechanism.However, when the engine load is small, that is, When the amount of engine exhaust heat generated is relatively small, the endothermic liquid reaches or exceeds the second set temperature (T _1H ) which is the upper limit temperature, and after switching to the heat radiation operation mode, the first set temperature (lower set temperature) ( T _1L) takes a long time to around below, which another problem exhaust heat recovery efficiency is reduced occurs, the preset temperature range (△ T ₁₎ that excessively large waste heat It was not preferable as a recovery device.

The present invention has been made in view of such circumstances, and it is possible to improve the exhaust heat recovery efficiency when the engine load is low while suppressing the hunting of the flow path switching valve mechanism when the engine load is high. The purpose is to be able to achieve.

<< Means for Solving the Problem >> The characteristic configuration of the present invention for achieving the above-mentioned object is that the engine cooling water derived from the outlet (1a) of the water jacket (1) of the engine (E) is used as a heat source for the engine exhaust. After receiving the heat by supplying it to the exhaust heat absorber (3),
Guide to (4) and let the heat absorbing liquid supplied here radiate heat,
Equipped with an engine cooling water circulation channel for exhaust heat recovery that returns engine cooling water from the exhaust heat recovery device (4) to the water jacket inlet (1b) of the engine (E) via the water pump (7) In the engine exhaust heat recovery device, the engine cooling water discharged from the exhaust heat absorber (3) is used as a radiator.
The engine cooling water flow paths (a), (f), (g), and (d) for heat radiation, which are supplied to the suction side of the water pump (7) after being guided to (8), are provided, and the exhaust gas absorber ( Flow path switching means (SV ₁ ), () that can switch between the exhaust heat recovery operation mode that guides the engine cooling water discharged from 3) to the exhaust heat recovery device (4) and the heat dissipation operation mode that guides it to the radiator (8) SV ₂ ) is provided, and the flow path switching means (SV ₁ ) and (SV ₂ ) are such that the outlet temperature (T ₁ ) of the heat absorbing liquid that exits from the exhaust heat recovery device (4) is the first set temperature (TV). _1L ), it switches to the exhaust heat recovery operation mode, and the first set temperature (T _1L )
The engine load detected by the engine load detection means (11) is connected to the control device (10) so that it can be switched to the heat radiation operation mode when it becomes higher than the second set temperature (T _1H ).
The larger the (L) is, the lower the first set temperature (T _1L ) is in the control device (10).

<< Operation >> According to the above characteristic configuration, when the engine is in the high load operation state, the first set temperature (T _1L ) is set lower than that in the low load operation of the engine, so the outlet temperature (T ₁ ) becomes 1 set temperature
It takes a relatively long time until the exhaust heat recovery operation mode is switched below (T _1L ) and then the temperature is raised to the second set temperature (T _1H ) and switched to the heat dissipation operation mode.

Then, as the engine load becomes smaller, the first set temperature (T _1L ) becomes higher, and in this case, the outlet temperature (T ₁ ) becomes equal to or higher than the second set temperature (T _1H ) and then the heat radiation operation mode is switched to. , It takes a short time to switch to the exhaust heat recovery operation mode by lowering the temperature below the first set temperature (T _1L ), and because the amount of engine exhaust heat generated is small, the exhaust heat recovery operation mode releases heat. It takes time to switch to the mode.

<< Examples >> Hereinafter, some examples of the present invention will be described with reference to the accompanying drawings.

FIG. 1 shows an embodiment of the present invention, in which an engine (E) that uses gas as a fuel is directly connected to a generator (G) to drive it. The engine cooling water derived from the outlet (1a) of the water jacket (1) provided for this engine (E) is
It is supplied to the heat receiving part (3a) of the exhaust heat absorber (3) arranged on the upstream side of the muffler (2), and absorbs engine exhaust heat to raise the temperature. The engine cooling water heated here has a flow path (a) and
It is supplied to the exhaust heat recovery unit (4) via (b). Exhaust heat recovery device
In (4), there is provided a heat receiving part (4a) for supplying and circulating the heat absorbing liquid (water) from the hot water supply equipment (5) as a heat load device through the circulation pump (6). The liquid absorbs heat from the engine cooling water and is heated. Then, the engine cooling water whose temperature has been lowered by heat dissipation in the exhaust heat recovery unit (4) is guided to the electric water pump (7) through the flow paths (c) and (d), and then the water jacket (1). The engine (E) is cooled and supplied to the inlet (1b) of the water jacket (1b) by heat absorption while passing through the water jacket (1), and is sent out from the water jacket outlet (1a) again.
That is, the water jacket (1) and the exhaust heat absorber
Engine cooling water circulation passage for exhaust heat recovery in which the engine exhaust heat absorbed in (3) is absorbed by the heat absorbing liquid in the exhaust heat recovery device (4)
(a), (b), (c), and (d) are formed.

Also, the engine cooling water flow path on the lower side of the exhaust heat absorber (3)
A bypass channel (e) is formed between (a) and the suction side channel (d) of the water pump. This bypass channel (e)
At the inlet of, the flow passage (a) is closed while the temperature of the engine cooling water is lower than the set value, and the entire amount of cooling water is guided to the bypass flow passage (e). A thermo valve (TV) that closes e) and opens the flow path (a) is provided, and is configured to accelerate the temperature rise of the engine cooling water during warm-up operation immediately after the engine is started.

Further, a flow passage (f) for supplying engine cooling water to the radiator (8) is provided from the connection portion between the flow passage (a) and the flow passage (b), and the cooling water discharged from the radiator (8) is also provided. Is provided with a flow passage (g) for guiding the water to the suction side flow passage (d) of the water pump (7), and the inlet and outlet portions of the flow passages (b) and (f) are each provided with a solenoid valve (SV) having reverse characteristics. ₁ ) and (SV ₂ ) are provided respectively. These electromagnetic on-off valves (SV ₁ ) and (SV ₂ ) are connected to the control device (10) together with the drive motor (FM) of the radiator cooling fan (9), and the heat receiving part (4) of the exhaust heat recovery unit (4). 4a) of the heat absorption liquid flow path (h), (i), the detection signal from the temperature sensor (S ₁ ) provided in the flow path (i) on the outlet side (outlet temperature (T ₁ ) ), It is controlled as follows.

That is, when the outlet temperature (T ₁ ) detected by the temperature sensor (S ₁ ) is lower than the first set temperature (T _1L ), the solenoid on-off valve (SV ₁ ) is opened and the solenoid on-off valve (SV ₂ ) is closed. The engine cooling water discharged from the exhaust heat absorber (3) is sent to the exhaust heat collector (4) to heat the heat absorbing liquid, and the outlet temperature (T _{When 1} ) becomes equal to or higher than the second set value (T _1H ) which is higher than the first set temperature (T _1L ), the solenoid on-off valve (SV ₁ ) is closed and the solenoid on-off valve (SV ₂ ) is opened. The engine cooling water exiting the exhaust heat absorber (3) is sent to the radiator (8) and the fan motor (FM) is activated.
Is started, and the radiator 8 cools the engine cooling water by radiating heat. By performing such an operation based on the detection of the outlet temperature (T ₁ ), the temperature of the heat absorbing liquid in the hot water supply equipment (5) is within the range of the first and second set temperatures (T _1L ) (T _1H ). It is kept at.

More detailed operation is shown in the control flow chart of FIG. That is, when the operation is started, first, the detected outlet temperature (T ₁ ) is compared with the second set temperature (T _1H ) (step 1
#). In this case, if the outlet temperature (T ₁ ) is lower than the second set temperature (T _1H ), the exhaust heat recovery operation mode is entered, the recovery solenoid on-off valve (SV ₁ ) is opened, and the heat dissipation solenoid on-off valve is opened. (SV
₂ ) is closed and the engine cooling water discharged from the exhaust heat absorber (3) is guided to the exhaust heat recovery unit (4) (step 2 #) and the outlet temperature
Exhaust heat recovery operation until (T ₁ ) rises above the second set temperature (T _1H ).
(Steps 1 #, 2 #) are continued.

When the outlet temperature (T ₁ ) becomes higher than the 2nd set temperature (T _1H ), the heat dissipation operation mode is set, the solenoid on-off valve (SV ₁ ) is closed and the solenoid on-off valve (SV ₂ ) is opened, and the engine cooling water is the radiator. It is sent to (8) (step 3 #).

When the heat radiation operation mode is entered, the engine load (L) is detected by the engine load detecting means (11) (step 4 #), and the temperature range (ΔT) previously associated with the detected engine load (L) is detected. ₁ ) is set (step 5 #). This temperature range (ΔT ₁ ) is equal to the engine load as indicated by A in FIG.
It has been established that the increase in (L) will increase.
Temperature range set as above from the second set temperature (T _1H )
The value (T _1H −ΔT ₁ ) obtained by subtracting (ΔT ₁ ) is set as the first set temperature (T _1L ) in this case (step 6 #).

And the outlet temperature (T ₁ ) is the first determined in this way
The set temperature (T _1L ) is compared (step 7 #). here,
If the outlet temperature (T ₁ ) is equal to or higher than the first set temperature (T _1L ) (step 3 #), the heat dissipation operation mode is continued and the outlet temperature
If (T ₁ ) is lower than the first set temperature (T _1L ), step (1 #,
2 #) and the exhaust heat recovery operation mode is entered.

As described above, by controlling both solenoid on-off valves (SV ₁ ) and (SV ₂ ), the outlet temperature (T ₁ ) is lower than the first set temperature (T _1L )
The temperature is maintained within the range (hunting part in FIG. 3) having the set temperature (T _1H ) as the upper limit.

The engine load detection means (11) is an engine
(E) Position of the governor fuel metering member, engine
A means for linearly detecting the boost pressure (E), the engine exhaust pressure, the exhaust temperature, etc. by a sensor can be considered. or,
As another means, it is also possible to indirectly detect the engine load by detecting the temperature of the circulating fluid, one example of which is shown in FIG.

That is, the flow rate (Q) and the temperature (T ₂ ) of the engine cooling water supplied to the exhaust heat recovery unit (4) are measured by the flow rate sensor (S ₀ ) and the temperature sensor, respectively.
(S ₂ ) and the temperature (T ₃ ) of the engine cooling water discharged from the exhaust heat recovery device (4) is detected by the temperature sensor (S ₃ ) and the flow rate (Q)
And the direct temperature of the engine (E) by the inlet temperature (T ₂ ),
Further, an external thermal load is calculated from the inlet temperature (T ₂ ) and the outlet temperature (T ₃ ) and the engine load (L) is comprehensively calculated from these. A control flowchart using this engine load detection means is shown in FIG.

<< Effects of the Invention >> As described above, according to the present invention, the first set temperature, which is the lower limit of the outlet temperature, is corrected to be lower as the engine load increases. In the load operation, immediately after switching to the exhaust heat recovery operation mode, it is possible to prevent a phenomenon in which the outlet temperature immediately rises to the second set temperature and the flow path switching means hunts, and the exhaust heat recovery During engine low load operation where the amount of generation is small, the exhaust heat recovery operation mode can be set longer to perform efficient exhaust heat recovery.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an engine exhaust heat recovery apparatus according to the present invention, FIG. 2 is a control flow chart, and FIG. 3 is a diagram showing the relationship between engine load and set temperature.
FIG. 4 is a block diagram of another embodiment, and FIG. 5 is a control flowchart of another embodiment. Further, FIG. 6 is a diagram showing the relationship between the engine load and the set temperature in the proposed technique, and further in FIG.
The figure is a block diagram of a conventional example. (1) …… Water jacket, (1a) …… Exit, (1b)…
… Inlet, (3) …… exhaust heat absorber, (4) …… exhaust heat recovery unit, (7) ……
Water pump, (8) …… Radiator, (10) …… Control device, (11) …… Engine load detection means, (E) …… Engine, (a, f, g, d) …… Engine cooling water flow path , (SV ₁ , SV ₂ ) …… Flow path switching means, (T ₁ ) …… Outlet temperature, (T _1L )
…… First set temperature, (T _1H ) …… Second set temperature.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-63-160318 (JP, A) Actual opening 59-91572 (JP, U) Actual opening 57-158958 (JP, U)

Claims (1)

[Claims] 1. A water jacket (1) for an engine (E)
After the engine cooling water derived from the outlet (1a) of the engine is supplied to the exhaust heat absorber (3) that uses the engine exhaust as a heat source to receive heat, it is guided to the exhaust heat recovery unit (4) and supplied there. Exhaust heat recovery configured to radiate heat to the heat absorbing liquid and return the engine cooling water discharged from the exhaust heat recovery device (4) to the water jacket inlet (1b) of the engine (E) via the water pump (7) In the exhaust heat recovery system of the engine equipped with the engine cooling water circulation passage, the engine cooling water discharged from the exhaust heat absorber (3) is radiated.
The engine cooling water flow paths (a), (f), (g), and (d) for heat radiation, which are supplied to the suction side of the water pump (7) after being guided to (8), are provided, and the exhaust heat absorber ( Exhaust heat recovery operation mode and radiator (8) to guide engine cooling water discharged from 3) to exhaust heat recovery device (4)
Alternative switchable flow path switching unit in the radiating operation mode leading to (SV _1), provided with (SV _2), and the flow path switching unit _{(SV 1), (SV 2} ) is exhaust heat recovery device
The outlet temperature (T ₁ ) of the endothermic liquid from (4) is the first set temperature.
When it becomes lower than (T _1L ), it is switched to the exhaust heat recovery operation mode, and when it becomes higher than the second set temperature (T _1H ), which is higher than the first set temperature (T _1L ), it is switched to the heat radiation operation mode. ), And the control device (10) is provided with means for lowering the first set temperature (T _1L ) as the engine load (L) detected by the engine load detection means (11) increases. Exhaust heat recovery device for engine.