JPH08338310A - Exhaust heat recovery system - Google Patents

Abstract

PURPOSE: To prevent the generation of overshoot due to an increase in exhaust heat demand amt. at an exhaust heat recovery part without affected by secular change or a variation in flow resistance. CONSTITUTION: A rapid decrease in exhaust heat demand amt. such as sudden suspension of warm water-absorption type refrigerator operation, etc., is detected from the temp. of cooling water supplied to a heat exchanger for heat radiation by means of an input temp. sensor 16. A control output of 30% is generated from feed forward side control means 22. Control output from a feedback side control means 23 is added to the 30%-control output. The added control output controls a three-way valve 12. Cooling water having some previously set amt., not the total amt. of the cooling water, is supplied to the heat exchanger for heat radiation. When exhaust heat recovery is restarted, the control output from the feed forward side control means 22 is retained to 30% by means of a cooling water temp. sensor 15 until the temp. of the cooling water returned to an engine cooling part becomes set temp. or below. Thus, returning the high-temp. cooling water due to overshoot to the engine cooling part is avoided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an engine cooling section such as a cooling jacket for a gas engine or a diesel engine, for use in a cogeneration system or the like.
While connecting the exhaust heat recovery part of the hot water absorption refrigerator, hot water supply equipment, heating device, etc. via piping, connect the three-way valve and the bypass pipe to the cooling water supply side piping from the exhaust heat recovery part to the engine cooling part. Is provided with a heat dissipation heat exchanger having a heat dissipation amount changing means, and the temperature of the cooling water is measured between the exhaust heat recovery part of the cooling water supply side pipe and the heat dissipation heat exchanger. The present invention relates to an exhaust heat recovery system that is provided with an inlet temperature sensor and operates a heat radiation amount changing means based on the temperature of cooling water measured by the inlet temperature sensor.

[0002]

2. Description of the Related Art In an exhaust heat recovery system, a cooling water temperature sensor for measuring the temperature of cooling water to be supplied to an engine cooling section is usually provided downstream of a bypass pipe of a cooling water supply side pipe, and the cooling water is also provided. Provided with feedback side control means for operating the heat radiation amount changing means so that the temperature of the cooling water measured by the temperature sensor becomes the set temperature, so that the temperature of the cooling water supplied to the engine cooling section becomes the set temperature. The amount of cooling water distributed and supplied to the heat dissipation heat exchanger is controlled. As a result, it is possible to avoid the occurrence of so-called engine trip in which the temperature of the cooling water in the cooling jacket rises too much and the engine protection circuit operates to automatically stop the engine.

[0003]

However, in the conventional example, when the exhaust heat demand suddenly decreases, such as when the hot water absorption refrigerator suddenly stops, for example, a three-way valve is used in the wake. Even if a heat radiating heat exchanger is installed to lower the water temperature, the heat radiating heat exchanger does not take enough heat due to the control delay when the water temperature rises rapidly, and the cooling water temperature overshoots the set temperature. , Hot cooling water returns to the engine and the engine trips.

Therefore, the set temperature is lowered in anticipation of the maximum temperature due to overshoot. However, there is a drawback that the temperature of the cooling water taken out from the engine cooling section becomes low during normal times, and the exhaust heat recovery efficiency decreases.

Therefore, as described at the beginning, the temperature of the cooling water discharged from the exhaust heat recovery section is measured by the inlet temperature sensor, and the feed for operating the heat radiation amount changing means such as a three-way valve based on the measured temperature. It has been proposed to perform forward control and activate a heat radiation amount changing means at an early stage to prevent overshoot.

However, in the case of performing the feedforward control, when the exhaust heat demand suddenly decreases, the inlet temperature sensor senses the temperature rise of the cooling water and activates the heat radiation amount changing means early to perform the heat radiation heat exchange. Although it can be dealt with to increase the heat radiation amount in the refrigerator, conversely, the exhaust heat demand increases, such as restarting the operation of the hot water absorption refrigerator after the exhaust heat demand is decreasing. In this case, if the inlet temperature sensor detects that the temperature of the cooling water has dropped and activates the heat radiation amount changing means to reduce the heat radiation amount in the heat radiation heat exchanger, the heat radiation heat exchanger releases heat. However, there was a problem that the cooling water, which was still at high temperature, was returned to the engine cooling section to cause overshoot.

Therefore, in order to solve such a problem,
It is conceivable to calculate the time required for the low-temperature cooling water measured by the inlet temperature sensor to reach the location controlled by the heat radiation amount changing means, and continue heat radiation in the heat radiation heat exchanger for that time. Was given.

The time required for the cooling water to reach the location controlled by the heat radiation amount changing means is calculated from the inner diameter of the pipe and the flow velocity of the cooling water flowing therethrough. However, there is a possibility that the inner diameter of the pipe may change over time due to the scale being attached to the inner peripheral surface of the pipe due to use. Further, the flow velocity fluctuates due to the change in flow resistance in the entire system due to the operation or stop of the exhaust heat recovery unit.

For this reason, it is difficult to properly set the delay time over a long period of time, and there is a drawback that the control delay time is incorporated into the control configuration, which causes a cost increase, and further improvement is desired. It was rare.

The present invention has been made in view of the above circumstances, and the exhaust heat recovery system of the invention according to claim 1 recovers the exhaust heat without being affected by aged deterioration or flow resistance change. The purpose of the present invention is to prevent the occurrence of overshoot due to an increase in the exhaust heat demand in the exhaust heat recovery section, and the exhaust heat recovery system of the invention according to claim 2 is to exhaust the exhaust heat in the exhaust heat recovery section. An object of the present invention is to prevent the control from becoming unstable due to an operation delay at the start of heat recovery.

[0011]

The invention according to claim 1 is
In order to achieve the above purpose, the engine cooling part of the engine (1) and the exhaust heat recovery parts (6), (7) are connected to the pipes (5), (8a),
Connected via (8b) and exhaust heat recovery parts (6), (7)
From the engine cooling section to the cooling water supply side pipe (5) is provided with a heat dissipation heat exchanger (14) equipped with heat dissipation amount changing means (12), and the cooling water supply side pipe (5) exhaust heat An inlet temperature sensor (16) for measuring the temperature of the cooling water is provided between the recovery sections (6), (7) and the heat dissipation heat exchanger (14), and cooling is performed by the inlet temperature sensor (16). In the exhaust heat recovery system configured to operate the heat radiation amount changing means (12) based on the water temperature, the cooling water supply side pipe (5) is provided on the downstream side of the heat radiation heat exchanger (14). Cooling water temperature sensor (15) that measures the temperature of the cooling water returned to the engine cooling unit, and cooling based on the heat radiation signal output when the temperature measured by the inlet temperature sensor (16) exceeds the set temperature. Hold means (21) that outputs a heat radiation control signal until the temperature measured by the water temperature sensor (15) is lower than the set temperature, and heat radiation control signal When the engine (1) is in rated operation with the valve opening of the heat radiation amount changing means (12) and the exhaust heat demand of the exhaust heat recovery parts (6), (7) is zero in response to the A feed-forward side control means (22) for controlling to a preset valve opening smaller than the valve opening for flowing the amount of cooling water to be supplied to the heat dissipation heat exchanger (14), and a cooling water temperature sensor ( Based on the measured temperature of the cooling water by 15), it comprises a feedback side control means (23) for controlling the heat radiation amount changing means (12) so that the heat radiation amount increases as the measured temperature rises.

As the exhaust heat recovery unit, a hot water absorption type refrigerator, hot water supply equipment, a heating device or the like is used.

Further, the exhaust heat recovery system of the invention according to claim 2 has the following features to achieve the above object.
Hold means in the exhaust heat recovery system of the invention according to (2)
1), the measured temperature of the cooling water by the inlet temperature sensor (16) is lower than the set temperature (A), and the measured temperature of the cooling water by the cooling water temperature sensor (15) is the set temperature (B). The heat radiation control signal is output until the temperature becomes lower than that.

[0014]

According to the constitution of the exhaust heat recovery system of the invention as claimed in claim 1, when the exhaust heat demand amount in the exhaust heat recovery portion is suddenly reduced, the cooling water whose temperature is rapidly increased by the inlet is introduced. When the temperature sensor detects it, it outputs a heat radiation signal, and based on that, it outputs a heat radiation control signal from the hold means, and in response to the heat radiation control signal, the feedforward side control means activates the heat radiation amount changing means, Is set to a small value, and the cooling water is supplied to the heat radiation heat exchanger in an amount smaller than the total amount. On the other hand, in the feedback side control means, based on the measured temperature of the cooling water temperature sensor, if the measured temperature becomes high, the amount supplied to the heat radiating heat exchanger increases, and conversely, if the measured temperature becomes low. The heat radiation amount changing means is operated so that the amount of heat supplied to the heat radiation heat exchanger is reduced. That is,
The heat radiation amount changing means is operated by the control output of the entire system in which the control output from the feedforward side control means and the control output from the feedback side control means are added. Then, when the exhaust heat recovery in the exhaust heat recovery unit is restarted, it is determined that the measured temperature of the cooling water by the cooling water temperature sensor is lower than the set temperature,
Based on this, the action of the holding means is released, and the cooling water is not supplied to the heat radiating heat exchanger only by the control output from the feedforward side control means, but from the feedback side control means based on the temperature measured by the cooling water temperature sensor. Control output is added to operate the heat radiation amount changing means so that the temperature measured by the cooling water temperature sensor does not exceed the set temperature. More specifically, when the exhaust heat demand in the exhaust heat recovery unit is stable and the temperature change of the cooling water returned to the engine cooling unit is small, the feedback side based on the temperature of the cooling water returned to the engine cooling unit The addition of the control output from the control means effectively acts to control the amount of cooling water supplied to the heat radiating heat exchanger. For example, when the exhaust heat demand at the exhaust heat recovery unit is suddenly reduced, such as when the operation of the hot water absorption refrigerator is stopped, the fact that the temperature of the cooling water measured by the inlet temperature sensor indicates the set temperature When the temperature exceeds the limit, the holding means acts to supply a predetermined amount (set amount) of cooling water to the heat radiation heat exchanger instead of the total amount of cooling water required to radiate the required amount. ,
Avoid returning cooling water that has suddenly increased in temperature to the engine cooling section, and supply cooling water that has not risen to the heat radiation heat exchanger more than necessary to keep it cooler than necessary. It suppresses returning to the engine cooling part, and
In the range exceeding the set amount, the amount of cooling water supplied to the heat radiation heat exchanger so that the temperature of the cooling water returned to the engine cooling unit does not exceed the set temperature due to the addition of the control output from the feedback side control means. To control. Further, when the exhaust heat recovery in the exhaust heat recovery section is restarted, the operation of the holding means is canceled after a delay from the restart time,
By the action of the addition of the control output from the feedback side control means based on the temperature measured by the cooling water temperature sensor, the temperature of the cooling water returned to the engine cooling unit is supplied to the heat radiation heat exchanger so as not to exceed the set temperature. Control the amount of cooling water.

According to the structure of the exhaust heat recovery system of the second aspect of the invention, in addition to the fact that the holding means releases the action, the temperature measured by the cooling water temperature sensor becomes lower than the set temperature. The temperature measured by the inlet temperature sensor becomes lower than the set temperature. For example, when restarting the exhaust heat recovery in the exhaust heat recovery unit, the low-temperature cooling water remaining on the exhaust heat recovery unit side first flows, and then the cooling water that has passed through the exhaust heat recovery unit flows, but When there is an operation delay in the heat recovery unit, the temperature of the cooling water that has passed through the exhaust heat recovery unit is not lowered during the operation delay. Therefore, when the action of the holding means is released based on the fact that the cooling water temperature sensor senses the first low temperature cooling water, the high temperature cooling water due to the operation delay flows into the engine cooling section immediately after that. Therefore, when the cooling water temperature sensor detects the first low temperature cooling water, if the inlet temperature sensor detects the high temperature cooling water due to the operation delay, the action of the hold means is not released and the heat for heat radiation is not released. It is possible to prevent the high-temperature cooling water from flowing into the engine cooling unit due to the operation delay because the supply state to the exchanger is continued.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing a first embodiment of the exhaust heat recovery system according to the present invention.
Further, a generator 3 is interlocked and coupled via a transmission clutch 2.

A main pipe 5 having a first pump 4 interposed between the outlet and the inlet of the engine cooling portion of the gas engine 1.
Is connected. A hot water absorption refrigerator 6 as an exhaust heat recovery unit and a hot water supply facility 7 are connected to the main pipe 5 in parallel with each other via a feed pipe 8a and a return pipe 8b. Further, a cooling device 11 ... Is connected to the hot water absorption refrigerator 6 via a cooling pipe 10 in which a second pump 9 is interposed, and exhaust heat generated by engine cooling is used as a heat source for cooling or hot water supply. Is configured. The main pipe 5, the feed pipe 8a, and the return pipe 8b are collectively referred to as pipes.

Further, a heat radiation heat exchanger is provided in the cooling water supply side pipe downstream of the connection point of the main pipe 5 with the return pipe 8b via a three-way valve 12 as a heat radiation amount changing means and a bypass pipe 13. 14 is connected. The three-way valve 12 may be provided on the inlet side to the heat radiating heat exchanger 14.

A cooling water temperature sensor 15 for measuring the temperature of the cooling water supplied to the engine cooling portion is provided downstream of the connection point of the cooling water supply side pipe with the three-way valve 12. Further, on the downstream side of the connection point between the most downstream return pipe 8b and the main pipe 5, and on the upstream side of the upstream connection point of the cooling water supply side pipe with the bypass pipe 13,
An inlet temperature sensor 16 is provided to measure the temperature of the cooling water supplied to the three-way valve 12, that is, the temperature of the cooling water on the inlet side to the heat dissipation heat exchanger 14.

The cooling water temperature sensor 15 and the inlet temperature sensor 16 are connected to a microcomputer 17, and the microcomputer 17 has a driver 18 for the three-way valve 12.
(See FIG. 2) are connected.

In the microcomputer 17, as shown in the block diagram of FIG. 2, the first and second comparing means 1 are provided.
9 and 20, holding means 21, feedforward side control means 22, feedback side control means 23, and control output addition means 24 are provided.

In the first comparing means 19, the inlet temperature T1 of the cooling water measured by the inlet temperature sensor 16 and the first set temperature Ta set by the inlet temperature setting device 25 (for example, 84
C) is input and compared, and a heat radiation signal is output to the holding means 21 only when the inlet temperature T1 becomes equal to or higher than the first set temperature Ta.

In the second comparing means 20, the temperature T2 of the cooling water supplied to the engine cooling section measured by the cooling water temperature sensor 15 and the second set temperature Tb set by the cooling water temperature setting device 26 (for example, , 83 ° C.) for comparison, and when the measured temperature T2 becomes equal to or lower than the second set temperature Tb, a hold release signal is output to the holding means 21.

In the holding means 21, the first comparing means 1
The heat radiation control signal is output in response to the heat radiation signal from 9, and the output of the heat radiation control signal is stopped in response to the hold release signal from the second comparison means 20, that is, the cooling water temperature sensor. Measurement temperature T2 of cooling water by 15
The heat radiation control signal is continuously output until the temperature becomes equal to or lower than the second set temperature Tb.

In the feedforward side control means 22,
In response to the heat radiation control signal from the holding means 21,
The three-way valve 12 is opened to a predetermined opening, and the heat radiation amount in the operating heat radiation heat exchanger 14 is set in advance to, for example, 30% so that the set heat radiation amount is set to a value smaller than the maximum heat radiation amount. It is designed to output control output.

The feedback side control means 23 outputs a control output according to the temperature change of the cooling water measured by the cooling water temperature sensor 15, and opens the three-way valve 12 when the temperature rises. That is, in order to increase the amount of cooling water supplied to the heat radiating heat exchanger 14, conversely, to close the three-way valve 12 when changing to the descending side, that is, the cooling to be supplied to the heat radiating heat exchanger 14. It is designed to reduce the amount of water.

The control output adding means 24 adds the control output from the feedforward side control means 22 and the control output from the feedback side control means 23, and outputs the added output to the driver 18 of the three-way valve 12. , The three-way valve 12 is controlled so that the opening corresponding to the addition output is obtained.

Next, the control operation according to the above configuration will be described with reference to the flowchart of FIG. First, the inlet temperature T1 measured by the inlet temperature sensor 16 and the cooling water temperature sensor 15
The cooling water temperature T2 measured in (1) is input (S1), and the inlet temperature T1 is compared with the first set temperature Ta (S2).
Here, when the inlet temperature T1 is equal to or higher than the first set temperature Ta, the heat radiation signal is output to the holding means 21 (S3).

Next, the cooling water temperature T2 is compared with the second set temperature Tb (S4). Here, when the cooling water temperature T2 is not lower than or equal to the second set temperature Tb, that is, when the cooling water temperature T2 is higher than the second set temperature Tb, the heat radiation control signal is output to the feedforward side control means 22 (S5). ), The control unit 22 of the feedforward side outputs a control output of 30% to the control output addition unit 24 (S6).

Next, in the control output adding means 24,
The control output from the feedback side control means 23 is added to the control output from the feedforward side control means 22 (S7), and the added control output is output to the driver 18 (S8) and then returned to step S1. The driver 18 controls the three-way valve 12 so that the opening degree corresponding to the added control output is obtained.

In step S2, when the inlet temperature T1 is not higher than the first set temperature Ta, that is, when the inlet temperature T1 is lower than the first set temperature Ta, the process proceeds to step S1.

In step S4, when the cooling water temperature T2 becomes equal to or lower than the second set temperature Tb, the process proceeds to step S9, the hold release signal is output to the hold means 21, and the feedforward side control means 22 outputs the hold release signal. 15% in the control output adding means 24 (this control output is the three-way valve 12
It is in the dead band of the
No cooling water is supplied to the control output) (S1
0) to step S7.

With the above construction, when the exhaust heat demand in the hot water absorption refrigerator 6 and the hot water supply equipment 7 is stable and the temperature change of the cooling water returned to the engine cooling section is small, it is returned to the engine cooling section. The addition of the control output from the feedback side control means 23 based on the temperature T2 of the cooling water effectively acts to control the amount of cooling water supplied to the heat radiating heat exchanger 14.

When the exhaust heat demand suddenly decreases, for example, when the operation of the hot water absorption refrigerator 6 is suddenly stopped, this is set by the cooling water temperature T1 measured by the inlet temperature sensor 16. When the temperature exceeds Ta, it is sensed, and by the action of the holding means 21, the feedforward side control means 22 outputs a control output of 30% to the control output addition means 24, and the amount of cooling water required to radiate the required amount of Not a total amount, but a preset amount (set amount)
Of the cooling water is supplied to the heat radiating heat exchanger 14 to avoid returning the cooling water whose temperature has risen rapidly to the engine cooling section, and to cool the cooling water whose temperature has not risen more than necessary. The cooling of the cooling water having a temperature lower than necessary by supplying it to the exchanger 14 is suppressed, and in the range exceeding the set amount, the engine cooling is performed by the addition of the control output from the feedback side control means 23. The amount of cooling water supplied to the heat radiating heat exchanger 14 is controlled so that the temperature T2 of the cooling water returned to the section does not exceed the set temperature Tb.

When exhaust heat recovery in the exhaust heat recovery section is restarted, such as when the operation of the hot water absorption refrigerator 6 is restarted, this is set by the temperature T2 of the cooling water returned to the engine cooling section. Judging when the temperature becomes equal to or lower than the temperature Tb, the action of the holding means 21 is released after a delay from the point of time when the exhaust heat recovery is restarted, and the feedforward side control means 22 outputs a control output of 15% to the control output addition means 24. Feedback-side control means 23 based on the temperature T2 of the cooling water returned to the engine cooling section, which is measured by the cooling water temperature sensor 15.
Is added, and the amount of cooling water supplied to the heat radiating heat exchanger 14 is controlled so that the temperature T2 of the cooling water returned to the engine cooling unit does not exceed the set temperature Tb by the added control output. .

Next, regarding the operation according to the first embodiment,
This will be described with reference to the graphs of FIGS. 4, 5 and 6. FIG.
Is the outlet temperature (indicated by A1) from the hot water absorption refrigerator 6 and the outlet temperature (B1 from the heat radiation heat exchanger 14 due to changes in exhaust heat demand in the hot water absorption refrigerator 6 and the hot water supply equipment 7.
) [Display both temperatures on the vertical axis and true temperature]
It is a graph which shows the time-dependent change of. The true temperature was measured by using a platinum resistance thermometer with a diameter of 2 mm exclusively for measurement, instead of the platinum resistance thermometer with a diameter of 10 mm incorporated in an ordinary device. FIG. 5 shows the temperature T1 of the cooling water measured by the inlet temperature sensor 16 and the temperature T2 of the cooling water returned to the engine cooling unit measured by the cooling water temperature sensor 15.
FIG. 7 is a graph showing a change with time of [displaying both temperatures on a vertical axis with a control sensor temperature], which is slightly different from the true temperature shown in FIG. 6 due to a delay in response characteristic of the sensor itself and is a smooth change. It can be seen that the temperature is low and the temperature is low, but it is sufficiently following. FIG. 6 is a graph showing the change over time in the control output based on the measured temperatures of both sensors 15 and 16.

When the exhaust heat demand is stable, a control output of 15% (shown by A2) from the feedforward side control means 22 measured by the cooling water temperature sensor 15.
In addition, the control output (B2 from the feedback side control means 23 based on the temperature T2 of the cooling water returned to the engine cooling unit).
The control output (indicated by C) is added to control the opening of the three-way valve 12, and as shown in FIG. 5, the temperature T2 of the cooling water returned to the engine cooling unit is set to the set temperature Tb ( For example, the temperature is maintained close to 80 ℃.

When the demand for exhaust heat recovery sharply decreases from the state where the demand for exhaust heat is stable, for example, when the operation of the hot water absorption refrigerator 6 is suddenly stopped (see P in FIG. 4).
As shown in FIG. 5, the temperature T1 of the cooling water measured by the inlet temperature sensor 16 rises.
When the temperature exceeds a (for example, 80 ° C.), the heat radiation signal is output to the hold means 21 to enter the hold state, and the heat radiation control signal is output from the hold means 21 to the feedforward side control means 22, as shown in FIG. Then, the control output of the feedforward side control means 22 outputs 30% of the control output to shift to the hold state. 30 when entering the hold state
The control output from the feedback side control means 23 based on the temperature T2 of the cooling water returned to the engine cooling unit is added to the control output of%, and the added control output C opens / closes the three-way valve 12. As a result, the temperature T2 of the cooling water returned to the engine cooling unit is maintained at a predetermined temperature (about 80 ° C.).

On the other hand, when the exhaust heat recovery demand increases sharply due to, for example, restart of the operation of the hot water absorption type refrigerator 6, as shown in FIGS. The low-temperature cooling water in the return pipe 8b flows in, and the true temperature A1 and the temperature T1 of the cooling water measured by the inlet temperature sensor 16 sharply decrease. This effect is due to the true temperature B1 at the outlet of the heat radiating heat exchanger 14 and the cooling water temperature sensor 1.
5 appears at each of the measurement temperatures T2 of 5 with the distance of the measurement position delayed by the time t when the cooling water flows. Cooling water temperature sensor 1
When the measured temperature T2 of 5 falls below the set temperature Tb, a hold release signal is output to the hold means 21 to release the hold, and as shown in FIG. 6, the control output A2 from the feedforward side control means 22 is 15%. The control output of the feedback side control means 23 is added to this to control the three-way valve 12, and the heat radiation heat exchanger 1
The amount of the cooling water flowed to 4 is reduced to prevent the temperature T2 of the cooling water returned to the engine cooling unit from dropping more than necessary. After that, as the exhaust heat demand stabilizes, the temperature T2 of the cooling water returned to the engine cooling unit becomes a predetermined temperature (about 80
℃) will be maintained.

FIG. 7 is a block diagram showing the essential parts of a second embodiment of the exhaust heat recovery system according to the present invention. The difference from the first embodiment is as follows. That is, the comparison output from each of the first and second comparing means 19 and 20 in the first embodiment is input to the AND circuit 27, and its A
The output from the ND circuit 27 is input to the hold means 21 as a hold release signal.

Then, in the operation, as shown in the flow chart of FIG. 8, step S in the first embodiment.
Between step 4 and step S9, step S4A for determining whether the temperature T1 of the cooling water measured by the inlet temperature sensor 16 is less than the set temperature Ta is provided, and the cooling water temperature sensor 1
When the temperature T2 of the cooling water returned to the engine cooling unit measured by 5 becomes equal to or lower than the set temperature Tb and the temperature T1 of the cooling water measured by the inlet temperature sensor 16 becomes lower than the set temperature Ta. At step S7, the hold release signal is output. Step S4
In A, when it is determined that the temperature T1 of the cooling water measured by the inlet temperature sensor 16 is equal to or higher than the set temperature Ta, the hold release signal is not output and the process proceeds to step S5. Other configurations and operations are the same as those in the first embodiment, and the description thereof will be omitted.

Next, the characteristic operation of the second embodiment will be described with reference to the time chart of FIG. That is, the demand for exhaust heat recovery increases sharply due to the restart of the operation of the hot water absorption refrigerator 6, and as shown in FIG. Temperature of the cooling water T1 measured by the inlet temperature sensor 16 drops sharply, but next, before the cooling water whose waste heat is actually recovered in the hot water absorption refrigerator 6 flows in. In the case where high-temperature cooling water in which exhaust heat is not recovered flows due to an operation delay in the hot water absorption refrigerator 6, as shown in (b) of FIG. The temperature T2 measured by the water temperature sensor 15 also changes.

When such a situation occurs, in the above-described first embodiment, the hold state is released as the measured temperature T2 of the cooling water temperature sensor 15 becomes less than the set temperature Tb at this time. However, after that, as described above, there is a problem that high-temperature cooling water in which exhaust heat is not recovered flows and the temperature of the cooling water returned to the engine cooling section rises to cause an overshoot. Therefore, in the second embodiment, as shown in FIG. 9C, the cooling water temperature sensor 15
The hold state cannot be released only when the measured temperature T2 of the above is less than the set temperature Tb, the exhaust heat is actually recovered by the hot water absorption refrigerator 6, and the temperature T1 of the cooling water measured by the inlet temperature sensor 16 is also The hold state is released after the temperature becomes lower than the set temperature Ta so that the above-mentioned problem can be avoided.

As the heat radiation amount changing means for changing the flow rate of the cooling water flowing through the heat radiation heat exchanger 14, instead of the three-way valve 12,
For example, the cooling water supply side pipe of the main pipe 5 and the bypass pipe 1
A flow rate adjusting valve may be provided for each of the three, and both flow rate adjusting valves may be interlocked with each other to change the flow rate of the cooling water flowing to the heat radiating heat exchanger 14.

Further, in the above embodiment, the feedforward side control means 22 for obtaining the set heat radiation amount to be held.
The control output from 30% is set to 30%, but this value may be set appropriately according to the capacity of the hot water absorption refrigerator 6 used in the exhaust heat recovery system, the three-way valve 12, etc.
It is about 35%.

[0047]

As is apparent from the above description, according to the exhaust heat recovery system of the first aspect of the present invention, when the exhaust heat demand amount in the exhaust heat recovery section is suddenly reduced, the temperature When the inlet temperature sensor senses the cooling water that has risen sharply, a heat radiation signal is output, based on which a heat radiation control signal is output from the hold means, and in response to the heat radiation control signal, the feed forward side control means outputs the entire amount. A control output having a set heat radiation amount set to a value smaller than the maximum heat radiation amount is output so as to supply a predetermined smaller amount of cooling water to the heat radiation heat exchanger. On the other hand, from the feedback side control means, based on the measured temperature of the cooling water temperature sensor, if the measured temperature becomes high, the amount supplied to the heat radiating heat exchanger increases, and conversely, the measured temperature cannot be lowered. For example, the control output is output so that the amount supplied to the heat radiating heat exchanger is reduced, and the heat radiating amount changing means is operated by the addition predetermined control output of both the feedforward side control means and the feedback side control means. Then, when the exhaust heat recovery in the exhaust heat recovery section is restarted, it is judged that the measured temperature of the cooling water by the cooling water temperature sensor becomes lower than the set temperature, and the action of the holding means is based on that. And the control output from the feedback side control means is effective based on the temperature measured by the cooling water temperature sensor to activate the heat radiation amount changing means, and the temperature of the cooling water returned to the engine cooling unit becomes the set temperature. Control not to exceed. That is, when the exhaust heat demand in the exhaust heat recovery unit is stable and the temperature change of the cooling water returned to the engine cooling unit is small, the feedback side control means based on the temperature of the cooling water returned to the engine cooling unit The added amount of the control output works effectively to control the amount of cooling water supplied to the heat dissipation heat exchanger, and, for example, when the operation of the hot water absorption refrigerator is suddenly stopped, the exhaust heat recovery unit When the exhaust heat demand in the system suddenly decreases, not the total amount of cooling water required to radiate the required amount, but a certain amount of preset cooling water (set amount) is supplied to the heat radiation heat exchanger. In addition to avoiding returning the cooling water whose temperature has risen rapidly to the engine cooling unit, supply cooling water that has not risen to the heat radiation heat exchanger more than necessary to cool it to a temperature lower than necessary. Return the water to the engine cooling section In the range in which the temperature of the cooling water returned to the engine cooling unit does not exceed the set temperature by the addition of the control output from the feedback side control means, The amount of cooling water supplied to the engine is controlled, and when the exhaust heat recovery in the exhaust heat recovery unit is resumed, the cooling returned to the engine cooling unit by the action of the addition of the control output from the feedback side control means. Since the amount of cooling water supplied to the heat dissipation heat exchanger is controlled so that the temperature of the water does not exceed the set temperature, the inner peripheral surface of the pipe is It is not affected by the secular change such as adhesion of scale to the exhaust heat and the change in flow resistance due to the operation and stoppage of the exhaust heat recovery unit, and the overshoot caused by the increase in exhaust heat demand in the exhaust heat recovery unit Good occurrence I was able to stop.

Further, according to the exhaust heat recovery system of the second aspect of the present invention, the low temperature cooling water remaining on the exhaust heat recovery unit side is restarted when the exhaust heat recovery unit restarts the exhaust heat recovery. Even if the cooling water temperature sensor senses, the action of the holding means is not canceled and the supply state to the heat radiating heat exchanger can be continued, so that the high temperature cooling water due to the operation delay in the exhaust heat recovery unit is generated in the engine. It is possible to avoid flowing into the cooling section and improve the stability of control.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of an exhaust heat recovery system according to the present invention.

FIG. 2 is a block diagram showing a configuration of a microcomputer.

FIG. 3 is a flowchart for explaining the operation.

FIG. 4 is a graph showing a change in true temperature with time.

FIG. 5 is a graph showing changes over time in measured temperatures measured by an inlet temperature sensor and a cooling water temperature sensor.

FIG. 6 is a graph showing changes over time in control output.

FIG. 7 is a block diagram showing a main part of a second embodiment of the exhaust heat recovery system according to the present invention.

FIG. 8 is a flowchart of a main part for explaining the operation.

FIG. 9 is a time chart of a main part for explaining the operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Gas engine 5 ... Main piping 6 ... Hot water absorption type refrigerator 7 ... Hot water supply equipment 8a ... Feed piping 8b ... Return piping 12 ... Three-way valve 14 ... Radiating heat exchanger 15 ... Cooling water temperature sensor 16 ... Inlet temperature sensor 17 ... Microcomputer 21 ... Hold means 22 ... Feedforward side control means 23 ... Feedback side control means

Claims (2)

[Claims] 1. The engine cooling part of the engine (1) and the exhaust heat recovery parts (6), (7) are connected via pipes (5), (8a), (8b), and the exhaust heat recovery is performed. From the parts (6) and (7) to the cooling water supply pipe (5) to the engine cooling part, the heat radiation amount changing means (12)
Is provided with a heat dissipation heat exchanger (14), and the cooling water supply side pipe (5) of the exhaust heat recovery section (6), (7) and the heat dissipation heat exchanger (14) An inlet temperature sensor (16) for measuring the temperature of the cooling water is provided between them, and the heat radiation amount changing means (12) is operated based on the temperature of the cooling water measured by the inlet temperature sensor (16). In the exhaust heat recovery system described above, cooling water that is provided on the cooling water supply side pipe (5) downstream of the heat radiating heat exchanger (14) and measures the temperature of the cooling water returned to the engine cooling unit. Temperature sensor (15), the measured temperature of the cooling water by the cooling water temperature sensor (15) is set based on the heat radiation signal output when the temperature measured by the inlet temperature sensor (16) exceeds the set temperature. Hold means that outputs the heat dissipation control signal until it becomes lower than the temperature
(21), and in response to the heat dissipation control signal, the heat dissipation amount changing means (12)
When the engine (1) is in rated operation and the exhaust heat demand of the exhaust heat recovery parts (6), (7) is zero, the valve opening of is supplied to the heat dissipation heat exchanger (14). Based on the measured temperature of the cooling water by the feed-forward side control means (22) for controlling so as to have a preset valve opening smaller than the valve opening for flowing the amount of cooling water to be flowed, and the cooling water temperature sensor (15). The exhaust heat recovery system further comprises feedback side control means (23) for controlling the heat radiation amount changing means (12) so that the heat radiation amount increases as the measured temperature increases. 2. The holding means (21) according to claim 1,
The measured temperature of the cooling water by the inlet temperature sensor (16) is lower than the set temperature (A), and the cooling water temperature sensor (15)
An exhaust heat recovery system that outputs a heat dissipation control signal until the measured temperature of the cooling water by is lower than the set temperature (B).