JPH109054A - Exhaust heat recovery system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of an overshoot resulting from a sudden variation of the exhaust heat recovery amount without receiving the influence of an aged deterioration, as well as suppressing the generation of a control delay problem reasonably. SOLUTION: A sudden reduction of the exhaust heat recovery amount by the stop of a circulation pump and the stop of operation of a warm water suction type refrigerator is perceived by a flow switch 21 and a load side circulation water temperature sensor 20, 30% of control output is output from a feed forward side control means 28, a three-way valve 16 is controlled by the control output adding the control output from a feed back side control means 24 to the above control output, and a cooling water with a set amount a little smaller than the full amount of the cooling water is fed to a heat exchanger for radiation. When the exhaust heat recovery is reopened, the control output from the feed forward side control means 28 is maintained at 30%, until a cooling water temperature sensor 19 perceives that the temperature of the cooling water returned to the engine cooler is made less than a set temperature, so as to avoid to return the cooling water of a high temperature owing to an overshoot, to the engine cooler.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention connects an engine cooling unit such as a cooling jacket of a gas engine or a diesel engine to a heat exchanger for exhaust heat recovery via a cooling water circulation pipe for use in a cogeneration system or the like. At the same time, the exhaust heat recovery heat exchanger is connected to the exhaust heat recovery load, such as a hot water absorption refrigerator, hot water supply equipment, and heating device, via a load-side circulation pipe with a circulation pump. On the downstream side of the cooling water circulation pipe from the exchanger, a cooling water circulation pipe is provided with a heat radiation heat exchanger having a heat radiation amount changing means such as a three-way valve and a bypass pipe, and a heat radiation amount changing means. On the downstream side, a cooling water temperature sensor for measuring the temperature of the cooling water returned to the engine cooling unit is provided in the cooling water circulation pipe, and the cooling water measured by the cooling water temperature sensor is provided. About the exhaust heat recovery system configured to operate the heat radiation amount changing means based on the time.

[0002]

2. Description of the Related Art An exhaust heat recovery system as described above usually includes feedback side control means for operating a heat radiation amount changing means so that the temperature of cooling water measured by a cooling water temperature sensor becomes a set temperature. The amount of cooling water to be supplied to the heat radiating heat exchanger is controlled such that the temperature of the cooling water supplied to the engine cooling unit becomes the set temperature. This allows
It is possible to avoid the occurrence of a so-called engine trip in which the temperature of the cooling water in the cooling jacket rises excessively, the engine protection circuit is activated, and the engine is automatically stopped.

[0003]

By the way, in the above-mentioned exhaust heat recovery system, for example, the amount of exhaust heat demand suddenly decreases, for example, when a hot water absorption refrigerator is suddenly stopped, or a circulation pump is used. An abnormal situation occurs in which the amount of exhaust heat recovery sharply decreases, for example, the device stops due to a failure or the like and cannot recover exhaust heat.

[0004] However, in the conventional example, even if a heat-exchanging heat exchanger for lowering the water temperature is provided in the downstream side via a three-way valve or the like, the heat-exchanging heat exchanger for exhaust-heat recovery due to the occurrence of the abnormal situation described above. If the water temperature in the cooling water circulation pipe through the exchanger rises sharply, heat will not be taken away sufficiently by the heat exchanger for heat dissipation due to control delay, and the temperature of the cooling water will overshoot the set temperature, causing the high-temperature cooling water to flow into the engine. Return and engine trip.

For this reason, the set temperature is lowered in consideration of the maximum temperature due to overshoot. However, there is a disadvantage that the temperature of the cooling water taken out from the engine cooling unit in a normal time is lowered, and the exhaust heat recovery efficiency is reduced.

Therefore, the temperature of the cooling water discharged from the heat exchanger for exhaust heat recovery is measured by an inlet temperature sensor, and feedforward control for operating a radiation amount changing means such as a three-way valve is performed based on the measured temperature. In order to prevent overshoot by activating the heat radiation amount changing means at an early stage, it has been proposed.

In the case of performing the feedforward control, if the location where the temperature of the cooling water is measured by the inlet temperature sensor is close to the location where the cooling water circulates from the piping side to the heat-radiating heat exchanger side, a control delay occurs, and the drainage occurs. When the heat recovery amount sharply decreases, there is a problem in that the high-temperature cooling water that has not flowed to the heat-radiating heat exchanger side is returned to the engine cooling section to cause overshoot.

Further, when an inlet temperature sensor is provided at a position where control delay does not occur, it is possible to cope with a sudden decrease in the amount of exhaust heat recovery. When the amount of exhaust heat recovered increases, for example, when the operation of the hot water absorption refrigerator is restarted, the temperature of the cooling water is sensed by the inlet temperature sensor to reduce the temperature of the cooling water, and the heat radiation amount changing means is actuated. If the amount of heat dissipated in the heat exchanger decreases rapidly, some cooling water will not be dissipated by the heat dissipating heat exchanger and will return to the engine cooling section at a high temperature, causing overshoot. there were.

Therefore, in order to solve such a problem,
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 consider continuing the heat radiation in the heat radiation heat exchanger for that time. Was done.

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 rate of the cooling water flowing therethrough. However,
The inner diameter of the pipe may change with time, for example, the scale may adhere to the inner peripheral surface of the pipe with use, and the flow resistance may increase.

Therefore, it is difficult to appropriately set the delay time over a long period of time, and there is a drawback that the cost is increased because the control delay time is incorporated into the control configuration. Was rare.

The present invention has been made in view of such circumstances, and the exhaust heat recovery system according to the first aspect of the present invention rationally suppresses the occurrence of a control delay problem and is capable of preventing aging. It is an object of the present invention to prevent overshoot from occurring due to a sudden change in the amount of exhaust heat recovery without being affected. An object of the present invention is to prevent control from becoming unstable due to an operation delay at the time.

[0013]

The invention according to claim 1 is
To achieve the above object, the engine cooling section of the engine (1) is connected to the exhaust heat recovery heat exchanger (6) via the cooling water circulation pipe (5), and the exhaust heat recovery heat exchanger is connected. Load side circulation piping with circulation pump (7) interposed in exchanger (6)
Exhaust heat recovery loads (9) and (10) are connected via (8), and on the downstream side of the cooling water circulation pipe (5) from the exhaust heat recovery heat exchanger (6),
The cooling water circulation pipe (5) is provided with a heat radiation heat exchanger (18) having a heat radiation amount changing means (16), and the cooling water circulation pipe (5) is located downstream of the heat radiation amount changing means (16). The cooling water temperature sensor (1) measures the temperature of the cooling water returned to the engine cooling section.
In the exhaust heat recovery system configured to operate the heat radiation amount changing means (16) based on the cooling water temperature measured by the cooling water temperature sensor (19),
A load-side circulating water temperature sensor (20) that is provided downstream of the exhaust heat recovery loads (9) and (10) of (8) and measures the temperature of the load-side circulating water flowing therethrough; Circulating water temperature sensor
Comparing the temperature of the load-side circulating water measured in (20) with the first set temperature and outputting a heat radiation signal when the temperature of the load-side circulating water is equal to or higher than the first set temperature; Means (22)
Is provided in the load-side circulation pipe (8) to detect whether the flow state of the load-side circulating water is a predetermined flow state or any other abnormal flow state, and output a heat radiation signal in accordance with the detection of the abnormal flow state Flow state detecting means (21) and a holding means (27) for outputting a heat radiation signal until the measured temperature of the cooling water by the cooling water temperature sensor (19) becomes lower than a second set temperature based on the heat radiation signal. ), And in response to the heat radiation signal, the engine (1) performs a rated operation of the valve opening of the heat radiation amount changing means (16),
In addition, when the exhaust heat demand of the exhaust heat recovery loads (9) and (10) is zero, the opening degree is preset to be smaller than the valve opening degree through which the amount of cooling water to be supplied to the heat radiating heat exchanger (18) flows. Feedforward side control means (28) for outputting a control output so as to reach the set valve opening degree,
Based on the measured temperature of the cooling water by the cooling water temperature sensor (19), the feedback control means (24) for outputting a control output for controlling the heat radiation amount changing means (16) so that the heat radiation amount increases as the measured temperature increases. ), And controls the heat radiation amount changing means (16) by a control output obtained by adding the control output from the feed forward control means (28) and the control output from the feedback control means (24). . The numbers given in parentheses [()] to each element are given with reference to FIGS. 1, 2 and 7 for easy understanding. The invention described in the claims excludes each number. For example,
The description of the exhaust heat recovery loads (9) and (10) means that the exhaust heat recovery load may be singular [Example (9)] or plural [Examples (9) and (10)].

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

Further, the exhaust heat recovery system according to the second aspect of the present invention has the first aspect in order to achieve the above object.
Holding means in the exhaust heat recovery system of the invention according to (2).
7), the load-side circulating water temperature measured by the load-side circulating water temperature sensor (20) becomes lower than its set temperature (Ta), and
The cooling water temperature sensor (19) is configured to output the heat radiation signal until the measured temperature of the cooling water becomes lower than the set temperature (Tb).

[0016]

According to the configuration of the exhaust heat recovery system according to the first aspect of the present invention, the exhaust heat demand at the exhaust heat recovery loads (9) and (10) sharply decreases, and the temperature of the load side circulating water decreases. When the temperature rises rapidly and exceeds the first set temperature, it is detected by the load-side circulating water temperature sensor (2
0) senses and outputs a heat radiation signal. Also a circulation pump
When an abnormal flow state such as the load side circulating water not flowing due to the failure of (7) occurs, the flow state detection means (21) detects the occurrence and outputs a heat radiation signal. A heat radiation signal is output from the holding means (27) based on such a heat radiation signal, and in response to the heat radiation signal, the set heat radiation amount set to a value smaller than the maximum heat radiation amount by the feed forward side control means (28). The control output for operating the heat radiation amount changing means (16) is issued so that the cooling water is supplied to the heat radiation heat exchanger (18) in an amount smaller than the total amount. On the other hand, in the feedback side control means (24), based on the measured temperature of the cooling water temperature sensor (19), if the measured temperature increases, the amount supplied to the heat-radiating heat exchanger (18) increases, Conversely, when the measured temperature decreases, a control output for operating the heat radiation amount changing means (16) is issued so that the amount supplied to the heat radiation heat exchanger (18) decreases. Then, the control output from the feedforward control means (28) and the feedback control means
The heat radiation amount changing means (16) is operated by the control output of the entire system obtained by adding the control output from (24).

On the other hand, when the exhaust heat recovery at the exhaust heat recovery loads (9) and (10) is resumed or when the amount of the exhaust heat demand increases, this is notified by the cooling water temperature sensor (19). Is determined by the measured temperature of being lower than the second set temperature, based on which the operation of the holding means (27) is released,
Cooling water is not supplied to the heat radiation heat exchanger (18) only by the control output from the feed forward control means (28), but the feedback control means (24) is based on the temperature measured by the cooling water temperature sensor (19). Is added, and the heat radiation amount changing means (16) is operated so that the temperature measured by the cooling water temperature sensor (19) does not exceed the second set temperature.

More specifically, when the exhaust heat demand at the exhaust heat recovery loads (9) and (10) is stable and the temperature change of the cooling water returned to the engine cooling unit is small, the engine cooling unit The addition of the control output from the feedback-side control means (24) based on the temperature of the returned cooling water effectively acts to control the amount of cooling water supplied to the heat-radiating heat exchanger (18).

For example, when the demand for exhaust heat at the exhaust heat recovery loads (9) and (10) suddenly decreases, such as when the operation of the hot water absorption refrigerator is stopped, or when the failure of the circulation pump (7) occurs. When an abnormal flow state such as load-side circulating water does not flow occurs and exhaust heat recovery becomes impossible as a result, the fact that the load-side circulating water temperature measured by the circulating-water temperature sensor (20) is When the temperature exceeds the first set temperature or when the flow state detecting means (21) detects an abnormal flow state, the secondary side of the exhaust heat recovery heat exchanger (6) detects the temperature quickly and the holding means (2)
By the action of 7), instead of the total amount of cooling water required to dissipate the required amount, a predetermined amount (set amount) of cooling water is supplied to the heat exchanger for heat radiation (18), and suddenly Avoid returning the high-temperature cooling water to the engine cooling section, and supply unnecessarily low-temperature cooling water to the heat-radiating heat exchanger (18) to cool the unnecessarily low-temperature cooling water. Is returned to the engine cooling section, and in a range exceeding the set amount, the temperature of the cooling water returned to the engine cooling section decreases the set temperature by the addition of the control output from the feedback side control means (24). The amount of cooling water supplied to the heat-exchanging heat exchanger (18) is controlled so as not to exceed.

When the exhaust heat recovery at the exhaust heat recovery loads (9) and (10) is resumed, or when the exhaust heat demand at the exhaust heat recovery loads (9) and (10) shifts to a stable state, As described above, the action of the hold means (27) is released as described above, and the action of the addition of the control output from the feedback control means (24) based on the temperature measured by the cooling water temperature sensor (19) is used. The amount of the cooling water supplied to the heat radiating heat exchanger (18) is controlled so that the temperature of the cooling water returned to the engine cooling unit does not exceed the set temperature.

Further, according to the configuration of the exhaust heat recovery system according to the second aspect of the present invention, the operation of the holding means (27) is canceled so that the measured temperature of the cooling water by the cooling water temperature sensor (19) becomes lower than the set temperature. In addition to the above, the determination is made based on the fact that the measured temperature of the load side circulating water by the load side circulating water temperature sensor (20) becomes lower than the set temperature. For example, when resuming the exhaust heat recovery at the exhaust heat recovery loads (9) and (10), the exhaust heat recovery heat exchanger (6) is initially connected to the exhaust heat recovery loads (9) and (10). The remaining low-temperature circulating water flows, and then the exhaust heat recovery load
Although the circulating water flows through (9) and (10), the exhaust heat recovery load
When there is an operation delay in (9) and (10), the temperature of the circulating water that has passed through the exhaust heat recovery loads (9) and (10) has not decreased during the operation delay. Therefore, based on the fact that the cooling water temperature sensor (19) senses the first low-temperature cooling water, the holding means (27)
When the cooling water temperature sensor (19) detects the first low-temperature cooling water, the high-pressure cooling water due to the operation delay flows into the engine cooling section immediately after the operation is canceled. If the circulating water temperature sensor (20) detects high-temperature circulating water due to operation delay, hold means
The function of (27) is not canceled, and the supply state to the heat radiating heat exchanger (18) is continued, so that high-temperature cooling water due to operation delay can be prevented from flowing into the engine cooling unit.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings.

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

An exhaust heat recovery heat exchanger 6 is connected to an outlet and an inlet of the engine cooling section of the gas engine 1 via a cooling water circulation pipe 5 provided with a first pump 4. A load-side circulation pipe 8 having a circulation pump 7 interposed is connected to the heat exchanger 6 for exhaust heat recovery.
In addition, a hot water absorption refrigerator 9 and a hot water supply facility 10 as exhaust heat recovery loads are connected in parallel to each other via a feed pipe 11a and a return pipe 11b, and a three-way valve 12 for adjusting a hot water supply amount. . Further, a cooling device 15 is connected to the hot water absorption refrigerator 9 via a cooling pipe 14 provided with a second pump 13 interposed therebetween, so that exhaust heat generated by cooling the engine is used as a heat source for cooling and hot water supply. Is configured.

Further, on the downstream side of the cooling water circulation pipe 5 from the exhaust heat recovery heat exchanger 6, a heat radiation heat exchanger 18 via a three-way valve 16 as a heat radiation amount changing means and a bypass pipe 17.
Is connected. The three-way valve 16 may be provided on the inlet side to the heat exchanger 18 for heat radiation.

A cooling water temperature sensor 19 for measuring the temperature of the cooling water supplied to the engine cooling section is provided downstream of the connection point of the cooling water circulation pipe 5 with the three-way valve 16. Further, a load-side circulating water temperature sensor 2 that measures the temperature of the load-side circulating water after exhaust heat recovery that flows through the load-side circulating pipe 8 downstream of the three-way valve 12 with respect to the hot water supply equipment 10.
0 and a flow switch 21 that detects the presence or absence of the flow state of the load side circulating water and outputs a heat radiation signal when the flow of the load side circulating water stops.

The load-side circulating water temperature sensor 20 is connected to a comparator 22 as exhaust heat recovery amount detecting means. In the comparator 22, the temperature T1 of the load-side circulating water measured by the load-side circulating water temperature sensor 20 is measured. Is compared with the first set temperature Ta input from the first temperature setter 23 (see FIG. 2), and the temperature T1 of the load side circulating water is set to the set temperature T.
It is configured to output a heat radiation signal when the value exceeds a.

The above-described flow switch 21 determines whether the load side circulating water is flowing or not flowing, in other words, whether the circulating pump 7 is stopped.
For example, a flow rate sensor is provided in place of the flow switch 21, and the flow rate of the load side circulating water measured by the flow rate sensor is compared with a set speed by a comparator, and the flow rate of the load side circulating water is lower than the set speed. In some cases, a heat radiation signal may be output so as to detect not only the stop of the circulating pump 7 but also a decrease in flow velocity due to leakage in the load-side circulating pipe 8. The flow switch 21 and the flow switch 21 may be configured so as to detect a predetermined flow state or another abnormal flow state and output a heat radiation signal in accordance with the detection of the abnormal flow state. , A flow state sensor and a comparator are collectively referred to as flow state detecting means.

Feedback side control means 24 is connected to the cooling water temperature sensor 19, and the feedback side control means 24 performs proportional differential integration control (PID control) based on the measured temperature of the cooling water by the cooling water temperature sensor 19. Then, a control output for controlling the three-way valve 16 is issued so that the heat radiation increases as the measured temperature increases. More specifically, a control output corresponding to a change in the measured temperature of the cooling water by the cooling water temperature sensor 19 is issued, and the three-way valve 16 is opened when the temperature changes to a rising side, that is,
In order to increase the amount of the cooling water supplied to the heat radiation heat exchanger 18, on the contrary, to close the three-way valve 16 when it changes to the descending side, that is, to supply the cooling water to the heat radiation heat exchanger 18. The amount is to be reduced.

A microcomputer 25 is connected to each of the cooling water temperature sensor 19, the flow switch 21 and the comparator 22. The microcomputer 25 includes a comparing unit 26, a holding unit 27, and a feed-forward control unit 28.

In the comparison means 26, the cooling water temperature sensor 19
Is compared with the second set temperature Tb inputted from the second temperature setter 29, and when the measured coolant temperature T2 becomes equal to or lower than the second set temperature Tb. A hold release signal is output to the hold means 27, and the output of a heat radiation signal described later from the hold means 27 is prohibited.

In the holding means 27, the flow switch 2
1 and the heat release signal from the comparator 22 until the hold release signal is received from the comparison means 26, that is, until the measured temperature T2 of the coolant by the coolant temperature sensor 19 becomes equal to or lower than the second set temperature Tb. It is designed to output a signal.

In the feed forward side control means 28,
In response to the heat radiation signal from the holding means 27, the three-way valve 1
When the gas engine 1 is rated and the exhaust heat demand of the hot water absorption chiller 9 and the hot water supply equipment 10 is zero, the amount of cooling water to be supplied to the heat radiating heat exchanger 18 is set to the valve opening degree of 6. A control output of, for example, 30% is output so that a preset valve opening degree smaller than the valve opening degree is set in advance.

The control output from the feedback-side control means 24 and the control output from the feedforward-side control means 28 are input to the control output adding means 30 and added, and the control output obtained by adding the two is output to the control output adding means. The output from 30 to the driver 31 of the three-way valve 16 is controlled so that the opening of the three-way valve 16 is controlled so as to obtain an opening corresponding to the added control output.

Next, the control operation of the above configuration will be described with reference to the flowchart of FIG. First, the load side circulating water temperature T1 measured by the load side circulating water temperature sensor 20 and the cooling water temperature T2 measured by the cooling water temperature sensor 19 are input (S1), and the load side circulating water temperature T1 is set. Is compared with the first set temperature Ta (S2). Here, when the temperature T1 of the load-side circulating water is equal to or higher than the first set temperature Ta, a heat radiation signal is output to the holding means 27 (S3).

In step S2, when the temperature T1 of the load side circulating water is lower than the first set temperature Ta, the flow shifts to step S4 to judge whether or not the circulating pump 7 is stopped, ie, whether or not the circulating pump 7 is stopped. . Here, when it is determined that the circulation pump 7 is stopped, the process proceeds to step S3 to output a heat radiation signal to the holding means 27 (S3). On the other hand, when it is determined that the circulation pump 7 is not stopped, Since the predetermined exhaust heat recovery is being performed, the process returns to step S1.

After the heat radiation signal is output, the cooling water temperature T2 is compared with the second set temperature Tb (S5). 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 lower than the second set temperature Tb.
If it is higher than this, a heat radiation signal is output to the feed forward control means 28 (S6), and a 30% control output is output from the feed forward control means 28 to the control output adding means 30 (S7).

Next, in the control output adding means 30,
The control output from the feedback control means 24 is added to the control output from the feedforward control means 28 (S8), and the added control output is output to the driver 31 (S9), and the process returns to step S1. Thus, the three-way valve 16 is controlled through the driver 31 so that an opening corresponding to the added control output is obtained.

In step S5, when the cooling water temperature T2 falls below the second set temperature Tb, step S5
10 and outputs a hold release signal to the hold means 27. The feedforward control means 28 outputs 15% to the control output adding means 30 (this control output is within the dead band of the three-way valve 16, and actually, (A cooling water is not supplied to the heat exchanger 18), and the process proceeds from step S11 to step S8.

With the above configuration, when the demand for exhaust heat in the hot water absorption refrigerator 6 and the hot water supply system 7 is stable and the temperature change of the cooling water returned to the engine cooling unit is small, the cooling water is returned to the engine cooling unit. The added amount of the control output from the feedback side control means 24 based on the temperature T2 of the cooling water effectively acts to control the amount of the cooling water supplied to the heat exchanger 18 for heat radiation.

For example, when the circulating pump 7 is stopped due to a failure or the like, or the operation of the hot water absorption refrigerator 9 is suddenly stopped, and the amount of exhaust heat recovery decreases sharply, this is taken into account. It is detected whether the temperature T1 of the load-side circulating water measured by the temperature sensor 20 becomes equal to or higher than the first set temperature Ta, or whether the flow switch 21 detects the flow stop state. A 30% control output is output from the side control means 28 to the control output adding means 30, and a predetermined amount (set amount) of cooling water is radiated instead of the total amount of cooling water required to radiate the required amount. The cooling water supplied to the cooling heat exchanger 18 to avoid returning the cooling water whose temperature has suddenly increased to the engine cooling unit, and the cooling water whose temperature has not risen more than necessary. 8 to prevent the cooling water having a temperature lower than necessary from being returned to the engine cooling unit, and within a range exceeding the set amount, the added amount of the control output from the feedback control unit 24 causes the engine cooling unit to The amount of the cooling water supplied to the heat radiating heat exchanger 18 is controlled so that the returned cooling water temperature T2 does not exceed the second set temperature Tb.

When the exhaust heat recovery by the exhaust heat recovery load is restarted, for example, by restarting the circulation pump 7 or restarting the operation of the hot water absorption refrigerator 9, the fact is returned to the engine cooling section. The cooling water temperature T2 becomes equal to or lower than the second set temperature Tb, and the load side circulating water temperature T1 becomes the first set temperature Tb.
a from the feed forward side control means 28 to the control output adding means 30 by releasing the operation of the holding means 27 at a time later than the restart time of the exhaust heat recovery. A control output is output, and a control output from the feedback side control means 24 based on the temperature T2 of the cooling water returned to the engine cooling unit, which is measured by the cooling water temperature sensor 19, is added. The amount of the cooling water supplied to the heat-radiating heat exchanger 18 is controlled so that the temperature T2 of the cooling water returned to the temperature does not exceed the second set temperature Tb.

Next, regarding the operation according to the first embodiment,
This will be described with reference to the graphs of FIGS. FIG.
Are the outlet temperature (shown by A1) from the hot water supply system 10 and the outlet temperature (shown by B1) from the heat-dissipating heat exchanger 18 due to changes in the exhaust heat demand in the hot water absorption refrigerator 9 and the hot water supply system 10. It is a graph which shows a time-dependent change of [each temperature is displayed on a vertical axis and a true temperature]. The true temperature is
The measurement was performed using a 2 mm diameter platinum resistance thermometer dedicated for measurement instead of a 10 mm diameter platinum resistance temperature detector incorporated in a normal apparatus.

FIG. 5 shows the temperature T1 of the load-side circulating water measured by the load-side circulating water temperature sensor 20 and the temperature T2 of the cooling water returned to the engine cooling section measured by the cooling-water temperature sensor 19 [both temperatures, respectively]. Is displayed on the vertical axis of the control sensor temperature).
It can be seen that, although a slight shift occurs due to the delay of the response characteristic of the sensor itself as compared with the true temperature in FIG. 6 and a smooth change occurs, and the temperature is low, the temperature sufficiently follows.

FIG. 6 is a graph showing the change over time of the control output based on the measured temperatures of the two sensors 19 and 20. In a state where the exhaust heat demand is stable, the flow state is detected by the flow switch 21 and the temperature T1 of the load-side circulating water lower than the first set temperature Ta measured by the load-side circulating water temperature sensor 20. The control output (indicated by B2) from the feedback-side control means 24 based on the temperature T2 of the cooling water returned to the engine cooling unit is added to the 15% control output (indicated by A2) from the feedforward-side control means 28. The control output (indicated by C) is output 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 changed to a second set temperature Tb (for example,
80 ° C).

When the demand for exhaust heat is stable and the exhaust heat recovery decreases rapidly, for example, the circulation pump 7 is stopped or the operation of the hot water absorption refrigerator 9 is suddenly stopped. As shown in FIG. 5, the temperature T1 of the load-side circulating water measured by the load-side circulating water temperature sensor 20 rises, but as shown in FIG. 5, the first set temperature Ta (for example, 80 ° C.) ), The heat radiation signal is output to the holding means 27 to enter the hold state, and at the same time, the heat radiation signal is output from the holding means 27 to the feedforward control means 28, and as shown in FIG. A control output of 28 to 30% is output and the state shifts to the hold state. When the state shifts to the hold state, the control output from the feedback side control means 24 based on the temperature T2 of the cooling water returned to the engine cooling unit is added to the control output of 30%, and the three-way valve 12 is operated by the added control output C. Open and close. 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, if the exhaust heat recovery demand sharply increases, for example, when the circulation pump 7 is restarted or the operation of the hot water absorption refrigerator 9 is restarted, as shown in FIGS. First, the low-temperature load-side circulating water flows into the exhaust heat recovery heat exchanger 6, and the true temperature A1 and the cooling water temperature T1 measured by the load-side circulating water temperature sensor 20 rapidly decrease. This effect appears at the true temperature B1 at the outlet of the heat radiation heat exchanger 18 and the measured temperature T2 of the cooling water temperature sensor 19 with a delay of the time t at which the cooling water flows through the distance between the measurement positions. When the measured temperature T2 of the cooling water temperature sensor 19 becomes equal to or lower than the second set temperature Tb, a hold release signal is output to the hold means 27 to release the hold, and as shown in FIG. The control output A2 is returned to 15%, and the three-way valve 16 is controlled by the control output C obtained by adding the control output B2 from the feedback-side control means 24 to the amount of the cooling water flowing to the heat-radiating heat exchanger 18. To prevent the temperature T2 of the cooling water returned to the engine cooling unit from unnecessarily lowering.
Thereafter, as the exhaust heat demand becomes stable, the temperature T2 of the cooling water returned to the engine cooling unit is maintained at a predetermined temperature (about 80 ° C.).

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. The difference from the first embodiment is as follows. That is, the comparison output from each of the comparator 22 and the comparison means 26 in the first embodiment is input to the AND circuit 32,
The output from the ND circuit 32 is input to the hold means 27 as a hold release signal.

In the operation, as shown in the flowchart of FIG. 8, step S in the first embodiment is performed.
5 and step S10, a step S5A for judging whether the temperature T1 of the load-side circulating water measured by the load-side circulating water temperature sensor 20 is lower than the first set temperature Ta is provided, and the cooling water temperature The temperature T2 of the cooling water returned to the engine cooling unit measured by the sensor 19 becomes equal to or lower than the second set temperature Tb, and the temperature T1 of the cooling water measured by the load-side circulating water temperature sensor 20 becomes the first temperature T1. When the temperature becomes lower than the set temperature Ta, the flow shifts to step S10 to output a hold release signal. If it is determined in step S5A that the cooling water temperature T1 measured by the load-side circulating water temperature sensor 20 is equal to or higher than the first set temperature Ta, the process proceeds to step S6 without outputting the hold release signal. Has become. Other configurations and operations are the same as those of the first embodiment, and a description thereof will be omitted.

Next, a characteristic operation according to the second embodiment will be described with reference to a time chart of FIG. That is, the exhaust heat recovery demand sharply increases due to the restart of the operation of the hot water absorption refrigerator 9 or the like, and as shown in FIG. Low-temperature circulating water flows into the heat exchanger 6 for exhaust heat recovery, and the temperature T1 of the load-side circulating water measured by the load-side circulating water temperature sensor 20 sharply decreases.
In the case where the high-temperature cooling water from which the exhaust heat is not recovered due to an operation delay in the hot water absorption refrigerator 9 before the circulating water from which the exhaust heat has been actually recovered flows, as shown in FIG. As shown in b), the measured temperature T2 of the cooling water temperature sensor 19 also changes with a time delay t.

When such a situation occurs, in the above-described first embodiment, the hold state is released at this time as the measured temperature T2 of the cooling water temperature sensor 19 falls below the second set temperature Tb. However, thereafter, as described above, there is a problem in that high-temperature cooling water from which exhaust heat is not recovered flows, and the temperature of the cooling water returned to the engine cooling unit increases, causing overshoot. Therefore, in the second embodiment, as shown in FIG. 9C, the hold state cannot be released only when the measured temperature T2 of the cooling water temperature sensor 19 falls below the second set temperature Tb. The exhaust heat is actually recovered by the absorption refrigerator 9, and the circulating water temperature T1 measured by the load-side circulating water temperature sensor 20 is also the first set temperature T.
The hold state is released after the value becomes less than a so that the above-described 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 18, instead of the three-way valve 16,
For example, a bypass pipe 17 and two bypass pipes 1
A flow rate control valve is separately provided in a portion of the cooling water circulating pipe 5 sandwiched between the points where the pipes 7 and 17 are connected, and the flow rate control valves are linked to each other to change the flow rate of the cooling water flowing to the heat radiation heat exchanger 18. May be configured.

In the above embodiment, the feed-forward control means 28 for obtaining the set heat radiation amount to be held.
Is set to 30%, but this value may be appropriately set according to the capacity of the hot water absorption refrigerator 9 used in the exhaust heat recovery system, the three-way valve 16, and the like.
It is about 35%.

[0054]

As is apparent from the above description, according to the exhaust heat recovery system of the present invention, the heat exchanger for exhaust heat recovery (6)
A load-side circulating water temperature sensor (20) and a flow state detection means (21) are provided on the load-side circulating pipe side, which is the secondary side pipe, and the flow-side circulating water flows due to a failure of the circulating pump (7). The load-side circulating water temperature sensor (20) senses when abnormalities are detected or the circulating water whose exhaust heat demand at the exhaust heat recovery load (9), (10) suddenly decreases and the temperature rises sharply When the heat release signal is output, a heat release signal is output from the holding means (27) based on the signal, and in response to the heat release signal, a predetermined amount of cooling less than the total amount is supplied from the feed forward side control means (28). In order to supply water to the heat radiating heat exchanger (18), a control output having a heat radiation amount set to a value smaller than the maximum heat radiation amount is output.

On the other hand, from the feedback side control means (24), if the measured temperature is high based on the measured temperature of the cooling water temperature sensor (19), the amount supplied to the heat-radiating heat exchanger (18) increases. Conversely, when the measured temperature decreases, the control output is output so that the amount supplied to the heat-radiating heat exchanger (18) decreases, and the feed-forward control means
The heat radiation amount changing means (16) is operated by the control output determined by the addition of the control means (28) and the feedback control means (24).
Then, when the exhaust heat recovery at the exhaust heat recovery loads (9) and (10) is restarted, the fact is that the measured temperature of the cooling water by the cooling water temperature sensor (19) becomes lower than the set temperature. Judgment, release the action of the holding means (27) based on it,
The control output from the feedback side control means (24) based on the temperature measured by the cooling water temperature sensor (19) effectively acts to operate the heat radiation amount changing means (16), and the cooling water returned to the engine cooling section. Control so that the temperature does not exceed the set temperature.

That is, when the demand for the exhaust heat at the exhaust heat recovery loads (9) and (10) is stable and the temperature change of the cooling water returned to the engine cooling unit is small, the cooling water returned to the engine cooling unit Feedback-side control means based on the temperature of the vehicle (24)
The addition of the control output from the CPU effectively acts to control the amount of cooling water supplied to the heat-radiating heat exchanger (18).

For example, the circulation pump (7) is stopped,
When the amount of exhaust heat recovery at the exhaust heat recovery load (9) or (10) decreases rapidly, such as when the operation of the hot water absorption refrigerator is suddenly stopped, the amount of cooling water required to release the required amount of heat Is supplied to the heat-radiating heat exchanger (18), instead of the total amount of the cooling water, of a predetermined amount (set amount). As a result, it is possible to avoid returning the cooling water whose temperature has suddenly increased to the engine cooling section, and to supply the cooling water whose temperature has not increased to the heat exchanger (18) for heat radiation more than necessary. It is possible to suppress the return of the low-temperature cooling water to the engine cooling section. Also,
In the range exceeding the set amount, the feedback control means (2
By the addition of the control output from 4), the amount of the cooling water supplied to the heat-radiating heat exchanger (18) can be favorably controlled so that the temperature of the cooling water returned to the engine cooling unit does not exceed the set temperature.

Further, the circulation pump (7) is restarted,
When the exhaust heat recovery at the exhaust heat recovery loads (9) and (10) is resumed, the temperature of the cooling water returned to the engine cooling unit is increased by the action of the addition of the control output from the feedback control means (24). Control the amount of cooling water supplied to the heat-exchanger heat exchanger (18) so that the temperature does not exceed the set temperature. As a result, it is possible to prevent the occurrence of overshoot caused by the increase in the amount of exhaust heat recovery in the exhaust heat recovery loads (9) and (10) without being affected by the secular change such as the adhesion of scale to the surface.

According to the exhaust heat recovery system of the second aspect of the present invention, when the exhaust heat recovery is resumed at the exhaust heat recovery loads (9) and (10), respectively, the exhaust heat recovery loads (9) and (9) Even if the low-temperature circulating water remaining on the (10) side is detected by the load-side circulating water temperature sensor (20), the operation of the holding means (27) is not released,
Since the supply state to the heat radiation heat exchanger (18) can be continued, it is possible to prevent high-temperature cooling water from flowing into the engine cooling section due to operation delay in the exhaust heat recovery loads (9) and (10), Control stability can be improved.

[Brief description of the 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 illustrating a configuration of a microcomputer.

FIG. 3 is a flowchart for explaining an operation;

FIG. 4 is a graph showing a change over time of a true temperature.

FIG. 5 is a graph showing a change over time of a temperature measured by an inlet temperature sensor and a cooling water temperature sensor.

FIG. 6 is a graph showing a temporal change of a 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 explanation of operation.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Gas engine 5 ... Cooling water circulation pipe 6 ... Exhaust heat recovery heat exchanger 7 ... Circulation pump 8 ... Load side circulation pipe 9 ... Hot water absorption type refrigerator as exhaust heat recovery load 10 ... Hot water supply as exhaust heat recovery load Equipment 16: Three-way valve constituting heat radiation amount changing means 17 ... Bypass pipe constituting heat radiation amount changing means 18 ... Heat radiation heat exchanger 19 ... Cooling water temperature sensor 20 ... Load side circulating water temperature sensor 21 ... Flow switch 22 ... Comparator as exhaust heat recovery amount detection means 24 feedback control means 27 hold means 28 feedforward control means

Claims (2)

[Claims] An exhaust heat recovery heat exchanger (6) is connected to an engine cooling section of an engine (1) and a waste heat recovery heat exchanger (6) via a cooling water circulation pipe (5). To the exhaust heat recovery load via a load side circulation pipe (8) with a circulation pump (7) interposed, and the cooling water circulation pipe (5) is On the downstream side, the cooling water circulation pipe
In (5), a heat exchanger (1)
8), and a cooling water temperature sensor (19) for measuring the temperature of the cooling water returned to the engine cooling section in the cooling water circulation pipe (5) downstream of the heat radiation amount changing means (16). )
In the exhaust heat recovery system configured to operate the heat radiation amount changing means (16) based on the temperature of the cooling water measured by the cooling water temperature sensor (19), the load-side circulation pipe (8 A load-side circulating water temperature sensor (20) that is provided downstream of the exhaust heat recovery load and measures the temperature of the load-side circulating water flowing therethrough, and the load-side circulating water temperature sensor (20). Comparing the measured temperature of the load side circulating water with the first set temperature and outputting a heat radiation signal when the temperature of the load side circulating water is equal to or higher than the first set temperature; Provided on the load-side circulation pipe (8), detects whether the flow state of the load-side circulating water is a predetermined flow state or another abnormal flow state, and generates a heat radiation signal along with the detection of the abnormal flow state. A flow state detecting means (21) to output, and the cooling water temperature sensor ( A holding means (27) for outputting a heat radiation signal until the measured temperature of the cooling water according to (19) becomes lower than the second set temperature; and a valve opening of the heat radiation amount changing means (16) in response to the heat radiation signal. When the engine (1) is in rated operation and the exhaust heat demand of the exhaust heat recovery load is zero, the heat radiating heat exchanger
(18) a feedforward-side control means (28) for outputting a control output so that a preset valve opening is set to an opening smaller than a valve opening for flowing an amount of cooling water to be supplied to the cooling water temperature sensor; Based on the measured temperature of the cooling water according to (19), feedback-side control means (24) for outputting a control output for controlling the heat radiation amount changing means (16) so that the heat radiation increases as the measured temperature increases. The heat radiation amount changing means (16) is configured to be controlled by a control output obtained by adding a control output from the feed forward control means (28) and a control output from the feedback control means (24). An exhaust heat recovery system, characterized in that: 2. The holding means (27) according to claim 1,
The measured temperature of the load side circulating water by the load side circulating water temperature sensor (20) is lower than its set temperature (Ta), and the measured temperature of the cooling water by the cooling water temperature sensor (19) is the set temperature.
An exhaust heat recovery system that outputs a heat radiation signal until the temperature becomes lower than (Tb).