JPH07247835A - Exhaust heat recovery system - Google Patents

Abstract

PURPOSE:To improve exhaust heat recovery efficiency by increasing a temperature of cooling water to be supplied to an engine cooling part to maximum without generating engine trip. CONSTITUTION:An absorbing type refrigerator and a hot water unit are connected to an engine cooling part in order to utilize its cooling exhaust heat. A heat exchanger for exhaust heat is connected to a cooling water supplying side piping lead to the engine cooling part through a three-directional valve 12 and a bypass piping. A temperature T1 of the cooling water to be supplied to the three-directional valve 12 is measured by means of an inlet temperature sensor 15. In addition, a temperature T2 of the cooling water in the bypass piping at an outlet side from the exhaust heat exchanger is measured by means of an outlet temperature sensor 16. An opening V of the three-directional valve 12 is controlled by the following equation based on the inlet temperature Tl, the outlet temperature T2, and a set temperature Tset : V=(Tset-T2)/(T1-T2).

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.
The exhaust heat recovery unit of the absorption chiller, hot water supply equipment, heating device, etc. is connected via a pipe, and the flow distribution unit such as a three-way valve is connected to the cooling water supply side pipe from the exhaust heat recovery unit to the engine cooling unit. And an exhaust heat recovery system connected to a heat exchanger for exhaust heat via a bypass pipe.

[0002]

2. Description of the Related Art In the above-mentioned exhaust heat recovery system, generally, a cooling water temperature sensor for measuring the temperature of the cooling water supplied to the engine cooling section is provided downstream of the bypass pipe of the cooling water supply side pipe. Along with this, there is provided a flow rate distribution control means for operating the flow rate distribution means so that the temperature of the cooling water measured by the cooling water temperature sensor becomes the set temperature, and the temperature of the cooling water supplied to the engine cooling section becomes the set temperature. Thus, the amount of cooling water distributed and supplied to the heat exchanger for exhaust heat is controlled. As a result, the temperature of the cooling water in the cooling jacket rises too much, the engine protection circuit operates, and the so-called engine trip, which automatically stops the engine, can be avoided.

[0003]

However, in the conventional example, when the exhaust heat demand sharply decreases, for example, when the cooling load of the air conditioner sharply decreases, a three-way valve is used in the wake of the exhaust flow. Even if an exhaust heat heat exchanger for lowering the water temperature is provided, if the water temperature rises sharply, the exhaust heat heat exchanger does not fully remove heat, and the cooling water temperature overshoots the set temperature, resulting in high-temperature 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.

The present invention has been made in view of such circumstances, and the exhaust heat recovery system of the invention according to claim 1 is a cooling system to be supplied to an engine cooling section without causing an engine trip. The purpose is to raise the temperature of water as much as possible to improve the exhaust heat recovery efficiency, and in the exhaust heat recovery system of the invention according to claim 2, the load fluctuation in the exhaust heat recovery unit can be specified in advance. In such a case, the purpose is to be able to respond favorably to the peak of the load, and the exhaust heat recovery system of the invention according to claim 3 is
The purpose is to be able to reasonably incorporate into a ready-made control system.

[0006]

In order to achieve the above-mentioned object, an exhaust heat recovery system according to a first aspect of the present invention connects an engine cooling section and an exhaust heat recovery section via a pipe. In an exhaust heat recovery system in which a heat exchanger for exhaust heat is connected to a cooling water supply side pipe from the exhaust heat recovery unit to the engine cooling unit via a flow distribution means and a bypass pipe, the exhaust heat recovery unit is used. An inlet temperature sensor that measures the temperature of the cooling water between the point where the cooling water and the cooling water that does not pass through and the heat exchanger for exhaust heat are measured, and the cooling water in the bypass pipe on the outlet side from the heat exchanger for exhaust heat An outlet temperature sensor for measuring the temperature of the cooling water is provided, and the flow rate distribution means is based on the following relationship based on the inlet temperature of the cooling water measured by the inlet temperature sensor and the outlet temperature of the cooling water measured by the outlet temperature sensor and the set temperature. Flow rate controlled by formula Constituting provided control means. Relational expression V = (Tset-T2) / (T1-T2) V: ratio of the amount of cooling water not supplied to the exhaust heat heat exchanger side to the total amount of cooling water supplied to the engine cooling unit Tset: set temperature T1: inlet Cooling water inlet temperature measured by temperature sensor T2: Cooling water outlet temperature measured by outlet temperature sensor

As the exhaust heat recovery section, a hot water absorption type refrigerator, hot water supply equipment, vapor compression type refrigerator, heating device, etc. are used.

Further, the exhaust heat recovery system of the invention according to claim 2 is the same as that of claim 1 in order to achieve the above object.
Set temperature changing means for automatically changing the set temperature in the exhaust heat recovery system of the invention according to the invention in accordance with a preset time zone such that the set temperature becomes higher in a time zone in which the amount of exhaust heat recovered by the exhaust heat recovery section is higher. And is configured.

The exhaust heat recovery system of the invention according to claim 3 is the same as that of claim 1 in order to achieve the above object.
Alternatively, in the exhaust heat recovery system according to claim 2, a cooling water temperature sensor for measuring the temperature of the cooling water supplied to the engine cooling unit is provided downstream of the bypass pipe of the cooling water supply side pipe. , Equipped with steady flow distribution control means for operating the flow distribution means so that the temperature of the cooling water measured by the cooling water temperature sensor becomes the set temperature, and the inlet temperature of the cooling water measured by the inlet temperature sensor is equal to or higher than the set temperature. Only in this case, the operation state switching means for switching the operation state so as to operate the flow rate distribution control means in preference to the steady flow rate distribution control means is provided.

[0010]

According to the constitution of the exhaust heat recovery system of the invention as set forth in claim 1, even if the temperature of the cooling water returned to the flow rate distribution means becomes high due to the rapid decrease in the exhaust heat demand amount, the temperature of the cooling water is increased accordingly. Immediately actuating the flow rate distribution means to increase the flow rate of the cooling water flowing to the heat exhaust heat exchanger. On the other hand, even if the exhaust heat demand rapidly increases and the temperature of the cooling water returned to the flow rate distribution unit becomes low, the flow rate distribution unit is immediately activated and the heat exhaust heat exchanger is replaced. Reduce the flow rate of cooling water.
By these controls, it is possible to accurately suppress the temperature change of the cooling water supplied to the engine cooling unit regardless of the rapid change in the exhaust heat demand amount.

Further, according to the configuration of the exhaust heat recovery system of the second aspect of the present invention, when the temporal variation in one day can be grasped in advance such as the cooling load, that is, the exhaust heat demand. When the change in quantity over time can be specified in advance, when the exhaust heat demand increases, the set temperature is made as high as possible, the temperature of the cooling water taken out from the engine cooling section is made high, and it is sent to the exhaust heat recovery section. The temperature of the cooling water can be raised.

According to the structure of the exhaust heat recovery system of the third aspect of the invention, the ready-made steady flow rate distribution control for controlling the flow rate distribution means by measuring the temperature of the cooling water supplied to the engine cooling section. When there is no fear that the temperature of the cooling water supplied to the engine cooling unit will be unnecessarily high, it is controlled by an off-the-shelf steady-state flow distribution control means, while the exhaust heat demand sharply decreases. When there is a risk that the temperature of the cooling water returned to the flow distribution means will rise above the set temperature and the temperature of the cooling water supplied to the engine cooling section will rise to an unnecessarily high temperature, the flow distribution control means will be given priority. Can act by letting it work.

[0013]

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

FIG. 1 is a block diagram showing an embodiment of an exhaust heat recovery system according to the present invention, in which a generator 3 is interlocked with a gas engine 1 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.
Are connected. An absorption refrigerator 6 as an exhaust heat recovery unit and hot water supply equipment 7 are connected to the main pipe 5 in parallel with each other via a feed pipe 8a and a return pipe 8b. Further, the absorption refrigerating machine 6 is connected with cooling devices 11 ... Through a cooling pipe 10 in which a second pump 9 is interposed,
The exhaust heat generated by cooling the engine is used as a heat source for cooling and hot water supply. The main pipe 5, the feed pipe 8a, and the return pipe 8b are collectively referred to as pipes.

In addition, a heat exchanger for exhaust heat is provided to a cooling water supply side pipe downstream of a connection point of the main pipe 5 with the return pipe 8b via a three-way valve 12 and a bypass pipe 13 as flow rate distributing means. 14 is connected. The three-way valve 12 may be provided on the outlet side of the heat exchanger 14 for exhaust heat.

The cooling water supplied to the three-way valve 12, that is, the upstream side of the three-way valve 12 of the cooling water supply side pipe,
An inlet temperature sensor 15 for measuring the temperature of the cooling water on the inlet side to the heat exchanger 14 for exhaust heat is provided. In addition, an outlet temperature sensor 16 that measures the temperature of the cooling water cooled by the heat exchanger 14 for exhaust heat is provided in the bypass pipe 13 on the outlet side from the heat exchanger 14 for exhaust heat. Further, a cooling water temperature sensor 17 that measures the temperature of the cooling water supplied to the engine cooling unit is provided downstream of the bypass pipe 13 of the cooling water supply side pipe.

Inlet temperature sensor 15 and outlet temperature sensor 16
And the cooling water temperature sensor 17 are each connected to a microcomputer 18, and the microcomputer 18
Is connected to the driver 19 of the three-way valve 12.

As shown in the block diagram of FIG. 2, the microcomputer 18 is provided with an opening degree calculating means 20, a set temperature changing means 21, first and second comparing means 22 and 23, and an operating state switching means 24. Has been.

In the opening degree calculating means 20, the inlet temperature sensor 1
5, the inlet temperature T1 of the cooling water, the outlet temperature T2 of the cooling water measured by the outlet temperature sensor 16, and the set temperature Tset from the set temperature changing means 21 are input, and the three-way valve 12 is opened by the following relational expression. The degree V is calculated, and a command signal according to the calculated opening degree V is output to the driver 19 via the action state switching means 24. Relational expression V = (Tset-T2) / (T1-T2) V: Ratio of the amount of cooling water not supplied to the exhaust heat heat exchanger 14 side to the total amount of cooling water supplied to the engine cooling unit Tset: Set temperature T1: Coolant inlet temperature measured by inlet temperature sensor 15 T2: Coolant outlet temperature measured by outlet temperature sensor 16

The set temperature changing means 21 receives a time signal from the clock 25 every set time such as 5 seconds,
In response to this, the data stored in the set temperature table 26 is read, the set temperature Tset for each time is read, and sent to the opening degree calculation means 20.

The set temperature Tset for each time is set to 83 ° C. with a peak at 2:00 pm, and
Set the lowest value at 7am and 9pm to 75 ° C,
The middle part is set so as to ride on a curve obtained by averaging based on past data. The time signal from the clock 25 can be stopped as appropriate during the intermediate period or winter. By changing the set temperature Tset by the set temperature changing means 21, the temperature of the cooling water supplied to the engine cooling section is raised as much as possible when the cooling load in the summer reaches a peak, and the amount of exhaust heat energy obtained is increased. It is configured to be able to.

In the first comparing means 22, the temperature T of the cooling water supplied to the engine cooling section measured by the cooling water temperature sensor 17 is inputted, and the temperature and the first set temperature Ta (for example, 75 ° C.) are inputted. In comparison with the measured temperature T is the first set temperature Ta
When it is higher than the above, a closing signal is output, and the amount of cooling water flowing to the exhaust heat exchanger 14 is increased on the side where the opening degree becomes small, and conversely, the measured temperature T is higher than the first set temperature Ta. When it is too low, an open signal is output and the opening becomes larger,
That is, command signals are output to the driver 19 via the action state switching means 24 so as to reduce the amount of cooling water flowing to the exhaust heat heat exchanger 14.

In the second comparing means 23, the inlet temperature T1 of the cooling water measured by the inlet temperature sensor 15 is input, and the temperature is compared with the second set temperature Tb (for example, 85 ° C.),
When the measured temperature is higher than the second set temperature Tb, a priority signal is output to the operating state switching means 24 to set the inlet temperature T1.
And the outlet temperature T2, the opening degree of the three-way valve 12 is preferentially controlled. On the contrary, when the measured temperature is lower than the second set temperature Tb, a steady signal is output to the operating state switching means 24. The control mode is switched so that the opening degree of the three-way valve 12 is controlled only based on the temperature T of the cooling water supplied to the engine cooling unit.

Next, the control operation according to the above configuration will be described with reference to the flowchart of FIG. First, the inlet temperature T1 is input (S1) and compared with the second set temperature Tb (S).
2). Here, when the measured temperature is equal to or higher than the second set temperature Tb, the outlet temperature T2 is input (S3), and the set temperature Tset for each time input from the set temperature changing means 21.
And the inlet temperature T1 and the outlet temperature T2 are substituted into the relational expression to calculate the opening degree V (S4), and the opening degree signal corresponding to the calculated opening degree V is output (S5). Adjust the opening. The control of steps S3, S4 and S5 corresponds to the flow rate distribution control means.

In step S2, when the measured temperature is lower than the second set temperature Tb, the temperature T of the cooling water supplied to the engine cooling portion is input (S6), and then the cooling water temperature T and the first Compare with the set temperature Ta (S
7).

Here, the cooling water temperature T is the first set temperature T
When it is equal to or more than a, a close signal is output (S8), the flow rate of the cooling water flowing to the heat exchanger 14 for exhaust heat is increased, and the three-way valve is set so that the cooling water temperature T becomes the first set temperature Ta. 12
Adjust the opening of. On the other hand, when the cooling water temperature T is lower than the first set temperature Ta, an opening signal is output (S
9) The flow rate of the cooling water flowing to the heat exchanger 14 for exhaust heat is reduced to adjust the opening degree of the three-way valve 12 so that the cooling water temperature T reaches the first set temperature Ta. This step S6,
The control of S7, S8 and S9 corresponds to the steady flow distribution control means.

Next, the result of the simulation according to the above embodiment will be described. As the three-way valve 12, an operating time of 30 seconds from fully closed to fully opened was used. Flow rate 1
00 m ³ , the cooling temperature difference in the exhaust heat heat exchanger 14 was set to 10 ° C., and the transfer characteristic in the exhaust heat heat exchanger 14 was set to 1 / (1 + 5 s). However, s is a Laplace transformer in the transfer function. In addition, the dead time from when the input is applied until the output is affected is set to 10 seconds.

Under the above-mentioned conditions, changes in the temperature of the cooling water supplied to the engine cooling portion (shown by 1) and the temperature of the cooling water immediately before supplied to the three-way valve 12 (shown by 2) were examined. However, as shown in the graph of FIG. 4, the temperature of the cooling water immediately before being supplied to the three-way valve 12 is 75 ° C. to 85 ° C.
Even if the temperature changes to 1, the outlet temperature is maintained near 75 ° C, and the heat for exhaust heat does not change regardless of the sudden change in the temperature of the cooling water immediately before being supplied to the three-way valve 12 due to the rapid decrease in the exhaust heat demand. It is clear that the amount of cooling water supplied to the exchanger 14 can be accurately controlled to maintain the temperature of the cooling water supplied to the engine cooling unit close to the preset temperature and suppress the temperature change.

The inlet temperature sensor 15, the outlet temperature sensor 16 and the opening degree calculating means 20 calculate the opening degree of the three-way valve 12 based on the inlet temperature T1, the outlet temperature T2 and the set temperature Tset of the cooling water, A drive signal is output to the driver 22 so that the calculated opening degree is obtained, and the three-way valve 12 is automatically operated so that the cooling water inlet temperature T1 increases and the amount of cooling water supplied to the exhaust heat heat exchanger 14 increases. It is called a flow rate distribution control means having a structure for performing the operation control.

In the above embodiment, the three-way valve 12 is used to change the flow rate of the cooling water flowing through the heat exchanger 14 for exhaust heat. For example, the cooling water supply side pipe of the main pipe 5 and the bypass pipe 13 are respectively provided. It may be configured such that a flow rate adjusting valve is individually provided, and both flow rate adjusting valves are interlocked with each other to change the flow rate of the cooling water flowing to the heat exchanger 14 for exhaust heat. Collectively referred to as flow rate distribution means.

[0032]

As is apparent from the above description, according to the exhaust heat recovery system of the first aspect of the present invention, the amount of exhaust heat demand sharply decreases and the cooling water returned to the flow distribution means is returned. Immediately responding to temperature changes, the flow distribution means is activated to change the flow rate of the cooling water flowing to the heat exchanger for exhaust heat, and the cooling that is supplied to the engine cooling unit regardless of sudden changes in the exhaust heat demand. Since the temperature change of water is accurately controlled, the temperature of the cooling water supplied to the engine cooling section can be made as high as possible and the exhaust heat recovery efficiency can be improved without causing an engine trip.

According to the exhaust heat recovery system of the second aspect of the invention, as the load on the exhaust heat recovery section becomes higher, the engine cooling section becomes more responsive to the temporal change in the exhaust heat demand that can be specified in advance. Since the temperature of the cooling water taken out is raised and the temperature of the cooling water sent to the exhaust heat recovery unit is raised, it is also good for the peak load when the load fluctuation in the exhaust heat recovery unit can be specified in advance. It has become possible to deal with.

Further, according to the exhaust heat recovery system of the third aspect of the present invention, an off-the-shelf steady flow rate distribution control means for controlling the flow rate distribution means by measuring the temperature of the cooling water supplied to the engine cooling section is provided. When used together, the exhaust heat demand sharply decreases and the temperature of the cooling water returned to the flow distribution means becomes higher than the set temperature, and the temperature of the cooling water supplied to the engine cooling part becomes higher than necessary. Only when there is a risk, the flow distribution control means is given priority and acts, so that it is possible to rationally incorporate the existing control system while making the most of it.

[Brief description of drawings]

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

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

FIG. 3 is a flowchart.

FIG. 4 is a graph.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Gas engine 5 ... Main piping 6 ... Absorption type refrigerator 7 ... Hot water supply equipment 8a ... Feed piping 8b ... Return piping 12 ... Three-way valve 13 ... Bypass piping 14 ... Exhaust heat heat exchanger 15 ... Inlet temperature sensor 16 ... Outlet Temperature sensor 17 ... Cooling water temperature sensor 21 ... Set temperature changing means 24 ... Working state switching means

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location F28F 27/00 511 M

Claims (3)

[Claims] 1. An engine cooling unit and an exhaust heat recovery unit are connected via a pipe, and a cooling water supply side pipe from the exhaust heat recovery unit to the engine cooling unit is connected via a flow distribution means and a bypass pipe. In the exhaust heat recovery system in which a heat exchanger for exhaust heat is connected, the temperature of the cooling water between the location where the cooling water passing through the exhaust heat recovery unit and the cooling water not passing through and the heat exchanger for exhaust heat are combined. And an outlet temperature sensor for measuring the temperature of the cooling water in the bypass pipe on the outlet side from the heat exchanger for exhaust heat are provided, and the flow distribution means is measured by the inlet temperature sensor. Exhaust heat recovery system provided with a flow rate distribution control means for controlling the operation according to the following relational expression based on the inlet temperature of the cooling water and the outlet temperature of the cooling water measured by the outlet temperature sensor and the set temperature. . Relational expression V = (Tset-T2) / (T1-T2) V: ratio of the amount of cooling water not supplied to the exhaust heat heat exchanger side to the total amount of cooling water supplied to the engine cooling unit Tset: set temperature T1: inlet Cooling water inlet temperature measured by temperature sensor T2: Cooling water outlet temperature measured by outlet temperature sensor 2. The set temperature according to claim 1 is set to be higher in a time zone in which the amount of exhaust heat recovered by the exhaust heat recovery unit is higher.
An exhaust heat recovery system equipped with set temperature changing means that changes automatically according to a preset time period. 3. The exhaust heat recovery system according to claim 1, wherein the temperature of the cooling water supplied to the engine cooling unit is measured downstream of the bypass pipe of the cooling water supply side pipe. And a steady flow rate distribution control means for operating the flow rate distribution means so that the temperature of the cooling water measured by the cooling water temperature sensor is set to a set temperature, and is measured by the inlet temperature sensor. An exhaust heat recovery system provided with an operating state switching means for switching the operating state so that the flow rate distribution control means operates in preference to the steady flow rate distribution control means only when the inlet temperature of the cooling water is equal to or higher than the set temperature.