JPH02104954A - Device for recovering exhaust heat of engine - Google Patents

Abstract

PURPOSE:To reduce the temperature change of a heat recovering liquid by operating a variable flow-dividing valve more to a heat radiation increasing side by means of a flow-dividing rate control device as a cooling water temperature gets higher and increasing the flow-dividing rate on the heat radiating side of the cooling water. CONSTITUTION:When the heat radiating quantity of an engine exhaust heat from a heat exchanger 6 is reduced due to a reduced heat recovering quantity or when an engine exhaust heat itself is increased due to increase in the load of an engine E, the temperature of cooling water in an engine cooling water passage 11 is increased. This is detected by a temperature sensor 13 and a flow-dividing rate control device 14 controls a variable flow-dividing valve 12 to be on a heat radiating rate increasing side to make the cooling water dividingly flow in a larger quantity on a heat radiating passage 10 side whereas in a smaller quantity on a heat-recovering discharge-side water passage 7 side, thereby increasing the heat radiating rate of the exhaust heat of the engine E. Hence, the changing width of cooling water temperature passing through the heat-recovering discharge-side water passage 7 of the heat exchanger 6 can be reduced while reducing the temperature change of a heat recovering liquid which recovers heat therefrom and which is discharged out of a heat-recovering heat absorbing side liquid passage of the heat exchanger 6.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for recovering exhaust heat from an engine, such as engine body heat and exhaust heat. To provide something that can prevent the engine from overheating by keeping it within the temperature range.

<Prior art> As shown in FIG. 1 or 4, the basic structure of the engine exhaust heat recovery device to which the present invention is applied is that a heat exchanger 3 for absorbing exhaust heat is installed in the water jacket 2 of the engine E. This system is constructed by connecting an exhaust heat absorption path 4, a hot water path 5, an endothermic side water path 7 for heat recovery of a heat exchanger 6 for recovering engine exhaust heat, and a cold water path 8 in series in a circulating manner.

As a prior art of this type, US Pat. No. 4,226,21
As shown in Publication No. 4 (see Figure 4), an engine E and a generator G are interlocked, and the generator G generates electricity, and the engine body heat absorbed by the water jacket 2,
The exhaust heat absorbed in the exhaust heat absorption path 4 is radiated in the engine exhaust heat recovery heat exchanger 6, and the exhaust heat of the engine E is recovered from the heat recovery side water channel 15 of the heat exchanger 6. There is something configured like this.

Reference numeral 50 designates a three-way switching valve that short-circuits the cooling waterway directly from the hot waterway 5 to the cold waterway 8 when the engine E is started, so that the engine E can be warmed up quickly.

<Problems to be Solved by the Invention> However, in the above conventional technology, when the amount of heat recovered from the engine exhaust heat recovery heat exchanger 6 decreases due to external factors such as seasonal factors and number of people, the engine E Since the rate at which the exhaust heat is radiated to the heat recovery liquid side in the heat exchanger 6 decreases, the cooling water temperature rapidly rises, causing the engine E to overheat, and causing sudden thermal stress to the exhaust heat absorption heat exchanger 3. There is a risk that the heat exchanger 3 will be damaged by heat.

In addition, even if the amount of heat recovery is constant, if the load on the engine generator increases, even though the exhaust heat of engine E increases, the heat radiation rate does not increase commensurately, so engine E still overheats. There is a possibility that

Moreover, as described above, if the amount of heat recovered from the heat exchanger 6 decreases or the load on the engine E increases, the heat exchanger 6
The temperature of the cooling water flowing through the heat recovery discharge side waterway 7 rises rapidly, and the outlet temperature of the hot water on the side of the heat recovery endothermic side waterway 15 that exchanges heat with it also rises rapidly. When the amount of water increases or the load on the engine E decreases, the temperature of hot water coming out from the heat recovery side water channel 15 of the heat exchanger 6 decreases rapidly, and the heat recovery load on the heat exchanger 6 and the load on the engine E decrease. There is a problem in that the temperature of the hot water fluctuates rapidly and is not constant due to changes in the temperature.

The present invention prevents the engine from overheating or the exhaust heat absorption heat exchanger from being thermally damaged even when the heat recovery load of the heat exchanger or the engine load changes, and the heat exchanger for exhaust heat absorption The technical problem is to reduce the temperature change of the heat recovery liquid exiting from the heat recovery waterway on the heat absorption side of the heat exchanger.

<Means for Solving the Problems> Means for solving the above problems will be described below using drawings corresponding to embodiments.

That is, the present invention provides an engine exhaust heat recovery device having the above-mentioned basic structure, in which the heat radiation path 10 of the radiator 1 is connected in parallel to the heat recovery discharge side water channel 7 of the engine exhaust heat recovery heat exchanger 6, An engine cooling waterway 11 consisting of a cold waterway 8, a water jacket 2, an exhaust heat absorption path 4, and a hot waterway 5 is connected to a heat recovery discharge side waterway 7 and a heat radiation path 10 using a variable flow divider valve 12.
A temperature sensor 13 is provided in the engine cooling water channel 11, and a flow rate control device 1 is connected to the temperature sensor 13.
4, the variable flow dividing valve 12 is linked to control the flow dividing ratio,
The temperature sensor 13 detects the temperature of the engine cooling water passing through the engine cooling water channel 11, and the detected temperature T of the cooling water temperature is the set temperature T for starting heat radiation.
1 (L) and higher temperature T1 (
H), the higher the detected temperature of the cooling water, the more the division ratio control device 14 operates the variable division valve 12 to increase the amount of heat radiation, and the engine cooling water 11 to the heat radiation path IO, and decrease the heat recovery side distribution rate of the cooling water to the heat recovery discharge side waterway 7, and the lower the detected temperature of the cooling water, the lower the detected temperature of the cooling water. It is characterized in that the division ratio control device 14 operates the variable division valve 12 to the heat radiation loss side to decrease the heat radiation side division ratio and increase the heat recovery side division ratio.

Effect> When the cooling water temperature T1 of the engine cooling waterway 11 is within the temperature range A for heat radiation control, (1) The amount of heat recovered from the heat recovery device is reduced due to external factors, and the amount of heat recovered from the heat exchanger 6 is reduced. When the amount of heat dissipated from the engine exhaust heat decreases, or when the load on the engine E increases and the engine exhaust heat itself increases, the cooling water aTl in the engine cooling water passage 11 tends to rise, but the temperature sensor 13 detects this. , the diversion rate control device 14 that has obtained the information on the increase in the cooling water temperature T, controls the variable diversion valve 12 to increase the heat radiation rate, thereby diverting a large amount of the cooling water to the heat radiation path 10 side for heat recovery. A small amount of water is diverted to the discharge side waterway 7,
Since the heat dissipation rate of the exhaust heat of the engine E is increased, the increase in the cooling water temperature TI is suppressed.

(2) Conversely, the amount of heat recovered from the heat recovery device increases due to external factors, and the amount of heat released from the engine exhaust from the heat exchanger 6 increases, or the load on the engine E decreases, causing the engine When the exhaust heat itself decreases, the cooling water temperature T1 of the engine cooling waterway 11 tends to decrease, but the diversion ratio control device 14, which has obtained information about the decrease in the cooling water temperature T1 through the detection of the temperature sensor 13, operates the variable diversion valve. 12 to the side where the heat radiation rate decreases, less cooling water is diverted to the heat radiation path IO side, and more of the cooling water is diverted to the heat recovery discharge side waterway 7 side, thereby lowering the heat radiation rate of the exhaust heat of the engine E. Therefore, the decrease in the cooling water temperature T1 is suppressed.

In addition, as described above, the engine exhaust heat recovery heat exchanger 6
Even if the amount of heat recovered from the engine or the load on the engine E changes, the cooling water temperature T1 of the cooling water channel 11 is maintained within a constant temperature range.
The fluctuation range of the temperature of the cooling water passing through the cooling water becomes small, and the temperature change of the heat recovery liquid that recovers heat from this cooling water and exits from the heat recovery endothermic side liquid path of the heat exchanger 6 can also be reduced.

<Effects of the Invention> (1) Even if the amount of heat recovered from the engine exhaust heat recovery heat exchanger decreases due to external factors or the engine load increases, the engine exhaust heat increases, it will not work in conjunction with the temperature sensor. The diversion function of the variable diversion valve suppresses the temperature rise of the cooling water flowing through the cooling waterway within a certain range, which not only smoothly prevents engine overheating but also prevents heat damage to the exhaust heat absorption heat exchanger. let

(2) Even if the amount of heat recovered from the engine exhaust heat recovery heat exchanger or the engine load changes, the cooling water temperature in the cooling waterway is maintained within a constant temperature range, so the heat exchanger for engine exhaust heat recovery The temperature change of the heat recovery liquid flowing out from the heat absorption side liquid path of the vessel can be suppressed to a small level.

<Example> Hereinafter, embodiments of the present invention will be described based on the drawings.

Fig. 1 is a system principle diagram of a cogeneration engine power generation device, and Fig. 2 is a diagram showing the relationship between cooling water temperature and radiator side cooling water flow rate in the same device. and the generator '1411G are interlocked in the front and rear direction to generate electricity and at the same time recover the engine exhaust heat, which is the engine body heat and the exhaust heat.

A water jacket 2 is formed in the cylinder block and cylinder head of the gas engine E, and an exhaust heat absorption heat exchanger 3 and a muffler 20 are attached to the exhaust path 21 of the engine E in this order.

In addition, a radiator 1 is attached to the engine E so that engine exhaust heat can be radiated outside the system, and a heat exchanger 6 for recovering engine exhaust heat is attached to the heat recovery discharge side of the heat exchanger 6. The engine exhaust heat is released in the water channel 7, the exhaust heat is recovered in the heat absorption side water channel 15 for heat recovery, and the hot water taken out from the heat absorption side water channel 15 is stored in the hot water tank 23 and used for hot water supply. configured.

Reference numeral 24 denotes a control device that controls the cooling fan 25 of the radiator 1, the circulation pump 22 (described later), the pressure reducing valve of the gas fuel introduction path, and the like.

The above two are combined into a jacket 2 and a heat exchanger 3 for absorbing exhaust heat.
The exhaust heat absorption path 4 and the heat-exchanged cooling water are transferred to the engine E.
A hot waterway 5 led out from the engine, a cold waterway 8 that introduces the cooling water before heat exchange to the engine E, and a circulation pump 22 are connected in a serial circulation manner, and between the hot waterway 5 and the cold waterway 8, The heat radiation path 10 passing through the radiator 1 and the heat recovery discharge side water channel 7 of the engine exhaust heat recovery heat exchanger 6 are communicated in parallel.

However, the reference numeral 26 is a thermostatic valve, and the hot water channel 5
The valve 26 is disposed at the branch inlet of the bypass passage 27 which branches into the cold water channel 8 in a short-circuit manner.
, the cooling water is short-circuited from the hot water channel 5 to the cold water channel 8, and the amount of heat dissipated is minimized to enable early warm-up.

A variable flow dividing valve 12 consisting of a three-way valve is interposed at a portion where the heat radiation path 10 and the heat recovery discharge side waterway 7 are bifurcated from the hot waterway 5, and a temperature sensor 13 is attached to the hot waterway 5. The variable flow dividing valve 12 is connected to the temperature sensor 13 via the flow dividing ratio control device 14 so as to be able to control the flow dividing ratio, so that even if the engine load or the heat recovery load fluctuates, the temperature of the hot water flowing in the hot water channel 5 is kept within a certain range. Configured to hold within.

That is, the temperature range A for heat radiation control is applied to the division ratio control device 14.
and set the lower limit of this area A as the heat radiation start temperature TI(L)
The upper limit is the temperature T1 (H
), the variable flow divider valve 12 is operated as follows (
Control as in 1) to (3) to change the division ratio into two flow paths: ■ Hot water channel 5 → heat radiation path 10 ■ Hot water channel 5 → heat recovery discharge side water channel 7 of heat exchanger 6 , configured to vary the ratio of heat dissipation and heat recovery.

However, as a matter of course, T 1 (L) < T 1 (H), and in practice, it is best to maintain the temperature of the waste water from the engine E at around 90°C, so the temperature is ±3 around this temperature. °
C, T1(L) is 87°C, T1(H) is 9
Each was set at 3°C.

Further, the variable flow dividing valve 12 is not limited to the three-way valve as in the embodiment, but may be a normal two-way valve that connects the heat radiation path 10 branched from the hot water channel 5 and the heat recovery discharge side water channel 7, as shown in FIG. Directional metering valves 12a may be provided respectively, and these may be configured to cooperate with one flow rate control device 14.

(1) When detected temperature T is less than heat radiation start temperature TI (L) (
In other words, when the hot water temperature drops abnormally), as shown in FIG. The engine cooling water that has absorbed engine exhaust heat is controlled to have a diversion rate of 100% to the hot water channel 5.
All of the heat flows from the heat exchanger 6 through the variable flow divider valve 12 to the heat recovery discharge waterway 7 of the heat exchanger 6, minimizing the heat radiation rate, suppressing a drop in hot water temperature, and recovering engine exhaust heat at an extremely high rate. The water is collected in the endothermic side waterway 15.

After the heat has been recovered by the heat exchanger 6, the cooling water passes through the cold water channel 8, returns to the water jacket 2 of the engine E by the circulation pump 22, and absorbs the exhaust heat of the engine E again.

In this control, in order to avoid hunting, the heat dissipation side division ratio is maintained at 0% until the hot water temperature rises to a temperature considerably higher than the heat dissipation start temperature T 1 (L).

(2) When heat radiation start temperature T1 (L) ≦ detected temperature T, ≦ total radiation temperature TI (H) (i.e.,
(When the hot water temperature is in the normal temperature range) As shown in FIG. 2, the variable flow dividing valve 12 is controlled by the flow dividing ratio control device 14 as follows.

(2) As the detected temperature T1 becomes higher, the heat radiation side diversion rate to the heat radiation path IO is increased, and the heat recovery side diversion rate to the heat recovery discharge side water channel 7 is decreased.

(2) As the detected temperature T1 becomes lower, the heat radiation side diversion rate to the heat radiation path 10 is decreased, and the heat recovery side diversion rate to the heat recovery discharge side waterway 7 is increased.

Therefore, as the detected temperature T becomes higher, the division rate of cooling water from the hot water channel 5 to the heat radiation path 10 increases, the heat radiation ratio of the cooling water becomes thicker, and the hot water temperature of the hot water channel 5 quickly decreases. .

As a result, the temperature of the hot water coming out of the heat recovery endothermic side water channel 15 of the heat exchanger 6 is also quickly lowered and adjusted to an appropriate temperature.

Conversely, when the detected temperature T1 becomes lower, the distribution rate of the cooling water from the hot water channel 5 to the heat recovery discharge side water channel 7 increases, the heat radiation rate of the cooling water decreases, and the hot water temperature of the hot water channel 5 decreases. Rise quickly.

As a result, the temperature of the hot water coming out of the heat recovery endothermic water channel 15 of the heat exchanger 6 also rises quickly and is adjusted to an appropriate temperature.

(3) In the case of total release temperature T1 (H) < detection temperature T, (
In other words, when the hot water temperature rises abnormally), as shown in FIG.
The cooling water flowing out from the engine E flows from the hot water channel 5 through the variable diverter valve 12 into the heat radiation path 10, and the engine exhaust heat stored in the cooling water is removed. / Heat is radiated outside the stem system at a very large rate to quickly prevent overheating of the engine E and quickly lower the temperature of the hot water flowing through the hot water channel 5.

As described above, in this control as well, in order to avoid hunting, the heat dissipation side division ratio is maintained at 100% until the hot water temperature all falls to a temperature considerably lower than the heat dissipation temperature T1 (H).

However, when the variable flow diverter valve 1 is
2 is left behind and engine E stops, there is a risk that when engine E is restarted, heat dissipation efficiency remains low and engine E overheats. When configured to detect with a sensor (for example, an engine rotation speed detection sensor, a throttle valve position detection sensor of a gas fuel/air mixer, etc.) and control the heat radiation side division ratio of the variable distribution valve 12 to 100%, Heat dissipation efficiency is made sufficiently high to smoothly prevent engine overheating during startup.

As described above, the present invention allows cooling water that has absorbed engine exhaust heat to be routed between the heat radiation path of the radiator and the heat recovery waterway of the heat exchanger by the action of the variable flow dividing valve linked to the temperature sensor via the control device. The engine E is not limited to an engine generator, but may also be another engine working machine such as an engine compressor or an engine welder, or the engine alone.

Further, the heat radiator 1 is not limited to a radiator, but may be a condenser or a hopper.

The temperature sensor 13 includes a cooling water channel 11 consisting of a hot water channel 5, a cold water channel 8, a water jacket 2, and an exhaust heat absorption channel 4.
Although it may be provided in any of the above, it is preferable to measure the temperature of the hot water in the hot water channel 5 in order to maintain the temperature of the hot water supplied from the engine exhaust heat recovery heat exchanger 6 at a predetermined level.

[Brief explanation of the drawing]

Fig. 1 is a diagram of the principle of an engine exhaust heat recovery device showing an embodiment of the present invention, Fig. 2 is a diagram showing the relationship between the hot water temperature of the hot water channel and the diversion ratio to the heat radiation path, and Fig. 3 is a diagram of the variable diversion valve. A main part system diagram showing another embodiment, FIG. 4 is a diagram corresponding to FIG. 1 showing the prior art. 1...Radiator, 2...Water jacket, 3...
・Exhaust heat absorption heat exchanger, 4...Exhaust heat absorption path, 5.
・・Hot water channel, 6.・Heat exchanger for engine exhaust heat recovery,
7...6 heat recovery discharge side waterway, 8...cold waterway, 1
0... Heat radiation path, 12... Variable flow diversion valve, 13... Temperature sensor, 14... Diversion ratio control device, E... Engine, T1... Detection temperature, T1 (L)...・Heat radiation start temperature, TI(H)...All heat radiation temperature, A...Heat radiation control area. Patent applicant: Kubota Iron Works Co., Ltd. 4-J? Oshiiri -1)-
z ＊ Yami Min ＼Figure 2Figure 1

Claims (1)

[Claims] 1. The water jacket 2 of the engine E includes the exhaust heat absorption path 4 of the exhaust heat absorption heat exchanger 3, the hot water channel 5, and the heat recovery discharge side of the engine exhaust heat recovery heat exchanger 6. In an engine exhaust heat recovery device configured by serially connecting a water channel 7 and a cold water channel 8 in a serial circulation manner, the heat dissipation of the radiator 1 is carried out in the heat recovery discharge side water channel 7 of the heat exchanger 6 for engine exhaust heat recovery. The heat recovery discharge side waterway 7 and the heat radiation path 10 are connected in parallel to the engine cooling waterway 11 consisting of the cold waterway 8, the water jacket 2, the exhaust heat absorption path 4, and the hot waterway 5. , variable flow divider valve 12
A temperature sensor 13 is provided in the engine cooling water channel 11, and a variable diverter valve 12 is connected to the temperature sensor 13 via a diverter ratio controller 14.
The temperature sensor 13 detects the temperature of the engine cooling water passing through the engine cooling water channel 11, and the detected temperature T_1 of the cooling water temperature is set to the heat radiation start temperature T_1 ( L) and the set temperature T for total heat dissipation which is higher than this.
_1 (H), the higher the detected temperature of the cooling water, the more the diversion ratio control device 14 operates the variable diversion valve 12 to increase the amount of heat radiation, increasing the temperature of the engine. The heat radiation side division ratio of the cooling water from the cooling water channel 11 to the heat radiation path 10 is increased, and the heat recovery side division ratio of the cooling water to the heat recovery discharge side waterway 7 is decreased, so that the detected temperature of the cooling water is low. Indeed, the engine is characterized in that the division ratio control device 14 operates the variable division valve 12 to the heat radiation loss side to decrease the heat radiation side division ratio and increase the heat recovery side division ratio. Exhaust heat recovery device