JPH02104953A - Device for recovering exhaust heat of engine - Google Patents

Abstract

PURPOSE:To prevent the thermal breakage of an exhaust-heat absorbing heat exchanger 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 heat recovering liquid temperature gets higher and increasing the flow-dividing rate on the heat radiating side of cooling water. CONSTITUTION:If the heat recovering quantity by a heat recovering device is reduced by an external factor reducing the heat radiating quantity of an engine exhaust heat from a heat exchanger 6 or when the load of an engine E is increased increasing the engine exhaust heat itself, the temperature of cooling water passing through the discharge-side water passage 7 side of the engine exhaust-heat recovering heat exchanger 6 is increased, also increasing the temperature of a heat recovering liquid of a heat-recovering heat absorbing side liquid passage 15 for changing heat therewith. This is detected by a temperature sensor 30 and a variable flow-dividing valve 12 is operated to a heat radiating rate increasing side by a signal from a flow-dividing rate control device 14, to make cooling water dividingly flow in a larger quantity on the heat radiating passage 10 side whereas in a smaller quantity on the heat-recovering discharge-side water passage 7 side thereby, increasing the heat radiating rate of the exhaust heat of the engine E to restrain the increase in temperature of the heat recovering liquid. Thus, the thermal breakage of the exhaust-heat absorbing heat exchanger can be prevented.

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, and the present invention relates to a device for recovering exhaust heat from an engine such as engine body heat and exhaust heat. To provide a device that can maintain the temperature of liquid taken out from a liquid within a certain 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. The exhaust heat absorption path 4, the hot water path 5, the heat recovery discharge side water path 7 of the engine exhaust heat recovery heat exchanger 6, and the cold water path 8 are connected 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 liquid path 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 sharply increases and the engine E overheats, and a sudden thermal stress is applied to the exhaust heat absorption heat exchanger 3. , there is a risk that the heat exchanger 3 will be thermally damaged.

In addition, even if the amount of heat recovery is constant, if the load on the engine generator increases, even though the heat emitted from engine E increases, the heat radiation rate does not increase commensurately, so the sudden increase in cooling water temperature will cause There is a risk that the heat exchanger 3 for absorbing exhaust heat may be thermally damaged.

Moreover, as described above, when the amount of heat recovered from the heat exchanger 6 decreases or the load on the engine E increases, the heat exchanger 6
When the temperature of the hot water discharged from the heat recovery endothermic liquid path 15 increases rapidly, and conversely, when the amount of heat recovered from the heat exchanger 6 increases or the load on the engine E decreases, the heat of the heat exchanger 6 increases. There is a problem in that the temperature of hot water discharged from the heat-absorbing liquid path 15 for recovery rapidly decreases, and the temperature of hot water rapidly changes and is not constant due to fluctuations in the heat recovery load of the heat exchanger 6 and the load of the engine E.

The present invention maintains the temperature of the heat recovery liquid exiting from the heat absorption side liquid path of the heat exchanger for engine exhaust heat recovery within a constant temperature range even when the heat recovery load of the heat exchanger or the engine load changes, and The technical challenge is to prevent thermal damage to heat exchangers for heat absorption.

<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 3 is connected to the outlet side of the endothermic liquid path 15 for heat recovery of the heat exchanger 6 for engine exhaust heat recovery.
0 is provided, and the variable flow dividing valve 12 is connected to the temperature sensor 30 via the flow dividing ratio control device 14 so as to be able to control the flow dividing ratio. The detected temperature T of the heat recovery liquid temperature is between the hot water temperature set for starting heat radiation Tt (L) and the higher temperature set temperature T2 (H) for total heat radiation. When the temperature is within the heat radiation control temperature range A, the higher the detected temperature of the heat recovery liquid temperature is, the more the division ratio control device 14 operates the variable flow division valve 12 to increase the heat radiation amount.
The heat radiation side distribution rate of cooling water from the engine cooling waterway 11 to the heat radiation path IO is increased, and the heat recovery discharge side waterway 7
The division ratio of the cooling water to the heat recovery side is decreased, and the lower the detected temperature of the heat recovery liquid is, the division ratio control device 14 operates the variable division valve 12 to the heat radiation loss side,
The present invention is characterized in that the heat radiation side division ratio is decreased and the heat recovery side division ratio is increased.

<Function> When the heat recovery liquid temperature T of the heat recovery endothermic side liquid path 15 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; , when the amount of heat dissipated from the engine exhaust heat from the heat exchanger 6 decreases, or when the load on the engine E increases and the engine exhaust heat itself increases, the discharge side water channel 7 of the heat exchanger 6 for recovering engine exhaust heat As the temperature of the cooling water passing through the cooling water increases, the temperature T of the heat recovery liquid in the heat recovery endothermic side liquid path 15 that exchanges heat with it also tends to rise, but the temperature sensor 30 detects this heat recovery liquid temperature T. detect a rise,
The variable diverter valve 12 operates to increase the heat radiation rate in response to a signal from the diverter ratio control device 14, so that more cooling water is diverted to the heat radiation path 10 side, and less cooling water is diverted to the heat recovery discharge water channel 7 side. hand,
Since the heat dissipation rate of the exhaust heat of the engine E is increased, the temperature of the cooling water passing through the heat recovery discharge side water channel 7 of the engine exhaust heat recovery heat exchanger 6 decreases, and the heat recovery endothermic side fluid channel that exchanges heat with the heat recovery discharge side water channel 7 decreases. The increase in the temperature Tt of the heat recovery liquid No. 15 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 temperature of the cooling water passing through the discharge side waterway 7 side of the engine exhaust heat recovery heat exchanger 6 decreases, and the heat recovery liquid in the heat recovery endothermic side liquidway 15 that exchanges heat with it decreases. The temperature T also tries to decrease, but the temperature sensor 30 detects this decrease in the heat recovery liquid temperature T,
The variable distribution valve 12 operates to lower the heat radiation rate in response to a signal from the distribution ratio control device 14, and diverts less cooling water to the heat radiation path 10 side and more to the heat recovery discharge waterway 7 side. ,
Since the heat dissipation rate of the exhaust heat of the engine E is lowered, the temperature of the cooling water passing through the heat recovery discharge side water channel 7 of the engine exhaust heat recovery heat exchanger 6 increases, and the heat recovery endothermic side liquid channel that exchanges heat with this increases. 15 Temperature T of heat recovery liquid! The decline in is suppressed.

In addition, as described above, the engine exhaust heat recovery heat exchanger 6
Even if the amount of heat recovered from the heat exchanger 6 or the load on the engine E changes, the temperature of the cooling water passing through the heat recovery discharge side water channel 7 of the heat exchanger 6 will fluctuate less, and the heat recovery that recovers heat from this cooling water will reduce the fluctuation range. The temperature change of the heat recovery liquid in the endothermic side liquid path 15 can also be reduced.

<Effects of the invention> (1) Even if the amount of heat recovered from the engine exhaust heat recovery heat exchanger or the engine load changes, the cooling water temperature of the heat recovery discharge side waterway of the heat exchanger remains within a constant temperature range. Therefore, the temperature change of the heat recovery liquid in the heat recovery endothermic side liquid path that recovers heat from the cooling water can be suppressed to a small level.

(2) 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. The diversion function prevents the temperature of the cooling water in the cooling waterway from rising rapidly, thereby eliminating heat damage to the heat exchanger for absorbing exhaust heat.

<Example> Embodiments of the present invention will be described below 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 a generator G are interlocked in the front-rear direction to generate electricity and at the same time recover engine exhaust heat including engine body heat and exhaust heat.

A jacket 2 is formed in the cylinder protrusion and cylinder head of the gas engine E, and the engine E
A heat exchanger 3 for absorbing exhaust heat and a muffler 20 are installed in the exhaust passage 21 of
Install them in 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.

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

A heat exchanger 3 for absorbing exhaust heat is attached to the water jacket 2.
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 lO passing through the radiator I 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.
Switch to the side of
It is configured to short-circuit from the cold water channel 8 to the cold water channel 8, thereby minimizing the amount of heat dissipated and allowing early warm-up.

On the other hand, 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 the heat exchanger for engine exhaust heat recovery is installed. A temperature sensor 30 is attached to the outlet side of the endothermic side water channel 15 of No. 6, and the temperature sensor 30 is linked to the variable flow dividing valve 12 via the flow dividing ratio control device 14 so as to be able to control the flow dividing ratio. It is configured to maintain the temperature of the hot water flowing out within a certain range.

That is, the temperature range A for heat radiation control is applied to the division ratio control device 14.
is set, and the lower limit of this region A is the heat radiation start temperature T 2 (L
), and its upper limit is the temperature T2 at which the heat dissipation rate becomes 100%.
(H), the temperature sensor 30 for this temperature range A
The variable flow divider valve 12 is controlled as shown in (1) to (3) below according to the level of the detected temperature T of the hot water supply water. It is configured to change the rate of division of the recovery discharge side waterway 7 into the two flow paths to change the ratio of heat radiation and heat recovery.

However, as a matter of course, T2(L)<T,(H), and in reality, the temperature of the hot water supplied from the heat recovery endothermic side waterway 15 is 8.
It is best to keep it around 0°C, so take ±3°C around this temperature, set 'rt(L) to 77°C, and set T2(H) to 77°C.
are each set at 83°C.

Further, the variable diverter valve 12 is not limited to the three-way valve as in the embodiment, but as shown in FIG. Two-way metering valves 12a may be provided, and these may be configured to cooperate with one flow rate control device 14.

(1) When the detected temperature T is less than the heat radiation start temperature Tt (L) (
In other words, when the hot water temperature drops abnormally), as shown in FIG. The engine cooling water, which has absorbed engine body heat through the water jacket 2 and absorbed exhaust heat through the exhaust heat absorption path 4, is controlled to have a diversion rate of 100%. All of the engine exhaust heat that flows into the heat release side water channel 7 of the heat exchanger 6 via the diversion valve 12 and is stored in the cooling water is effectively recovered by the heat recovery release side water channel 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.

However, in this control, in order to avoid hunting, the heat radiation side diversion rate is maintained at 0% until the hot water temperature rises to a temperature considerably higher than the heat radiation start temperature T*(L).

(2) Heat radiation start temperature T! In the case of (L)≦detected temperature T,≦all discharge temperature T, (H) (that is, when the hot water temperature is in the normal temperature range), as shown in FIG. 12 is controlled as follows.

(2) As the detected temperature T becomes higher, the heat radiation side diversion rate to the heat radiation path 10 is increased, and the heat recovery side diversion rate to the heat recovery discharge side waterway 15 is decreased.

(2) As the detected temperature T 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 15 is increased.

Therefore, as the detected temperature T becomes higher, the proportion of cooling water diverted from the hot water channel 5 to the heat radiation path 10 increases, the heat radiation efficiency of the cooling water increases, 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, the lower the detected temperature T, the warm water channel 5→
The proportion of cooling water diverted to the heat recovery discharge side waterway 7 increases,
The heat dissipation efficiency of the cooling water becomes low, and the temperature of the hot water in the hot water channel 5 quickly rises.

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) When the total discharge temperature "r*(H)<detected temperature T" (that is, when the hot water temperature rises abnormally) As shown in FIG. is controlled so that the diversion rate to the heat radiation path 10 is 100% and the diversion rate to the heat recovery discharge side waterway 7 is 0%, and the cooling water flowing out from the engine E is transferred from the hot waterway 5 to the variable diversion valve. 12, all flows into the heat radiation path 10, and the engine exhaust heat stored in the cooling water is radiated outside the system, lowering the cooling water temperature in the heat recovery discharge side waterway 7, and reducing the heat recovery endothermic side waterway 15. Decrease the temperature of flowing hot water.

As mentioned above, in this control as well, in order to avoid notching, the heat dissipation side flow rate is kept at 10 until the temperature of the hot water all drops to a temperature well below the heat dissipation temperature T2 (H).
Continue at 0%.

On the other hand, a temperature sensor 13 is attached to the hot water channel 5, and the temperature sensor 13 is linked to the variable flow dividing valve 12 via the flow dividing ratio control device 14, so that overheating of the engine E is prevented. .

That is, the upper limit temperature T Depending on the situation, the following controls (a) to (b) are performed.

(a) Detected temperature T, < upper limit temperature T, in the case of (H) (that is, when the engine heated waste water is in the normal temperature range) the detected temperature T of hot water from the temperature sensor 30.

Based on the information, the flow division ratio control of the variable flow division valve 12 is performed by the flow division ratio control device 14 as described in (1) to (3) above.

(b) When upper limit temperature TI(H)≦detected temperature T (i.e., when engine heated waste water rises abnormally) temperature sensor 13
The information from the temperature sensor 30 takes priority over the information from the temperature sensor 30, and the division ratio of cooling water flowing into the heat radiation path 10 is set to 100%, and the division ratio to the heat recovery discharge side water channel 7 of the heat exchanger 6 is set to 0.
%, all of the hot water flowing through the hot water channel 5 flows to the heat radiation 11 side, maximizing the heat radiation rate to the outside of the cooling water circulation system, and early starting the engine E. This prevents the engine E from overheating by cooling the heated waste water from the engine.

Note that the hunting prevention measures described above are also taken in this control.

However, the temperature sensor 13 may be provided in any of the cooling channels 11 consisting of the hot water channel 5, the cold water channel 8, and the engine jacket 2 and the exhaust heat absorption channel 4.
In order to quickly prevent overheating, it is preferable to measure the temperature of the hot water in the hot water channel 5.

As described above, in the present invention, a temperature sensor is attached to the endothermic waterway for heat recovery of a heat exchanger for recovering engine exhaust heat, and by the action of a variable flow divider valve linked to the temperature sensor via a control device, The engine E is characterized by distributing the cooling water that has absorbed engine exhaust heat to the heat radiation path of the radiator and the heat recovery water path of the heat exchanger at a predetermined distribution ratio, so that the engine E is limited to an engine generator, an engine compressor, Other engine work equipment such as an engine welder, or the engine alone may be used.

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

The heat recovery liquid flowing through the heat absorption side waterway of the engine exhaust heat recovery heat exchanger is not limited to water as in the above embodiments, but may also be oil or the like.

[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 temperature of the heat recovery liquid and the diversion rate 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. l...Radiator, 2...Thin 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 divider valve, 14... Diversion ratio control device, 15... Heat absorption side liquid path for heat recovery of 6, 3
0...Temperature sensor, E...Engine, T,...1
Detected temperature %T1 (L) at 5: Heat radiation start temperature, T,
(H)...All heat radiation temperature, A...Heat radiation control area. Patent applicant Kubota Iron Works Co., Ltd. Figure 2 Figure 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 30 is provided on the outlet side of the heat recovery endothermic liquid path 15 of the engine exhaust heat recovery heat exchanger 6, and the temperature sensor 30
The variable flow dividing valve 12 is connected to the variable flow dividing valve 12 via the flow dividing ratio control device 14 so as to be able to control the flow dividing rate, and the temperature sensor 30 detects the liquid temperature of the heat recovery liquid that has passed through the heat recovery endothermic side liquid path 15. The detected temperature T_2 of the heat recovery liquid temperature is within the heat radiation control temperature range A between the heat radiation start set temperature T_2 (L) and the higher temperature total heat radiation set temperature T_2 (H). In this case, the higher the detected temperature of the heat recovery liquid is, the more the diversion rate control device 14 operates the variable diversion valve 12 to the heat radiation increasing side,
The heat radiation side distribution rate of cooling water from the engine cooling waterway 11 to the heat radiation path 10 is increased, and the heat recovery discharge side waterway 7
The division ratio of the cooling water to the heat recovery side is decreased, and the lower the detected temperature of the heat recovery liquid is, the division ratio control device 14 operates the variable division valve 12 to the heat radiation loss side,
An exhaust heat recovery device for an engine, characterized in that the engine exhaust heat recovery device is configured to reduce the heat radiation side division ratio and increase the heat recovery side division ratio.