EP2287454A1

EP2287454A1 - Cooling water circuit for stationary engine

Info

Publication number: EP2287454A1
Application number: EP09742678A
Authority: EP
Inventors: Hirotoshi Kihara; Shohei Amakawa; Toshiyuki Hayashi; Shojiro Matsumura
Original assignee: Yanmar Co Ltd
Current assignee: Yanmar Co Ltd
Priority date: 2008-05-07
Filing date: 2009-04-24
Publication date: 2011-02-23
Also published as: EA020099B1; JP2009270485A; US20110061833A1; AU2009245230A1; JP5191792B2; CN102016258A; EA201071276A1; WO2009136554A2; CN102016258B

Abstract

The present invention has a waste heat recovery device (37) that supplies engine waste heat by way of engine coolant; a radiator (18) that dissipates engine waste heat by way of engine coolant; an exhaust gas heat exchanger (33) that supplies engine waste heat from exhaust gas to engine coolant; and a coolant pump (32) that causes engine coolant to circulate. Furthermore, the constitution is such that pressure drop equipment (34) is arranged upstream with respect to a coolant pump suction region (32b); a restrictor is arranged in a communication passage (50) between a coolant pump suction region and a region (20) vented to atmosphere; a location upstream with respect to the pressure drop equipment is made to communicate with the region vented to atmosphere; and the region vented to atmosphere is made capable of being kept in communication with atmosphere.

Description

TECHNICAL FIELD

The present invention relates to a coolant circuit for a stationary engine having a waste heat recovery device such as might be employed in a GHP (gas heat pump) or a cogeneration system.

BACKGROUND ART

Disclosed conventionally as a coolant circuit for a stationary engine having a waste heat recovery device, in the context of an engine coolant circuit having a waste heat recovery device, is a constitution in which a coolant pump suction region communicates with a region vented to atmosphere (see, for example, Patent Reference No. 1).
That is, the engine coolant circuit described in Patent Reference No. 1 is equipped with a waste heat recovery device constituted such that a radiator is in contact with an outdoor heat exchanger. Moreover, the inlet region side of the coolant pump is connected to a reserve tank, and the coolant pump suction port communicates with atmosphere by way of a vent hole provided at the reserve tank.

PRIOR ART REFERENCES

PATENT REFERENCES

PATENT REFERENCE NO. 1: Japanese Patent Application Publication Kokai No. H09-88602 (1997 )

SUMMARY OF INVENTION

PROBLEM TO BE SOLVED BY INVENTION

With the constitution of the engine coolant circuit of the aforementioned Patent Reference No. 1, pressure at the coolant pump suction region will be more or less equal to head pressure at the reserve tank, and so long as the coolant pump is not arranged at a location higher than the reserve tank, it will not be possible to set the pressure at the pump suction region so as to be the same or less than the head pressure.
However, an engine coolant circuit having a waste heat recovery device is equipped with an exhaust gas heat exchanger for causing engine heat to be absorbed by engine coolant from exhaust gases prior to supply of engine waste heat by way of engine coolant at the waste heat recovery device. Because it heats engine coolant, there is a possibility that such an exhaust gas heat exchanger might be treated as a type of boiler. Where the exhaust gas heat exchanger is thus treated as a boiler, there will be a desire to keep the pressure of that engine coolant as low as possible.
The present application therefore addresses the problem of making it possible, in the context of an engine coolant circuit having a waste heat recovery device, to adjust pressure as required at a coolant pump suction region, which is where pressure in the circuit is lowest, so as to be any desired pressure that is the same or less than head pressure, for the purpose of setting pressure within the coolant circuit of an exhaust gas heat exchanger or the like so as to be a prescribed pressure.

MEANS FOR SOLVING PROBLEM

The present invention, being conceived in order to solve the aforesaid problem, is a stationary engine coolant circuit having a waste heat recovery device that supplies engine waste heat by way of engine coolant; a radiator that dissipates engine waste heat by way of engine coolant; an exhaust gas heat exchanger that supplies engine waste heat from exhaust gas to engine coolant; and a coolant pump that causes engine coolant to circulate, the constitution being such that a coolant pump suction region is made to communicate with a region vented to atmosphere; a location upstream with respect to the pressure drop equipment is made to communicate with the region vented to atmosphere; a restrictor is arranged in a communication passage between the region vented to atmosphere and the location upstream with respect to the pressure drop equipment; and the region vented to atmosphere is capable of being kept in communication with atmosphere.
In such present invention, the pressure drop from the pressure drop equipment makes it possible to cause pressure at the coolant pump suction region to be lower than head pressure. Furthermore, by adjusting flow rate at the restrictor in the passage communicating with the region vented to atmosphere, it is possible to adjust pressure so as to be any desired pressure within a range from a negative pressure below atmospheric pressure to the head pressure at the region vented to atmosphere. This being the case, it is possible to set pressure within the coolant circuit to be a prescribed pressure while maintaining engine coolant flow rate so as to be equal to (pump suction region pressure + pump discharge pressure + pressure drop to measurement location).
The exhaust gas heat exchanger in the aforesaid present invention is arranged at a location that is at a discharge side of the coolant pump and that is downstream with respect to the engine. In such present invention, it is possible to cause pressure at the inlet port of the exhaust gas heat exchanger to be (pump suction region pressure + pump discharge pressure + pressure drop across flow passages within engine), this being lower than (pump suction region pressure + pump discharge pressure) by an amount corresponding to (pressure drop across flow passages within engine).
In the aforesaid present invention, a motor-driven three-way valve having an adjustable opening is arranged at a region where a radiator downstream passage and a waste heat recovery device downstream passage meet. In such present invention, because a motor-driven three-way valve is arranged at a location in the engine coolant circuit at which coolant temperature is lowest, heat resistance of the motor-driven three-way valve is improved. Note that the motor-driven three-way valve corresponds to one example of the aforesaid pressure drop equipment.
In the aforesaid present invention, a thermostat is arranged at a discharge side of the coolant pump; the waste heat recovery device is arranged at a passage on a high-temperature side of said thermostat; and a radiator is arranged at a location downstream with respect to the waste heat recovery device. In such present invention, when engine coolant temperature is at or above the thermostat setpoint temperature, all coolant flow will be directed to the waste heat recovery device. This being the case, when calculating the amount of heat supplied from the engine coolant, as compared with a constitution in which there is control of divided flow with respect to the waste heat recovery device and the radiator, calculation is simplified to the extent that there is no need to take engine coolant flow ratio into account.
In the aforesaid present invention, the region vented to atmosphere is constituted such that a vent pipe is provided at an upper region of a coolant tank, the coolant pump suction region and at least one of either the exhaust gas heat exchanger or the radiator being made to communicate with a watersealed region of the coolant tank. In such present invention, because a location in the coolant circuit at which there is high probability of air pocket formation is vented to atmosphere by way of a watersealed region, it is possible to definitively carry out gas-liquid separation on bubbles so that only engine coolant is returned to the circuit.
In the aforesaid present invention, the constitution is such that two of the coolant tanks are provided; the vent pipe being provided at one of the tanks; and further, an air pocket region at one of the tanks being made to communicate with an air pocket region at the other tank; the coolant pump suction region and at least one of either the exhaust gas heat exchanger or the radiator being made to communicate with a watersealed region at the other tank; a watersealed region at one of the tanks being made to communicate with a watersealed region at the other tank; and a bottom of the tank provided with the vent pipe being arranged at the same height or elevation as a bottom of the other tank. In such present invention, because a constitution is adopted in which two tanks are provided, it is possible to divide these in terms of function such that one serves as reserve tank while the other serves to allow gas-liquid separation of high-temperature bubbles that rise up from within the circuit, permitting prevention of elevated reserve coolant temperature as a result of gas-liquid separation.

BENEFIT OF INVENTION

In the present invention, because the pressure drop from the pressure drop equipment and adjustment of the opening at the restrictor make it possible to adjust the pressure at the coolant pump suction region so as to be any desired pressure that is the same or less than head pressure, this can be set as required so as to be the same or lower than atmospheric pressure.

BRIEF DESCRIPTION OF DRAWINGS

[FIG. 1] FIG. 1 is a circuit diagram showing an engine coolant circuit in a cogeneration apparatus associated with one embodiment of the present invention.
[FIG. 2] FIG. 2 is a front perspective view showing the entirety of same cogeneration apparatus.
[FIG. 3] FIG. 3 is a rear perspective view showing the entirety of same cogeneration apparatus.
[FIG. 4] FIG. 4 is a schematic drawing of a coolant tank.

EMBODIMENTS FOR CARRYING OUT INVENTION

Below, embodiments of the present invention are described with reference to the drawings.
In the present embodiment, description is carried out in terms of a situation in which the present invention is applied to a cogeneration apparatus 1. Note that cogeneration apparatus 1 refers to a system, where a commercial electric power subsystem of an external commercial power supply and an electric power generation subsystem of an electric generator are connected to an electric power delivery subsystem that delivers electric power to electric power consuming equipment (load), that meets the electric power demand of said load, that recovers waste heat generated in accompaniment to electric power generation, and that utilizes said recovered heat.
FIG. 1 shows a circuit diagram of an engine coolant circuit in the cogeneration apparatus, FIG. 2 shows a front perspective view of same apparatus, and FIG. 3 shows a rear perspective view of same apparatus.
As shown in FIG. 2 and FIG. 3, cogeneration apparatus 1 associated with the present embodiment is equipped with shell 2 serving as enclosure. The interior of this shell 2 is divided vertically into two regions, the lower region comprising engine chamber 3 and equipment housing chamber 5, and the upper region comprising radiator chamber 7, intake chamber 8, and exhaust chamber 9.
Arranged within the aforesaid engine chamber 3 there are an engine 10, an electric generator 11 driven by this engine 10, and an oil tank 12 storing lubricating oil.
The aforesaid equipment housing chamber 5 is arranged to the side (right side as shown in FIG. 2) of engine chamber 3. Arranged within equipment housing chamber 5 there are an inverter 14 and a control box 17 equipped with a control apparatus 16 for controlling engine drive equipment and so forth.
The aforesaid radiator chamber 7 is arranged above equipment housing chamber 5, radiator 18 and coolant tank 20 being arranged within this radiator chamber 7. Heat-dissipating radiator fan 19, driving of which is controlled by the aforesaid control apparatus 16, is arranged above radiator chamber 7.
Respectively arranged at intake chamber 8 are air cleaner 22 and intake silencer 23. Arranged at exhaust chamber 9 is exhaust silencer 24.
Next, referring to FIG. 1, the engine coolant circuit will be described. This engine coolant circuit 30 is equipped with coolant pump 32, which is the drive source for causing circulation of engine coolant. Connected in order as one proceeds downstream from the discharge side (coolant pump discharge region 32a) of this coolant pump 32 there are coolant passages (water jacket) internal to engine 10, exhaust gas heat exchanger 33, and thermostat 35.
Engine 10 might be a stationary gas engine using municipal gas or the like as fuel, the exhaust system thereof being equipped with the aforesaid exhaust gas heat exchanger 33 and the aforementioned exhaust silencer 24. Furthermore, engine coolant passing through engine 10 is sent to exhaust gas heat exchanger 33, and after heat from exhaust gas is removed therefrom at exhaust gas heat exchanger 33, is made to flow into thermostat 35 by way of passage 31.
Thermostat 35 is equipped with passage 35a on the low-temperature side thereof and passage 35b on the high-temperature side thereof, the downstream end of low-temperature passage 35a being connected to the inlet side (coolant pump suction region 32b) of coolant pump 32. Furthermore, the downstream end of high-temperature passage 35b is connected to liquid-liquid heat exchanger 37 serving as waste heat recovery device.
Thermostat 35 is such that when temperature of engine coolant is below a prescribed temperature (e.g., when the engine is first started), engine coolant is made to flow to low-temperature passage 35a; and such that when engine coolant reaches a temperature that is at or above a prescribed temperature, engine coolant is made to flow to high-temperature passage 35b and liquid-liquid heat exchanger 37.
Liquid-liquid heat exchanger 37 supplies heat removed from engine coolant to the exterior, supplying heat to water flowing in the secondary-water side 38 of a hot water supply, for example. Respectively provided at locations upstream and downstream from liquid-liquid heat exchanger 37 are temperature sensors 43, 44 for detecting temperature of engine coolant.
Engine coolant that has passed through liquid-liquid heat exchanger 37 is made to flow to radiator 18 and motor-driven three-way valve 34. That is, motor-driven three-way valve 34 comprises a motor valve controlled by the aforesaid control apparatus 16, and has three ports, these being first coolant inlet 34a, second coolant inlet 34b, and coolant outlet 34c.
Furthermore, connected to first coolant inlet 34a is the downstream end of waste heat recovery device downstream passage 39, which extends from liquid-liquid heat exchanger 37. Moreover, connected to second coolant inlet 34b is the downstream end of radiator downstream passage 40, which extends from radiator 18. Accordingly, motor-driven three-way valve 34 is arranged at a region where waste heat recovery device downstream passage 39 and radiator downstream passage 40 meet. Note that waste heat recovery device downstream passage 39 is connected by way of passage 42 to radiator 18.
Furthermore, coolant outlet 34c is connected by way of coolant supply pipe 41 to the aforesaid low-temperature passage 35a.
Motor-driven three-way valve 34 is such that the ratio between the degree to which first coolant inlet 34a and second coolant inlet 34b are opened is capable of being changed (adjustment of opening), the opening ratio being determined in correspondence to the amount of heat exchange occurring at liquid-liquid heat exchanger 37. Specifically, when the amount of heat exchange occurring at liquid-liquid heat exchanger 37 is large, i.e., when the amount of heat being dissipated by engine coolant is large, the degree to which first coolant inlet 34a is opened will be large; and when the amount of heat exchange occurring at liquid-liquid heat exchanger 37 is small, i.e., when the amount of heat being dissipated by engine coolant is small, the degree to which second coolant inlet 34b is opened will be large.
The aforesaid coolant tank 20 comprises two tanks, one tank (reserve tank) 20a being made of synthetic resin, and the other tank (gas-liquid separation tank) 20b being made of metal. Connected to the one tank 20a is a vent pipe 48 that is capable of being kept in communication with atmosphere. The bottom of the coolant at the one tank that is provided with vent pipe 48 is arranged at the same height or elevation as the bottom of the other tank, and moreover, respective air pocket regions at the one tank 20a and the other tank 20b are made to communicate by means of communication pipe 46. Furthermore, watersealed regions of the two tanks 20a, 20b (the portions thereof at which engine coolant is stored) are made to communicate by way of communication pipe 47 which extends to the respective lower portions of the tanks.
The lower portion of the other tank 20b is connected by way of communication pipe 45 to the upper portion 18a of radiator 18. Furthermore, communication pipe 49 is connected between the lower portion of the other tank 20b and plumbing (not shown), through which engine coolant flows, within exhaust gas heat exchanger 33. Radiator 18 and exhaust gas heat exchanger 33 are arranged at elevation(s) higher than engine 10, the reason being that they are locations within the coolant circuit that are susceptible to formation of air pockets. By thus providing an air purge circuit leading to a gas-liquid separation tank at location(s) where there is danger of air pocket formation, this allows gas-liquid separation to be carried out so that only engine coolant is returned for intake by coolant pump 32.
Moreover, restrictors 60 and 61 are provided so as to prevent excessive flow of engine coolant to communication pipes 45 and 49 and so as to adjust pressure at the inlet side of coolant pump 32 to any desired pressure that is the same or less than head pressure.
However, if it should become necessary to drastically reduce pressure at coolant pump suction region 32b, the diameters of restrictors 61, 60 may be increased, or the restrictors might be removed from communication pipes 45, 49 and a restrictor 51 might be provided at communication passage 50, so as to allow pressure within the circuit to be adjusted to a lower value.
Cogeneration apparatus 1 of the present embodiment having the foregoing constitution, operation with respect to circulation in the coolant circuit will next be described.
Upon causing coolant pump 32 to operate, engine coolant discharged from coolant pump 32 is supplied to engine 10, its temperature becoming elevated as it cools cylinders and various other locations while passing through the interior of engine 10, and it moreover passes through exhaust gas heat exchanger 33 to arrive at thermostat 35. At thermostat 35, when coolant temperature is below a prescribed temperature, engine coolant is returned to coolant pump 32.
Furthermore, when engine coolant reaches a temperature that is at or above a prescribed temperature, thermostat 35 causes engine coolant to flow to liquid-liquid heat exchanger 37. Here, in the event that there is desire for supply of hot water, at liquid-liquid heat exchanger 37, heat from engine coolant is extracted to the exterior as it is used to heat water flowing in the secondary-water side 38 of a hot water supply. Furthermore, the amount of engine coolant flowing to radiator 18 is adjusted in correspondence to the amount of heat exchange occurring at liquid-liquid heat exchanger 37. When the amount of heat exchange is large, the degree to which first coolant inlet 34a of motor-driven three-way valve 34 is opened is greater than the degree to which second coolant inlet 34b thereof is opened, and the amount of coolant flowing through waste heat recovery device downstream passage 39 and bypassing radiator 18 is large.
When the amount of heat exchange is small, the degree to which second coolant inlet 34b of motor-driven three-way valve 34 is opened is greater than the degree to which second coolant inlet 34a thereof is opened, and the amount of coolant flowing to radiator 18 is large.
Furthermore, the passage which goes from coolant pump suction region 32b, through communication passage 50 and coolant tank 20, to vent pipe 48 constitutes a line vented to atmosphere; and because both the communication pipe 49 from exhaust gas heat exchanger 33 and the communication pipe 45 from radiator 18, at which the pressure within the coolant circuit is higher than at coolant pump suction region 32b, go through restrictors 61, 60 before meeting at coolant tank 20, it is possible to cause the pressure at coolant pump suction region 32b to be the same or less than head pressure.
Furthermore, by providing exhaust gas heat exchanger 33 downstream with respect to engine 10, this makes it possible to reduce the pressure drop by an amount corresponding to the contribution from engine 10 and thus reduce the pressure acting at exhaust gas heat exchanger 33.
By providing motor-driven three-way valve 34 at the suction location of the pump, which is the location within the coolant circuit where temperature is lowest, reliability with respect to the part(s) employed for motor-driven three-way valve 34 is improved. Moreover, with improved reliability it becomes possible to use motor-driven three-way valve 34 over a long period and achieve cost reduction.
When engine coolant temperature increases and the state of thermostat 35 becomes such that the high-temperature side thereof is opened, because all flow constantly goes through liquid-liquid heat exchanger 37, it will be possible to calculate the amount of heat exchange occurring at liquid-liquid heat exchanger 37 by detecting the change in water temperature at temperature sensor 43 at the inlet side of liquid-liquid heat exchanger 37 versus temperature sensor 44 at the outlet side thereof. This being the case, as compared with the situation in which radiator 18 and liquid-liquid heat exchanger 37 are arranged in paralleled fashion, because computation of the amount of heat exchange no longer requires a flowmeter at the passage leading to liquid-liquid heat exchanger 37, cost reduction is made possible. Alternatively, as compared with use of the ratio of opening relative to liquid-liquid heat exchanger 37 at motor-driven three-way valve 34 to calculate flow rate to liquid-liquid heat exchanger 37, computational load is reduced.
Also, an air purge circuit leading to a gas-liquid separation tank is provided at location(s) where there is danger of air pocket formation, such as at exhaust gas heat exchanger 33 and radiator 18. This being the case, bubbles mixed with engine coolant at exhaust gas heat exchanger 33 and radiator 18 are, as shown at FIG. 4, made to pass through communication pipe 49 and communication pipe 45, to flow into the other tank 20b. Moreover, only air passes through communication pipe 46 and enters the one tank 20a, the air traveling through vent pipe 48 to be discharged to atmosphere. Thus, because the constitution is such that gas-liquid separation is carried out, with only engine coolant being returned to the circuit interior, it is possible to reduce the size of radiator 18, and it is also possible to prevent cavitation at coolant pump 32. Note that engine coolant within the one tank 20a moves as appropriate to the interior of the other tank 20b by way of communication pipe 47.
By carrying out gas-liquid separation of high-temperature bubbles at the other tank (gas-liquid separation tank) 20b, which is different from the one tank (reserve tank) 20a, it is possible to prevent increase in water temperature at the reserve tank. In addition, because increase in water temperature is prevented thereat, the reserve tank may be manufactured easily and cheaply from synthetic resin.
The present invention is not limited to the foregoing embodiment. For example, as indicated by the imaginary line at FIG. 1, it is possible for the bottom of the coolant at the one tank that is provided with vent pipe 48 to be arranged so as to be at higher elevation than the bottom of the other tank. In such case, it will be possible to more easily cause engine coolant within the one tank 20a to move to the interior of the other tank 20b by way of communication pipe 47.
Furthermore, it is also possible to employ the present invention in an engine-driven heat pump. The present invention may be embodied in a wide variety of forms other than those presented herein without departing from the spirit or essential characteristics thereof. The foregoing embodiments and working examples, therefore, are in all respects merely illustrative and are not to be construed in limiting fashion. The scope of the present invention being as indicated by the claims, it is not to be constrained in any way whatsoever by the body of the specification. All modifications and changes within the range of equivalents of the claims are, moreover, within the scope of the present invention.
Moreover, this application claims priority based on Patent Application No. 2008-121521 filed in Japan on 7 May 2008. The content thereof is hereby incorporated in the present application by reference.

POTENTIAL INDUSTRIAL USE

The stationary engine coolant circuit associated with the present invention is effective as a coolant circuit for a stationary engine having a waste heat recovery device, and is particularly suited to use in a GHP (gas heat pump) or a cogeneration system.

EXPLANATION OF REFERENCE NUMERALS

1: Cogeneration apparatus
2: Shell
10: Engine
18: Radiator
20: Coolant tank
20a: The one tank
20b: The other tank
30: Engine coolant circuit
32: Coolant pump
32a: Coolant pump discharge region
32b: Coolant pump suction region
33: Exhaust gas heat exchanger
34: Motor-driven three-way valve
35: Thermostat
37: Liquid-liquid heat exchanger (waste heat recovery device)
39: Waste heat recovery device downstream passage
40: Radiator downstream passage
41: Coolant supply pipe
42: Passage
43: Temperature sensor
44: Temperature sensor
45: Communication pipe
46: Communication pipe
47: Communication pipe
48: Vent pipe
49: Communication pipe
50: Communication passage
51: Restrictor
60: Restrictor
61: Restrictor

Claims

A stationary engine coolant circuit having a waste heat recovery device that supplies engine waste heat by way of engine coolant; a radiator that dissipates engine waste heat by way of engine coolant; an exhaust gas heat exchanger that supplies engine waste heat from exhaust gas to engine coolant; and a coolant pump that causes engine coolant to circulate,
the stationary engine coolant circuit being characterized in that it is constituted such that pressure drop equipment is arranged upstream with respect to a coolant pump suction region; the coolant pump suction region is made to communicate with a region vented to atmosphere; a location upstream with respect to the pressure drop equipment is made to communicate with the region vented to atmosphere; a restrictor is arranged in a communication passage between the region vented to atmosphere and the location upstream with respect to the pressure drop equipment; and the region vented to atmosphere is capable of being kept in communication with atmosphere.
A stationary engine cooling circuit according to claim 1, the stationary engine coolant circuit being characterized in that the exhaust gas heat exchanger is arranged at a location that is at a discharge side of the coolant pump and that is downstream with respect to the engine.
A stationary engine coolant circuit according to claim 1, the stationary engine coolant circuit being characterized in that a motor-driven three-way valve having an adjustable opening is arranged at a region where a radiator downstream passage and a waste heat recovery device downstream passage meet.
A stationary engine coolant circuit according to claim 1, the stationary engine coolant circuit being characterized in that a thermostat is arranged at a discharge side of the coolant pump; the waste heat recovery device is arranged at a passage on a high-temperature side of said thermostat; and a radiator is arranged at a location downstream with respect to the waste heat recovery device.
A stationary engine coolant circuit according to claim 1, the stationary engine coolant circuit having a waste heat recovery device and characterized in that the region vented to atmosphere is constituted such that a vent pipe is provided at an upper region of a coolant tank, the coolant pump suction region and at least one of either the exhaust gas heat exchanger or the radiator being made to communicate with a watersealed region of the coolant tank.
A stationary engine coolant circuit according to claim 5, the stationary engine coolant circuit having a waste heat recovery device and characterized in that it is constituted such that two of the coolant tanks are provided; a vent pipe being provided at one of the tanks; and further, an air pocket region at one of the tanks being made to communicate with an air pocket region at the other tank; the coolant pump suction region and at least one of either the exhaust gas heat exchanger or the radiator being made to communicate with a watersealed region at the other tank; a watersealed region at one of the tanks being made to communicate with a watersealed region at the other tank; and a bottom of the tank provided with the vent pipe being arranged at the same height or elevation as a bottom of the other tank.