JP2008185001A - Waste heat recovering device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste heat recovering device reducing negative pressure in a system caused by condensation of steam when an engine provided with Rankine cycle is stopped and cooled, and avoiding breakage of piping and the like. <P>SOLUTION: The waste heat recovering device 1 is provided with a reservoir tank 16 connected to a condenser 9. The condenser 9 and the reservoir tank 16 are connected by a first passage 17 and a second passage 18 connecting both lower end parts. A first check valve 20 limiting cooling water flowing into the condenser 9 from the reservoir tank 16 is installed on the first passage 17. A second check valve 21 limiting cooling water flowing into the reservoir tank 16 from the condenser 9 is installed on the second passage 18. When pressure in the condenser 9 gets lower than valve opening pressure of the second check valve 21, the second check valve 21 opens and liquid cooling water in the reservoir tank 16 flows into the condenser 9. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a waste heat recovery apparatus that recovers waste heat in an engine via steam.

  2. Description of the Related Art Conventionally, there is known a waste heat recovery device that recovers waste heat generated by driving an internal combustion engine (engine) using a Rankine cycle. Such a waste heat recovery apparatus, for example, vaporizes a cooling medium such as cooling water in the water jacket of the engine and further recovers the waste heat via an expander driven by steam superheated by exhaust heat. It has become. The vapor after driving the expander is returned to a liquid state by the condenser. For example, Patent Document 1 discloses an improved version of such a waste heat recovery apparatus.

JP 2000-345835 A

  The waste heat recovery apparatus as described above is in an operable state in which a Rankine cycle is established when steam generated after engine warm-up fills part of the superheater, expander, or condenser with steam. However, such a waste heat recovery apparatus may cause the following problems after the engine is stopped. That is, when the engine is stopped and the inside is cooled, steam condenses inside the system, and the inside of the system becomes negative pressure. When the pressure in the system becomes negative, the piping forming the Rankine cycle is compressed by the external air pressure, and if this is repeated, cracking of the piping will occur.

  In addition, the mechanical seal of the water pump ensures the sealing function by sliding the seal part when the engine is running, but the sealing function is lowered because the seal part also stops sliding when the engine is stopped. There is a risk of being sucked into the system. Furthermore, there is a risk that external air may enter the system from the joints of the piping. The air that has entered the system in this way is accumulated in the condenser together with the steam when the engine is running, but the air that does not condense stays in the condenser. Once a large amount of air enters the system, the condenser is filled with air, and the heat dissipation performance of the condenser decreases. Due to this, the steam generated in the engine is not condensed in the condenser, the engine internal pressure rises, and there is a risk that problems such as overheating of the engine and rupture of the pipe coupling portion may occur.

  Accordingly, the present invention provides a waste heat recovery apparatus that can reduce the negative pressure in the system caused by condensation of steam when the engine equipped with the Rankine cycle is stopped and cooled, and can avoid damage to piping and the like. It is an issue to provide.

  In order to achieve such a problem, the waste heat recovery apparatus of the present invention includes a steam flow path through which a cooling medium vaporized by waste heat in an engine flows, a liquid flow path through which a liquid cooling medium flows, and the steam An energy recovery device that recovers energy from the vapor in the flow path, and a liquid amount adjustment device that adjusts the amount of liquid in the liquid flow path according to the vapor pressure in the vapor flow path. (Claim 1). When the pressure in the steam flow path decreases, the amount of liquid in the liquid flow path communicating with the vapor flow path is increased, the volume of the vapor flow path is reduced, and the pressure in the system is maintained. By maintaining the pressure in the system, it is possible to suppress deformation or the like of the pipe against the external pressure.

  In such a waste heat recovery apparatus, a condenser for returning the vapor to a liquid is provided, and the liquid amount adjusting apparatus includes a reserve tank connected to the condenser, according to the vapor pressure in the condenser. The liquid amount can be adjusted between the condenser and the reserve tank (claim 2). Generally, a waste heat recovery apparatus includes a condenser that returns steam after passing through an expander such as a turbine included in the energy recovery apparatus. Inside such a condenser, the ratio of vapor to liquid cooling medium is changing. If the liquid cooling medium is supplied from a reserve tank separately prepared for such a condenser, the proportion of the liquid cooling medium increases. Thus, if the ratio of the liquid cooling medium increases, the generation of negative pressure in the system due to the condensation of vapor can be mitigated. As a result, the pressure in the system can be maintained, and deformation of piping can be suppressed against the external atmospheric pressure.

  Such a waste heat recovery apparatus includes a condenser for returning the vapor to a liquid, and the liquid amount adjustment apparatus includes a reserve tank connected to the condenser, and a cooling medium from the reserve tank to the condenser A first check valve that restricts the inflow of the refrigerant, and a second check valve that restricts the inflow of the cooling medium from the condenser to the reserve tank, and the condenser and the The liquid amount can be adjusted with the reserve tank (claim 3). The first check valve in such a configuration is opened when the vapor pressure in the condenser becomes higher than a set value, and returns the liquid cooling medium in the condenser to the reserve tank. On the other hand, the second check valve is opened when the vapor pressure in the condenser becomes lower than the set pressure, and the liquid cooling medium in the reserve tank flows into the condenser. As a result, the amount of liquid in the system is adjusted, and consequently the vapor pressure in the system is adjusted. Such a 1st check valve and a 2nd check valve can be set as the structure arrange | positioned on the path | route which connects the lower end part of the said condenser, and the lower end part of the said reserve tank, respectively.

  Further, the liquid amount adjusting device in the waste heat recovery apparatus of the present invention may be configured to be a reserve tank that is connected to the liquid circulation path and is filled with a gas and a liquid cooling medium. Item 4). The liquid flow path and the vapor flow path are not separated. For this reason, when the vapor pressure in the vapor circulation path is lowered, the liquid cooling medium in the reserve tank flows into the liquid circulation path, the ratio of the vapor circulation path is lowered, and the pressure in the vapor circulation path is maintained. On the other hand, when the vapor pressure in the vapor circulation path increases, the cooling medium in the liquid circulation path is returned to the reserve tank, and the vapor pressure in the vapor circulation path is adjusted. Thereby, the damage of piping etc. resulting from the system becoming a negative pressure can be suppressed.

  Such a waste heat recovery apparatus may include a condenser that returns the vapor to a liquid, and the condenser may include a third check valve that releases internal air. The valve opening pressure of the third check valve is larger than the valve opening pressure of the first check valve. The third check valve acts as an air vent or a gas vent when the pressure rises due to the accumulation of gas such as air in the system due to some abnormality. Such a third check valve is installed on the path connecting the upper part of the condenser and the upper part of the reserve tank, that is, the path connecting the respective space portions, and the released air is released into the reserve tank. It can be constituted as follows. At this time, by making the valve opening pressure of the third check valve larger than the valve opening pressure of the first check valve, the steam is released when the cooling medium is returned from the condenser to the reserve tank through the first check valve. Can be avoided.

  By incorporating these waste heat recovery devices into the engine, the engine of the present invention can be obtained (claim 7).

  According to the present invention, when the engine is stopped and cooled, the vapor in the system is condensed and a negative pressure is generated in the system, thereby supplying the liquid cooling medium into the system and suppressing the pressure drop in the system. As a result, damage to the piping forming the Rankine cycle can be avoided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  Embodiments of the present invention will be described with reference to the drawings. 1 and 2 are explanatory diagrams showing a schematic configuration of the waste heat recovery apparatus 1 of the present embodiment. FIG. 1 shows a state where the engine is operating and the vapor pressure in the system has increased, and FIG. 2 shows a state where the engine has been stopped and cooled.

  The waste heat recovery apparatus 1 is incorporated in an engine body 2 that is a combustion engine. The waste heat recovery apparatus 1 includes a water jacket 3 formed from the cylinder block 2a to the cylinder head 2b, and a cooling water injection nozzle 4 installed in the cylinder head 2b. Cooling water as a cooling medium is supplied into the water jacket 3. Cooling water pumped from the lower portion of the water jacket 3 by the first water pump 5 is supplied to the cooling water injection nozzle 4. The injected cooling water is vaporized when the high-temperature engine body 2 is cooled, and fills the upper portion of the water jacket 3.

  The waste heat recovery apparatus 1 further includes a vaporized cooling medium, that is, a vapor path 6 through which the vapor flows. In the steam path 6, a superheater 7 and a turbine 8 are disposed in order from the upstream side, and an end thereof is connected to an upper portion 9 a of the condenser 9. An exhaust path 14 connected to the exhaust port 13 of the engine body 2 is drawn into the superheater 7. The superheater 7 recovers heat from the exhaust gas in the exhaust path 14 and further gives heat to the steam passing through the steam passage 6, and improves the recovery efficiency of waste heat. The turbine 8 is driven by high-temperature, high-pressure steam that flows through the steam path 6. The turbine 3 includes a drive shaft 8 a that is common to the generator 15. For this reason, when the turbine 3 is driven, the generator 15 converts the thermal energy of the steam into electric energy and recovers it. The steam that has passed through the turbine 8 is condensed by the condenser 13 and returned to the cooling water. The turbine 8 and the generator 15 constitute an energy recovery device in the present invention.

  The waste heat recovery apparatus 1 further includes a cooling water passage 10 connected to the lower portion 9 b of the condenser 9 and the water jacket 3. The cooling water passage 10 is provided with a catch tank 11 and a second water pump 12 driven by a motor 12a in order from the upstream side. The cooling water condensed in the condenser 9 and returned to the liquid is temporarily stored in the catch tank 11 and then supplied again into the water jacket 3 by the second water pump 12.

  As described above, the waste heat recovery apparatus 1 forms a closed system in which the liquid cooling medium in the water jacket 3 becomes vapor, and is returned to the liquid again by the condenser 9 and supplied to the water jacket 3. ing. That is, there are formed a steam flow path through which a cooling medium vaporized by waste heat in the engine flows and a liquid flow path through which a liquid cooling medium flows. The steam flow path is mainly from the upper area of the water jacket 3 to the upper area of the condenser 9, and the liquid flow path is mainly from the lower area of the condenser 9 to the lower area of the water jacket 3. However, the ratio of the steam flow path and the liquid flow path varies depending on the generation and condensation of steam.

  Such a waste heat recovery apparatus 1 further includes a reserve tank 16 connected to the condenser 9. The condenser 9 and the reserve tank 16 are connected by a first passage 17 and a second passage 18 that connect the lower ends of both. A first check valve 20 that restricts the flow of the cooling medium, that is, liquid cooling water, from the reserve tank 16 to the condenser 9 is installed on the first passage 17. The valve opening pressure of the first check valve 20 is set to P1. Accordingly, when the vapor pressure in the condenser 9 exceeds P1, the first check valve 20 is opened, and the liquid cooling water in the condenser 9 flows into the reserve tank 16. On the second passage 18, a second check valve 21 that restricts the flow of the cooling medium, that is, liquid cooling water, from the condenser 9 to the reserve tank 16 is installed. The valve opening pressure of the second check valve 21 is set to P2. Therefore, when the pressure in the condenser 9 falls below P2, the second check valve 21 is opened, and the liquid cooling water in the reserve tank 16 flows into the condenser 9. Here, the valve opening pressure P1 of the first check valve 20 is set to a value higher than the steam pressure in the normal state in consideration of the steam pressure in the waste heat recovery apparatus 1 operating normally. This is a measure for preventing cooling water from flowing out into the system, that is, from the condenser 9 to the reserve tank 16 more than necessary. On the other hand, the valve opening pressure P2 of the second check valve 21 is set to a negative pressure lower than the atmospheric pressure. The reserve tank 16, the first check valve 20, and the second check valve 21 constitute a liquid amount adjusting device in the present invention.

  The condenser 9 and the reserve tank 16 are also connected by a third passage 19 having one end connected to the upper part 9 a of the condenser 9. A third check valve 22 is installed on the third passage 19. The third check valve 22 functions as an air vent when air accumulates in the system due to some abnormality and the pressure increases due to this, and the valve opening pressure is set to P3. The valve opening pressure P3 is set to a value higher than the valve opening pressure P1 of the first check valve 20.

  In this way, the capacity of the reserve tank 16 connected to the condenser 9 takes into account the volume of the steam that occupies a part of the system when the engine is operating, and a capacity sufficiently larger than the volume of the steam is secured. Moreover, the reserve tank 16 is provided with the opening part 16a, and the internal pressure is equivalent to air | atmosphere.

  The operation of the waste heat recovery apparatus 1 configured as described above will be described with reference to FIGS. 1 and 2. First, the piping in the system is filled with liquid cooling water as shown in FIG. 2 until the engine is started and the warm-up is completed, that is, until the generation of cooling water vapor as a cooling medium starts. This cooling water is gradually heated by the combustion heat of the engine. At this time, although the 1st water pump 5 and the 2nd water pump 12 can also be made into an operation state, in the waste heat recovery apparatus 1 of a present Example, all are made into the stop state.

  When the warm-up is completed and steam starts to be generated in the system, the steam filled with a part of the condenser 9 in the turbine housing that houses the superheater 7 and the turbine 8 that is an expander is used. Push to the bottom side of the condenser 9 to move. On the other hand, the amount of water supplied by the second water pump 12 at this time, that is, the water pump for supplying the cooling water to the water jacket 3 is very small compared to the amount (volume) of steam generated in the engine. For this reason, the pressure in the system between the engine (water jacket 3) and the inlet of the second water pump 12 increases. When the pressure in the system exceeds P1 which is the valve opening pressure of the first check valve 20 due to such an increase in pressure, the first check valve is opened and cooling water is pushed out from the condenser 9 into the reserve tank 16. . Thereby, the cooling water and steam of the liquid in the system are replaced, and the Rankine cycle becomes operable. After this state is reached, if the engine continues to operate and steam continues to be generated, the Rankine cycle operation continues. At this time, the second check valve 21 does not open.

  Next, a case where the engine is stopped will be described. When the engine is stopped, heat transfer from the engine combustion chamber to the cooling water is eliminated, so that generation of steam inside the engine is also stopped. In this way, when the generation of vapor stops and the inside of the system cools, the vapor existing in the system condenses and begins to change into a liquid. As the vapor condenses into a liquid, the volume decreases and the pressure in the system decreases. When the pressure in the system falls below P2 which is the valve opening pressure of the second check valve 21 due to such a pressure drop, the second check valve 21 opens and the cooling water in the reserve tank 16 is condensed into the condenser. The cooling water returned into the condenser 9 and into the condenser 9 flows into the turbine housing, superheater 7 and piping in the system. Thereby, it can suppress that the system inside becomes a negative pressure. As a result, the pressure in the system can be maintained, and deformation of the piping can be suppressed against the external atmospheric pressure. When the engine is stopped, liquid cooling water is supplied into the system as shown in FIG.

  Next, an operation when some abnormality occurs in such a waste heat recovery apparatus 1 and other gas such as air is mixed in the system will be described. When a gas such as air is mixed in the system, the gas accumulates in the condenser 9 along with the flow of steam during Rankine cycle operation. When gas other than steam is stored in the condenser 9, the heat dissipation performance of the condenser 9 is degraded. As a result, when the amount of steam generated by the combustion heat is larger than the amount of steam condensed in the condenser 9, the pressure in the system exceeds the normal pressure during Rankine cycle operation. When such an increase in pressure exceeds the valve opening pressure of the third check valve 22, the third check valve 22 is opened and air is released to the reserve tank 16 side. Thereby, the air in the condenser 9 is discharged, and the condenser 9 can recover the heat dissipation capability. If the pressure in the system falls to the normal range, the third check valve 22 is closed.

  Next, a second embodiment of the present invention will be described with reference to FIGS. 3 and 4 are explanatory views showing a schematic configuration of the waste heat recovery apparatus 51 of the present embodiment. FIG. 3 shows a state in which the engine is operating and the vapor pressure in the system has increased, and FIG. 4 shows a state in which the engine has been stopped and cooled. The difference between the waste heat recovery apparatus 1 of the first embodiment and the waste heat recovery apparatus 51 of the second embodiment is that the waste heat recovery apparatus 1 includes the reserve tank 6, the first check valve 20, and the second check valve 21 as constituent elements. The waste heat recovery apparatus 51 includes a reserve tank 52 that is connected to the liquid flow path and is filled with cooling water that is a gas and liquid cooling medium. It is a point. Since the other components are the same as those in the first embodiment, the same components are denoted by the same reference numerals in the drawings, and detailed description thereof is omitted.

  In this embodiment, the reserve tank 52 is filled with nitrogen which is an inert gas. In addition, the capacity of the reserve tank 52 is sufficiently larger than the volume of the steam in consideration of the volume of the steam that occupies a part of the system when the engine is operating. In addition, the reserve tank 16 is in a sealed state except for the connection portion 52a of the pipe 53 provided in the lower portion. The reserve tank 53 is connected to the water jacket 3 by a pipe 53, and the cooling water in the reserve tank 52 goes to and from the liquid circulation path such as the water jacket 3, but the cooling water is completely discharged from the reserve tank 52. The capacity is set so as not to be lost. The connection position of the pipe 53 to the water jacket 3 is a position where the cooling water is always present in the water jacket 3. For this reason, nitrogen does not flow out to the water jacket 3 side. The connection of the pipe 53 to the liquid flow path is not limited to the water jacket 3, and may be a position where cooling water is always present, such as the lower part of the condenser 9.

  The operation of the waste heat recovery apparatus 51 configured as described above will be described with reference to FIGS. First, until the engine is started and the warm-up is completed, that is, until the generation of steam of cooling water as a cooling medium starts, the piping in the system is filled with liquid cooling water as shown in FIG. This cooling water is gradually heated by the combustion heat of the engine. The amount of cooling water in the reserve tank 52 has decreased, and the proportion of nitrogen has increased. At this time, although the 1st water pump 5 and the 2nd water pump 12 can also be made into an operation state, in the waste heat recovery apparatus 51 of a present Example, all are made into the stop state.

  When the warm-up is completed and steam starts to be generated in the system, the pressure in the system increases, and the cooling water in the water jacket 3 flows into the reserve tank 52 while compressing the nitrogen in the reserve tank 52. . On the other hand, in the turbine housing that houses the superheater 7 and the turbine 8 that is an expander, the cooling water filled in a part of the condenser 9 is pushed and moved to the bottom side of the condenser 9 by the generated steam. . Such cooling water is fed into the water jacket 3 by the second water pump 12 and then flows into the reserve tank 52. In this way, the cooling water in the system is replaced with steam. As described above, when steam is present in the system, the Rankine cycle becomes operable. After this state is reached, if the engine continues to operate and steam continues to be generated, the Rankine cycle operation continues.

  Next, a case where the engine is stopped will be described. When the engine is stopped, heat transfer from the engine combustion chamber to the cooling water is eliminated, so that generation of steam inside the engine is also stopped. In this way, when the generation of vapor stops and the inside of the system cools, the vapor existing in the system condenses and begins to change into a liquid. As the vapor condenses into a liquid, the volume decreases and the pressure in the system decreases. Due to such a pressure drop, the nitrogen in the reserve tank 52 expands, the cooling water in the reserve tank 52 is returned to the water jacket 3 side, and the cooling water returned into the water jacket 3 is supplied to the turbine housing in the system. , Flows into the superheater 7 and the piping. Thereby, it can suppress that the system inside becomes a negative pressure. As a result, the pressure in the system can be maintained, and deformation of the piping can be suppressed against the external atmospheric pressure. When the engine is stopped, liquid cooling water is supplied into the system as shown in FIG.

  As described above, according to the present invention, the cooling water in the reserve tank flows into the system when the pressure in the system decreases due to the engine being stopped and being cooled. The pressure in the system can be maintained, and deformation of piping can be suppressed against the external atmospheric pressure.

  The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited thereto. Various modifications of these embodiments are within the scope of the present invention. It is apparent from the above description that various other embodiments are possible within the scope. For example, the first check valve 20, the second check valve 21, and the third check valve 22 according to the first embodiment may be controlled by an ECU (Electronic Control Unit).

It is explanatory drawing which shows schematic structure of the waste heat recovery apparatus of Example 1, and is explanatory drawing which showed the state which the engine was operating and the vapor pressure in a system rose. It is explanatory drawing which shows schematic structure of the waste heat recovery apparatus of Example 1, and is explanatory drawing which showed the state which the engine stopped and was cooled. It is explanatory drawing which shows schematic structure of the waste heat recovery apparatus of Example 2, Comprising: It is explanatory drawing which showed the state which the engine was operating and the vapor pressure in a system rose. It is explanatory drawing which shows schematic structure of the waste heat recovery apparatus of Example 2, and is explanatory drawing which showed the state which the engine stopped and was cooled.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,51 Waste heat recovery apparatus 2 Engine main body 2a Cylinder block 2b Cylinder head 3 Water jacket 4 Cooling water injection nozzle 5 1st water pump 6 Steam path 7 Superheater 8 Turbine 9 Condenser 10 Cooling water passage 11 Catch tank 12 2nd Water pump 12a Motor 13 Exhaust port 14 Exhaust path 15 Generator 16, 52 Reserve tank 20 First check valve 21 Second check valve 22 Third check valve

Claims (7)

A steam flow path through which a coolant vaporized by waste heat in the engine flows;
A liquid flow path through which a cooling medium in a liquid state flows;
An energy recovery device for recovering energy from the steam in the steam flow path;
A liquid amount adjusting device for adjusting the amount of liquid in the liquid flow path according to the vapor pressure in the vapor flow path;
A waste heat recovery device comprising: The waste heat recovery apparatus according to claim 1,
A condenser for returning the vapor to a liquid;
The liquid amount adjusting device includes a reserve tank connected to the condenser, and adjusts the liquid amount between the condenser and the reserve tank according to a vapor pressure in the condenser. Waste heat recovery device. The waste heat recovery apparatus according to claim 1,
A condenser for returning the vapor to a liquid;
The liquid amount adjusting device includes a reserve tank connected to the condenser, a first check valve that restricts the flow of the cooling medium from the reserve tank to the condenser, and the condenser to the reserve tank. A waste heat recovery apparatus comprising: a second check valve for restricting inflow of a cooling medium; and adjusting a liquid amount between the condenser and the reserve tank in accordance with a vapor pressure in the condenser . The waste heat recovery apparatus according to claim 1,
The waste heat recovery apparatus according to claim 1, wherein the liquid amount adjusting device is a reserve tank connected to the liquid circulation path and filled with a gas and a liquid cooling medium. The waste heat recovery apparatus according to claim 1,
A waste heat recovery apparatus comprising a condenser for returning the vapor to a liquid, the condenser comprising a third check valve for releasing the air inside. The waste heat recovery apparatus according to claim 3,
The condenser includes a third check valve that releases internal air,
The waste heat recovery apparatus according to claim 1, wherein a valve opening pressure of the third check valve is larger than a valve opening pressure of the first check valve. An engine comprising the waste heat recovery device according to any one of claims 1 to 6.

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