JP2009097391A - Waste heat recovery device and engine provided with same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a waste heat recovery device discharging air immersing into a coolant circulation system and providing efficient waste heat recovery. <P>SOLUTION: A condenser 9 includes a fan 20 on the side in which air to be supplied for heat exchange is introduced in a core part 9c. The fan 20 improves cooling efficiency of the condenser 9 and also improves a condensation effect of steam. A drive part 20a of the fan 20 is electrically connected to ECU 19. The condenser 9 includes a shutter 21 on the side in which air to be supplied for heat exchange is introduced in the core part 9c. A drive part 21a of the shutter 21 is electrically connected to the ECU 19. When the shutter 21 is closed, introduction of air to the core part 9c is restricted and the condensation effect of the condenser 9 is dropped. The cooling effect of the condenser is dropped by stopping the fan 20. The pressure in the circulation system is increased thereby, and air inside the system is discharged to the reservoir tank 16. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a waste heat recovery apparatus that recovers waste heat in an engine through steam and an engine including the same.

  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. In such a waste heat recovery device, for example, the water cooling cooling system of the engine has a sealed structure, and the expander (turbine) is driven by the cooling water vaporized by the waste heat in the engine, that is, steam, and the heat possessed by the steam. There is one that converts energy into electrical energy and recovers it. For example, Patent Document 1 discloses an improved version of such a waste heat recovery apparatus. Moreover, the proposal which improves the thermal efficiency in a Rankine cycle is disclosed by patent document 2, for example.

JP 2000-345835 A JP 2001-182504 A

Such a waste heat recovery apparatus can perform efficient waste heat recovery as the pressure ratio of the expander increases. By the way, in an engine in which such a waste heat recovery apparatus is incorporated, since the temperature in the refrigerant circulation system decreases when the engine is stopped, condensation of steam begins. When the condensation of the vapor begins, the pressure in the circulation system drops rapidly. For this reason, even if it is a very small amount, air enters from the seal part of the circulation system and is gradually stored in the circulation system. When air enters the circulation system, the pressure in the condenser becomes higher than the saturated vapor pressure corresponding to the water temperature at that time when the waste heat recovery apparatus is operated or stopped.
This is because the infiltrated air does not condense even if the temperature drops. The condenser is usually installed on the downstream side of the expander, but if the width of the pressure drop in the condenser is small due to air infiltration, the pressure ratio before and after the expander cannot be increased, and the performance of the expander Decreases. As a result, the efficiency of waste heat recovery is also reduced. The greater the amount of infiltrated air, the lower the waste heat recovery efficiency.

  No effective countermeasures have been proposed for such a phenomenon, including the Rankine cycle proposed in Patent Document 2.

  Therefore, an object of the present invention is to propose a waste heat recovery apparatus that discharges air entering the refrigerant circulation system and can realize efficient waste heat recovery.

  In order to achieve such a problem, the waste heat recovery apparatus of the present invention includes a power recovery machine that recovers power via steam generated by overheating a refrigerant of an engine, and steam that has passed through the power recovery machine. A condenser for returning to a liquid refrigerant, a supply pump for supplying the liquid refrigerant to the engine, and air discharge means in the refrigerant circulation system are provided (claim 1). By setting it as such a structure, the pressure ratio before and behind an expander can be enlarged, and efficient waste heat recovery can be performed.

  The air discharge means in such a waste heat recovery apparatus includes a condenser operation suppressing means, and a reserve tank in which air inside the condenser is discharged together with the refrigerant when the inside of the condenser is pressurized. (Claim 2). The condenser is a heat exchanger that, when activated, cools the vapor back to liquid. Therefore, normally, efficient waste heat recovery is realized by increasing the cooling efficiency. However, the air that has entered the refrigerant circulation system is easily stored in the condenser, and even if the cooling efficiency is improved, the air does not condense, so it is difficult to improve the pressure ratio before and after the expander. Therefore, the operation of the condenser is intentionally suppressed to suppress a temperature drop in the condenser, and thereby the internal pressure is increased, or the internal pressure is discharged together with the refrigerant to the reserve tank. Thereby, the function of the condenser can be recovered, and efficient waste heat recovery can be performed.

  In order to increase the pressure inside the expander, the introduction of cooling air that exchanges heat with the refrigerant flowing inside the expander may be limited. In view of this, it is possible to adopt a configuration provided with a condenser operation suppressing means for restricting the introduction of cooling air into the condenser. As such a condenser operation | movement suppression means, there exists a shutter which interrupts | blocks the air which goes to a condenser, for example. Further, the operation of the fan that normally feeds air toward the condenser may be stopped.

  Such a condenser operation suppression means is preferably configured to operate based on the detection result of the intrusion air detection means (claim 4). This is because it is desirable to increase the pressure in the expander only when air is exhausted from the circulation system. Specifically, the intrusion air detection means determines the intrusion of air by comparing a pressure sensor, a water temperature sensor, a saturated vapor pressure corresponding to the water temperature, and a pressure in the system measured by the pressure sensor. And an arithmetic means (claim 5). When air is stored in the condenser, the pressure in the condenser is higher than the saturated vapor pressure corresponding to the water temperature at that time. In this way, the invasion of air in the circulation system can be determined by comparing the saturated vapor pressure corresponding to the water temperature at that time with the pressure in the system (in the circulation system) measured by the pressure sensor. When the intrusion of air is confirmed, the condenser operation suppressing means is operated to control the pressure in the condenser and discharge the air. On the other hand, when the discharge of air is confirmed, the condenser is operated to accelerate the condensation of the steam to reduce the pressure on the downstream side of the expander.

  The intrusion air detection means of such a waste heat recovery apparatus calculates the amount of air intrusion by comparing the saturated vapor pressure corresponding to the water temperature with the pressure in the system measured by the pressure sensor, and It can be set as the structure containing the calculating means which determines the operating time of the said condenser operation | movement suppression means from the amount of infiltration (Claim 6). By setting it as such a structure, the state which gives priority to discharge | emission of air and the state which gives priority to waste heat recovery can be switched appropriately.

  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, since air that has entered the refrigerant circulation system of the Rankine cycle can be discharged, the pressure ratio before and after the expander can be increased, and efficient waste heat recovery can be performed. .

  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 in which air entering the circulation system through which the refrigerant of the engine 2 circulates is discharged, and FIG. 2 shows a state in which waste heat recovery is promoted.

  The waste heat recovery apparatus 1 is incorporated in an engine 2 that is an internal 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 cooling water injection nozzles 4a and 4b installed in the cylinder head 2b. Cooling water, which is a refrigerant, 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 4a. Further, the cooling water injection nozzle 4b is supplied with the cooling water which is circulated through the Rankine cycle by the second water pump 12 and returned to the liquid. The cooling water injected from the cooling water injection nozzles 4 a and 4 b 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 vapor path 6 through which vaporized refrigerant, that is, vapor flows. A superheater 7, a turbine 8, and a heater 23 are disposed in this steam path 6 in this order from the upstream side, and the end thereof is connected to the upper tank 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 8 includes a drive shaft 8 a that is common to the generator 15. For this reason, when the turbine 8 is driven, the generator 15 converts the thermal energy of the steam into electrical energy and recovers it. The turbine 8 and the generator 15 constitute a power recovery machine in the present invention. The steam that has passed through the turbine 8 is condensed by the condenser 9 and returned to the cooling water.

  Here, the configuration of the condenser 9 will be described with reference to FIG. The condenser 9 includes an upper tank 9a, a lower tank 9b, and a core portion 9c. The condenser 9 cools the refrigerant flowing in the cooling pipe 9d by the air introduced into the core portion 9c, and returns the refrigerant from the vapor to the liquid.

  The upper tank 9a is provided with an introduction pipe 9e through which steam after passing through the heater 23 flows. The lower tank 9b includes a first discharge pipe 9f and a second discharge pipe 9g for discharging the refrigerant that has become liquid. The core portion 9c includes a cooling pipe 9d and fins 9h. The core portion 9c has a configuration in which fins 9h are arranged in parallel between a plurality of cooling pipes 9d arranged in parallel. The core portion 9c is assembled to the upper tank 9a and the lower tank 9b so that the cooling pipe 9d communicates between the upper tank 9a and the lower tank 9b.

  A pressure sensor 17 for measuring the pressure in the condenser 9 is attached to the upper tank 9a. The lower tank 9b is equipped with a water temperature sensor 18 for measuring the temperature of the condensed cooling water. The pressure sensor 17 may be mounted anywhere as long as the pressure in the condenser 9 can be measured, but the water temperature sensor 18 does not measure the temperature of the steam having a high temperature before condensation. The cooling water is attached to the lower tank 9b. Both the pressure sensor 17 and the water temperature sensor 18 are electrically connected to an ECU (Electronic control unit) 19. The ECU 19 has the function of the calculation means in the present invention, and constitutes the intrusion air detection means in the present invention together with the pressure sensor 17 and the water temperature sensor 18. The ECU 19 calculates the saturated vapor pressure corresponding to the water temperature measured by the water temperature sensor 18 and compares the pressure measured by the pressure sensor 17 to detect the intrusion of air into the circulation system of the refrigerant.

  The condenser 9 includes a fan 20 on the side where air to be used for heat exchange in the core portion 9c is introduced. This fan 20 improves the cooling efficiency in the condenser 9, and improves the condensing effect of a vapor | steam. The drive unit 20a of the fan 20 is electrically connected to the ECU 19. The condenser 9 further includes a shutter 21 on the side where air to be used for heat exchange in the core portion 9c is introduced. The drive unit 21 a of the shutter 21 is electrically connected to the ECU 19. When the shutter 21 is in a closed state, the introduction of air into the core portion 9c is suppressed, and the condensation effect of the condenser 9 is reduced. That is, the shutter 21 corresponds to the condenser operation suppressing means in the present invention. Moreover, the cooling effect in the condenser 9 is reduced by stopping the fan 20 and the condensation effect is suppressed, and in this sense, it corresponds to the condenser operation suppressing means in the present invention.

  The waste heat recovery apparatus 1 includes a cooling water passage 10 that connects the lower tank 9 b of the condenser 9 and the water jacket 3. The cooling water passage 10 and the condenser 9 are connected by a first discharge pipe 9f. In this cooling water passage 10, a catch tank 11, a second water pump 12 corresponding to a supply pump in the present invention, and a heater 23 are arranged in this 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. At that time, the cooling water is heated by the heater 23 from the high-temperature steam and becomes high temperature. Thereby, it becomes easy to evaporate in the water jacket 3, and efficient waste heat recovery can be performed. Thus, the system forming the Rankine cycle constitutes the refrigerant circulation system of the present invention.

  Such a waste heat recovery apparatus 1 further includes a reserve tank 16 connected to the condenser 9. The reserve tank 16 is connected to the condenser 9 via a discharge pipe 22 connected to the second discharge pipe 9g. The outlet of the discharge pipe 22 is arranged so as to open in the liquid stored in the reserve tank 16. The reserve tank 16 has an opening 16a, and the air discharged into the reserve tank 16 is released to the atmosphere. A one-way valve 24 that allows only the flow from the condenser 9 side to the reserve tank 16 side is mounted in the middle of the discharge pipe 22.

The operation of the waste heat recovery apparatus 1 configured as described above will be described with reference to the flowchart shown in FIG.
First, in step 1, the ECU 19 acquires the pressure Pg in the condenser 9 from the pressure sensor 17. At the same time, the water temperature of the cooling water accumulated in the condenser 9 is acquired from the water temperature sensor 18. The ECU 19 calculates a saturated vapor pressure Pw corresponding to the water temperature from the water temperature. Specifically, the saturated vapor pressure Pw is calculated from a map stored in the ECU 19.

  In step S2, the ECU 19 determines whether or not the condenser internal pressure Pg is larger than the saturated vapor pressure Pw. When it is determined Yes in step S2, the process proceeds to step S4. On the other hand, when it is determined No in step S2, the process proceeds to step S3. In step S3, the shutter 21 is opened and the fan 20 is operated. When the condenser internal pressure Pg is smaller than the saturated vapor pressure Pw, it can be determined that air has not entered the circulation system. Therefore, by opening the shutter 21 and operating the fan 20 as shown in FIG. 2, a large amount of air is sent to the condenser 9 to improve the cooling effect and promote condensation. When condensation in the condenser 9 is promoted, the pressure in the circulation system decreases. Thereby, the pressure ratio before and behind the turbine 8 is increased, and the turbine efficiency is improved. As a result, the efficiency of waste heat recovery is improved.

  On the other hand, in step S4, the difference between Pg and Pw acquired in step S1 is calculated, and the air discharge time Th is determined from the value. The greater the difference between Pg and Pw, the greater the amount of air that has entered the circulatory system, so the air discharge time Th becomes longer. This air discharge time Th is a time for which the pressure in the condenser Pg exceeds the atmospheric pressure by the measure started in step S5 and the measure of step 5 is continued from that point.

  In step S5 performed subsequent to step S4, the shutter 21 is closed and the operation of the fan 20 is stopped as shown in FIG. Supplying air to the condenser 9 is suppressed by closing the shutter 21 and stopping the operation of the fan 20. Thereby, the cooling effect | action in the condenser 9 falls and the temperature and pressure in a circulation system rise.

  Even after the measure of the ECU S5 is taken, the condenser internal pressure Pg is acquired in step S6. In step S7, the ECU 19 determines whether or not the condenser internal pressure Pg acquired in step S6 has become higher than the atmospheric pressure. When the pressure in the circulation system rises and becomes larger than the atmospheric pressure, the air accumulated in the condenser 9 is discharged into the reserve tank 16 together with the steam. When it is determined No in step S7, the measures in steps S5 and S6 are repeated. When it is determined Yes in step S7, the process proceeds to step S8, where the counting of time Th is started, and it is determined whether time Th has elapsed. If the time Th elapses after the condenser internal pressure Pg becomes equal to or higher than the atmosphere, it can be determined that the air in the circulation system has been exhausted.

  As described above, when each part constituting the waste heat recovery apparatus 1 operates, the air that has entered the circulation system is discharged, and the function of the condenser 9 can be maintained.

  The above-described embodiments are merely examples for carrying out the present invention, and the present invention is not limited to them. 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 operation of the condenser 9 can be suppressed only by stopping the fan 20 without providing the shutter 21 and without opening and closing the shutter 21. Furthermore, the fan 20 may not be provided, and only the opening / closing control of the shutter 21 may be performed.

It is explanatory drawing which showed schematic structure of the waste heat recovery apparatus of an Example, and is explanatory drawing of the state which discharges the air which infiltrated into the circulation system through which the refrigerant | coolant of an engine circulates. It is explanatory drawing which showed schematic structure of the waste heat recovery apparatus of a present Example, and is explanatory drawing of the state which accelerates | stimulates waste heat recovery. It is a perspective view of a condenser. It is a flowchart which shows an example of control of a waste heat recovery apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Waste heat recovery apparatus 2 Engine 2a Cylinder block 2b Cylinder head 3 Water jacket 4a, b Cooling water injection nozzle 5 1st water pump 6a Steam path 7 Superheater 8 Turbine 9 Condenser 10 Cooling water passage 11 Catch tank 12 2nd water Pump 13 Exhaust port 14 Exhaust path 15 Generator 16 Reserve tank 17 Hydraulic sensor 18 Water temperature sensor 19 ECU
20 Fan 21 Shutter 22 Discharge pipe 23 Heater 24 One-way valve

Claims (7)

A power recovery machine that recovers power through steam generated by overheating the refrigerant of the engine;
A condenser for returning the vapor after passing through the power recovery machine to a liquid refrigerant;
A supply pump for supplying liquid refrigerant to the engine;
Air discharge means in the refrigerant circulation system;
A waste heat recovery device comprising: The waste heat recovery apparatus according to claim 1,
The air discharge means is
A condenser operation suppressing means;
A reserve tank in which air inside the condenser is discharged together with the refrigerant when the inside of the condenser is pressurized;
Waste heat recovery device characterized by including The waste heat recovery apparatus according to claim 1,
The air discharge means is
A condenser operation suppressing means for restricting introduction of cooling air to the condenser;
A reserve tank in which air inside the condenser is discharged together with the refrigerant when the inside of the condenser is pressurized;
Waste heat recovery device characterized by including The waste heat recovery apparatus according to claim 1,
The air discharge means is
Intrusion air detection means;
Condenser operation suppression means that operates based on the detection result of the intrusion air detection means;
A reserve tank in which air inside the condenser is discharged together with the refrigerant when the inside of the condenser is pressurized;
Waste heat recovery device characterized by including The waste heat recovery apparatus according to claim 4,
The intrusion air detection means includes
A pressure sensor, a water temperature sensor,
A calculation means for comparing the saturated vapor pressure corresponding to the water temperature and the pressure in the system measured by the pressure sensor to determine the intrusion of air;
Waste heat recovery device characterized by including The waste heat recovery apparatus according to claim 4,
The intrusion air detection means includes
A pressure sensor, a water temperature sensor,
The saturated vapor pressure corresponding to the water temperature and the pressure in the system measured by the pressure sensor are compared to calculate the amount of intrusion of air, and the operation time of the condenser operation suppression means is determined from the amount of intrusion of air. Computing means;
Waste heat recovery device characterized by including An engine comprising the waste heat recovery device according to any one of claims 1 to 6.

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