JP2012102645A - Rankine cycle system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent breakage of piping caused by freezing of a cooling medium.SOLUTION: A Rankine cycle system 100 includes: a vapor flow passage 3b through which vaporized cooling medium passes by waste heat in an engine 1; an expander 10 recovering energy from a vapor in the vapor flow passage 3b; a condensed water tank 14 storing the cooling medium in which the vapor via the expander 10 is condensed and liquefied; a detection means detecting the stop of the engine 1; and a nozzle 20 introducing, into the vapor flow passage 3b, compressed air for pushing out the vapor remaining in the vapor flow passage 3b to the condensed water tank 14 when the stop of the engine 1 is detected.

Description

  The present invention relates to a Rankine cycle system.

  Conventionally, a Rankine cycle that recovers waste heat associated with the operation of an internal combustion engine is known. In such Rankine cycle, for example, boiling cooling is performed by using a water cooling cooling system of the engine as a closed structure, and an expander such as a steam turbine is driven by refrigerant evaporated by waste heat in the engine, that is, steam, There is one that recovers heat energy of the steam by converting it into electrical energy or the like. As an example of improving such a Rankine cycle system, there is Patent Document 1, for example.

JP 2008-121615 A

  In the Rankine cycle system of Patent Document 1, the steam generated from the engine flows from the engine whose pressure is high due to the boiling of the refrigerant to the low-pressure condensed water tank. However, when the engine stops, the boiling in the engine stops and the pressure difference between the engine and the condensed water tank disappears. When the pressure difference disappears, the steam no longer flows from the engine to the condensed water tank, and the vaporized refrigerant remains in the pipe. The refrigerant remaining in the pipe may be frozen when it is cold, and the freezing of the refrigerant in the pipe leads to breakage of the pipe or the like.

  Therefore, the Rankine cycle system disclosed in the present specification has an object to suppress damage to piping due to freezing of the refrigerant.

  In order to solve this problem, a Rankine cycle system disclosed in this specification includes a steam flow path through which a cooling medium vaporized by waste heat in an internal combustion engine flows, and energy for recovering energy from the steam in the steam flow path. A recovery unit, a storage unit for storing the cooling medium condensed and liquefied through the energy recovery unit, a detection unit for detecting the stop of the internal combustion engine, and when the stop of the internal combustion engine is detected, Compressed air introduction means for introducing into the steam flow path compressed air that pushes the steam remaining in the steam flow path to the reservoir.

  According to the above configuration, when the internal combustion engine is stopped, the compressed air is introduced into the system from the steam flow path to the storage portion. The cooling medium is pushed out to the storage part. Thereby, it can suppress that a refrigerant | coolant remains in a vapor | steam flow path by the stop of an engine, and it can suppress that piping etc. are damaged by freezing of the refrigerant | coolant which remained in the vapor | steam flow path.

  According to the Rankine cycle system disclosed in this specification, breakage of piping is suppressed.

FIG. 1 is a schematic configuration diagram of a Rankine cycle system according to an embodiment. FIG. 2 is a flowchart illustrating an example of control of the Rankine cycle system according to the embodiment.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings.

  A schematic configuration of the Rankine cycle system 100 will be described with reference to FIG. FIG. 1 is a schematic configuration diagram of a Rankine cycle system 100. The Rankine cycle system 100 includes an engine 1 that is cooled by boiling a refrigerant therein. The engine 1 is an example of an internal combustion engine. The engine 1 includes a cylinder block 1a and a cylinder head 1b. A water jacket is formed in the cylinder block 1a and the cylinder head 1b, and the engine 1 is cooled by boiling the refrigerant in the water jacket. At this time, the engine 1 generates steam. The engine 1 further includes an exhaust pipe 2. One end of an introduction passage 3 a for introducing the mixed refrigerant in the water jacket into the gas-liquid separator 4 is connected to the cylinder head 1 b of the engine 1.

  The other end of the introduction passage 3 a is connected to the gas-liquid separator 4. The mixed refrigerant flowing into the gas-liquid separator 4 in the gas-liquid mixed state from the engine 1 side is separated into a gas phase (vapor) and a liquid phase (liquefied refrigerant) in the gas-liquid separator 4. One end of the refrigerant circulation path 5 is connected to the lower end of the gas-liquid separator 4. The other end of the refrigerant circulation path 5 is connected to the cylinder block 1a. A first water pump 6 that pumps the liquefied refrigerant into the engine 1 is disposed in the refrigerant circulation path 5. The first water pump 6 is a so-called mechanical type and uses a crankshaft provided in the engine 1 as a drive source. The first water pump 6 circulates the liquefied refrigerant between the engine 1 and the gas-liquid separator 4.

  The upper end portion of the gas-liquid separator 4 is connected to one end of the steam flow path 3b. A superheater 8, an expander 10, a condenser 12, and a condensed water tank 14 are arranged in this order in the steam flow path 3b. The steam separated by the gas-liquid separator 4 flows into the superheater 8.

  The exhaust pipe 2 is drawn into the superheater 8. Inside the exhaust pipe 2, exhaust gas generated by the engine 1 circulates. The exhaust pipe 2 passes through the superheater 8, and the exhaust gas passes through the inside thereof. The exhaust gas exchanges heat with the steam separated by the gas-liquid separator 4. Thereby, while generating amount of steam increases, the superheat degree of steam improves and waste heat recovery efficiency improves. A steam discharge pipe for discharging steam is provided at the upper end portion of the superheater 8, and a nozzle 9 is provided at the tip portion thereof.

  An expander (energy recovery device) 10 is disposed downstream of the superheater 8. The expander 10 is driven by vaporized refrigerant supplied from the superheater 8, that is, steam, and performs energy recovery. The expander 10 is a steam turbine including a case 10a and a turbine blade 10b provided in the case 10a. The nozzle 9 is attached to the case 10a so that the steam supplied through the steam flow path 3b is injected toward the turbine blade 10b. Thereby, the turbine blade 10b is rotationally driven by the steam supplied through the steam flow path 3b. The rotational force of the turbine blade 10b assists the rotation of the crankshaft provided in the engine 1 or drives the generator. Thereby, recovery of waste heat is performed.

  On the downstream side of the expander 10, there is provided a discharge passage 11 for discharging the cooling medium after the energy is recovered. One end of the discharge passage 11 is connected to the expander 10. The other end of the discharge passage 11 is connected to the capacitor 12. The discharge passage 11 discharges the steam from the expander 10 and introduces the discharged steam into the condenser 12. The condenser 12 is condensed by cooling the vapor to generate a liquefied refrigerant. The condenser 12 receives the air blown by the fan 13 and can efficiently cool and condense the steam. A condensed water tank (storage unit) 14 that stores the liquefied refrigerant generated in the capacitor 12 is installed below the capacitor 12.

  A refrigerant recovery path 16 is provided on the downstream side of the condensed water tank 14 for recirculating the liquefied refrigerant once stored in the condensed water tank 14 to the engine 1 side. The refrigerant recovery path 16 is connected to the upstream side of the first water pump 6 in the refrigerant circulation path 5. A second water pump 17 is disposed in the refrigerant recovery path 16. The second water pump 17 is an electric vane pump. When the second water pump 17 is activated, the liquefied refrigerant in the condensed water tank 14 is supplied to the refrigerant circulation path 5. In addition, a one-way valve 18 for avoiding the back flow of the refrigerant is disposed downstream of the second water pump 17. As described above, the Rankine cycle system 100 includes a path through which the refrigerant circulates.

  In addition, the Rankine cycle system 100 according to the embodiment includes a mechanism for pushing steam remaining in the pipe after the engine is stopped to the condensed water tank 14. Specifically, in the Rankine cycle system 100, the nozzle 20 is provided in the vicinity of the connection location between the steam flow path 3b and the gas-liquid separator 4. The nozzle 20 is connected to the air tank 21. The air tank 21 is connected to the air compressor 22 and stores the compressed air generated by the air compressor 22. The air compressor 22 generates compressed air by the driving force of the engine 1 and sends the compressed air into the air tank 21.

  The nozzle 20 includes an electromagnetic valve 23. The opening and closing of the electromagnetic valve 23 is controlled by an ECU 19 described later. When the electromagnetic valve 23 is opened, the compressed air stored in the air tank 21 is introduced from the nozzle 20 into the steam flow path 3b. The compressed air introduced from the nozzle 20 into the steam flow path 3b pushes the steam remaining in the steam flow path 3b to the condensed water tank 14.

  The Rankine cycle system 100 includes an ECU (Electronic control unit) 19 that functions as part of the detection means and the compressed air introduction means. The ECU 19 includes an electromagnetic valve 23 provided in the nozzle 20, a pressure sensor 24 that measures the pressure in the air tank 21, an air compressor 22, the engine 1, and a pressure sensor 25 that measures the pressure in the condensed water tank 14. Are electrically connected. In addition, the structure which combined the nozzle 20, the air tank 21, the air compressor 22, the pressure sensor 24, the electromagnetic valve 23, and ECU19 mentioned above corresponds to a compressed air introduction means.

  The ECU 19 operates the air compressor 22 until the pressure in the air tank 21 reaches a predetermined pressure, and sends compressed air into the air tank 21. The ECU 19 acquires the pressure in the air tank 21 from the pressure sensor 24, and stops the air compressor 22 when the pressure in the air tank 21 reaches a predetermined pressure. The predetermined pressure is a pressure measured when compressed air is stored in the air tank 21 in such an amount that the steam remaining in the pipe can be pushed out.

  The ECU 19 acquires the engine speed from the engine 1 and determines whether or not the engine is stopped. When the engine is stopped, the ECU 19 opens the electromagnetic valve 23 to introduce the compressed air stored in the air tank 21 from the nozzle 20 into the steam flow path 3b. Specifically, when the engine stops, the ECU 19 instructs the electromagnetic valve 23 to open the valve. The electromagnetic valve 23 opens the valve based on a command from the ECU 19. When the electromagnetic valve 23 is opened, the compressed air stored in the air tank 21 is introduced from the nozzle 20 into the steam flow path 3b. The compressed air introduced into the steam flow path 3b moves toward the condensed water tank 14 while pushing out the steam remaining in the steam flow path 3b from the gas-liquid separator 4 to the condensed water tank 14. As a result, the steam remaining in the steam flow path 3 b connecting the gas-liquid separator 4 to the condensed water tank 14 is pushed out to the condensed water tank 14.

  Next, an example of control executed by the ECU 19 will be described. FIG. 2 is a flowchart illustrating an example of control executed by the ECU 19.

  The ECU 19 acquires the engine speed from the engine 1 (step S11).

  The ECU 19 determines whether the engine is stopped based on the acquired engine speed (step S13). For example, the ECU 19 determines that the engine is stopped when the engine speed is 0 for a predetermined time.

  When the engine is not stopped (step S13 / NO), the ECU 19 continues the process from step S11. When the engine is stopped (step S13 / YES), the ECU 19 controls the electromagnetic valve 23 to open the valve (step S15). Thereby, the compressed air stored in the air tank 21 is introduced from the nozzle 20 into the steam flow path 3b.

  ECU19 determines whether the pressure in the condensed water tank 14 became equal to the pressure in the air tank 21 (step S17). When the pressure in the condensed water tank 14 and the pressure in the air tank 21 are equal, it can be said that the compressed air stored in the air tank 21 has been released. Therefore, when the pressure in the condensed water tank 14 becomes equal to the pressure in the air tank 21 (step S17 / YES), the ECU 19 controls the electromagnetic valve 23, closes the valve (step S19), and ends this process. To do. When the pressure in the condensed water tank 14 is not equal to the pressure in the air tank 21 (step S17 / NO), the ECU 19 repeats the process of step S17.

  As described above, according to the Rankine cycle system disclosed in this specification, when the engine is stopped, the electromagnetic valve 23 is opened by a command from the ECU 19, and the compressed air stored in the air tank 21 flows from the nozzle 20 to the steam flow path. Introduce into 3b. As a result, when the engine 1 is stopped, the remaining steam without flowing from the engine 1 to the condensed water tank 14 is pushed out to the condensed water tank 14 by the compressed air. And it can suppress that a vapor | steam remains in the vapor | steam distribution path 3b from the gas-liquid separator 4 to the condensed water tank 14. FIG. As a result, it is possible to prevent the piping from being damaged due to freezing of the refrigerant remaining in the steam flow path 3b.

  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, in the above-described embodiment, the ECU 19 determines whether or not the engine 1 has stopped using the rotational speed of the engine 1. However, the ECU 19 may determine whether or not the engine 1 has been stopped based on, for example, ON / OFF of an ignition switch.

  In the above-described embodiment, the air compressor 22 is driven by the engine 1, but may be driven by electricity other than the engine 1.

DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Exhaust pipe 3a ... Introduction passage 3b ... Steam distribution path 4 ... Gas-liquid separator 5 ... Refrigerant circulation path 6 ... 1st water pump (W / P)
8 ... Superheater 9 ... Nozzle 10 ... Expander 10a ... Turbine case 10b ... Turbine blade 11 ... Discharge passage 12 ... Condenser 13 ... Fan 14 ... Condensed water tank 16 ... Refrigerant recovery passage 17 ... Second water pump (W / P)
18 ... One-way valve 19 ... ECU
20 ... Nozzle 21 ... Air tank 22 ... Air compressor 23 ... Electromagnetic valve 24, 25 ... Pressure sensor 100 ... Rankine cycle system

Claims (1)

A steam flow path through which a coolant vaporized by waste heat in the internal combustion engine flows;
An energy recovery device for recovering energy from the steam in the steam flow path;
A storage section for storing a cooling medium in which the vapor having passed through the energy recovery device is condensed and liquefied;
Detecting means for detecting a stop of the internal combustion engine;
Compressed air introduction means for introducing into the steam flow path compressed air that pushes the steam remaining in the steam flow path to the reservoir when the stop of the internal combustion engine is detected;
A Rankine cycle system comprising:

Images