JP5310622B2 - Rankine cycle system - Google Patents

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 2009-103060 A

  By the way, the Rankine cycle system as described above may include a gas-liquid separator that separates vapor, which is vaporized refrigerant generated in the engine, from liquefied refrigerant in order to take out the vapor that drives the expander. The engine included in the Rankine cycle system does not immediately drop in temperature even after stopping. For this reason, there is a possibility that the boiling of the refrigerant will continue in the engine. If boiling of the refrigerant in the engine continues, it is conceivable that the refrigerant in the water jacket provided in the engine is pushed out into the gas-liquid separator. Even if the engine is stopped due to excessive liquid refrigerant in the water jacket, the refrigerant in the water jacket will be pushed into the gas-liquid separator when boiling of the refrigerant starts in the engine at the next engine start. It is possible that

  When a large amount of liquefied refrigerant flows into the gas-liquid separator, there is a concern that the function of the gas-liquid separator deteriorates. When the function of the gas-liquid separator is lowered, the liquefied refrigerant flows into the superheater or the expander to be arranged on the downstream side of the gas-liquid separator, which may damage these devices.

  Therefore, the Rankine cycle system disclosed in this specification is intended to maintain an appropriate amount of refrigerant in the water jacket when the engine is stopped.

  In order to solve such a problem, a Rankine cycle system disclosed in this specification includes a water jacket formed therein, an engine that is cooled by boiling of a coolant flowing through the water jacket, and a communication with the water jacket. A gas-liquid separator that separates the refrigerant supplied from the water jacket into a vapor that is a vaporized refrigerant and a liquefied refrigerant, a superheater that is supplied with the vapor separated in the gas-liquid separator, and the superheater An expander that is driven by steam supplied from and recovers energy, a condenser that condenses the steam that has passed through the expander to generate liquefied refrigerant, and a condensed water tank that stores the liquefied refrigerant generated in the condenser And a water pump, and the liquefied refrigerant in the condensate tank is used as the water jacket or the gas-liquid. A first liquefied refrigerant passage to be supplied to the separator, a control valve, a second liquefied refrigerant passage connecting the condensed water tank and the water jacket or the gas-liquid separator, and restarting when the engine is stopped And a control unit that opens the control valve for a predetermined period of time.

  Excessive liquefied refrigerant is discharged from the water jacket or gas-liquid separator by opening the control valve for a predetermined period from when the engine is stopped to when the engine is restarted. be able to. Thereby, the refrigerant | coolant in a water jacket at the time of an engine stop can be maintained at an appropriate quantity. And it is suppressed that a liquefied refrigerant | coolant flows into a gas-liquid separator excessively immediately after an engine stop or at the time of engine restart. As a result, the function of the gas-liquid separator can be maintained. As a result, it is possible to avoid the liquefied refrigerant from flowing into the superheater or the expander to be disposed on the downstream side of the gas-liquid separator, and to suppress the breakage of these devices.

  According to the Rankine cycle system disclosed in the present specification, it is possible to maintain an appropriate amount of refrigerant in the water jacket when the engine is stopped.

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 in 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 includes a cylinder block 1a and a cylinder head 1b. Water jackets 1a1 and 1b1 are formed inside the cylinder block 1a and the cylinder head 1b, and the engine 1 is cooled by boiling the refrigerant flowing through the water jacket. At this time, the engine 1 generates steam. The engine 1 further includes an exhaust pipe 2. One end of a steam passage 3 communicating with the water jackets 1a1 and 1b1 is connected to the cylinder head 1b of the engine 1.

  A gas-liquid separator 4 is disposed in the steam passage 3. The gas-liquid separator 4 separates the refrigerant supplied from the water jackets 1a1 and 1b1 into vapor and liquefied refrigerant that are vaporized refrigerant. That is, the refrigerant flowing into the gas-liquid separator 4 from the engine 1 side in the gas-liquid mixed state is separated into the gas phase (vapor) and the 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 a water jacket 1a1 in 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. In the present specification, the circuit that circulates between the engine 1 and the gas-liquid separator 4 is hereinafter referred to as a refrigerant circulation circuit A. The refrigerant circuit A is surrounded by a dotted line in FIG.

  A superheater 8 is provided in the steam passage 3. The steam separated in the gas-liquid separator 4 is mainly supplied to the superheater 8. The superheater 8 includes an evaporation unit 8a on the lower side and a superheating unit 8b on the upper side. 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 penetrates the superheater 8 so that the exhaust gas passes through the superheater 8b and the evaporator 8a in this order. One end of the liquefied refrigerant passage 7 is connected to the evaporation unit 8a. The exhaust gas exchanges heat with the steam that has passed through the gas-liquid separator 4. The other end of the liquefied refrigerant passage 7 is connected to the lower end of the gas-liquid separator 4. The liquefied refrigerant passage 7 is provided with an on-off valve 7a electrically connected to an ECU (Electronic control unit) 21 described later. The supply state of the liquefied refrigerant from the gas-liquid separator 4 to the evaporation unit 8a is determined by the open / close state of the open / close valve 7a. The liquefied refrigerant supplied to the evaporation unit 8a can be vaporized by the heat of the exhaust gas after the vapor is superheated by the superheating unit 8b. Thereby, while generating amount of steam increases, the superheat degree of steam improves and waste heat recovery efficiency improves. A steam exhaust pipe 3a is provided at the upper end of the superheated part 8b. A nozzle 9 is provided at the tip of the steam discharge pipe 3a. The ECU 21 is an example of a control unit.

  An expander 10 is disposed on the downstream side 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 passage 3 is injected toward the turbine blade 10b. Thereby, the turbine blade 10 b is rotationally driven by the steam supplied through the steam passage 3. 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.

  The case 10a of the expander 10 is provided with a discharge port 10a1 for discharging steam. One end of the steam discharge passage 11 is connected to the discharge port 10a1. The other end of the steam discharge passage 11 is connected to a capacitor 12. The steam discharge passage 11 discharges the steam from the expander 10 and introduces the discharged steam into the condenser 12. The condenser 12 condenses the vapor that has passed through the expander 10 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 14 for storing the liquefied refrigerant generated in the capacitor 12 is installed below the capacitor 12.

  A first liquefied refrigerant passage 16 that recirculates the liquefied refrigerant once stored in the condensed water tank 14 to the engine 1 side is provided on the downstream side of the condensed water tank 14. The first liquefied refrigerant passage 16 is connected to the upstream side of the first water pump 6 in the refrigerant circulation passage 5. A second water pump 17 is disposed in the first liquefied refrigerant passage 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. Thereby, the liquefied refrigerant in the condensed water tank 14 can be supplied to the water jacket 1 a 1 or the gas-liquid separator 4. The liquefied refrigerant in the condensed water tank 14 can flow into either the water jacket 1a1 or the gas-liquid separator 4 depending on the state of the refrigerant in the water jackets 1a1 and 1b1 and the gas-liquid separator 4. 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.

  The first liquefied refrigerant passage 16 is branched from the second liquefied refrigerant passage 19 between the condensed water tank 14 and the second water pump 17. The second liquefied refrigerant passage 19 is connected to the upstream side of the first water pump 6 in the refrigerant circuit 5. Further, a control valve 19 a is disposed in the second liquefied refrigerant passage 19. Here, the refrigerant circulation path 5 is a pipe that connects the water jacket 1 a 1 and the gas-liquid separator 4. The second liquefied refrigerant passage 19 is connected to the refrigerant circulation path 5, thereby connecting the condensed water tank 14, the water jacket 1 a 1, and the gas-liquid separator 4. When the control valve 19a is opened, the second liquefied refrigerant passage can collect the liquefied refrigerant in the water jackets 1a1, 1b1 to the condensed water tank 14 side through the refrigerant circulation path 5. The positional relationship among the gas-liquid separator 4, the cylinder block 1a, the condensed water tank 14, and the second liquefied refrigerant passage 19 is such that excessive liquefied refrigerant in the water jackets 1a1 and 1b1 can be discharged to the condensed water tank 14 side. Adjust as appropriate. At this time, the necessary minimum liquid level in the water jackets 1a1 and 1b1 is taken into consideration. Specifically, the connection position of the second liquefied refrigerant passage 19 to the refrigerant circulation path 5 is set to be equal to or lower than the necessary minimum liquid level in the water jackets 1a1 and 1b1. The necessary minimum liquid level is a liquid level that ensures the minimum amount of liquefied refrigerant required for cooling the engine 1. Thereby, the excess liquefied refrigerant in the water jackets 1a1 and 1b1 can flow down to the condensed water tank 14 through the second liquefied refrigerant passage 19 and be collected. By ensuring the required minimum liquid level in the water jackets 1a1, 1b1, it is possible to avoid bumping of the liquefied refrigerant in the water jackets 1a1, 1b1.

  The second liquefied refrigerant passage 19 is connected to any part of the refrigerant circuit A as long as the liquefied refrigerant in the water jackets 1a1 and 1b1 can flow down and be collected on the condensed water tank 14 side. May be.

  The Rankine cycle system 100 includes an ECU 21 as an example of a control unit. The Rankine cycle system 100 includes a float type liquid level sensor 15 in the gas-liquid separator 4. The ECU 21 is electrically connected to a temperature sensor 20 mounted on the on-off valve 7a, the second water pump 17, the control valve 19a, and the cylinder head 1b.

  The second water pump 17 is driven and controlled by the ECU 21. Specifically, when the liquid level of the cooling medium in the gas-liquid separator 4 is lowered by the liquid level sensor 15, a drive command is issued by the ECU 21, and liquefied cooling is pumped from the condensed water tank 14 to the engine 1 side. To do. Thereby, it is possible to avoid a situation in which the liquid-phase cooling medium is insufficient in the engine 1.

  Next, an example of control of the Rankine cycle system 100 when the engine 1 is stopped will be described with reference to FIG. The ECU 21 opens the control valve for a predetermined period from when the engine 1 is stopped to when it is restarted. Here, the predetermined period is a period during which the amount of the liquefied refrigerant in the water jackets 1a1, 1b1 can be reduced to an appropriate amount. The timing for opening the control valve 19a may be any time from when the engine 1 is stopped to when it is restarted. For example, the control valve 19a can be opened at the timing when the ignition is turned off when the engine is stopped, or at the timing when the ignition is turned on when the engine is restarted. The amount of the liquefied refrigerant in the water jackets 1a1 and 1b1 may be adjusted until the liquefied refrigerant in the water jackets 1a1 and 1b1 starts to boil. Therefore, it is desirable to adjust the amount of liquefied refrigerant by opening the control valve 19a at the timing of ignition ON at the latest. Thereby, it can suppress that the liquefied refrigerant | coolant in water jacket 1a1, 1b1 is extruded in the gas-liquid separator 4 irrespective of the state of the engine 1 at the time of engine restart.

  First, in step S1, the ECU 21 confirms that the ignition is on. In step S2, the control valve 19a is opened. At the same time, counting for 30 seconds is started. Here, the period of 30 seconds is set as a period in which the liquid level in the water jackets 1a1 and 1b1 is in a stable state. If the liquid level in the water jackets 1a1 and 1b1 is stable at an appropriate amount, the liquid refrigerant is prevented from being pushed into the gas-liquid separator 4.

  After the count is started in step S3, it is determined in step S4 whether a 30-second period has elapsed. After the 30-second period has elapsed and it is determined YES in step S4, the process proceeds to step S5. In step S5, it is determined whether or not the refrigerant temperature acquired from the water temperature sensor 20 is higher than 80 ° C. Thereby, it is determined whether or not the engine 1 has been warmed up. When the warm-up of the engine 1 is completed and YES is determined in step S5, the process proceeds to step S6.

  In step S6, the liquid level control of the gas-liquid separator 4 is started. After step S6, control for cooling the engine 1 and efficient waste heat recovery is performed. Specifically, drive control of the second water pump 17 is performed based on information acquired from the liquid level sensor 15. Thereby, cooling of the engine 1 and efficient waste heat recovery are performed.

  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.

DESCRIPTION OF SYMBOLS 1 ... Engine 2 ... Exhaust pipe 3 ... Steam passage 3a1 ... Steam discharge pipe 4 ... Gas-liquid separator 5 ... Refrigerant circuit 6 ... 1st water pump (W / P)
7 ... liquefied refrigerant passage 8 ... superheater 8a ... evaporation portion 8b ... superheat portion 9 ... nozzle 10 ... expander 10a ... turbine case 10b ... turbine blade 11 ... steam discharge passage 12 ... condenser 13 ... fan 14 ... condensate water tank 15 ... Liquid level sensor 16 ... first liquefied refrigerant passage 17 ... second water pump (W / P)
18 ... One valve 19 ... Second liquefied refrigerant passage 19a ... Control valve 20 ... Water temperature sensor 21 ... ECU
100 ... Rankine cycle system

Claims (1)

An engine in which a water jacket is formed and is cooled by boiling the refrigerant circulating in the water jacket;
A gas-liquid separator that communicates with the water jacket and separates the refrigerant supplied from the water jacket into vapor and liquefied refrigerant that are vaporized refrigerant;
A superheater to which steam separated in the gas-liquid separator is supplied;
An expander driven by steam supplied from the superheater to recover energy;
A condenser that condenses the vapor that has passed through the expander to generate a liquefied refrigerant;
A condensed water tank for storing the liquefied refrigerant generated in the capacitor;
A first liquefied refrigerant passage that includes a water pump and supplies the liquefied refrigerant in the condensed water tank to the water jacket or the gas-liquid separator;
A second liquefied refrigerant passage that includes a control valve and connects the condensed water tank and the water jacket or the gas-liquid separator;
A control unit that opens the control valve for a predetermined period from when the engine is stopped to when it is restarted;
A Rankine cycle system characterized by having

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