DE112010005419B4 - Rankine cycle system - Google Patents

Abstract

Rankine cycle system (100), comprising: a super heater (8), an expander (10) driven by steam, which is evaporated refrigerant supplied from the super heater (8), to restore energy, and which includes a first outlet (10a1) that discharges steam and a second outlet (10a2) that discharges liquid refrigerant generated by condensation of the steam in the expander (10); a first outlet path (11), connected to the first outlet (10a1) and discharging the steam from the expander (10); a condenser (12) into which the steam is introduced through the first outlet path (11) and which condenses the steam into liquid refrigerant, a condensing refrigerant tank (14) that stores the liquid refrigerant generated in the condenser (12); anda second outlet path (15) connecting the second outlet (10a2) to the condensing refrigerant tank (14) and discharging the liquid refrigerant from the expander (10); where a liquid level in the condensing refrigerant tank (14) satisfies Δh> ΔPto / ρg, a difference between the liquid level and a lowest liquid level in the second outlet path (15) is expressed by Δh, a pressure loss when the steam from the expander (10) flows through the first outlet path (11) into the condenser (12), is expressed by ΔPto, a density of the liquid refrigerant is expressed by ρ, and a gravitational acceleration is expressed by g.

Description

TECHNICAL AREA

The present invention relates to a Rankine cycle system (Clausius-Rankine cycle system).

STATE OF THE ART

A Rankine cycle is conventionally known that uses exhaust gas that is generated due to an operation of an internal combustion engine for recovery. An exemplary Rankine cycle process causes a water-cooled cooling system of an internal combustion engine, which has a sealed structure, to perform ebullient cooling, an expander, such as a steam turbine, using a refrigerant that is vaporized by exhaust gas from the internal combustion engine, ie, drives steam and exhaust gas through Converting thermal energy contained in the steam into electrical energy used for recovery. The JP 2009 - 103 060 A. shows an example that improves the Rankine cycle system described above. That is, the JP 2009 - 103 060 A. discloses a Rankine cycle system comprising: a superheater; a turbine that is powered by steam that is evaporated refrigerant that is supplied from the superheater to restore energy and that includes a first outlet that discharges steam; a first outlet path connected to the first outlet and exhausting steam from an expander; a condenser into which steam is introduced through the first outlet path and which condenses the steam into a liquid refrigerant; and a condensing refrigerant tank that stores the liquid refrigerant generated in the condenser.

The also describes US 4,471,621 A a method and an apparatus for discharging a liquid working fluid from the pit of a container of a power plant. The liquid in the pit is gravity-fed into a steam boiler that heats the liquid and generates steam at the same pressure as that of a condenser. The resulting steam is passed directly to the condenser where it condenses and combines with a main condensate generated from steam discharged from a turbine.

The US 3,685,292 A describes a system and method for determining whether an exhaust line is blocked for discharging condensate from a turbine housing into a condenser and for cleaning the line if it is blocked.

SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

However, the following problem may occur at the time of an engine cold start when the approach of FIG JP 2009 - 103 060 A. is used. The temperature of the expander is generally low when the engine is cold. When steam is supplied to the expander at a low temperature, the steam in the expander condenses and is returned to a liquid refrigerant. The liquid refrigerant generated in the expander is held in the expander, becomes a resistance to the drive of the expander, and can cause deterioration or damage to the expander. When a Rankine cycle system is installed in a vehicle, it is necessary to solve the problem of deterioration or damage to the expander described above because the expander often gets cold. It is contemplated to provide a control valve that controls the flow of steam into the expander while the engine is warming up to suppress deterioration and damage to the expander. However, the control described above requires an actuator that operates the control valve, a temperature sensor for setting a control timing, or the development of logic for estimating the temperature, which increases the costs.

Therefore, the object to be achieved by the Rankine cycle system described in the present specification is to avoid deterioration and damage to an expander caused by the generation of a liquid refrigerant in the expander such as a steam turbine.

MEANS TO SOLVE THE PROBLEMS

To solve the problem described above, a Rankine cycle system described in the present specification is characterized in that it includes: a superheater; an expander driven by steam, which is evaporated refrigerant supplied by the superheater to restore energy, and which has a first outlet that discharges steam and a second outlet, the liquid refrigerant that is produced by condensation of the vapor in the expander is created, omits, contains; a first outlet path connected to the first outlet and discharging the steam from the expander; a condenser (steam condenser) into which the steam is introduced through the first outlet path and which condenses the steam into a liquid refrigerant; a condensing refrigerant tank that holds the liquid refrigerant that is generated in the condenser, stores; and a second outlet path that connects the second outlet to the condensing refrigerant tank and discharges the liquid refrigerant from the expander.

The expander has a second outlet and is therefore able to discharge the liquid refrigerant that is generated by condensation in the expander when the expander is in a cold state. If the liquid refrigerant can be discharged from the expander, it is possible to reduce a driving load on the expander. As a result, deterioration and damage to the expander can be avoided.

It is desirable that the second outlet be provided on a downstream portion of the expander. This serves to efficiently discharge the liquid refrigerant regardless of an internal shape of the expander and the like. Generally, the liquid refrigerant can be discharged by providing the second outlet on the downstream portion of the expander.

It is desirable that a liquid level in the condensing refrigerant tank satisfies the following relationship Δh> ΔPto / ρg, where a height difference between the liquid level and a lowest liquid level in the second outlet path is expressed by Δh, a pressure loss when the steam from the expander passes through the first outlet path flows into the condenser, is expressed by ΔPto, a density of the liquid refrigerant is expressed by ρ, and a gravitational acceleration is expressed by g.

If the liquid level in the condensing refrigerant tank is maintained such that the relationship described above is satisfied, it is possible to prevent the vapor from flowing through the second outlet.

A connection position of the second outlet path with the condensing refrigerant tank may be arranged higher than the lowest liquid level in the second outlet path. For example, if the second outlet path is formed from a U-tube, the second outlet path is a U-shaped portion of the U-tube, and Δh may be large. If Δh is large, it is possible to effectively prevent the steam from flowing through the second outlet.

In addition, a diameter of the second outlet can be smaller than a diameter of the first outlet. It is possible to effectively prevent the steam from flowing through the second outlet by setting a relationship between the diameter of the first outlet and the diameter of the second outlet such that the relationship described above is satisfied. In addition, when the diameter of the first outlet becomes large, the pressure loss ΔPto can be reduced, and this effectively prevents the steam from flowing through the second outlet.

In addition, it is desirable that a flow passage area of the second outlet path is smaller than a flow passage area of the first outlet path. The relationship expressed by the above equation can be achieved, for example, by making an inner diameter of a pipe that forms the second outlet path smaller than an inner diameter of a pipe that forms the first outlet path. It is possible to prevent the steam from flowing through the second outlet by causing a relationship between the flow passage area of the second outlet path and the flow passage area of the first outlet path to satisfy the relationship described above. In addition, when the flow passage area of the first outlet path becomes large, the pressure loss ΔPto can be reduced, and this effectively prevents steam from flowing through the second outlet.

EFFECTS OF THE INVENTION

According to the Rankine cycle system described in the present specification, it is possible to prevent deterioration and damage to an expander caused by the generation of liquid refrigerant in the expander.

Figure list

• 1 FIG. 12 is a schematic configuration diagram of a Rankine cycle system of an embodiment;
• 2nd is a diagram that is part A of the 1 represents enlarged; and
• 3rd FIG. 12 is a diagram illustrating another shape of a second exhaust path.

MODES FOR CARRYING OUT THE INVENTION

Modes for carrying out the present invention will now be described in more detail with reference to the drawings.

Embodiment

The following is a description of an outline of a Rankine cycle system 100 regarding 1 and 2nd . 1 is a schematic configuration diagram of the Rankine cycle Systems 100 . 2nd is a diagram that is part A of the 1 represents enlarged. The Rankine cycle system 100 has an internal combustion engine 1 which is cooled by boiling the refrigerant inside. The internal combustion engine 1 is an example of an internal combustion engine that corresponds to a steam generator. The internal combustion engine 1 contains a cylinder block 1a and a cylinder head 1b . A water jacket is in the cylinder block 1a and the cylinder head 1b trained, and the internal combustion engine 1 is cooled by boiling the refrigerant in the water jacket. The internal combustion engine 1 generates steam at this time. The internal combustion engine 1 also contains an exhaust pipe 2nd . An end to a steam path 3rd is with the cylinder head 1b of the internal combustion engine 1 connected.

A gas-liquid separator 4th is in the steam path 3rd arranged. The gas-liquid separator 4th separates the refrigerant, which is in a gas-liquid coexistence state, from the side of the internal combustion engine 1 out in the gas-liquid separator 4th flows into a gas phase (vapor) and a liquid phase (liquid refrigerant). One end of a refrigerant circulation path 5 is with a bottom end portion of the gas-liquid separator 4th connected. The other end of the refrigerant circulation path 5 is with the cylinder block 1a connected. It is also in the refrigerant circulation path 5 a first pump 6 arranged the liquid refrigerant in the internal combustion engine 1 pumps. The first pump 6 is a so-called mechanical pump and uses a crankshaft in the internal combustion engine 1 is included as a drive source. The first pump 6 leaves the liquid refrigerant between the internal combustion engine 1 and the gas-liquid separator 4th circling.

An overheater 8th is in the steam path 3rd arranged. The superheater 8th contains an evaporation section 8a on a lower side and an overheating section 8b on an upper side. The exhaust pipe 2nd is in the superheater 8th guided. Exhaust gas that is in the internal combustion engine 1 generated, flows through the exhaust pipe 2nd . The exhaust pipe 2nd runs through the superheater 8th so that the exhaust gas through the overheating section 8b and the evaporation section 8a flows in that order. One end of a liquid refrigerant path 7 is with the evaporation section 8a connected. The exhaust gas exchanges heat with the steam through the gas-liquid separator 4th flows from. The other end of the liquid refrigerant path 7 is with the bottom end portion of the gas-liquid separator 4th connected. An opening / closing valve 7a is on the liquid refrigerant path 7 intended. An opening / closing state of the opening / closing valve 7a determines the supply of the liquid refrigerant from the gas-liquid separator 4th to the evaporation section 8a . The liquid refrigerant that the evaporation section 8a is evaporated by means of heat of the exhaust gas, which is the steam at the superheating section 8b overheated. This increases an amount of steam generation, improves the degree of superheating of the steam, and improves the recovery efficiency of the exhaust gas. A steam outlet pipe 3a is at an upper end portion of the overheating portion 8b intended. A nozzle 9 is at a tip end portion of the steam outlet pipe 3a intended.

An expander 10th is on a downstream side of the superheater 8th arranged. The expander 10th is caused by evaporated refrigerant, ie steam coming from the superheater 8th is fed, driven and restores energy. The expander 10th is a steam turbine which is a casing 10a and a turbine blade 10b that in the housing 10a is arranged. The nozzle 9 is on the case 10a mounted so that the steam flowing through the steam path 3rd is fed in the direction of the turbine blade 10b is injected. Thus the turbine blade 10b through the steam, through the steam path 3rd is fed, rotated. The torque of the turbine blade 10b supports the rotation of the crankshaft in the internal combustion engine 1 is contained, and drives an energy generator. This restores the energy of the exhaust gas.

The housing 10a of the expander 10th is with a first outlet 10a1 which releases the steam and a second outlet 10a2 which is the liquid refrigerant caused by condensation of the vapor in the housing 10a is generated, omitted, provided. Here is the second outlet 10a2 on a downstream section of the housing 10a of the expander 10th provided to the liquid refrigerant in the housing 10a of the expander 10th omit. A diameter D2 of the second outlet 10a2 is smaller than a diameter D1 of the first outlet 10a1 . That is, the relationship D2 <D1 applies.

An end to a first outlet path 11 is with the first outlet 10a1 connected. The other end of the first outlet path 11 is with a capacitor 12th connected. The first outlet path 11 releases the steam from the expander 10th and discharges the released steam into the condenser 12th a. The condenser 12th condenses the steam by cooling the steam and generates the liquid refrigerant. The condenser 12th receives wind from a fan 13 and can efficiently cool and condense the steam. Under the condenser 12th is a condensing refrigerant tank 14 arranged of the liquid refrigerant in the condenser 12th is generated, stores.

One end of a second outlet path 15 is with the second outlet 10a2 connected. The other end of the second outlet path 15 is with the condensing refrigerant tank 14 connected. The second outlet path described above 15 releases the liquid refrigerant from the expander 10th to the condensing refrigerant tank 14 out. The liquid refrigerant that is in the condenser 12th has been cooled is in the condensing refrigerant tank 14 saved. The liquid refrigerant in the expander 10th is condensed with the liquid refrigerant that is in the condenser 12th is cooled, mixed, and its temperature is discharged to the condensing refrigerant tank 14 decreased. A flow passage area S2 of the second outlet path 15 is smaller than a flow passage area S1 the first outlet path 11 . That is, the relationship S2 <S1 applies.

On a downstream side of the condensing refrigerant tank 14 is a refrigerant recovery passage 16 provided the the liquid refrigerant that is temporarily in the condensing refrigerant tank 14 is stored to the side of the internal combustion engine 1 leads back. The refrigerant recovery passage 16 is with the upstream side of the first pump 6 in the refrigerant circulation path 5 connected. A second pump 17th is in the refrigerant recovery passage 16 arranged. The second pump 17th is an electric vane pump. If the second pump 17th is operated, the liquid refrigerant is in the condensing refrigerant tank 14 the refrigerant circulation path 5 fed. There is also a unidirectional valve 18th that prevents reverse flow of the refrigerant downstream of the second pump 17th intended. As described above, the Rankine cycle system includes 100 a passage in which the refrigerant circulates.

The relationship D2 <D1 becomes between the diameter D1 of the first outlet 10a1 that in the Rankine cycle system 100 is included, and the diameter D2 of the second outlet 10a2 set up as previously described. In addition, the relationship S2 <S1 between the flow passage area S1 the first outlet path 11 that in the Rankine cycle system 100 is included, and the flow passage area S2 of the second outlet path 15 set up. Maintaining the above relationships effectively prevents steam from passing through the second outlet 10a2 flows. In the Rankine cycle system 100 it is desirable that the steam that the expander 10th is fed as far as possible from the first outlet 10a is left out. When the vapor, which is non-condensed evaporated refrigerant, from the second outlet 10a2 the steam flows through the second outlet path 15 and the condensing refrigerant tank 14 and in the capacitor 12th . That is, the steam flows in a direction that is from an intended flow direction into the condenser 12th differs. If the steam from the other direction, which differs from the intended direction as described above, into the condenser 12th flows, the function of the capacitor 12th impaired. That is, the capacitor 12th cools and condenses the steam by heat exchange before the steam introduced from the top side condenses the condensing refrigerant tank 14 reached, and generates the liquid refrigerant. When a high temperature steam from the side of the condensing refrigerant tank 14 flows out, the function of the capacitor 12th impaired. In addition, the temperature of the liquid refrigerant in the condensing refrigerant tank rises 14 on. The liquid refrigerant in the condensing refrigerant tank 14 becomes the internal combustion engine again 1 fed and for cooling the internal combustion engine 1 used. That is, it is necessary to check the temperature of the liquid refrigerant in the condensing refrigerant tank 14 to keep as low as possible.

mit

• Δh: Höhendifferenz zwischen einem Flüssigkeitspegel in dem Kondensationskältemitteltank 14 und einem niedrigsten Flüssigkeitspegel in dem zweiten Auslasspfad 15,
• ΔPto: Druckverlust, wenn der Dampf von dem Expander 10 durch den ersten Auslasspfad 11 in den Kondensator 12 fließt,
• p: Dichte des flüssigen Kältemittels, und
• g: Gravitationsbeschleunigung.

The Rankine cycle system 100 meets the following equation (1) to prevent the steam from the second outlet 10a2 is left out. $$\Delta \text{H}>\Delta \text{Pto /}\mathrm{\rho }\text{G}$$

With

• Δh: height difference between a liquid level in the condensing refrigerant tank 14 and a lowest liquid level in the second outlet path 15 ,
• ΔPto: pressure loss when the steam comes from the expander 10th through the first outlet path 11 in the capacitor 12th flows,
• p: density of the liquid refrigerant, and
• g: gravitational acceleration.

Here, according to the present embodiment, Δh is equal to Δh1 as shown in FIG 1 and 2nd is shown. In addition, according to the present embodiment, ΔPto is a pressure loss within a range defined by B in 1 and 2nd is specified.

It is possible to prevent the steam from the second outlet by satisfying the relationship of the above equation (1) 10a2 is left out. In order to satisfy the above equation (1), the value of Δh should be as large as possible and the value of ΔPto as small as possible. It is by setting the diameter D1 of the first outlet 10a1 on large and setting the flow passage area S1 the first outlet path 11 on large possible to cause the value of ΔPto to be small.

On the other hand, the second outlet path 15 through a second outlet path 151 who in 3rd is shown, to be large to form Δh. Like it in 3rd is a connection position P1 of the second outlet path 151 with the condensing refrigerant tank 14 higher than a lowest liquid level 151a in the second outlet path 151 arranged. The lowest liquid level 151a is reduced by the second outlet path 151 has a U-shape. This is guaranteed by Δh2. As it is based on the 3rd it can be seen that Δh2 is greater than Δh1 if the second outlet path 15 is used. Accordingly, Δh2 easily satisfies the condition of the equation (1).

As described above, according to the Rankine cycle system described in the present specification, it is possible to use the liquid refrigerant contained in the expander 10th is omitted efficiently. As a result, it is possible to deteriorate and damage the expander 10th caused by the generation of the liquid refrigerant in the expander 10th caused to avoid. At the same time is a special control device for discharging the liquid refrigerant from the expander 10th not necessary, and this offers a cost advantage.

The above-described embodiments are only examples for carrying out the present invention, and the present invention is not limited to the above-described embodiments. It is apparent from the above description that further embodiments, variations and modifications are possible without departing from the scope of the present invention.

Reference list

1:

Internal combustion engine

2:

Exhaust pipe

3:

Steam path

3a1:

Steam outlet pipe

4:

Gas-liquid separator

5:

Refrigerant circulation path

6:

first pump (W / P)

7:

Liquid refrigerant path

8th:

Superheater

8a:

Evaporation section

8b:

Overheating section

9:

jet

10:

expander

10a:

Turbine casing

10b:

Turbine blade

11:

first outlet path

12:

capacitor

13:

Fan

14:

Condensing refrigerant tank

15, 151:

second outlet path

16:

Refrigerant recovery passage

17:

second pump (W / P)

18:

unidirectional valve

100:

Rankine cycle system

Claims (5)

Rankine cycle system (100), which includes: a superheater (8), an expander (10) driven by steam, which is evaporated refrigerant supplied from the super heater (8), to restore energy, and which has a first outlet (10a1), which discharges steam, and a second outlet ( 10a2) which contains liquid refrigerant generated by condensation of the vapor in the expander (10); a first outlet path (11) connected to the first outlet (10a1) and discharging the steam from the expander (10); a condenser (12) into which the steam is introduced through the first outlet path (11) and which condenses the steam into liquid refrigerant, a condensing refrigerant tank (14) that stores the liquid refrigerant generated in the condenser (12); and a second outlet path (15) connecting the second outlet (10a2) to the condensing refrigerant tank (14) and discharging the liquid refrigerant from the expander (10); in which a liquid level in the condensing refrigerant tank (14) satisfies Δh> ΔPto / ρg, where a difference between the liquid level and a lowest liquid level in the second outlet path (15) is expressed by Δh, a pressure loss when the steam from the expander (10) flows through the first outlet path (11) into the condenser (12) is expressed by ΔPto, a density of the liquid refrigerant is expressed by ρ, and a gravitational acceleration is expressed by g. Rankine cycle system (100) Claim 1 , characterized in that the second Outlet (10a2) is provided on a downstream section of the expander (10). Rankine cycle system (100) Claim 1 or 2nd , characterized in that a connection position of the second outlet path (15) with the condensing refrigerant tank (14) is arranged higher than a lowest liquid level in the second outlet path (15). Rankine cycle system (100) Claim 1 , 2nd or 3rd , characterized in that a diameter of the second outlet (10a2) is smaller than a diameter of the first outlet (10a1). Rankine cycle system (100) Claim 1 , 2nd , 3rd , or 4, characterized in that a flow passage area of the second outlet path (15) is smaller than a flow passage area of the first outlet path (11).

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