U.S. patent application number 13/636246 was filed with the patent office on 2013-01-10 for rankine cycle system.
This patent application is currently assigned to TOYOTA JIDOSHA KABUSHIKI KAISHA. Invention is credited to Masahide Ishikawa, Hideo Kobayashi, Toshihisa Sugiyama, Kenichi Yamada.
Application Number | 20130008165 13/636246 |
Document ID | / |
Family ID | 44672591 |
Filed Date | 2013-01-10 |
United States Patent
Application |
20130008165 |
Kind Code |
A1 |
Yamada; Kenichi ; et
al. |
January 10, 2013 |
RANKINE CYCLE SYSTEM
Abstract
A Rankine cycle system includes: a superheater, an expander
including a first outlet discharging steam and a second outlet
discharging liquid refrigerant produced therein; a first discharge
path discharging the steam from the expander; a condenser
condensing the steam introduced through the first discharge path
into liquid refrigerant, a condensed water tank reserving the
liquid refrigerant produced in the condenser; and a second
discharge path discharging the liquid refrigerant from the expander
to the condensed water tank, wherein a liquid level in the
condensed water tank satisfies a following relation:
.DELTA.h>.DELTA.Pto/.rho.g, when .DELTA.h means a height
difference between the liquid level and a lowest liquid level in
the second discharge path, .DELTA.Pto means a pressure loss when
the steam flows into the condenser from the expander through the
first discharge path, .rho. means a density of the liquid
refrigerant, and g means a gravitational acceleration.
Inventors: |
Yamada; Kenichi; (Yaizu-shi,
JP) ; Kobayashi; Hideo; (Mishima-shi, JP) ;
Ishikawa; Masahide; (Okazaki-shi, JP) ; Sugiyama;
Toshihisa; (Gotenba-shi, JP) |
Assignee: |
TOYOTA JIDOSHA KABUSHIKI
KAISHA
Toyota-shi, Aichi-ken
JP
|
Family ID: |
44672591 |
Appl. No.: |
13/636246 |
Filed: |
March 25, 2010 |
PCT Filed: |
March 25, 2010 |
PCT NO: |
PCT/JP2010/055229 |
371 Date: |
September 20, 2012 |
Current U.S.
Class: |
60/671 |
Current CPC
Class: |
F01K 25/10 20130101;
F01K 9/00 20130101; F01K 23/065 20130101 |
Class at
Publication: |
60/671 |
International
Class: |
F01K 13/00 20060101
F01K013/00 |
Claims
1. A Rankine cycle system comprising: a superheater, an expander
that is driven by steam, which is vaporized refrigerant supplied
from the superheater, to recover energy, and includes a first
outlet discharging steam and a second outlet discharging liquid
refrigerant produced by condensation of the steam in the expander;
a first discharge path that is connected to the first outlet and
discharges the steam from the expander; a condenser into which the
steam is introduced through the first discharge path, and that
condenses the steam into liquid refrigerant, a condensed water tank
that reserves the liquid refrigerant produced in the condenser; and
a second discharge path that connects the second outlet to the
condensed water tank and discharges the liquid refrigerant from the
expander, wherein a liquid level in the condensed water tank
satisfies a following relation: .DELTA.h>.DELTA.Pto/.rho.g, when
a height difference between the liquid level and a lowest liquid
level in the second discharge path is expressed by .DELTA.h, a
pressure loss when the steam flows into the condenser from the
expander through the first discharge path is expressed by
.DELTA.Pto, a density of the liquid refrigerant is expressed by
.rho., and a gravitational acceleration is expressed by g.
2. The Rankine cycle system according to claim 1, wherein the
second outlet is provided to a downside portion of the
expander.
3. (canceled)
4. The Rankine cycle system according to claim 1, wherein a
connected position of the second discharge path to the condensed
water tank is located higher than the lowest liquid level in the
second discharge path.
5. The Rankine cycle system according to claim 1, wherein a
diameter of the second outlet is smaller than a diameter of the
first outlet.
6. The Rankine cycle system according to claim 1, wherein a flow
passage area of the second discharge path is smaller than a flow
passage area of the first discharge path.
Description
TECHNICAL FIELD
[0001] The present invention relates to a Rankine cycle system.
BACKGROUND ART
[0002] There has been conventionally known a Rankine cycle that
recovers exhaust heat generated due to operation of an
internal-combustion engine. An exemplary Rankine cycle makes a
water-cooled cooling system of an engine have a sealed structure to
carry out the ebullient cooling, drives an expander such as a steam
turbine by refrigerant vaporized by exhaust heat of the engine,
i.e. steam, and recovers exhaust heat by converting thermal energy
included in the steam into electrical energy, for example. Patent
Document 1 is one example that improves the above-described Rankine
cycle system.
PRIOR ART DOCUMENT
Patent Document
[0003] [Patent Document 1] Japanese Patent Application Publication
No. 2009-103060
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0004] However, a following inconvenience may occur at a time of
cold start of an internal-combustion engine by adopting an approach
of Patent Document 1, for example. A temperature of an expander is
generally low when the internal-combustion engine is cold. If steam
is supplied to the expander in a low temperature state, the steam
is condensed in the expander, and goes back to liquid refrigerant.
The liquid refrigerant produced in the expander is retained in the
expander, becomes a resistance against the drive of the expander,
and may cause deterioration or damage of the expander. When a
Rankine cycle system is implemented to a vehicle, it is necessary
to solve the problem of deterioration or damage of the expander
described above because the expander frequently becomes in a cold
state. It is considered to provide a control valve that controls
inflow of steam into the expander while the internal-combustion
engine is warmed up, in order to suppress the deterioration and
damage of the expander. However, the above-described control needs
an actuator that actuates the control valve, and a temperature
sensor to set a control timing or a development of a logic to
estimate the temperature, and thus increases cost.
[0005] Therefore, a problem to be solved by a Rankine cycle system
disclosed in the present specification is to suppress deterioration
and damage of an expander caused by production of liquid
refrigerant in the expander such as a steam turbine.
Means for Solving the Problems
[0006] To solve the above-described problem, a Rankine cycle system
disclosed in the present specification is characterized by
including: a superheater, an expander that is driven by steam,
which is vaporized refrigerant supplied from the superheater, to
recover energy, and includes a first outlet discharging steam and a
second outlet discharging liquid refrigerant produced by
condensation of the steam in the expander; a first discharge path
that is connected to the first outlet and discharges the steam from
the expander; a condenser into which the steam is introduced
through the first discharge path, and that condenses the steam into
liquid refrigerant, a condensed water tank that reserves the liquid
refrigerant produced in the condenser; and a second discharge path
that connects the second outlet to the condensed water tank and
discharges the liquid refrigerant from the expander.
[0007] The expander has the second outlet, and thus is able to
discharge the liquid refrigerant produced 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 drive load of the expander. As a result, the deterioration
and damage of the expander can be suppressed.
[0008] It is desirable that the second outlet is provided to a
downside portion of the expander. It is for discharging the liquid
refrigerant efficiently regardless of an inner shape of the
expander and the like. Generally, the liquid refrigerant can be
discharged by providing the second outlet to the downside portion
of the expander.
[0009] It is desirable that a liquid level in the condensed water
tank satisfies a following relation: .DELTA.h>.DELTA.Pto/.rho.g,
when a difference between the liquid level and a lowest liquid
level in the second discharge path is expressed by .DELTA.h, a
pressure loss when the steam flows into the condenser from the
expander through the first discharge path is expressed by
.DELTA.Pto, a density of the liquid refrigerant is expressed by
.rho., and a gravitational acceleration is expressed by g.
[0010] If the liquid level in the condensed water tank is
maintained so as to satisfy the above-described relation, it is
possible to prevent the steam from flowing through the second
outlet.
[0011] A connected position of the second discharge path to the
condensed water tank may be located higher than the lowest liquid
level in the second discharge path. For example, when the second
discharge path is formed of a U-tube, the second discharge path is
a U-shaped portion of the U-tube, and .DELTA.h can be set large. If
.DELTA.h is set large, it is possible to prevent the steam from
flowing through the second outlet effectively.
[0012] Furthermore, a diameter of the second outlet may be smaller
than a diameter of the first outlet. It is possible to prevent the
steam from flowing through the second outlet effectively by setting
a relation between the diameter of the first outlet and the
diameter of the second outlet so as to satisfy the above-described
relation. In addition, if the diameter of the first outlet becomes
large, the pressure loss .DELTA.Pto can be reduced, and this is
effective for preventing the steam from flowing through the second
outlet.
[0013] In addition, it is desirable that a flow passage area of the
second discharge path is smaller than a flow passage area of the
first discharge path. For example, the relation expressed by the
above equation can be achieved by making an inside diameter of a
pipe forming the second discharge path smaller than an inside
diameter of a pipe forming the first discharge path. It is possible
to prevent the steam from flowing through the second outlet by
making a relation between the flow passage area of the second
discharge path and the flow passage area of the first discharge
path satisfy the above-described relation. In addition, if the flow
passage area of the first discharge path becomes large, the
pressure loss .DELTA.Pto can be reduced, and this is effective for
preventing the steam from flowing through the second outlet.
Effects of the Invention
[0014] According to the Rankine cycle system disclosed in the
present specification, it is possible to suppress deterioration and
damage of an expander caused by production of liquid refrigerant in
the expander.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] FIG. 1 is a schematic configuration diagram of a Rankine
cycle system of an embodiment;
[0016] FIG. 2 is an explanatory diagram enlarging a part A in FIG.
1; and
[0017] FIG. 3 is an explanatory diagram illustrating another shape
of a second discharge path.
MODES FOR CARRYING OUT THE INVENTION
[0018] Hereinafter, a description will be given of modes for
carrying out the present invention in detail with reference to
drawings.
Embodiment
[0019] A description will be given of an outline structure of a
Rankine cycle system 100 with reference to FIG. 1 and FIG. 2. FIG.
1 is a schematic configuration diagram of the Rankine cycle system
100. FIG. 2 is an explanatory diagram enlarging a part A in FIG. 1.
The Rankine cycle system 100 has an engine 1 that is cooled by
boiling of refrigerant therein. The engine 1 is an example of an
internal-combustion engine corresponding to a steam generator. 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 is cooled by boiling of the refrigerant in
the water jacket. The engine 1 produces steam at this time. The
engine 1 further includes an exhaust pipe 2. One end of a steam
pathway 3 is connected to the cylinder head 1b of the engine 1.
[0020] A gas-liquid separator 4 is arranged in the steam pathway 3.
The gas-liquid separator 4 separates the refrigerant, which is in a
gas-liquid coexistence state and flows into the gas-liquid
separator 4 from the engine 1 side, into a gas phase (steam) and a
liquid phase (liquid refrigerant). One end of a refrigerant
circulating path 5 is connected to a bottom end portion of the
gas-liquid separator 4. The other end of the refrigerant
circulating path 5 is connected to the cylinder block 1a. In
addition, in the refrigerant circulating path 5, arranged is a
first water pump 6 that pumps the liquid refrigerant into the
engine 1. The first water pump 6 is a so-called mechanical pump,
and uses a crankshaft included in the engine 1 as a drive source.
The first water pump 6 circulates the liquid refrigerant between
the engine 1 and the gas-liquid separator 4.
[0021] A superheater 8 is arranged in the steam pathway 3. The
superheater 8 includes a vaporizing portion 8a at a lower side, and
a superheating portion 8b at an upper side. The exhaust pipe 2 is
led to the superheater 8. Exhaust gas generated in the engine 1
flows through the exhaust pipe 2. The exhaust pipe 2 passes through
the superheater 8 so that the exhaust gas passes through the
superheating portion 8b and the vaporizing portion 8a in this
order. One end of a liquid refrigerant pathway 7 is connected to
the vaporizing portion 8a. The exhaust gas exchanges heat with the
steam passing through the gas-liquid separator 4. The other end of
the liquid refrigerant pathway 7 is connected to the bottom end
portion of the gas-liquid separator 4. An opening/closing valve 7a
is provided to the liquid refrigerant pathway 7. An opened/closed
state of the opening/closing valve 7a determines the supply of the
liquid refrigerant from the gas-liquid separator 4 to the
vaporizing portion 8a. The liquid refrigerant supplied to the
vaporizing portion 8a is vaporized by heat of the exhaust gas that
has superheated the steam at the superheating portion 8b. This
increases a steam generation amount, improves the degree of
superheating of the steam, and improves recovery efficiency of the
exhaust heat. A steam discharge pipe 3a is provided to an upper end
portion of the superheating portion 8b. A nozzle 9 is provided to a
tip end portion of the steam discharge pipe 3a.
[0022] An expander 10 is arranged at a downstream side of the
superheater 8. The expander 10 is driven by vaporized refrigerant,
i.e. steam, supplied from the superheater 8, and recovers energy.
The expander 10 is a steam turbine including a chassis 10a and a
turbine blade 10b located in the chassis 10a. The nozzle 9 is
mounted to the chassis 10a so that the steam supplied through the
steam pathway 3 is injected toward the turbine blade 10b. Thus, the
turbine blade 10b is rotary driven by the steam supplied through
the steam pathway 3. The rotative force of the turbine blade 10b
assists the rotation of the crankshaft included in the engine 1,
and drives a power generator. This recovers the exhaust heat.
[0023] The chassis 10a of the expander 10 is provided with a first
outlet 10a1 that discharges the steam, and a second outlet 10a2
that discharges the liquid refrigerant produced by condensation of
the steam in the chassis 10a. Here, the second outlet 10a2 is
provided to a downside portion of the chassis 10a of the expander
10 so as to discharge the liquid refrigerant in the chassis 10a of
the expander 10. A diameter D2 of the second outlet 10a2 is smaller
than a diameter D1 of the first outlet 10a1. That is to say, a
relation of D2<D1 is established.
[0024] One end of a first discharge path 11 is connected to the
first outlet 10a1. The other end of the first discharge path 11 is
connected to a condenser 12. The first discharge path 11 discharges
the steam from the expander 10, and introduces the discharged steam
into the condenser 12. The condenser 12 condenses the steam by
cooling the steam, and produces the liquid refrigerant. The
condenser 12 receives blast by a fan 13 and can cool and condense
the steam efficiently. Arranged under the condenser 12 is a
condensed water tank 14 that reserves the liquid refrigerant
produced in the condenser 12.
[0025] One end of a second discharge path 15 is connected to the
second outlet 10a2. The other end of the second discharge path 15
is connected to the condensed water tank 14. The above-described
second discharge path 15 discharges the liquid refrigerant from the
expander 10 to the condensed water tank 14. The liquid refrigerant
that has been cooled in the condenser 12 is reserved in the
condensed water tank 14. The liquid refrigerant condensed in the
expander 10 is mixed with the liquid refrigerant cooled in the
condenser 12 and its temperature is decreased by being discharged
to the condensed water tank 14. A flow passage area S2 of the
second discharge path 15 is smaller than a flow passage area S1 of
the first discharge path 11. That is to say, a relation of S2<S1
is established.
[0026] At a downstream side of the condensed water tank 14,
provided is a refrigerant recovery passage 16 that re-circulates
the liquid refrigerant, which is temporarily reserved in the
condensed water tank 14, to the engine 1 side. The refrigerant
recovery passage 16 is connected to the upstream side of the first
water pump 6 in the refrigerant circulating path 5. A second water
pump 17 is arranged in the refrigerant recovery passage 16. The
second water pump 17 is an electric vane pump. When the second
water pump 17 is in an operational state, the liquid refrigerant in
the condensed water tank 14 is supplied to the refrigerant
circulating path 5. In addition, a unidirectional valve 18 that
prevents reverse flow of the refrigerant is provided downstream of
the second water pump 17. As described above, the Rankine cycle
system 100 includes a passage where the refrigerant is
circulated.
[0027] The relation of D2<D1 is established between the diameter
D1 of the first outlet 10a1 included in the Rankine cycle system
100 and the diameter D2 of the second outlet 10a2 as described
previously. In addition, the relation of S2<S1 is established
between the flow passage area S1 of the first discharge path 11
included in the Rankine cycle system 100 and the flow passage area
S2 of the second discharge path 15. Maintaining the above relations
is effective for preventing the steam from passing through the
second outlet 10a2. In the Rankine cycle system 100, it is
desirable that the steam supplied into the expander 10 is
discharged from the first outlet 10a1 as much as possible. If the
steam, which is vaporized refrigerant not condensed, is discharged
from the second outlet 10a2, the steam passes through the second
discharge path 15 and the condensed water tank 14, and flows into
the condenser 12. That is to say, the steam flows from a direction
different from a designed inflow direction into the condenser 12.
If the steam flows into the condenser 12 from the direction
different from the designed direction as described above, the
function of the condenser 12 is impaired. That is to say, the
condenser 12 cools and condenses the steam by heat exchange before
the steam which has been introduced from the upper side thereof
reaches the condensed water tank 14, and produces the liquid
refrigerant. If high-temperature steam flows from the condensed
water tank 14 side, the function of the condenser 12 is impaired.
Moreover, the temperature of the liquid refrigerant in the
condensed water tank 14 rises. The liquid refrigerant in the
condensed water tank 14 is supplied to the engine 1 again, and used
for cooling the engine 1. Thus, it is required to keep the
temperature of the liquid refrigerant in the condensed water tank
14 as low as possible.
[0028] The Rankine cycle system 100 satisfies a relation expressed
by a following equation (1) in order to prevent the steam from
being discharged from the second outlet 10a2.
.DELTA.h>.DELTA.Pto/.rho.g equation (1)
.DELTA.h: difference between a liquid level in the condensed water
tank 14 and a lowest liquid level in the second discharge path 15
.DELTA.Pto: pressure loss when the steam flows in the condenser 12
from the expander 10 through the first discharge path 11 .rho.:
density of the liquid refrigerant g: gravitational acceleration
[0029] Here, .DELTA.h in the present embodiment is equal to
.DELTA.h1 as illustrated in FIG. 1 and FIG. 2. In addition
.DELTA.Pto in the present embodiment is a pressure loss within a
range indicated by B in FIG. 1 and FIG. 2.
[0030] It is possible to prevent the steam from being discharged
from the second outlet 10a2 by satisfying the relation expressed by
the equation (1). To satisfy the relation of the equation (1), it
is effective to make the value of .DELTA.h as large as possible,
and the value of .DELTA.Pto as small as possible. It is possible to
make the value of .DELTA.Pto small by setting the diameter D1 of
the first outlet 10a1 large or setting the flow passage area S1 of
the first discharge path 11 large.
[0031] On the other hand, the second discharge path 15 may be
replaced with a second discharge path 151 illustrated in FIG. 3 in
order to set .DELTA.h large. As illustrated in FIG. 3, a connected
position P1 of the second discharge path 151 to the condensed water
tank 14 is located higher than a lowest liquid level 151a in the
second discharge path 151. The lowest liquid level 151a is lowered
by making the second discharge path 151 have a U-shape. This
secures .DELTA.h2. As apparent from FIG. 3, .DELTA.h2 is larger
than .DELTA.h1 when the second discharge path 15 is used. As a
result, .DELTA.h2 easily satisfies the condition of the equation
(1).
[0032] As described above, according to the Rankine cycle system
disclosed in the present specification, it is possible to discharge
the liquid refrigerant produced in the expander 10 efficiently. As
a result, it is possible to suppress deterioration and damage of
the expander caused by production of the liquid refrigerant in the
expander 10. At this time, a special control device for discharging
the liquid refrigerant from the expander 10 is not necessary, and
there is an advantage in cost.
[0033] The above described embodiments are merely examples for
carrying out the present invention, and the present invention is
not limited to the above-mentioned embodiments, and it is apparent
from the above descriptions that other embodiments, variations and
modifications may be made without departing from the scope of the
present invention.
DESCRIPTION OF LETTERS OR NUMERALS
[0034] 1 . . . engine [0035] 2 . . . exhaust pipe [0036] 3 . . .
steam pathway [0037] 3a1 . . . steam discharge pipe [0038] 4 . . .
gas-liquid separator [0039] 5 . . . refrigerant circulating path
[0040] 6 . . . first water pump (W/P) [0041] 7 . . . liquid
refrigerant pathway [0042] 8 . . . superheater [0043] 8a . . .
vaporizing portion [0044] 8b . . . superheating portion [0045] 9 .
. . nozzle [0046] 10 . . . expander [0047] 10a . . . turbine
chassis [0048] 10b . . . turbine blade [0049] 11 . . . first
discharge path [0050] 12 . . . condenser [0051] 13 . . . fan [0052]
14 . . . condensed water tank [0053] 15, 151 . . . second discharge
path [0054] 16 . . . refrigerant recovery passage [0055] 17 . . .
second water pump (W/P) [0056] 18 . . . unidirectional valve [0057]
100 . . . Rankine cycle system
* * * * *