Title: Fuel evaporator
Abstract: A fuel evaporator composed of an evaporation chamber which evaporates a raw liquid fuel by a high temperature thermal medium to provide a raw fuel gas is disclosed. The evaporation chamber comprises a plurality of evaporation chambers serially connected to each other in a ventilation manner, and at least one raw liquid fuel injector for injecting the raw liquid fuel being provided on each of said plurality of evaporation chambers.
Patent Number: 6,899,741 Issued on 05/31/2005 to Nakamura, et al.
| Inventors:
|
Nakamura; Masahito (Saitama, JP);
Abe; Naoyuki (Saitama, JP);
Kasahara; Kiyoshi (Saitama, JP);
Tachihara; Takahiro (Saitama, JP)
|
| Assignee:
|
Honda Giken Kogyo Kabushiki Kaisha (Tokyo, JP)
|
| Appl. No.:
|
740994 |
| Filed:
|
December 21, 2000 |
Foreign Application Priority Data
| Dec 21, 1999[JP] | 11-363479 |
| Dec 21, 1999[JP] | 11-363481 |
| Dec 21, 1999[JP] | 11-363482 |
| Current U.S. Class: |
48/61; 48/127.7; 165/115; 261/79.2; 261/155; 422/200; 429/26 |
| Intern'l Class: |
H01M 008/06 |
| Field of Search: |
429/20,26,12
261/155,792
165/115
422/200
48/127.7,61
|
References Cited [Referenced By]
U.S. Patent Documents
| 6536748 | Mar., 2003 | Tachihara et al.
| |
| 6550532 | Apr., 2003 | Nakamura et al.
| |
| 6617067 | Sep., 2003 | Tachihara et al.
| |
| Foreign Patent Documents |
| 1 160 902 | Dec., 2001 | EP.
| |
| 2001/-650424 | Dec., 1999 | JP.
| |
| A-2000-319002 | Nov., 2000 | JP.
| |
| 2002231279 | Aug., 2002 | JP.
| |
Primary Examiner: Bhat; N.
Attorney, Agent or Firm: Arent Fox PLLC
Claims
1. A fuel evaporator composed of an evaporation chamber which evaporates a raw
liquid fuel by a high temperature thermal medium to provide a raw fuel gas,
said evaporation chamber comprising a plurality of evaporation chambers serially
connected to each other in a ventilation manner, and
at least one raw liquid fuel injector for injecting said raw liquid fuel being
provided on each of said plurality of evaporation chambers.
2. The fuel evaporator according to claim 1, wherein a plurality of the raw liquid
injector are provided on any one of said plurality of evaporation chambers.
3. The fuel evaporator according to claim 1, which further comprise a controller
for said raw liquid fuel injector, which, upon receiving a signal for the requirement
of said raw fuel gas, selects the raw liquid fuel injector or injectors from which
the raw liquid fuel is injected.
4. The fuel evaporator according to claim 2, which further comprise a controller
for said raw liquid fuel injector, which, upon receiving a signal for the requirement
of said raw fuel gas, selects the raw liquid fuel injector or injectors from which
the raw liquid fuel is injected.
5. The fuel evaporator according to claim 1, which has a heat receiving portion
for receiving the heat from the heat source, which generates said high temperature
thermal medium, provided near the bottom of one of said evaporation chamber, and
has a slope downward to said heat receiving portion provided on the bottom of another
evaporation chamber or chambers.
6. The fuel evaporator according to claim 2, which has a heat receiving portion
for receiving the heat from the heat source, which generates said high temperature
thermal medium, provided near the bottom of one of said evaporation chamber, and
has a slope downward to said heat receiving portion provided on the bottom of another
evaporation chamber or chambers.
7. The fuel evaporator according to claim 3, which has a heat receiving portion
for receiving the heat from the heat source, which generates said high temperature
thermal medium, provided near the bottom of one of said evaporation chamber, and
has a slope downward to said heat receiving portion provided on the bottom of another
evaporation chamber or chambers.
8. The fuel evaporator according to claim 5, wherein one of said evaporation
chambers is formed so that the thermal conductive area thereof is larger than that
or those of another evaporation chamber or chambers, and said heat receiving portion
is provided on the bottom of said evaporation chamber having a larger thermal conductive area.
9. The fuel evaporator according to claim 6, wherein one of said evaporation
chambers is formed so that the thermal conductive area thereof is larger than that
or those of another evaporation chamber or chambers, and said heat receiving portion
is provided on the bottom of said evaporation chamber having a larger thermal conductive area.
10. The fuel evaporator according to claim 7, wherein one of said evaporation
chamber is formed so that the thermal conductive area thereof is larger than that
or those of another evaporation chamber or chambers, and said evaporation chamber
having a larger thermal conductive area has said heat receiving portion.
11. A fuel evaporator composed of an evaporation chamber which evaporates a raw
liquid fuel by a high temperature thermal medium to provide a raw fuel gas,
said evaporation chamber comprising a plurality of evaporation chambers serially
connected to each other in a ventilation manner,
a chamber for controlling a gas temperature, which controls the temperature of
the raw fuel gas transferred from said evaporation chamber by means of heat-exchange
with said high temperature thermal medium, and
at least one raw liquid fuel injector for injecting said raw liquid fuel being
provided on each of said plurality of evaporation chambers.
12. The fuel evaporator according to claim 11, which further comprises:
at least one thermo sensor, which detects the temperature within any of said
evaporation chambers; and
a controller for said raw liquid fuel injector, which, upon receiving a signal
for the requirement of said raw fuel gas, selects the raw liquid fuel injector
or injectors from which the raw liquid fuel is injected.
13. The fuel evaporator according to claim 11, which further comprises:
a low temperature thermal medium inlet, which mix the high temperature thermal
medium introduced into said chamber for controlling the gas temperature with a
low temperature thermal medium, a low temperature thermal medium passage, and a
valve for supplying said low temperature thermal medium; and
a controller which controls the opening degree of said valve for supplying said
low temperature thermal medium.
14. The fuel evaporator according to claim 12, which further comprises:
a low temperature thermal medium inlet, which mix the high temperature thermal
medium introduced into said chamber for controlling the gas temperature with a
low temperature thermal medium, a low temperature thermal medium passage, and a
valve for supplying said low temperature thermal medium; and
a controller which controls the opening degree of said valve for supplying said
low temperature thermal medium.
15. The fuel evaporator according to claim 11, which further comprises:
a bypass channel, which withdraws and bypasses the high temperature thermal medium
to be introduced into said chamber for controlling the gas temperature, and a bypass
valve; and
a bypass controller which controls the opening degree of said bypass valve.
16. The fuel evaporator according to claim 12, which further comprises:
a bypass channel, which withdraws and bypasses the high temperature thermal medium
to be introduced into said chamber for controlling the gas temperature, and a bypass
valve; and
a bypass controller which controls the opening degree of said bypass valve.
17. The fuel evaporator according to claim 13, which further comprises:
a bypass channel, which withdraws and bypasses the high temperature thermal medium
to be introduced into said chamber for controlling the gas temperature, and a bypass
valve; and
a bypass controller which controls the opening degree of said bypass valve.
18. A fuel evaporator composed of an evaporation chamber which evaporates a raw
liquid fuel by a high temperature thermal medium to provide a raw fuel gas, comprising
a chamber for controlling a gas temperature, which is connected to said evaporation
chamber and which controls the temperature of the raw fuel gas transferred from
said evaporation chamber by means of heat-exchange with said high temperature thermal
medium,
a passage for a high temperature thermal medium, which is connected to one end
of said evaporation chamber, and which introduces said high temperature thermal
medium into said chamber for controlling the gas temperature;
a bypass channel, which is communicated with said passage for the high temperature
thermal medium, and which discharge said high temperature thermal medium bypassing
said chamber for controlling the gas temperature, and a bypass valve; and
a bypass controller which controls the opening degree of said bypass valve.
19. A fuel evaporator composed of an evaporation chamber which evaporates a raw
liquid fuel by a high temperature thermal medium to provide a raw fuel gas, comprising
a chamber for controlling a gas temperature, which is connected to said evaporation
chamber and which controls the temperature of the raw fuel gas transferred from
said evaporation chamber by means of heat-exchange with said high temperature thermal
medium,
a passage for a high temperature thermal medium, which is connected to one end
of said evaporation chamber, and which introduces said high temperature thermal
medium into said chamber for controlling the gas temperature;
a passage for a low temperature thermal medium, which is connected to said passage
for the high temperature thermal medium, and which mixes a low temperature thermal
medium having a temperature lower than that of said high temperature thermal medium
with said high temperature thermal medium, a low temperature thermal medium inlet
and a valve for supplying said low temperature thermal medium; and
a controller which controls the opening degree of said valve for supplying said
low temperature thermal medium.
20. A fuel evaporator composed of an evaporation chamber which evaporates a raw
liquid fuel by a high temperature thermal medium to provide a raw fuel gas, comprising
a chamber for controlling a gas temperature, which is connected to said evaporation
chamber and which controls the temperature of the raw fuel gas transferred from
said evaporation chamber by means of heat-exchange with said high temperature thermal
medium,
a passage for a high temperature thermal medium, which is connected to one end
of said evaporation chamber, and which introduces said high temperature thermal
medium into said chamber for controlling the gas temperature;
a bypass channel, which is communicated with said passage for the high temperature
thermal medium, and which discharge said high temperature thermal medium bypassing
said chamber for controlling the gas temperature, and a bypass valve;
a bypass controller which controls the opening degree of said bypass valve;
a passage for a low temperature thermal medium, which is connected to said passage
for the high temperature thermal medium, and which mixes a low temperature thermal
medium having a temperature lower than that of said high temperature thermal medium
with said high temperature thermal medium, a low temperature thermal medium inlet
and a valve for supplying said low temperature thermal medium; and
a controller which controls the opening degree of said valve for supplying said
low temperature thermal medium.
21. A process for injecting a raw liquid fuel from a plurality of a raw liquid
fuel injector provided on a fuel evaporator from the outlet of vapor to the inner
part toward a plurality of heat sources provided the fuel evaporator from the outlet
of vapor to the inner part to evaporate the raw liquid fuel; which comprises:
a step for injecting the raw liquid fuel from the raw liquid fuel injector or
injectors near the outlet of the vapor, when a required amount of evaporating the
raw liquid fuel is relatively small; and
a step for injecting the raw liquid fuel from the liquid fuel injector or injectors
far from the outlet of the vapor in addition to the injector or injectors near
the outlet of the vapor, according to increase in the required amount of evaporating
the raw liquid fuel.
22. A process for injecting a raw liquid fuel from a plurality of a raw liquid
fuel injectors provided on a fuel evaporator from the outlet of vapor to the inner
part toward a plurality of heat sources provided the fuel evaporator from the outlet
of vapor to the inner part to evaporate the raw liquid fuel; which comprises:
setting at least one raw liquid fuel injector, which is not actuated at the stationary
operation to set at least one corresponding empty burned heat source, while injecting
the raw liquid fuel from other raw liquid fuel injector or injectors; and
injecting the liquid fuel from said raw liquid fuel injector, which is not actuated
at the stationary operation, in addition to the other raw liquid fuel injector
or injectors.
Description
FIELD OF THE INVENTION
The present invention relates to a fuel evaporator which can be suitably utilized
in a fuel cell system in which a raw fuel gas produced by evaporating a raw liquid
fuel is reformed in a reformer, and then supplied to a fuel cell to generate electricity.
BACKGROUND ARTS
A fuel cell system has hitherto been known in which a raw liquid fuel composed
of a mixture of methanol with water is injected into a fuel cell evaporator (evaporation
chamber) through a raw liquid raw fuel gas injection apparatus to evaporate the
raw liquid fuel to thereby produce a raw fuel gas, the resulting raw fuel gas is
reformed in a reformer and carbon monoxide contained therein is removed to prepare
a raw fuel gas which is a hydrogen enriched gas, and the hydrogen-enriched raw
fuel gas is supplied to the fuel cell to generate electricity. Meanwhile, in the
case where the fuel cell system constructed as described above is utilized under
the conditions that change in the load is extremely large, e.g., in the case of
the fuel cell system carried on a fuel cell electric vehicle, if the raw liquid
fuel is sharply injected within the fuel evaporator in order to meet the requirement
of increasing the operating power, all of the raw liquid fuel cannot be evaporated,
sometimes causing residence of the raw liquid fuel (hereinafter referred to as
"liquid residence") in the fuel evaporator. Similarly, the liquid residence easily
occurs if the fuel evaporator is not sufficiently heated due to the lacking of
the heat value used for in evaporation, for example, at the time of starting the
fuel cell system.
When the liquid residence is generated, the liquid residence, which sustained
within the fuel evaporator, is evaporated even if the injection of the raw liquid
fuel is stopped, generating the raw fuel gas. This unduly results in changing the
response of the fuel evaporator for the worse. In the case where the raw liquid
fuel is made of a mixture, among the resulting liquid residence, the components
is evaporated in the order of easiness of the evaporation and, thus, there causes
unevenness in the gas compositions of the raw fuel gas. This sometimes causes the
situation where the reformer does not exhibit its performance sufficiently or the
situation where carbon dioxide cannot be sufficiently removed, decreasing the performance
of the fuel cell.
In light of such a situation, for the purpose of attaining good response of the
fuel evaporator in order to effectively prevent the generation of the liquid residence
and, at the same time, for the purpose of quickly warming up the fuel evaporator,
our Japanese Patent Application No. 11-125366 (not disclosed) suggests, a fuel
evaporator 100, as shown in FIG. 38. This fuel evaporator 100
is composed of a body 110 of the fuel evaporator and a superheating portion
150 residing at the downstream of the body 110 of the fuel evaporator,
and a raw fuel injection apparatus 140 provided on the upper portion of
the body 10.
Into this fuel evaporator 100, is supplied a combustion gas HG (high
temperature thermal medium) obtained by catalytically combusting a hydrogen-containing
off gas, which is generated in the fuel cell (not shown), in a catalytic combustor
(not shown) as a heat source. The combustion gas HG enters from an inlet 112
in,
and is passed through the inside of a plurality of U-shaped tubes 112 for
thermal medium (referred to as thermal medium tubes) provided in a evaporation
chamber 111 within the body 110 of the fuel evaporator to reach an
outlet 112
out. Subsequently, the combustion gas HG is passed
through a combustion gas passage 113 provided on the lower portion of the
body 110 of the fuel evaporator, and introduced into the superheating portion
150 provided downstream of the body 110 of the fuel evaporator. The
raw liquid fuel FL composed of a mixture of methanol with water is injected from
the raw liquid fuel injector 140 in the state of mist, is heated on the
thermal medium tubes 112 and is evaporated to be the raw fuel gas FG. The
raw fuel gas FG is passed through the interior of evaporation tube 151 provided
within the superheating portion 150 to be superheated and then introduced
into a reformer (not shown) residing at the downstream of the superheating portion 150.
In this fuel evaporator 100, the lower surface 111
b of the
evaporation chamber 111 in the body 110 of the fuel evaporator also
serves as the upper surface 113
t of the combustion gas passage 113.
Consequently, since heat is also supplied from the lower surface 111
b
of the evaporation chamber 111, the generation of the liquid residence
is prevented and, even if the liquid residence occurs, the liquid can be quickly
evaporated. Accordingly, the fuel evaporator 110 is of good response. Also,
the warming up of the fuel evaporator 110 can be conducted in a quick manner.
However, the combustion gas HG, which is a heat source of the conventional
fuel evaporator 100 is changed depending upon the operation conditions of
the fuel cell and, thus, it is required that a required amount of the raw liquid
fuel FL should be evaporated using heat of combusting hydrogen and then is supplied
to the reactor. However, there is a problem that the situations of the evaporation
in the evaporation chamber 111 (e.g., generation of liquid residence) and
the temperature of the raw fuel gas FG are changed by various factors such as the
change in the heating value supplied (change in the operation conditions), heat
mass of the fuel evaporator itself, and change in atmospheric temperature.
In the case where the fuel cell system is carried on an fuel cell/electric automobile,
it is required for the fuel evaporator that the raw liquid fuel is quickly evaporated
at the time of starting the system or of sharply changing the load, i.e., the raw
fuel gas is obtained with much better response. Furthermore, it is desired for
driving the reformer under good conditions that the raw fuel gas is supplied at
an appropriate temperature without unevenness of the temperature. In addition,
if the raw fuel gas having an appropriate temperature range is obtained at the
time of heavy load state, the conventional fuel evaporator has a problem that the
temperature of the raw fuel gas under middle or low load conditions becomes unduly high.
SUMMARY OF THE INVENTION
An object of the present invention is, therefore, to provide a fuel evaporator,
which can secure sufficient response to a sharp change in the load, which can supply
a raw fuel gas at an appropriate temperature into the later reformer, and which
can satisfy high requirements of the fuel cell system for carrying a fuel cell/electric automobile.
According to the first aspect of the present invention, there is provided
a fuel evaporator composed of an evaporation chamber which evaporates a raw liquid
fuel by a high temperature thermal medium to provide a raw fuel gas, said evaporation
chamber comprising a plurality of evaporation chambers serially connected to each
other in a ventilation manner, and at least one raw liquid fuel injector for injecting
said raw liquid fuel being provided on each of said plurality of evaporation chambers.
In this embodiment, it is preferred that a plurality of the raw fuel injector
are provided on any one of said plurality of evaporation chambers.
In this embodiment, it is also preferable that the fuel evaporator further comprises
a controller for said raw liquid fuel injector, which, upon receiving a signal
for the requirement of said raw fuel gas, selects the raw liquid fuel injector
or injectors from which the raw liquid fuel is injected.
Also, it is preferable for the fuel evaporator according to this embodiment
to have a heat receiving portion for receiving the heat from the heat source, which
generates said high temperature thermal medium, provided near the bottom of one
of said evaporation chamber, and to have a slope downward to said heat receiving
portion provided on the bottom of another evaporation chamber or chambers.
In this specific embodiment, it is further preferable that one of said evaporation
chambers is formed so that the thermal conductive area thereof is larger than that
or those of another evaporation chamber or chambers, and said heat receiving portion
is provided on the bottom of said evaporation chamber having a larger thermal conductive area.
According to another first aspect of the present invention, there is provided
a fuel evaporator composed of an evaporation chamber which evaporates a raw liquid
fuel by a high temperature thermal medium to provide a raw fuel gas, said evaporation
chamber comprising a plurality of evaporation chambers serially connected to each
other in a ventilation manner, a chamber for controlling a gas temperature, which
controls the temperature of the raw fuel gas transferred from said evaporation
chamber by means of heat-exchange with said high temperature thermal medium, and
at least one raw liquid fuel injector for injecting said raw liquid fuel being
provided on each of said plurality of evaporation chambers.
In this embodiment, it is preferable that the fuel evaporator further comprises:
at least one thermo sensor, which detects the temperature within any of said evaporation
chambers; and a controller for said raw liquid fuel injector, which, upon receiving
a signal for the requirement of said raw fuel gas, selects the raw liquid fuel
injector or injectors from which the raw liquid fuel is injected.
In this embodiment, it is also preferable that fuel evaporator further comprises:
a low temperature thermal medium inlet, which mix the high temperature thermal
medium introduced into said chamber for controlling the gas temperature with a
low temperature thermal medium, a low temperature thermal medium passage, and a
valve for supplying said low temperature thermal medium; and a controller which
controls the opening degree of said valve for supplying said low temperature thermal medium.
Alternative to or in combination with the former preferred embodiment,
it is also preferable that fuel evaporator further comprises: a bypass channel,
which withdraws and bypasses the high temperature thermal medium to be introduced
into said chamber for controlling the gas temperature, and a bypass valve; and
a bypass controller which controls the opening degree of said bypass valve.
According to the second aspect of the present invention, there is provided
a fuel evaporator composed of an evaporation chamber which evaporates a raw liquid
fuel by a high temperature thermal medium to provide a raw fuel gas, comprising
a chamber for controlling a gas temperature, which is connected to said evaporation
chamber and which controls the temperature of the raw fuel gas transferred from
said evaporation chamber by means of heat-exchange with said high temperature thermal
medium, a passage for a high temperature thermal medium, which is connected to
one end of said evaporation chamber, and which introduces said high temperature
thermal medium into said chamber for controlling the gas temperature; a bypass
channel, which is communicated with said passage for the high temperature thermal
medium, and which discharge said high temperature thermal medium bypassing said
chamber for controlling the gas temperature, and a bypass valve; and a bypass controller
which controls the opening degree of said bypass valve.
Alternatively, according to the second aspect of the present invention,
there is provided a fuel evaporator composed of an evaporation chamber which evaporates
a raw liquid fuel by a high temperature thermal medium to provide a raw fuel gas, comprising
a chamber for controlling a gas temperature, which is connected to said evaporation
chamber and which controls the temperature of the raw fuel gas transferred from
said evaporation chamber by means of heat-exchange with said high temperature thermal medium,
a passage for a high temperature thermal medium, which is connected to one end
of said evaporation chamber, and which introduces said high temperature thermal
medium into said chamber for controlling the gas temperature;
a passage for a low temperature thermal medium, which is connected to said passage
for the high temperature thermal medium, and which mixes a low temperature thermal
medium having a temperature lower than that of said high temperature thermal medium
with said high temperature thermal medium, a low temperature thermal medium inlet
and a valve for supplying said low temperature thermal medium; and
a controller which controls the opening degree of said valve for supplying said
low temperature thermal medium.
Also, according to the second aspect of the present invention, there is provided
a fuel evaporator composed of an evaporation chamber which evaporates a raw liquid
fuel by a high temperature thermal medium to provide a raw fuel gas, comprising
a chamber for controlling a gas temperature, which is connected to said evaporation
chamber and which controls the temperature of the raw fuel gas transferred from
said evaporation chamber by means of heat-exchange with said high temperature thermal
medium, a passage for a high temperature thermal medium, which is connected to
one end of said evaporation chamber, and which introduces said high temperature
thermal medium into said chamber for controlling the gas temperature; a bypass
channel, which is communicated with said passage for the high temperature thermal
medium, and which discharge said high temperature thermal medium bypassing said
chamber for controlling the gas temperature, and a bypass valve; a bypass controller
which controls the opening degree of said bypass valve; a passage for a low temperature
thermal medium, which is connected to said passage for the high temperature thermal
medium, and which mixes a low temperature thermal medium having a temperature lower
than that of said high temperature thermal medium with said high temperature thermal
medium, a low temperature thermal medium inlet and a valve for supplying said low
temperature thermal medium; and a controller which controls the opening degree
of said valve for supplying said low temperature thermal medium.
Also included in the present invention is a process for injecting a raw liquid
fuel from a plurality of a raw liquid fuel injector provided on a fuel evaporator
from the outlet of vapor to the inner part toward a plurality of heat sources provided
the fuel evaporator from the outlet of vapor to the inner part to evaporate the
raw liquid fuel; which comprises:
a step for injecting the raw liquid fuel from the raw liquid fuel injector or
injectors
near the outlet of the vapor, when a required amount of evaporating the raw liquid
fuel is relatively small; and
a step for injecting the raw liquid fuel from the liquid fuel injector or injectors
far from the outlet of the vapor in addition to the injector or injectors near
the outlet of the vapor, according to increase in the required amount of evaporating
the raw liquid fuel.
Further more the present invention relates to a process for injecting a raw
liquid fuel from a plurality of a raw liquid fuel injectors provided on a fuel
evaporator from the outlet of vapor to the inner part toward a plurality of heat
sources provided the fuel evaporator from the outlet of vapor to the inner part
to evaporate the raw liquid fuel; which comprises:
setting at least one raw liquid fuel injector, which is not actuated at the
stationary operation to set at least one corresponding empty burned heat source,
while injecting the raw liquid fuel from other raw liquid fuel injector or injectors; and
injecting the liquid fuel from said raw liquid fuel injector, which is
not actuated at the stationary operation, in addition to the other raw liquid fuel
injector or injectors.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 shows the configuration of a fuel cell system, in which a fuel evaporator
according to the first embodiment of the present invention is used.
FIG. 2 is a partial cutaway plane view of the fuel evaporator according to the
first embodiment of the present invention.
FIG. 3 is a cross-sectional view taken along the line A—A of FIG. 2.
FIG. 4 is a cross-sectional view taken along the line B—B of FIG. 2.
FIG. 5 is a cross-sectional view taken along the line C—C of FIG. 2.
FIG. 6 is a block diagram showing the control system of the fuel evaporator
according to the first embodiment of the present invention.
FIG. 7 is a drawing showing the relation between the position of injecting the
raw liquid fuel in an evaporation chamber and the temperature of the raw fuel gas
at the outlet of the evaporation chamber.
FIG. 8(
a) is a drawing which explains an aimed temperature range
and a tolerance temperature range of the raw fuel gas, and
FIG. 8(
b) shows a basic injection pattern at a stationary state.
FIG. 9 is a flowchart showing the control of the fuel evaporator according to
the first embodiment of the present invention at a stationary state.
FIG. 10 is a flowchart showing the control of the fuel evaporator according
to the first embodiment of the present invention at an accelerated state.
FIG. 11 is a drawing showing the relation between the operation power and the
temperature of the raw fuel gas in the fuel cell system using the fuel evaporator
according to the first embodiment of the present invention.
FIG. 12 is a partial cutaway plane view of the fuel evaporator according to
the second embodiment of the present invention.
FIG. 13 is a block diagram showing the control system of the fuel evaporator
according to the second embodiment of the present invention.
FIG. 14 is a flowchart showing the control where the temperature of the raw
fuel gas is controlled by mixing a diluted air with the combustion gas of the fuel
evaporator according to the second embodiment of the present invention.
FIG. 15 is a partial cutaway plane view of the fuel evaporator according to
the third embodiment of the present invention.
FIG. 16 is a block diagram showing the control system of the fuel evaporator
according to the third embodiment of the present invention.
FIG. 17 is a flowchart showing the control where the temperature of the raw
fuel gas is controlled by bypassing the combustion gas of the fuel evaporator according
to the third embodiment of the present invention.
FIG. 18 is a partial cutaway plane view of the fuel evaporator according to
the fourth embodiment of the present invention.
FIG. 19 is a cross-sectional view taken along the line A—A of FIG. 18.
FIG. 20 is a cross-sectional view taken along the line B—B of FIG. 18.
FIG. 21 is a cross-sectional view taken along the line C—C of FIG. 18.
FIG. 22 is a block diagram showing the control system of the fuel evaporator
according to the fourth embodiment of the present invention.
FIG. 23 is a flowchart showing the control of the fuel evaporator according
to the fourth embodiment of the present invention at a stationary state.
FIG. 24 is a flowchart showing the control of the fuel evaporator according
to the fourth embodiment of the present invention at an accelerated state.
FIG. 25 is a partial cutaway plane view of the fuel evaporator according to
the fifth embodiment of the present invention.
FIG. 26 is a cross-sectional view taken along the line A—A of FIG. 25
FIG. 27 is a cross-sectional view taken along the line B—B of FIG. 25.
FIG. 28 is a block diagram showing the control system of the fuel evaporator
according to the fifth embodiment of the present invention.
FIG. 29 is a drawing showing the relation between the position of injection
of the raw liquid fuel in an evaporation chamber and the temperature of the raw
fuel gas at the outlet of the evaporation chamber.
FIG. 30(
a) is a drawing explaining an aimed temperature range
and a tolerance temperature range of the raw fuel gas, and
FIG. 30(
b) shows a basic injection pattern at a stationary state.
FIG. 31 is a flowchart showing the control of the fuel evaporator according
to the fifth embodiment of the present invention at a stationary state.
FIG. 32 is a flowchart showing the control of the fuel evaporator according
to the fifth embodiment of the present invention at an accelerated state.
FIG. 33 is a flowchart showing the control where the temperature of the raw
fuel gas is controlled by bypassing the combustion gas of the fuel evaporator according
to the fifth embodiment of the present invention.
FIG. 34 is a drawing showing the relation between the operation power and the
temperature of the raw fuel gas in the fuel cell system using the fuel evaporator
according to the fifth embodiment of the present invention.
FIG. 35 is a partial cutaway plane view of the fuel evaporator according to
the sixth embodiment of the present invention.
FIG. 36 is a block diagram showing the control system of the fuel evaporator
according to the sixth embodiment of the present invention.
FIG. 37 is a flowchart showing the control where the temperature of the raw
fuel gas is controlled by mixing a diluted air with the combustion gas of the fuel
evaporator according to the fifth embodiment of the present invention.
FIG. 38 is a cross-sectional view showing the conventional fuel evaporator.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
A fuel evaporator according to the first to second aspects of the present invention
will now be described.
(First Aspect)
First, the fuel evaporator according to the first aspect of the present invention
will now be described by referring to the drawings. The fuel evaporator according
to the first aspect of the present invention is divided into four types (first
to fourth embodiments), depending upon the presence or absence of a chamber for
controlling the temperature of the raw fuel gas, the method of supplying a high
temperature thermal medium into the chamber for controlling the gas temperature,
etc. The fuel evaporator of the fourth embodiment has no chamber for controlling
the gas temperature.
<<First Embodiment>>
The fuel evaporator of the first embodiment will now be described.
FIG. 1 shows the configuration of a fuel cell system, in which a fuel evaporator
according to the first embodiment of the present invention is used, FIG. 2 is a
partial cutaway plane view of the fuel evaporator according to the first embodiment
of the present invention, FIG. 3 is a cross-sectional view taken along the line
A—A of FIG. 2, FIG. 4 is a cross-sectional view taken along the line B—B
of FIG. 2, and FIG. 5 is a cross-sectional view taken along the line C—C
of FIG.
2.
[Fuel Cell System]
First, the configuration of a fuel cell system FCS in which the fuel evaporator
1 of the first embodiment is used will be described by referring to FIG.
1. The fuel cell system FCS is composed mainly of a fuel evaporator
1,
a reformer
2, a CO remover
3, an air compressor
4, a fuel
cell
5, a gas/liquid separator
6, a combustion burner
7, and
a tank T for a raw liquid fuel (a tank for storing a water/methanol mixed liquid).
The fuel evaporator
1 possesses a body
10 of the fuel evaporator,
a catalytic combustor
20, a chamber
30 for controlling the temperature
of the gas (hereinafter referred to as temperature-control chamber), and a raw
liquid fuel injection apparatus
40. The fuel evaporator
1 is an apparatus
in which a raw liquid fuel, such as a water/methanol mixed liquid, pumped from
the tank T for the raw liquid fuel via a pump P, is injected into the body
10
of the fuel evaporator to be converted into the raw fuel gas. The high temperature
thermal medium for evaporating the raw liquid fuel is a combustion gas supplied
from the catalytic combustor
20. The combustion gas is obtained by catalytically
combusting the off-gas etc. in the fuel cell
5 in the catalytic combustor
20. The raw fuel gas obtained as described above whose temperature is controlled
in the temperature-control chamber
30 is supplied into the reformer
2.
The details of the fuel evaporator will be described later on.
The reformer
2 reforms the raw fuel gas supplied from the fuel evaporator
1 into a hydrogen-enriched raw fuel gas due to steam reforming and partial
oxidation. With regard to the steam reforming and partial oxidation, the reactions
are accelerated by the function of a catalyst filled within the reformer
2.
In order to partially oxidize the raw fuel gas, air is supplied into the reformer
2 via the air compressor
4 through pipes (not shown).
In the resulting hydrogen-enriched raw fuel gas, carbon monoxide is selectively
reacted in the presence of a catalyst by means of the CO remover. This converts
carbon monoxide into carbon dioxide, which is then removed. The removal of carbon
monoxide is carried out in order to prevent the platinum catalyst from being poised
to enlarge the service life of the fuel cell
5. The CO remover
3
typically possesses two CO removers, i.e., No.
1 CO remover
3a
and No.
2 CO remover
3b, and quickly decreases the concentration
of carbon monoxide in the hydrogen enriched raw fuel gas. The temperature of the
hydrogen-enriched raw fuel gas in the CO remover is controlled by means of a heat
exchanger not so as to bring about any undesirable reaction such as converse shifting
or methanation.
The air compressor
4 compresses an air to supply the air required in the
fuel cell
5 into the fuel cell
5. The air compressor
4 also
supplies the air for partial oxidation in the reformer
2 as described above.
Furthermore, the air compressor
4 supplies the air to the No.
2 CO
remover
3b in order to convert carbon monoxide contained in the raw
fuel gas into carbon dioxide. As the power for the air compressor
4, an
energy generated during the course of swelling the off gas discharged from the
fuel cell
5 can be utilized.
The fuel cell
5 is a solid macromolecular type fuel cell as described
above. Into a hydrogen pole is supplied the raw fuel gas, from which carbon monoxide
is removed, and into an oxygen pole of the fuel cell
5 is supplied the air
from the air compressor
4. Within the fuel cell
5, water and electricity
electrochemically occur from hydrogen and oxygen in the presence of the platinum
catalyst. The electricity can be used as a power source for an electric vehicle
or such.
The off gas containing unused hydrogen and the produced water are discharged
from the hydrogen pole of the fuel cell
5, and they are separated into gaseous
components and liquid components by means of a gas/liquid separator
6. At
the time of starting the fuel cell system FCS, the off gas is supplied into a combustion
burner
7 and then combusted to warm up the catalytic combustor
20
etc. After the completion of the warming-up, the off gas is supplied into the fuel
evaporator
1 without combustion in the combustion burner
7, and is
catalytically combusted in the catalytic combustor
20 to be used as a heat
source for the evaporation of the raw liquid fuel. At the time of starting the
fuel cell system FCS, a fuel for catalytic combustion (e.g., methanol) is supplied
into the catalytic combustor
20 instead of the off gas.
The functions and configuration of the fuel cell system FCS in which the fuel
evaporator
1 according to the first embodiment is used are described above.
[Fuel Evaporator]
Subsequently, the fuel evaporator
1 which realizes the present
invention will now be described. (See, FIGS. 2 to
5.) The fuel evaporator
1 according to the first embodiment is composed of the body of the fuel
evaporator
10, the catalytic combustor
20, the temperature control
chamber
30, and the raw liquid fuel injection apparatus
40.
With regard to schematically positional relation, the body
10 of the
fuel evaporator is provided on the upper portion of the catalytic combustor
20,
the temperature control chamber
30 is provided on one side of the body
10
of the fuel evaporator, and the raw liquid fuel injection apparatus
40 is
provided on the upper portion of the body
10 of the fuel evaporator.
(1) Body of Fuel Evaporator
As shown in FIG. 3 or such, the body
10 of the fuel evaporator possesses
a boxy evaporation chamber
11 having a plurality of U-shaped tubes
12A
for thermal medium (hereinafter simply referred to as the "thermal medium tubes".
The evaporation chamber evaporates the raw liquid fuel FL injected from the raw
liquid fuel injection apparatus
40 by means of the combustion gas HG, which
serves as the high temperature thermal medium, to bring about the raw fuel gas
FG. Here, the evaporation chamber
11 is composed such that a first evaporation
chamber
11A, a second evaporation chamber
11B and a third evaporation
chamber
11C are connected in series in a ventilation manner. The raw fuel
gas FG generated in the first evaporation chamber
11A and the second evaporation
chamber
11B, is configured to be introduced into the later temperature control
chamber
30 via the third evaporation chamber
11C. The symbol
11p
is a diaphragm which divides the evaporation chamber
11 in a ventilation manner.
In the evaporation chamber
11, the first evaporation chamber
11A
is the biggest; the second evaporation chamber
11B is smaller than the first
evaporation chamber
11A; and the third evaporation chamber
11C is
the smallest. These evaporation chambers
11A,
11B, and
11C
have U-shaped thermal medium tubes
12A,
12B, and
12C provided
thereon respectively, according to the size (capacity) of the evaporation chamber.
The size (capacity) of the first evaporation chamber
11A is approximately
the same as the sum of the size (capacity) of the second evaporation chamber
11B
and that of the third evaporation chamber
11C, and is configured so that
the heat value thereof becomes larger than those of the other evaporation chambers
11B and
11C by having more thermal medium tubes
12A (the numbers
of the thermal medium tubes
12A>the number of the thermal medium tubes
12B>the numbers of the thermal medium tubes
12C). Consequently,
the first evaporation chamber
11A has the highest performance for evaporating
the raw liquid fuel FL to generate the raw fuel gas HG (as described later on,
the first evaporation chamber
11A is also heated from the lower portion
by means of the catalytic combustor
29.)
As for the order of serially connecting the evaporation chambers
11, for
example, the first evaporation chamber
11A may reside between the second
evaporator chamber
11B and the third evaporator chamber
11C.
As shown in FIG. 3, the tubes
12A in the first evaporation chamber are
placed so that the distances between the respective thermal medium tubes
12A
become wider toward the upper direction and they become narrower toward the lower
direction (i.e., the thermal medium tubes become sparser as they are near from
the injector
41A, and they become denser as they are far from the injector
41A), in order to widespread the raw liquid fuel FL injected from the injector
41A among every portions of the evaporation chamber
12A including
the portion far from the injector
41A. Also, by such a configuration, the
generation of big film boiling such as the film boiling spread between the thermal
medium tubes
12A can be reduced (i.e., the distances between the thermal
medium tubes
12A at the portion near the injector
41A are widened
to prevent greatly grow in the portions where the film boiling occurs), to thereby
secure the passages of the raw liquid fuel FL and the raw fuel gas FG. By placing
the tubes
12A at the lower portion of the first evaporation chamber
11A
in a dense manner, and by strongly heating the lower portion of the first evaporation
chamber
11A, the liquid residence on the lower portion of the first evaporator
chamber
11A can also be prevented (the generation of the liquid residence
on the lower portion of the first evaporator
11A is also prevented by increasing
the heat mass at the lower portion of the first evaporation chamber
11A).
With regard to the placements and the functions of the thermal medium tubes
12B
and
12C in the second and third evaporation chambers
11B and
11C,
they are substantially the same as those of the tubes
12A in the first evaporation
chamber
11A.
As shown in FIG. 3, the cross-section of the lower surface
11b of
the first evaporation chamber
11A is configured into a wave form to meet
the shape (placements) of the thermal medium tubes
12A residing at the lower
portion amongst them, so as to minimize the space between the thermal medium tubes
12A and the lower portion of the evaporation chamber as low as possible
not so as to generate any large liquid residence. However, there are some gaps
between the lower surface
11b of the first evaporation chamber
11A
and the tubes
12A for residing at the lower portion so that they are not
come in contact with each other due to the vibration etc.
On the other hand, as shown in FIG. 3, the lower surfaces of the second and the
third evaporation chambers
11B and
11C are slanted toward the side
of the first evaporation chamber
11A downwardly so that if the liquid residence
is brought about on the second or the third evaporation chamber
11B or
11C,
the resulting liquid residence flows into the first evaporation chamber
11A.
A baffle lip is configured so as to form an opening which allows for the liquid
residence flowing into the portion of the lower surface
11b of the
evaporation chamber. The height of the opening positioned at the upper portion
of the baffle
11p is substantially the same as the thickness of the
bundle of the thermal medium tubes
12A (
12B and
12C), so that
the resulting raw fuel gas FL easily flows.
As shown in FIG. 4, the front side of the first evaporation chamber
11A
(on the basis of the fuel evaporator
1) is blocked with a supporting plate
12A to hold the tubes
12A not so as to mix the combustion gas HG
with the raw fuel gas FG. Both ends of the thermal medium tube
12A are opened,
and the combustion gas HG enters into the thermal medium tube
12A from the
lower end of the thermal medium tube
12A (inlet
12A
in
of the thermal medium tube; sometimes referred to as tube inlet
12A
in),
while existing from the upper end of the thermal medium tube
12A (outlet
12A
out of the thermal medium tube; sometimes referred to as tube
outlet
12A
out). From the tube outlet
12A
out,
a combustion gas passage
13 (a first combustion gas passage
13a),
which will be described later on, is started. Here, with regard to the positions
such as front, side, and rear sides, they are based on the fuel evaporator
1
(and so forth).
The upper side of the thermal medium tube
12A is slanted so as to descend
towards the end thereof. The reason why the thermal medium tube
12A has
a slant as described above is that in the case where the raw liquid fuel FL is
adhered on the upper side of the tube
12A in the form of droplets, the droplets
thus adhered allow for moving towards the supporting plate
12A to thereby
evaporate the droplets due to the heat possessed by the supporting plate
12A.
Similarly, the thermal medium tubes
12B and
12C of the second and
the third evaporation chambers
11B and
11C are also slanted as in
the case of the thermal medium tube
12A of the first evaporation chamber
11A.
As shown in FIG. 5, the rear surface (on the basis of the fuel evaporator
1)
of the second and the third evaporation chambers
11B and
11C are
blocked with a supporting plate
12Ba which holds the thermal medium tubes
12B and
12C in a unification manner, not so as to mix the combustion
gas HG with the raw fuel gas FG. Both ends of the respective thermal medium tube
12B or
12C are opened, and the combustion gas HG enters into the
thermal medium tube
12B or
12C from the lower end of the thermal
medium tube
12B or
12C (tube inlet
12B
in or
12C
in),
while existing from the upper end of the thermal medium tube
12B or
12C
(tube outlet
12B
out or
12C
out). A diaphragm
13p is provided not so as to mix the combustion gas HG of the tube
inlet
12B
in or
12C
in with combustion gas of
the tube outlet
12B
out or
12C
out. After heating
the first evaporation chamber
11A, the combustion gas HG diverges to heat
the second and the third evaporation chambers
11B and
11C.
While the body
10 of the fuel evaporator evaporates
11 the raw
liquid fuel FL within the evaporation chambers to generate the raw fuel gas FG,
the generated raw fuel gas FG is passed through a ventilation means
14 possessed
by the third evaporation chamber
11C to be introduced into the temperature
control chamber
30 (see FIG.
30). The ventilation means
14
is composed of a punched plate having many small pores etc. so that the droplets
of the raw liquid fuel FL such as fly droplets do not directly enter in the temperature
control chamber
30.
The fuel evaporator
1 according to this embodiment possesses a combustion
gas passage
13 also severing as keeping the evaporation chamber
11
warm. The combustion gas passage
13 is divided into a first combustion gas
passage
13A and a second combustion gas passage
13B. The first combustion
gas passage
13A is started at the tube outlet
12A
out of
the first evaporation chamber
11A and extends to the tube inlets
12B
in
and
12C
in of the second and the third evaporation chambers
11B and
11C. Specifically, the first combustion gas passage
13A
is provided at the front, side, and rear surfaces of the first evaporation chamber
11A and the rear surfaces (upper halves) of the second and the third evaporation
chambers
11B and
11C. The first combustion gas passage
13A
according to this embodiment has a construction where it totally covers a diaphragm
24 of the catalytic combustor
20 and a side surface
20s
of the catalytic combustor
20.
On the other hand, the second combustion gas passage
13b is started
at the tube outlets
12B
out and
12C
out of the
second and the third evaporation chambers
11B and
11C and extends
to the temperature control chamber
30 (shell
32). Specifically, the
second combustion gas passage
13b is placed on the rear surfaces
(lower halves), the lower surfaces and the front surfaces of the second and the
third evaporation chambers
11B and
11C.
The member represented by the symbol
15 in FIG. 2 is an air inlet, which
introduces air (oxygen) required for the reformation (partial oxidation) into the
reformer
2 at the stage of generating the raw fuel gas FG in the fuel evaporator
1 in order to mix the air with the raw fuel gas FG. By mixing the air with
the raw fuel gas FG, the reaction in the reformer
2 takes place smoothly.
Specifically, by introduction of the air at the stage of generating
the raw fuel gas in the fuel evaporator
1, during the migration of the raw
fuel gas FG within each of the evaporation chambers
11A,
11B, and
11C toward the outlet of the body
10 of the evaporation chamber,
the raw fuel gas FC collides with each of the tubes
12A,
12B, and
12C provided within each evaporation chamber
11A,
11B, or
11C and a diaphragm
11p to complete the perfect mixing of
the raw fuel gas FG with the air. This makes it possible to introduce the raw fuel
gas having a uniform composition containing the air into the reformer
2.
Preference is given to the placement of air inlet
15 on the evaporation
chamber
11 (first evaporation chamber
11A) having a high heat value
and a high evaporation performance, because of the necessity of the increase in
the temperature of the introduced air.
(2) Catalytic Combustor
The catalytic combustor
20 according to the first embodiment of the present
invention is in a boxy form similar to the case of the evaporation chamber
11,
and has a catalytic layer
22 comprising a catalyst in the shape of a honeycomb
accommodated therewith. The catalytic combustor
20 combusts the off gas
OG from the fuel cell
5, which is the gas to be combusted, i.e., a mixed
gas comprising hydrogen and oxygen. The combusted gas HG generated due to the catalytic
combustion of the off gas OG is used as a high temperature thermal medium in the
evaporation of the raw liquid fuel FL in the evaporation chamber
11, keeping
the temperature of the evaporation chamber
11 warm, and controlling the
temperature of the temperature control chamber
30.
Due to catalytic combustion in the interior thereof, the catalytic combustor
20 itself is kept at a high temperature. In this embodiment, since the catalytic
combustor
20 itself makes a use of the heat genera
