U.S. patent application number 10/684805 was filed with the patent office on 2004-06-17 for burner, hydrogen generator, and fuel cell power generation system.
Invention is credited to Asou, Tomonori, Maenishi, Akira, Mukai, Yuji, Yotsuya, Motoo.
Application Number | 20040115577 10/684805 |
Document ID | / |
Family ID | 32040811 |
Filed Date | 2004-06-17 |
United States Patent
Application |
20040115577 |
Kind Code |
A1 |
Maenishi, Akira ; et
al. |
June 17, 2004 |
Burner, hydrogen generator, and fuel cell power generation
system
Abstract
A burner comprises a fuel distributor having a plurality of fuel
injection holes through which a fuel gas is injected into a
combustion space 3, an air injector 2 placed to surround the fuel
distributor and having a plurality of air injection holes through
which air is injected into the combustion space 3, a temperature
detector placed such that a temperature detecting portion at a tip
end thereof is located within the air injection hole, a body
portion thereof is contained within the air injector, and an air
layer is formed between the temperature detector and an inner wall
of the air injector 9, and a flame detector connected to the
temperature detector, for detecting a flame condition based on
temperature information within the combustion space which is
obtained from the temperature detector.
Inventors: |
Maenishi, Akira; (Ikeda-shi,
JP) ; Yotsuya, Motoo; (Soraku-gun, JP) ;
Mukai, Yuji; (Kadomo-shi, JP) ; Asou, Tomonori;
(Kitakatsuragi-gun, JP) |
Correspondence
Address: |
STEVENS DAVIS MILLER & MOSHER, LLP
1615 L STREET, NW
SUITE 850
WASHINGTON
DC
20036
US
|
Family ID: |
32040811 |
Appl. No.: |
10/684805 |
Filed: |
October 15, 2003 |
Current U.S.
Class: |
431/75 |
Current CPC
Class: |
F23D 14/725 20130101;
H01M 8/0612 20130101; C01B 2203/0233 20130101; C01B 2203/066
20130101; C01B 2203/0816 20130101; F23C 2900/9901 20130101; F23D
2207/00 20130101; F23D 14/22 20130101; Y02E 60/50 20130101; F23D
2208/10 20130101; C01B 2203/0822 20130101; C01B 2203/0827 20130101;
C01B 2203/1695 20130101; H01M 8/04007 20130101; Y02P 20/10
20151101; C01B 3/38 20130101; C01B 2203/0283 20130101 |
Class at
Publication: |
431/075 |
International
Class: |
F23N 005/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 16, 2002 |
JP |
2002-301799 |
Claims
What is claimed is:
1. A burner having a fuel distributor configured to inject a fuel
supplied from a fuel supply device; and an air injector placed such
that the air injector surrounds the fuel distributor so as to form
a combustion space around the fuel distributor and having an air
injection hole through which air supplied from an air supply device
is injected, the air injected from the air injection hole and the
fuel injected from the fuel distributor being combusted to allow a
flame to be generated in the combustion space, the burner
comprising: a temperature detector for detecting a temperature of
the combustion space, the temperature detector having a temperature
detecting portion located within the air injection hole or in an
air flow passage of the combustion space; and a flame detector for
detecting a condition of the flame within the combustion space,
based on the temperature detected by the temperature detector.
2. The burner according to claim 1, wherein the temperature
detector is placed such that the temperature detecting portion is
located within the air injection hole or within the combustion
space in the vicinity of the air injection hole.
3. The burner according to claim 1, wherein the temperature
detector is placed so as to penetrate the air injector.
4. The burner according to claim 1, wherein the temperature
detecting portion of the temperature detector is thermally
insulated from an inner face of the air injection hole.
5. The burner according to claim 4, wherein a gap is formed between
the temperature detector and the inner face of the air injection
hole, and a width of the gap is substantially uniform over an outer
periphery of the temperature detector.
6. The burner according to claim 4, wherein the air injector has a
plurality of air injection holes, and a cross-sectional area of the
gap between the air injection hole within which the temperature
detector is provided and the temperature detector is substantially
equal to a cross-sectional area of the air injection hole within
which the temperature detector is not provided.
7. The burner according to claim 1, wherein the temperature
detector has the temperature detecting portion at an end portion
thereof, and a body of the temperature detector is contained within
the air injector.
8. The burner according to claim 7, wherein an end portion of the
temperature detecting portion side of the temperature detector is
substantially covered with an oxidation film.
9. The burner according to claim 7, wherein an end portion of the
temperature detecting portion side of the temperature detector is
substantially hemispherical.
10. The burner according to claim 1, wherein the temperature
detector is a sheath-shaped thermo couple.
11. The burner according to claim 1, wherein a plurality of
temperature detectors are provided at different positions within
the combustion space to detect temperatures of different regions
within the combustion space.
12. The burner according to claim 1, wherein the combustion space
has a cross-sectional area that increases toward a flame radiation
direction.
13. The burner according to claim 1, further comprising: an
electrode contained within the fuel distributor and having an end
portion that protrudes into the combustion space; and an ignition
circuit electrically connected to the electrode, for applying a
voltage to the electrode to allow electric discharge from the
electrode to occur within the combustion space.
14. The burner according to claim 13, further comprising: a switch
configured to perform switching so that the electrode is connected
to the ignition circuit during ignition, and the electrode is
connected to the flame detector when the flame detector judges that
ignition has occurred based on temperature information of the
combustion space from the temperature detector, wherein the flame
detector detects the flame based on the temperature information
from the temperature detector and detects the flame based on an
output current from the electrode.
15. The burner according to claim 14, wherein the end portion of
the electrode that protrudes into the combustion space is placed in
a region different from a region of the combustion space in which
the temperature detector is placed, to detect the flame in the
region which is different from the region where the flame is
detected by the temperature detector.
16. The burner according to claim 15, wherein the temperature
detector detects the flame in an upper region of the combustion
space in the flame radiation direction, and the electrode detects
the flame in a lower region of the combustion space in the flame
radiation direction.
17. A hydrogen generator comprising: a burner having a fuel
distributor configured to inject a fuel supplied from a fuel supply
device; and an air injector placed such that the air injector
surrounds the fuel distributor so as to contain the fuel
distributor and form a combustion space around the fuel distributor
and having an air injection hole through which air supplied from an
air supply device is injected, the air injected from the air
injection hole and the fuel injected from the fuel distributor
being combusted to allow a flame to be generated in the combustion
space, the burner including: a temperature detector for detecting a
temperature of the combustion space, the temperature detector
having a temperature detecting portion located within the air
injection hole or in an air flow passage of the combustion space;
and a flame detector for detecting a condition of the flame within
the combustion space, based on the temperature detected by the
temperature detector, and a reformer for generating a reformed gas
containing hydrogen by a reforming reaction of a feed material
including a compound containing at least carbon and hydrogen, the
burner being configured to heat the reformer.
18. A fuel cell power generation system comprising: a hydrogen
generator including: a burner having a fuel distributor configured
to inject a fuel supplied from a fuel supply device; and an air
injector placed such that the air injector surrounds the fuel
distributor so as to contain the fuel distributor and form a
combustion space around the fuel distributor and having an air
injection hole through which air supplied from an air supply device
is injected, the air injected from the air injection hole and the
fuel injected from the fuel distributor being combusted to allow a
flame to be generated in the combustion space, the burner
including: a temperature detector for detecting a temperature of
the combustion space, the temperature detector having a temperature
detecting portion located within the air injection hole or in an
air flow passage of the combustion space; and a flame detector for
detecting a condition of the flame within the combustion space,
based on the temperature detected by the temperature detector, and
a reformer for generating a reformed gas containing hydrogen by a
reforming reaction of a feed material including a compound
containing at least carbon and hydrogen, the burner being
configured to heat the reformer; and a fuel cell configured to
generate a power using a gas containing hydrogen as a major
component which is supplied from the hydrogen generator to a fuel
electrode and an oxidizing gas supplied to an oxidizing electrode.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a burner. Particularly, the
present invention relates to a burner configured to perform
combustion using a fuel gas containing a high content of hydrogen
and a low content of hydrocarbon based substance. More
particularly, the present invention relates to a burner used in a
hydrogen generator configured to generate hydrogen to be supplied
to apparatus using hydrogen such as a fuel cell, from a fuel gas
mainly containing a hydrocarbon based substance as a compound
containing at least carbon and hydrogen, for example, a natural
gas, LPG, gasoline, naphtha, coal oil, or methanol, or a burner
configured to combust a fuel gas containing hydrogen as a major
component such as an off-gas delivered from the fuel cell, to
generate heat to be used for air-conditioning or supplying hot
water.
[0003] 2. Description of the Related Art
[0004] In a fuel cell power generation system, a hydrogen generator
that generates hydrogen to be supplied to a fuel cell is configured
such that water is added to a fuel gas mainly containing a
hydrocarbon based substance, such as a natural gas, LPG, gasoline,
naphtha, coal oil, or methanol, and the resulting mixture is heated
at 650 to 700.degree. C., so that the fuel gas is reformed to allow
hydrogen to be taken out (reforming reaction). The reformed gas
containing a high content of hydrogen obtained by the reforming
reaction is supplied to the fuel cell and used for power
generation. Heating in the reforming reaction is performed by using
a burner. The burner is configured to combust the fuel gas and air
to generate a flame, thereby generating heat. In the hydrogen
generator, using the heat generated by the burner, the heating for
the reforming reaction is performed. As a fuel gas of the burner,
for example, an off-gas delivered from the fuel cell is used for
efficient use of a feed gas. The off-gas contains a high content of
hydrogen because it contains large amount of hydrogen which remains
unused after the reaction in the fuel cell and hence has high
reactivity. For this reason, when a mixture of the off-gas as the
fuel gas and the air is supplied to a combustion space (or
chamber), the problem that the flame flows back will arise. In such
a situation, problems associated with safety arises. Accordingly,
in the burner, the off-gas and the air are independently supplied
to the combustion space.
[0005] In the burner configured as described above, in order to
detect ignition mistake, vanishment of flame, abnormal combustion,
or the like for the purpose of safe and efficient combustion, a
flame rod extends from outside to an inside of the combustion space
to detect the flame (see Japanese Laid-Open Paten Application
Publication No. 2001-201046. An igniter installed in an upper space
of the combustion space is adapted to perform ignition (see
Japanese Laid-Open Patent Application Publication No. Hei.
7-22043).
[0006] In a flame detecting method using the flame rod, a voltage
is applied between the flame rod in contact with the flame
generated within the combustion space and a burner body, and a
current generated by ions residing within the flame is detected, so
that the flame is detected based on the current. The flame
detecting method using the flame rod is advantageous when numerous
ions are generated during a combustion reaction generating the
flame, for example, the fuel gas containing large amount of carbon
hydrogen based combustible substances. However, when the fuel gas
containing a high content of hydrogen and a low content of the
hydrocarbon based combustible substance is combusted as described
above, no ions are generated in a combustion reaction generating
the flame. For this reason, no current flows when the voltage is
applied between the flame rod and the burner body, and it is
therefore difficult to detect the flame.
[0007] Meanwhile, in the hydrogen generator, a hydrogen-rich gas
generated during start and containing H.sub.2 as a major component
contains large amount of CO in addition to H.sub.2. Such a
hydrogen-rich gas (hereinafter referred to as a generated gas) is
not supplied to the fuel cell because CO contained in the gas
degrades an electrode of the fuel cell. Accordingly, the generated
gas is also used as the fuel gas of the burner for efficient use as
in the case of the off-gas. As described above, in the hydrogen
generator, the hydrocarbon based substance (e.g., CH.sub.4)
contained in the fuel gas is converted into H.sub.2 and CO.sub.2 by
the reforming reaction. Therefore, the hydrocarbon based
combustible substance remaining unconverted, which is contained in
the generated gas, is less. For this reason, in the combustion
reaction using the generated gas as the fuel gas, generated ions,
are less as in the case of using the off-gas. So, when the flame
detecting method using the flame rod is applied, the current
detected when applying the voltage between the flame rod and the
burner body is small, and it is therefore difficult to detect the
flame as in the case of using the off-gas.
[0008] In the burner of the hydrogen generator in the fuel cell
power generation system, a current value detected by the flame rod
is converted into a voltage value, and it is judged whether or not
a flame has vanished based on whether or not the voltage value is
smaller than a threshold voltage for judgment of vanishment of the
flame. When the voltage value is lower than the threshold voltage,
it is judged that the flame has vanished and an operation is
stopped. It should be noted that, in the burner to which the
off-gas or the generated gas is supplied as the fuel gas, the
current value detected by the flame rod is small because of small
amount of ions residing in the flame, and hence, the voltage value
is small. For this reason, if the threshold voltage used for
judgment of vanishment of the flame is set relatively higher, the
voltage value obtained by detection becomes below the threshold
voltage, and it is judged that the flame has vanished regardless of
generation of the flame. In view of this, it is necessary to set
the threshold lower. But, in such a case, there is a possibility
that misjudgment is made due to variation in the value caused by
noises in a component of a system. As should be appreciated from
the above, when combustion is performed using the off-gas or the
generated gas as the fuel gas, it is difficult to detect the flame
with high accuracy in the flame detecting method using the flame
rod.
[0009] In addition, in the above configuration of the burner, there
exists a need for a space in the vicinity of the combustion space
in which the flame rod is provided or a discharge electrode for
ignition is provided. However, in the configuration provided with
the above installation spaces, combustion heat from the burner is
transmitted to the space which should not be heated, and is
radiated therefrom. This reduce efficiency of heat transmission to
the hydrogen generator to be heated. Further, the installation
space increases a size of the burner, and hence reduce a space
around the burner. As a result, the configuration around the burner
is difficult to design flexibly.
SUMMARY OF THE INVENTION
[0010] The present invention has bee made under the circumstances,
and an object of the present invention is to provide a burner
capable of accurately detecting a flame in combustion of a fuel gas
containing a low content of hydrocarbon based combustible
substance. Another object of the present invention is to provide a
burner capable of efficiently heating an object to be heated while
inhibiting heat radiation to an object other than the object to be
heated, and having a compact configuration with flexibility
increased around the burner.
[0011] According to the present invention, there is provided a
burner having a fuel distributor configured to inject a fuel
supplied from a fuel supply device; and an air injector placed such
that the air injector surrounds the fuel distributor so as to form
a combustion space around the fuel distributor and having an air
injection hole through which air supplied from an air supply device
is injected, the air injected from the air injection hole and the
fuel injected from the fuel distributor being combusted to allow a
flame to be generated in the combustion space, the burner
comprising a temperature detector for detecting a temperature of
the combustion space, the temperature detector having a temperature
detecting portion located within the air injection hole or in an
air flow passage of the combustion space; and a flame detector for
detecting a condition of the flame within the combustion space,
based on the temperature detected by the temperature detector.
[0012] In accordance with such a configuration, since the flame
condition is detected by detecting the temperature within the
combustion space using the temperature detector, the flame can be
detected accurately and correctly regardless of the type of the
fuel gas in combustion using a fuel gas containing a low content of
hydrocarbon based combustible substance.
[0013] The temperature detector may be placed such that the
temperature detecting portion is located within the air injection
hole or within the combustion space in the vicinity of the air
injection hole.
[0014] In accordance with such a configuration, since the
temperature detecting portion is located within the air injection
hole or within the combustion space in the vicinity of the air
injection hole, the temperature detecting portion is not heated up
to the temperature as high as that of the combustion space.
Therefore, the temperature detector can detect the temperature
within a heat-resistance limit, and degradation of the temperature
detector due to heat can be avoided. In addition, since the
temperature detector is placed so as to protrude slightly into the
combustion space, detection of the temperature within the
combustion space can be carried out without disturbing the flame
generated within the combustion space. These effects are remarkable
in the configuration in which the temperature detector is placed
such that the temperature detecting portion is located within the
air injection hole.
[0015] The temperature detector may be placed so as to penetrate
the air injector.
[0016] It is preferable that the temperature detecting portion of
the temperature detector is thermally insulated from an inner face
of the air injection hole.
[0017] In accordance with such a configuration, since the
temperature detecting portion of the temperature detector is placed
to be thermally insulated from the air injection hole, temperature
variation within the combustion space can be detected smoothly
without being affected by the air injector.
[0018] It is preferable that a gap is formed between the
temperature detector and the inner face of the air injector, and a
width of the gap is substantially uniform over an outer periphery
of the temperature detector.
[0019] In accordance with such a configuration, the temperature
detector is thermally insulated from the air injection hole by the
air layer existing within the gap. In addition, since flow of air
toward the combustion space is formed within the air layer, the
temperature detecting portion of the temperature detector can be
cooled quickly by the flow of the air when the flame has vanished.
This follows that vanishment of the flame can be detected
immediately. In particular, since uniform flow of air is formed in
the air layer in the structure in which the width of the air layer
is substantially uniform over the entire outer periphery of the
temperature detector, the air can be supplied stably and combustion
state can be stabilized.
[0020] It is preferable that the air injector has a plurality of
air injection holes, and a cross-sectional area of the gap between
the air injection hole within which the temperature detector is
provided and the temperature detector is substantially equal to a
cross-sectional area of the air injection hole within which the
temperature detector is not provided.
[0021] In accordance with such a configuration, disorder of an
injection state of the air which is caused by provision of the
temperature detector within the air injection hole, can be
inhibited, and the air can be injected through the air injection
hole within which the temperature detector is provided, as in other
air injection holes. Thereby, the flame can be generated in proper
balance and stably.
[0022] The temperature detector may have the temperature detecting
portion at an end portion thereof, and a body of the temperature
detector is contained within the air injector.
[0023] In accordance with such a configuration, the space in which
the temperature detector is installed is unnecessary. This makes it
possible to avoid heat radiation to such an installation space, and
hence efficiently heat an object to be heated. Further, the burner
can be small-sized, and flexibility of the configuration around the
burner can be improved.
[0024] An end portion of the temperature detecting portion side of
the temperature detector may be substantially covered with an
oxidation film.
[0025] When using the temperature detector whose end portion is not
covered with the oxidization film, the oxidization film is formed
by combustion, so that the temperature varies due to the
oxidization film. On the other hand, by using the temperature
detector whose one end portion is covered with the oxidization
film, accuracy of detection can be improved because variation in
the detected temperature due to formation of the oxidization film
does not occur.
[0026] An end portion of the temperature detecting portion side of
the temperature detector may be substantially hemispherical.
[0027] In accordance with such a configuration, the temperature
detector can be cooled quickly by the smooth flow of the air along
the outer periphery of the tip end when combustion by the burner
stops. During combustion, the temperature detector is subjected to
heat radiation, which makes it easy to detect a temperature
increase. Therefore, accuracy of detection is improved.
[0028] The temperature detector may be a sheath-shaped thermo
couple.
[0029] Thereby, the configuration of the present invention can be
easily achieved.
[0030] A plurality of temperature detectors may be provided at
different positions within the combustion space to detect
temperatures of different regions within the combustion space.
[0031] In accordance with such a configuration, since a plurality
of temperature detectors can detect temperatures in different
regions of the combustion space, detection of the flame can be
carried out more correctly and accurately. In particular, by
comparing the flame conditions in the regions of the combustion
space to each other, detection of the abnormal combustion can be
carried out accurately and smoothly. Therefore, combustion is
stopped immediately under the abnormal combustion condition, and as
a result, discharge of CO and abnormally-high temperature condition
can be avoided.
[0032] The combustion space may have a cross-sectional area that
increases toward a flame radiation direction.
[0033] In accordance with such a configuration, combustion is
stably performed in each region of the combustion space according
to a combustion amount in a wide range.
[0034] The burner may further comprise an electrode contained
within the fuel distributor and having an end portion that
protrudes into the combustion space; and an ignition circuit
electrically connected to the electrode, for applying a voltage to
the electrode to allow electric discharge from the electrode to
occur within the combustion space.
[0035] In accordance with such a configuration, by applying a
voltage to the electrode to allow electric discharge to occur
between the fuel distributor or the air injector and the electrode,
ignition can take place. Since the electrode is contained within
the fuel distributor, a space for installing the ignition means
becomes unnecessary. Because of the absence of such an installation
space, heat radiation to the space can be avoided, and the object
to be heated can be heated efficiently. In addition, the burner can
be small-sized and flexibility of the configuration around the
burner can be improved.
[0036] The burner may further comprise a switch configured to
perform switching so that the electrode is connected to the
ignition circuit during ignition, and the electrode is connected to
the flame detector when the flame detector judges that ignition has
occurred based on temperature information of the combustion space
from the temperature detector, wherein the flame detector detects
the flame based on the temperature information from the temperature
detector and detects the flame based on an output current from the
electrode.
[0037] In accordance with such a configuration, concurrently with
the flame detection using the temperature detector, the
conventional flame detection using the electrode can be carried
out. Therefore, the flame can be detected more accurately and
correctly. Such a configuration is easily achieved without
significant change, because the electrode as the ignition means can
be used to detect the flame,
[0038] The end portion of the electrode that protrudes into the
combustion space may be placed in a region different from a region
of the combustion space in which the temperature detector is
placed, to detect the flame in the region different from the region
where the flame is detected by the temperature detector.
[0039] In accordance with such a configuration, the temperatures of
different regions in the combustion space can be detected more
correctly and accurately by using the temperature detector and the
electrode. In particular, by comparing the flame conditions in the
regions of the combustion space to each other, detection of the
abnormal combustion can be carried out easily, accurately and
smoothly. Therefore, combustion is stopped under abnormal
combustion condition, and as a result, discharge of CO and
abnormally-high temperature condition can be avoided.
[0040] The temperature detector may detect the flame in an upper
region of the combustion space in the flame radiation direction,
and the electrode may detect the flame in a lower region of the
combustion space in the flame radiation direction.
[0041] In accordance with such a configuration, the flame can be
detected in both of the upper and lower regions of the combustion
space, a state in which ignition is detected in the upper region
but ignition is not detected in the lower region, and ignition is
not detected in the upper region but ignition is detected in the
lower region, can be detected as the abnormal combustion
condition.
[0042] According to the present invention, there is provided a
hydrogen generator comprising a burner having the above
configuration, and a reformer for generating a reformed gas
containing hydrogen by a reforming reaction of a hydrocarbon based
material, wherein the burner is configured to heat the
reformer.
[0043] In accordance with such a configuration, since the burner
having the configuration is used, the flame can be detected
accurately and correctly even when the gas containing a low content
of hydrocarbon based combustible substance is used as the fuel gas
for the burner. The hydrogen generator having such a configuration
can generate the flame stably regardless of the type of the fuel
gas while detecting the flame.
[0044] According to the present invention, there is provided a fuel
cell power generation system comprising the hydrogen generator
having the above configuration, and a fuel cell configured to
generate a power, using a gas containing hydrogen as a major
component which is supplied from the hydrogen generator to a fuel
electrode and an oxidizing gas supplied to an oxidizing
electrode.
[0045] In accordance with the above configuration, since the
above-described effects are obtained in the hydrogen generator, the
off-gas or the generated gas containing hydrogen as a major
component, is combusted as the fuel gas by the burner to generate
heat for the reforming reaction. Consequently, it is possible to
achieve a system in which power generation efficiency is high and
burden on environment is less.
[0046] The above and further objects and features of the invention
will more fully be apparent from the following detailed description
with accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] FIG. 1 is a cross-sectional view schematically showing a
configuration of a burner according to a first embodiment of the
present invention;
[0048] FIG. 2 is a partially enlarged cross-sectional view
schematically showing placement of a temperature detector in FIG.
1;
[0049] FIG. 3 is a partially enlarged plan view schematically
showing placement of the temperature detector in FIG. 2;
[0050] FIG. 4 is a cross-sectional view schematically showing a
configuration of a burner according to an alternative example of
the first embodiment;
[0051] FIG. 5 is a cross-sectional view schematically showing a
configuration of a burner according to a second embodiment of the
present invention;
[0052] FIG. 6 is a cross-sectional view schematically showing a
configuration of a burner according to a third embodiment of the
present invention;
[0053] FIG. 7 is a cross-sectional view schematically showing a
configuration of a burner according to a fourth embodiment of the
present invention;
[0054] FIG. 8 is a view schematically showing a configuration of a
fuel cell power generation system according to a fifth embodiment
of the present invention; and
[0055] FIG. 9 is a view showing operation data of a hydrogen
generator in the fuel cell power generation system according to the
fifth embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0056] Hereinafter, preferred embodiments of the present invention
will be described with reference to the accompanying drawings.
[0057] (Embodiment 1)
[0058] FIG. 1 is a cross-sectional view schematically showing a
configuration of a burner according to a first embodiment of the
present invention. FIG. 2 is a partially enlarged cross-sectional
view schematically showing placement of a temperature detector in
FIG. 1, and FIG. 3 is a partially enlarged plan view schematically
showing placement of the temperature detector in FIG. 2.
[0059] As shown in FIG. 1, the burner comprises a fuel distributor
1 provided with a plurality of fuel injection holes 8, an air
injector 2 provided with a plurality of air injection holes 9, and
a temperature detector 6 contained and placed within the air
injector 2. A space surrounded by an inner peripheral wall 2B of
the air injector 2 is a combustion space (or combustion chamber) 3.
The temperature detector 6 detects temperature of the combustion
space 3.
[0060] The air injector 2 is cylindrical and are configured to open
at both ends. The air injector 2 is hollow and its internal shape
is such that the inner peripheral wall 2B is inclined, thereby
forming an inverted-frustum-cone shaped space in which a
cross-sectional area of an inner hole of a cylinder increases
toward an opening at the upper end (exit from which the flame
radiates). In other words, the inner peripheral wall 2B forms a cup
shape. The cup-shaped space corresponding to the inner hole of the
air injector 2 forms the combustion space 3 in which the flame is
generated and combustion is performed. The air injector 2 has a
hollow cylindrical peripheral wall portion. The peripheral wall
portion is configured such that an inner space 20 is formed by an
outer peripheral wall 2A, the inner peripheral wall 2B, an upper
end wall 2C, and a lower end wall 2D, and surrounds the combustion
space 3 in the circumferential direction. The inner space 20 of the
air injector 2 communicates with the combustion space 3 through the
plurality of air injection holes 9 arranged both in the
circumferential direction and in a vertical direction of the air
injector 2. The inner space 20 has an air supply port 31 provided
in the outer peripheral wall 2A, and an air supply device 5
provided outside is connected to the air supply port 31. The air
supply device 5 has an air blower (not shown) such as a pump or a
fan, and is configured to supply air for combustion to the air
injector 2 while adjusting its flow rate. The flow rate of air
supply is adjusted by controlling an operation of the air blower,
or by controlling a flow rate adjuster provided downstream of the
air blower such as a valve in a supply system.
[0061] The air injector 2 is, for example, made of metal. The air
injector 2 has a heat capacity larger than that of a temperature
detector 6 mentioned later, because of its large volume. As shown
in FIG. 2, the air injection holes 9 (9A and 9B) that are circular
and have predetermined diameters are formed in the inner peripheral
wall 2B forming the combustion space 3 at predetermined intervals.
Here, the air injection holes 9 are comprised of one air injection
hole 9A having a diameter D1 of 2.0 mm and a number of air
injection holes 9B having a diameter D2 of 1.2 mm. And, the
temperature detector 6 is provided within the air injection hole
9A. The temperature detector 6 is configured such that a
temperature detecting portion (not shown) provided at a tip end
thereof slightly protrudes into the combustion space 3 to face the
combustion space 3 and to be located in flow of the air. And, a
body of the temperature detector 6 extends through the inner space
20 of the air injector 2 and through a penetrating hole 32 formed
in a lower end wall 2D and its base end protrudes outside. The
temperature detector 6 is supported by a support member (not
shown), and sealing is created by a seal member (not shown) between
the penetrating hole 32 of the air injector 2 and the temperature
detector 6 in order to inhibit leakage of air. Here, as the
temperature detector 6, a sheath-shaped thermocouple having a
diameter of 1.6 mm is used. The tip end portion including the
temperature detecting portion (not shown) is covered with an
oxidization film 16. By covering the tip end portion with the
oxidization film 16, the temperature within the combustion space 3
can be detected accurately as described later. The temperature
detector 6 is placed so as not to be in contact with an inner face
of the air injection hole 9A, and hence, there is a gap between the
temperature detector 6 and the inner face of the air injection hole
9A. As shown in FIG. 3, the temperature detector 6 is placed
concentrically within the circular air injection hole 9A. Thereby,
a width L of the annular air layer 17 formed on an outer periphery
of the temperature detector 6 (i.e., distance between the inner
peripheral face of the air injection hole 9A and an outer
peripheral face of the temperature detector 6) is substantially
uniform over the entire outer periphery of the temperature detector
6. In the structure of the air injection hole 9A within which the
temperature detector 6 is placed, a cross-sectional area of a
portion as an air flow passage (i.e., air layer 17) is
substantially equal to that of the air injection hole 9B, and the
air flow passage having the uniform width L is formed on the outer
periphery of the temperature detector 6. Instead of the thermo
couple, for example, a thermistor or the like may be used as the
temperature detector 6. The temperature detector 6 is connected to
a flame detector 7 provided outside of the burner.
[0062] The combustion space 3 has a cross-sectional area that
decreases from the upper portion (an exit from which the flame is
radiated) toward a lower portion thereof. A fuel distributor 1 is
fitted to the lower portion of the combustion space 3. The fuel
distributor 1 is pipe-shaped and its upper end is closed. The fuel
distributor 1 is placed such that an upper end portion provided
with a plurality of fuel injection holes 8 arranged in the
circumferential direction protrudes into a center portion of the
combustion space 3 having a circular cross-section and a lower end
thereof is connected to the fuel gas supply device 4 provided
outside. The fuel gas supply device 4 is configured to supply the
fuel gas containing a combustible gas to the fuel distributor 1
while adjusting the flow rate of the fuel gas, and has the blower
(not shown) such as the pump or the fan. The flow rate of the fuel
gas is adjusted by controlling an operation of the air blower, or
by controlling a flow rate adjustor provided downstream of the air
blower such as the valve in the supply system.
[0063] Subsequently, an operation of the burner during combustion
will be described.
[0064] As indicated by an arrow in FIG. 1, the fuel gas is supplied
from the fuel gas supply device 4 to the fuel distributor 1.
Further, the fuel gas is injected from the fuel distributor 1 into
the combustion space 3 through the fuel injection hole 8. As
defined herein, the fuel gas supplied from the fuel gas supply
device 4 refers to a combustible gas containing hydrogen as a major
component. As described later in an fifth embodiment (FIG. 8), as
the fuel gas, a generated gas which is generated during start of
the hydrogen generator in the fuel cell power generation system, or
the off-gas of the fuel cell, may be used.
[0065] Meanwhile, air is supplied from the air supply device 5 to
the air injector 2. As indicated by arrows in FIG. 1, the air is
introduced into the inner space 20 of the air injector 2, and is
injected into the combustion space 3 through the air injection
holes 9. At this time, the flow rates of the air being injected
from both of the holes 9A and 9B are substantially equal, because
the cross-sectional areas of the air flow passages of the air
injection holes 9A and 9B are substantially equal. Therefore,
disorder of an air injection state of the air due to placement of
the temperature detector 6 within the air injection hole 9A is
minimized, and disorder of a combustion state is inhibited. In
addition, since the air flow passage having the uniform width L is
formed on the outer periphery of the temperature detector 6 as
described above, the air is injected substantially uniformly from
the air injection hole 9A in the outer peripheral region of the
temperature detector 6. Therefore, disorder of the injection state
of the air is further inhibited, and the disorder of the combustion
state is further inhibited.
[0066] The fuel gas and the air which are thus supplied to the
combustion space 3 are mixed therein. And, ignition is performed
using an ignition device (not shown) such as gathering coal or a
heater. The fuel gas and the air are reacted to be combusted in the
combustion space 3, thereby generating a flame 10. As described
above, since the air is supplied from the air injection holes 9A
and 9B at substantially equal flow rate, the flame 10 can be
generated stably and in proper balance. And, as indicated by an
arrow, heat emitted from the generated flame is transmitted to an
object to be heated. Thus, by supplying the fuel gas and the air
independently to be combusted within the combustion space 3,
combustion is carried out stably without back flow of the flame in
the supply system, which occurs in the conventional configuration
in which the mixture of the combustible fuel gas and the air is
supplied to and combusted in the combustion space 3.
[0067] During the combustion, the condition of the flame is
detected using the temperature detector 6 to know whether or not
ignition, flame vanishment, or abnormal combustion has occurred.
Hereinbelow, how the flame is detected will be described.
[0068] Upon the flame 10 being generated within the combustion
space 3, the temperature within the combustion space 3 which had
normal temperature, increases, and hence, the temperature detector
6 detects the increased temperature. At this time, the temperature
detector 6 is not directly exposed to the flame of the combustion
space 3, because the temperature detecting portion (not shown) at
the tip end thereof is located within the air injection hole 9A of
the air injector 2, and the body thereof is contained within the
inner space 20 of the air injector 2. For this treason, during
combustion, the temperature of the temperature detector 6 does not
increase to a high temperature (about 1000.degree. C.) up to which
the temperature of the combustion space 3 increases. Under this
condition, the temperature detector 6 is placed under the
temperature within a heat-resistant limit, and degradation thereof
is avoided. In addition, since the temperature detector 6 protrudes
only slightly into the combustion space 3, the temperature within
the combustion space 3 can be detected without disturbing the flame
generated within the combustion space 3.
[0069] In addition, since the temperature detecting portion (not
shown) at the tip end of the temperature detector 6 faces the
combustion space 3, the temperature within the combustion space 3
can be detected accurately and smoothly. It should be noted that
the tip end at which the temperature detecting portion is provided
is not directly in contact with the inner face of the air injection
hole 9A, and is thereby thermally insulated from the air injector 2
because of the presence of the air layer 17 formed around the
temperature detector 6. Accordingly, the temperature detector 6 can
detect variation in the temperature within the combustion space 3
without being affected by the variation in the temperature of the
inner peripheral wall 2B of the air injector 2. In other words,
since the temperature of the temperature detecting portion of the
temperature detector 6 increases more quickly than the temperature
of the inner peripheral wall 2B of the air injector 2 having a
large heat capacity increases, the ignition can be detected
smoothly, accurately, and correctly.
[0070] Temperature information of the combustion space 3 detected
by the temperature detector 6 is transmitted to the flame detector
7 in the form of an electric signal. Upon reception of the electric
signal, the flame detector 7 judges whether or not the flame 10 has
been generated within the combustion space 3 (i.e., ignition has
occurred) based on the temperature variation in the combustion
space 3. To judge whether or not the ignition has occurred, it may
be judged whether or not the detected temperature of the combustion
space 3 is higher than a predetermined temperature, or otherwise,
it may be judged whether or not temperature increasing rate per
unit time is higher than a predetermined temperature increasing
rate.
[0071] If the flame has vanished for some reasons, then the
temperature of the combustion space 3 which was kept high is
rapidly reduced. Correspondingly, the temperature detected by the
temperature detector 6 is reduced. The reduced temperature
information of the combustion space 3 is transmitted to the flame
detector 7 in the same manner as described above. Upon reception of
the electric signal, the flame detector 7 judges whether or not the
flame 10 has vanished within the combustion space 3 based on the
temperature variation. To judge whether or not the flame 10 has
vanished, it may be judged whether or not the detected temperature
of the combustion space 3 is lower than a predetermined
temperature, or otherwise, it may be judged whether or not
temperature reducing rate per unit time is higher than a
predetermined temperature reducing rate. As described above, since
the air layer 17 is formed in the gap between the temperature
detecting portion of the temperature detector 6 and the inner face
of the air injection hole 9A, the temperature of the temperature
detector 6 is reduced quickly soon after the flame 10 has vanished
without being affected by the air injector 2. Especially, in the
air layer 17 formed between the temperature detector 6 and the
inner face of the air injection hole 9A, the air flows toward the
combustion space 3 by supply of the air, and the temperature
detector 6 is located in the flow of air. By the flow of the air,
the temperature detector 6 is cooled quickly, and the temperature
of the temperature detecting portion of the temperature detector 6
is reduced rapidly when heating stops after the flame 10 has
vanished. Therefore, it is possible to detect vanishment of the
flame 10 in a short time after the flame 10 has vanished.
[0072] In accordance with the flame detecting method described
above, since the flame 10 can be detected based on the temperature
variation within the combustion space 3 regardless of a current
value during combustion unlike in the conventional method. As a
result, even in the combustion using the fuel gas that is difficult
to detect by the conventional detecting method using the flame rod,
or the like, i.e., the fuel gas containing a low content of
hydrocarbon based combustible substance, the flame condition can be
detected accurately and correctly.
[0073] As described above, since the tip end on the temperature
detecting portion (not shown) side of the temperature detector 6 is
covered with the oxidation film 16, the temperature within the
combustion space 3 can be detected more accurately as compared to
the detecting method using the temperature detector without the
oxidation film. The reason for this will be described below. In the
case where the temperature detector which is not covered with the
oxidation film is used, the tip end of the temperature detector is
oxidized by the combustion within the combustion space 3, and in
time, the oxidation film is formed. In this case, the temperature
detected by the temperature detector 6 varies due to formation of
the oxidization film. On the other hand, in the case where the
oxidation film 16 is formed on the tip end of the temperature
detector 6 as described above, the variation in the detected
temperature can be avoided. Therefore, the flame can be detected
more accurately.
[0074] Furthermore, in the above configuration, since the
combustion space 3 is cup-shaped, i.e., inverted-frustum-cone
shaped to have the cross-section that increases toward the upper
portion (flame radiation exit), the flame 10 can be generated
stably and in proper balance according to a combustion amount in a
wide range. Specifically, in the case where the flow rate of a
mixture gas of the fuel gas and the air as a combustion source is
small and hence the amount of combustion is correspondingly small,
the flow rate and combustion speed of the mixture gas are balanced
in a region of the combustion space 3 having a
small-cross-sectional area. The size of the flame is determined by
the balance between the flow rate and combustion speed (reaction
rate of the combustion reaction) of the mixture gas as the
combustion source. When the amount of combustion is thus small
under the condition in which the combustion speed is constant, a
flame 10A is generated in substantially the lower region of the
combustion space 3. On the other hand, when the flow rate of the
mixture gas is high and hence the amount of combustion is
correspondingly large, the mixture gas flow rate and the combustion
speed are balanced in a region of the combustion space 3 that has a
large cross-sectional area. Therefore, in this case, a flame 10B is
generated in substantially the upper region of the combustion space
3. Thus, the cup-shaped combustion space 3 enables stable
combustion in a wide range of combustion amount. The air injector 2
having the cup-shaped combustion space 3 is easily constituted by
one component by press forming or drawing. Here, the flame is
defined as a highest-temperature portion at a boundary between the
region where combustion is being performed and the region where
combustion is not performed. In other words, the flame is an
outermost portion of the generated flame.
[0075] Further, since the temperature detector 6 is placed to be
contained within the air injector 2, a space for installing the
temperature detector becomes unnecessary unlike the conventional
method using the flame rod as the temperature detector. That is, an
installation space need not be provided around the burner. Since
heat radiation from the installation space is avoided, the object
to be heated can be heated efficiently. The size of the burner can
be reduced because of the absence of such an installation space. As
a result, the flexibility of the configuration around the burner
can be greatly improved.
[0076] The hole diameter of the air injection holes 9A and 9B, the
diameter of the temperature detector 6, and the shapes of these are
only illustrative and are not intended to be limited to those
described above. In addition, the cross-sectional areas of the air
injection holes 9A and 9B are not necessarily equal, but may be
different from each other so long as the air layer 17 is formed
around the temperature detector 6. Furthermore, the width L of the
air layer 17 may be non-uniform. As an alternative example of this
embodiment, the combustion space 3 surrounded by the air injector 2
may be cylindrical to have a uniform cross-sectional area, instead
of the cup-shape shown in FIG. 1.
[0077] FIG. 4 is a partially enlarged cross-sectional view
schematically showing a configuration of the burner according to
the alternative example of the first embodiment. As shown in FIG.
4, the burner of this alternative example is substantially
identical in configuration to the burner in FIG. 1 except the
following respects.
[0078] In the burner of this alternative example, the tip end of
the temperature detecting portion (not shown) side of the
temperature detector 6 placed within the air injection hole 9A is
hemispherical. The tip end of such a shape is subjected to heat
radiation more than the tip end having a corner portion, and
therefore, allows the temperature increase caused by combustion to
be detected accurately by the temperature detector 6. The tip end
of such a shape is easily cooled by smooth air flow formed along a
smooth surface of the hemispherical shape, and upon vanishment of
the flame, the temperature of the tip end is rapidly reduced. So,
the vanishment of the flame can be detected accurately. As should
be appreciated from the foregoing, in accordance with the
configuration of this alternative example, the above effects can be
produced more efficiently.
[0079] (Embodiment 2)
[0080] FIG. 5 is a cross-sectional view schematically showing a
configuration of the burner according to a second embodiment of the
present invention. The burner of this embodiment is substantially
identical in configuration to the burner of the first embodiment
except that a plurality of temperature detectors are placed at
different positions in the combustion space.
[0081] In addition to the temperature detector 6 provided as
described in the first embodiment, in the second embodiment, a
temperature detector 60 is provided so as to be located lower than
the temperature detector 6. The temperature detector 60 is
connected to the flame detector 7 to allow temperature information
relating to a lower region of the combustion space 3 detected by
the temperature detector 60 to be transmitted to the flame detector
7 in the form of an electric signal. As in the temperature detector
6, the temperature detector 60 is configured such that a tip end of
the temperature detecting portion (not shown) side is covered with
the oxidation film 16. Also, as in the temperature detector 6, the
temperature detecting portion (not shown) is located within the air
injection hole 9 to be in the air flow, and an air layer having a
uniform width is formed on an outer periphery of the temperature
detector 60. Therefore, in accordance with the temperature detector
60, the temperature of the lower region of the combustion space 3
can be detected accurately and correctly as in the temperature
detector 6. In addition, as in the first embodiment, the
temperature of the upper region of the combustion space 3 can be
detected accurately and correctly by the temperature detector 6.
Thus, temperatures of different regions of the combustion space 3,
i.e., the upper region and the lower region are respectively
detected, and ignition states of these regions are compared to
another. Thereby, in particular, abnormal combustion can be
detected easily and correctly. When it is judged that the abnormal
combustion has occurred, for example, supply of the fuel gas from
the fuel gas supply device 4 is stopped to cause combustion to
stop. Thus, discharge of CO due to abnormal combustion or
degradation of devices including the burner due to elevated
temperature, can be avoided. Hereinbelow, how the abnormal
combustion is detected will be described in detail.
[0082] First, in the case where combustion is performed normally,
and a flame 11C is thereby generated, the temperature of the
combustion space 3 becomes substantially uniform. So, the
temperature detected by the temperature detector 6 provided in the
upper region of the combustion space 3 (in the vicinity of the exit
of the combustion space 3) becomes substantially equal to the
temperature detected by the temperature detector 60 provided in the
lower region of the combustion space (in the vicinity of the fuel
distributor 1), and the flame detector 7 judges that ignition has
occurred in both of the upper and lower regions of the combustion
space 3. So, in this case, it is confirmed that combustion is being
performed normally within the combustion space 3.
[0083] However, for example, if the combustion amount becomes too
large, or the amount of air supply is small for some reasons,
thereby causing the flame to be lifted to some degrees, abnormal
combustion takes place, and a flame 11B is generated in
substantially the upper region of the combustion space 3. The flame
11B causes the upper region of the combustion space 3 to be heated
greatly, thereby resulting in a temperature of this upper region
higher than normal. So, the temperature detected by the temperature
detector 6 provided in the upper region of the combustion space 3
becomes high. Conversely, the temperature detected by the
temperature detector 60 provided in the lower region of the
combustion space 3 becomes low because of absence of the flame.
Temperature information of the upper region of the combustion space
3 which has been detected by the temperature detector 6 and
temperature information of the lower region of the combustion space
3 which has been detected by the temperature detector 60 are
respectively transmitted to the flame detector 7, which judges
flame conditions based on these information. In this case, since it
is detected that the temperature of the upper region of the
combustion space 3 is higher than a predetermined value, based on
the temperature information from the temperature detector 6, the
flame detector 7 judges that that ignition has occurred in the
upper region of the combustion space 3. On the other hand, since it
is detected that the temperature of the lower region of the
combustion space 3 is lower than the predetermined value, based on
the information from the temperature detector 60, the flame
detector 7 judges that the flame has vanished in the lower region
of the combustion space 3. As a result, it is confirmed that the
flame 11B is abnormal.
[0084] If the combustion amount becomes too small, or the amount of
air supply becomes large for some reasons, abnormal combustion
takes place, and a small flame 11A is generated in the lower region
of the combustion space 3. The flame 11A causes the lower region of
the combustion space 3 to be heated greatly, thereby resulting in a
temperature of this lower region higher than normal. So, the
temperature detected by the temperature detector 60 provided in the
lower region of the combustion space 3 becomes high. Conversely,
the temperature detected by the temperature detector 6 provided in
the upper region of the combustion space 3 becomes low because of
absence of the flame. Thus, based on the temperature information of
the upper region of the combustion space 3 which has been detected
by the temperature detector 6 and the temperature information of
the lower region of the combustion space 3 which has been detected
by the temperature detector 60, the flame detector 7 judges the
condition of the flame 11A within the combustion space 3. In this
case, since it is detected that the detected temperature of the
upper region of the combustion space 3 is lower than a
predetermined value, based on the temperature information from the
temperature detector 6, the flame detector 7 judges that the flame
has vanished in the upper region of the combustion space 3. On the
other hand, since it is detected that the detected temperature of
the lower region of the combustion space 3 is higher than the
predetermined value, based on the temperature information from the
temperature detector 60, the flame detector 7 judges that ignition
has occurred in the lower region of the combustion space 3. As a
result, it is judged that the flame 11A is abnormal.
[0085] It should be noted that, the number of the temperature
detectors or placement of the same within the combustion space are
not intended to the above.
[0086] (Embodiment 3)
[0087] FIG. 6 is a cross-sectional view schematically showing a
configuration of a burner according to a third embodiment of the
present invention. The burner of this embodiment is substantially
identical in configuration to the burner of the first embodiment
except that an electrode 12 as an ignition means is provided within
the distributor 1.
[0088] More specifically, in this embodiment, the electrode 12 is
provided at the center of an inner hole of the fuel distributor 1
that is pipe-shaped and has a double-walled structure. The
electrode 12 is supported by a support member 15 fitted to the
inner hole of the fuel distributor 1, and a tip end of the
electrode 12 protrudes into the combustion space 3. The support
member 15 is made of ceramic or the like that is heat-resistant and
insulative. The protruding tip end portion of the electrode 12 is
bent in an arc shape toward the inner peripheral wall 2B of the air
injector 2. And, a base end of the electrode 12 penetrates through
a bottom wall of the fuel distributor 1 and protrudes to outside to
be electrically connected to an ignition circuit 13 provided
outside. A seal member (not shown) is filled in a gap between the
electrode 12 and the support member 15 and in a gap between the
inner peripheral wall of the fuel distributor 1 and the support
member 15.
[0089] In the above configuration, during ignition, the air is
injected from the air injection holes 9 of the air injector 2 into
the combustion space 3, and the fuel gas is injected from the fuel
injection hole 8 of the fuel distributor 1 into the combustion
space 3. Since the fuel distributor 1 has the double-walled
structure, the electrode 12 and the support member 15 provided
within the fuel distributor 1 do not inhibit the fuel gas from
being supplied from the fuel gas supply device 4 to the distributor
1 and from being injected from the fuel injection hole 8. Upon the
fuel gas and the air being supplied into the combustion space 3 and
mixed therein, a voltage from the ignition circuit 13 is applied to
the electrode 12. This causes electric discharge between the
electrode 12 and the inner peripheral wall 2B of the air injector
2. As a result, ignition takes place. Then, combustion is performed
and the flame is generated within the combustion space 3. At this
time, as in the first embodiment, the temperature detector 6
detects the temperature within the combustion space 3 and the flame
detector, detects the flame condition.
[0090] In accordance with the configuration of the second
embodiment, in addition to the effects provided by the
configuration of the first embodiment, effects described below is
obtained. In the configuration of the second embodiment, since the
electrode 12 functioning as the ignition means is contained in the
fuel distributor 1, the space for installing the ignition means
around the burner, for example, above the combustion space 3,
becomes unnecessary unlike the conventional configuration.
Therefore, heat radiation from the installation space is avoided
and the object to be heated can be heated efficiently. The size of
the burner can be reduced because of the absence of the
installation space. As a result, flexibility of the configuration
around the burner can be further improved.
[0091] While ignition is performed in such a manner that electric
discharge is caused to occur between the electrode 12 and the inner
peripheral wall 2B of the air injector 2, this may be performed by
electric discharge between the electrode 12 and the fuel
distributor 1. In this case, to facilitate the electric discharge
between the electrode 12 and the fuel distributor 1, it is
preferable that the tip end of the electrode 12 that protrudes into
the combustion space 3 is bent toward the fuel distributor 1. It
should be noted that the shape of the electrode 12 is not intended
to be limited to the above, that is, the electrode is not
necessarily bent.
[0092] (Embodiment 4)
[0093] FIG. 7 is a cross-sectional view schematically showing a
configuration of a burner according to a fourth embodiment of the
present invention. The burner of this embodiment is substantially
identical in configuration to the burner of the first embodiment
except that the ignition circuit 13 and the flame detector 7 are
connected in parallel to the electrode 12 through a switch 14. In
this configuration, switching is performed so that the electrode 12
is connected to the ignition circuit 13 in ignition and the
electrode 12 is connected to the flame detector 7 after detection
of ignition.
[0094] In ignition, the switch 14 performs switching so that the
electrode 12 is connected to the ignition circuit 13, and ignition
is carried out as in the third embodiment. Meanwhile, when the
ignition takes place and the flame is generated, the flame detector
7 detects ignition based on the temperature information of the
combustion space 3 which has been detected by the temperature
detector 6. Upon detection, the switch 14 performs switching so
that the electrode 12 is connected to the flame detector 7.
Thereby, the flame detector 7 detects the flame based on an output
current detected by the electrode 12 by the conventional flame
detecting method as well as the flame detecting method using the
temperature detector 6. Thus, the flame can be detected by two
methods using the temperature detector 6 and the electrode 12, and
hence the flame can be detected more accurately.
[0095] Here, the flame condition in the upper region of the
combustion space 3 can be detected by the temperature detector 6,
and the flame condition in the lower region of the combustion space
3 can be detected by the electrode 12 with tip end thereof placed
in the lower region within the combustion space 3 that is lower
than the tip end of the temperature detector 6. By detecting the
flame conditions in plurality of different regions within the
combustion space 3, the abnormal combustion condition can be
detected as in the second embodiment.
[0096] First, in the case where combustion is performed normally,
and a flame 11C is thereby generated, the flame detector 7 judges
that the ignition has occurred in the upper region of the
combustion space 3, based on the temperature detected by the
temperature detector 6 provided in the upper region of the
combustion space 3 (vicinity of the exit of the combustion space
3). Concurrently with detection by the temperature detector 6, the
output current from the electrode 12 placed in the lower region of
the space 3 (in the vicinity of the fuel distributor 1) is detected
and the detected current value is converted into a voltage value.
Based on whether or not the voltage value is larger than a
threshold voltage, it is judged whether or not ignition has
occurred. In this case, since the flame is formed in the lower
region of the combustion space 3, the output current becomes large,
and hence, the voltage is larger than the threshold voltage. So,
the flame detector 7 judges that the ignition has occurred in the
lower region of the combustion space 3. Thus, since it is judged
that ignition has occurred in both of the upper and lower regions
of the combustion space 3, normal combustion is confirmed.
[0097] On the other hand, for example, if the combustion amount
becomes too large or the amount of air supply becomes small for
some reasons, thereby causing the flame to be lifted to some
degrees, abnormal combustion takes place, and a flame 11B is
generated in substantially the upper region of the combustion space
3. Such a flame 11B causes the upper region of the combustion space
3 to be heated greatly, thereby resulting in a temperature of this
upper region higher than normal. For this reason, the temperature
detected by the temperature detector 6 provided in the upper region
of the combustion space 3 becomes high. Based on this, the flame
detector 7 judges that ignition has occurred in the upper region of
the combustion space 3. Conversely, the output current from the
electrode 12 placed in the lower region of the combustion space 3
is not detected because of absence of the flame in the lower region
of the combustion space 3, and therefore, the voltage value into
which the current value has been converted becomes smaller than the
threshold voltage. From this, the flame detector 7 judges that the
flame has vanished in the lower region of the combustion space 3.
And, from these judgment as to ignition in the upper and the lower
regions of the combustion space 3, the abnormal combustion
condition has been confirmed.
[0098] Further, for example, the combustion amount becomes too
small, or the amount of air supply becomes large for some reasons,
abnormal combustion condition occurs, and a small flame 11A is
generated in the lower region of the combustion space 3. When the
flame 11A is generated, the output current from the electrode 12 is
detected because of the presence of the flame. In this case, the
voltage value into which the detected current value has been
converted is larger than the threshold voltage, and based on this,
the flame detector 7 judges that ignition has occurred in the lower
region of the combustion space 3. On the other hand, the
temperature detected by the temperature detector 6 provided in the
upper region of the combustion space 3 becomes low because of
absence of the flame. Based on this temperature information, the
flame detector 7 judges that the flame has vanished in the upper
region of the combustion space 3. From judgment of ignition in the
upper and lower regions of the combustion space 3, the abnormal
combustion state is confirmed.
[0099] In the first to fourth embodiments, the temperature
detecting portion of the temperature detector is placed within the
air injection hole, but this is only illustrative. For example, a
temperature detector made of a heat-resistant material may extend
further into the combustion space. More specifically, the
temperature detector may be placed differently from those in the
first to fourth embodiments, so long as it is thermally insulated
from a burner component around it and is exposed to an air flow
injected from the air injection hole. It should be noted that, if
the tip end of the temperature detecting portion of the temperature
detector is set back to a considerable degree from the interface
between the air injection hole 9 and the combustion space 3, or is
located between the outer wall and the inner wall of the air
injector, the temperature within the combustion space cannot be
detected accurately, correctly, and smoothly. It is therefore
necessary to place the temperature detecting portion of the
temperature detector at a location to enable temperature variation
in the combustion space to be detected immediately, i.e., at least
face the combustion space 3.
[0100] In the second to fourth embodiments, the tip end of the
temperature detecting portion side of the temperature detector is
shaped to have a corner portion. Alternatively, as in the case of
the alternative example of the first embodiment, the tip end of the
temperature detector may be hemispherical.
[0101] (Embodiment 5)
[0102] FIG. 8 is a view schematically showing a configuration of a
fuel cell power generation system comprising a hydrogen generator
including the burner of the present invention. As shown in FIG. 8,
a fuel cell power generation system 10 comprises a fuel cell 53 and
a hydrogen generator 52 as major components. The fuel cell 53 has
the conventional structure.
[0103] The hydrogen generator 52 comprises a burner 50, a reformer
51, and a CO shifter 54. As the burner 50, the burner described in
the first to fourth embodiments is used. The reformer 51 and the CO
shifter 54 have the conventional structures. Within the reformer
51, CH.sub.4 as the fuel gas is supplied, and a reforming reaction
is conducted as represented by a reaction formula. Since the
reforming reaction needs to be carried out at a temperature as high
as 650 to 700.degree. C., in the hydrogen generator 52, the burner
50 heats the reformer 51. The reformed gas generated through the
reforming reaction in the reformer 51 is supplied to the CO shifter
54. In the CO shifter 54, CO is removed from the reformed gas by
the reaction represented by a reaction formula in FIG. 8. Thus, in
the reformer 51 and the CO shifter 54, a hydrogen-rich gas
containing H.sub.2 as a major component is generated, and is
supplied to the fuel cell 53 as the fuel gas. In the hydrogen
generator 52, the hydrogen-rich gas (generated gas) containing
large amount of CO is generated during start of the generator.
However, such a generated gas cannot be used in the fuel cell 53
because CO degrades the electrode of the fuel cell 53. For this
reason, such a gas is supplied to the burner 50 of the hydrogen
generator 52 as the fuel gas. Although the generated gas contains
large amount of CO, the operation of the reformer 51 is controlled
so that the conversion rate of CH.sub.4 into H.sub.2 and CO.sub.2
in the reforming reaction becomes high, and therefore, the
percentage of unconverted hydrocarbon based combustible substance
contained in the generated gas is low and the content of H.sub.2
contained in the generated gas is high.
[0104] The hydrogen-rich gas generated in the hydrogen generator 52
is supplied to the fuel cell 53, where reaction is conducted using
the hydrogen-rich gas and oxygen contained in the air as
represented by a reaction formula in FIG. 7, thereby generating a
power. An electric energy derived from the fuel cell 53 is used for
various purposes. On the other hand, the off-gas containing H.sub.2
which remains unused after the reaction, which is included in the
hydrogen-rich gas supplied to the fuel cell 53, is supplied to the
burner 50 of the hydrogen generator 52 and used as the fuel gas of
the burner 50.
[0105] Hereinbelow, a flame detecting operation in the hydrogen
generator 52 in the fuel cell power generation system 100 (FIG. 8)
including the burner 50 of the fourth embodiment in FIG. 7 will be
described with reference to FIG. 9.
[0106] FIG. 9 is a view showing operation data of the hydrogen
generator 52 in the fuel cell power generation system 100 of this
embodiment. As shown in FIG. 9, a graph A represents time-series
variation in temperature of the reformer 51 of the hydrogen
generator 52, graph B represents time-series variation in
temperature of the combustion space 3 detected by the temperature
detector 6, and graph C represents time-series variation in the
voltage value into which the output current value from the
electrode 12 (FIG. 7) has been converted.
[0107] As shown in the graph A, when the fuel cell power generation
system 100 starts and the burner 50 is ignited, the temperature of
the reformer 51 increases after a lapse of a predetermined time
after ignition because of its large heat capacity. And, after a
lapse of several minutes, the temperature of the reformer 51
increases to a predetermined value (about 650 to 700.degree. C.)
and is kept at this temperature.
[0108] On the other hand, as shown in the graph B, when the burner
50 is ignited, temperature variation within the combustion space 3
can be detected by the temperature detector 6, and the detected
temperature gradually increases just after the voltage value of the
electrode 12 increases as described later. Then, after a lapse of
time, and a predetermined temperature is reached, the detected
temperature becomes constant.
[0109] As shown in the graph C, since the generated gas containing
a high content of hydrocarbon based combustible substance (or
off-gas) is supplied to the burner 50 during ignition, the voltage
value into which the output current value from the electrode 12 has
been converted increases in a moment of time. As described above,
this voltage value is affected by a composition of the generated
gas, and hence varies as described below with a lapse of an
operation time. Until the reformer 51 reaches the predetermined
temperature, a conversion rate in the reforming reaction gradually
increases, and the concentration of hydrogen contained in the
generated gas which is obtained from the reformer 51 gradually
increases. Correspondingly, the content of the hydrocarbon based
combustible substance contained in the generated gas gradually
decreases. As a result, the voltage value of the electrode 12
decreases regardless of the increase in the temperature of the
reformer 51. And, when the reformer 51 is kept at the predetermined
temperature, the voltage value becomes constant at a lower limit
value. In this case, if the conversion rate in the reformer 51 is
increased in order to generate a large amount of hydrogen in the
hydrogen generator 52, the voltage value is further reduced.
[0110] As should be appreciated from the above, in the hydrogen
generator 52, the flame can be detected by the conventional flame
detecting method based on the voltage value of the electrode 12
during ignition and a predetermined period thereafter. In
particular, during ignition, because of high responsivity to
ignition, the flame can be detected more accurately than detection
by the temperature detector 6. However, when the temperature of the
reformer 51 increases, thereby causing the conversion rate in the
reforming reaction to increase, detection using the electrode 12
becomes difficult under the influence of noises. Accordingly, the
flame is detected using the electrode 12 in ignition, and
thereafter, under the condition in which the gas containing low
content of hydrocarbon based combustible substance because the
conversion rate in the reformer 51 is high, is supplied to the
burner 50, the flame is detected using the temperature detector 6.
Thereby, generation of the flame can be detected as soon as
ignition takes place, and then, the flame condition can be detected
accurately under the condition in which combustion is performed in
the burner 50 using the gas containing low content of hydrocarbon
based combustible substance as the fuel gas.
[0111] In accordance with the above configuration, during operation
of the fuel cell power generation system 100, the flame can be
detected accurately in the hydrogen generator 52 regardless of the
composition of the fuel gas supplied to the burner 50. Therefore,
combustion is carried out by the burner 50 using the off-gas or the
generated gas as the fuel gas. As a result, it is possible to
achieve a power generation system using the off-gas or the
generated gas as the fuel, in which power generation efficiency is
high, burden on environment is small, and safety is high.
[0112] While the burner of the present invention is used for
heating the hydrogen generator in the fuel power generation system,
this may be used as a burner using the gas containing a low content
of combustible substances including compound at least containing
carbon and hydrogen as the fuel gas, for example, a burner for
heating a hot water supply device.
[0113] Numerous modifications and alternative embodiments of the
invention will be apparent to those skilled in the art in the light
of the foregoing description. Accordingly, the description is to be
construed as illustrative only, and is provided for the purpose of
teaching those skilled in the art the best mode of carrying out the
invention. The details of the structure and/or function may be
varied substantially without departing from the spirit of the
invention.
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