Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02352811 2001-07-10
A FUEL DISCHARGE MEMBER, A BURNER, A PREMIXING NOZZLE OF A
COMBUSTOR, A COMBUSTOR, A GAS TURBINE, AND A JET ENGINE
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a fuel discharge member that is preferably used to
reduce the amount of NOx exhaust, and a burner, a premixing nozzle of a
combustor, a
combustor, a gas turbine and a jet engine, which are equipped with this fuel
discharge
member.
2. Description of Related Art
A gas turbine and a jet engine each include a compressor, a combustor, and a
turbine. The compressor and the turbine are connected to each other by means
of a
main shaft. The combustor is connected to an outlet of the compressor.
A working fluid gas is compressed by the compressor in order to supply a
high-pressure gas to the combustor. The high-pressure gas is heated to a
predetermined
turbine inlet temperature by the combustor in order to supply a high-pressure
and
high-temperature gas to the turbine. The high-temperature and high-pressure
gas is
expanded in a cylinder of the turbine, as the high-temperature and high-
pressure gas
passes between a stator blade and a rotor blade disposed on the main shaft of
the turbine.
Thereby, the main shaft is rotated, so that a shaft output is generated. Since
a shaft
output can be obtained, wherein the consumption power of the compressor is
excluded,
the shaft output can be used as a driving source by connecting an electric
power
generator to the main shaft at the opposite side of the turbine, for example.
The jet engine uses the output in the form of kinetic energy of a high-
velocity jet
to directly propel an aircraft.
The development of the gas turbine and the jet engine described above has been
promoted in order to reduce the emissions of NOx and the like, in view of
recent
environmental problems. Particularly, various research and development related
to
combustors has been undertaken and is disclosed in Japanese Unexamined Patent
Application, First Publication No. Hei 8-54119, No. Hei 10-318541, No. Sho 60-
126521,
No. Hei 8-21627, No. Hei 9-119639, No. Hei 4-283316, and Japanese Examined
Patent
CA 02352811 2001-07-10
Application, Second Publication No. Hei 6-84817, for example.
In Japanese Unexamined Patent Application, First Publication No. Hei 8-21627,
a fuel nozzle, which is used during the entire operation of a gas turbine to
reduce
emissions of air pollutants in exhaust gas of the gas turbine, is disclosed.
In the
following, the fuel nozzle is described with reference to FIG. 11.
This fuel nozzle includes a housing 1 and a central tube 2, and an annular
chamber 3 is formed between the housing l and the central tube 2. Downstream
of the
central tube 2, an inner swirler 4 and an outer swirler 5 are disposed so as
to be connected
to the downstream side of the annular chamber 3. Downstream of the inner
swirler 4
and the outer swirler 5, a combustion area is provided.
In a diffusion combustion mode, when a fuel gas is supplied to the inner
swirler
4 from an aperture 2a that is provided near the front end of the central tube
2, a portion of
the air, which is supplied to the annular chamber 3, is mixed with the fuel
gas by the
inner swirler 4, so that diffusion flames are maintained in a diffusion mixing
cup 6
disposed at the downstream side of the inner swirler 4. On the other hand, the
remaining air which is supplied to the annular chamber 3, is led to the outer
swirler 5
after being separated from the air which is supplied to the inner swirler 4,
by means of a
splitter vane which extends circumferentially to form the dii~usion mixing cup
6. At the
upstream portion of the annular chamber 3, a plurality of spokes 7 protrude
toward the
inside of the annular chamber 3. In a premixing combustion mode, the fuel gas
is
supplied to the annular chamber 3 from apertures 7a of the spokes 7, and is
subsequently
mixed with the air which is supplied to the annular chamber 3. At that time,
the flow
passage of the fuel gas, which communicates with the aperture 2a to supply the
fuel gas
to the inner swirler 4, is shut, and thereby, the entire fuel gas is supplied
to the spokes 7.
In FIG. 11, a fuel source 6 and a fuel gas passage switching valve 9 are also
shown.
As described above, since the spokes 7 are disposed at the upstream side of
the
inner swirler 4 and the outer swirler 5, a fuel/air mixture in the premixing
combustion
mode is supplied to the inner swirler 4 and the outer swirler 5 from the
annular chamber
3, and is accelerated to a high-velocity swirl through an aerodynamic vane.
This
high-velocity swirl prevents the flashback of combustion from the combustion
zone into
the annular chamber 3. Therefore, the surface of the premixing flame is
stabilized, and
the entirety of air which is supplied from the compressor is used so as to be
mixed with
the fuel gas which is supplied from the spokes 7. Therefore, a lean fuel/air
ratio in the
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3
premixing combustion mode can be obtained, thereby reducing the amount of NOx
exhaust in the mid to high-load operating range of the turbine.
However, in recent gas turbines and jet engines, the combustion temperature in
the combustor tends to be set at a high temperature to improve the effciency
of the
combustion. Even in the premixing combustion mode described above, since the
range
of the concentration distribution of the premixed fuel is broad due to the
reasons
described below, a rich zone, wherein the fuel concentration (fuel/air ratio)
is greater than
1, is generated, so that NOx is generated in a high concentration in the rich
zone. Thus,
it is difficult to reduce the amount of NOx exhaust from the combustor.
Particularly, when the combustion temperature is raised to over approximately
1600°C, it is known that the concentration of NOx contained in the
combustion gas is
rapidly increased. Therefore, when the combustion temperature is set to become
near
1600°C in order to increase the efficiency of the combustion, even if
the range of the
concentration distribution of the fuel is relatively narrow, NOx may be easily
generated.
Therefore, it is desired to make the concentration of the premixed fuel
uniform in order
to improve efficiency of the gas turbine and the jet engine, and to reduce the
NOx
exhaust at the same time.
In the following, the reasons why the range of the concentration distribution
of
the fuel is broad in the premixing combustion mode are described. In this
case, the fuel
gas is supplied from the apertures 7a of the spokes 7 of which a comparatively
large
cross-sectional area protrudes into the air flow passage. Thereby, downstream
of the
spokes 7, a negative pressure zone is generated in the flow direction of the
air. Then,
the air flow is engulfed by the negative pressure area, so that swirls are
generated in the
negative pressure area. Due to the generation of swirls, the fuel gas can be
circumferentially supplied for a short time from the apertures 7a disposed
perpendicular
to the air flow passage, for example. That is, the fuel gas loses penetration
force
through the air flow. Therefore, the concentration distribution of the fuel
gas becomes
circumferentially nonuniform.
Japanese Unexamined Patent Application, First Publication No. Hei 8-21627,
No. Hei 10-318541, and No. Hei 9-119639 disclose spokes protruding in the air
flow
passage and a device that supplies a fuel gas from an aperture of a hollow
pole, for
example. However, the concentration distribution cannot be made uniform
according to
these prior art publications.
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4
SUMMARY OF THE INVENTION
The present invention has been made to solve the problems described above.
An object of the present invention is to provide a fuel discharge member,
which can be
operated with high effectiveness by setting a high-temperature of the
combustion, and to
reduce the amount of NOx exhaust at the same time, and is provided with a
burner, a
premixing nozzle, a combustor, a gas turbine, and a jet engine.
In order to achieve the object described above, the present invention utilizes
the
following constitution.
A fuel discharge member according to the present invention includes a main
body to be fixed on a fuel supply conduit. The fuel discharge member includes
a main
body which has an internal space that communicates with a fuel passage in the
fuel
supply conduit, fuel discharge outlets which communicated with the internal
space, and a
trailing edge. The thickness of the trailing edge may be no more than S mm, or
a flow
passage block ratio of the fuel discharge member may be no more than 10% of
the
cross-sectional area of the air flow passage in which the fuel discharge
member is to be
placed.
By the use of this fuel discharge member, since the thickness of the trailing
edge
is thin enough such that the flow passage block ratio of the fuel discharge
member is no
more than 10%, the efl'ective area of the air flow passage is enlarged, so
that the
generation of swirls is suppressed at the downstream side of the fuel
discharge member
with respect to the air flow.
Alternatively, the main body of the fuel discharge member may be a flat tube.
By the use of this fuel discharge member, since the projected area of the main
body in the
air flow direction is decreased, the effective area of the air flow passage is
increased, so
that the generation of swirls is suppressed at the downstream side of the fuel
discharge
member with respect to the air flow.
The fuel discharge member may be disposed so that the fuel discharge outlets
of
the main body open the perpendicular or approximately perpendicular to the air
flow
passage. In this case, the fuel is discharged by a strong penetration force
through the air
flow in which the generation of swirls is suppressed at downstream side of the
fuel
discharge member.
In the fuel discharge member, the trailing edge of the main body may be
inclined
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so that the base end of the trailing edge extends further downstream from the
tip end of
the trailing edge with respect to the air flowwhich is to be formed in the air
flow passage.
Thereby, the air flows in a radially outward direction along the trailing
edge, so that the
generation of a second flow, which may cause the generation of swirls, is
suppressed.
In this case, the trailing edge may be formed with a detachable inclined
member. Thus,
the fuel discharge member of which the trailing edge is inclined can be easily
manufactured.
In the fuel discharge member, the fuel discharge outlets may be disposed
axially
in a plurality of lines at radially staggered positions on both sides of the
main body.
Thereby, the fuel flow discharged from the respective fuel discharge outlets
can be made
uniform.
In the fuel discharge member, the fuel discharge outlets may open toward the
downstream direction so as to discharge the fuel in the downstream direction
of the fuel
discharge member with respect to the air flow. By the use of this fuel
discharge member,
it is possible to make the concentration distribution of the fuel uniform.
The cross-sectional shape of the fuel discharge member may be an elliptical
shape, a flat oval shape, or an annular shape. The trailing edge may be formed
with a
protruding portion at the downstream side with respect to the air flow.
A burner according to the present invention includes a fuel supply conduit in
which a fuel passage is formed so as to communicate with a fuel supply source;
the fuel
discharge member described above; and swirlers which are fixed on the fuel
supply
conduit so as to rotate an air flow or a premixed gas flow containing air and
fuel.
A plurality of fuel discharge members may be arranged axially in a plurality
of
lines on the fuel supply conduit. Thereby, the number of fuel discharge
outlets can be
increased without decreasing the effective area of the air flow passage.
The fuel discharge members may be disposed so that the fuel discharge
members are circumferentially displaced in relation to one another. In this
case, the
circumferential concentration distribution of the fuel can be made uniform.
The swirlers may be disposed downstream of the fuel discharge member with
respect to the air flow. The swirler and the fuel discharge member may be
arranged
circumferentially in the same line. In this case, since the turbulence of the
flow
velocities caused by the fuel discharge member interacts with the turbulence
of the flow
velocities caused by the swirler, the turbulence of the flow velocities caused
by the fuel
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6
discharge member downstream thereof can be prevented.
Alternatively, the swirlers may be disposed so that the swirler and the fuel
discharge member are circumferentially staggered with respect to each other.
In this
case, since the turbulence of the flow velocities are generated respectively
downstream of
the fuel discharge member and the swirler, the turbulence of the flow
velocities are made
approximately uniform downstream of the swirler.
The fuel supply conduit may further comprise a liquid fuel passage which
communicates with a liquid fuel supply source, and fuel discharge holes which
communicate with the liquid fuel passage substantially at the tip end portions
of the fuel
supply conduit.
This burner suppresses the generation of swirls downstream of the fuel
discharge member, so that the concentration distribution of the fuel can be
made uniform.
Thus, since the amount of fuel burned at a high fuel/air ratio, which causes
an increase in
the amount of NOx exhaust, is reduced, the amount of NOx exhaust can be
reduced.
A premixing nozzle of the combustor according to the present invention has a
pilot burner which is disposed on the central axis of the premixing nozzle,
and also has
the burners described above which are disposed as main burners surrounding the
pilot
burner.
Since the premixing nozzle of the combustor is provided with the burners which
suppress the generation of swirls downstream of the fuel discharge member, it
is possible
to make the concentration distribution of the fuel uniform. Therefore, the
amount of
fuel burned at a high fuel/air ratio, which causes an increase in the amount
of NOx,
exhaust is reduced, and the amount of NOx exhaust is reduced.
A combustor of the present invention has the premixing nozzle described above,
and a cylinder which holds the premixing nozzle therein.
Since this combustor includes the premixing nozzle which can suppress the
generation of swirls downstream of the fuel discharge member, it is possible
to make the
concentration distribution of the fuel uniform. Thereby, the amount of fuel
burned at a
high fuel/air ratio, which causes an increase in the amount of NOx exhaust, is
reduced,
and the amount of NOx exhaust is reduced.
A gas turbine of the present invention comprises a compressor which
compresses air to generate a high-pressure gas; the combustor described above,
which is
connected to the compressor so as to be supplied with the high-pressure gas
from the
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compressor, and which heats the high-pressure gas to generate a high-
temperature and
high-pressure gas; and a turbine which is connected to the combustor so as to
be supplied
with the high-temperature and high-pressure gas from the combustor, and which
rotates
an out shaft by expanding the high-temperature and high-pressure gas to
generate a shaft
output.
Since this gas turbine includes the combustor which can suppress the
generation
of swirls downstream of the fuel discharge member, it is possible to make the
concentration distribution of the fuel uniform. Thereby, the amount of fuel
burned at a
high fuel/air ratio, which causes an increase in the amount of NOx exhaust, is
reduced,
and the amount of NOx exhaust is reduced.
A jet engine of this present invention comprises a compressor which compresses
air to generate a high-pressure gas, the combustor described above, which is
connected to
the compressor so as to be supplied with the high-pressure gas from the
compressor, and
which heats the high-pressure gas to generate a high-temperature and high-
pressure gas,
and the turbine which is connected to the combustor so as to be supplied with
the
high-temperature and high-pressure gas from the combustor.
Since this jet engine includes the combustor which can suppress the generation
of swirls downstream of the fuel discharge member, it is possible to make the
concentration distribution of the fuel uniform. Thereby, the amount of fuel
burned at a
high fuel/air ratio, which causes an increase in the amount of NOx exhaust, is
reduced,
and the amount of NOx exhaust is reduced.
BRIEF DESCRIPTION OF DRAWINGS
FIGS. I A to 1 C show a burner comprising a fuel discharge member of a first
embodiment according to the present invention: FIG. 1 A is a cross-sectional
view of a
key portion of the burner; FIG. 1 B is a cross-sectional view of the fuel
discharge member
taken along the line A-A of FIG. 1 A; and FIG. 1 C is a cross-sectional view
of the burner
taken along the line B-B of FIG. 1 A.
FIG. 2 is a graph which shows the relationship between the flow passage block
ratio of a fuel discharge member and the NOx concentration.
FIGS. 3A to 3E show respective modified cross-sectional shapes of the fuel
discharge member of a first embodiment according to the present invention:
FIG. 3A is a
cross-sectional view of a first modification; FIG. 3B is a cross-sectional
view of a second
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g
modification; FIG. 3C is a cross-sectional view of a third modification; FIG.
3D is a
cross-sectional view of a fourth modification, and FIG. 3E is a cross-
sectional view of a
fifth modification.
FIG. 4A is a cross-sectional view of a key portion of a burner comprising a
fuel
discharge member of a second embodiment according to the present invention.
FIG. 4B
is a cross-sectional view of the fuel discharge member, which is taken along
the line C-C
of FIG. 4A.
FIGS. SA and SB show a modified fuel discharge member according to the
present invention: FIG. SA is a cross-sectional view, and FIG. SB is a cross-
sectional
view taken along the line D-D of FIG. SA.
FIG. 6 is a schematic representation which illustrates the action of the
second
embodiment shown in FIG. 4A.
FIGS. 7A and 7B show a fuel discharge member of a third embodiment
according to the present invention: FIG. 7A is a cross-sectional view of a key
portion of
the fuel discharge member, and FIG. 7B is a cross-sectional view taken along
the line
E-E of FIG. 7A.
FIGS. 8A and 8B show the relationship between the fuel discharge member and
swirlers of a fourth embodiment according to the present invention: FIG. 8A is
a
schematic representation which illustrates the relationship between the fuel
discharge
member and the main swirlers, wherein the fuel discharge member and the main
swirlers
are staggered; and FIG. 8B is a schematic representation which illustrates the
relationship
between the fuel discharge member and the main swirlers, wherein the fuel
discharge
member and one main swirler are arranged in the same line.
FIG. 9 is a cross-sectional view which shows a burner according to a fifth
embodiment of the present invention.
FIGS. 1 OA and 1 OB show a combustor including a fuel discharge member of the
present invention: FIG. l0A is a cross-sectional view of a key portion of the
combustor,
and FIG. 1 OB is a cross-sectional view of FIG. 10A.
FIG. 11 is a cross-sectional view which shows a combustor according to the
prior art.
DETAILED DESCRIPTION OF THE INVENTION
In the following, embodiments according to the present invention will be
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9
explained with reference to the drawings.
FIRST EMBODIMENT
A gas turbine expands a high-temperature and high-pressure gas in the turbine
and rotates the main shaft to generate a shaft output which is used as a
driving force for
an electric power generator and the like. A jet engine expands the high-
temperature and
high-pressure gas in the turbine and rotates the main shaft to exert kinetic
energy of a
high-velocity jet (exhaust), discharged from an outlet of the turbine, as a
propelling force
of an aircraft.
The main components of the gas turbine and the jet engine are a compressor, a
combustor, and a turbine.
The compressor compresses a gas, that is air, which is introduced from an
inlet
thereof, as a working fluid in order to supply a high-pressure gas to the
combustor that is
connected to the outlet of the compressor. This compressor used is an axial
compressor
which is connected to the turbine through the main shaft. In the combustor,
the
high-pressure gas is burned to generate a high-temperature and high-pressure.
Then, the
high-temperature and high-pressure gas is supplied to the turbine.
In the following, the combustor according to a first embodiment is described
with reference to FIGS. l0A and l OB.
A combustor 10 is equipped with a premixing nozzle 12 along a central axis of
an internal cylinder 1 I . The internal cylinder 11 is a circular cylinder of
which both
ends open. The premixing nozzle 12 includes a pilot burner 13 and a plurality
of main
burners 14. The pilot burner 13 is provided at the central position which
coincides with
the central axis of the premixing nozzle 12. The plurality of main burners 14
are
disposed at even intervals so as to surround the pilot burner 13. Therefore,
the central
axis of the pilot burner 13 is the central axis of the internal cylinder 11.
In FIG. l OB,
eight main burners 14 are disposed so as to surround the pilot burner 13,
wherein the
main burners 14 each have the same form.
The pilot burner 13 of the premixing nozzle 12 includes a pilot fuel tube 15
and
pilot swirlers 16. The pilot fuel tube 15 is a circular cylinder of which one
end is
connected to a fuel supply source which is not shown, so that pilot fuel is
supplied to the
pilot fuel tube 15 from the fuel supply source. At the other end of the pilot
fuel tube I 5,
a pilot fuel nozzle 1 Sa is formed so as to open toward a combustion chamber l
Oa of the
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combustor 10 which is formed on the internal cylinder 11. Thus, the pilot fuel
is
supplied to the combustion chamber 1 Oa from the pilot fuel nozzle 1 Sa. The
pilot
swirlers 16 have a twisted shape, and are fixed on the pilot fuel tube 15 at
even intervals
in the circumferential direction. In FIG. l OB, the pilot swirlers 16 are
disposed on the
pilot fuel tube 15 at intervals of 45° in the circumferential
direction. The pilot swirlers
16 give a swirling motion to the air flow (shown by an arrow) which passes
through the
pilot swirlers 16. Thereby, the air flow is emitted to the surroundings of the
pilot fuel
nozzle 15a.
The pilot fuel supplied from the pilot fuel nozzle 1 Sa burns the swirled flow
of
air as combustion gas to generate flames in the combustion chamber 10a. Thus,
flames
generated by the pilot burners 13 are used to generate flames at the main
burner 14.
The main burner 14 of the premixing nozzle 12 includes a fuel supply conduit
17, fuel discharge members 20, and swirlers 18. The fuel supply conduit 17 is
a circular
cylinder in which a fuel passage is formed. One end of the fuel supply conduit
17 is
connected to a fuel supply source, which is not shown, in order to supply main
fuel to the
fuel supply conduit 17. The other end of the fuel supply conduit 17 is closed.
The fuel
discharge members 20 are fixed on the fuel supply conduit 17 at even intervals
in the
circumferential direction. The fuel discharge member 20 includes a main body
having
an internal space which communicates with the fuel supply conduit 17, and fuel
discharge outlets 21 which communicate with the internal space, so as to
discharge the
main fuel into the air flow. The swirlers 18 have a twisted shape, and are
fixed on the
fuel supply conduit 17 at even intervals in the circumferential direction. In
FIG. l OB,
the swirlers 18 are disposed on the fuel supply conduit 17 at intervals of
45° in the
circumferential direction. The swirlers 18 are disposed downstream of the fuel
discharge members 20. The swirlers 18 give a swirling motion to the air flow
passing at
the peripheral portion of the fuel supply conduit 17. In FIG. l OB, eight main
burners 14
contact each other and surround the pilot burner 13.
Thus, the main burners 14 discharge the main fuel gas, which is introduced
through the fuel supply conduit 17 to a fuel discharge outlet 21, into the air
flow from the
fuel discharge outlet 21. Thereby, the fuel gas and the air are premixed, so
that a
premixed gas is generated. When the premixed gas passes through the swirlers
18, the
premixed gas is swirled by the swirlers 18, and subsequently emitted to the
combustion
chamber l0a of the combustor 10. The premixed gas is led to the surroundings
of the
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11
pilot burner 13 from the eight main burners 14 in the combustion chamber 10a.
The
premixed gas is ignited by the flames generated by the pilot burner 13
described above,
so that a high-temperature gas is generated. The generated gas is emitted from
an
aperture which is disposed at one end of the internal cylinder 11.
An external cylinder 19 is disposed on the outer side of the internal cylinder
11.
The external cylinder 19 is a circular cylinder of which one end is opened. At
the other
end of the external cylinder 19, an introductory passage of the air flow is
formed so as to
reverse the air flow direction.
In the following, the burner used as the main burner 14 according to the first
embodiment will be explained in further detail.
FIG. I A shows the burner including the fuel supply conduit 17, the fuel
discharge members 20, and the swirlers 18. The fuel discharge member 20
includes the
main burner 14, the fuel supply conduit 17, the swirlers 18, and the fuel
discharge outlets
21.
As shown in FIG. 1 A, the fuel discharge members 20 are fixed on the fuel
supply conduit 17 and radially protrude into the air flow passage (shown by an
arrow).
The fuel discharge member 20 includes a main body 23 having an internal space
22, fuel
discharge outlets 21, and a trailing edge 23a. The tip end of the main body 23
is closed,
and the base end of the main body 23 communicates with the fuel passage in the
fuel
supply conduit 17 through the internal space 22. The internal space 22 is
formed so as
to communicate with the fuel passage in the fuel supply conduit 17 at the base
end of the
internal space 22. In FIG. lA, two fuel discharge outlets 21 are centrally
aligned at
opposite sides of the main body 23, respectively. The fuel discharge outlets
21 open
toward a perpendicular or almost perpendicular direction to the air flow
passage. The
fuel discharge outlets 21 are formed so as to communicate with the internal
space 22.
However, the number of fuel discharge outlets 21 formed in the main body 23 is
not
limited to two, and the relationship between the fuel discharge outlets 21 is
also not
limited such that they are aligned.
In FIG. 1 B, the main body 23 used is a flat tube of which the cross-sectional
shape is a flat oval shape. The flat oval shape has two opposite linear
portions disposed
parallel to each other and both tip ends of the opposite linear portions are
connected to
each other forming semicircular portions, as shown in FIG. 1 B. The thickness
t of the
main body 23 in a direction perpendicular to the air flow passage is set to be
no more
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than 5 mm or to be thin enough such that the flow passage block ratio thereof
(the ratio
of the cross-sectional area, wherein the trailing edge 23a of the fuel
discharge member 23
occupies the air flow passage, to the total cross-sectional area of the air
flow passage) is
no more than 10%. As a result, the thickness of the trailing edge 23a of the
main body
23 becomes thin.
In FIG. 1 C, four fuel discharge members 20 are disposed at intervals of
90° in
the circumferential direction. The swirlers 18 are disposed at intervals of
45° in the
circumferential direction downstream of the fuel discharge members 20, with
respect to
the flow of the air. The swirlers 18 have a twisted shape.
As described above, since the thickness t of the trailing edge 23a of the main
body 23 is set to be no more than 5 mm or to be thin enough such that the flow
passage
block ratio thereof is no more than 10%, an interrupted effective area of the
air flow
passage, wherein the air flow is interrupted by the fuel discharge member 20
fixed on the
fuel supply conduit, is decreased, so that the flow of the premixed gas is
made uniform.
Thus, a negative pressure area, caused by the interruption of the flow of the
premixed gas
by the fuel discharge member 20 and formed downstream of the trailing edge
23a, is
decreased, so that the generation of swirls caused by the negative pressure
area, wherein
the air flow is entrained, is reduced.
Thereby, the turbulence of the velocity distribution of the air flow is
decreased
at the downstream side of the fuel discharge member 20. Thus, since the
penetration
force of the fuel gas discharged from the fuel discharge outlet 21 can be
maintained
approximately constantly, the concentration distribution of the fuel gas in
the premixed
gas can be constantly maintained in spite of the quality or the quantity of
the fuel gas in
the premixed gas.
Since four fuel discharge members 20 are disposed at intervals of 90°
in the
circumferential direction and the plurality of fuel discharge outlets 21 are
disposed
respectively on both sides of the fuel discharge members 20, the
circumferential
concentration distribution of the fuel gas is made uniform. Moreover, since
two fuel
discharge outlets 21 are disposed radially in a line on the opposite sides of
the fuel
discharge member 20, the radial concentration distribution of the fuel gas is
made
uniform. The number of fuel discharge members 20 and the arrangement of the
fuel
discharge members 20 may be suitably decided.
In FIG. 2, experimental results show the relationship between the flow passage
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13
block ratio of the fuel discharge members 20 and the concentration of NOx
exhausted.
When the flow passage block ratio of the fuel discharge members 20 is
increased, the
concentration of NOx exhausted is also increased.
In the United States, the concentration of NOx exhausted is restricted to be
no
greater than 25 ppm. According to the experimental results shown in FIG. 2,
the flow
passage block ratio of the fuel discharge members 20 may be set to no more
than 10 % to
satisfy the restriction of the concentration described above. When the flow
passage
block ratio of the fuel discharge members 20 is set to 7%, the concentration
of NOx
exhausted is 9 ppm.
The cross-sectional shape of the main body 23 described above may be another
modified shape other than the flat oval shape shown in FIG. 1 B.
In a first modification shown in FIG. 3A, a flat tube, wherein the cross-
sectional
shape is a flat oval shape, is used, and two fuel discharge outlets 21 are
disposed on both
sides and staggered with respect to each other in the direction of the air
flow, that is, in
the axial direction of the fuel supply conduit 17. Thus, interaction between
the fuel
discharge outlets 21 can be reduced, so that the fuel gas is constantly
supplied.
In a second modification shown in FIG. 3B, a flat tube, wherein the
cross-sectional shape is an elliptical shape, is used, and the opposite sides
in which the
fuel discharge outlets 21 are disposed, are curved.
In a third modification shown in FIG. 3C, the trailing edge 23a is formed with
a
protruding portion 24 disposed on the end of the trailing edge side of the
first
modification. In this case, the protruding portion 24 may be formed into a
semicircle of
which the radius R is small enough so that the thickness t of the trailing
edge 23a is no
more than 5 mm or the flow passage block ratio of the fuel discharge member is
no more
than 10% with respect to the cross-sectional area of the air flow passage in
which the fuel
discharge member 20 is to be placed. Thereby, the internal space 22 of the
main body
23 has a large cross-sectional shape, so that a large flow of the fuel gas can
be easily
maintained. Moreover, the generation of swirls at the downstream side is
prevented, so
that the fuel concentration distribution can be made uniform.
In a fourth modification shown in FIG. 3D, protruding portions 24 and 25 are
disposed at opposite sides to form the trailing edge 23a and a leading edge of
the fuel
discharge member 20 according to the second modification, and thereby, the
generation
of swirls downstream of the fuel discharge member 20 is satisfactorily
prevented.
CA 02352811 2001-07-10
14
These protruding portions 24 and 25 may be disposed in another type of fuel
discharge
member of which the cross-sectional shape is a flat oval shape or a circular
shape, for
example.
In a fifth modification shown in FIG. 3E, the trailing edge 23a is thin enough
such that the thickness of the trailing edge 23a is no more than 5 mm or the
flow passage
block ratio of the fuel discharge member 20 is no more than 10% (R < 2.5 mm).
The
cross-sectional shape of the main body 23 is a wing shape, and the cross-
sectional shape
of the internal space 22 is an elliptical shape. In this case, the generation
of swirls is
suppressed as described above.
The cross-sectional shape of the internal space 22 is not limited to an
elliptical
shape, and may be a flat oval shape or an annular shape.
SECOND EMBODIMENT
In the following, a burner including a fuel supply conduit 17, a fuel
discharge
member 30, and swirlers 18 of the second embodiment will be explained with
reference
to FIGS. 4A. and 4B. In this case, the same members as those of the first
embodiment
are indicated by the same reference numbers, and descriptions of the same
members are
omitted.
In FIG. 4A, fuel discharge members 30 and swirlers 18 are fixed on the fuel
supply conduit 17.
The fuel discharge member 30 including a main body 33 having fuel discharge
outlets 31, an internal space 32, and a trailing edge 33a is shown. In this
embodiment,
the trailing edge 33a is inclined so that the base end of the trailing edge
33a extends
further downstream from the tip end of the trailing edge 33a with respect to
the air flow
which is to be formed in the air flow passage. That is, the shape of the fuel
discharge
member 30 as viewed from the side is a tail assembly shape.
The internal space 32 communicates with the fuel passage in the fuel supply
conduit 17 at the base end of the internal space 32. In the main body 33, the
fuel
discharge outlets 31 open toward a direction perpendicular to the air flow
passage and
communicate with the internal space 32. In FIG. 4A, on the opposite sides of
the main
body 33, two fuel discharge outlets 31 are arranged along an angular line with
respect to
the air flow and are staggered axially with respect to each other. Thus, four
fuel
discharge outlets 31 are disposed on the respective main bodies 33 so as to be
axially
CA 02352811 2001-07-10
displaced in relation to one another.
In this case, the main body 33 used is a flat tube wherein the cross-sectional
shape is a flat oval shape of which both opposite sides are parallel to each
other and both
tip ends are connected to each other forming a curve, as shown in FIG. 4B. The
thickness t of the main body 33 in a direction perpendicular to the air flow
passage is set
to be no more than 5 mm or to be thin enough such that the flow passage block
ratio of
the fuel discharge member is no more than 10% with respect to the cross-
sectional area
of the air flow passage in which the fuel discharge member 20 is to be placed.
In this
case, the thickness of the trailing edge 33a of the main body 33 becomes thin.
In FIG. 4A, four fuel discharge members 30 are disposed at intervals of
90° in
the circumferential direction and protrude radially, and swirlers 18 are
disposed at
intervals of 45° in the circumferential direction downstream of the
fuel discharge
members 30 with respect to the air flow.
The cross-sectional shape of the main body 33 is not limited to the flat oval
shape described above, and may be the cross-sectional shapes shown in FIGS. 3A
to 3E,
respectively.
As shown in FIG. SA, the trailing edge 33a may be formed with a detachable
inclined member 34 of which the lateral shape is a triangle, so that the
trailing edge 33a
is inclined. This construction makes it easy to manufacture the fuel discharge
member
30 of which the trailing edge 33a is inclined.
In the following, the effects of the fuel discharge member 30, of which
trailing
edge 33a is inclined, will be explained with reference to FIG. 6.
In general, a negative pressure area is formed downstream of the fuel
discharge
member 33, and thereby, the air flow is swirled. In contrast, when the
trailing edge 33a
of the fuel discharge member 30 is inclined as shown in FIG. 6, the air flows
from the
base end of the fuel discharge member 30 along the incline of the trailing
edge 33a, so
that the air flow is prevented from being swirled. Thus, the concentration
distribution
of the fuel gas can be made uniform.
Since the fuel discharge member 30 is a flat tube, the fuel discharge outlets
31
are staggered axially. That is, one of the fuel discharge outlets 31,
positioned axially
upstream with respect to the air flow, is disposed near the tip end of the
fuel discharge
member 30. The other of the fuel discharge outlets 31, positioned axially
downstream
with respect to the air flow, is arranged near the base end of the fuel
discharge member
CA 02352811 2001-07-10
16
30. The fuel gas can be uniformly discharged from both fuel discharge outlets
31 which
are axially staggered. Therefore, even if the number of fuel discharge outlets
31 is
increased, the radial penetration force is made uniform. Moreover, the radial
concentration distribution of the fuel gas can be made uniform by inclining
the trailing
edge 33a as described above. The circumferential concentration distribution
can be
easily made uniform by increasing the number of fuel discharge members 30 and
fuel
discharge outlets 31.
THIRD EMBODIMENT
In the third embodiment, the fuel discharge members 30 are disposed on the
fuel
supply conduit 17 in a plurality of lines along the axial direction of the
fuel supply
conduit 17 (along the flow direction of the air). In FIG. 7A, the fuel
discharge members
30 are axially arranged in two lines.
In this case, a fuel discharge member 30A located upstream and a fuel
discharge
member 30B located downstream may be arranged at the same position
circumferentially
and protrude radially. Alternatively, the fuel discharge members 30A and 30B
may be
staggered circumferentially as shown in FIG. 7B.
When the plurality of fuel discharge members 30 are respectively arranged at
the
same positions circumferentially as described above, the effective area of the
air flow
passage in which the plurality of fuel discharge members 30 are to be placed
hardly
changes compared to the effective area in which only one fuel discharge member
30 is to
be placed. Therefore, the number of fuel discharge outlets 31 to be disposed
can be
increased while maintaining the effective area of the air flow passage, and
the
circumferential concentration distribution of the fuel gas can be made
uniform.
When the plurality of fuel discharge members 30 are staggered
circumferentially,
the interval which circumferentially separates the fuel discharge outlets 31
from each
other becomes small, in accordance with the increase in the number of fuel
discharge
outlets 31. Therefore, the circumferential concentration distribution of the
fuel gas can
be made more uniform.
FOURTH EMBODIMENT
In the fourth embodiment shown in FIGS. 8A and 8B, the relationship between
the fuel discharge member 30 and the swirlers 18 is described.
CA 02352811 2001-07-10
17
In FIG. 8A, the fuel discharge member 30 and the swirlers 18 are staggered
circumferentially. That is, the fuel discharge member 30 is disposed upstream
of a
position which is located between the adjacent swirlers 18. In this case, the
intensity of
the turbulence of flow velocity v' is enlarged in accordance with the
proximity to the fuel
discharge member 30, as shown in FIG. 8A. The fuel gas is engulfed in swirls
generated at downstream of the fuel discharge member 30, so that the fuel gas
becomes
concentrated. In contrast, the intensity of the turbulence of flow velocity v"
is
generated downstream of the swirlers 18, as shown in FIG. 8A. The turbulence
of flow
velocity v" interacts with the turbulence of flow velocity v', so that the
distribution of the
turbulence of the flow velocity becomes uniform at downstream of the swirlers
18.
Then, a premixed gas, wherein the fuel gas is discharged into the air, is
mixed by this
uniform turbulence of the flow velocity, so that the concentration
distribution of the fuel
gas becomes uniform.
In FIG. 8B, the fuel discharge member 30 and one of the swirlers 18 are
aligned
circumferentially. That is, the fuel discharge member 30 is located
circumferentially
upstream of the swirlers 18. In this case, positions of the turbulence of flow
velocity v'
caused by the fuel discharge member 30 and the turbulence of flow velocity v"
caused by
the swirlers 18 are circumferentially consistent with each other, so that
ef~'ects caused by
the fuel discharge member 30 at the downstream side can be suppressed. That
is, the
turbulence of the flow velocity caused by the fuel discharge member 30 is
substantially
negligible.
FIFTH EMBODIMENT
In FIG. 9, a burner 14A including a fuel supply conduit 40, fuel discharge
members 30, and swirlers 18 according to the fifth embodiment is shown. In the
fuel
supply conduit 40, a fuel passage (not shown), a liquid fuel passage (not
shown), and fuel
discharge outlets 41 are formed. The fuel passage is formed so as to
communicate with
a fuel gas supply source to supply the fuel gas to the fuel discharge members
30. The
liquid fuel passage is formed so as to communicate with a liquid fuel supply
source to
supply liquid fuel to the fuel discharge outlets 41. The fuel discharge
outlets 41 are
formed so as to communicate with the liquid fuel passage substantially at the
tip end
portions of the fuel supply conduit 40. The fuel discharge outlets 41 open
toward the
downstream direction of the swirlers 18 with respect to the air flow.
CA 02352811 2001-07-10
1 i~
By the use of this burner 14A, premixed gas, wherein the concentration of the
fuel gas is uniform, can be formed in the same manner as described above.
As described above, by using the fuel discharge member 20 or 30, the
concentration distribution of the fuel gas in the premixed gas, wherein air
and fuel gas
are mixed, can be made circumferentially and radially uniform, so that the
area, wherein
the concentration of the fuel gas is high, that is, the fuel/air ratio is over
1, can be
reduced.
When the concentration distribution of the fuel gas is made uniform, even if
the
temperature for the combustion is raised to near 1600°C, the amount of
NOx generated
during the combustion can be reduced. Thus, by using a burner having a fuel
discharge
member, a premixing nozzle having a burner, and a combustor having a premixing
nozzle,
the total amount of NOx generated can be reduced. Moreover, a gas turbine and
a jet
engine, which include a burner, a premixing nozzle, and a combustor, can
reduce the
amount of NOx generated, even if the temperature for the combustion is raised
to operate
with high effectiveness. Particularly, when the trailing edge of the fuel
discharge
member 20 or 30 is set to be thin enough such that the thickness thereof is no
more than
mm or the flow passage block ratio of the fuel discharge member is no more
than 10%
with respect to the cross-sectional area of the air flow passage in which the
fuel discharge
member is to be placed, the generation of NOx can be considerably reduced.
Although the fuel discharge outlets 21 and 31 are respectively disposed in the
fuel discharge members 20 and 30 perpendicular or approximately perpendicular
to the
air flow passage, the fuel discharge outlets according to the present
invention may be
disposed downstream of the fuel discharge members with respect to the
direction of the
air flow.
Although the swirlers 18 are preferably disposed downstream of the fuel
discharge members 20 or 30, the swirlers may be disposed upstream of the fuel
discharge
members.
Although the fuel discharge members are disposed in the main burner of the
premixing nozzle in the respective embodiments described above, the fuel
discharge
members may be disposed in a pilot burner.
Although the combustor 10, the premixing nozzle 12, the main burner 14, the
gas turbine, and the jet engine include the fuel discharge member according to
the present
invention, configurations of the combustor 10, the premixing nozzle 12, the
main burner
CA 02352811 2001-07-10
19
14, the gas turbine, and the jet engine are not limited to the configurations
described in
the respective embodiments. That is, the number of pilot burners 13 and main
burners
14 disposed in the premixing nozzle 12 or the number of fuel discharge members
protruding from the main burner 14 may be suitably selected, for example.
It is understood, by those skilled in the art, that the foregoing description
is a
preferred embodiment of the disclosed configurations and that various changes
and
modifications may be made to the invention without departing from the spirit
and scope
thereof.
The following effects can be obtained by the present invention.
By using the fuel discharge member of which the thickness at the trailing edge
is
no more than S mm or the flow passage block ratio of the fuel discharge member
is no
more than 10% with respect to the cross-sectional area of the air flow passage
in which
the fuel discharge member is to be placed, the generation of swirls downstream
of the
fuel discharge member is reduced, so that the concentration distribution of
the premixed
gas including air and fuel is made uniform. Therefore, the total amount of NOx
exhaust
can be reduced, even if the temperature for the combustion is raised.
By using a flat tube as the fuel discharge member, the generation of swirls
downstream of the fuel discharge member is reduced, so that the concentration
distribution of the premixed gas including air and fuel is made unifrom.
Moreover, the
number of fuel discharge outlets can be increased, and the fuel discharge
outlets can be
suitably disposed. Thereby, the concentration distribution can be made
radially and
circumferentially uniform.
By using the burner, the premixing nozzle, and the combustor, the
concentration
distribution of the premixed gas including air and fuel is made uniform.
Therefore, the
total amount of NOx exhaust can be reduced, even if the temperature for the
combustion
is raised.
By using the gas turbine or the jet engine, since the concentration
distribution of
the premixed gas is uniformly maintained, the total amount of NOx exhaust can
be
reduced, even if the temperature for the combustion is raised. Thus, highly
effective
operation and the reduction of the amount of NOx exhaust can be achieved at
the same
time.
