Technical Field
[0001] The present invention relates to a gas turbine combustor. More particularly, the
present invention relates to a gas turbine combustor configured to generate an air
swirl flow inside a premixing tube connected to and communicated with a combustion
cylinder, and to secure a region where straight flows of air and fuel are generated
so as to prevent deterioration in durability of the combustion cylinder by stably
retaining a flame at an appropriate position in the combustion cylinder, and simultaneously,
to realize stabilization of combustion and low emission.
Background Art
[0002] Japanese Unexamined Patent Application Publication No.
2009-198054 discloses a gas turbine combustor 1 provided with a combustion cylinder 2, a premixing
tube 3, and a fuel supply unit 5. The gas turbine combustor 1 is configured to allow
the fuel supply unit to supply the fuel to an annular fuel passage 16 along a tangential
direction so that the fuel is uniformly injected through an annular nozzle portion
19. The injected fuel is atomized by air from a circumferential air passage 22 that
surrounds the nozzle portion, and an axial flow is generated in the combustor. Meanwhile,
air flowing inside through holes 25 in a peripheral wall surface of the premixing
tube generates a swirl flow that surrounds the axial flow within the combustor. As
a result, the flame is retained at a position apart from a top portion of the combustion
cylinder so that a heat shield plate 6 is not excessively heated, resulting in improved
durability. The resultant gas turbine combustor has durability higher than that of
generally employed type, and improved emission characteristics.
[0003] However, the aforementioned generally employed gas turbine combustor has a difficulty
in stabilization of the flame resulting from the swirl flow supplied inside through
the holes formed in the peripheral wall surface of the premixing tube, which intrudes
the premixing tube toward the center to disturb uniformity of the axial flow at the
center part of the premixing tube.
[0004] The nozzle employed in the generally employed gas turbine combustor also has a problem
of insufficient shear force to atomize the liquid film of the air blasted fuel fed
from the filmer because the straight air flow only exists around the fuel liquid film.
[0005] It is an object of the present invention to prevent an excessive increase in the
flow velocity of the straight flow component by avoiding a decrease in the cross-section
area of the straight flows of air and fuel in the premixing tube so that the flame
is stably retained at an appropriate position in the combustion cylinder to prevent
deterioration in durability of the combustion cylinder by the heat, and atomize the
fuel irrespective of the air flow for realization of stabilized combustion and low
emission.
[0006] The present invention in its various aspects is as claimed in the claims
[0007] A first aspect of the present invention provides A gas turbine combustor which includes
a combustion cylinder that combusts a mixture of fuel and air for supply of a combustion
gas to a turbine, a premixing tube that mixes the fuel and air supplied from one end
side and supplies the mixture into the combustion cylinder from the other end side,
and a fuel supply unit attached to the one end side of the premixing tube for supply
of the fuel into the premixing tube, wherein, therein a peripheral wall of the premixing
tube, a plurality of holes, through which the air is allowed to flow, are formed along
a tangential direction of the peripheral wall, and inside the premixing tube, with
a cylindrical inner wall provided apart from the peripheral wall at a predetermined
interval, a cylindrical gap having one end side closed and the other end side communicated
with the combustion cylinder is defined between the premixing tube and the inner wall.
[0008] A second aspect of the present invention is the gas turbine combustor according to
the first aspect wherein an inner circumferential surface of the inner wall has a
straight cylindrical shape.
[0009] A third aspect of the present invention is the gas turbine combustor according to
the second aspect wherein the fuel supply unit is a pressure injection nozzle of hollow
cone type, which injects the fuel in a hollow conical shape.
[0010] A fourth aspect of the present invention is the gas turbine combustor according to
the third aspect wherein the other end side of the premixing tube is protruded into
the combustion cylinder.
[0011] A fifth aspect of the present invention is the gas turbine combustor according to
the fourth aspect wherein an axial length of the premixing tube is set so that the
fuel conically injected through the pressure injection nozzle is not brought into
contact with the other end side of the premixing tube.
[0012] A sixth aspect of the present invention is the gas turbine combustor according to
the fifth aspect wherein an air flow channel is formed around the pressure injection
nozzle.
[0013] The gas turbine combustor according to the first aspect is configured so that air
flowing inside through the holes formed in the peripheral wall of the premixing tube
forms a swirl flow in a cylindrical gap between the peripheral wall and the inner
wall so as to be fed into the combustion cylinder. Air and fuel are supplied from
one end side of the premixing tube into an inner space of the inner wall, which are
formed into a mixture. The mixture forms the uniform straight flow along the axial
direction of the inner wall over an entire region inside the inner wall under no influence
of interference of the swirl flow, and is supplied into the combustion cylinder for
combustion. The straight flow of the mixture in the premixing tube secures the uniform
cross section area as the one inside the peripheral wall without any disturbance of
the uniform axial flow at the center of the premixing tube owing to intrusion of the
air swirl flow through the holes in the peripheral wall of the premixing tube. Therefore,
the flame is stably retained at the appropriate position in the combustion cylinder
so as to prevent deterioration in durability of the combustion cylinder by the heat
and to realize stabilized combustion and low emission.
[0014] The inner wall of the gas turbine combustor according to the second aspect, owing
to the effect of the gas turbine combustor according to the first aspect, has the
straight cylindrical inner circumferential surface. Compared to the structure with
the inner wall having a nozzle-like inner circumference surface protruding inward,
the gas turbine combustor according to the invention is configured to suppress adhesion
of the fuel supplied from the fuel supply unit to the inner wall. As the inner diameter
of the inner wall is kept constant, the flow velocity of the mixture is kept at a
constant value adequately to hardly fluctuate, resulting in a steady straight flow.
[0015] The gas turbine combustor according to the third aspect, owing to the effect of the
gas turbine combustor according to the second aspect, has the fuel supply unit formed
as the pressure injection nozzle of hollow cone type. This makes it possible to inject
the fuel in the hollow cone shape, and to atomize the fuel in good condition irrespective
of the air flow.
[0016] The gas turbine combustor according to the fourth aspect, owing to the effect of
the gas turbine combustor according to the third aspect, is configured so that the
other end of the premixing tube protrudes into the combustion cylinder. The fuel injected
into the premixing tube is exposed under the high temperature atmosphere in the combustion
cylinder so as to promote evaporation.
[0017] The gas turbine combustor according to the fifth aspect, owing to the effect of the
gas turbine combustor according to the fourth aspect, is configured to prevent the
problem of an increase in the temperature at the other end side of the premixing tube
caused by the conically injected fuel through the pressure injection nozzle, which
is adhered to the other end of the premixing tube and ignited.
[0018] The gas turbine combustor according to the sixth aspect, owing to the effect of the
gas turbine combustor according to the fifth aspect, is configured to suppress the
spread of the conically injected fuel through the pressure injection nozzle by the
air from the flow channel provided around the pressure injection nozzle. This makes
it possible to further alleviate adhesion of the fuel to the inner wall.
Brief Description of the Drawings
[0019] An embodiment of the present invention will now be described, by way of example only,
with reference to the accompanying drawings, of which:
Fig. 1 is a longitudinal sectional view of a gas turbine combustor according to an
embodiment of the present invention; and
Fig. 2 is an enlarged longitudinal sectional view of a part around a premixing tube
of the gas turbine combustor according to the embodiment.
Description of the Embodiment
[0020] An embodiment of the present invention will be described in detail referring to the
drawings.
[0021] Referring to Fig. 1, a general structure of a gas turbine combustor 1 according to
an embodiment will be described. The gas turbine combustor 1 includes a substantially
cylindrical combustion cylinder 2. The combustion cylinder 2 has a top portion closed,
and a lower opening communicated with an exhaust side of a not shown gas turbine.
The top portion of the combustion cylinder 2 is provided with a premixing tube 3,
which will be described in detail later. A top portion of the premixing tube 3 is
provided with a pressure injection unit 4 as a fuel supply unit. The combustion cylinder
2 and the premixing tube 3 are encased with an outer cylinder 5 communicated with
a compressed air inlet of a turbo-compressor (not shown). A part of a fuel supply
system connected to the pressure injection unit 4 is guided to the outside while penetrating
the top portion of the outer cylinder 5.
[0022] Referring to Figs. 1 and 2, at the center position of the top portion of the combustion
cylinder 2, the premixing tube 3 is coaxially provided. The premixing tube 3 includes
a cylindrical peripheral wall 6 provided outside the top portion of the combustion
cylinder 2, and a cylindrical protruding wall 7 that is provided at the top portion
of the combustion cylinder 2 so as to partially protrude into the combustion cylinder
2 downward by a predetermined dimension. The peripheral wall 6 has a straight cylindrical
outer shape, and an inner shape with the inner diameter gradually reduced toward the
combustion cylinder 2 in the downward direction. The peripheral wall 6 has a plurality
of holes 8 along the tangential direction, which allow air to flow inside. The protruding
wall 7 connected to the lower end of the peripheral wall 6 has the straight cylindrical
shape with the same inner diameter as that of the opening of the peripheral wall 6
at the lower end.
[0023] A cylindrical inner wall 9 is provided inside the peripheral wall 6 of the premixing
tube 3 coaxially at a predetermined interval therebetween. An outer circumferential
surface of the inner wall 9 has an outer diameter gradually reduced toward the combustion
cylinder 2 in the downward direction. The radial distance between the peripheral wall
6 and the inner wall 9 is kept constant, which defines a cylindrical gap S penetrating
downward. The gap S has its upper end at one end side of the premixing tube 3 closed,
and a lower end opened around the protruding wall 7. The inner circumferential surface
of the inner wall 9 has a straight cylindrical shape. The upper end of the inner wall
9 at one end side of the premixing tube 3 is opened to the outer cylinder 5.
[0024] The compressed air from the turbo-compressor, which is guided into the outer cylinder
5 flows inside through the holes 8 formed in the peripheral wall 6 of the premixing
tube 3, and then forms a swirl flow in the cylindrical gap S between the peripheral
wall 6 and the inner wall 9. It is further fed into the combustion cylinder 2 while
swirling along the inner circumferential surface of the protruding wall 7. The compressed
air is supplied to the inside of the inner wall 9 from the opening at the upper end
thereof together with the fuel supplied from the pressure injection unit 4, which
are formed into the mixture. The mixture forms the uniform straight flow along the
axial direction of the inner wall 9 over the whole region inside thereof under no
influence of the interference of the swirl flow. It is then supplied into the combustion
cylinder 2.
[0025] As shown in Fig. 2, the pressure injection unit 4 is attached to the center of the
opening at the upper end of the peripheral wall 6 at one end side of the premixing
tube 3. The pressure injection unit 4 is a pressure injection nozzle of hollow cone
type, which atomizes liquid fuel in a highly advanced manner by injecting the fuel
in a hollow conical shape. The pressure injection unit 4 is configured to discharge
the fuel supplied from two fuel supply channels, that is, a main supply channel 10
and a pilot supply channel 11 through one injection nozzle 12. The swirl motion is
applied to the fuel so that the fuel discharged through the injection nozzle 12 spreads
under centrifugal force to form a hollow cone film. As the pressure injection nozzle
of hollow cone type, the simplex injection valve is known.
[0026] As shown in Fig. 2, an injection angle α of the injection nozzle 12 of the pressure
injection unit 4 is set so that the conically injected fuel is not adhered to the
opening at the lower end (lower end of the protruding wall 7) of the premixing tube
3 with the whole axial length of L and inner diameter of D. A flow channel 13 is formed
around the pressure injection nozzle, through which the compressed air in the outer
cylinder 5 is guided from an inlet 14 so as to be injected. Accordingly, the air from
the flow channel 13 serves to suppress spread of the fuel conically injected through
the pressure injection nozzle. This makes it possible to further alleviate and suppress
adhesion of the fuel to the protruding wall 7.
[0027] Operations of the above-structured gas turbine combustor 1 according to the embodiment
will now be described.
[0028] The compressed air from the turbo-compressor is generally at the temperature of approximately
300°C. The compressed air is guided into the outer cylinder 5, flows inside through
the holes 8 formed in the peripheral wall 6 of the premixing tube 3, and forms the
swirl flow in the cylindrical gap S between the peripheral wall 6 and the inner wall
9. The swirl flow is retained along the inner circumferential surface of the protruding
wall 7, and fed into the combustion cylinder 2 so as to prevent adhesion of the flame
to an outlet of the protruding wall 7. Meanwhile, the compressed air is also supplied
into the inner space of the inner wall 9 from the opening at the upper end of the
premixing tube 3, and mixed with the fuel injected from the pressure injection unit
4 to form the mixture as the straight flow. It is fed into the combustion cylinder
2 through the protruding wall 7, and combusted to generate combustion gas at the temperature
ranging from 1000 to 2000°C, for example. The aforementioned temperatures of the air
and gas are taken as example values.
[0029] The compressed air and the fuel, or the mixture thereof in the inner wall 9 form
the uniform straight flow along the axial direction of the inner wall 9 over the entire
region inside thereof under no influence of the interference of the swirl flow of
the compressed air formed in the gap S between the peripheral wall 6 and the inner
wall 9. The flow is not forced to reduce the cross-section area by the swirl flow
around the protruding wall 7, and is fed into the combustion cylinder 2 for combustion.
Uniformity of the straight flow of the mixture in the premixing tube 3 along the axial
direction at the center is not disturbed by intrusion of the air swirl flow through
the holes 8 formed in the peripheral wall 6 of the premixing tube 3. This may secure
the uniformity of the cross-section area inside the peripheral wall as that of the
flow channel so that the mixture flow is stably fed into the combustion cylinder 2
at the constant flow velocity. The flame may be stably retained at the appropriate
position in the combustion cylinder 2, thus preventing deterioration in durability
of the combustion cylinder 2 by the heat, and realizing the stabilized combustion
and low emission.
[0030] The inner circumferential surface of the inner wall 9 of the gas turbine combustor
1 according to the embodiment has the straight cylindrical shape. This may further
alleviate and suppress adhesion of the fuel supplied from the pressure injection unit
4 to the inner wall 9. As a result, the position and state of combustion are further
stabilized, thus improving durability of the combustion cylinder 2 and the low emission.
[0031] The pressure injection unit 4 of the gas turbine combustor 1 according to the embodiment
is formed as the pressure injection nozzle of hollow cone type. This makes it possible
to inject the fuel in a hollow conical shape, and to atomize the fuel in good condition
as the effect of the nozzle by itself irrespective of the air flow. The resultant
synergistic effects allow the combustion state to be further stabilized.
[0032] The gas turbine combustor 1 according to the embodiment is configured so that the
other end of the premixing tube 3 is protruded into the combustion cylinder 2 as the
protruding wall 7. The fuel injected into the premixing tube 3 is exposed to the high
temperature atmosphere in the combustion cylinder 2 to facilitate evaporation. Stabilization
of the combustion state is expected as a result of the synergistic effects. The effect
of reducing the temperature on the surface of the protruding wall 7 by latent heat
of vaporization at the inner side of the protruding wall 7 is also expected.
[0033] The relationship between the injection angle α of the fuel injected through the pressure
injection nozzle, and the whole axial length L and the inner diameter D of the premixing
tube 3 is appropriately set so that the conically injected fuel is not adhered to
the other end of the premixing tube 3 of the gas turbine combustor 1 according to
the embodiment. As described above, in the embodiment, the air swirl flow in the gap
S is retained inside the protruding wall 7, which prevents adhesion of the flame to
the outlet of the protruding wall 7. The relationship between the shape of the premixing
tube 3 and the injection angle of the pressure injection nozzle ensures to further
prevent the disadvantage of an increase in the temperature resulting from ignition
of the fuel adhered to the other end of the premixing tube 3.
[0034] According to the gas turbine combustor 1 of the embodiment, the air from the flow
channel 13 provided around the injection nozzle 12 serves to suppress spread of the
fuel conically injected through the pressure injection nozzle. This ensures to further
prevent adhesion of the fuel to the other end of the premixing tube 3.
[0035] The gas turbine combustor 1 according to the embodiment ensures to generate the air
swirl flow in the gap S between the premixing tube 3 and the inner wall 9, and secure
the constant cross-section area of the flow in the inner space of the inner wall 9
under no interference. This also provides the straight flows of air and fuel at constant
flow velocities. This may provide the effect of ensuring mixture of the air and fuel
as a whole, and feeding the uniformly mixed mixture into the combustion cylinder 2
at a uniform flow velocity, and implementing the stable combustion with low emission.
This never applies an excessive thermal load to the device by ensuring the flame to
be retained at the appropriate position apart by the required distance from the top
portion of the combustion cylinder 2.
1. A gas turbine combustor (1) comprising:
a combustion cylinder (2) that combusts a mixture of fuel and air for supply of a
combustion gas to a turbine;
a premixing tube (3) that mixes the fuel and air supplied from one end side and supplies
the mixture into the combustion cylinder (2) from the other end side; and
a fuel supply unit (5) attached to the one end side of the premixing tube (3) for
supply of the fuel into the premixing tube (3),
wherein, through a peripheral wall of the premixing tube (3), a plurality of holes,
through which the air is allowed to flow, are formed along a tangential direction
of the peripheral wall; and
inside the premixing tube (3), with a cylindrical inner wall (9) provided apart from
the peripheral wall at a predetermined interval, a cylindrical gap having one end
side closed and the other end side communicated with the combustion cylinder (2) is
defined between the premixing tube (3) and the inner wall (9).
2. The gas turbine combustor (1) according to claim 1, wherein an inner circumferential
surface of the inner wall (9) has a straight cylindrical shape.
3. The gas turbine combustor (1) according to claim 2, wherein the fuel supply unit (5)
is a pressure injection nozzle (12) of hollow cone type which injects the fuel in
a hollow conical shape.
4. The gas turbine combustor (1) according to claim 3, wherein the other end side of
the premixing tube (3) is protruded into the combustion cylinder (2).
5. The gas turbine combustor (1) according to claim 4, wherein an axial length of the
premixing tube (3) is set so that the fuel conically injected through the pressure
injection nozzle (12) is not brought into contact with the other end side of the premixing
tube (3).
6. The gas turbine combustor (1) according to claim 5, wherein an air flow channel is
formed around the pressure injection nozzle (12).