Power plants – Combustion products used as motive fluid – Combustion products generator
Reexamination Certificate
2001-02-09
2003-10-21
Kim, Ted (Department: 3746)
Power plants
Combustion products used as motive fluid
Combustion products generator
C060S747000, C060S760000
Reexamination Certificate
active
06634175
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a gas turbine combustor and to a structure for reducing the disturbances in an air flow in the combustor so that the combustion instability may be reduced.
BACKGROUND ART
FIG. 13
is a general sectional view of a gas turbine. In
FIG. 13
, numeral
1
designates a compressor for compressing air for combustion and for cooling a rotor and blades. Numeral
2
designates a turbine casing, and numeral
3
designates a number of combustors arranged in the turbine casing
2
around the rotor. There are for example sixteen combustors, each of which is constructed to include a combustion cylinder
3
a,
a cylinder
3
b
and a transition cylinder
3
c.
Numeral
100
designates a gas path of the gas turbine, which is constructed to include multistage moving blades
101
and stationary blades
102
. The moving blades are fixed on the rotor and the stationary blades are fixed on the side of the turbine casing
2
. The hot combustion gas, jetting from the combustor transition cylinder
3
c,
flows in the gas path
100
to rotate the rotor.
FIG. 14
is a detailed view of portion
3
a
in FIG.
13
and shows the internal structure of the combustor
3
. In
FIG. 14
, numeral
4
designates an inlet passage of the combustor, and numeral
5
designates a main passage or a passage around main nozzles
7
. A plurality of, e.g., eight main nozzles
7
are arranged in a circle. Numeral
6
designates a main swirler which is disposed in the passage
5
of the main nozzles
7
for swirling the fluid flowing in the main passage
5
toward the leading end. Numeral
8
designates one pilot nozzle, which is disposed at the center and which is provided therearound with a pilot swirler
9
, as in the main nozzles
7
. Numeral
10
designates a combustion cylinder.
In the gas turbine combustor thus far described, the air, as compressed by the compressor
1
, flows, as indicated by
110
, from the compressor outlet into the turbine casing
2
and further flows around the inner cylinder of the combustor into the combustor inlet passage
4
, as indicated by
110
a.
After this, the air turns around the plurality of main nozzles
7
, as indicated by
110
b,
and flows into the main passage
5
around the main nozzles
7
, as indicated by
110
c.
On the other hand, the air also flows around the pilot nozzle
8
, as indicated by
110
d,
and is swirled by the main swirler
6
and the pilot swirler
9
until it flows to the individual nozzle leading end portions, as indicated by
110
e,
for combustion.
FIG. 15
is a diagram showing the flow states of the air having flowed into the combustor of the prior art. The air
110
a
from the compressor flows, as indicated by
110
b,
around the main nozzles
7
. Around the outer sides of the main nozzles
7
, however, vortexes
120
are generated by the separation of the flow. When the air flows in from the root portion around the pilot nozzle
8
, on the other hand, there are generated vortexes
121
, vortexes
122
flowing to the leading end of the pilot nozzle
8
, and disturbances
123
in the flow around the outlet of the inner wall of the combustor.
In this gas turbine, NOx is emitted more as the load becomes heavier, but this emission has to be suppressed. As the load is increased, the combustion air has to be increased accordingly. As described with reference to
FIG. 15
, the air vortexes
120
,
121
,
122
and
123
in the combustor are more intensified, increasing the tendency to combustion instability. In order to suppress the emissions of NOx, the aforementioned combustion instability is reduced at present by adjusting the pilot fuel ratio and the bypass valve opening. With the prevailing structure, however, the running conditions are restricted by the combustion instability.
In the gas turbine combustor of the prior art, as has been described hereinbefore, drifts, vortexes and flow disturbances are caused in the air flowing in the combustor, causing the combustion instability. As the load is increased, increasing the flow rate of air to combustion, so that the drifts, vortexes and flow disturbances have serious influences, the concentration of the fuel becomes heterogeneous with respect to time and space, thereby making the combustion unstable. At present, in order to suppress this combustion instability, the pilot combustion ratio and the bypass valve opening are adjusted, but in vain for sufficient combustion stability. In the worst case, therefore, the combustor is damaged and the gas turbine running range is restricted.
SUMMARY OF THE INVENTION
Therefore, the present invention has been conceived to provide a gas turbine combustor which reduces combustion instability by guiding the air to flow smoothly into the combustor and by straightening the flow to eliminate flow disturbances and concentration changes of the fuel.
In order to solve the foregoing problems, the present invention contemplates the following.
(1) A gas turbine combustor comprises a cylinder supported at its circumference by a plurality of struts fixed on one end in a combustor housing portion of a turbine casing. A pilot nozzle is arranged at the center of the cylinder. A plurality of main nozzles are arranged around the pilot nozzle. A flow ring has a ring shape so as to cover the upstream end of the cylinder, a semicircular sectional shape (including an elliptical shape) and so maintains a predetermined gap. A porous plate downstream of the flow ring closes a space which formed in the cylinder between the pilot nozzle and the main nozzles.
(2) A gas turbine combustor as set forth in (1), can have the flow ring sectionally shaped as an extended semicircular shape by extending the two ends of a semicircle. The porous plate is fixed at its circumference on the circumferential side face of the extended semicircular shape.
(3) A gas turbine combustor as set forth in (1), can have the flow ring include semicircular curves arranged in multiple stages while maintaining a predetermined gap.
(4) A gas turbine combustor as set forth in (1), can have a guide portion disposed around the inlet portion of the combustor housing portion of the turbine casing with a smoothly curved face for covering the whole circumference wall face of the inlet portion.
(5) A gas turbine combustor as set forth in (1), can also have a funnel shaped flow guide having a smoothly curved sectional shape along the curved face of the flow ring and arranged upstream of the flow ring while maintaining a predetermined gap from the flow ring. The flow guide is fixed at its larger diameter portion on the inner wall of the combustor housing portion of the turbine casing and at its smaller diameter portion around the pilot nozzle. The porous plate is arranged downstream of a support for supporting the pilot nozzle and the main nozzles.
(6) A gas turbine combustor according to the present invention may also comprise a cylinder supported at its circumference by a plurality of struts fixed on one end in a combustor housing portion of a turbine casing. A pilot nozzle is arranged at the center of the cylinder. A plurality of main nozzles are arranged around the pilot nozzle. A flow ring having a ring shape covers the upstream end of the cylinder, has a semicircular sectional shape and maintains a predetermined gap. Flow rings individually having semicircular sectional shapes are arranged in multiple stages upstream of the flow ring in the axial direction while maintaining a predetermined gap. A cylindrical porous plate covers the entire circumference of the inlet portion on the outer side of all of the flow ring.
(7) Another gas turbine combustor may comprise a pilot nozzle arranged at the center of a cylinder and a plurality of main nozzles arranged around the pilot nozzle. Spaces between the circumference of the pilot nozzle and the inner circumferences of the individual main nozzles confronting each other are filled with a filler in the axial direction downstream from the upstream end so as to extend near the circumferential portion of the leading end of the cylinder, thereby forming
Akita Eiji
Arimura Hisato
Kawata Yutaka
Mandai Shigemi
Tsukuda Yoshiaki
Kim Ted
Mitsubishi Heavy Industries Ltd.
Wenderoth , Lind & Ponack, L.L.P.
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