Gas turbine combustor

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a combustor of a gas turbine, and more particularly to a combustor structured such that uniformity of combustion air intake is attained so as to enhance combustion efficiency and combustor cooling ability, as well as a fitting structure of structural portions which are less durable against thermal stress, such as a combustor main swirler or a pilot cone. They are improved so as to not be influenced by high temperature, whereby overall efficiency of the gas turbine combustor is enhanced in view of recent tendencies of higher temperature combustion gas. The present invention also relates to a combustor of a gas turbine having reduced combustion vibration.

2. Description of the Prior Art

FIG. 20

shows a structural arrangement of a representative gas turbine combustor and surrounding portions thereof in the prior art. In

FIG. 20

, numeral

20

designates a combustor, which is provided in a turbine casing

50

. Numeral

21

designates main fuel nozzles provided in plural pieces in a circumferential direction the combustor and is to be supplied with a main fuel of oil or gas. Numeral

22

designates a pilot fuel nozzle, which is provided in a central portion of the plural main fuel nozzles

21

for igniting the main fuel nozzles

21

. Numeral

23

designates a combustion chamber, and numeral

24

designates a tail tube, from which a high temperature gas produced in the combustion chamber

23

is led into a gas turbine. Numeral

62

designates a compressor, numeral

63

designates an air outlet, numeral

64

designates an air separator for supplying gas turbine blades with outside air for cooling thereof, numeral

65

designates a gas turbine stationary blade and numeral

66

designates a gas turbine moving blade.

In the combustor constructed as mentioned above, air

40

coming from the compressor

62

flows into the turbine casing

50

via the air inlet

63

and further flows into the combustor

20

, for effecting combustion, from around the combustor

20

through spaces formed between stays, described later, as air shown by numerals

40

a,

40

b.

In the flow of the air

40

at this time, there arises differences in the flow rate and pressure between the air

40

a

which is near the air outlet

63

or the compressor

62

and the air

40

b

which is far from the air outlet

63

or the compressor

62

. This causes a non-uniformity in the air flow entering the combustor

20

according to the circumferential directional position thereof, with the result that a biased flow of air arises in an inner tube, described later, in the combustor

20

, causing a non-uniformity of fuel flow as well, which leads to an increase of NO

x

formation.

FIG. 21

is an enlarged schematic view of the gas turbine combustor of FIG.

20

. In

FIG. 21

, there are shown several structural portions having shortcomings to be addressed. That is, an (X-

1

) portion and an (X-

2

) portion are air intake portions into the fuel nozzles, an (X-

3

) portion is a main swirler fitting structural portion, an (X-

4

) portion is a pilot cone fitting structural portion and an (X-

5

) portion is a tail tube cooling structural portion. There are problems to be solved in the respective portions. Such problems as exist in the present situation will be sequentially described below.

The air intake portion (X-

1

) will be described first.

FIG. 22

is a cross sectional view of a top hat type fuel nozzle portion of a prior art gas turbine. In

FIG. 22

, the air

40

a,

40

b

coming from the compressor flows into the combustor

20

for effecting a combustion from around the combustor

20

through spaces formed between supports

25

provided in the combustor

20

. Between the air

40

a

which is near the compressor and the air

40

b

which is far from the compressor, there are differences in the flow passages themselves and the shapes thereof, which causes a non-uniformity in the flow rate of the air flowing into the combustion chamber

23

according to the circumferential directional position thereof so as to cause a biased flow of the air. By this biased flow of the air, fuel flow also becomes non-uniform in the combustion chamber, and NO

x

formation increases. It is needed, therefore, that the air flow into the combustor be uniform in the circumferential direction.

Also, in the combustor of

FIG. 22

which is of the top hat type, there is fitted to the turbine cylinder

50

an outer tube casing cover

51

for covering a portion where the fuel nozzles are inserted. On the other hand, in the combustor of

FIG. 20

, the air intake portion is arranged in a space formed by a cylindrical casing of the turbine casing

50

. In the example of

FIG. 22

, a portion surrounding the supports

25

as the air intake portion is covered by the cylindrical outer tube casing cover

51

. The outer tube casing cover

51

is of a hat-like shape which projects toward the outside. In this type of combustor, a central axis

61

of the outer tube casing cover

51

of the turbine casing

50

and a central axis

60

of the combustor do not coincide with each other, and the combustor is fitted to the outer tube casing cover

51

so as to incline slightly thereto. Although a detailed explanation of the reason therefor is omitted, while the combustion gas flowing through the inner tube and the tail tube is led into a gas turbine combustion gas path, the temperature distribution of the gas flow is needed to be made as uniform as possible. In order to realize an optimized temperature distribution according to the manner in which the combustor is fitted, the central axis

60

of the combustor is inclined slightly relative to axis

61

of the outer tube casing cover

51

.

In the portion surrounding the supports

25

, as the air intake portion in such combustor, there are differences along the circumferential direction in the space areas formed by the outer tube casing cover

51

and the supports

25

, and while the quantity of intake air is varied in this way, there is still a non-uniformity of the intake air. In this type of combustor, while the outer tube casing cover

51

functions as a correcting tube to some extent, so that there is obtained some correction effect of the air flow coming in the combustor, as compared with the combustor of

FIG. 20

, the air takes turns at the air intake portion surrounding the supports

25

to flow into the nozzle portion. This causes a non-uniformity of the air flow, and hence improvement so as to realize a more uniform flow of the air is desired.

Next, a problem existing in the air intake portion (X-

2

) will be described.

FIG. 23

is a side view of an inner tube portion of the combustor

20

of FIG.

20

. In

FIG. 23

, a high temperature combustion gas

161

flows through the inside of an inner tube

28

. In a circumferential surface of the inner tube

28

, which is exposed to the high temperature gas, there are provided a multiplicity of small cooling holes (not shown). Air flowing through these cooling holes cools the inner tube

28

to then flow out to be mixed into the combustion gas flowing inside the inner tube

28

. On the other hand, there remains an unburnt component of fuel in the combustion gas flowing through the inner tube

28

, increasing the NO

x

formation, and hence it is necessary to sufficiently burn the unburnt component. For this purpose, there are provided in the circumferential surface of the inner tube

28

, air holes

10

-

1

,

10

-

2

, and

10

-

3

formed in three rows, with six air holes in each of the rows. The six air holes of each row are arranged with equal intervals between them in the circumferential direction of the inner tube

28

, as shown in FIG.

23

.

In the inner tube

28

constructed as above, the combustion gas

161

produced by the main fuel nozzle

21

flows through the inner tube

28

to flow to the tail tube

24

. For combustion of the unburnt component of fuel contained in the high temperature combustion gas

161

, air

130

is led into the inner tube

28

through the first row of air holes

10

-

1

and the second row of air holes

10

-

2

. Further, air

131

is led into the inner tube

28

through the downstream third row of air holes

10

-

3

for combustion of the unburnt component still remaining unburnt.

The air entering the combustor

20

comprises three portions, that is, the air used for combustion at the nozzle portion of the combustor, the air entering the inner tube

28

for cooling thereof through the small cooling holes and the air

130

,

131

flowing into the inner tube

28

through the air holes

10

-

1

,

10

-

2

, and

10

-

3

. Where the total quantity of these three portions of the air is 100%, as one example in a prior art combustor, the quantity of the air flowing through the air holes

10

-

1

, and

10

-

2

is about 14% each, and that of the air flowing through the air holes

10

-

3

is about 19 to 20%. If the respective quantities are expressed in a ratio for the air holes

10

-

1

,

10

-

2

and

10

-

3

, it is expressed as approximately 1:1 (1.3 to 1.4). That is, the air quantity entering the inner tube

28

through the downstream air holes

10

-

3

is largest. But if the air quantity entering through the air holes

10

-

3

becomes excessive, it remains unused for combustion, and cools flames of the high temperature combustion gas to thereby cause a colored smoke.

Next, a problem existing in the main swirler portion (X-

3

) will be described. In a prior art multiple type premixture combustor of a gas turbine, a pilot swirler is provided in a center thereof and either pieces of main swirlers are arranged therearound. Each of the main swirlers is fixed by welding to an inner wall of the combustor via a thin fixing member of about 1.6 mm thickness.

FIG. 24

is a cross sectional side view showing a swirler portion and a pilot cone portion of the type of combustor in the prior art and

FIG. 25

is a partial view seen from plane H—H of FIG.

24

. In

FIGS. 24 and 25

, numeral

20

designates a combustor, numeral

31

designates a pilot swirler provided in a center of the combustor

20

and numeral

33

designates a pilot cone fitted to an end of the pilot swirler

31

. Numeral

32

designates a main swirler, which is arranged in eight pieces around the pilot swirler

31

. Numeral

34

designates a base plate which is formed in a circular shape and has its circumferential portion fixed by welding to the inner wall of the container

20

. In the base plate

34

, there is provided a hole in a center portion thereof through which the pilot swirler

31

passes to be supported. Also provided are eight holes around the hole of the center through which the main swirlers

32

pass so as to be supported.

Numeral

35

designates metal fixing members, which are each formed of a metal plate and is interposed to fix each of the eight main swirlers

32

to the inner circumferential wall of an end portion

36

of the combustor

20

by welding. As shown in

FIG. 25

, the main swirlers

32

are fixed to the inner circumferential wall of the end portion

36

of the combustor

20

via the fixing metal member

35

. Although omitted in the illustration, a main fuel nozzle has its front end portion inserted into the main swirler

32

and a pilot fuel nozzle has its front end portion inserted into the pilot swirler

31

. Main fuel injected from the main fuel nozzle mixes with air coming from the main swirler

32

to be ignited for combustion by a flame, the flame being made by pilot fuel coming from the pilot fuel nozzle together with air coming from the pilot cone

33

of the pilot swirler

31

. The mentioned combustor

20

is arranged in several tens of pieces, 16 for example, in a circle around a rotor in a gas turbine cylinder for supplying therefrom a high temperature combustion gas into a gas turbine combustion gas path for rotation of the rotor.

In the gas turbine combustor so made as a welded structure, a deformation occurs due to vibration or thermal stress in operation so as to cause cracks in the welded portion of the metal fixing member

35

. This requires frequent repair work to replace the fixing metal member

35

or carry out additional welding work. In the fitting portion of the metal fixing member

35

, there is only a narrow space for welding work, creating a bad condition for performing a satisfactory welding. As such, a high level of skill of the workers is required. Also, in making the welded structure, a fine adjustment in fitting is difficult, which restricts maintaining accuracy. That is, there is a problem in the work accuracy in making the welded structure.

Next, a problem existing in the pilot cone portion (X-

4

) will be described. In the combustor

20

described with respect to

FIGS. 24 and 25

, the main fuel nozzle is inserted into the central portion of the main swirler

32

, and main fuel injected from the main fuel nozzle and air coming from the main swirler

32

are mixed together to form a premixture. On the other hand, the pilot fuel nozzle is inserted into the central portion of the pilot swirler

31

, and pilot fuel injected from the pilot fuel nozzle together with air coming from the pilot swirler

31

burns to ignite the premixture of the main fuel for combustion in a combustion tube, which include an inner tube and a connecting tube, to thereby produce the high temperature combustion gas.

FIG. 26

is a partial detailed cross sectional view of a fitting portion of the pilot cone

33

of FIG.

24

. In

FIG. 26

, a cone ring

38

at its one end is fitted to an outer wall of the pilot cone

33

by welding W

2

. The cone ring

38

at the other end is fitted to a fitting member

39

b,

which is an integral part of a base plate

39

, by welding W

1

. The pilot cone

33

is inserted into a cylindrical portion

39

a

of the base plate

39

and fixed to the base plate

39

by welding W

3

. An end portion

31

a

of the pilot swirler

31

is inserted into the pilot cone

33

to be fitted to the pilot cone

33

by welding W

4

. In the welding W

4

, a black arrow in

FIG. 26

shows a direction in which the welding is carried out. Thus, the pilot cone

33

is fitted to the base plate

39

via the cone ring

38

by welding W

3

and the pilot swirler

31

is fitted to the pilot cone

33

by welding W

4

. Hence, the base plate

39

fixes the central pilot swirler

31

, the pilot cone

33

and the eight pieces of the main swirlers

32

by welding, as mentioned above, to support them in a base plate block.

Fitting work procedures of the mentioned welded fitting structure have the cone ring

38

first fitted around the fitting member

39

b

of the base plate

39

by welding

1

, and then the pilot cone

33

is fitted to the cone ring

38

by welding W

2

. The pilot cone

33

is then fitted to the base plate

39

by welding W

3

which is done around an end portion of the pilot cone

33

. Thereafter, the pilot swirler

31

is inserted into the end portion of the pilot cone

33

to be fitted to the pilot cone

33

by welding W

4

to be done therearound. Thus, in case the pilot cone

33

is to be uncoupled in the welded structure, the weldings W

2

, W

3

and W

4

need to be detached. But in the spaces around the weldings W

2

and W

3

, there are arranged the main swirlers

32

, making the work space very narrow. This results in the need to disassemble the entirety of the base plate block. In this situation, the accuracy of the welding is deteriorated and becomes easily influenced by the thermal stress of the high temperature gas.

As the pilot swirler

31

and the pilot cone

33

are continuously influenced by the high temperature combustion gas, and the base plate block is made with a thin plate structure, as mentioned above, cracks easily arise due to strain caused by the thermal stress. This necessitates frequent repair work with a high level of welding skill, and thus an improvement of such welded structure is desired.

Next, a problem existing in the tail tube cooling portion (X-

5

) will be described. In the recent tendency toward higher temperature gas turbines, a combustor is being developed in which the combustion gas reaches a high temperature of about 1500° C., and the cooling system thereof is being tried to be changed to a steam type cooling system from the air type cooling system.

FIG. 27

is an explanatory view showing a tail tube cooling structure in a representative gas turbine combustor in the prior art, which has been developed by the present applicants, wherein FIG.

27

(

a

) is an entire view, FIG.

27

(

b

) is a perspective view showing a portion of a tail tube wall and FIG.

27

(

c

) is a cross sectional view taken on line J—J of FIG.

27

(

b

). In FIG.

27

(

a

), numeral

20

designates a combustor, which comprises a combustion tube and a tail tube

24

. Numeral

22

designates a pilot fuel nozzle, which is arranged in a central portion of the combustion tube, and numeral

21

designates main fuel nozzles provided in either pieces around the pilot fuel nozzle

22

. Numeral

26

designates a main fuel supply port, which supplies the main fuel nozzles

21

with fuel

141

. Numeral

27

designates a pilot fuel supply port, which supplies the pilot fuel nozzle

22

with pilot fuel

140

.

Numeral

125

designates a cooling steam supply pipe for supplying therethrough steam

133

for cooling. Numeral

126

designates a cooling steam recovery pipe for recovering therethrough recovery steam

134

after being used for cooling of the tail tube

24

of the combustor. Numeral

127

designates a cooling steam supply pipe, which supplies therethrough cooling steam

132

from a tail tube outlet portion for cooling of the tail tube

24

, as described later.

In FIG.

27

(

b

), showing a portion of a wall

20

a

of the tail tube

24

, there are provided a multiplicity of steam passages

150

in the wall

20

a.

Steam passing therethrough cools the wall

20

a.

In FIG.

27

(

c

), a steam supply hole

150

a

and a steam recovery hole

150

b

are provided to communicate with the steam passages

150

so that steam supplied through the steam supply hole

150

a

flows through the steam passages

150

for cooling of the wall

20

a

and is then recovered through the steam recovering hole

150

b.

In the combustor so constructed, the main fuel

141

is supplied into the eight pieces of the main fuel nozzles

21

from the main fuel supply part

26

. On the other hand, the pilot fuel

140

is supplied into the pilot fuel nozzle

22

from the pilot fuel supply port

27

to be burned for ignition of the main fuel injected from the surrounding main fuel nozzles

21

. Combustion gas of high temperature thus flows through the combustion tube and the tail tube

24

to be supplied into a combustion gas path of a gas turbine (not shown), and while flowing between stationary blades and moving blades, works to rotate a rotor. The combustor so constructed is arranged in various plural pieces according to the model or type, for example 16 pieces, around the rotor. The high temperature gas of about 1500° C. flows in the outlet of the tail tube

24

of each of the combustors. Thus, the combustor

20

needs to be cooled by air or steam.

In the combustor of

FIG. 27

, a steam cooling system is employed. The cooling steam

132

,

133

, extracted from a steam source (not shown), is supplied through the cooling steam supply pipes

127

,

125

, respectively, to flow through the multiplicity of steam passages

150

provided in the wall

20

a

of the tail tube

24

for cooling of the wall

20

a.

The cooling steam then joins together in the cooling steam recovery pipe

126

to be recovered as the recovery steam

134

to be returned to the steam source for effective use thereof.

FIG. 28

is a view seen from plane K—K of FIG.

27

(

a

) to show an outlet portion of the tail tube

24

. Numeral

160

designates a combustion gas path, through which the high temperature combustion gas of about 1500° C. is discharged. A flange

71

for connection to the gas turbine combustion gas path is provided at an end periphery of the outlet portion of the tail tube

24

.

FIG. 29

is a cross sectional view taken on line L—L of

FIG. 28

to show a steam cooled structure of the tail tube outlet portion in the prior art. In

FIG. 29

, the multiplicity of steam passages

150

are provided in the wall

20

a,

as mentioned above, in parallel with each other. A cavity

75

is formed over the entire inner circumferential peripheral portion of the flange

71

of the tail tube

24

outlet portion and the multiplicity of steam passages

150

communicate with the cavity

75

.

A manifold

73

is formed, being covered circumferentially by a covering member

72

, between an outer surface portion of the wall

20

a

of the tail tube

24

and the flange

71

. The respective steam passages

150

communicate with the manifold

73

via respective steam supply holes

74

.

In the mentioned steam cooled structure, a high temperature combustion gas

161

of about 1500° C., on the one hand, flows in the combustion gas path

160

, and on the other hand, the temperature of air flowing outside of the manifold

73

within the turbine cylinder is about 400 to 500° C. An inner peripheral surface portion of the wall

20

a

and that of the tail tube

24

outlet portion, which are exposed to the high temperature combustion gas

161

, are sufficiently cooled by the cooling steam

132

flowing into the steam passages

150

from the manifold

73

via the steam supply holes

74

. The steam in the cavity

75

cools also a portion

20

b

which is not exposed to the high temperature combustion gas

161

and the cooling steam

132

in the manifold

73

also cools a portion

20

c.

Hence, as compared with the inner wall

20

a,

the portions

20

b

and

20

c

are excessively cooled, causing a differential thermal stress between the wall

20

a

and the portions

20

b

and

20

c,

thereby causing unreasonable forces therearound, which results in the possibility of cracks occurring, etc.

The gas turbine combustor in the prior art as described above is what is called a two stage combustion type gas turbine combustion, effecting a pilot combustion and a main combustion at the same time. The pilot combustion is done such that fuel is supplied along the central axis of the combustor, and combustion air for burning this fuel is supplied therearound to form a diffusion flame (hereinafter referred to as a pilot flame) in the central portion of the combustor. Main combustion is done such that a main fuel premixture having a very high excess air ratio is supplied around the pilot flame so as to make contact with a high temperature gas of the pilot flame to thereby form a premixture flame (hereinafter referred to as a main flame).

FIG. 30

is a conceptual view of such a two stage combustion type gas turbine combustor in the prior art.

With reference to

FIG. 30

, within a liner

252

of the combustor

20

, the pilot fuel nozzle

22

for injecting a pilot fuel is provided along a central axis O′ and a pilot air supply passage

256

is provided around the pilot fuel nozzle

22

. The pilot swirlers

1

for flame holding is provided in the pilot air supply passage

256

. Further, the main fuel nozzle

21

, main air supply passages

258

and the main swirlers

32

for supplying main fuel are provided around the pilot air supply passage

256

.

The pilot cone

33

is provided downstream of the pilot fuel nozzle

22

and the pilot air supply passage

256

. The fuel supplied from the pilot fuel nozzle

22

and the air supplied from the pilot air supply passage

256

effect a combustion in a pilot combustion chamber

262

formed by the pilot cone

33

to form the pilot flame as shown by arrow

266

. The fuel supplied from the main fuel nozzles

21

and the air supplied from the main air supply passages

258

are mixed together in a mixing chamber

264

downstream thereof to form the premixture as shown by arrow

268

. This premixture

268

comes in contact with the pilot flame

262

to form the main flame

270

.

In the prior art combustor

20

, as the pilot flame

266

and the premixture

268

come in contact with each other in a comparatively short time, the premixture

268

is ignited easily, whereby the main flame

270

burns over a comparatively short length in the axial direction or the main flow direction, and is thus liable to form a short flame. If the combustion is over such a short length, or in other words, in a narrow space, a concentration of energy released by the combustion in the space of a cross sectional combustion load of the combustor becomes high to easily cause combustion vibration. Combustion vibration is a self-induced vibration caused by a portion of the thermal energy being converted to vibration energy, and as the cross sectional combustion load of the combustor becomes higher, the exciting force of the combustion vibration becomes larger and the combustion vibration becomes more liable to occur. As mentioned above, in the prior art combustor, the combustion load is comparatively high and there is a problem that the combustion becomes unstable due to the combustion vibration.

SUMMARY OF THE INVENTION

In the prior art gas turbine combustor as described above, mainly with reference to

FIG. 20

, non-uniformity of the air intake in the air intake portions (X-

1

) and (X-

2

), influence of the thermal stress due to the work process and work accuracy of the welded structures of the fitting portions of the main swirlers (X-

3

) and of the pilot cone (X-

4

), influence of the thermal stress due to non-uniformity of cooling of the tail tube cooling portion (X-

5

), etc. are obstacles in attaining higher temperature and higher efficiency of the gas turbine combustor. For realization thereof, further improvements of the mentioned portions of (X-

1

) to (X-

5

) are desired strongly.

Thus, it is an object of the present invention to provide a gas turbine combustor which makes uniform the air intake in the air intake portions (X-

1

) and (X-

2

) and realizes an optimal combustion air quantity therein, employs a fitting structure to mitigate the influence of the thermal stress in the thermally severest portions of the main swirler portion (X-

3

) and the pilot cone portion (X-

4

) and also employs a cooling structure to ensure a cooling uniformity of the tail tube cooling portion (X-

5

) to thereby totally solve the problems accompanying the higher temperature of the combustor, so as to realize a higher performance thereof.

Also, it is an object of the present invention to provide a gas turbine combustion having reduced combustion vibration.

In order to attain the object, the present invention provides the following (1) to (9).

(1) A gas turbine combustor is constructed such that an inner tube, a connecting tube and a tail tube are arranged to be connected sequentially from a fuel inlet side. The inner tube comprises a pilot swirler arranged in a central portion of the inner tube and a plurality of main swirlers arranged around the pilot swirler. The pilot swirler and each of the main swirlers at their respective end portions pass through a circular base plate to be supported. The circular base plate is supported by being fixed to an inner circumferential surface of the inner tube and an outlet portion of the tail tube is connected to a gas turbine inlet portion. The inner tube comprises an air intake for making the air intake into the combustor uniform. The pilot swirler or each of the main swirlers comprises a holding means for mitigating thermal stress and the outlet portion of the tail tube comprises a cooling means for attaining uniform cooling.

In the present invention of (1) above, which is a basic embodiment of the invention, the air intake makes the air flowing into the combustor uniform. The air quantity flowing into the inner tube through air holes provided in the circumferential wall of the inner tube is adjusted to an appropriate quantity, whereby good combustion is attained with less formation of NO

x

and colored smoke generated by combustion is suppressed as well. Also, by the holding means, the structural portions, such as the pilot swirler and the main swirlers, which are liable to receive thermal stress, influences are made such that the thermal stress is absorbed, repair and inspection become easy and welding of a high accuracy becomes possible, whereby shortcomings such as a weld cracks, etc. can be suppressed. Further, by the cooling of the tail tube, in case steam cooling is employed, non-uniformity of the cooling of the tail tube outlet portion is avoided. By the uniform cooling at this portion, cracks due to thermal stress, etc. can be prevented. Thus, according to the present invention of (1) above, combustion uniformity in higher temperature gas turbine and structural portions subject to severe thermal stress are improved. The cooling structure to attain the uniform cooling to prevent the generation of thermal stress at the tail tube outlet portion is employed, with the result that the performance enhancement of the gas turbine combustor using higher temperature combustion gas becomes possible.

(2) A gas turbine combustor as mentioned in (1) above may have the air intake constructed such that a rectifier tube is provided to cover the surroundings of the inner tube on the fuel inlet side, maintaining a predetermined space from the inner tube. The rectifier tube is at one end fixed to a turbine cylinder wall and is open at the other end.

In the present invention of (2) above, the air supplied from the compressor flows in around the combustor from the other end of the rectifier tube, and while it flows through the predetermined space between the rectifier tube and the combustor inner tube, it is rectified to be a uniform flow of an appropriate quantity, and then flows into the combustion chamber through the gaps formed by the plural supports. The air flow is a uniform flow without bias so that the fuel concentration at the nozzle outlet becomes uniform, whereby good combustion is attained and an increase of NO

x

formation can be suppressed. The mentioned rectifier tube may be applied to either a combustor of a type having a wider space in the combustor air inflow portion in the turbine cylinder, or what is called a top hat type combustor having the air inflow portion being covered by a casing, with the same effect being obtained in both cases.

(3) A gas turbine combustor as mentioned in (2) above may have the rectifier tube at one end comprising a sloping portion in which the diameter thereof contracts gradually.

In the present invention of (3) above, the rectifier tube at its one end comprises the sloping portion in which the diameter of the rectifier tube contracts gradually. The air flowing therein thereby strikes the inner circumferential surface of the sloping portion and changes the direction of flow entering the combustion chamber smoothly so that the air flows uniformly toward the central portion of the combustor with increased rectifying effect. Hence the effect of the invention of (2) above is ensured further.

(4) A gas turbine combustor as mentioned in (1) above may have the air intake constructed such that a plurality of air holes are provided in a circumferential wall of the inner tube, being arranged in a plurality of rows in a flow direction of the combustion gas flowing from upstream to downstream in the inner tube. Where air supplied from a fuel nozzle portion for combustion of the fuel, air supplied for cooling of the combustor and air supplied into the inner tube through the plurality of air holes are a total quantity of air, air supplied into the inner tube through the air holes of a most downstream row of the plurality of rows is 7 to 12% thereof.

In the gas turbine combustor, there are three portions of air flow thereinto, that is, air used for combustion of fuel supplied from the main fuel nozzles and the pilot fuel nozzle, air flowing into the inner tube through cooling holes provided in the inner tube wall for cooling of the inner tube and air flowing into the inner tube through air holes for burning unburnt components of the fuel. The air holes are provided in the circumferential wall of the inner tube as plural holes arranged in plural rows, three rows for example, in the gas flow direction in the inner tube. In the prior art, the air quantity flowing in each of the two rows on the upstream side is the same as each other, and that flowing in the row at the most downstream side is more than that, for example about 20% of the entire air quantity of the three portions. If the air flowing into the inner tube through the air holes of the most downstream row becomes excessive at a low load time, the combustion gas is cooled to increase the amount of colored smoke. In the present invention of (4) above, however, the air quantity entering through the air holes of the most downstream row is suppressed to 7 to 12% of the entire air quantity, which is approximately half of the prior art case, and hence generation of the colored smoke can be suppressed.

(5) A gas turbine combustor as mentioned in any one of (1) to (4) above may have the holding means constructed such that each of the plurality of main swirlers, at an inlet portion thereof, is fixed to an inner circumferential surface of the inner tube via a fitting member. The fixing of each of the main swirlers and the fitting member to the inner tube is done by a bolt joint.

In the present invention of (5) above, the main swirler at its outlet end portion, as well as the pilot swirler, are supported by the base plate, and the base plate is fitted to the inner circumferential surface of the combustor. Also, the main swirler at its inlet end portion is jointed to the inner circumferential surface of the combustor by the bolt via the fitting member, whereby the fitting work becomes easy, fine adjustment for the fitting can be done easily and accuracy of the fitting position is enhanced.

The holding structure is a welded structure in the prior art, so that cracks occur easily in the welded portions of the fitting member of the main swirler due to thermal stress, etc. In operation there is a limitation to the accuracy of the product made in the welded structure of thin metal plates and deformation occurs due to residual strain in the welded portions in addition to the thermal stress so as to cause mutual contact of the main swirler and the main fuel nozzles, increasing abrasion. Further, there is only a narrow space for welding work of the fitting member to deteriorate the workability. But in the present invention of (5) above, the shortcomings are improved to enhance reliability of the product, and the manufacturing cost thereof is reduced as well.

(6) A gas turbine combustor is mentioned in any one of (1) to (4) above may have the holding means constructed such that an outer diameter of an inlet end portion of the pilot cone, which is arranged on an outlet side of the pilot swirler, is made approximately equal to an outer diameter of an outlet end portion of the pilot swirler so that the inlet end portion of the pilot cone abuts on the outlet end portion of the pilot swirler. Welding is applied at this point from inside of the pilot cone to joint the pilot swirler and the pilot cone together.

In the present invention of (6) above, the pilot swirler passes through the central cylindrical portion of the base plate to be supported and the inlet portion end of the pilot cone abutting thereon is jointed by welding, which is done from inside of the pilot cone. In case the pilot cone is damaged by burning in operation so as to require replacement thereof, the welded portion of the pilot cone is thereby removed from the inside thereof, and the welded portion of the pilot cone and the fitting member of the base plate is also removed, so that the pilot cone only can be taken out easily and the replacement work thereof is done easily. In the prior art, if the pilot cone was to be detached, the entire swirler needed to be disassembled in each of the base plate blocks. But the welded structure of the present invention is made such that the pilot swirler is first fitted to the base plate and then the pilot cone is welded to the pilot swirler. The welding is done from inside of the pilot cone, so that detachment of the pilot cone can be done easily, replacement thereof becomes easy and workability thereof is improved. With such a welded structure, accuracy of the welding is enhanced and reliability in attaining the higher temperature of the gas turbine is also enhanced.

(7) A gas turbine combustor as mentioned in any one of (1) to (4) above may have the cooling means constructed such that a steam manifold is closed by a covering member to cover an outer circumference of an outlet portion of the tail tube and an end flange of the outlet portion of the tail tube. A plurality of steam passages are provided in a wall of the tail tube extending from the connecting tube to near the end flange of the tail tube. The plurality of steam passages communicate with the steam manifold and a cavity formed over an entire inner circumferential portion of the outlet portion of the tail tube near the end flange. The steam manifold is partitioned therein by a rib to form two hollows, one on the side of the end flange for covering at least an outer side of the cavity and the other for steam flow therein.

In the present invention of (7) above, the hollow is provided to cover the outer circumferential surface of the tail tube outlet portion near the end flange, and this hollow covers also the outer side of the cavity. Thus, the outer side of the cavity makes contact with the air layer in the hollow so as not to be cooled directly by the steam in the steam manifold. In the prior art, the outer side of the cavity is cooled directly by the steam in the cavity and in the steam manifold so as to be excessively cooled, which causes a differential temperature between the inner circumferential surface of the tail tube outlet portion and the outer side structural components, causing thermal stress. But in the present invention, such excessive cooling is avoided by mitigating the differential temperature between the tail tube outlet portion and the outer side components, and the thermal stress caused thereby can also be mitigated.

(8) A gas turbine combustor as mentioned in any one of (1) to (7) above may have shield gas supplied between the pilot air and the main combustion premixture. The pilot air is supplied from the pilot swirler and the main combustion premixture is formed by main air supplied from the main swirlers and main fuel being mixed together.

In the present invention of (8) above, the pilot fuel is burned by the pilot air, whereby the pilot flame which comprises the diffusion flame is formed. As in the prior art case, the main combustion premixture makes contact with the pilot flame to burn as the premixture combustion. The shield gas supplied around the pilot air suppresses mutual contact of the premixture and the pilot flame, whereby the combustion velocity of the premixture is reduced, the main flame, as the premixture flame formed between the premixture and the pilot flame, becomes longer in the longitudinal direction of the combustor and the combustion energy concentration is lowered.

(9) A gas turbine combustor as mentioned in (8) above may have the shield gas be a recirculated gas of exhaust gas produced by combustion in the gas turbine combustor.

In the present invention of (9) above, the shield gas is supplied from the recirculated gas of the gas turbine exhaust gas, whereby the oxygen concentration in the premixture flame is reduced and NO

x

formation is suppressed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

is a constructional view of a gas turbine combustor showing entire portions of embodiments according to the present invention.

FIG. 2

is a cross sectional view showing a fitting state of a rectifier tube of a gas turbine combustor of a first embodiment.

FIG. 3

is a cross sectional view taken on line A—A of FIG.

2

.

FIG. 4

is a perspective view of the rectifier tube of FIG.

2

.

FIG. 5

is a cross sectional view of an example where the rectifier tube of the first embodiment is applied to another type, or a hat top type, of combustor.

FIG. 6

is a cross sectional view of another example where the rectifier tube of the first embodiment is applied to still another type of combustor.

FIG. 7

is a side view of an inner tube portion of a combustor of a second embodiment according to the present invention.

FIGS. 8

are cross sectional views showing the arrangement of air holes of the inner tube, wherein FIG.

8

(

a

) is a view taken on line B—B of FIG.

7

and FIG.

8

(

b

) is a view showing a modified example of the air holes.

FIG. 9

is a cross sectional view taken on line C—C of FIG.

8

(

b

).

FIG. 10

is a graph showing a relation between smoke visibility and load as an effect of the second embodiment as compared with the prior art case.

FIGS. 11

is a partial cross sectional view of a main swirler of a combustor of a third embodiment according to the present invention.

FIG. 12

is an enlarged view of portion D of FIG.

11

.

FIG. 13

is partial view seen from plane E—E of FIG.

11

.

FIG. 14

is a detailed view of portion F of FIG.

13

.

FIG. 15

is a cross sectional side view showing a fitting portion of a pilot cone of a fourth embodiment according to the present invention.

FIG. 16

is a detailed view of portion G of FIG.

15

.

FIGS. 17

are enlarged detailed views of welded fitting structures of pilot cones, wherein FIG.

17

(

a

) is of a prior art and FIG.

17

(

b

) is of the fourth embodiment.

FIG. 18

is a cross sectional view of a steam cooled structure of a combustor tail tube outlet portion of a fifth embodiment according to the present invention.

FIG. 19

is a conceptual cross sectional view of a combustor of a sixth embodiment according to the present invention.

FIG. 20

is a structural arrangement view of a representative gas turbine combustor and surrounding portions thereof in the prior art.

FIG. 21

is an enlarged schematic view of the gas turbine combustor of FIG.

20

.

FIG. 22

is a cross sectional view of a top hat type fuel nozzle portion of a prior art gas turbine.

FIG. 23

is a side view of an inner tube portion of the combustor of FIG.

20

.

FIG. 24

is a cross sectional side view showing a swirler portion and a pilot cone portion in the prior art combustor.

FIG. 25

is a partial view seen from plane H—H of FIG.

24

.

FIG. 26

is a partial detailed cross sectional view of a fitting portion of the pilot cone portion of FIG.

24

.

FIG. 27

are explanatory views showing a tail tube cooling structure in a representative gas turbine combustor in the prior art, wherein FIG.

27

(

a

) is an entire view, FIG.

27

(

b

) is a perspective view showing a tail tube wall and FIG.

27

(

c

) is a cross sectional view taken on line J—J of FIG.

27

(

b

).

FIG. 28

is a view seen from plane K—K of FIG.

27

(

a

).

FIG. 29

is a cross sectional view taken on line L—L of FIG.

28

.

FIG. 30

is a conceptual view of a two stage combustion type gas turbine combustor in the prior art.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Herebelow, embodiments according to the present invention will be described with reference to the figures. The present invention solves various problems existing in the gas turbine combustor as described before with respect to

FIG. 21

, and

FIG. 1

shows the entire construction thereof. In

FIG. 1

, an (X-

1

) portion as a first embodiment, an (X-

2

) portion as a second embodiment, an (X-

3

) portion as a third embodiment, an (X-

4

) portion as a fourth embodiment, an (X-

5

) portion as a fifth embodiment and a case to solve a combustion vibration problem as a sixth embodiment will be described sequentially below.

The first embodiment in the (X-

1

) portion will be described with reference to

FIGS. 2

to

6

.

FIG. 2

is a cross sectional view showing a fitting state of a rectifier tube of the gas turbine combustor of the first embodiment,

FIG. 3

is a cross sectional view taken on line A—A of

FIG. 2

, and

FIG. 4

is a perspective view of the rectifier tube of FIG.

2

. In

FIG. 2

, a combustor

20

is contained in a turbine casing

50

and a plurality of supports

25

are fitted to and around an outer periphery of an inner tube

28

with a predetermined interval being kept between each of the supports

25

. A rectifier tube

11

is provided so as to surround and cover the supports

25

with a predetermined space being kept between itself and the inner tube

28

or the supports

25

. The rectifier tube

11

has fitting flanges

5

fixed by bolts

6

to the turbine casing

50

near end portions of the supports

25

.

In

FIG. 3

, the rectifier tube

11

is made by combining a casing

1

and a casing

2

, both of a semi-circular cross sectional shape. The casing

1

is provided with flanges

3

a,

3

b,

3

c,

3

d

(see

FIG. 2

) and the cylinder

2

is likewise provided with flanges

4

a,

4

b,

4

c,

4

d

(

4

b

and

4

d

are omitted in the illustration). These flanges are jointed together by bolts and nuts

7

to form the rectifier tube

11

of a circular cross sectional shape, wherein the flanges

3

a

and

4

a,

3

b

and

4

b,

3

c

and

4

c,

and

3

d

and

4

d

are jointed together, respectively.

The fitting flanges

5

of the rectifier tube

11

comprise plural pieces arranged around one end of the rectifier tube

11

of the cylindrical shape, as shown in FIG.

3

. The other end of the rectifier tube

11

opens as an air inflow side. The fitting flange

5

side of the rectifier tube

11

opens also, and main fuel nozzles

21

and a pilot fuel nozzle

22

are inserted through this opening portion. An outside view of only the rectifier tube

11

so constructed is shown in FIG.

4

.

In the gas turbine combustor so constructed, air

40

a,

40

b

coming from a compressor flows around the inner tube

28

of the combustor

20

through the predetermined space between the inner tube

28

and the rectifier tube

11

. The air is turned so as to be rectified by and around a sloping portion

11

a

of the rectifier tube

11

, wherein a diameter of the rectifier tube

11

contracts gradually along the air flow direction. Thus, the rectified air

40

a,

40

b

flows through gaps formed by the supports

25

to flow into the inner tube

28

uniformly.

As there had been no such rectifier tube

11

in the prior art, the air flowing around the combustor

20

flowed in through the gaps of the supports

25

from a comparatively wide space formed between an inner wall of the turbine casing

50

and the combustor

20

. There is a wide space or a narrow space in that space, according to the place where the air flowed, and hence the air did not flow uniformly therein.

On the contrary, in the present embodiment, a predetermined space is covered and maintained by the rectifier tube

11

around the gaps of the supports

25

through which the air flows. The air, whose pressure and velocity are kept constant, flows into this space to further flow into the combustor

20

through the gaps of the supports

25

. The air flow is rectified smoothly in its flow direction by the sloping portion of the rectifier tube

11

to uniformly flow into the combustor

20

. Thus no biased flow of the air coming into the inner tube

28

occurs and a uniform fuel concentration is attained at nozzle outlet portions of the combustor

20

, whereby NO

x

production can be suppressed.

FIG. 5

is a cross sectional view of an example where the rectifier tube

11

of the first embodiment is applied to another type, or a hat top type, of combustor. In

FIG. 5

, an outer tube casing

51

is provided to project toward the outside from a turbine casing

50

to form a fitting portion of an inner tube of the combustor. Such a combustor fitting structure is generally called a top hat type, wherein supports

25

support the inner tube

28

around main fuel nozzles

21

of the combustor and wherein the outer tube casing

51

and an outer tube casing cover

51

a

surround and cover the supports

25

. Such outer tube casing

51

is arranged projecting around a rotor in the same number of pieces as the combustor to form an extension portion of the turbine casing

50

.

The rectifier tube

11

is of a cylindrical shape and divided into two portions, as mentioned above. The rectifier tube

11

is provided with a plurality of fitting flanges

5

arranged circularly with a predetermined interval between each of the fitting flanges

5

. The tube

11

is thus fitted to an inner tube fitting flange

52

by bolts

6

via the fitting flanges

5

. A sloping portion

11

a

is formed so as to connect to the fitting flanges

5

. The rectifier tube

11

is provided coaxially with a combustor central axis

60

and covers an air intake space. The tube

11

maintains a gap so as not to come in contact with an inner wall surface of the outer tube casing

51

and maintaining a uniform dimension of the space

5

around the supports

25

.

In the combustor constructed as above, air

80

coming from a compressor flows in through an opening portion of the rectifier tube

11

to become a uniform flow

80

a

in the space between the rectifier tube

11

and the inner tube

28

, and then turns in the space formed by the sloping portion

11

a

and the supports

25

to flow into the combustor as a turning flow

80

b.

In this turning flow

80

b,

as the uniform flow

80

a

enters along the sloping portion

11

a

of the rectifier tube

11

, the flow turns smoothly to enter swirler portions in the space of the combustor, whereby a uniform swirled flow is produced and the combustion performance is enhanced.

FIG. 6

is a cross sectional view of another example where the rectifier tube

11

of the first embodiment is applied to still another type of combustor in which the top hat structural portion of the combustor is divided. That is, an outer tube casing

151

is detachably fitted with an outer tube casing cover

151

a

by a bolt

152

so that when the bolt

152

is unfastened, the outer tube casing cover

151

a

together with the combustor, may be taken out.

In

FIG. 6

, the rectifier tube

11

is constructed to be fitted to the outer tube casing cover

151

a

via fitting flanges

5

and an inner tube fitting flange

52

integrally by bolts

16

. In this construction, there no exclusive bolt is needed for fitting the rectifier tube

11

, whereby the structure of the fitting portion can be simplified. Other portions of the construction being the same as those of

FIG. 5

, the same effect as that of the example of

FIG. 5

can be obtained.

Next, a second embodiment in the (X-

2

) portion of the combustor of

FIG. 1

will be described with reference to

FIGS. 7

to

10

.

FIG. 7

is a side view of an inner tube portion of a combustor of the second embodiment. In

FIG. 7

, a high temperature combustion gas

161

flows into the inner tube

28

. The high temperature combustion gas is produced by combustion of fuel injected from a pilot fuel nozzle and main fuel nozzles and air. In a circumferential surface of the inner tube

28

, there are provided air holes

10

-

1

on an upstream side of the inner tube

28

, the air holes

10

-

1

comprising six air holes arranged at equal intervals around the inner tube

28

. Also, there are provided air holes

10

-

2

downstream of the air holes

10

-

1

comprising six air holes at equal intervals. Arrangement of these air holes

10

-

1

,

10

-

2

is the same as that of the prior art shown in FIG.

23

. In the present embodiment, air holes

10

-

3

on a downstream side of the inner tube

28

comprise only three air holes, which is less than the six in the prior art case, around the inner tube

28

.

FIGS. 8

are cross sectional view showing arrangement of the air holes

10

-

3

, wherein FIG.

8

(

a

) is a view taken on line B—B of FIG.

7

and FIG.

8

(

b

) is a view showing a modified example of the air holes

10

-

3

. In FIG.

8

(

a

), there are provided three air holes

10

-

3

a,

10

-

3

b,

and

10

-

3

c

with equal intervals in the circumferential surface of the inner tube

28

. In FIG.

8

(

b

), six air holes

10

-

3

a,

10

-

3

b,

10

-

3

c,

10

-

3

d,

10

-

3

e,

and

10

-

3

f

as provided in the prior art are seen, and in order to arrange the air holes in three parts with equal intervals, the air holes

10

-

3

b,

10

-

3

d,

and

10

-

3

f

are closed by plugs

14

. The air holes

10

-

3

a,

10

-

3

c,

10

-

3

e

only remain open, and there the same arrangement of three air holes as FIG.

8

(

a

) is formed.

FIG. 9

is a cross sectional view taken on line C—C of FIG.

8

(

b

). In

FIG. 9

, the plug

14

, being of a diameter which is slightly smaller than a hole diameter of the air hole

10

-

3

b,

has a flange

14

a

around a peripheral portion thereof and is fitted in the air hole

10

-

3

b

to be fixed by welding, etc. for closing of the hole. By the use of such plug

14

, an existing inner tube can be used as is and, when so modified, can easily have the construction of the present second embodiment.

In the second embodiment constructed as above, the air entering the combustor

20

comprises three portions, as in the prior art case. That is, it includes the air used for combustion at the nozzle portion, the air entering the inner tube for cooling thereof through the small cooling holes and the air flowing into the inner tube through air holes

10

-

1

,

10

-

2

, and

10

-

3

. Where the total quantity of the air is 100%, the quantity of the air flowing through the air holes

10

-

1

and

10

-

2

is about 14% each, as in the prior art case, and that of the air flowing through the air holes

10

-

3

, having only the three holes as compared with the six holes in the prior art, is suppressed to about 7 to 12%.

If the respective air quantities of the air holes

10

-

1

,

10

-

2

, and

10

-

3

are expressed in a ratio, it is approximately 1:1:(0.5 to 0.85). As compared with the ratio in the prior art of 1:1:(1.3 to 1.4), the air quantity entering the inner tube from the air holes

10

-

3

on the downstream side of the inner tube is reduced to approximately half. As a result of this, an appropriate air quantity is realized such that, while the air

131

entering through the air holes

10

-

3

on the downstream side of the inner tube is sufficient to be used for combustion of carbon remaining unburnt in the high temperature combustion gas

161

, it is not so much so as to cool the high temperature combustion gas

161

. Thus, the combustion efficiency is enhanced and the occurrence of a dark colored smoke in the exhaust gas can be prevented.

FIG. 10

is a graph showing a relation between smoke visibility and load as an effect of the second embodiment as compared with the prior art case. In

FIG. 10

, the horizontal axis shows load and the vertical axis shows the value of a level of smoke visibility (BSN). As this value becomes larger, it means a thicker smoke color visible by human eyes, and as this value becomes smaller, it means a thinner smoke color that is less visible. According to the result, it is understood that smoke color X

1

of the combustor of the present embodiment is thinner than the color X

2

of the combustor in the prior art shown in FIG.

23

. Thus there is obtained an effect of suppressing the occurrence of smoke.

Next, a third embodiment in the (X-

3

) portion of the combustor of

FIG. 1

will be described with reference to

FIGS. 11

to

14

.

FIG. 11

is a partial cross sectional view of a main swirler of a combustor of the third embodiment. In

FIG. 11

, a combustor

20

in its central portion has a pilot swirler

31

and a pilot cone

33

arranged at an end portion thereof. Eight main swirlers

32

are arranged around the pilot swirler

31

. These swirlers

31

and

32

are fitted to a base plate

34

of circular shape, and the base plate

34

has its circumferential periphery welded to an inner wall of the combustor

20

. This structure is the same as that existing in the prior art. A block

17

is fitted to an outer circumferential surface of an end portion of the main swirler

32

. The main swirler

32

is fixed to the inner wall of an end portion of the combustor

20

via the block

17

. The block

17

is fixed to the inner wall of the combustor

20

by a bolt

12

, which passes through the wall of the combustor from the outside via a washer

13

.

FIG. 12

is an enlarged view of portion D of FIG.

11

. The block

17

is fitted to the main swirler

32

by welding. A fitting seat

36

a

is formed by cladding welding on the inner wall of an end portion

36

of the combustor

20

. A recess portion

36

b

for receiving the washer

13

is formed in an outer wall of the combustor

20

at a position corresponding to the fitting seat

36

a.

A bolt hole is bored there, and the bolt

12

is screwed into the block

17

via the washer

13

for fixing of the block

17

, whereby the main swirler

32

is fixed to the combustor

20

.

FIG. 13

is a partial view seen from plane E—E of FIG.

11

. The block

17

is fitted by welding to the outer circumferential surface each of the main swirlers

32

arranged in eight pieces and each of the blocks

17

is fixed to the wall of the end portion

36

of the combustor

20

by two bolts

12

. The two bolts

17

are screwed into the block

17

via one common washer

13

.

FIG. 14

is a detailed view of portion F of

FIG. 13

, wherein the bolts

12

and the washer

13

are shown enlarged. The recess portion

36

b

is formed not in a curved form, but in a linear form in the outer circumferential surface of the end portion

36

of the combustor

20

, and the washer

13

is made as a flat plate of linear shape. The two bolts

12

are inserted into bolt holes

36

c,

which are bored in parallel with each other, to be screwed into the block

17

for fixing thereof and thus for fixing the main swirler

32

to the combustor

20

. An anti-rotation welding

18

is applied to the bolt

12

for preventing rotation or loosening thereof. By employing such structure, manufacture of the bolt fitting portion is simplified. As the washer

13

makes contact with the recess portion

36

b

via flat surfaces, a good effect against rotation or loosening of the bolt is obtained. Further, accuracy in the work process and in fitting can be enhanced.

In the prior art gas turbine combustor, as described before, cracks often occur in the welded portion of the fixing metal member

35

supporting the main swirler

32

due to vibration, thermal stress, etc. in operation. The structure itself is a welded structure of thin metal plates, so that there is a problem in the accuracy of fitting and assembling. Further, deformation occurs due to residual strain in the welded portion and the metal plates, which causes mutual contact of the main swirler

32

and the main fuel nozzle arranged therein, increasing abrasion. Also, there is only a narrow working space around the fitting portion of the fixing metal member

35

, which requires high skill for performing satisfactory welding.

According to the structure of the present third embodiment, the main swirler

32

is fixed to the combustor

20

by the bolt

12

via the washer

13

and the block

17

fixed to the main swirler

32

, whereby accuracy in assembling is enhanced, strain due to welding does not occur and welding work in the narrow space becomes unnecessary. Also, the washer

13

of flat plate shape makes contact with the recess portion

36

b

and the two bolts

12

fix the main swirler

32

to the combustor

20

, whereby no loosening of the bolts

12

occurs and precise positioning becomes possible. Further, maintenance and replacement of part, etc. becomes simple, so that all of the above mentioned problems are addressed.

Next, a fourth embodiment in the (X-

4

) portion of the combustor of

FIG. 1

will be described with reference to

FIGS. 15

to

17

.

FIG. 15

is a cross sectional side view showing a fitting portion of a pilot cone in the combustor, in contrast with the prior art case shown in FIG.

24

.

FIG. 16

is a detailed view of portion G of

FIG. 15

, in contrast with the prior art case shown in FIG.

26

.

In

FIGS. 15 and 16

, a pilot swirler

31

, a pilot cone

33

, a main swirler

32

, a base plate

39

, a fitting member

39

b

and a cone ring

38

have the same functions as those of the prior art shown in

FIGS. 24 and 26

. Hence the same reference numerals are used and description thereof is omitted. Featured portions of the present invention are configuration portions shown by numerals

31

a,

33

a

and welded portions of X

1

to X

4

will be described in detail below.

In

FIG. 16

, while a pilot swirler end portion

31

a

is structured in the prior art so as to be inserted into an end portion of the pilot cone

33

in contact with an inner circumferential surface of the pilot cone

33

, that of the present invention is structured to be inserted into the cylindrical portion

39

a

of the base plate

39

. For this purpose, a pilot cone end portion

33

a

is made shorter as compared with the prior art case. An outer diameter of the pilot cone end portion

33

a

is made approximately the same as that of the pilot swirler end portion

31

a

so that both ends of the pilot cone end portion

33

a

and the pilot swirler end portion

31

a

are welded together in contact with each other.

In the welded structure mentioned above, the pilot swirler

31

is first inserted into the cylindrical portion

39

a

of the base plate

39

to be fixed to an end of the cylindrical portion

39

a

by welding X

1

done along the circumferential direction. Then the cone ring

38

is fitted to the fitting member

39

b,

which is integral with the base plate

39

, by welding X

2

done along the circumferential direction. Then, while the pilot cone end portion

33

a

and the pilot swirler end portion

31

a

make contact with each other, the pilot cone

33

is fitted to the cone ring

38

by welding X

3

. Thereafter the pilot cone end portion

33

a

and the pilot swirler end portion

31

a

are jointed together by welding X

4

, which is done from inside of the pilot cone

33

along the circumferential direction. It is to be noted that the welding X

3

and X

4

may be done in the reverse order, that is, the welding X

4

may be earlier and the welding X

3

later, and also that a black arrow in

FIG. 16

shows a direction in which the welding X

4

is done.

According to the welded structure mentioned above, in case of repair work, the welding X

4

is removed from inside of the pilot cone

33

and the welding X

3

at the pilot cone outlet is also removed, whereby the pilot cone

33

can be easily detached. In the prior art case, there is insufficient work space in the portion of the welding X

3

, X

4

(

FIG. 26

) and moreover there is difficulty in detaching the pilot cone

33

unless the entire portion of the base plate block is disassembled. In the present fourth embodiment, however, the accuracy of the welded structure is enhanced, whereby the welding strength can be enhanced and workability in repair can be remarkably improved.

FIGS. 17

are enlarged detailed views of the welded fitting structures of the pilot cones of the prior art and of the present fourth embodiment, wherein FIG.

17

(

a

) is of the prior art and FIG.

17

(

b

) is of the fourth embodiment. In both of FIGS.

17

(

a

) and

17

(

b

), while the pilot cone end portion

33

a

is made long enough to be inserted into the cylindrical portion

39

a

of the base plate

39

in the prior art, the portion

33

a

of the present embodiment is made shorter to abut on the pilot swirler end portion

31

a.

By this structure, the pilot cone

33

of FIG.

17

(

b

) is supported by the base plate

39

via the welding X

4

of the pilot swirler

31

, and it is understood that detachment of the pilot cone

33

is easily done if the welding X

4

is removed by work done from inside of the pilot cone

33

, as shown by the black arrow of FIG.

17

(

b

).

According to the present fourth embodiment as described above, the welded structure is employed such that the pilot swirler

31

is first fitted to the base plate and the pilot cone

33

is fitted thereafter. The welding X

4

is done from inside of the pilot cone

33

, whereby repair work and detachment of the pilot cone

33

becomes easy, remarkably improving the workability. Thus, a lot of labor and time for repairing can be saved, the accuracy of the welding is enhanced and strain due to the thermal stress can be suppressed to a minimum.

Next, a fifth embodiment in the (X-

5

) portion of the combustor of

FIG. 1

will be described with reference to FIG.

18

.

FIG. 18

is a cross sectional view of a steam cooled structure of a combustor tail tube outlet portion of the fifth embodiment. This steam cooled structure is applicable to the outlet portion of the tail tube

24

shown in

FIG. 27

, and the structure of

FIG. 18

is shown in contrast with that of the prior art shown in FIG.

29

.

In

FIG. 18

, as in the prior art case, a multiplicity of steam passages

150

are provided in a wall

20

a

of the tail tube outlet portion and a cavity

75

is formed in an entire inner circumferential peripheral portion of a flange

71

of the tail tube outlet portion. A manifold

73

and a hollow

77

are formed by being covered circumferentially by a covering member

72

between an outer surface portion of the wall

20

a

of the tail tube outlet portion and the flange

71

and by being partitioned by a rib

76

between them. The manifold

73

communicates with a cooling steam supply pipe (not shown) and the hollow

77

has an air layer formed therein.

In the mentioned cooled structure, cooling steam

132

supplied into the manifold

73

from the cooling steam supply pipe flows into the steam passages

150

through a steam supply hole

74

to cool the wall

20

a,

which is exposed to a high temperature combustion gas of about 1500° C. Also, the steam entering the cavity

75

cools end portions

20

b

and

20

c.

The end portion

20

b

cooled by the steam in the cavity

75

is exposed on a side surface of the flange

71

to air of about 400 to 450° C. in a turbine cylinder. The end portion

20

c

is exposed to the air layer in the hollow

77

and is not directly exposed to the cooling steam

132

. While this end portion

20

c

is directly exposed to the cooling steam

132

so as to be excessively cooled in the prior art, such excessive cooling is prevented in the present fifth embodiment.

According to the fifth embodiment as described above, the wall

20

a

of the tail tube outlet portion to be directly exposed to the high temperature combustion gas

161

is sufficiently cooled by the cooling steam

132

supplied into the steam passages

150

from the manifold

73

through the steam supply hole

74

. On the other hand, while the steam entering the cavity

75

of the end portion of the tail tube outlet cools the wall exposed to the high temperature combustion gas

161

, the end portion

20

c

which is not directly exposed to the high temperature combustion gas

161

, is not cooled. This end portion

20

c

makes contact with the air layer in the hollow

77

and is not excessively cooled. Thus, the differential temperature between the inner circumferential wall surface and the outer circumferential structural portion in the tail tube outlet portion is mitigated and the thermal stress is alleviated.

It is to be noted that although the present fifth embodiment is described with respect to the example shown in

FIG. 27

, where the steam is supplied from the cooling steam supply pipe

127

of the tail tube outlet portion and from the cooling steam supply pipe

125

on the combustion tube side, and is recovered into the steam recovery pipe

126

, supply and recovery of the steam may be done reversely. That is, the steam may be supplied from the pipe

126

and recovered into the pipes

125

,

127

. In this case the same effect can also be obtained.

Next, a gas turbine combustor of a sixth embodiment will be described with reference to FIG.

19

. In

FIG. 19

, a combustor

20

is generally formed in a cylindrical shape and a pilot fuel nozzle

22

for supplying pilot fuel is provided in a liner

212

along a central axis O of the combustor

20

. A pilot air supply passage

216

is provided around the pilot fuel nozzle

22

and a pilot swirler

21

for holding the pilot flame is provided in the pilot air supply passage

216

. Thus, the pilot fuel nozzle

22

, the pilot air supply passage

216

and the pilot swirler

31

compose a pilot burner. Downstream of the pilot air supply passage

216

there is provided a pilot cone

33

for forming a pilot combustion chamber

224

.

A main fuel nozzle

21

for supplying main fuel and a main air supply passage

222

are provided around the pilot air supply passage

216

. A main swirler

32

is provided in the main air supply passage

222

. Thus, the main fuel nozzle

21

, the main air supply passage

222

and the main swirler

32

compose a main burner. Between the pilot air supply passage

216

and the main air supply passage

222

, there is provided an exhaust gas supply passage

218

as a supply passage of shield gas. Downstream of the exhaust gas supply passage

218

and on the outer side of the pilot cone

33

, a sub-cone

226

is provided coaxially with the pilot cone

33

. Numeral

218

a

designates a swirler provided in the exhaust gas supply passage

218

.

The function of the present embodiment will be described below. Pilot air supplied from the pilot air supply passage

216

enters the pilot combustion chamber

224

to flow so as to surround the pilot fuel supplied from the pilot fuel nozzle

22

, whereby the pilot fuel together with the pilot air burns to form the pilot flame (a white arrow

230

), comprising a diffusion flame. Main fuel supplied from the main fuel nozzle

21

and main air supplied from the main air supply passage

222

are mixed together in a mixing chamber

228

downstream thereof to form a premixture shown by arrow

232

. This premixture

232

comes in contact with the pilot flame

230

to form a premixture flame as a main flame

234

.

In the present gas turbine combustor

20

, exhaust gas produced by the combustion is supplied into a gas turbine (not shown) provided downstream of the combustor

20

for driving the gas turbine. After having driven the gas turbine, the exhaust gas is mostly discharged into the air, but a portion thereof is recirculated into the exhaust gas supply passage

218

of the combustor

20

via a recirculation system including an exhaust gas compressor, etc. (not shown).

The exhaust gas

236

supplied from the exhaust gas supply passage

218

flows through an exhaust gas leading portion as a leading portion of shield gas formed between the pilot cone

33

and the sub-cone

226

to be supplied between the pilot flame

230

and the premixture

232

. Thus, mutual contact of the pilot flame

230

and the premixture

232

is suppressed by the exhaust gas

236

, whereby the combustion velocity of the main flame

234

is reduced and the main flame

234

becomes longer in the combustor axial direction or in the main flow direction. Hence, the combustion energy concentration released by the main flame

234

, or the cross sectional combustion load of the combustor, becomes reduced, exciting forces of combustion vibration are reduced and combustion vibration is suppressed. Further, due to the existence of exhaust gas

236

, the oxygen concentration in the main flame

234

is reduced and the flame temperature is reduced, whereby the NO

x

quantity produced is reduced.

It is to be noted that although an example using exhaust gas of the gas turbine is described in the present embodiment, the invention is not limited thereto. Exhaust gas from other machinery or equipment may be used, or inert gas, such as nitrogen, supplied from other facilities may be used in place of the exhaust gas. The point is to use gas which is inert with respect to the combustion reaction so as to be able to prevent direct contact of the mixture and the pilot flame and to elongate the premixture flame in the main flow direction in the combustor.

While various embodiments are described with reference to figures, it is understood that the invention is not limited to the particular construction and arrangement of parts and components herein illustrated and described, but embraces such modified forms thereof as come within the scope of the appended claims.

Number	Date	Country	Kind
10-322630	Nov 1998	JP
10-348838	Dec 1998	JP

Number	Name	Date
4704869	Iizuka	Nov 1987
4852355	Kenworthy	Aug 1989
4872312	Iizuka	Oct 1989

Number	Date	Country
06257750	Sep 1994	JP
09021531	Jan 1997	JP

Gas turbine combustor

Information

Patent Number

Date Filed

Date Issued

Inventors

Original Assignees

Examiners

Agents

CPC

US Classifications

Field of Search

US

International Classifications

Abstract

Description

Claims

Priority Claims (2)

US Referenced Citations (3)

Foreign Referenced Citations (2)