Annular combustor for a gas turbine engine

Field of invention

The present invention relates to an annular combustor for a gas turbine engine and to a gas turbine engine including such a combustor.

Art Background Annular combustors are well known in the field of gas turbine engines .

An annular combustor is normally included in a gas turbine engine 1 comprising, arranged in flow series: a compressor section, a burner, the annular combustor and a gas turbine section. In operation of the gas turbine engine, air is compressed by the compressor section and delivered to the combustion section, including the burner and the annular combustor. The compressed air exiting from the compressor enters the burner, where is mixed with a gaseous or liquid fuel. The air/fuel mixture is then burned and the combustion gas from the combustion is channelled through the combustor to the gas turbine section, for transforming the energy from the operative gas into working power. The annular combustor for the above described application normally extends axially between a first axial burner end, close to the burner and a second axial outlet end, adjacent to the inlet of the gas turbine section. Further the annular combustor radially extends between an annular inner liner and an annular outer liner. At first axial burner end, the annular combustor comprises an annular backwall for connecting the annular inner liner and the annular outer liner. The backwall comprises at least a hole for coupling at least a respective burner to the annular combustor.

According to a known possible prior art solution, the annular combustor described above is normally manufactured in one piece including at least the annular inner liner, the annular outer liner and the backwall. Such unitary piece is then attached to the gas turbine engine by means of one or more connections provided between the combustor and a casing of the gas turbine engine. Such a connection is typically remote from the interface between the outlet of the combustor and the inlet of the gas turbine, therefore a gap is necessary between the combustor and the gas turbine for allowing thermal expansions.

Such an annular combustor and attachment determines a plurality of inconveniences:

- the gap in the interface between the combustor and the inlet of the turbine section cannot be reduced below a lower limit. This leads to damages to the components, due to hot gas ingestion, i.e. the hot gas exiting the second axial outlet end of the combustor and leaking through the gap between combustor and gas turbine section;

- when a reparation is required, repairing an annular combustor like the one described above, i.e. a combustor manufac- tured in a unitary piece attached to the casing of the gas turbine engine, is expensive.

Prior art solutions to above inconveniences may be, respectively:

- purging air has in the cavity between the combustor and the gas turbine section,-

- cutting the combustor into several pieces, that, after reparation, have nevertheless to be welded back together. The above solutions are not yet considered optimal and therefore it is still desirable to provide a new annular combustor design for efficiently overcoming the above described drawbacks . Summary of the Invention It may be an object of the present invention to provide an annular combustor for a gas turbine engine permitting to reduce at the minimum or eliminating the gap between the combustor and the inlet of the turbine section, in such a way that the phenomenon of hot gas ingestion is avoided or lim- ited to a minimum.

It may be a further object of the present invention to provide an annular combustor for a gas turbine engine, whose maintenance is easier and less expensive, with respect to the prior art.

It may be an additional object of the present invention to provide a gas turbine engine including an annular combustor having a reduced gap between the combustor and the inlet of the turbine section and whose maintenance is easier and less expensive, with respect to the prior art.

In order to achieve the objects defined above, an annular combustor for a gas turbine is provided in accordance with the independent claim. The dependent claims describe advantageous developments and modifications of the invention.

According to a first aspect of the present invention, a segmented annular combustor for a gas turbine engine, the annu- lar combustor axially extending between a first axial burner end and a second axial outlet end, the annular combustor radially extending between an annular inner liner and an annular outer liner, the annular combustor being at least an assembly of :

- a first part including the annular inner liner and a first connection element for connecting the first part to the gas turbine engine, - a second part including the annular outer liner and a second connection element for connecting the second part to the gas turbine engine independently from the first part, the second part being attachable to the first part in a removable way,

- at least one of the first connection element and of the second connection element being adjacent to the outlet end of the combustor.

The segmentation of the annular combustor allows reducing at the minimum or eliminating the gap between the outlet of the combustor and the inlet of the gas turbine. As a result, hot gas ingestion is eliminated or effectively reduced, thus producing a much more robust design, which would be also easier and therefore cheaper to repair. In particular, with the de- sign of the present invention, it is also possible to replace only a certain part of the combustor (for example only the inner liner or only the outer liner) on site, because no cutting and welding would be needed.

Further, reducing the slot between the combustor and the tur- bine makes it possible to improve the flow path aerodynamics of the transition between combustor and turbine.

The term "segmented" means that the combustor is not a single unitary piece but an arrangement of segments.

According to an exemplary embodiment of the present invention, the first or the second part further includes a back- wall for connecting the annular inner liner and the annular outer liner at the first axial burner end, the backwall com- prising at least an hole for coupling a burner to the annular combustor .

According to another exemplary embodiment of the present invention, the annular combustor is an assembly of the first part, the second part, and at least a third part including: - a backwall for connecting the annular inner liner and the annular outer liner at the first axial burner end, the back- wall providing at least an hole for letting a gas including fuel and air inside the annular combustor, - a third connection element for connecting the third part to a casing of the gas turbine engine.

According to the last two described embodiments, it is either possible that the annular combustor of the present invention is made part of two parts, one including the backwall, or is made of three parts, respectively including inner liner, outer liner and backwall. Advantageously, these variants give the possibility to adapt the combustor design of the present invention to the design of different gas turbine engines, for example gas turbine engines having different overall dimensions .

According to a further embodiment of the present invention, between the backwall and at least one of the inner liner and the annular outer liner a sealing is provided.

More particularly, the sealing may comprise at least a finger seal .

The sealing avoids leakages through the contacts between first, second and third part of the annular combustor at the backwall, i.e. where the first, second and third part contact each other.

According to another exemplary embodiment of the present invention, the annular inner liner and/or the annular outer liner comprise a plurality of effusion holes for letting compressed air to enter the combustor through the annular inner liner and /or the outer liner, in order to cool the annular inner liner and /or the outer liner, respectively.

According to yet another exemplary embodiment of the present invention, the annular inner liner and/or the annular outer liner comprises at least a cooling passage inside the liner. The cooling passage may be provided between two panels of the annular inner liner and/or of the annular outer liner, bonded together .

The effusion holes or the cooling passages provide the necessary cooling to the walls of the inner and outer liners. According to a second aspect of the present invention, a gas turbine engine comprises a burner, a gas turbine and an annular combustor as above described, between the burner and the gas turbine .

According to a third aspect of the present invention, a gas turbine comprises an inlet section and at least one connection element adjacent to the inlet section for coupling with an annular combustor as above described.

Brief Description of the Drawings

The aspects defined above and further aspects of the present invention are apparent from the examples of embodiment to be described hereinafter and are explained with reference to the examples of embodiment. The invention will be described in more detail hereinafter with reference to examples of embodiment but to which the invention is not limited.

Fig. 1 is a partial schematic view, sectioned along a longitudinal direction, of a gas turbine engine including a first embodiment of an annular combustor according to the present invention,

Fig. 2 is a partial schematic view, sectioned along a longitudinal direction, of a gas turbine engine including a second embodiment of an annular combustor according to the present invention,

Fig. 3 is a partial schematic view, sectioned along a longitudinal direction, of a gas turbine engine including a third embodiment of an annular combustor according to the present invention,

Fig. 4 is a partial schematic view, sectioned along a longitudinal direction, of a gas turbine engine including a fourth embodiment of an annular combustor according to the present invention,

Fig. 5 shows a magnified view of the detail V of figure 4.

Detailed Description

Hereinafter, above-men ioned and other features of the pre- sent invention are described in details. Various embodiments are described with reference to the drawings, wherein the same reference numerals are used to refer to the same elements throughout. The illustrated embodiments are intended to explain, and not to limit the invention.

Figure 1 shows an example of a gas turbine engine 1 in a partial schematic sectional view.

The gas turbine engine 1 (not shown as a whole) comprises, in flow series, a compressor section 4 (not shown as a whole), a plurality of burners 2 (only one burner 2 shown in each of the section figures 1 to 4) an annular combustor 10 and a gas turbine 3, which are generally arranged in flow series within a casing 5.

The gas turbine engine 1 is generally arranged about a rotational axis X, which is the rotational axis for rotating components, in particular the compressor section 4 and the gas turbine 3. The rotational axis X is also coincident with the axis of symmetry of the annular combustor 10, when the annu- lar combustor 10 is assembled to the gas turbine engine 1. In operation of the gas turbine engine 1, air is compressed by the compressor section 4 and delivered to the combustion section, including the burner 2 and the annular combustor 10. The compressed air exiting from the compressor 4 and flowing towards the combustion section is schematically represented in the attached figures by arrows A. The compressed air enters the burner 2 where is mixed with a gaseous or liquid fuel. The air/fuel mixture is then burned and the combustion gas from the combustion is channelled through the combustion chamber 10 to the gas turbine section 1, for transforming the energy from the operative gas into working power. The combustion gas flows along the combustion chamber 10 along a main direction oriented from the burner 2 to the gas turbine 3.

The combustion section 4 and the burner 2 are not a specific object of the present invention and, therefore, in the following, they will not be described in further detail.

In the following the terms radial, circumferential and axial are with respect to the rotational and symmetry axis X.

The annular combustor 10 extends axially between a first axial burner end 11 and a second axial outlet end 12 and ra- dially between an annular inner liner 15 and an annular outer liner 16.

The annular combustor 10 further includes:

- a first part 21 including the annular inner liner 15 and a first connection element 31 for connecting the first part 21 to the gas turbine engine 1,

- a second part 22, distinct from first part 21, including the annular outer liner 16 and a second connection element 32 for connecting the second part 22 to the gas turbine engine 1,

- a backwall 25 for connecting the annular inner liner 15 and the annular outer liner 16 at the first axial burner end 11. The backwall 25 comprises a plurality of holes 26, distributed about the axis X, for coupling a plurality of respective burners 2 to the annular combustor 10.

According with the different embodiments of the present invention, at least one of the first connection element 31 and of the second connection element 32 is adjacent to the outlet end 12 of the combustor 10 and is connectable to a respective gas turbine connection element 17, 18 on the gas turbine 3, respectively radially inner and outer. The connection elements 17, 18 are adjacent to the inlet section 13 of the gas turbine 3. Optionally, the annular combustor 10 further comprises a third part 23, distinct from first part 21 and from the second part 22. The third part 23 includes the backwall 25 and a third connection element 33 for connecting the third part 22 to the casing 5 of the gas turbine engine 1.

With reference to the embodiment of figure 1, the annular combustor 10 is an assembly of:

- the first part 21, with the first connection element 31 connecting the first part 21 to the inner connection element 17 of the gas turbine 3,

- the second part 22, with the second connection element 32 connecting the second part 22 to the outer connection element 18 of the gas turbine 3,

- the third part 23, with the third connection element 33 connecting the third part 23 to a casing connection element

35 on the casing 5.

The coupling between the first, second and third part 21, 22, 23 and the gas turbine 3 and the casing 5, respectively, is circumferentially distributed about the axis X. According to the different embodiments of the present invention, this may be obtained with circumferential elongated connection elements 31, 32, 33, 17, 18, 35. As an alternative each of the first part 21, second part 22 and third part 23 comprises a respective plurality of connection elements 31, 32, 33 to be coupled to a respective plurality of connection elements 17, 18 on the gas turbine 3 and of connection elements 35 on the casing 5.

With reference to the embodiment of figures 2 and 3, the third part 23 is not present and the backwall 25 is comprised in the first part 21 and in the second part 22, respectively. The annular combustor 10 of figure 2 is therefore an assembly of:

- the first part 21, including the annular inner liner 15 and the backwall 25, with the first connection element 31 con- necting the first part 21 to the casing connection element 35, - the second part 22, with the second connection element 32 connecting the second part 22 to the outer connection element 18 of the gas turbine 3.

The coupling between the first and the second part 21, 22 and the casing and 5 the gas turbine 3, respectively, is circum- ferentially distributed about the axis X. According to the different embodiments of the present invention, this may be obtained with circumferential elongated connection elements 31, 32, 18, 35. As an alternative each of the first part 21 and second part 22 comprises a respective plurality of connection elements 31, 32 to be coupled to a respective plurality of casing connection elements 35 and of outer connection elements 18 on the gas turbine 3.

The annular combustor 10 of figure 3 is instead an assembly of:

- the first part 21, with the first connection element 31 connecting the first part 21 to the inner connection element 17 of the gas turbine 3,

- the second part 22, including the annular outer liner 16 and the backwall 25, with the second connection element 32 connecting the second part 22 to the casing connection element 35.

The coupling between the first and the second part 21, 22 and the gas turbine 3 and the casing 5, respectively, is circum- ferentially distributed about the axis X. According to the different embodiments of the present invention, this may be obtained with circumferential elongated connection elements 31, 32, 17, 35. As an alternative each of the first part 21 and second part 22 comprises a respective plurality of con- nection elements 31, 32 to be coupled to a respective plurality of inner connection elements 17 on the gas turbine 3 and of casing connection elements 35.

In all the embodiments above described, the couplings between the first, second and third part 21, 22, 23 and the gas tur- bine 3 and/or the casing 5 are detachable and may performed by means of screw (or other threaded connection) and/or bolts. This allows connecting and disconnecting each part 21, 22, 23 of the annular combustor 10 independently from the others .

In all embodiments, the mounting of the first, second and third part 21, 22, 23 in the gas turbine engine is made in such a way that the outlet end 12 of the annular combustor 10 is mounted adjacent to the inlet section 13 of the gas turbine 3. This avoids or limits hot gas leakages when hot gases from the annular combustor 10 enter the gas turbine 3. In all the embodiments of the present invention the annular combustor 10 is constituted as an assembly of two (embodiments of figs. 2 and 3) or three (embodiments of figs. 1 and 4) main parts 21, 22, 23 attachable to each other in a removable way, in order that each of the two or three parts 21, 22, 23 of the annular combustor 10 is connectable and discon- nectable to the gas turbine 3 and/or the casing 5 independently from the other (s) of the parts 21, 22, 23 of the annular combustor 10.

This implies no permanent connection, for example a welded connection, is provided between the two or three main parts

21, 22, 23 which constitutes the annular combustor 10.

The first, second and third part 21, 22, 23 contact each other along the edges of the backwall 25. To avoid leakages through the contacts between first, second and third part 21, 22, 23, a sealing 40 is provided between the backwall 25 and at least one of the inner liner 15 and the annular outer liner 16.

In the embodiments of the attached figures 1 to , the sealing 40 comprises an inner finger seal 41 between the backwall 25 and the inner liner 15 and/or an outer finger seal 42 between the backwall 25 and the outer liner 16.

In the embodiment of figures 1 and 4, where the first, second and third part 21, 22, 23 are present, both the inner and outer finger seals 41, 42 are present.

In the embodiment of figure 2, where the backwall 25 is integrated in the first part 21 of the annular combustor 10, only the outer finger seal 42 is present. In the embodiment of figure 3, where the backwall 25 is integrated in the second part 22 of the annular combustor 10, only the inner finger seal 41 is present.

According to other embodiments of the present invention, other sealing devices may be used between the parts 21, 22, 23 of the annular combustor 10, in order to avoid hot gas leakages between the backwall 25 and the inner liner 15 and/or between the backwall 25 and the outer liner 16. The inner finger seal 41 and/or the outer finger seal 42 interact with the third part 23 such that the first part 21 and/or the second part 22 engage with another slidably. In fact the finger seal 41 and/or the outer finger seal 42 protrude in a corresponding depression of the third part 23. This allows for thermal expansion and/or to counteract mechanical stress which otherwise could occur. By this finger seal configuration the second part 22 is attachable to the first part 21 - via the third part 23 - in a removable way. In other words, the first part 21 is removably attachable to the third part 23 and/or the second part 22 is removably attachable to the third part 23.

In the embodiment of figures 1 to 3 , the annular inner liner 15 and the annular outer liner 16 comprise a plurality of effusion holes 50 for letting compressed air (represented by arrows A) to enter the combustor 1) through the walls of the annular inner liner 15 and the outer liner 16, in order to cool the annular liners 15 and 16, respectively.

The embodiment of figure 4 is similar to the embodiment of figure 1, i.e it comprises the first, second and third parts 21, 22, 23 of the annular combustor independently attached to the gas turbine 3 and to the casing 5. The embodiment of figure 4 is different from the embodiment of figure 1 for the fact that the annular inner liner 15 and the annular outer liner 16 comprises one or more cooling passages 60 inside the respective liner 15, 16, for providing cooling by letting a flow of compressed air A enter the annular combustor 10 through the cooling passages 60. Each cooling passage 60 is obtained inside the walls of the annular inner liner 15 and the annular outer liner 16 by means of at least two panels 61, 62, respectively internal (i.e. facing the inner volume of the combustor 10, where hot gasses flow) and external (i.e. facing a volume external to the combustor 10, where compressed air A from the compressor 4 flows) . Each cooling passage 60 comprises an inlet 63, through which compressed air A enters the passage 60, and an outlet 64, through which compressed air A exits the passage 60 to enter the annular combustor 10.

According to other embodiments (not shown) of the present invention, mixed solutions are possible:

- the annular liners 15, 16 comprise both effusion holes 50 and cooling passages 60, for example on different zones of the annular liners 15, 16,

- one of the annular liners 15, 16 comprises effusion holes 50, while the other comprises cooling passages 60. To summarize previous sections, the combustor is not one large singular component but is split up into two or three parts, i.e. the combustor is a segmented combustor. This is achieved by mounting/suspending the backwall and liners individually. The liners can be mounted/suspended to a turbine module and a backwall to a central casing. One alternative is where the outer liner and the backwall are one component whilst the inner liner remains separate, see Figure 3. This would allow elimination of even more parts compared to a previous combustor design but will mean that the backwall will move due to thermal expansion in relation to the burner which can also be disadvantageous.

Due to the segmented approach different parts could be repaired/exchanged individually and disassembling the combustor would be a lot easier.

When the liners and the backwall/heat shield can move individually the interface between them become of importance. Leakage between liners and backwall is controlled using a seal design. This could be achieved using finger seals as demonstrated for example in Figures 1 or 4. Bolting the liners to the turbine module could make it much easier to control the interface between combustor and turbine. Also reducing the slot between the combustor and turbine makes it possible to improve the flow path aerodynamics of the transition between the combustor and turbine.

Repair would be made a lot easier and therefore also cheaper. It would also become possible to replace only a certain part (inner liner/outer liner/backwall ) on site because no cutting and welding would be needed.