COMBUSTION CHAMBER FOR A GAS TURBINE ENGINE

Abstract

A combustion chamber for a gas turbine engine includes: an inner wall delimiting an inner volume of the combustion chamber, through which combustion gas flow from a burner to a gas turbine of the gas turbine engine, a plurality of dampening cavities for the dampening of thermo-acoustic vibrations in the combustion gas, each dampening cavity communicating with the inner volume through at least a dampening hole on the inner wall, at least a cooling passage for a cooling medium flowing outside the inner volume in thermal contact with the inner wall, each dampening cavity having at least a purging hole communicating with the cooling passage for purging a portion of the cooling medium through the dampening cavities to the inner volume.

Claims

1-14. (canceled)

15. A combustion chamber for a gas turbine engine comprising: an inner wall delimiting an inner volume of the combustion chamber, through which combustion gas flow from a burner to a gas turbine of the gas turbine engine, a plurality of dampening cavities for the dampening of thermo-acoustic vibrations in the combustion gas, each dampening cavity communicating with the inner volume through at least a dampening hole on the inner wall, at least a cooling passage for a cooling medium flowing outside the inner volume in thermal contact with the inner wall, each dampening cavity comprising at least a purging hole communicating with the cooling passage for purging a portion of the cooling medium through the dampening cavities to the inner volume.

16. The combustion chamber according to claim 15, wherein each dampening cavity is delimited by the inner wall and by at least a side cavity wall, the purging hole being provided on the cavity wall.

17. The combustion chamber according to claim 15, wherein the combustion chamber further comprises an outer wall and an interspace between the inner wall and the outer wall, the plurality of dampening cavities and the cooling passage being provided in said interspace.

18. The combustion chamber according to claim 17, wherein the interspace annularly extends around the inner volume of the combustion chamber.

19. The combustion chamber according to claim 17, wherein the plurality of dampening cavities extends from one to the other of said inner wall and outer wall.

20. The combustion chamber according to claim 17, wherein at least a portion of dampening cavities are arranged along at least one row.

21. The combustion chamber according to claim 20, wherein the plurality of dampening cavities are arranged along a plurality of rows extending along a longitudinal direction parallel to the main flowing direction of the combustion gas inside the inner volume.

22. The combustion chamber according to claim 21, wherein the at least one cooling passage is provided between at least a couple of said rows of dampening cavities.

23. The combustion chamber according to claim 22, wherein the purging hole are arranged at a negative angle with respect to the cooling medium flowing in the cooling passage.

24. The combustion chamber according to claim 15, wherein the section of the cooling passage has a section narrowing along the direction of the flow of cooling medium inside the cooling passage.

25. The combustion chamber according to claim 15, wherein at least one of the dampening cavities comprises two side cavity walls in thermal contact with the cooling medium.

26. The combustion chamber according to claim 15, wherein at least one of the dampening cavities comprises three side cavity walls in thermal contact with the cooling medium.

27. The combustion chamber according to claim 17, wherein the plurality of dampening cavities are arranged are distributed according to a matrix pattern including a plurality of rows and columns.

28. The combustion chamber according to claim 17, wherein the plurality of dampening cavities are staggered.

29. The combustion chamber according to claim 20, wherein the plurality of dampening cavities are arranged along a plurality of rows extending along a longitudinal direction which is not parallel to the main flowing direction of the combustion gas inside the inner volume.

30. The combustion chamber according to claim 16, wherein the side cavity wall and/or the walls of the plurality of cooling passages is built via an additive manufacturing process.

31. A gas turbine engine comprising: a burner, a gas turbine, and a combustion chamber according to claim 15, between the burner and the gas turbine.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] 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.

[0033] FIG. 1 is a partial schematic view of a gas turbine engine including a combustion chamber, sectioned along a longitudinal direction,

[0034] FIG. 2 shows a schematic magnified view of the detail II of FIG. 1, as known in the prior art,

[0035] FIG. 3 shows a schematic magnified view of the detail II of FIG. 1, according to an embodiment of the present invention,

[0036] FIG. 4 shows a schematic cross-sectional view of the detail of a combustion chamber of FIG. 3, sectioned according to the line III-III of FIG. 3,

[0037] FIG. 5 shows a schematic sectional view of the detail of a combustion chamber of FIGS. 3 and 4, sectioned according to the circumferential surface IV-IV of FIG. 4,

[0038] FIG. 6 is an axonometric partial view of another embodiment of a combustion chamber, according to the present invention,

[0039] FIGS. 7, 8 and 9 respectively show three schematic plane projections of portions of a combustion chamber, according to three respective embodiments of the present invention.

DETAILED DESCRIPTION

[0040] Hereinafter, above-mentioned and other features of the present 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.

[0041] FIG. 1 shows an example of a gas turbine engine 1 in a partial schematic sectional view.

[0042] More in general, the schematic layout of FIG. 1 can be used also for describing a gas turbine engine according to the known prior art. In particular, the detail II in FIG. 1 can be represented by both the magnifications in FIGS. 2 and 3, respectively showing a known solution already described above and a solution according to the present invention, better detailed in the following.

[0043] The gas turbine engine 1 (not shown as a whole) comprises, in flow series, a compressor section (not shown), a burner 2 a combustor chamber 10 and a gas turbine 3, which are generally arranged in flow series. In operation of the gas turbine engine 1, air is compressed by the compressor section and delivered to the combustion section, including the burner 2 and the combustion chamber 10. The compressed air exiting from the compressor 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 longitudinal direction X oriented from the burner 2 to the gas turbine 3.

[0044] The combustion section, burner 2 and the gas turbine 3 are not a specific object of the present invention and, therefore, in the following, only the combustion chamber 10 will be described in further detail.

[0045] With reference to FIGS. 3, 4 and 5, a combustion chamber 10 according to the present invention comprises an inner wall 22 delimiting an inner volume V of the combustion chamber 10, through which a combustion gas flow from a burner 2 to a gas turbine 3 of the gas turbine engine 1, along the main longitudinal direction X. The combustion chamber 10 further comprises an outer wall 25 and an annular interspace 28 between the inner wall 22 and the outer wall 25. The interspace 28 annularly extends around the inner volume V of the combustion chamber 10.

[0046] In the interspace 28 a plurality of dampening cavities 30 for the dampening of thermo-acoustic vibrations in the combustion gas, each dampening cavity 30 communicating with the inner volume V through at least a dampening hole 40 on the inner wall 22. Each dampening cavity 30 represents a Helmoltz resonator having the following main geometrical parameters: —the volume Vc of the dampening cavity 30, —the cross sectional area A of the dampening hole 40, —the length L of the dampening hole 40.

[0047] Each dampening cavity 30 can be used to suppress a frequency f of the thermo-acoustic vibrations in the combustion gas inside the volume V, the frequency f being proportional to squared root of the ratio between area A and the product of volume Vc by the length L, i.e. in symbols:

f˜sqrt(A/(Vc*L).

[0048] Each dampening cavity 30 is delimited by the inner wall 22 and the outer wall 25 of the combustion chamber 10 and by at least two side cavity walls 42, 43, extending from one to the other of the inner wall 22 and the outer wall 25, orthogonally to the longitudinal direction X.

[0049] The two side cavity walls 42, 43 extends along the longitudinal direction X from the burner 2 to the gas turbine 3, in such a way that at least a portion of the dampening cavities 30 are arranged along at least one row 31, extending parallel to the longitudinal direction X. Two rows 31 are shown in the partial view of FIG. 5, but any number of rows 31 may be provided in the interspace 28 according to the present invention. In particular, according to a possible embodiment, a plurality of rows 31 may be distributed in the interspace 28 around the longitudinal direction X, regularly spaced from one another.

[0050] The interspace 28 further comprises at least a cooling passage 50, also extending from one to the other of said inner wall 22 and outer wall 25. In the embodiment of FIGS. 3, 4 and 5 a plurality of cooling passage 50 are provided.

[0051] Each cooling passage 50 is interposed between each couple of adjacent rows 31 of dampening cavities 30. Inside the cooling passage 50 a cooling medium flows outside the inner volume V, but in thermal contact with the inner wall 22. The cooling medium is typically a portion of the compressed air from the compressor section which by-passes the burner 2 and is channelled directly into the interspace 28. According to other possible embodiment of the present invention other cooling media may be used.

[0052] Each dampening cavity 30 comprises at least a purging hole 60 communicating with the cooling passage 50 for purging a portion of the cooling medium through the dampening cavities 30 to the inner volume V. The purging hole 60 is provided on one or both of the cavity walls 42, 43.

[0053] The purging holes 60 are normally of smaller dimensions with respect to the dampening holes 40, with a lower limit depending from the necessity of not getting blocked by solid particles, for example.

[0054] The purging holes 60 are arranged at a negative angle with respect to the cooling medium flowing in the cooling passage 50, in such a way that a dust trap can be arranged, making more difficult for dust or other solid particles to migrate from the cooling passage towards the dampening cavities 30 and the combustion chamber volume V.

[0055] According to other possible embodiments of the present invention, a great variety of geometrical arrangement of dampening cavities 30 and cooling passages 50 are possible. For example, dampening cavities 30 may be not arranged in rows, but quincuncially or staggered or according to any other pattern.

[0056] In particular, according to the embodiment in FIG. 6, the dampening cavities 30 may not extend from one to the other of the inner wall 22 and the outer wall 25, but comprise a third side cavity walls 44 in thermal contact with the cooling medium and spaced from the outer wall 25. In such embodiment, the third side cavity walls 44 extends parallel to the longitudinal direction X and comprises a plurality of purging holes 60 and more than one dampening hole 40 is present for a single dampening cavity. The cooling passage 50 is in contact with the three side cavity walls 42, 43, 44.

[0057] Other embodiments (not shown) may derive from combinations of the embodiment in FIGS. 3, 4 and 5 with the embodiment in FIG. 6, for example, according to the invention, it may be possible to have one of more dampening cavities 30 with one single dampening hole 40 and with the purging holes 60 on the two side cavity walls 42, 43 (like the embodiment in FIGS. 3, 4 and 5) but with a cooling passage 50 in contact with the three side cavity walls 42, 43, 44 (like the embodiment in FIG. 6).

[0058] Also the cooling passage 50 may vary from the straight geometry represented in FIGS. 4 and 5. For example, according to a possible embodiment (not shown), the cooling passage 50 has a section narrowing along the direction of the flow of cooling medium inside the cooling passage 50. Other geometries of the cooling passage may be possible, in order to control the overall cooling effect along the cooling passage.

[0059] In the cooling passage 50 the cooling medium flows mainly longitudinally, i.e. parallel to the longitudinal direction X, from a first longitudinal end to a second longitudinal end of the cooling passage 50.

[0060] According to one possible embodiment of the present invention, the cooling passage(s) 50 and the dampening cavities 30 are provided on the combustion chamber 10, for all its longitudinal extension along direction X and all its circumferential extension around direction X.

[0061] According to another possible embodiment of the present invention, only a reduced section of the combustion chamber 10, limited in its longitudinal extension along direction X or in its circumferential extension around direction X, comprises the cooling passages 50 and the dampening cavities 30. For example, the cooling passages 50 and the dampening cavities 30 may be provided only on one or more sections where the dampening of thermo-acoustic vibrations and/or the cooling requirements are particularly strong.

[0062] In particular with reference to three possible embodiments of the present invention, FIGS. 7, 8 and 9 respectively show three different geometrical arrangement patterns of dampening cavities 30 and of cooling passages 50 over the inner wall 22. Each of the dampening cavities 30 in FIGS. 7, 8 and 9 may be analogous to any of the damping cavities in FIGS. 3 to 6. In FIG. 7 dampening cavities 30 are distributed according to a matrix pattern including a plurality of rows and columns, respectively parallel and orthogonal to the longitudinal direction X. Each dampening cavity 30 is spaced from the others in both the directions, parallel and orthogonal to the longitudinal direction X. In FIG. 8 dampening cavities 30 are staggered. In both embodiment of FIGS. 7 and 8, cooling passages 50 surround each dampening cavity 30 as described with reference to the embodiment in FIG. 6. In FIG. 9 rows of dampening cavities 30 are used, similarly to the embodiment in FIGS. 3 to 5, but with the difference that rows in FIG. 9 are not parallel to the longitudinal direction X. The cooling passages 50 between the rows of dampening cavities 30 are consequently not parallel to the longitudinal direction X, too.

[0063] A great variety of different other geometries may be achieved, for example, by using additive manufacturing, instead of welding.

[0064] Particularly the side cavity wall 42 and/or 43 and/or the third side cavity walls 44 and/or the walls of the plurality of cooling passages 50 may be built by additive manufacturing techniques, for example by selective laser melting, selective laser sintering, electron-beam melting, selective heat sintering, or electron beam freeform fabrication. Particularly the solutions using lasers (e.g. selective laser melting, selective laser sintering) allow very fine structures and fine geometries.

[0065] By using additive manufacturing techniques, the optimal (complex) acoustic geometry can be established and also allow separation of each dampening hole on the cold side, making it possible to utilize less cooling air since each cavity only has one hole. Only a small purging flow is necessary in each cavity. The convective cooling of the wall is maintained in a separate channel in between the dampening cavities where only a small amount of air is bled off. By maintaining the main cooling stream straight and the bleeds in a negative angle, a dust trap can be arranged for these very small holes. The main channel can also be convergent if necessary to maintain convective heat transfer along the dampening segment of the combustion chamber wall. The dampening segment can be matched thermally with other parts of the combustion chamber to maintain mechanical integrity.

[0066] For all the geometry, it is essential that the cooling passages 50 are decoupled from the dampening cavities 30, in such a way that the convective cooling medium mainly flows in channels separated from the dampening cavities. The convective cooling relies primarily on the main flow of the cooling medium inside the passages 50, i.e. outside the dampening cavities 30, even if a small flow of cooling medium through the purging holes 60 and the dampening holes 40 is allowed for purging reasons.

[0067] In the sections of the combustion chamber 10 where the cooling passages 50 and the dampening cavities 30 are provided, the flow of the cooling medium is mainly longitudinal, inside the cooling passages 50, while a minor portion of the cooling medium enters the dampening cavities 30 through the purging holes 60 and the inner volume V through the dampening holes 40.

[0068] It is advantageous that the dampening cavities additionally act to provide cooling air to cool the inner wall 22, which is typically affected by the hot combustion zone.

[0069] The dampening cavities 30 may particularly be located close to heat release with the combustion volume, i.e. near the flame front. It may be located in a front panel or combustion liner. It may also or additionally be located close to where eigenmode largest fluctuation is present.

[0070] It may also be possible that the complete wall surrounding the combustion volume is equipped with a plurality of dampening cavities.

[0071] In the region where the dampening cavities are present, they may be arranged as a full ring provided with dampening cavities.

[0072] Particularly when using additive manufacturing, ring segments may be produced in which all walls are produced by an additive manufacturing process. The ring segments then will be attached to one closed ring, e.g. by welding. A smaller combustion chamber may be built as a full ring—a cylindrical component—without segmentation.

[0073] The shape of the “helmholtz volume” can be arbitrary, e.g. globe, conical, rectangular, honeycomb, etc. The shape of the holes may be round or oval, etc.

[0074] The dampening cavities—i.e. the “Helmholtz volume” can have different spacing in between. The different dampening cavities can be placed together or with a distance inbetween both tangential or axial direction.

[0075] It may be advantageous to have at least 1000 dampening cavities present in one combustion chamber.

[0076] Furthermore embodiments can be implemented without specific cooling passages 50 (as proposed in FIG. 5) but to simply have a plurality of dampening cavities that are each distant to another and the cooling air flows between the distinct dampening cavities.