CA2845192A1 - Combustor for gas turbine engine - Google Patents

Abstract

In a gas turbine combustor having an inner and outer liner defining an annular combustion chamber, at least an annular scoop ring provided on each inner and outer combustor liner. The annular scoop ring includes a solid radial inner base provided with bores defined therein and communicating with the combustion chamber to form air dilution inlets. The scoop ring has a radial outer portion in the form of a C-shaped scoop open to receive high velocity annular air flow. The bores of the inlets communicating with the scoop portion to direct the air flow into the combustion chamber whereby the bores of the inlets form jet nozzles to generate air jet penetration and direction within the combustion chamber.

Description

COMBUSTOR FOR GAS TURBINE ENGINE
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims priority on United States Patent Application Serial No. 13/795,089, filed on March 12, 2013, and incorporated herein by reference.
TECHNICAL FIELD

[0002] The present application relates to gas turbine engines and to a combustor thereof.
BACKGROUND OF THE ART

[0003] In combustors of gas turbine engines, an efficient use of primary zone volume in annular combustor is desired. An important component in improving the mixing within the primary zone of the combustor is creating high swirl, while minimizing the amount of components. It has been found however that high velocity outer annulus flow produces low local static pressure drop, and the inability to turn the flow to feed a row of large dilution holes at the inner and outer diameters of an annular combustor may result in poor hole discharge coefficient and low penetration angle of the air jets.
SUMMARY OF THE INVENTION

[0004] In one aspect, the present invention provides at least an annular scoop ring on a combustor liner defining a combustion chamber; the ring including a solid radial inner portion provided with bores defined in the ring and communicating with the combustion chamber to form air dilution inlets, and a radial outer portion in the form of a C-shaped scoop open to receive high velocity, annular air flow. The bores communicate with the scoop to direct the air into the combustion chamber wherein the bores form air jet nozzles to generate jet penetration and trajectory within the combustor.

[0005] In a more specific embodiment the radial thickness of the inner portion of the scoop ring must meet a minimum ratio of L/D=1 where L is the axial length of the bore and D is the diameter of the bore.

[0006] In a still more specific embodiment, the combustor is an annular combustor with inner and outer liners and there is at least an annular scoop ring on each inner and outer liner.

[0007] Further details of these and other aspects of the present invention will be apparent from the detailed description and figures included below.
DESCRIPTION OF THE DRAWINGS

[0008] Reference is now made to the accompanying figures depicting embodiments of the present invention, in which:

[0009] Fig. 1 is a schematic cross-sectional view of a turbofan gas turbine engine;

[0010] Fig. 2 is a side cross-sectional view of a combustor assembly in accordance with one embodiment;

[0011] Fig. 3 is a fragmentary perspective view of a detail shown in Fig.
2;

[0012] Fig. 4 is a fragmentary perspective view of another detail shown in Fig. 2;

[0013] Fig. 5 is a schematic section view showing an axial length to diameter ratio of a bore of a scoop ring of the combustor of Fig. 2;

[0014] Figs. 6A and 6B are respectively outer radial and section views of a scoop ring of the combustor, with internal guide vanes; and [0015] Figs. 7A and 7B are respectively outer radial and section views of a scoop ring of the combustor, with directional inlet holes.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Fig.1 illustrates a gas turbine engine 10 of a type preferably provided for use in subsonic flight, generally comprising in serial flow communication a fan 12 through which ambient air is propelled, a compressor section 14 for pressurizing the air, a combustor 16 in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section 18 for extracting energy from the combustion gases.

[0017] The combustor 16 is illustrated in Fig. 1 as being of the reverse-flow type;
however the skilled reader will appreciate that the description herein may be applied to many combustor types, such as straight-flow combustors, radial combustors, lean combustors, and other suitable annular combustor configurations. The combustor 16 has an annual geometry with an inner liner 20 and an outer liner 30 defining therebetween an annular combustor chamber in which fuel and air mix and combustion occurs. As shown in figure 2, the upstream end A of the combustor 16 may contain a manifold, fuel and air nozzles.
Downstream, is the mixing channel B which includes channel walls 50 and 60 providing a narrow, annular throat favoring complete mixing of the fuel and air. The inner and outer liners 20 and 30 flare out, downstream of the mixing channel B into the dilution zone C, within the combustion zone.

[0018] The present description is focused on the dilution zone C.
Complementary to this description, US Patent Application Serial No. 13/795,089, mentioned above, is incorporated herein by reference.

[0019] The liners 20 and 30 are provided with various patterns of cooling inlets represented by the 27 in liner 20, for instance. Annular scoop rings 70 and 80 are provided as integral to the liners 20 and 30 respectively. The scoop rings 70, 80 may also be separately fabricated and welded to the liners. Associated with annular rings 70 and 80 are patterns of air diluting inlets 26, 36, respectively.

[0020] Annular ring 80 will now be described in detail. Annular ring 70 is similar to annular ring 80. Annular ring 80 includes a radially inner portion 82 in the form of an annular, solid block, i.e., having a greater thickness than the surrounding liner. A C-Shaped or U-shaped appendage extends radially outwardly from the inner block forming an air scoop 84, open to receive the annular flow air. The dilution air inlets 36 and cooling inlets 37 are in the form of bores extending through the solid block of the inner portion 82 and communicating with the combustion chamber. As described in the above mentioned US Patent Application Serial No. 13/795,089, the bores forming the inlets 36 and 37 will be oriented individually at predetermined directions, either at an angle to the radial axis, such as tangential, acute or obtuse depending on the penetration or swirl required of the air jets formed by the bores making up the inlets 36 and 37.

[0021] In order to ensure the formation of air jets by means of the bores making up inlets 36, the radial thickness of the inner block portion 82 must be sufficient to meet a minimum ratio of L/D=1 where L is the axial length of the bore and D is the diameter of the bore (as shown in Fig. 5). The thickness of the inner block portion may be greater, thus increasing the bore length. The block portions may be integrally formed with the liner, or attached thereto (e.g., welding, etc).

[0022] The provision of the scoop portion 84 immediately adjacent the inlets 36 captures the dynamic head in the outer air flow to increase the inlet feed static pressure and for a better right angle turn into the inlets 36. The jet flow formed by the bores, defining the inlets 36, result in improved discharge coefficient, higher pressure drop and deeper jet penetration.

[0023] Referring to Fig. 4, dilution air inlets 36 are circumferentially distributed on the respective scoop ring 80, in the dilution zone C of the combustor 16.
According to an embodiment, the dilution air inlets 26 and 36 are equidistantly distributed, and opposite one another across the combustion chamber. It is observed that the central axis of one or more of the bores forming the dilution air inlets 26 and 36, generally shown as D, may have an axial component and/or a tangential component, as opposed to being strictly radial.
Referring to Fig. 4, the central axis D is oblique relative to a radial axis R of the combustor 16, in a plane in which lies a longitudinal axis X of the combustor 16. Hence, the axial component DX of the central axis D is oriented downstream, i.e., in the same direction as that of the flow of the fuel and air, whereby the central axis D leans towards a direction of flow (for instance generally parallel to the longitudinal axis X). In an embodiment, the central axis D
could lean against a direction of the flow.

[0024] It should however be understood that the inlets 26 and 36 may have both the axial component DX and the tangential component DZ. The tangential component DZ is oblique relative to radial axis R in an axial plane, i.e., the axial plane being defined as having the longitudinal axis X of the combustor 16 being normal to the axial plane. In Fig. 4, the tangential component DZ is in a counter clockwise direction.

[0025] Referring to Fig. 4, the plurality of cooling air inlets 27 may be defined in the inner liner 20 and at least cooling air inlets 37 in the scoop ring 80 relative to liner 30. The scoop ring 80 has a set of dilution air inlets 37 in an alternating sequence with the set of dilution air inlets 36. The dilution air inlets 37 have a smaller diameter than that of the dilution air inlets 36. This alternating sequence is a configuration considered to maximize the volume of dilution in a single circumferential ring.

[0026] The scoop portion 84, of the scoop ring 80, is open upstream to the direction of annular airflow, in other words, downstream relative to the direction of flow within the combustion chamber, while the scoop 74 of scoop ring 70 is open upstream to the reverse direction of annular airflow adjacent the liner 20, but upstream to the direction of flow of fuel and air within the combustion chamber. Hence, the scoop rings 70 and 80 face opposite directions, although they could face a similar direction as well. The shape of the scoop portion 74, 84 of the scoop ring 70, 80 may be of various open configurations such as U-shaped, C-shaped or other open shapes. The scoop portion 84 includes a forward extending lip 84a which may be designed at a selected angle and extension length to optimize the air entrance trajectory and the feed static pressure. For the purposes of this description, the term C-shape is meant to cover the various shapes. Slots 85 may be provided in the scoop portion 84 to relieve any hoop stresses. Like slots may also be provided in the scoop ring 70.

[0027] The openings to the diluting air inlets 26, 36 are located on the inner surface of the scoop portion 74, 84, near the bight of the C-shaped portion. The figures show a single row of inlets 26, 27, 36, 37, but multiple rows are considered as well.
Sectional dimensions for the inlets 26, 27, 36, 37 may also vary. Referring to Fig. 5, one of the scoop rings 70 and 80 is illustrated as having dimensions d, I and h, and angles a and [3 that can be adjusted in order to obtain the desired effect, for instance to optimize the entrance trajectory and feed static pressure in the case of angle (3.

[0028] Referring to Figs. 6A and 6B, internal guide vanes 90 may be provided in the scoop rings 70 and/or 80, to give tangential direction to the incoming flow, hence providing control of the tangential component of the air jet entering the combustor.
Alternatively, or additionally, referring to Figs. 7A and 7B, directional inlet holes 100 may be provided in the scoop rings 70 and/or 80, for the same tangential component purpose. In the case of directional inlet holes 100, they are defined in a radial block 101 added in the scoop rings 70 and/or 80.

[0029] The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. For instance, the annular scoop rings 70, 80 may be present on the outer liner, on the inner liner, or in tandem, so as to obtain the desired mass flow rate and flow feature. Other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.

Claims (18)

WHAT IS CLAIMED IS:

1. A gas turbine combustor comprising an annular liner defining a portion of a combustion chamber; at least an annular scoop ring on the annular liner; the ring comprising a solid radial inner portion provided with bores defined therein and communicating with the combustion chamber to form air dilution inlets; the scoop ring having a radial outer portion to define a C-shaped scoop open to receive annular air flow; the bores of the inlets communicating with the scoop to direct the air flow into the combustion chamber; the bores of the inlets being oriented to generate air jet penetration and direction within the combustion chamber.

2. The combustor as defined in claim 1 wherein the radial thickness of the solid radial inner portion of the scoop ring has a ratio of at least L/D=1 where L is the axial length of the bore and D is the diameter of the bore.

3. The combustor as defined in any one of claims 1 and 2 wherein the combustor is an annular combustor and wherein said annular liner is defined by an inner liner and an outer liner; the annular scoop ring comprising an inner annular scoop ring provided on the inner liner and an outer annular scoop ring on the outer liner with the C-shaped scoop being on the inner annular scoop ring and on the outer annular scoop ring, the C-shaped scoops being open to receive the annular air flow for directing the air into the combustion chamber.

4. The combustor as defined in claim 3 wherein the radial thickness of the inner portion of the scoop ring has a ratio of at least L/D=1 where L is the axial length of the bore and D is the diameter of the bore.

5. The combustor as defined in any one of claims 3 and 4 wherein cooling air inlets are provided in an alternating sequence with the dilution air inlets on the inner portion of the outer annular scoop ring.

6. The combustor as defined in any one of claims 3 and 4 wherein cooling air inlets are provided in patterns at least in the inner liner.

7. The combustor as defined in claim 6 wherein the dilution air inlets and the cooling air inlets are provided at least in the dilution zone of the combustion chamber.

8. The combustor as defined in any one of claims 1 to 7, wherein a central axis of at least one of the bores of the inlet has a tangential component relative to a central axis of the annular combustor chamber.

9. A combustor for a gas turbine engine comprising a liner defining a combustion chamber, a plurality of diverting air inlets provided in a pattern on the liner; each diverting air inlet provided with a scoop comprising an inner base portion and radially outward C-shaped scoop portion to receive annular air flow; a bore defined in the base portion communicating the scoop portion with the combustion chamber to provide a jet nozzle for the air diverted by the scoop portion.

10. The combustor as defined in claim 9 wherein the radial thickness of the base portion of the scoop has a ratio of at least L/D=1 where L is the axial length of the bore and D is the diameter of the bore.

11. A gas turbine engine comprising:
a combustor comprising:
an annular liner defining a portion of a combustion chamber;
at least an annular scoop ring on the annular liner, the ring comprising a solid radial inner portion provided with bores defined therein and communicating with the combustion chamber to form air dilution inlets, the scoop ring having a radial outer portion to define a C-shaped scoop open to receive annular air flow, the bores of the inlets communicating with the scoop to direct the air flow into the combustion chamber, the bores of the inlets being oriented to generate air jet penetration and direction within the combustion chamber.

12. The gas turbine engine as defined in claim 11 wherein the radial thickness of the solid radial inner portion of the scoop ring has a ratio of at least L/D=1 where L is the axial length of the bore and D is the diameter of the bore.

13. The gas turbine engine as defined in any one of claims 11 and 12 wherein the combustor is an annular combustor and wherein said annular liner is defined by an inner liner and an outer liner; the annular scoop ring comprising an inner annular scoop ring provided on the inner liner and an outer annular scoop ring on the outer liner with the C-shaped scoop being on the inner annular scoop ring and on the outer annular scoop ring, the C-shaped scoops being open to receive the annular air flow for directing the air into the combustion chamber.

14. The gas turbine engine as defined in claim 13 wherein the radial thickness of the inner portion of the scoop ring has a ratio of at least L/D=1 where L is the axial length of the bore and D is the diameter of the bore.

15. The gas turbine engine as defined in any one of claims 13 and 14 wherein cooling air inlets are provided in an alternating sequence with the dilution air inlets on the inner portion of the outer annular scoop ring.

16. The gas turbine engine as defined in any one of claims 13 and 14 wherein cooling air inlets are provided in patterns at least in the inner liner.

17. The gas turbine engine as defined in claim 16 wherein the dilution air inlets and the cooling air inlets are provided at least in the dilution zone of the combustion chamber.

18. The gas turbine engine as defined in any one of claims 11 to 17 wherein a central axis of at least one of the bores of the inlet has a tangential component relative to a central axis of the annular combustor chamber.