Combustor of gas turbine engine and method

A combustor for a gas turbine engine includes a liner enclosing a combustion chamber and defining air passages through the liner, a fuel nozzle fluidly connected to the combustion chamber, and a louver disposed inside the combustion chamber over the air passages. The louver extends circumferentially along the liner and is connected to the liner by a fastener. The fastener spacing at least one of axial edges of the louver from the liner to define an air outlet between the at least one of the axial edges and the liner. A method of manufacturing a combustor of an aircraft engine is also disclosed.

TECHNICAL FIELD

The application relates to combustors for gas turbine engines.

BACKGROUND OF THE ART

While prior art combustors for gas turbine engines may be suitable for their intended purposes, improvements in aviation technologies are always desirable.

SUMMARY

In one aspect, there is provided a combustor for a gas turbine engine having a rotation axis, the combustor comprising: a liner enclosing a combustion chamber extending along an axial direction relative to the rotation axis, the liner defining air passages through the liner into the combustion chamber, a fuel nozzle fluidly connected to the combustion chamber upstream of the air passages, and a louver disposed inside the combustion chamber over the air passages, the louver extending circumferentially along the liner relative to the rotation axis from a first circumferential end of the louver to a second circumferential end of the louver and having a front-facing axial edge facing toward the fuel nozzle and a rear-facing axial edge facing away from the fuel nozzle, the louver connected to the liner by a fastener, the fastener spacing at least one of the axial edges from the liner to define an air outlet between the at least one of the axial edges and the liner.

In some embodiments, the at least one of the axial edges is the front-facing axial edge and the air outlet is an only air outlet in a radial direction between the front-facing axial edge the liner; and the rear-facing axial edge and the liner define a rear-facing air outlet between the rear-facing axial edge and the liner, the rear-facing air outlet extending from the first circumferential end of the louver to the second circumferential end of the louver.

In some embodiments, combustor comprises a divider wall extending from the liner to the louver, the divider wall disposed between the front-facing and rear-facing air outlets and between the air passages such that some of the air passages supply air to the front-facing air outlet and a rest of the air passages supply air to the rear-facing air outlet.

In some embodiments, the liner includes an annular outer liner extending about a central axis of the combustor; the louver and the divider wall extend circumferentially along a portion of the outer liner relative to the central axis; and an end wall is disposed at each of opposed circumferential ends of the louver, the end walls defining the front-facing and rear-facing air outlets.

In some embodiments, the front-facing air outlet has a total airflow exit area that is between 2 to 3 times a total airflow exit area of the air passages supplying air to the front-facing air outlet, and the rear-facing air outlet has a total airflow exit area that is between 2 to 3 times a total airflow exit area of the air passages supplying air to the rear-facing air outlet.

In some embodiments, the total airflow exit area of the air passages supplying air to the front-facing air outlet is greater than the total airflow exit area of the air passages supplying air to the rear-facing air outlet.

In some embodiments, the combustor comprises a plurality of thumbnail air outlets disposed on a side of the louver opposite the divider wall, each of the thumbnail air outlets being fluidly connected to at least one of: the first air passages, and an air source disposed outside of the liner; the combustion chamber includes a primary zone in a front portion of the combustion chamber, and a dilution zone downstream of the primary zone; the louver, the divider wall, and the first air passages are positioned between the primary zone and the dilution zone; the liner defines therethrough air passages opening into the primary zone of the combustion chamber; the liner includes an annular inner liner, the inner liner defining at least one primary jet air passage through the inner liner, the at least one primary jet air passage opening into the combustion chamber between the primary zone and the dilution zone; and the air passages opening into the primary zone and the at least one primary jet air passage are sized and oriented such that air flowing into the combustion chamber during operation through the air passages opening into the primary zone and the at least one primary jet air passage generates a toroidal flow of combustion gases in the primary zone, the toroidal flow of combustion gases impinging upon the louver and the thumbnail air outlets.

In some embodiments, the louver, the divider wall, the front-facing and rear-facing air outlets, and the thumbnail air outlets are part of an air film starter threadingly attached to the outer liner; the air film starter is a plurality of film starters distributed circumferentially along the outer liner; the fuel nozzle is a plurality of fuel nozzles disposed upstream of the plurality of film starters; and each fuel nozzle of the plurality of fuel nozzles aligns axially with at least one film starter of the plurality of film starters.

In some embodiments, the plurality of film starters covers substantially an entirety of a circumference of the outer liner.

In some embodiments, the louver has a rectangular cross-section.

In another aspect, there is provided a combustor for a gas turbine engine, the combustor comprising: an outer liner and an inner liner defining an annular combustion chamber between the outer liner and the inner liner; a fuel nozzle disposed in a front portion of the combustion chamber; a plurality of air passages defined through the outer liner downstream of the fuel nozzle; and an air film starter disposed inside the combustion chamber and connected to the outer liner via a threaded stud, the air film starter defining: a front-facing elongate air outlet directing air from at least one of the plurality of air passages along the outer liner toward the fuel nozzle when the combustor is in use; and a rear-facing elongate air outlet directing air from at least one of the plurality of air passages along the outer liner away from the fuel nozzle when the combustor is in use.

In some such embodiments, the air film starter includes a louver disposed inside the combustion chamber proximate to and spaced from the outer liner, and opposed axial edges of the louver define respective ones of the front-facing and rear-facing elongate air outlets between respective ones of the opposed axial edges and the outer liner.

In some such embodiments, the front-facing elongate air outlet extends radially inward of the outer liner; and the rear-facing elongate air outlet extends radially inward of the outer liner.

In some such embodiments, the threaded stud is one of: a plurality of bolts distributed circumferentially along the outer liner and extending into the combustion chamber through the outer liner and connecting to the air film starter; and a plurality of threaded studs extending from the air film starter out of the combustion chamber through the outer liner.

In some such embodiments, the air film starter includes a divider wall extending from the outer liner to the louver between opposed circumferential ends of the louver, and an end wall at each of the opposed circumferential ends, the end walls defining the front-facing and rear-facing elongate air outlets, the divider wall fluidly separating the plurality of air passages into: at least a first air passage supplying air to the front-facing elongate air outlet when the combustor is in use, and at least a second air passage supplying air to the rear-facing elongate air outlet when the combustor is in use.

In some such embodiments, the air film starter is coated with a Platinum-Aluminide coating.

In some such embodiments, the air film starter is one of: cast, made as a single crystal, and metal injection molded, from a B1900Hf alloy.

In yet another aspect, there is provided a method of manufacturing a combustor of an aircraft engine, comprising: forming an outer liner and an inner liner to define a combustion chamber of the combustor; fluidly connecting a fuel nozzle to a front portion of the combustion chamber for injecting fuel into a primary zone of the combustion chamber; forming air passages through the outer liner and the inner liner around the primary zone to provide an air supply pattern into the primary zone that creates a toroidal flow of combustion gases in the primary zone during operation of the combustor, the toroidal flow impinging upon a circumferential portion of the outer liner downstream of the fuel nozzle; forming an air passage through the outer liner in the circumferential portion of the outer liner; and attaching a louver via a fastener to the outer liner at a location opposite the air passage inside the combustion chamber such that an axial edge of the louver is spaced from the outer liner to define an elongate air outlet between the axial edge and the outer liner.

In some embodiments, the axial edge is one of two opposed axial edges of the louver, and the attaching the louver via the fastener spaces both of the opposed axial edges from the outer liner to define opposed elongate air outlets, the elongate air outlet being one of the opposed elongate air outlets.

In some embodiments, the method comprises attaching the fastener to a side of the louver facing the outer liner at a location between the opposed axial edges.

In yet another aspect, there is provided a method of creating an air film in a combustion chamber of a combustor of an aircraft engine, comprising: during operation of the combustor, supplying air into a primary zone of the combustion chamber to generate a toroidal flow of combustion gases in the primary zone, the toroidal flow of combustion gases impinging upon a circumferential portion of an outer liner defining/enclosing the combustion chamber; and supplying air into the combustion chamber along the outer liner from front-facing elongate air outlets spanning the circumferential portion of the outer liner.

In some such embodiments, the method further comprises supplying air into the combustion chamber along the outer liner from rear-facing elongate air outlets spanning the circumferential portion of the outer liner.

In some such embodiments, the method further comprises supplying air into the combustion chamber in a circumferential direction along the circumferential portion of the outer liner from outlets positioned radially inward of the front-facing and the rear-facing elongate air outlets relative to a central axis of the combustor.

DETAILED DESCRIPTION

While the air film starter technology of the present application is described herein with respect to a particular type of aircraft engine and combustor, the air film starter technology of the present application may likewise be used with other types of aircraft engines and/or other types and/or embodiments of combustors. Axial (XA), radial (XR), circumferential (XC), axially forward (F), and axially rearward (R) directions as referred to in the present document are shown with corresponding arrows in the figures. Various airflows and air passages have been shown with arrows in the figures.

To maintain clarity of the figures, only some of the airflows and passages have been labeled. For the purposes of this document, the term “elongate outlet” is used to distinguish the outlet from circular outlets, and means that the outlet has a width or length, depending on the orientation of the outlet, which is greater than its height. Further, for the purposes of this document, the term “outlet” means an outlet defined by two or more surfaces that are spaced from each other, and excludes a gap that may be left between two surfaces abutting each other and/or being compressed against each other, which gap may pass airflow therethrough.

FIG. 1Aillustrates an aircraft engine1A, which may be part of an aircraft, such as a conventional aircraft for example. In this example, the engine1A is a turboshaft engine1A, but may be any other type of aircraft engine. In this embodiment, the engine1A includes in serial flow communication a low pressure compressor section (LPC) and a high pressure compressor section (HPC) for pressurizing air. The engine1A further includes a high pressure turbine section (HPT) and a lower pressure turbine section (LPT). The respective pairs of the compressor and turbine sections are interconnected via respective independently rotatable low pressure and high pressure spools (LPS), (HPS). The engine1A includes a transmission (T) driven by the low pressure turbine section (LPT) for outputting motive power to an aircraft.

The engine1A further includes a combustor10in which the compressed air is mixed with fuel and ignited for generating combustion gases that may be used to power the high pressure turbine section (HPT) and a lower pressure turbine section (LPT). In this embodiment, the combustor10is of an annular type and has a central axis10X. The combustor10is disposed about a rotation axis (X) of the engine1A such that the central axis10X of the combustor10coincides with the rotation axis (X) of the engine1A. It is contemplated that in some embodiments and applications, a different arrangement may be used.

FIGS. 1B and 10illustrate the combustor10in more detail. As shown, in this embodiment, the combustor10includes a liner12. The liner12includes an annular outer liner12A and an annular inner liner12B that together define/enclose a combustion chamber16between the outer liner12A and the inner liner12B. A plurality of fuel nozzles14are disposed in and/or extend and/or open into a front portion16F of the combustion chamber16. In this embodiment, the fuel nozzles14are distributed circumferentially about the front portion16F of the combustion chamber16, as shown with dotted lines inFIG. 10to maintain clarity of the figure. To maintain clarity of the figures and this description, only one of the fuel nozzles14is labeled and only two of the fuel nozzles14are shown inFIG. 10. It is contemplated that the combustion chamber16may include any number and any arrangement of fuel nozzles14suitable for each particular embodiment and application of the combustion chamber16.

Referring toFIG. 1B, as shown with arrow (FF), each of the fuel nozzles14is operable to inject fuel into a primary zone18P of the combustion chamber16. During operation, the fuel (FF) is mixed with air (A) supplied into the primary zone18P of the combustion chamber16via a first set of air passages20defined through the outer and inner liners12A,12B in the primary zone18P of the combustion chamber16. To maintain clarity of the figures and this description, only one of the air passages20is labeled and only two of the air passages20are shown with parallel lines traversing the liner12. The rest of the air passages20are shown with arrows (A), only some of which are labeled to maintain clarity. The resulting fuel-air mixture is combusted in the combustion chamber16. The combustion creates combustion gases that flow from the combustion chamber16to the various components, such as the high pressure turbine section (HPT) and the lower pressure turbine section (LPT) of the engine1A to power the engine1A.

It is contemplated that any suitable ignition and/or flame holding arrangement may be used to initiate and/or maintain combustion, and therefore these elements are not described in detail herein. It is contemplated that any suitable fluid connection(s) and/or shape of the combustor10may be used for directing the combustion gases through the engine1A. Therefore, to maintain clarity, these elements and details are not described in detail herein.

In this embodiment, the combustor10further includes one or more primary air jet louvers22disposed circumferentially along, as shown with arrow (XC) inFIG. 1c, and/or defined by the inner liner12B. As shown, the primary air jet louvers22span a circumferential portion of the inner liner12B, which is disposed between the primary zone18P of the combustion chamber16and a dilution zone18D of the combustion chamber16that is downstream of the primary zone18P. More particularly, as shown inFIG. 10, the primary air jet louvers22define front-facing (i.e. facing the front portion16F of the combustion chamber16) elongate air outlets22L that span substantially the entirety of the circumferential portion12C of the inner liner12B, as shown with dotted lines inFIG. 10to maintain clarity of the figure. To maintain clarity, only one of the elongate air outlets22L, further referred to as “inner elongate air outlets22L”, is labeled and only two of the inner elongate air outlets22L are shown in their entirety inFIG. 1C. It is contemplated that the combustion chamber16may include any number and/or configuration and/or shape of inner elongate air outlets22L suitable to provide for the functionality described herein.

The primary air jet louvers22thus define air passages that include the inner elongate air outlets22L and direct air flowing into the combustion chamber16via air passages20corresponding to the primary air jet louvers22(i.e. the air passages20disposed radially inward of the louvers22), along the inner liner12B toward the front portion16F of the combustion chamber16, and hence toward the fuel nozzles14. As shown inFIG. 1B, the first set of air passages20and the inner elongate air outlets22L (a.k.a. primary jet air passages22L) are sized and oriented such that air (A) flowing into the combustion chamber16during operation of the combustor10through the first set of air passages20and the inner elongate air outlets22L generates a toroidal flow16G of combustion gases in the primary zone18P of the combustion chamber16.

As shown with arrow16GD, the toroidal flow16G impinges upon a circumferential portion26of the outer liner12A. From the primary zone18P, the combustion gases flow axially rearward downstream of the circumferential portion26into and through the dilution zone18D of the combustion chamber16. Thus, the circumferential portion26of the outer liner12A may be said to be disposed between the primary zone18P and the dilution zone18D, and/or may be part of the primary zone18P and/or the dilution zone18D.

Referring toFIGS. 1B and 10, in the present embodiment, to help protect the circumferential portion26of the outer liner12A, the combustor10includes a plurality of air film starters28. To maintain clarity, only one of the air film starters28is labeled and only two of the air film starters28are shown in their entirety inFIG. 10. As schematically shown inFIG. 10with dotted lines to maintain clarity of the figure, in this embodiment, the film starters28are distributed and extend circumferentially along the outer liner12A and span substantially an entirety of the circumferential portion26of the outer liner12A. In an aspect, this arrangement helps protect an entirety of the circumferential portion26from the heat of the impinging portion16GD of the toroidal flow16G of the combustion gases.

In the present embodiment, the number of the air film starters28equals to the number of the fuel nozzles14, with one air film starter28being aligned axially with a corresponding one of the fuel nozzles14as shown inFIG. 10. In at least some embodiments, each given fuel nozzle14may generate a fuel and/or combustion gas flow pattern that may be different from the fuel and/or combustion gas flow pattern of one or more of the other fuel nozzle(s)14, if any. Hence, in an aspect, a 1-to-1 air film starters28to fuel nozzles14arrangement may help provide a more efficient combustion pattern for each of the fuel nozzle(s)14.

In some embodiments, the combustor10may have a different air film starters28to fuel nozzles14arrangement. For example, in some embodiments, the number of the air film starters28may be a multiple of the number of the fuel nozzles14. As a more particular non-limiting example, in some embodiments, the number of the air film starters28may be ½ of the number of the fuel nozzles14. In some such embodiments, each air film starter28may be sufficiently long in the circumferential direction (XC) so as to axially align with two corresponding fuel nozzles14and/or to cover with a film of air the portion of the circumferential portion26of the outer liner12A that may otherwise be contacted by combustion gases produced by the two corresponding fuel nozzles14.

In some embodiments, the air film starters28may be similar to each other. In other embodiments, one or more of the air film starters28may be different from each other such as by having one or more different features and/or one or more different shape(s) and/or dimension(s) selected to suit the corresponding fuel nozzle(s)14. To maintain clarity of this description, various embodiments of the construction of only one of the air film starters28are described in detail herein next, with reference toFIGS. 2A to 2C. It is noted that for simplicity, the arcuate portion of the annular outer liner12A, and the one of the air film starters28, shown inFIGS. 2A to 2Care both shown as straight elements. It is contemplated that the outer liner12A and the air film starters28may have any suitable one or more curvatures and shapes to suit each particular embodiment and size of the combustor10.

Referring toFIG. 2A, in the present embodiment, the air film starter28includes a louver30disposed inside the combustion chamber16proximate to and spaced, as shown with arrows (SP1) and (SP2), from the outer liner12, over air passages20A,20B defined through the outer liner12that bring air (A) into the combustion chamber16. The louver30is connected to and spaced from the outer liner12A using one or more threaded studs32, which may are examples of fasteners that may be integral to or attached to the louver30. As shown, the one or more threaded studs32may extend through the liner12A, and may space the louver30from the outer liner12such that a front-facing axial edge28E′ of the louver30defines a front-facing (i.e. facing the front portion16F of the combustion chamber16) elongate air outlet28F between the front-facing axial edge28E′ and the outer liner12A, and such that a rear-facing axial edge28E″ of the louver30defines a rear-facing (i.e. facing away from the front portion16F of the combustion chamber16) elongate air outlet28R between the rear-facing axial edge28E″ and the outer liner12A.

As shown inFIGS. 1cto 2cfor example, in this embodiment, each of the air outlets28F,28T receives air from one or more of the air passages20A,20B. In this embodiment, each of the air outlets28F,28T extends from a first circumferential end (at wall28W) of the louver30to a second circumferential end (at the other wall28W of the louver30, opposite the first circumferential end) of the louver30, with no structures and hence no impedances to airflow extending across either of the air outlets28F,28T. While the no-structure/impedance embodiments may provide advantages in cooling efficiency for example, it is contemplated that in some embodiments, one or more structures, such as a mesh for example, may extend across one or both of the elongate air outlets28F,28T. It is contemplated that in some embodiments, the air film starter28may define only one of the front-facing elongate air outlet28F and the rear-facing elongate air outlet28R for example.

The spacings (SP1) and (SP2) referred to above are measured along a radial direction between the respective axial edges28E′,28E″ and the respective parts of the outer liner12A. Further as seen inFIG. 1B, in this embodiment, the front-facing elongate air outlet28F extends radially (XR) inward of the outer liner12A, and the rear-facing elongate air outlet28R extends radially (XR) inward of the outer liner12. Also in this embodiment, and although need not be the case in other embodiments, the liner12A proximate to the air film starter28A has a cross section that is free of material cavities or depressions. In some embodiments, the spacing (SP1) is equal to the spacing (SP2).

In some embodiments, the spacing (SP1) may be selected such that a total airflow exit area of the front-facing elongate air outlet28F may be between 1.5 to 4 times a total airflow exit area of the air passages20A and/or20B (as applicable in each embodiment) supplying air to the front-facing elongate air outlet28F. In some embodiments, the spacing (SP1) may be selected such that the total airflow exit area of the front-facing elongate air outlet28F may be between 2 to 3 times a total airflow exit area of the air passages20A and/or20B (as applicable in each embodiment) supplying air to the front-facing elongate air outlet28F. In some embodiments, the spacing (SP2) may be selected such that a total airflow exit area of the rear-facing elongate air outlet28R may be between 1.5 to 4 times a total airflow exit area of the air passages20B and/or20A (as applicable in each embodiment) supplying air to the rear-facing elongate air outlet28R.

In some embodiments, the spacing (SP2) may be selected such that the total airflow exit area of the rear-facing elongate air outlet28R may be between 2 to 3 times the total airflow exit area of the air passages20B and/or20A (as applicable in each embodiment) supplying air to the rear-facing elongate air outlet28R. In some embodiments, the spacing (SP1) may be larger than the spacing (SP2) to provide for more airflow through the front-facing elongate air outlet28F than through the rear-facing elongate air outlet28R. In some applications, such an unequal flow distribution may help protect at least a part of the outer liner12A that defines the primary zone18P which may be hotter than the dilution zone18D.

Although the above arrangements and/or ranges of airflow exit areas may provide advantages in some applications, in other embodiments, the spacing (SP1) may be different from the spacing (SP2) and/or the spacings (SP1), (SP2) may have different magnitudes that may not fall into the abovementioned ranges.

Referring toFIGS. 2A to 2C, although this may not be the case in other embodiments, in the present embodiment the louver30has a straight rectangular cross section. Also in this embodiment, the louver30is elongate and arcuate in the circumferential direction (XC). Also in this embodiment, the louver30has no walls extending along an entirety of its curved length in the circumferential direction (XC). In this embodiment, the curvature of the louver30conforms to the curvature of the outer liner12A, however in other embodiments this may not be the case. While the straight rectangular cross section may provide advantages in, for example, at least some aspects of manufacturing of the present embodiment, in other embodiments, the louver30may have one or more different cross sections, such as one or more curved and/or arced rectangular and/or non-rectangular cross sections.

As best shown inFIGS. 2B and 2C, the outer liner12A defines therethrough the air passages20A,20B over which the louver30is positioned. The passages20A,20B may be fed with air (A) from any suitable air source(s) outside of the combustion chamber16. Thus, as shown, the louver30is disposed over the air passages20A,20B and faces the air passages20A,20B. The louver30thereby redirects air flowing/being supplied into the combustion chamber16via the air passages20A,20B out of the front-facing and the rear-facing elongate air outlets28F,28R.

In this embodiment, and although this need not be the case in other embodiments, the air film starter28includes a divider wall34. In this embodiment, the divider wall34extends from the outer liner12A to the louver30and is disposed between the front-facing and rear-facing elongate air outlets28F,28R, and in this embodiment also between the air passages20A,20B. More particularly, the divider wall34extends between the air passages20A and the air passages20B, between opposed circumferential ends of the louver30. The divider wall34forces air flowing through the air passages20A to flow out of the front-facing elongate air outlet28F, and the air flowing through the air passages20A to flow out of the rear-facing elongate air outlet28R.

Stated otherwise, the divider wall34may fluidly separate the plurality of air passages20A,20B into: at least a first air passage20A supplying air to the front-facing elongate air outlet28F when the combustor10is in use, and at least a second air passage20B supplying air to the rear-facing elongate air outlet28R when the combustor is in use. It is contemplated that any number of the air passages20A and the air passages20B may be used to suit each particular embodiment of the combustor10, including for example an appropriately dimensioned single air passage20A and an appropriately dimensioned single air passage20B.

In an aspect, the divider wall34helps predefine and/or control the magnitude of the airflow coming out of each of the front-facing elongate air outlet28F and the rear-facing elongate air outlet28R. As a non-limiting example, in some embodiments, the air passages20A and the front-facing elongate air outlet28F may be dimensioned to provide an effective airflow diameter that is larger than an effective airflow diameter provided by the air passages20B and the rear-facing elongate air outlet28R. This may help provide more airflow out of the front-facing elongate air outlet28F.

As noted above, in some applications, this larger axially forward (F) airflow may help protect at least a part of the outer liner12A that defines the primary zone18P which may be hotter than the dilution zone18D. In summary, whether or not an unequal airflow arrangement is implemented, the front-facing and the rear-facing elongate air outlets28F,28R may provide respective air films (F1) (F2), labeled inFIG. 1B, flowing over and thereby heat shielding respective portions of the outer liner12A that are axially forward (F) and axially rearward (R) of the air film starter28.

As shown inFIG. 2A, in this embodiment the air film starter28further includes end walls28W at the opposed circumferential ends of the louver30. The end walls28W close off the circumferential ends of the front-facing and the rear-facing elongate air outlets28F,28R and thereby help direct airflows out of these outlets28F,28R in the respective forward and rearward axial directions (i.e. relative to the central axis10X of the combustor10). It is contemplated that in some embodiments, one or both of the end walls28W of the air film starter28may be omitted. For example, in some such embodiments, one or more end walls28W air film starters28that are adjacent to a given air film starter28may provide for the function of the end walls28W of the given air film starter28.

As best shown inFIGS. 2A and 2B, in this embodiment, the air film starter28in this embodiment is threadingly connected to the outer liner12A. In this embodiment, the threaded connection is provided by three equally spaced threaded studs32distributed along and connected to the divider wall34. In the present embodiment, the threaded studs32are received through corresponding apertures12S in the outer liner12A and extend out of the combustion chamber16through the outer liner12A. The threaded studs32secure the air film starter28in place using washers32A and nuts32B threaded over the studs32and tightened against an outer surface of the outer liner12A.

It is contemplated that any suitable number and spacing of threaded studs32, and any suitable corresponding number of apertures12S in the outer liner12A, may be used for each given air film starter28, to suit the particular embodiment of that air film starter28. While the threaded connection of the present embodiment helps reduce effort required in assembling the combustor10in at least some embodiments of the combustor10, in other embodiments, a different threaded connection, or a different type of connection, to the outer liner12A may be used.

For example, in other embodiments, one or more of the threaded studs32may be attached to a different part of the air film starter28to provide for the functionality described herein. For example, referring toFIG. 3which shows an air film starter38that is a different embodiment of the air film starter28, one or more of the threaded studs32may instead be a threaded bolt44extending to and/or into the louver30for example. In the particular example shown inFIG. 3, the bolt44extends into a boss40defined on the radially outward surface of the louver30, and more particularly into a threaded aperture40defined in the boss40and the louver30.

In the embodiment ofFIG. 3, the bolt44is tightened in the aperture40, with the head44H of the bolt44compressing one or more washers32A (which may be omitted in some embodiments) against the outer surface of the outer liner12A and compressing the outer liner against at least a part of the divider wall34(not visible inFIG. 3). In embodiments in which a part or all of the divider wall34is omitted, the boss40or other support structure may extend for example from the louver30to the outer liner12A to provide a surface against which the bolt44may compress the outer liner12A to define the spacing between the louver30and the outer liner12A. Another difference between the air film starter38and the air film starter28is in the number and size of the air passages in the circumferential portion26of the outer liner12A, as shown with reference numerals20A′ and20B′.

The air passages20A′ are spaced from the front-facing axial edge28E′ of the louver30by an offset that may help the louver30redirect airflow from the air passages20A′ to form the forwardly moving air film (F). Similarly, air passages20B′ are spaced from the rear-facing axial edge28E″ of the louver30by an offset that may help the louver30redirect airflow from the air passages20B′ to form the rearwardly moving air film (R). In some embodiments, the air passages20A′,20B′ are defined as close to a circumferential centerline (which in this embodiment is a symmetry line defined through the axial centers of the bolts44) as permitted given by each embodiment of the air film starter38to make each of the edge offsets a maximum offset. In an aspect, in some embodiments this may help improve at least some characteristics of the respective forwardly and rearwardly moving air films (F), (R) created by the air film starter38. In some cases, and depending on the particular application for example, a similar spacing of the respective air passages20may be applied to other embodiments of film starters described herein.

Referring back toFIGS. 2A to 2C, in the present embodiment the air film starter28further includes thumbnail air outlets36that are disposed on a side of the louver30that is opposite the divider wall34and faces toward the inner liner12B. As shown schematically with airflow arrows inFIGS. 2A to 2C, each of the thumbnail air outlets36is fluidly connected to at least one of the air passages20A,20B via one or more corresponding air passages30A that are defined through the air film starter28. To maintain clarity of the figures, only three of the air passages30A appearing inFIG. 2Bhave been labeled.

As a non-limiting example, the thumbnail air outlet36shown inFIG. 2Bfluidly connects to both the air passages20A and the air passages20B via at least two air passages defined through the louver30, with at least one of these air passages being on each side of the divider wall34. Also as shown, in this embodiment, the thumbnail air outlet36also receives a supply of air from an air source disposed outside of the liner12through one or more apertures/passages defined through a corresponding one of the threaded studs32.

In some embodiments, one or more of the thumbnail air outlets36are supplied with air directly from an air source disposed outside of the liner12, such as solely via one or more air passages in one or more of the studs32for example, and are not directly fluidly connected to any of the passages20A or20B. As an example, in some such embodiments, the air passage(s)30A defined through the stud(s)32as shown inFIG. 2bmay be present, while the other air passages30A shown in the louver30may be absent. In an aspect, such arrangements may help improve impingement and other airflow characteristics of airflow provided by the thumbnail air outlets36by taking advantage of a pressure difference that may be available across the liner12, which may be higher than a pressure difference available across the louver30. It is contemplated that in some embodiments and applications, the thumbnail air outlets36may be supplied with air using any other suitable number and/or arrangement of air passages.

As shown with airflow arrows inFIG. 2A, the thumbnail air outlets36supply air into the combustion chamber16in the circumferential direction (XC) along the inward surface of the louver30. The thumbnail air outlets36thereby create an air film over an entirety of the louver30, and hence over an entirety of the circumferential portion26of the outer liner12A, and thereby help heat shield the air film starters28and the circumferential portion26from the impinging flow16GD of the combustion gases. It is contemplated that any suitable number and/or arrangement and/or shape of the thumbnail air outlets36may be used to provide for this functionality, for example to suit each particular embodiment of the combustor10. It is contemplated that in some applications, the impinging flow16GD and/or the thumbnail air outlets36may be omitted.

Now referring toFIGS. 4A to 4C, an air film starter48, which is yet another different embodiment of the air film starter28, is shown. The air film starter48is similar to the air film starter28, and therefore parts of the air film starter48that correspond to parts of the air film starter28have been labeled with the same reference numerals and will not be described again in detail.

A difference between the air film starter48and the air film starter28is that in the air film starter48, the divider wall34is omitted. Accordingly, the front-facing and the rear-facing elongate air outlets28F,28R are directly fluidly connected to each other, and thus airflow from the air passages50F,50R in the circumferential portion26of the outer liner12A may flow to either of the front-facing and the rear-facing elongate air outlets28F,28R. In this particular embodiment and although need not be the case in other embodiments, the air passages50F,50R are defined through the outer liner12A at non-orthogonal angles, in directions that are tilted toward the respective ones of the front-facing and the rear-facing elongate air outlets28F,28R. In an aspect, this respective tilting may help direct a majority of air flowing from the air passages50F to the front-facing elongate air outlet28F and a majority of air flowing from the air passages50R to the rear-facing elongate air outlet28R.

Another difference between the air film starter48and the air film starter28is that the air film starter48includes an abutment52(shown inFIG. 4B) attached to each of the threaded studs32, against which the nuts32B may compress the outer liner12A for fixing the air film starter48in place.

In some embodiments, one or more of the air film starters28and/or38and/or48of the combustor10may be coated with a Platinum-Aluminide coating, which has been found to help increase durability of the air film starters28and/or38and/or48and hence of the circumferential portion26of an outer liner12A while not materially affecting a complexity of the manufacturing of the combustor10. Also, in some embodiments, one or more of the air film starters28and/or38and/or48of the combustor10may be one of: cast, made as a single crystal, and metal injection molded, from a B1900Hf alloy. Such construction may help mitigate oxidation and may help reduce thermal gradient that may occur across at least some parts of the air film starters28and/or38and/or48during various modes of operation of the combustor10.

Now referring toFIG. 5, with the above non-limiting embodiments of the combustor10and the air film starter28,38,48in mind, the present technology also provides a method60of creating an air film, such as the air film (F1) shown inFIG. 1B, in a combustion chamber16of a combustor10of an aircraft engine1A. In some embodiments, the method60includes, during operation of the combustor10, supplying air (A) into a primary zone18P of the combustion chamber16to generate a toroidal flow16G of combustion gases16G in the primary zone18P, such that the toroidal flow16G of combustion gases16G impinges, as shown with arrow16GD, upon a circumferential portion26of an outer liner12A that defines the combustion chamber16.

In some such embodiments, the method60may also include supplying air (A) into the combustion chamber16along the outer liner12A from front-facing elongate air outlets, such as front-facing elongate air outlets28F and/or48F for example, which may span the circumferential portion26of the outer liner12A as described herein above. In some embodiments, the method60may also include supplying air (A) into the combustion chamber16along the outer liner12A from rear-facing elongate air outlets, such as rear-facing elongate air outlets28R and/or48R, which may span the circumferential portion26of the outer liner12A as described herein above.

Yet further in some embodiments, the method60may also include supplying air (A) into the combustion chamber16in a circumferential direction (XC) along the circumferential portion26of the outer liner12A from outlets, such as thumbnail air outlets36, positioned radially inward (i.e. in a radial direction (XR)) of the front-facing and/or the rear-facing elongate air outlets28F,48F,28R,48F, relative to a central axis10X of the combustor10. As an example, this step of the method60may be performed by, for example, supplying air (A) from all of the thumbnail air outlets36of the combustor10along all of the louvers30in the circumferential direction (XC), and thereby creating an air film (F3) heat shielding at least substantially an entirety of the circumferential portion26of the outer liner12A and all of the air film starters28and/or38and/or48that may cover the 360 degrees of the circumferential portion26.

In a further aspect, and now referring toFIG. 6, the present technology also provides a method70of manufacturing a combustor10of an aircraft engine1A. In some embodiments, the method includes forming an outer liner12A and an inner liner12B to define a combustion chamber16of the combustor10, and fluidly connecting a fuel nozzle14to a front portion16F of the combustion chamber16for injecting fuel (FF) into a primary zone18P of the combustion chamber10.

In some such embodiments, the method70also includes forming air passages20through the outer liner12A and the inner liner12B around the primary zone18P to provide an air supply pattern into the primary zone18P during operation of the combustor10, which air supply pattern creates a toroidal flow of combustion gases in the primary zone18P during operation of the combustor10, the toroidal flow impinging upon a circumferential portion16of the outer liner12A downstream of the fuel nozzle14. One non-limiting example of such an air supply pattern is shown with arrows (A) inFIG. 1B, only some of which are labeled to maintain clarity. One non-limiting example of such a toroidal flow of combustion gases is shown with arrows inFIG. 1B, two of which are labeled16G and16GD.

In some such embodiments, the method70may further include forming an air passage, such as one of the air passages20A,20B,20A′,20B′ for example, through the outer liner12A in the circumferential portion16of the outer liner12A, and attaching a louver30via a fastener32to the outer liner12A at a location opposite the air passage(s)20A,20B,20A′,20B′, inside the combustion chamber16, such that an axial edge, such as the axial edge28E′ and/or the axial edge28E″, of the louver30is spaced from the outer liner12A to define an elongate air outlet28F and/or28R between the axial edge28E′,28E″ and the outer liner12A.

In some such embodiments, the axial edge28E′,28E″ is one of two opposed axial edges28E′,28E″ of the louver30, and the attaching the louver30via the fastener32spaces both of the opposed axial edges28E′,28E″ from the outer liner12A to define opposed elongate air outlets28F and28R, in which cases the elongate air outlet28F or28R referred to above may be one of the opposed elongate air outlets28F and28R.

In some such embodiments, and as shown inFIGS. 2B and 2Cfor example, the method70may further include attaching the fastener(s)32to a side of the louver30facing the outer liner12at a location, such as the central location shown, between the opposed axial edges28E′,28E″ and/or between the opposed circumferential edges of the louver30.

The various embodiments of the engine1A and the combustor10described above may be made using conventional engineering principles and manufacturing techniques.

The above description is meant to be exemplary only. One skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the technology disclosed herein. For example, while in the above embodiments the film starters28,38,48each have one elongate air outlet28F,28R on each of their front-facing and rear-facing sides, in other embodiments this need not be the case. As another example, in some embodiments, one or more of the film starters28,38,48may define one or more elongate air outlet(s) on each of the front-facing and rear-facing sides, and/or may define elongate air outlet(s) on only one but not both of the front-facing and rear-facing sides.

Still other modifications which fall within the scope of the present technology will be apparent to those skilled in the art, in light of a review of this disclosure.