Combustor bulkhead heat shield

A heat shield for a combustor includes a ring shaped body including a central opening defining a radially inner edge of the ring shaped body. The ring shaped body is at least partially made of a ceramic material. The heat shield includes a shaped portion designed to enhance an interference fit.

TECHNICAL FIELD

The present disclosure relates generally to a combustor for a gas turbine engine, and more particularly to a combustor bulkhead heat shield.

BACKGROUND OF THE INVENTION

Gas turbine engines are generally known and, when used on an aircraft, typically include a fan delivering air into a bypass duct and a compressor section. Air from the compressor section is passed downstream into a combustion section where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors driving the turbine rotors to rotate.

Some existing gas turbine engines utilize a metallic bulkhead within the combustion section. The metallic bulkhead is either made as a single integral unit, or assembled from multiple bulkhead panels. Existing metallic bulkhead panels are coated on an internal surface with a heat resistant coating to resist the extreme temperatures resulting from combustion. In some examples, oxidation of heat resistant coatings on the bulkhead panels can be extreme and shorten the life of the combustor. In order to combat high temperatures, engines have been designed using alternate materials to create the combustor itself or using a liner made from an alternate material within the combustor and affixed to the combustor via fasteners.

SUMMARY OF THE INVENTION

A gas turbine engine according to an exemplary embodiment of this disclosure, among other possible things includes a compressor section, a combustor in fluid communication with the compressor section, a turbine section in fluid communication with the combustor, the combustor further including a combustor region defined by at least one bulkhead panel, and at least one heat shield panel interior to the combustor region, the at least one heat shield panel is connected to the bulkhead panel via an interference fit.

In a further embodiment of the foregoing gas turbine engine, the heat shield panel includes at least one layer of a ceramic matrix composite (CMC) material and at least one layer of a high heat tolerance machinable temperature material.

In a further embodiment of the foregoing gas turbine engine, the high heat tolerance machinable material includes silicon.

In a further embodiment of the foregoing gas turbine engine, the combustor further includes an outer diameter combustor shell and an inner diameter combustor shell, at least one of the outer diameter combustor shell and the inner diameter combustor shell includes a protrusion into the combustor and an edge of the heat shield panel is axially positioned between the protrusion and the bulkhead relative to an axis defined by the gas turbine engine.

In a further embodiment of the foregoing gas turbine engine, each of the outer diameter combustor shell and the inner diameter combustor shell includes a protrusion into the combustor and an inner diameter edge of the heat shield panel is axially positioned between the protrusion on the inner diameter combustor shell and the bulkhead, and a portion of the heat shield panel is axially positioned between the protrusion on the outer diameter combustor shell and the bulkhead.

In a further embodiment of the foregoing gas turbine engine, the interference fit is an interference fit between the protrusion, the bulkhead and one of the inner diameter edge and the outer diameter edge of the heat shield panel.

In a further embodiment of the foregoing gas turbine engine, the heat shield panel has a primary axial thickness and a secondary axial thickness, where the secondary axial thickness is positioned proximate to at least one of an inner diameter and an outer diameter.

In a further embodiment of the foregoing gas turbine engine, the heat shield panel includes a plurality of axially aligned through holes, and the combustor includes a plurality of swirlers protruding into the axially aligned through holes.

In a further embodiment of the foregoing gas turbine engine, the combustor further includes a plurality of outer liner panels and a plurality of inner liner panels, and at least one panel of the plurality of outer liner panels and the plurality of inner liner panels includes an interference fit protection feature.

In a further embodiment of the foregoing gas turbine engine, the interference fit protection feature includes a portion of a liner closest to the heat shield panel, and the portion is curved toward a center of the combustion region.

A heat shield for a combustor according to an exemplary embodiment of this disclosure, among other possible things includes a ring shaped body including a central opening defining a radially inner edge of the ring shaped body, the ring shaped body includes a ceramic material, a plurality of through holes distributed circumferentially about the ring shaped body, and an interference fit shaped portion on at least one of the radially inner edge and a radially outward edge of the heat shield.

A further embodiment of the foregoing heat shield includes a high heat tolerance machinable material layer applied to all sides of the heat shield.

In a further embodiment of the foregoing heat shield, the high heat tolerance machinable layer includes silicon.

A further embodiment of the foregoing heat shield includes an interference fit shaped portion on both the radially inner edge and a radially outer edge.

In a further embodiment of the foregoing heat shield, the interference fit shaped portion has a larger thickness along an axis defined by the ring shaped body than the thickness of the body along the same axis.

In a further embodiment of the foregoing heat shield, the interference fit shaped portion is a rounded bulb shape and the bulb shape has a diameter larger than a thickness of the body along an axis defined by the ring shaped body.

In a further embodiment of the foregoing heat shield, an edge of the ring shaped body extends into the interference fit shaped portion.

In a further embodiment of the foregoing heat shield, the ring shaped body includes a ceramic matrix composite (CMC) material.

A method for constructing a combustor according to an exemplary embodiment of this disclosure, among other possible things includes the step of maintaining a heat shield adjacent to at least one bulkhead panel using an interference fit.

In a further embodiment of the foregoing method, the interference fit is an interference between an interference feature on at least one of a radially outward edge of the heat shield and an interference feature on a radially inner edge of the heat shield, a bulkhead, and a protrusion feature on a combustor shell.

DETAILED DESCRIPTION OF AN EMBODIMENT

FIG. 2schematically illustrates the combustor section26of the gas turbine engine ofFIG. 1in greater detail. The combustor section26includes a combustion region110in which fuel is combusted. The combustor section26is defined by a combustor bulkhead120, and one or more combustor panels122that are combined to form an annular combustor shape. The combustor shells122are connected to each other using known fastening means. The shells122are full hoop sheet metal shells and are designed to handle a pressure load and other mechanical loads. Lining the combustor bulkhead120, and within the combustion region110, is a ceramic matrix composite (CMC) heat shield130. The CMC heat shield130is maintained in position via an interference fit between the combustor bulkhead120, the heat shield130, and a protrusion feature134located on at least one of the combustor shells122. While the example ofFIG. 2illustrates a protrusion feature positioned on both the inner combustor shell122and the outer combustor shell122it is understood that alternate examples could maintain the interference fit using only one protrusion feature positioned on either the inner diameter combustor shell122or the outer diameter combustor shell122. Further, it is understood that the particular “bump” shape of the protrusion feature134illustrated inFIG. 2is purely exemplary and alternate shaped protrusion features can be used to the same affect.

During operation of the turbine engine20, compressed air from the compressor section24passes around the combustor section26and impinges on an external surface of the combustor bulkhead120. Due to the extreme heat generated within the combustor56, the gas exiting the compressor section24and impinging upon the combustor bulkhead120is cool relative to the temperatures in the combustor56. The combustor bulkhead120includes multiple small cooling holes through which the impinging air can pass. Disposed between the bulkhead120and the heat shield130is a gap132. The impinging air enters the gap132through the holes in the combustor bulkhead120and provides a cooling effect on the heat shield130.

As described above, the illustrated heat shield130is constructed of a ceramic matrix composite (CMC) material, and has a very high heat tolerance. CMC materials, however, are prone to breakage any place where a fault or stress is introduced into the material. By way of example, this type of fault or stress is introduced anywhere that a threaded component is threaded through the heat shield130. Heat shields130constructed of traditional materials, such as nickel alloys, are typically connected to the bulkhead panel via physical fasteners that use a threaded bolt/nut arrangement. As described above, passing the threaded bolt through the CMC material of the heat shield130introduces a fault into the CMC material. This fault is exacerbated by thermal expansion and contraction and can lead to an early breakdown, such as cracking or delamination of the heat shield130, resulting in more frequent repairs.

FIG. 3illustrates a partial cross section of a bulkhead portion of an annular combustor200showing the position of the heat shield130in greater detail. The combustor200is generally formed of a hood210, a bulkhead panel220, an outer combustor shell230, and an inner diameter combustor shell240. The hood210, bulkhead shell220and the outer diameter combustor shell230are joined on an outer diameter edge of the annular combustor200via a fastener216. Similarly, the hood210, the bulkhead shell220and the inner diameter combustor panel240are fastened together on an inner diameter edge via a fastener216. While the illustrated annular combustor200shows a single fastener216on each edge, it is understood that multiple fasteners216can be distributed around the annular combustor, thereby ensuring a solid assembly.

The hood210and the bulkhead panel220define a cavity222. A fuel line212protrudes into the cavity222and provides fuel to a swirler214. The swirler214protrudes through a corresponding hole in the bulkhead panel220and provides fuel into a combustion region202where the fuel is ignited. While only a single fuel line212and swirler214are shown in the illustration ofFIG. 3, it is understood that multiple fuel lines212and swirlers214are disposed circumferentially about the annular combustor200

In order to protect the bulkhead panel220from the heat generated by combustion in the combustor region202, a heat shield panel250is placed adjacent to the bulkhead panel220and includes multiple openings258through which the swirlers214protrude. The heat shield panel250is constructed at least partially of a CMC material and protects the metal bulkhead panel220by absorbing the combustion heat, and thereby minimizing the amount of heat that the bulkhead panel220is exposed to. Similar to the heat shield panel250, metal combustor liners260,270are affixed to the outer diameter combustor shell230and the inner diameter combustor shell240and serve a similar function to the heat shield panel250.

In existing combustor designs, the heat shield panels250are constructed of a metal material and are maintained in position relative to the bulkhead panel220via one or more fasteners that are threaded through the heat shield panel250. As described above, CMC materials, such as those used in the construction of the instant heat shield panel250can be weakened or break when a fastener is threaded through the heat shield panel250. In order to minimize this possibility, the heat shield panel250in the annular combustor200ofFIG. 3is maintained in position via an interference fit.

The interference fit is between the metal bulkhead panel220and an interference feature232,242on the outer diameter combustor shell230or the inner diameter combustor shell240. In the example combustor200ofFIG. 3, the interference features232,242are protrusions into the combustion region202of the combustor200. In alternate examples, the heat shielding panel250can be maintained in position using only a radially inner interference fit or a radial outer interference fit and the interference feature232,234on the opposite edge can be omitted.

As a further component of the interference fit, in some examples the inner diameter liner270and the outer diameter liner260closest to the interference fit include a protection feature262,272. The protection features262,272curve inwards toward a center of the combustion region202and protect at least a portion of the inward protrusions (the interference features232,242) from the heat of the combustion in the combustion region202. As with the interference fit, the protection features262,272can be located on either the inner diameter (protection feature272) or the outer diameter (protection feature262) or both, as in the illustrated example. The protection features262,272can further protect the interference fits and the joints between the combustor panels230,240and the bulkhead panel220by directing airflow away from the interference fit and the joint as a result of the curvature.

To further aid with the interference fit, each end of the heat shield panel250includes a shaped region256,254that is wider than a main body portion255of the heat shield panel250. The shaped region254,256fits between the metal bulkhead panel220and the corresponding interference feature232,242and is shaped to enhance the interference fit. The illustrated shaped region254,256is a bulb shape. It is understood however, that alternate shapes could also be determined and used by one of skill in the art having the benefit of this disclosure. Once assembled, the interference feature232,242pinches the shaped region254,256against the metal bulkhead panel220thereby holding the heat shield panel250in position. In this way, the heat shield panel250can be maintained in position without requiring the utilization of fasteners that can weaken or damage the heat shield panel250.

The shaped regions254,256further facilitate a gap252between the main body portion255of the heat shield panel250. The gap252is a cooling gap252. In practical embodiments, the metal bulkhead220includes multiple small holes disposed about the bulkhead220, and the cavity222is not airtight. As a result, relatively cool air enters the cavity222from the compressor section and passes through the metal bulkhead220. The relatively cool air impinges on the heat shield panel250, providing a cooling effect to the heat shield panel250.

FIG. 4illustrates a fore view of a heat shield panel300, such as the heat shield panel250illustrated in the annular combustor ofFIG. 3. The heat shield panel300includes an outer diameter shaped region310along an outer edge of the ring corresponding to the outer shaped region256of the heat shielding panel illustrated inFIG. 3. Similarly, the heat shield panel300includes an inner diameter shaped region320along the inner edge of the ring corresponding to the inner shaped region254ofFIG. 3, and multiple swirler holes340disposed circumferentially about the heat shield panel300. While the illustrated example includes sixteen swirler holes340distributed evenly about the heat shield panel300, it is understood that an alternate number of swirler holes340could be utilized and that the swirler holes need not be evenly distributed in all examples.

FIG. 5illustrates a partial cross sectional view of a heat shield panel400that can be utilized in the examples ofFIG. 2-4. The heat shield panel400includes a shaped region410on at least one of an inner diameter edge or an outer diameter edge of the heat shield panel400. The shaped region410has an axial thickness412that is defined as the axially thickest portion of the shaped region410. A main body portion420of the heat shield panel400is located between the shaped regions410in heat shields400including a shaped region410on both a radially inner and a radially outer edge. In the illustrated example, the main body region extends into the interior of the shaped region410.

The main body portion420of the heat shield panel400has an axial thickness422. The axial thickness422of the main body portion420is smaller than the axial thickness412of the shaped region410. This enhances the interference fit of the heat shield panel400and provides for the creation of the cooling gap described above.

The heat shield panel400is constructed primarily of two different materials and techniques. The first material utilized is the above described CMC material can be formed in multiple CMC layers440. The CMC layers form the basic heat shield400ring shape, including the swirler holes and excluding the shaped regions410. Once the basic shape of the heat shield400is formed from the heat resistant CMC material, a high heat tolerance machinable material layer430is applied over top of the CMC layers440. In one example, the high heat tolerance machinable layer430is a material comprised at least partially of silicon. A high heat tolerance machinable material is any material that can withstand extremely high temperatures, and can be machined to a desired shape or dimension without loss of the high heat tolerance. The high heat tolerance machinable material layer430is then machined to create a thinner main body portion having a uniform thickness and the shaped region410.

In alternate examples the entire heat shield panel400is formed from the CMC material, and a machinable high heat tolerant coating material is not required. Examples utilizing purely a CMC material are more difficult to produce and can in some cases have a lower expected part lifetime. Alternatively, a pure ceramic (monolith ceramic) material can be used in place of the CMC material.

The bulkhead heat shield described above can be modified by one of skill in the art having the benefit of this disclosure to function in a can style combustor as well as the above described annular combustor. Thus, one alternative to the aboved described system is replacing the annular combustor with a can combustor.

While the examples illustrated herein utilize a bulb shape, or rounded, region for the shaped portion, it is understood that the shaped region410can be shaped in any shape that provides a tight interference fit with the bulkhead panel and the combustor panels.