Combustor dome and heat-shield assembly

A combustor dome and heat-shield assembly comprises a heat-shield having a first opening therethrough. A swirler extends through the first opening and captures the heat-shield. A dome having a second opening therethrough and has an upstream side and a downstream side. The swirler extends through the second opening from the downstream side to the upstream side to capture the heat-shield on the downstream side, and a retaining clip engages the swirler to secure the swirler and the heat-shield on the dome.

TECHNICAL FIELD

Embodiments of the subject matter described herein relate generally to gas turbine (GT) engines and, more particularly, to a combustor dome assembly that includes a swirler assembly that retains a heat-shield in its operative position.

BACKGROUND

Gas turbine (GT) engines, which are commonly deployed on aircraft, derive energy by igniting a mixture of fuel and air within a combustion chamber to drive turbines that power the engine's compressor. The combustor system of one known GT engine includes a combustion chamber having a combustor dome assembly that comprises a heat-shield and an annular housing section having multiple apertures therethrough. A carburetor assembly is disposed through each of the apertures and supplies a mixture of fuel and air to the interior of the combustion chamber for combustion therein. Each of the carburetor assemblies comprises a fuel-injector receiving portion and an air flow modulator, which may be formed as an integral part of the combustor's heat-shield. The fuel-injector receiving portion may take the form of, for example, a bellmouth that receives a hook-shaped fuel injector within its mouth portion. The air flow modulator includes a plurality of circumferential veins that extends from an outer annular surface to an inner annular surface. These veins receive air from one or more compressors and direct it into the interior of the air flow modulator where the air is mixed with injected fuel. The combustible fuel-air mixture is then delivered into the combustion chamber and ignited. Ideally, the air flow modulator receives the compressed air at a uniform pressure along its outer surface to minimize cross-flow and turbulence, though this is not often the case in actual practice.

In the past, the injector bellmouth, the swirler/heat-shield assembly, and the combustor dome were rigidly coupled together using, for example, a welding or brazing process. This rigid type of coupling, however, is not designed to accommodate the spatial displacement that may occur between various parts of the combustion system due to thermal expansion. For example, the combustor dome and the swirler/heat-shield assembly are heated by the combustive gases and may move relative to the fuel injector and fuel injector bellmouth, which remain relatively cool during combustion. To better accommodate the differences in thermal expansion, alternative coupling means have been developed that employ various components (e.g., retaining rings, clips, etc.) to secure and align the swirler/heat-shield assembly with the combustor dome and the bellmouth, while simultaneously permitting limited movement between the bellmouth and the combustor dome and swirler/heat-shield assembly. Though overcoming some of the disadvantages associated with welding and brazing, such “flexible” coupling means employ multiple components and, consequently, are relatively complex and expensive to manufacture and install.

In addition to the above, in one known arrangement, the combustor-dome/heat-shield assembly accounts for a significant percentage of the total combustor weight and manufacturing cost. That is, each combustor dome assembly comprises eight unique parts and three retaining features (i.e. one each for the dome heat-shield, the dome swirler, and the bellmouth that contribute weight and cost to the combustor).

Considering the forgoing, it should be appreciated that it would be desirable to provide a simplified retaining means for use in conjunction with a combustor dome assembly that employs fewer components resulting in a lighter, less expensive combustor dome assembly.

DETAILED DESCRIPTION

FIG. 1is a simplified cross-sectional illustration of a gas turbine engine100comprising a low pressure compressor102, a high pressure compressor104, a combustor106, a high pressure turbine108, a low pressure turbine110, and a nozzle112, which are fixedly coupled together along a longitudinal axis114. During operation of engine100, air is supplied by compressors102and104to an upstream portion of combustor106wherein the air is mixed with fuel supplied by a plurality of fuel injectors (not shown). The fuel-air mixture is ignited within a combustion chamber of combustor106to produce a rapid increase in the temperature, velocity, and volume of the surrounding gas, which then drives turbines108and110before exiting engine100through nozzle112.

FIGS. 2 and 3are isometric and cross-sectional views of a portion of combustor106. Combustor106comprises a combustion chamber housing120having an upstream end122and a downstream end124(shown inFIG. 3). A combustor dome assembly116is disposed proximate upstream end122and comprises an annular dome assembly126through which a plurality of orifices128is provided. Orifices128are angularly dispersed around longitudinal axis114of combustor106(FIG. 1). A carburetor assembly130is disposed through each of orifices128comprising a fuel-injector receiving element or bellmouth132, an air flow modifier134commonly referred to as a swirler, a bellmouth retainer138, a vane cover139, and a swirler retaining ring136, each of which is described in detail below. Carburetor assembly130is configured to facilitate mixing of the air passing through air swirler134with the fuel injected into bellmouth132, and includes a flow passage therethrough for conducting the fuel-air mixture into combustion chamber housing120.

FIG. 4illustrates each of the swirler assembly components in greater detail and positioned within shroud141. Bellmouth132comprises a mouth portion135, a generally tubular throat portion140, and a flange portion142that extends radially outward from a downstream end of throat portion140and has an upstream surface and a downstream surface. A swirler vane cover139has a radial section coupled to an upstream portion of swirler134(e.g., by brazing), and an outboard axial section extending upstream. A radially extending bellmouth retainer138has an outboard end coupled to the outboard axial section of vane cover139(e.g., by welding) forming a radially extending slot therebetween for slidingly positioning flange142, and therefore bellmouth132. A fuel injector (not shown) is matingly received within bellmouth132and introduces fuel into throat140. The injected fuel travels and subsequently mixes with air provided through swirler134.

FIG. 5is an isometric view of swirler134in accordance with an embodiment. As can be seen swirler134is a toroid in shape and includes a plurality of circumferential vanes143that receive compressed air from compressors102and104along an outer radial surface of swirler134. Swirler134also includes a plurality of cooling channels152for cooling heat-shield137and lip151. Vanes143alter the flow characteristics of the compressed air in the well-known manner and direct the air into orifice128(FIG. 3) just downstream of the bellmouth132. Fuel injected into bellmouth132is thus mixed with the air supplied by air flow swirler134proximate orifice128and is subsequently ignited within the housing120.

Referring toFIGS. 6,7and8, swirler134is provided with a depression that may take the form of a circumferential groove144. As will be seen, groove144is configured to receive a portion of retaining ring136(e. g. a split ring), which will capture and secure heat-shield137and annular dome assembly126between retaining clip136(which is secured within groove144) and an annular, radially extending abutment148having flat surface150.

Swirler134is disposed proximate orifice128provided through annular dome assembly126. If desired, swirler134may be coupled to a heat-shield137(as described below) that protects combustor dome assembly116from extreme temperatures during combustion. Heat-shield137may be stamped from, for example, a high-temperature nickel alloy. Swirler134and heat-shield assembly may then be secured in relation to annular dome assembly126and, therefore, combustion chamber housing120, via retaining clip136as described in detail hereinbelow. Furthermore, slots161are provided at the periphery of swirler134that are configured to receive projections170(FIG. 11) on annular dome assembly126to prevent swirler134from rotating as will be described below.

FIGS. 6 and 7are cross-sectional views of a section of swirler134in accordance with an embodiment. Referring toFIG. 6, swirler134is provided with annular groove144in an outer circumferential surface154thereof. In addition, swirler134comprises an outer circumferential abutment148having a radial surface150.FIG. 7illustrates how this configuration is capable of capturing dome assembly126and heat-shield137. That is, an edge174of an opening176through dome assembly126(FIG. 11) is sandwiched between an inner annular region178of retaining clip136and an inner annular edge180of an opening182through heat-shield137. In turn, the inner annular portion178of retaining clip136is constrained within swirler groove144. The inner annular edge180of the opening182through heat-shield137abuttingly engages surface150of radial swirler134. Thus, retaining clip136, dome assembly126, and heat-shield137are sandwiched between groove144and surface150and are captured therebetween. Finally,FIG. 8is a cross-sectional view illustrating the upstream end of the combustor dome assembly configured to secure heat-shield137, dome assembly126, and retaining clip136between groove144and surface150.

FIGS. 9 and 10are isometric views of upstream and downstream sides of a heat-shield segment137having a thermal barrier coating156(e.g. a ceramic; more particularly, 7-8% yttria stabilized zirconia) deposited thereon. The heat-shield segments are also provided with attachment elements for securing the heat-shield to dome assembly126; e.g., projections166that pass through openings168(e.g. slots) in dome assembly126shown inFIG. 11. Projections166also serve as a redundant and independent mechanism for securing the heat shield. In addition, the openings through heat-shield137are provided with inwardly directed projections186which align and are received within swirler slots161(FIG. 5) to prevent rotation thereof.

FIG. 12is a flow chart describing the process190for assembling the combustor dome and heat-shield assembly in accordance with an embodiment. In STEP192, the swirler134assembly comprised of the bellmouth132, the bellmouth retainer138, the vane cover139, and the swirler is assembled. Next, the swirler is inserted through the opening182in the heat-shield137from the downstream side to the upstream side (STEP194). In STEP196, the composite swirler/heat-shield assembly is inserted through the opening176in the dome until stopped by the dome. In STEP198, the split retaining ring136is positioned in groove144and the halves welded together to secure the assembly. Finally, tabs166on heat-shield137that were passed through slots in dome assembly126are bent to secure heat-shield137.

Thus, there has been provided a simplified retaining means for use in conjunction with a combustor dome assembly that employs fewer components resulting in a lighter, less expensive combustor dome assembly.