Patent Description:
During operation of gas turbine engines, parts of the engine are exposed to the hot combustion gases. During transient events, such as when the gas turbine engine is started, the temperature of these parts may rapidly increase from a relative cold temperature to the hot temperature of the combustion gases.

The rapid increase in temperature of the parts exposed to the hot combustion gases may cause them to undergo thermal expansion. If these parts are mounted to other components which do not experience such a rapid increase in temperature, a thermal mismatch may result and may lead to thermally-induced stresses.

<CIT> discloses a modular industrial gas turbine exhaust system.

<CIT> discloses improvements in gas turbine engines.

According to an aspect of the present invention there is a turbine casing assembly in accordance with claim <NUM>.

According to another aspect of the present invention there is a method of assembling a turbine casing of a gas turbine engine in accordance with claim <NUM>.

<FIG> illustrates a gas turbine engine <NUM> of a type preferably provided for use in subsonic flight, generally comprising in serial flow communication a compressor section <NUM> for pressurizing the air, a combustor <NUM> in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, and a turbine section <NUM> for extracting energy from the combustion gases. Some of the rotatable components of the gas turbine engine <NUM> rotate about a longitudinal center axis <NUM> of the gas turbine engine.

The gas turbine engine <NUM> has a "cold" section 12A and a "hot" section 12B. The cold section 12A includes those components of the gas turbine engine <NUM> which are upstream (relative to the direction gases flow through the gas turbine engine <NUM>) of the combustor <NUM> and have thus not been exposed to the hot combustion gases. The hot section 12B includes the combustor <NUM> and those components of the gas turbine engine <NUM> which are downstream of the combustor <NUM>. The components of the hot section 12B are thus exposed to the hot combustion gases generated in the combustor <NUM>. The gases GC flowing through the cold section 12A have a lower temperature than the gases GH flowing through the hot section 12B.

Referring to <FIG>, the hot section 12B includes the combustor <NUM>, the turbine section <NUM> and a case downstream of the turbine section <NUM> for conveying the exhaust gases. The turbine section <NUM> includes one or more rotors 18A each having rotor blades 18B which rotate about the center axis <NUM> and extract energy from the combustion gases. The rotors 18A and rotor blades 18B of the turbine section are typically referred to as turbines and turbine blades, respectively. The hot section 12B includes stationary bodies which enclose other components of the hot section 12B and define the gas path for the hot combustion gases. These stationary bodies are sometimes referred to as casings or cases which collectively define radially-outer boundaries of the gas turbine engine.

Referring to <FIG>, the casing of the gas turbine engine <NUM> includes a turbine casing assembly <NUM> which is part of the hot section 12B. The turbine casing assembly <NUM> is a group of casing components that form part of the turbine section <NUM> and enclose the combustion gases. The turbine casing assembly <NUM> may be provided as disassembled cases which may then be assembled in a suitable facility. The turbine casing assembly <NUM> includes a first case <NUM> and a second case <NUM>. In the embodiment of <FIG>, the first case <NUM> is a turbine support case (TSC) and is thus sometimes referred to herein as "turbine support case <NUM>" or "TSC <NUM>". In the embodiment of <FIG>, the second case <NUM> is an exhaust case <NUM> for conveying the hot exhaust gases, and is mounted to the TSC <NUM>. It will be appreciated that the first and second cases <NUM>, <NUM> may be other cases of the hot section 12B. For example, in one possible alternate configuration, the first case <NUM> houses the combustor <NUM> and part of the components of the cold section 12A, and the second case <NUM> houses the rotors 18A and stators of the turbine section <NUM>.

Referring to <FIG>, the TSC <NUM> forms part of the casing for the gas turbine engine <NUM>. The TSC <NUM> houses stationary and rotatable components of the turbine section <NUM> such as the rotor blades 18B, disks, or stator vanes of the turbine section <NUM>, and defines part of the gas path for the hot combustion gases through the turbine section <NUM>. The TSC <NUM> has a TSC body <NUM> which provides structure to the TSC <NUM> and forms the corpus thereof. In <FIG>, the TSC body <NUM> is cylindrical about the center axis <NUM>. In <FIG>, the TSC body <NUM> defines part of an annular gas path for the hot combustion gases through the turbine section <NUM>. Referring to <FIG>, the TSC body <NUM> includes an inner wall 22A disposed radially inwardly (i.e. closer to the center axis <NUM>) of an outer wall 22B. A radial thickness of the TSC body <NUM> is defined between the inner and outer walls 22A, 22B.

Referring to <FIG>, the TSC body <NUM> has one or more TSC flanges <NUM>. The TSC flange <NUM> is a radially-protruding body that is configured for mating with, and being secured to, corresponding structure of the exhaust case <NUM> in order to assemble the TSC <NUM> and the exhaust case <NUM>. In <FIG>, the TSC flange <NUM> extends radially outwardly from a radially-outermost outer surface of the TSC body <NUM>. In <FIG>, the TSC flange <NUM> extends radially outwardly from the outer wall 22B of the TSC body <NUM>. In <FIG>, a radially-outermost surface of the TSC flange <NUM> is substantially parallel to the center axis <NUM> and defines an outer diameter of the TSC flange <NUM>. In <FIG>, a radially-outermost surface of the TSC flange <NUM> is substantially parallel to the center axis <NUM> and defines an outer diameter of the TSC body <NUM>.

Referring to <FIG>, a portion <NUM> of the TSC body <NUM> adjacent to the TSC flange <NUM> is resiliently deformable. Referring to <FIG>, the portion <NUM> is immediately adjacent to the TSC flange <NUM>. The portion <NUM> is immediately upstream of the TSC flange <NUM>. The portion <NUM> has an axial extent, and extends in a direction being substantially parallel to the center axis <NUM>. Referring to <FIG>, the portion <NUM> extends axially between an upstream extremity 23A and a downstream extremity 23B that is integral with the TSC flange <NUM>. The portion <NUM> extends axially upstream from the TSC flange <NUM>. The portion <NUM> is a cylindrical body which forms only a segment of the axial extent of the TSC body <NUM>.

By "resiliently deformable", it is understood that the portion <NUM> displaces by deforming temporarily and returns to its original shape in response to a radial displacement of parts of the exhaust case <NUM> due to thermal expansion, as described in greater detail below. The temporary deformation of the portion <NUM> is caused by the displacement of TSC flange <NUM> resulting from the thermal expansion of the exhaust case <NUM>. The portion <NUM> returns to its default shape and position when thermal expansion has ceased. The portion <NUM> thus acts like a hinge to accommodate temporary thermal expansion of the exhaust case <NUM>. The resilient deformability of the portion <NUM> may result from its material composition, from the technique used to manufacture the portion <NUM>, from its dimensional arrangement, and/or from any combination of the preceding factors.

Referring to <FIG>, the resilient deformability of the portion <NUM> results at least in part from a difference in the radial thickness of the TSC body <NUM> adjacent to the TSC flange <NUM>. The portion <NUM> has a first radial thickness RT1 defined between the inner and outer walls 22A, 22B of the TSC body <NUM> along the axial extent of the portion <NUM>. The first radial thickness RT1 is constant along the axial extent of the portion <NUM>. A remainder of the TSC body <NUM>, or possibly just a segment of the TSC body <NUM> immediately adjacent to the portion <NUM>, has a second radial thickness RT2 that is greater than the first radial thickness RT1. Thus, in <FIG>, the resilient deformability of the portion <NUM>, and thus of the TSC flange <NUM> connected thereto, is derived at least in part from a thinner cylindrical portion of the TSC body <NUM> acting as a hairpin structure adjacent to the TSC flange <NUM> to improve the flexibility of the TSC flange <NUM> during thermal expansion of mating components. The resilient deformability of the portion <NUM> may also result from the technique used to manufacture the portion <NUM>. For example, the portion <NUM> may be forged metal. Forging a metal involves shaping the metal using localized compressive forces. For example, a hammer, or another tool for applying compressive forces such as a die, may compress the portion <NUM> so that the grains of the metal have the properties and orientation to achieve the functionality described above. In an embodiment, the TSC body <NUM> is a forged metal.

Referring to <FIG>, the exhaust case <NUM> forms part of the casing for the gas turbine engine <NUM>. The exhaust case <NUM> is disposed downstream of the TSC <NUM> and mounted thereto. The exhaust case <NUM> houses stationary components of the hot section 12B such as an exhaust cone <NUM>, and defines part of an annular gas path for the exhaust gases after the combustion gases have been exhausted through the turbine section <NUM>. The exhaust case <NUM> has an exhaust case body <NUM> which provides structure to the exhaust case <NUM> and forms the corpus thereof. In <FIG>, the exhaust case body <NUM> is cylindrical about the center axis <NUM>. Referring to <FIG>, the exhaust case body <NUM> includes an inner wall 32A disposed radially inwardly (i.e. closer to the center axis <NUM>) of an outer wall 32B. A radial thickness of the exhaust case body <NUM> is defined between the inner and outer walls 32A, 32B.

Referring to <FIG>, the exhaust case body <NUM> has one or more exhaust case flanges <NUM>. The exhaust case flange <NUM> is a radially-protruding body that is configured for mating with, and being secured to, the TSC flange <NUM> in order to assemble the TSC <NUM> and the exhaust case <NUM>. In <FIG>, the exhaust case flange <NUM> extends radially outwardly from a radially-outermost outer surface of the exhaust case body <NUM> to a radially-outer wall 34A of the exhaust case flange <NUM>. In <FIG>, the exhaust case flange <NUM> extends radially outwardly from the outer wall 32B of the exhaust case body <NUM>. In <FIG>, the radially-outer wall 34A defines a radially-outermost surface of the exhaust case flange <NUM> and is substantially parallel to the center axis <NUM>. The radially-outer wall 34A defines the outer diameter Ø of the exhaust case flange <NUM>. The radially-outer wall 34A defines the outer diameter Ø of the exhaust case body <NUM>.

Referring to <FIG>, when the TSC and exhaust case flanges <NUM>, <NUM> are mating and secured together such that the TSC <NUM> and the exhaust case <NUM> are assembled together, some or all of the TSC flange <NUM> abuts against the radially-outer wall 34A of the exhaust case flange <NUM>, and against other portions of the exhaust case flange <NUM> as well. The TSC flange <NUM> radially overlaps the exhaust case flange <NUM> at its outer diameter Ø. The TSC and exhaust case flanges <NUM>, <NUM> thus form a flange/joint arrangement that includes an interface along the outer diameter Ø of the exhaust case flange <NUM>. This tight fit at the outer diameter Ø helps to maintain the mating faces of the TSC and exhaust case flanges <NUM>, <NUM> in abutment through the application of compressive forces on the mating faces during thermal expansion of part of the exhaust case <NUM>, as described in greater detail below, through all engine running conditions.

Different configurations for the mating engagement of the TSC flange <NUM> with the radially-outer wall 34A of the exhaust case flange <NUM> are possible. For example, and referring to <FIG>, the TSC flange <NUM> includes a first portion 24A extending radially outwardly from the outer wall 22B of the TSC body <NUM>. The first portion 24A extends along a line being radial to the center axis <NUM>. A radially-overlapping second portion 24B of the TSC flange <NUM> extends axially away from, and downstream of, the first portion 24A. The second portion 24B abuts against the radially-outer wall 34A of the exhaust case flange <NUM>. A radially-innermost wall of the second portion 24B abuts against the radially-outer wall 34A of the exhaust case flange <NUM>. The second portion 24B abuts against the radially-outer wall 34A of the exhaust case flange <NUM> over all of the axial extent of the radially-outer wall 34A. The second portion 24B is disposed radially-outwardly from the radially-outer wall 34A. A downstream surface of the first portion 24A of the TSC flange <NUM> mates with and abuts against an upstream surface of the exhaust case flange <NUM>. Referring to <FIG> and <FIG>, the second portion 24B of the TSC flange <NUM> abuts against the radially-outer wall 34A along all of the circumferential periphery of the radially-outer wall 34A. The TSC flange <NUM> thus radially overlaps the exhaust case flange <NUM> continuously over the entire periphery of the exhaust case flange <NUM>. The radial overlap of the TSC flange <NUM> over the radially-outer wall 34A is <NUM> degrees. Similarly, the first portion 24A of the TSC flange <NUM> abuts against the remainder of the exhaust case flange <NUM> along all of the circumferential periphery of the exhaust case flange <NUM>.

Other configurations for the mating engagement of the TSC flange <NUM> with the radially-outer wall 34A of the exhaust case flange <NUM> are possible. For example, the TSC flange <NUM> may radially overlap the exhaust case flange <NUM> in a non-continuous manner, such as over circumferentially discrete and spaced apart portions of the exhaust case flange <NUM>, for example in circumferential locations where struts <NUM> of the exhaust case <NUM> are positioned. In yet another possible configuration of the engagement of the TSC flange <NUM> with the radially-outer wall 34A, the TSC flange <NUM> includes only one inclined portion extending from the outer wall 22B of the TSC body <NUM> at an angle to a plane being perpendicular to the center axis <NUM>, the inclined portion of the TSC flange <NUM> abutting against only an upstream portion of the radially-outer wall 34A.

Referring to <FIG>, the exhaust case <NUM> has struts <NUM> that reinforce the exhaust case body <NUM>. The struts <NUM> are distributed circumferentially about the center axis <NUM>. The struts <NUM> are circumferentially spaced apart from each other by the same circumferential distance. Each of the struts <NUM> extends along a substantially radial direction. By "substantially radial direction", it is understood that the magnitude of the dimension of each strut <NUM> defined along a line radial to the center axis <NUM> is greater than the magnitude of the dimension of each strut <NUM> defined along a line that is parallel to the center axis <NUM>. Each strut <NUM> extends radially from an inner end 37A to an outer end 37B disposed radially outwardly of the inner end 37A. The inner end 37A of each strut <NUM> is connected to the exhaust cone <NUM>. In an alternate embodiment, the inner end 37A is mounted to a shaft with a suitable bearing, or to another stationary or rotatable structure adjacent to the center axis <NUM>. The outer end 37B of each strut <NUM> is connected to, or integral with, the exhaust case body <NUM>. The outer end 37B of each strut <NUM> is the radially-outermost extremity of the strut <NUM>. It will be appreciated that the struts <NUM> may be integrally formed with the exhaust case body <NUM> to form a single component exhaust case <NUM>.

Referring to <FIG>, each of the struts <NUM> extends in a substantially axial direction between a leading edge portion 38A and a trailing edge portion 38B. By "substantially axial direction", it is understood that the directional vector of the chord between the leading and trailing edge portions 38A, 38B of each strut <NUM> has a magnitude defined along a line parallel to the center axis <NUM> that is much greater than the magnitude of the directional vector defined along a line that is radial to the center axis <NUM>. The leading edge portion 38A includes the leading edge 38AL of the strut <NUM> as well as the portion of the body of the strut <NUM> immediately adjacent to the leading edge 38AL. Similarly, the trailing edge portion 38B includes the trailing edge 38BT of the strut <NUM> as well as the portion of the body of the strut <NUM> immediately adjacent to the trailing edge 38BT. The leading and trailing edge portions 38A, 38B are defined relative to the direction of flow of exhaust gases across the strut <NUM> and through the exhaust case <NUM>, with the leading edge portion 38A being upstream relative to the flow and encountering the flow before the downstream trailing edge portion 38B. One or more of the struts <NUM> may define an airfoil that is symmetric or asymmetric about the chord defined between the leading and trailing edges 38AL, 38BT.

Referring to <FIG>, the strut <NUM> is hollow and defines an internal cavity 36A. Oil service lines, coolant, probes and any other suitable object may extend through the cavity 36A of the strut <NUM>. Referring to <FIG>, the cavity 36A forms an opening 36AH at the outer wall 32B of the exhaust case body <NUM> through which objects may be inserted into the cavity 36A. The cavity 36A is delimited by an internal cylindrical or annular wall 36B. An axial thickness of the strut <NUM> at the leading edge portion 38A is defined along a line parallel to the center axis <NUM> between the leading edge 38AL and the axially closest portion of the annular wall 36B. An axial thickness of the strut <NUM> at the trailing edge portion 38B is defined along a line parallel to the center axis <NUM> between the trailing edge 38BT and the axially closest portion of the annular wall 36B. In an alternate embodiment, some or all of the strut <NUM> is filled internally if the weight envelope permits.

Referring to <FIG>, the leading edge portion 38A of at least the outer end 37B of each of the struts <NUM> is axially aligned with the exhaust case flange <NUM>. The leading edge portion 38A at the outer end 37B of each of the struts <NUM> has a leading edge axial position AP1 defined relative to the center axis <NUM> that is similar to a flange axial position AP2 of the exhaust case flange <NUM>. The leading edge and flange axial positions AP1,AP2 are measured relative to the center axis <NUM>. The leading edge axial position AP1 may be one of the following: the axial position of the leading edge 38AL at the outer end 37B, the axial position of the internal annular wall 36B at the outer end 37B of the leading edge portion 38A, or the midpoint between the two preceding positions. Similarly, the flange axial position AP2 may be one of the following: the axial position of an upstream surface of the exhaust case flange <NUM>, the axial position of a downstream surface of the exhaust case flange <NUM>, or the midpoint between the two preceding positions. It will be appreciated that the axial thicknesses of the leading edge portion 38A at the outer end 37B and of the exhaust case flange <NUM> are small relative to the overall dimensions of the exhaust case <NUM>. Therefore, the axial positions of the thin leading edge portion 38A and of the thin exhaust case flange <NUM> vary very little over their respective axial extents.

The term "similar" is used herein to convey that the leading edge and flange axial positions AP1,AP2 may be identical, or may differ from each other by a relatively small amount such that at least a portion of the leading edge portion 38A at the outer end 37B of the strut <NUM> is positioned radially inwardly of the exhaust case flange <NUM> along a radial line RL extending from, and perpendicular to, the center axis <NUM> through the exhaust case flange <NUM>. For example, and referring to <FIG>, the axial position of the leading edge portion 38A is not constant, and varies between the inner and outer ends 37A, 37B of each strut <NUM>. In such a configuration, and as shown in <FIG>, at least part of the leading edge portion 38A at the outer end 37B of the strut <NUM> lies along the radial line RL and defines the leading edge axial position A1. Referring to <FIG>, the axial position of the leading edge portion 38A varies between the inner and outer ends 37A, 37B of each strut <NUM>. The axial position of the leading edge portion 38A at the inner end 37A is upstream of the axial position of the leading edge portion 38A at the outer end 37B. It thus follows that part of the leading edge portion 38A of the strut <NUM> may be axially misaligned with the exhaust case flange <NUM>, but the leading edge portion 38A at the outer end 37B of the strut <NUM> is axially aligned with the exhaust case flange <NUM>. In an alternate configuration of the strut <NUM>, the leading edge portion 38A extends along a line radial to the center axis <NUM>, such that all of the leading edge portion 38A is axially aligned with the exhaust case flange <NUM>.

The axial alignment of the outer end 37B of the leading edge portion 38A of the struts <NUM> with the exhaust case flange <NUM>, and with the joint formed by the TSC and exhaust case flanges <NUM>, <NUM>, allows any radial expansion of the strut <NUM> to be transmitted substantially radially outwardly to the exhaust case flange <NUM>, thereby helping to reduce or eliminate any moment on the exhaust case flange <NUM> that may be caused by the radial expansion of the strut <NUM>. The exhaust case <NUM> thus provides a structure where the mating flanges <NUM>, <NUM> are positioned directly radially outwardly of some or all of the leading edge 38AL of the struts <NUM>. The leading edge 38AL of the struts <NUM> is at least partially axially aligned with the point of attachment between the TSC <NUM> and the exhaust case <NUM>.

Referring to <FIG>, when the gas turbine engine <NUM> undergoes a transient event, such as when the gas turbine engine <NUM> goes from being off to started up, the hot gases GH flowing through the exhaust case <NUM> heat up the struts <NUM> very quickly, particularly in compact engine designs. The struts <NUM> are heated more than the TSC <NUM> such that there is a thermal mismatch between the exhaust case <NUM> and the TSC <NUM>. The heated struts <NUM> are caused to thermally expand radially outwardly. The axial alignment of at least the outer end 37B of the leading edge portion 38A helps to direct the expansion of the struts <NUM> radially outwardly to the exhaust case flange <NUM>. Referring to <FIG>, the radially-outward expansion of the struts <NUM> applies a radial force RF against the exhaust case flange <NUM>. Since the radially-outer wall 34A of the exhaust case flange <NUM> is radially overlapped by part of the TSC flange <NUM>, the radial force RF is applied against the second portion 24B of the TSC flange <NUM>. The application of the radial force RF against the second portion 24B causes the first portion 24A of the TSC flange <NUM> and the exhaust case flange <NUM> to be squeezed together under compressive forces CF. Any radial displacement of the attached TSC and exhaust case flanges <NUM>, <NUM> is accommodated by the resiliently deformable portion <NUM> of the TSC body <NUM>, which displaces by deforming temporarily in response to the radial displacement of the attached TSC and exhaust case flanges <NUM>, <NUM>.

The TSC <NUM> and exhaust case <NUM> disclosed herein help to allow the TSC <NUM> near the attached flanges <NUM>, <NUM> to be flexible to accommodate thermal expansion of the struts <NUM>. This allows for transferring most or all of the deformation of the struts <NUM> to the attached or mated TSC <NUM>. The TSC <NUM> is thus designed to be flexible to accommodate the radial expansion of the struts <NUM>. The TSC <NUM> and exhaust case <NUM> disclosed herein help to reduce or eliminate bending or deflection into the exhaust case body <NUM> and thus avoid high tensile stress into the material of the exhaust case <NUM>. This may help to provide a solution to a transient thermal stress issue, which may be more common on gas turbine engines <NUM> which are compact relative to the center axis <NUM>. The TSC <NUM> and exhaust case <NUM> disclosed herein may thus contribute to allowing for the installation of an exhaust duct <NUM> in an extreme high temperature and compact area of the gas turbine engine <NUM>.

The mated TSC <NUM> and exhaust case <NUM> may have additional features which contribute to the functionalities described above. For example, and referring to <FIG>, the exhaust case flange <NUM> is a single continuous body that extends around the entire circumferential periphery of the exhaust case body <NUM>. Similarly, the TSC flange <NUM> is a single continuous body that extends around the entire circumferential periphery of the TSC body <NUM>. The flanges <NUM>, <NUM> are thus circumferentially continuous. In such an embodiment, the continuous exhaust case flange <NUM> includes holes <NUM> being through holes that extend through the axially-spaced apart walls of the exhaust case flange <NUM>. The holes <NUM> are configured to be aligned with corresponding holes in the TSC flange <NUM> (see <FIG>) and to receive therethrough a bolt secured in the holes with a nut, thereby attaching the TSC <NUM> to the exhaust case <NUM>. The holes <NUM> are disposed on the exhaust case flange <NUM> circumferentially about the center axis <NUM>. As explained in greater detail below, most of the holes <NUM>, but not all, are spaced circumferentially from an adjacent hole <NUM> by the same circumferential distance. Referring to <FIG>, the exhaust case flange <NUM> includes portions <NUM> each one of which is circumferentially aligned with one of the struts <NUM>. By "circumferentially aligned", it is understood that the strut <NUM> has the same circumferential position, defined about the center axis <NUM>, as some or all of the corresponding portion <NUM> of the exhaust case flange <NUM>. Referring to <FIG>, each portion <NUM> has a circumferential extent defined between two holes <NUM>. Each portion <NUM> is a segment of the exhaust case flange <NUM> that is continuous. Each portion <NUM> is a segment of the exhaust case flange <NUM> that is free of holes <NUM>. Each portion <NUM> of the exhaust case flange <NUM> is axially aligned with the leading edge portion 38A of the strut <NUM> and is free of holes <NUM>. The circumferential distance between the holes <NUM> is largest over the portions <NUM>, and is equal between the holes <NUM> everywhere else in the exhaust case flange <NUM>. The exhaust case flange <NUM> thus has a structure in which attachment holes <NUM> are omitted in line with each strut <NUM>. This structure helps to reinforce the exhaust case flange <NUM> at the location where the radial force RF from the thermal expansion of the struts <NUM> is directed, thus helping to reduce or eliminate tensile stress.

In an alternate embodiment of the exhaust case flange <NUM> and/or the TSC flange <NUM>, the TSC and exhaust case bodies <NUM>, <NUM> include multiple TSC and exhaust case flanges <NUM>, <NUM>, respectively, where each flange <NUM>, <NUM> is circumferentially spaced apart from an adjacent flange <NUM>, <NUM>. In another possible configuration, the flanges <NUM>, <NUM> are free of pre-formed holes <NUM>, such that the TSC <NUM> and the exhaust case <NUM> are attached together using other mechanical fasteners such as clamps, screws and rivets.

Another feature of the TSC <NUM> which contributes to the functionalities described above is described with reference to <FIG>. The TSC flange <NUM> has a TSC flange radially-outer wall 24C. The TSC flange radially-outer wall 24C is the radially-outer wall of the second portion 24B of the TSC flange <NUM>. The TSC flange radially-outer wall 24C defines an outer diameter of the TSC flange <NUM>. The TSC flange radially-outer wall 24C defines an outer diameter of the TSC <NUM>. The TSC flange radially-outer wall 24C is the radially-outermost wall of the TSC <NUM>. The TSC flange <NUM> includes reinforced portions <NUM>. The reinforced portion <NUM> are parts of the TSC flange <NUM> which are strengthened to better accommodate the radial force RF from the thermal expansion of the struts <NUM>. Each of the reinforced portion <NUM> are circumferentially aligned with one of the struts <NUM>. By "circumferentially aligned", it is understood that the strut <NUM> has the same circumferential position, defined about the center axis <NUM>, as some or all of the corresponding reinforced portion <NUM> of the TSC flange <NUM>. Referring to <FIG>, each reinforced portion <NUM> has a circumferential extent that extends circumferentially on either side of strut <NUM>. The TSC flange <NUM> includes other, non-reinforced portions <NUM>, that are each disposed circumferentially between adjacent reinforced portions <NUM>. A radial thickness of the TSC flange <NUM> is defined along a line being radial and perpendicular to the center axis <NUM> from the outer wall 22B of the TSC body <NUM> to the TSC flange radially-outer wall 24C. The radial thickness FRT1 of the reinforced portions <NUM> is greater than the radial thickness FRT2 of the non-reinforced portions <NUM> (see <FIG>). The TSC flange <NUM> thus has a "thicker" second portion 24B overlapping the exhaust case flange <NUM> at circumferential locations where the struts <NUM> are expected to direct the radial force RF, to help distribute the radial thermal load. The thinner, non-reinforced portions <NUM> of the TSC flange <NUM> may be referred to as "scalloped" portions <NUM> of the TSC flange <NUM>.

Yet another feature of the exhaust case <NUM> which contributes to the functionalities described above is described with reference to <FIG>. The leading edge portion 38A of the strut <NUM> has the greatest axial thickness at the outer end 37B, where the axial thickness at the leading edge portion 38A is defined along a line parallel to the center axis <NUM> between the leading edge 38AL and the portion of the annular wall 36B closest to the leading edge 38AL. The axial thickness AT1 of the leading edge portion 38A is greatest at the outer end 37B of each strut <NUM>. The axial thickness of the leading edge portion 38A is less at locations radially inward from the outer end 37B of each strut <NUM>. The leading edge portion 38A of each strut <NUM> is thus designed with a variable wall thickness directly in line with the radially-outer exhaust case flange <NUM>. The axially thicker radially outer end 37B of the leading edge portion 38A helps to distribute the thermal radial load from the struts <NUM> when they undergo thermal expansion. Furthermore, the axially thicker radially outer end 37B of the leading edge portion 38A may increase the mass of the leading edge portion 38A at the outer end 37B and thus stiffen the leading edge portion 38A at this location to help reduce the radial deformation and expansion experienced by the strut <NUM> at this location. Components which are exposed to high temperatures are typically made thinner to be more flexible to accommodate thermal expansion. However, the leading edge portion 38A at the outer end 37B may be made more massive and stiffer because the necessary flexibility for the mating TSC <NUM> and exhaust case <NUM> is transferred to the TSC <NUM> as explained above. In an embodiment, and referring to <FIG>, the axial thickness AT1 of the leading edge portion 38A at the outer end 37B is greater than an axial thickness AT2 of the exhaust case flange <NUM>. The axial thickness AT1 of the leading edge portion 38A at the outer end 37B may be greater than the combined axial thickness of the TSC and exhaust case flanges <NUM>, <NUM>. Such a thicker structure for the leading edge portion 38A of the strut <NUM> at the outer end 37B may take more time to thermally expand and may thus be better at accommodating the transient heating moment. Referring to <FIG>, the leading edge 38AL of the strut <NUM> is joined to the inner wall 32A of the exhaust case body <NUM> with a fillet radius. Such a gradual increase in the axial thickness of the leading edge portion 38A may provide more mass to dissipate heat.

Yet another feature of the exhaust case <NUM> which contributes to the functionalities described above is described with reference to <FIG>. In an embodiment, the TSC <NUM> is forged or is a forged metal, and the exhaust case <NUM> or portions thereof are casted metal. During casting of the exhaust case <NUM>, liquid metal is provided to a mold that contains a negative impression of the shape of the exhaust case <NUM> or components thereof. The metal is cooled and the exhaust case <NUM> is extracted. This may allow for making the exhaust case flange <NUM> inflexible. This may allow for making the exhaust case flange <NUM> stiff such that it does not bend or expand under anticipated loads caused by the radial expansion of the struts <NUM>. This may prevent the exhaust case flange <NUM> from being displaced into the gas path surrounding the exhaust case body <NUM> during thermal expansion of the struts <NUM>, such that all thermal deformation that is not absorbed by the heavier struts <NUM> is transferred to the TSC <NUM>. The stiffness or inflexibility of the exhaust case flange <NUM> may be a property of the material used for exhaust case flange <NUM>, may be derived from how it is manufactured, or may result from both of these factors.

Referring to <FIG>, there is disclosed herein a method of assembling a turbine casing of the gas turbine engine <NUM>. The method includes abutting the TSC flange <NUM> against the exhaust case flange <NUM> to abut part of the TSC flange <NUM> against the outer diameter surface of the exhaust case flange <NUM>, wherein abutting the flange <NUM> of the TSC <NUM> against the flange <NUM> of the exhaust case <NUM> includes abutting the flange <NUM> of the TSC <NUM> against the flange <NUM> of the exhaust case <NUM> to circumferentially align radially-thicker portions <NUM> of the flange <NUM> of the TSC <NUM> with the struts <NUM> of the exhaust case <NUM>.

This also includes positioning leading edge portions 38A of the struts <NUM> at positions along the center axis <NUM> such that at least a portion of each leading edge portion 38A is positioned radially inwardly of the exhaust case flange <NUM> along a radial line RL extending from, and perpendicular to, the center axis <NUM> through the exhaust case flange <NUM>. The method includes securing the flanges <NUM>, <NUM> together to assemble the TSC <NUM> with the exhaust case <NUM>. The assembled TSC and exhaust case <NUM>, <NUM> are configured to displace together with a resiliently deformable portion <NUM> of the TSC <NUM> adjacent to the TSC flange <NUM>.

Claim 1:
A turbine casing assembly (<NUM>), comprising:
a turbine support case (TSC) (<NUM>) having a TSC body (<NUM>) defined about a center axis (<NUM>) with a TSC flange (<NUM>); and
an exhaust case (<NUM>) having an exhaust case body (<NUM>) defined about the center axis (<NUM>) with an exhaust case flange (<NUM>) extending radially outwardly from the exhaust case body (<NUM>) to a radially-outer wall (34A) defining an outer diameter (QJ) of the exhaust case flange (<NUM>), the exhaust case flange (<NUM>) configured to attach the TSC (<NUM>) to the exhaust case (<NUM>), the exhaust case (<NUM>) having struts (<NUM>) circumferentially spaced apart about the center axis (<NUM>), each of the struts (<NUM>) extending radially from an inner end (37A) to an outer end (37B) attached to the exhaust case body (<NUM>), each of the struts (<NUM>) extending between a leading edge portion (38A) and a trailing edge portion (38B), at least a portion of the leading edge portion (38A) at the outer end (37B) of each of the struts (<NUM>) being positioned radially inwardly of the exhaust case flange (<NUM>) along a radial line (RL) extending from, and perpendicular to, the center axis (<NUM>) through the exhaust case flange (<NUM>),
wherein:
the TSC body (<NUM>) adjacent to the TSC flange (<NUM>) is resiliently deformable such that it can deform temporarily and return to its original shape in response to a radial displacement of parts of the exhaust case (<NUM>) due to thermal expansion; and
the TSC flange (<NUM>) has a TSC flange radially-outer wall (24C), a radial thickness (FRT) of the TSC flange (<NUM>) defined from the TSC body (<NUM>) to the TSC flange radially-outer wall (24C),
characterized in the TSC flange (<NUM>) including reinforced portions (<NUM>) each being circumferentially aligned with one of the struts (<NUM>) upon the TSC (<NUM>) being attached to the exhaust case (<NUM>), the TSC flange (<NUM>) including other portions (<NUM>) each disposed circumferentially between adjacent reinforced portions (<NUM>) of the TSC flange (<NUM>), the radial thickness (FRT1) of the reinforced portions (<NUM>) being greater than the radial thickness (FRT2) of the other portions (<NUM>),
and the exhaust case flange (<NUM>) configured to be secured to the TSC flange (<NUM>) to abut the TSC flange (<NUM>) against the radially-outer wall (34A) of the exhaust case flange (<NUM>).