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EP-4502346-B1 - BLADE CONTAINMENT ASSEMBLY FOR A GAS TURBINE ENGINE

EP4502346B1EP 4502346 B1EP4502346 B1EP 4502346B1EP-4502346-B1

Inventors

  • LEFEBVRE, GUY
  • DOYON, FRANCOIS

Dates

Publication Date
20260513
Application Date
20211018

Claims (5)

  1. An exhaust case assembly for a gas turbine engine (10) having a turbine rotor (14a) mounted for rotation about an engine axis, the turbine rotor (14a) having a set of turbine blades (14c), the exhaust case assembly comprising: a flange ring (15a) having a monolithic body including an outer annular wall (15a') and an inner containment ring (15a"') spaced-radially inwardly from the outer annular wall (15a'), the outer annular wall (15a') having a flange (15a") for connection to an associated flange (24a) of an adjacent turbine case (24) surrounding the set of turbine blades (14c); and a sheet metal outer case (15b) extending axially from the outer annular wall of the flange ring (15a), the sheet metal outer case (15b) welded to the outer wall of the flange ring (15a) at a weld joint (15c) disposed in a blade containment zone (22) axially spanning the set of turbine blades (14c), the inner containment ring (15a‴) extending axially from a first location on a first side of the weld joint (15c) to a second location on a second opposite side of the weld joint (15c), characterised in that : the inner containment ring (15a‴) has a radial wall thickness greater than that of the outer wall (15a') at the weld joint (15c).
  2. The exhaust case assembly according to claim 1, wherein the flange (15a") is axially aligned with the set of turbine blades (14c).
  3. The exhaust case assembly according to claim 1 or 2, wherein the inner containment ring (15a‴) is machined into the monolithic body with an annular gap (G) between the outer annular wall (15a') and the inner containment ring (15a"').
  4. The exhaust case assembly according to any preceding claim, wherein exhaust port stiffeners (26) are welded to the sheet metal outer case (15b) at a location axially spaced-apart from the weld joint (15C) outside of the blade containment zone (22).
  5. The exhaust case assembly according to any preceding claim, wherein the weld joint (15c) is a butt joint and is disposed axially downstream of the set of turbine blades (14c) relative to a gas flow through the set of turbine blades (14c).

Description

TECHNICAL FIELD The application relates generally to gas turbine engines and, more particularly, to a blade containment assembly. BACKGROUND OF THE ART In a gas turbine engine, the portion of the engine case surrounding bladed rotors, such as turbine discs, need to be reinforced to preserve the integrity of the case in a blade off event. Features susceptible to weaken the engine case are, thus, typically avoided in the blade containment zone of the case. For instance, weld joints between casing members are typically disposed outside of the blade containment zone. However, in some applications, this may not always be practical. EP 2,149,680 A2 discloses a gas turbine engine. US 4,598,449 A discloses a beam for a containment structure. US 4,490,092 A discloses a containment structure. US 2008/086881 A1 discloses an annular gas turbine engine case and a method of manufacturing. SUMMARY According to an aspect of the present invention, there is provided an exhaust case assembly for a gas turbine engine in accordance with claim 1. Features of embodiments are recited in the dependent claims. DESCRIPTION OF THE DRAWINGS Reference is now made to the accompanying figures in which: Fig. 1 is a schematic longitudinal/axial cross-section view of an exemplary gas turbine engine; andFig. 2 is an enlarged schematic longitudinal/axial cross-section of a last stage of turbine blades surrounded by a blade containment assembly including a weld joint in a blade containment zone. DETAILED DESCRIPTION Fig. 1 illustrates a gas turbine engine 10 of a type preferably provided for use in subsonic flight, generally comprising in serial flow communication an air inlet 11, a compressor 12 for pressurizing the air from the air inlet 11, a combustor 13 in which the compressed air is mixed with fuel and ignited for generating an annular stream of hot combustion gases, a turbine 14 for extracting energy from the combustion gases, and an exhaust 15 through which the combustion gases exit the engine 10. The turbine 14 includes a low pressure or power turbine 14a drivingly connected to an input end of a reduction gearbox RGB 16. The RGB 16 has an output end drivingly connected to an output shaft 18 configured to drive a rotatable load (not shown). The rotatable load can, for instance, take the form of a propeller or a rotor, such as a helicopter main rotor. The gas turbine engine 10 has an engine centerline 17. According to the illustrated embodiment, the compressor and the turbine rotors are mounted in-line for rotation about the engine centerline 17. The gas turbine engine 10 has an axially extending central core which defines an annular gaspath 20 through which gases flow, as depicted by flow arrows in Fig. 1. The exemplary embodiment shown in Fig. 1 is a "reverse-flow" engine because gases flow through the gaspath 20 from the air inlet 11 at a rear portion thereof, to the exhaust 15 at a front portion thereof. According to one aspect, the engine 10 can have an engine architecture corresponding to that of the engine described in applicant's US Patent No. 10,393,027 issued on August 27, 2019. However, it is understood that the engine could adopt different configurations, including a through flow configuration, the engine configuration illustrated in Fig. 1 being provided for context purposes only. FIG. 2 is a schematic enlarged view of the region of the engine encircled in Fig. 1. More particularly, Fig. 2 is a partial view of the turbine 14 and the exhaust 15. As will be seen herein below, Fig. 2 illustrates an example of a case assembly configured to allow for the provision of a weld joint in a blade containment zone. In gas turbine engines, the portion of the engine case surrounding bladed rotors, such as turbine rotors, is reinforced to contain blade fragments or blades and preserve the structural integrity of the case in the event of a blade ejection event. It is not recommended to have welds or other features that could potentially weaken the case (e.g. a hole) in the vicinity of the rotor blades, unless a separate containment ring protects the welds or the weakened region. However, in some engine regions, like the region between the turbine 14 and the exhaust 15, the space available is limited and, thus, the addition of a separate containment ring may not always be possible. Accordingly, the practice has been heretofore to thicken the case around the turbine blades and to move any weld joint axially away from the containment zone. However, it may not always be possible or desirable to do so. In one aspect, the present disclosure provides a means of adding a containment ring without the need to move the weld or another weakened feature (e.g. a hole) and to add a separate containment part. In the particular example shown in Fig. 2, the case assembly includes a blade containment zone 22 for use in blade containment in the event of a blade release event. The blade containment zone 22 as used herein is defined as a zone extending both axia