Patent Application
20220397041
The application relates generally to gas turbine engines and, more particularly, to turbine shrouds.
Turbine shrouds are radially located on a turbine support case (TSC) about the tip of the turbine blades to control blade tip clearance. The turbine shrouds are typically segmented in the circumferential direction to allow for thermal expansion. While various framework have been developed for supporting the shroud segments in position in the turbine case, continued improvements are suitable.
In one aspect, there is provided a turbine shroud segment of a circumferentially segmented turbine shroud configured to be mounted inside a turbine support case for surrounding a circumferential array of turbine blades rotatable about an axis, the turbine shroud segment comprising: a shroud body including: a platform having a radially inner surface facing towards the axis and a radially outer surface facing away from the axis; forward and aft hooks extending from the radially outer surface of the platform and configured for engagement with a shroud support structure on the turbine support case; and a pin receiving hole defined in the shroud body; and an anti-rotation pin engaged in the pin receiving hole, the anti-rotation pin projecting outwardly from the pin receiving hole for engagement with a corresponding anti-rotation abutment on the shroud support structure.
In another aspect, there is provided a turbine section comprising: a turbine support case extending circumferentially around an axis; a circumferential array of turbine blades disposed within the turbine support case for rotation about the axis; and a circumferentially segmented turbine shroud mounted inside the turbine support case about the circumferential array of turbine blades, the circumferentially segmented turbine shroud including a plurality of shroud segments disposed circumferentially one adjacent to another, each shroud segment having a body including: a platform having a radially inner surface facing towards the axis and a radially outer surface facing away from the axis; and forward and aft hooks extending radially outwardly from the radially outer surface of the platform for engagement with a shroud support structure on the turbine support case; wherein one or more of the plurality of shroud segments have a pin receiving hole defined in the body thereof; and wherein an anti-rotation pin has a first end engaged in the pin receiving hole and a second end received in a localisation slot defined in the shroud support structure of the turbine support case.
In a further aspect, there is provided a turbine shroud assembly comprising: a shroud support extending circumferentially around an axis; and a circumferentially segmented turbine shroud supported by the shroud support, the circumferentially segmented turbine shroud including a plurality of shroud segments, each shroud segment having: a platform; a pair of axially spaced-apart hooks projecting radially outwardly from a radially outer surface of the platform, each hook of the pair of axially spaced-apart hooks having a radially extending leg portion and an axially extending rail portion; a pin receiving hole extending through the radially extending leg portion of one of the axially spaced-apart hooks; and a pin removably installed in the pin receiving hole.
Reference is now made to the accompanying figures in which:
The expressions “forward” and “aft” used herein refer to the relative disposition of components of the engine 10, in correspondence to the “forward” and “aft” directions of the engine 10 and aircraft including the engine 10 as defined with respect to the direction of travel. In the embodiment shown, a component of the engine 10 that is “forward” of another component is arranged within the engine 10 such that it is located closer to the output shaft 18. Similarly, a component of the engine 10 that is “aft” of another component is arranged within the engine 10 such that it is further away from the output shaft 18.
The turbine 14 generally comprises one or more stages of circumferentially spaced-apart rotor blades 21 extending radially outwardly from respective rotor disks, with the blade tips being disposed closely adjacent to an annular turbine shroud 22 supported from a turbine shroud support 24 (
Referring concurrently to
According to the illustrated embodiment, the rail portions 40b, 42b of the forward and aft hooks 40, 42 of the shroud segment 22a project axially in an aft direction and the corresponding rail portions 24a, 24b of the shroud hanger axially project in a forward direction. However, it is understood that the axial orientation of the mating pairs of rail portions 24a, 40b and 24b, 42b could be inverted. In addition, the axial orientation of the forward and aft hooks 40, 42 does not need to be the same. Various combination/permutation are contemplated.
Referring jointly to
According to the example illustrated in
According to one or more embodiments, the pin receiving hole 52 is defined in the radially extending leg portion 40a, 42a of one of the hooks 40, 42. In the particular example shown in
As can be appreciated from
According to one or more embodiments, individual shroud segments 22a are cut from a circumferentially continuous shroud ring obtained from a turning manufacturing process on a computer numerical control (CNC) machine. Such a machining process is economical compared to casting or metal injection molding (MIM) processes. Still according to one or more embodiments, the pin receiving holes 52 are machined in the individual shroud segment 22a either prior or after cutting of the segments. Machining the pin receiving hole 52 in the shroud segments 22a instead of in the turbine case 26 contributes to reduce the risk that the turbine case 26, which is a much more expensive part than the shroud segments 22a, be rejected for non-conformance related to this additional machining operation. Indeed, the transfer of a feature (e.g. pin receiving hole) that needs precise machining from an expensive part with limited machining access to a less expensive “sacrificial” component (e.g. shroud segment) with easier machining access as several advantages from a manufacturing point of view. Also by mounting the pins 50 of the shroud segments 22a, the pins 50 can be more easily replaced together with the shroud segments when need be. This contributes to minimize the operation on the turbine case 26 at overhaul and, thus, the risk of inadvertently damaging the turbine case 26.
Still according to one or more embodiments, the pins 50 are installed on the shroud segments with a tight fit assembly. This method of assembly allows the pins 50 to be removed from their respective host and replaced by a new pin if need be during maintenance operations. The pins 50 and the body of the shroud segments 22a can be made of a same or different material. For instance, both the pins 50 and the shroud segments 22a could be made of Inconel 625 or from other suitable high temperature resistant materials. While the illustrated embodiment has one pin 50 per shroud segment 22a, it is understood that one or more pins can be installed on each segment or selected ones of the shroud segments.
The shroud segments 22a with the pins 50 pre-assembled thereon are individually installed inside the turbine case 26. First, the pin 50 of a first one of the shroud segments 22a is angularly aligned in a circumferential direction with a corresponding one of the slots 60 in the shroud support 24 and then the first shroud segment 22a is axially loaded into the turbine case 26 so as to axially slide the rail portions 40b, 42b of the forward and aft hooks 40, 42 over the forward and aft rail portions 24a, 24b of the shroud support 24. Once, the first segment has been properly positioned in the turbine case 26 with its pin 50 axially engaged in the associated slot 60, a second segment is installed and the procedure is repeated until all segments have been loaded into position within the turbine case 26.
In accordance with one aspect, there is provided a shroud segment that incorporates a feature for an anti-rotation device that can be removed and replaced as required. A removable anti-rotation device that contributes to reduce the cost of the shroud segment by using a turning operation for manufacturing the shroud segments, thereby eliminating the need for traditionally more costly manufacturing methods, such as casting or metal injection molding. The provision of a separate localisation pin pre-assembled on a shroud segment removed the precision of the anti-rotation feature from the turbine case 26, which is a more expensive part to manufacture.
The embodiments described in this document provide non-limiting examples of possible implementations of the present technology. Upon review of the present disclosure, a person of ordinary skill in the art will recognize that changes may be made to the embodiments described herein without departing from the scope of the present technology. For example, while the technology as been described in the context of a turboprop/turboshaft configurations, it is understood that the described shroud assembly features could be applied to other engine configuration, including turbofan and APU engines to name a few. Yet further modifications could be implemented by a person of ordinary skill in the art in view of the present disclosure, which modifications would be within the scope of the present technology.
