Gas Turbine Shroud Assembly Load Path Design
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Solution Overview
Problem
Existing gas turbine engine designs face challenges in load transmission between components, particularly with ceramic matrix composite shrouds, leading to undesirable load transmission, thermal gradient-induced axial deflections, and increased purge flow requirements, which reduce engine efficiency and increase cost and weight.
Innovation Solution
The design incorporates a shroud assembly with a hanger and support member that directs loads from nozzles through the hanger to the engine casing, minimizing load transmission through the shroud, using a support member positioned axially forward of the hanger arm to transfer loads with a gap between the support member and the shroud, thereby reducing axial gap variations and associated inefficiencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If an outer support connected to the casing and in contact with the nozzles is used to transmit loads, then load transmission is achieved, but thermal gradients cause axial deflection leading to large nozzle-shroud axial gap variations requiring additional purge flow
Solution Approach 1:
A load transmission element is introduced as an intermediary component between the nozzle and the shroud hanger. This element transmits loads from the nozzle to the hanger without requiring direct contact between the nozzle and shroud assembly, thereby maintaining stable axial gaps and reducing purge flow requirements while achieving effective load transmission.
Solution Approach 2:
The load transmission function is segmented from the shroud assembly itself and assigned to a separate dedicated load transmission element. This segmentation allows the shroud assembly to remain thermally isolated while the load transmission element handles mechanical loads independently, preventing thermal gradient-induced deflections from affecting axial gaps.
2Force
If an outer support connected to the casing and in contact with the nozzles is used to transmit loads, then load transmission is achieved, but the support is heavy and expensive increasing cost and weight
Solution Approach 1:
The load transmission function is extracted from a heavy external support structure and integrated into a compact element that utilizes the existing shroud hanger as part of its structure. This extraction eliminates the need for separate heavy support components while maintaining load transmission capability through a more lightweight integrated design.
3Ease of manufacture
If ceramic matrix composite shrouds are used, then numerous advantages are provided, but they are undesirable for load transmission due to material characteristics
Solution Approach 1:
The load transmission function is extracted from the ceramic matrix composite shroud itself and assigned to a separate load transmission element made of appropriate materials. This allows the CMC shroud to retain its manufacturing advantages while the dedicated load transmission element handles mechanical loads, solving the incompatibility between CMC material characteristics and load transmission requirements.
Solution Approach 2:
The shroud assembly is segmented into distinct functional components: the CMC shroud for its manufacturing advantages and a separate load transmission element for handling mechanical loads. This segmentation allows each component to be optimized for its specific function, with the load transmission element being in communication with the shroud hanger to transmit loads away from the CMC shroud.
Data Source
AI summary
Shroud assemblies for gas turbine engines are provided. A shroud assembly includes a hanger having a forward hanger arm, a rear hanger arm, and a hanger body extending between the forward hanger arm and the rear hanger arm. The shroud assembly further includes a shroud having a forward surface, a rear surface, and an inner surface and outer surface extending between the forward surface and the rear surface, the outer surface radially spaced from the inner surface, the shroud connected to the hanger. The shroud assembly further includes a support member positioned axially forward of the forward hanger arm, the support member having a radially outer portion connected to the forward hanger arm and a radially inner portion axially spaced from the shroud such that a gap is defined between the radially inner portion and an axially adjacent surface of the shroud.