Compressor Casing Treatment with Segmented Composite Inserts
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Solution Overview
Problem
Gas turbine engine compressors face challenges in maintaining a sufficient surge margin due to boundary layer airflow issues, leading to compressor stall or surge, which existing casing treatments struggle to effectively address, especially with unshrouded blades where clearance variations affect efficiency and risk tip rubs.
Innovation Solution
A compressor casing treatment featuring annular, circumferentially extending channels in a fibre reinforced composite material insert around the blade tips, allowing for boundary layer circulation and easy replacement, helps in managing airflow and preventing stall conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a casing treatment with channels is applied to the compressor casing wall, then the surge margin is improved and boundary layer circulation is enabled, but the device complexity increases due to the need for inserts and channel structures
Solution Approach 1:
The casing treatment is divided into multiple annular channels distributed around the compressor casing wall, with each channel independently forming a circulation path. This segmentation allows the boundary layer to be managed in multiple discrete locations, improving overall surge margin while keeping individual channel structures relatively simple
Solution Approach 2:
The insert containing the channels is formed from composite materials that combine structural integrity with aerodynamic performance. The composite construction allows complex channel geometries to be integrated into a single insert component, reducing assembly complexity while maintaining the surge margin improvement
2Ease of repair
If the insert is made of fibre reinforced composite material, then ease of replacement is improved and manufacturing flexibility increases, but the strength and durability may be reduced compared to traditional metal casings
Solution Approach 1:
The casing treatment is implemented as a separate insert component that can be independently manufactured from composite materials and replaced without affecting the main casing structure. This segmentation allows the insert to be optimized for ease of replacement while the main casing retains its structural strength
Solution Approach 2:
The insert is constructed from fibre reinforced composite materials that provide sufficient strength for the application while enabling easier manufacturing and replacement. The composite materials offer design flexibility and corrosion resistance, balancing strength requirements with maintenance considerations
3Reliability
If annular channels are provided in the compressor casing wall, then boundary layer circulation is enabled and stall conditions are prevented, but the manufacturing precision requirements increase due to the need for precise channel positioning and dimensions
Solution Approach 1:
The channels are positioned as discrete annular features rather than continuous structures, allowing for modular manufacturing and assembly. Each channel can be independently positioned and sized, reducing the overall precision requirements compared to a continuous casing treatment
Solution Approach 2:
The channels are pre-formed in the insert component during manufacturing, with precise positioning established before installation. This preliminary action allows for quality control during fabrication rather than during assembly, reducing the precision requirements for final installation while ensuring proper channel positioning
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the surge margin and efficiency of the compressor by delaying airflow stall and allowing for optimal tip clearance management, reducing the risk of tip rubs and improving overall engine performance.
Implementation Method 1
provision of means that allows boundary layer circulation in circumferential or axial directions or both. Such means essentially comprises a flow path let into the casing wall with open access to the boundary layer on the compressor stage wall
Data Source
AI summary
A compressor or fan casing is provided with a casing treatment to improve the surge margin of an unshrouded rotor stage. The casing treatment takes the form of an insert (20) let into the casing wall (10) to provide a plurality of re-circulation grooves (22) in the wall circumscribing the path of the rotor blade tips. The insert consists of a plurality of arcuate insert segments (20) made of a carbon fiber reinforced resin. In the preferred construction each arcuate segment (20) is formed with axially extending tangs (28,29) on either side that are received into the correspondingly shaped sides (38,40) of a receiving channel (16) in the casing wall (10). The casing (10) may be split on a diametric plane, thus exposing groove ends (38,40), into which the tangs (28,29) carried by the inserts (20) can be slid before the casing (10) is finally assembled.