Gas Turbine IP Compressor Shroud Distortion Control
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Solution Overview
Problem
In turbofan engines, the existing shroud mounting arrangement for centrifugal compressors is prone to distortions due to asymmetric structural loading, leading to increased impeller tip clearance and air leakage, which compromises engine performance.
Innovation Solution
A structural loop with comparable axial lengths from the bearing through both rotating and static structures, combined with a forward piston ring seal arrangement and a radial diffuser mounting scheme, minimizes shroud distortion and maintains tight impeller tip clearance by isolating the shroud from structural load paths and thermal growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the shroud is mounted to the compressor casing or diffuser assembly, then the shroud is supported structurally, but carcass distortions from asymmetric structural loading are transmitted to the shroud, resulting in increased impeller tip clearance
Solution Approach 1:
A vibration isolation element is introduced as an intermediary component between the shroud and the diffuser assembly. This element acts as a mediator that blocks the transmission path of structural vibrations and carcass distortions from the compressor casing to the shroud, while still providing necessary structural support. The vibration isolation element absorbs and dampens asymmetric structural loading, preventing it from reaching the shroud and causing clearance variations.
Solution Approach 2:
The invention addresses asymmetric structural loading by introducing a symmetric vibration isolation mechanism that counteracts the asymmetric forces. The isolation element is positioned and designed to provide uniform support around the shroud circumference, creating a symmetric response to asymmetric loads, thereby maintaining consistent impeller tip clearance despite asymmetric operational conditions.
2Reliability
If adequate clearance is designed in the shroud, then interference is avoided during extreme carcass distortions, but distortion increases component clearance, resulting in excess air leakage
Solution Approach 1:
The vibration isolation element provides dynamic adaptation to carcass distortions. Rather than relying on fixed static clearance, the isolation element dynamically adjusts to accommodate asymmetric structural loading and thermal growth, maintaining optimal clearance throughout the range of operational conditions. This dynamic response allows the system to maintain tight clearance during normal operation while preventing interference during extreme distortions.
3Productivity
If the shroud is rigidly mounted to minimize clearance, then compressor performance is optimized, but the shroud becomes susceptible to distortion from structural loading and thermal growth
Solution Approach 1:
The vibration isolation element changes the mechanical parameters of the shroud mounting system. It transforms the rigid mounting into a compliant mounting that maintains positional stability through controlled flexibility. The isolation element's material properties and geometric parameters are selected to provide optimal vibration isolation while maintaining sufficient stiffness to prevent excessive clearance variation, thus preserving compressor performance.
Data Source
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AI summary
A gas turbine engine includes a compressor assembly that is rotationally coupled to a shaft, the compressor assembly having a centrifugal impeller and a shroud covering a bladed portion of the centrifugal impeller. The compressor assembly includes a diffuser that is attached to the shroud via a pair of flanges, the diffuser including a strut that is mounted through an aft-extending leg to a base of an intercase. A sealing assembly is attached to the diffuser and is attachable to a transition duct that is positioned to receive air from the diffuser. The sealing assembly is configured to prevent air from passing through the sealing assembly while allowing relative motion to occur between the transition duct and the diffuser.