Rotor Cover Plate Asymmetric Snaps Thermal Expansion
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Solution Overview
Problem
Gas powered turbines face challenges in minimizing gas leakage between secondary air systems and the gas path due to the size of the gap between rotating and static components, which affects engine performance, and existing sealing mechanisms do not effectively manage centrifugal loads and thermal expansion differences.
Innovation Solution
The design incorporates a rotor disk cover plate with radially inward and outward facing snaps that are not aligned, a flexing portion for easy installation, and a knife edge seal, allowing for secure attachment and accommodating thermal expansion differences between the cover plate and rotor disk, ensuring a tight seal both when heating and cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the cover plate is made small relative to the rotor disk, then the centrifugal load on the rotor is minimized, but the sealing effectiveness is reduced
Solution Approach 1:
The patent applies local quality by concentrating sealing features (knife edge seals, labyrinths) at specific critical locations on the cover plate where gas leakage occurs, rather than requiring the entire cover plate to be large. This allows the cover plate to remain small while maintaining sealing effectiveness at key interfaces between rotating and static components.
Solution Approach 2:
The patent employs composite materials with different thermal expansion coefficients for the cover plate and rotor disk. This allows the cover plate to maintain proper dimensional relationships and sealing clearances across temperature variations without requiring a larger size, thus maintaining both low centrifugal load and effective sealing.
2Reliability
If the gap between rotating and static components is reduced to minimize gas leakage, then sealing effectiveness is improved, but the risk of contact and mechanical failure increases
Solution Approach 1:
The patent uses flexible sealing elements such as labyrinths and knife edge seals that can deflect and accommodate minor misalignments or thermal expansions. These flexible features maintain tight sealing gaps without rigid contact, preventing mechanical failure while ensuring effective sealing against gas leakage.
Solution Approach 2:
The patent utilizes thermal expansion parameter changes by selecting materials with different coefficients of thermal expansion for the cover plate and rotor disk. As temperature varies during operation, the differential expansion automatically adjusts the gap dimensions, maintaining optimal sealing clearance without risking contact between rotating and static components.
3Ease of manufacture
If the cover plate and rotor disk are made of the same material, then manufacturing is simplified, but thermal expansion differences during operation are not accommodated
Solution Approach 1:
The patent deliberately uses composite materials with different thermal expansion coefficients for the cover plate and rotor disk. This material selection strategy allows the assembly to accommodate thermal expansion differences during operation, maintaining proper clearances and sealing effectiveness across the temperature range experienced in turbine operation.
4Manufacturing precision
If the snaps are radially aligned for simple manufacturing, then manufacturing precision is improved, but the seal tightness during thermal cycles is reduced
Solution Approach 1:
The patent employs asymmetric positioning of the snaps relative to each other radially. This asymmetric arrangement, combined with the flexing portion, allows the cover plate to differential expand and contract during thermal cycles while maintaining consistent seal tightness. The non-aligned snaps create a compliance mechanism that accommodates thermal distortion without compromising sealing effectiveness.
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
This design effectively reduces gas leakage and manages centrifugal loads by using opposing snap directions and different thermal expansion materials, maintaining a secure seal across varying operational temperatures and engine conditions.
Implementation Method 1
a flexing portion operable to be flexed during installation and to return to an unflexed state after installation without permanent deformation
Implementation Method 2
the cover plate and a corresponding rotor are constructed of different materials having different thermal expansion rates
Implementation Method 3
The knife edge protrusion interfaces with a corresponding static component to form a seal and minimize gas leakage between the secondary air systems and the gas path
Data Source
AI summary
A cover plate for a rotor disk in a gas turbine machine includes a cylindrical body having multiple outward facing snaps and multiple inward facing snaps.