Controlled Gap Seal Surface Layout for Vortex Shedding Mitigation
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Solution Overview
Problem
Controlled gap seals in gas turbine engines experience excitation and potential cracking due to air flow-induced vortex shedding, which reduces the lifespan of the seal runner.
Innovation Solution
Incorporating surface discontinuities such as tabs and grooves circumferentially distributed around the central axis on the runner, ring, and housing to disrupt the airflow and mitigate vortex shedding, with varying spacings to attenuate dominant excitation frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tight clearance gap is used in the controlled gap seal, then sealing effectiveness is improved, but air flow-induced excitation and vortex shedding increase, leading to runner cracking
Solution Approach 1:
The seal runner surface is segmented into multiple discrete surface discontinuities (tabs, grooves, or protrusions) circumferentially distributed around the central axis. These segmented features disrupt the continuous airflow path, breaking up vortex shedding patterns and reducing excitation forces while maintaining the tight clearance gap for effective sealing.
Solution Approach 2:
Surface discontinuities are strategically placed at specific locations on the seal runner or ring surface within the gap region. By concentrating flow-disrupting features only where needed (locally) rather than modifying the entire seal structure, the design maintains tight clearance overall while creating localized turbulence to mitigate vortex shedding and excitation.
2Object-affected harmful factors
If surface discontinuities are added to disrupt airflow, then excitation frequencies are reduced, but device complexity increases
Solution Approach 1:
The airflow disruption is achieved through multiple simple, discrete surface discontinuities rather than a complex continuous structure. Each tab, groove, or protrusion is a simple geometric feature, but their collective arrangement provides effective flow disruption. This segmented approach reduces excitation frequencies while keeping individual components simple and manufacturable.
3Object-affected harmful factors
If non-uniform spacing of surface discontinuities is used, then dominant excitation frequencies are attenuated, but manufacturing precision requirements increase
Solution Approach 1:
The surface discontinuities are deliberately arranged with non-uniform spacing patterns rather than uniform distribution. This asymmetric arrangement prevents the formation of strong dominant excitation frequencies by avoiding periodic flow patterns. The intentional asymmetry in spacing breaks up resonant conditions while the features themselves remain simple geometric shapes that are manufacturable with standard tolerances.
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 surface discontinuities effectively disrupt the airflow and reduce the strength of excitation frequencies, enhancing the durability and lifespan of the seal runner by minimizing vibration-induced stress.
Implementation Method 1
A flow of air may develop between two zones separated by the seal and through the controlled gap. In some cases, this flow of air induces excitation of the rotating seal runner. The excitation may result in cracking of the seal runner.
Implementation Method 2
disrupting a flow circulating within the gap by circulating the flow between surface discontinuities circumferentially distributed around a central axis of the controlled gap seal
Data Source
AI summary
There is disclosed a controlled gap seal for a gas turbine engine including a ring configured to be in a sealing engagement with a housing and a runner configured for rotation relative to the ring about the central axis. The runner has a runner face facing a ring face of the ring. The ring face is spaced apart from the runner face by a gap. A plurality of surface discontinuities are circumferentially distributed around the central axis on the runner face and/or the ring face. The plurality of surface discontinuities are spaced relative to one another such that a first set of adjacent surface discontinuities are circumferentially spaced from each other at a different distance than a second set of adjacent surface discontinuities. A method of using the controlled gap seal is disclosed.