Controlled Gap Seal Surface Features to Suppress Vortex Shedding
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Solution Overview
Problem
Controlled gap seals in gas turbine engines face issues with excitation of the rotating seal runner due to air flow, leading to potential cracking and reduced lifespan, primarily caused by vortex shedding from the air flow between the seal components.
Innovation Solution
Incorporation of surface discontinuities, such as tabs and grooves, circumferentially distributed around the central axis of the controlled gap seal, either upstream or downstream of the gap, to disrupt the flow of air and mitigate vortex shedding, thereby reducing excitation and vibration frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a tight clearance gap is maintained between the ring and runner, then sealing effectiveness is improved, but air flow induces excitation and vortex shedding that can crack the seal runner
Solution Approach 1:
The patent applies local quality by introducing surface discontinuities (protrusions and recesses) at specific locations on the runner and/or ring surfaces. These localized features disrupt the air flow in the gap region without affecting the overall tight clearance sealing function. The discontinuities are strategically positioned to break up vortex formation while maintaining the necessary sealing clearance.
Solution Approach 2:
The surface discontinuities act as intermediaries between the air flow and the seal runner structure. By introducing these intermediate features, the patent modifies the flow characteristics to reduce excitation forces. The discontinuities serve as a mediating element that alters the harmful air flow patterns without compromising the sealing function.
2Object-affected harmful factors
If surface discontinuities are added to disrupt air flow, then excitation frequencies are attenuated, but device complexity increases
Solution Approach 1:
The patent applies segmentation by dividing the continuous surface of the runner or ring into discrete segments with protrusions and recesses. Instead of using a complex overall structure, the solution breaks down the flow disruption function into multiple simple, equally spaced surface discontinuities. This segmented approach reduces complexity compared to a fully complex design while effectively disrupting excitation frequencies.
Solution Approach 2:
The patent changes geometric parameters by introducing simple surface discontinuities with specific dimensions and spacing. Rather than fundamentally redesigning the entire seal structure, the solution modifies local geometric parameters (protrusion height, recess depth, spacing between discontinuities) to achieve flow disruption. This parameter-based approach maintains structural simplicity while addressing the excitation problem.
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 attenuate the strength of dominant excitation frequencies, enhancing the lifespan of the seal runner by disrupting the air flow and mistuning vibration modes, thus preventing cracking and improving operational reliability.
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
Data Source
AI summary
There is disclosed a controlled gap seal for a gas turbine engine. The seal has a ring annularly and continuously extending about a central axis. A runner that is configured for rotation about the central axis and rotatable relative to the ring. The runner has a face facing a face of the ring. The face of the ring is spaced apart from the face of the runner by a gap. Surface discontinuities are circumferentially distributed around the central axis. The surface discontinuities are located at specific locations and distributed in specific ways. A method of using the controlled gap seal is disclosed.