Diffuser Seal Shoe Geometry for Non-Contact Seal Flutter Reduction
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Solution Overview
Problem
Existing non-contact seals for rotational equipment face challenges in improving sealing efficiency and reducing seal flutter, particularly in gas turbine engines, where existing designs do not effectively manage pressure differentials and rotational dynamics.
Innovation Solution
A seal device with a plurality of seal shoes, a seal base, and spring elements, featuring a diffuser structure and a ramp structure, which are arranged circumferentially around an axis to manage pressure differentials and reduce seal flutter, utilizing a diffuser surface that increases in radius axially to enhance sealing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional non-contact seal designs are used, then the seal structure is simple, but sealing efficiency is insufficient and seal flutter occurs
Solution Approach 1:
The seal shoe is divided into multiple functional surfaces: a seal surface for sealing contact, a diffuser surface for pressure management, and a ramp surface for flow control. This segmentation allows each surface to perform its specific function optimally, improving sealing efficiency while managing the complexity through functional specialization
Solution Approach 2:
The diffuser surface is configured with an increasing radius in the axial direction, creating a three-dimensional pressure management structure. This dimensional approach allows pressure differentials to be managed across the axial dimension, reducing seal flutter while maintaining an efficient sealing geometry
2Reliability
If existing seal designs are used, then manufacturing is straightforward, but pressure differentials are not effectively managed leading to increased fluid leakage
Solution Approach 1:
Different surfaces of the seal shoe are given different geometric qualities: the seal surface has a specific radius for sealing contact, the diffuser surface has an increasing radius for pressure management, and the ramp surface has a controlled angle for flow management. This local differentiation of geometric properties enables effective pressure differential management across different functional zones
Solution Approach 2:
The diffuser surface is designed with a curved geometry where the radius increases in the axial direction. This curvature creates a gradual pressure transition zone that effectively manages pressure differentials and reduces fluid leakage, while the curved geometry can be manufactured using standard machining or additive processes
3Reliability
If conventional seal shoes are used, then the device is simple, but seal flutter increases and sealing performance deteriorates
Solution Approach 1:
The diffuser surface acts as an intermediary structure between the seal surface and the downstream environment. It gradually manages pressure differentials through its increasing radius geometry, preventing sudden pressure changes that cause seal flutter, while the ramp surface serves as an intermediary for controlling fluid flow onto the seal surface
Solution Approach 2:
The seal shoe geometry parameters are optimized: the diffuser surface radius increases axially to manage pressure gradients, the ramp surface angle is controlled to optimize flow conditions, and the seal surface radius is specified for optimal sealing contact. These parameter changes reduce seal flutter by creating stable pressure and flow conditions
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 effectively seals the annular gap between rotating and stationary structures, reducing seal flutter and enhancing sealing efficiency by managing pressure differentials and improving pressure distribution, thereby minimizing fluid leakage.
Implementation Method 1
A diffuser radius measured from the axis to the diffuser surface increases as the diffuser surface extends axially along the axis from the interface location to an axial distal side of the first seal shoe
Implementation Method 2
The spring elements connect and extend between the annular array of the seal shoes and the seal base
Data Source
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AI summary
An apparatus is provided for rotational equipment which includes a seal device. The seal device (38) includes a plurality of seal shoes (61), a seal base (60) and a plurality of spring elements (62). The seal shoes (61) are arranged circumferentially around an axis (33) in an annular array. A first of the seal shoes (61) includes a seal surface (122) and a diffuser surface (118). The seal surface (122) extends axially along the axis (33) to an axial interface location (130) where the seal surface (122) axially meets the diffuser surface (118). A minimum radius (132) of the first seal shoe (61) measured from the axis (33) to the seal surface (122) is defined at least at the axial interface location (130). A diffuser radius (126) measured from the axis (33) to the diffuser surface (118) increases as the diffuser surface extends axially along the axis from the interface location (130) to an axial distal side (124) of the first seal shoe (61). The spring elements (62) connect the seal shoes (61) and the seal base (60).