Labyrinth Seal Protrusions for Rotating Machine Leakage Control
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Solution Overview
Problem
The step type labyrinth seal has higher manufacturing costs and is prone to contact issues due to expansion differences, while the direct passage type labyrinth seal suffers from inferior sealing performance due to blowout effects, leading to reduced sealing efficiency.
Innovation Solution
A seal structure with a peripheral surface parallel to the axis line, featuring seal fins and protrusions that create re-adhesion edges and cavities to stabilize the leak current, reducing kinetic energy and promoting eddy formation to enhance sealing performance, thereby preventing contact and minimizing blowout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a step type labyrinth seal is used to improve sealing performance, then sealing performance is improved, but manufacturing costs increase and contact between components may occur due to expansion differences
Solution Approach 1:
The seal structure is divided into multiple seal fins arranged in series along the axial direction, creating multiple clearances that work together to reduce leak current. This segmentation allows the direct passage type seal to achieve improved sealing performance without requiring the complex stepped structure, thereby reducing manufacturing costs while maintaining reliability.
Solution Approach 2:
The protrusion is strategically positioned at specific locations between seal fins to create re-adhesion edges and cavities. This local modification optimizes the flow characteristics of the leak current at critical points, enhancing sealing performance in the direct passage type seal without requiring the extensive structural changes of a step type seal, thus avoiding increased manufacturing costs.
2Ease of manufacture
If a direct passage type labyrinth seal is used to reduce manufacturing costs, then manufacturing costs are reduced, but sealing performance degrades due to blowout effects
Solution Approach 1:
The protrusion acts as an intermediary element between the seal fins, creating re-adhesion edges that intercept the leak current and cavities that generate eddies. This intermediary structure suppresses the blowout effect by disrupting the direct passage of the leak current, thereby improving sealing performance while maintaining the simple and cost-effective direct passage type seal design.
Solution Approach 2:
The protrusion modifies the flow parameters of the leak current by creating re-adhesion edges that change the flow direction and cavities that increase turbulence. These parameter changes reduce the kinetic energy of the leak current and suppress blowout effects, improving sealing performance without complicating the overall seal structure or increasing manufacturing costs.
3Ease of manufacture
If seal fins are arranged with larger intervals to reduce manufacturing complexity, then ease of manufacture is improved, but blowout effects increase and sealing performance degrades
Solution Approach 1:
The protrusion with re-adhesion edges is positioned upstream to intercept and redirect the leak current before it can develop into a high-velocity jet. This preliminary action prevents the blowout effect from developing, allowing larger intervals between seal fins without compromising sealing performance, thereby reducing structural complexity and improving ease of manufacture.
Solution Approach 2:
The protrusion creates cavities that generate eddies, converting the kinetic energy of the leak current into rotational flow. This converts the harmful blowout effect into a beneficial turbulent flow pattern that enhances mixing and reduces the coherence of the leak jet, improving sealing performance even with larger seal fin intervals and simpler structures.
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 proposed seal structure stabilizes sealing performance by reducing leak current and preventing contact between rotating components, even under expansion differences, while enhancing kinetic energy dissipation and reducing blowout effects.
Implementation Method 1
a first cavity where an eddy flowing along the upstream seal fin toward the peripheral surface is created
Implementation Method 2
a protrusion that forms a re-adhesion edge, to which a leak current having passed through a clearance of an upstream seal fin readheres
Implementation Method 3
a second cavity where a current causing a contraction current effect on a clearance of a downstream seal fin is created
Data Source
AI summary
A seal structure (2) for sealing a gap between a first structure body (10) and a second structure body (51). The seal structure includes: a peripheral surface formed on one of the first structure body and the second structure body; a plurality of seal fins (5) provided at intervals in the axial direction so as to form clearances (m) together with the peripheral surface and protrusions that form re-adhesion edges between pairs of axially adjacent seal fins; the re-adhesion edges being locations at which leak currents (SL) re-adhere that have passed through a clearance (mA) of an upstream seal fin; and the protrusions forming first cavities in which eddies (B1) are created that flow along the upstream seal fin toward the second structure body, and second cavities in which currents (B2) are created that cause a contraction current effect on a clearance (mB) of a downstream seal fin.