Labyrinth Seal Outlet Geometry for Wear-Tolerant Leakage Control
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Solution Overview
Problem
Labyrinth seals with seal fins in rotary machines, such as gas turbines, suffer from wear-induced increased gap size between the rotary and stationary bodies, leading to deteriorating gas leakage suppression effectiveness.
Innovation Solution
A labyrinth seal configuration featuring seal fins with a downstream wall surface and a cavity surface that generates vortices, reducing gas leakage through a larger radial gap by directing gas flow along these surfaces, even when the gap dimensions are slightly larger.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If seal fins are used to reduce the opposing gap between rotary and stationary bodies, then gas leakage suppression is improved, but the seal fin tip wears away due to contact with the opposing surface, causing the gap to increase and leakage suppression to deteriorate
Solution Approach 1:
The patent extracts the sealing function from the seal fin tip contact mechanism and relocates it to a downstream location. The seal fin no longer needs to contact the opposing surface to achieve sealing, as the sealing action is transferred to the downstream wall surface and cavity surface combination, eliminating wear at the fin tip.
Solution Approach 2:
The patent shifts the sealing mechanism from a radial dimension (seal fin tip contact) to an axial dimension (downstream wall surface and cavity surface interaction). By creating a vortex flow pattern in the downstream space, the sealing effect is achieved through three-dimensional flow control rather than simple radial gap closure.
2Reliability
If the opposing gap is reduced using seal fins, then gas leakage is suppressed, but the structure becomes complex and manufacturing difficult
Solution Approach 1:
The downstream wall surface serves multiple functions: it guides gas flow, creates the vortex pattern, and provides the sealing surface. The cavity surface similarly performs flow guidance and sealing functions. This multi-functionality reduces the need for additional specialized components, simplifying the overall structure despite the sophisticated flow control mechanism.
3Reliability
If the gap between first outlet surface and second outlet surface is made small to suppress leakage, then gas leakage is reduced, but manufacturing precision requirements increase and the structure becomes more sensitive to wear
Solution Approach 1:
The vortex flow pattern is established in advance by the downstream wall surface and cavity surface configuration, before the gas reaches the outlet gap. This preliminary flow conditioning creates a pressure distribution and flow pattern that suppresses leakage through the outlet gap, allowing for larger gap dimensions without sacrificing sealing performance.
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
Effectively suppresses gas leakage at the outlet portion by creating vortices that minimize gas outflow, maintaining leakage control despite slight deviations in gap dimensions.
Implementation Method 1
the gas having passed through the most downstream seal fin collides with the downstream wall surface, then flows along the downstream wall surface, and further flows along the cavity surface. With this, a vortex is generated in a downstream space surrounded by the most downstream seal fin, the downstream wall surface, and the cavity surface
Data Source
AI summary
Provided is a labyrinth seal including a first structure; and a second structure opposing the first structure. The first structure includes seal fins located at intervals in an axial direction and extending toward the second structure; a downstream wall surface located most downstream one of the seal fins and extending toward the second structure. A tip of the downstream wall surface located at a side of a tip of the most downstream seal fin, the side being close to the second structure in a radial direction and having a first outlet surface extending from the tip of the downstream wall surface toward a downstream side. The second structure includes a second outlet surface opposing the first outlet surface, a radial gap between the first outlet surface and the second outlet surface; and a cavity surface located upstream of the second outlet surface recessed away from the first structure.