Coanda Labyrinth Seal Geometry for Rotating Machine Leakage Control
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Solution Overview
Problem
Existing rotating machine seals, such as labyrinth seals, suffer from performance degradation due to flow leakage between higher and lower pressure areas, with prior designs failing to optimally utilize the Coanda effect and coolant injection, leading to inefficiencies and power loss.
Innovation Solution
A seal design featuring teeth with transverse surfaces and a third surface that diverts incoming flow into cavities using the Coanda effect, with rounded or beveled edges, and specific geometric ratios to enhance flow diversion and reduce leakage, comprising a base, rows of teeth, and cavities between them, connected to both the rotor and stator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional labyrinth seal geometry is used, then the seal structure is simple, but flow leakage from higher pressure to lower pressure area increases
Solution Approach 1:
The patent applies local quality by creating asymmetric tooth geometry with a first surface having a first angle and a second surface having a second angle different from the first. This local geometric variation optimizes flow control at specific locations within the seal, redirecting flow into cavities to reduce leakage while maintaining overall structural simplicity.
Solution Approach 2:
The patent introduces a third dimension to the tooth geometry by adding a third surface that extends between the first and second surfaces. This additional surface creates a more complex three-dimensional flow path that directs flow into cavities, effectively reducing leakage without significantly increasing overall device complexity.
2Productivity
If teeth with asymmetric surfaces are used, then flow diversion into cavities improves, but manufacturing complexity increases
Solution Approach 1:
The patent optimizes specific geometric parameters including the first angle and second angle of tooth surfaces, as well as the dimensions of cavities. By carefully selecting these parameters, the design achieves effective flow diversion while maintaining manufacturability through standardized angular measurements and proportional relationships.
3Loss of energy
If the third surface is highly curved, then flow diversion towards cavity is maximized, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs curved surfaces, particularly the third surface extending between the first and second surfaces, to utilize the Coanda effect and redirect flow into cavities. The curvature is optimized to achieve effective flow capture and kinetic energy dissipation while remaining within achievable manufacturing tolerances for industrial applications.
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 seal effectively diverts a greater portion of the incoming flow into cavities, dissipating kinetic energy and reducing leakage, thereby improving the rotating machine's performance and reducing power loss by better insulating the lower pressure side from the higher pressure side.
Implementation Method 1
the tooth has an edge, defined by the third surface and by the second surface, being rounded or bevelled so that a part of the flow is deviated towards the cavity adjacent to the second surface due to the Coanda effect
Data Source
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AI summary
A seal for a rotating machine; the seal (6; 106; 206; 306) comprising at least one row of teeth (15a, 15b), the row extending from a first side (6a) to a second side (6b) along an axial direction (B); at least one cavity (16) arranged between respective two adjacent teeth (15a, 15b) of the row of teeth (15a, 15b); wherein at least one of the teeth (15a, 15b) has a first and a second surface (20a, 21a; 20a, 20b) which extend transversely to the axial direction (B), and a third surface (22a, 22b) which extends between the first and the second surface (20a, 21a; 20a, 20b) and transversely thereto; wherein the third surface (22a, 22b) is shaped so as to divert the incoming flow (F) towards the cavity (16a, 16b) adjacent to the second surface (21a, 21b).