Step Seal Protrusion for Turbo Machine Leak Suppression
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Solution Overview
Problem
Traditional step-type labyrinth seals in turbo machines do not effectively suppress fluid leaks due to insufficient vortex generation caused by straight radius-direction walls and potential deviations from designed dimensions due to thermal expansion, leading to inefficient leak loss reduction.
Innovation Solution
A step seal design featuring a sharp protrusion between the step face and opposed face, with specific dimensions and angles to enhance vortex formation and guide fluid flow away from the clearance, reducing leak steam flow and promoting a contraction flow effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a straight radius-direction wall is used in the step seal, then the structure is simple and easy to manufacture, but the vortex generation capability is insufficient leading to poor leak suppression
Solution Approach 1:
The patent applies curvature by replacing the straight radius-direction wall with a curved surface that has a specific curvature radius. This curved surface actively generates stronger vortices in the fluid flow, enhancing the contraction effect and improving leak suppression performance while maintaining manufacturing feasibility through standard curving processes
2Loss of energy
If the step seal height is increased to improve vortex growth, then leak suppression improves, but the device becomes more complex and harder to manufacture
Solution Approach 1:
The patent changes key parameters including the curvature radius of the curved surface, the height of the step seal, and the position of the protrusion. By optimizing these parameters within specific ranges, the invention achieves effective vortex generation and leak suppression without requiring excessive increases in step seal height, thus avoiding unnecessary complexity
3Adaptability or versatility
If the step seal dimensions deviate due to thermal expansion, then adaptability to thermal conditions improves, but vortex generation capability deteriorates leading to reduced leak suppression
Solution Approach 1:
The patent incorporates a protrusion that extends in the axial direction from the curved surface toward the seal fin. This protrusion is positioned in advance to actively guide fluid flow and enhance vortex generation. By pre-positioning this flow-guiding feature, the system maintains effective vortex generation even when dimensional deviations occur due to thermal expansion, ensuring consistent leak suppression
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 sharp protrusion design effectively weakens fluid flow into the clearance, enhances vortex growth, and stabilizes leak suppression, even under conditions of thermal expansion, thereby improving the efficiency and reducing leak loss in turbo machines.
Implementation Method 1
a radius-direction wall along the radius direction of the step section (step seal) of the shroud forms a main vortex of the operation fluid
Implementation Method 2
the action of a corner of the step section generates a separated vortex (vortex of the separated flow) from the main vortex at the upstream side of the seal fin. This separation vortex provides so-called contraction effect
Data Source
AI summary
There are provided a step seal, a seal structure, a turbo machine, and a method for manufacturing a step seal. The step seal suppresses leak of a fluid from a gap between a first structure and a second structure and is formed on the first structure so as to have a clearance between the step seal and a seal fin formed on the second structure. The first structure and the second structure face each other in a radius direction with the gap inbetween and rotate around an axis line relative to each other. The step seal includes: a step seal body having a step face facing an upstream side of a flow direction of the fluid and an opposed face facing the second structure; and a protrusion formed between the step face and the opposed face.