Arc-Fin Seal Layout for Leakage and Vibration Suppression
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Solution Overview
Problem
Rotary machines like steam turbines face challenges in suppressing leakage flow rates, which can lead to increased self-excited vibrations due to swirling flows, and existing solutions may exacerbate these vibrations when trying to improve turbine efficiency.
Innovation Solution
A sealing device with at least three arc-shaped fins, where the third fin is inclined or has a larger radial dimension than the first and second fins, forming a smaller seal gap, is used to reduce leakage flow rates and self-excited vibrations by altering the differential pressure distribution across the sealing portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the leakage flow rate is suppressed to improve turbine efficiency, then turbine efficiency is improved, but the exciting force of self-excited vibration increases
Solution Approach 1:
The sealing fins are configured with different radial dimensions and inclination angles at different axial positions. Specifically, the sealing fin on the downstream side has a larger radial dimension and greater inclination angle compared to upstream fins, creating localized variations in seal gap size that differentially affect leakage flow and vibration characteristics
Solution Approach 2:
The sealing device employs an asymmetric configuration where fins are not uniformly distributed but rather have varying radial dimensions and inclination angles along the axial direction. This asymmetric arrangement creates non-uniform differential pressure distribution that suppresses both leakage flow and self-excited vibration simultaneously
2Object-generated harmful factors
If seal fins are arranged to suppress swirl flow, then self-excited vibration is suppressed, but leakage flow rate increases
Solution Approach 1:
The sealing fins are configured with three-dimensional geometry including axial inclination angles and varying radial dimensions, rather than simple radial extensions. This multi-dimensional configuration allows the fins to simultaneously address swirl flow suppression and leakage flow control through complex flow interaction
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 configuration effectively suppresses leakage flow rates and self-excited vibrations in rotary machines by increasing the differential pressure across the sealing device, enhancing turbine efficiency without increasing the exciting force.
Implementation Method 1
The third fin satisfies at least either of following condition (a) or (b): (a) the third fin is disposed to be inclined with respect to a radial direction such that a tip end portion is located on a side of the first fin in the axial direction relative to a base end portion, and the third fin has a larger inclination angle than the first fin or the second fin with respect to the radial direction; or (b) the third fin has a larger radial dimension than the first fin or the second fin so as to form a smaller seal gap than the first fin or the second fin
Implementation Method 2
The configuration effectively suppresses leakage flow rates and self-excited vibrations in rotary machines by increasing the differential pressure across the sealing device
Data Source
AI summary
A sealing device according to at least one embodiment includes not less than three arc-shaped fins arranged in an axial direction. The arc-shaped fins include: a first fin which is one of two outermost fins located on an outermost side in the axial direction; a second fin disposed adjacent to the first fin in the axial direction; and at least one third fin disposed opposite to the first fin across the second fin in the axial direction. It is preferable that the third fin is disposed to be inclined with respect to a radial direction such that a tip end portion is located on a side of the first fin in the axial direction relative to a base end portion, and the third fin has a larger inclination angle than the first fin or the second fin with respect to the radial direction.