Segmented Sealing Fin Structure for Turbine Swirl Vibration

Solution Overview

Problem

In rotary machines like steam turbines and gas turbines, the reduction in rotor diameter and increase in blade stages lead to increased self-excited vibration due to swirling flows, which existing structures fail to effectively suppress.

Innovation Solution

The implementation of a rotor-blade-side sealing apparatus with sealing fins that include first and second extending portions, which guide and mix the swirling flow to reduce its circumferential velocity, thereby suppressing self-excited vibration. These fins are designed to extend in a manner that creates a spiral flow and turbulence, reducing the velocity components of the swirling flow.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the rotor diameter is reduced and blade stages are increased to enhance turbine efficiency, then turbine efficiency is improved, but self-excited vibration of the rotor is generated more easily

Engineering Contradiction:

Improveturbine efficiencyVSAvoidself-excited vibration

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The sealing fin is divided into multiple segments (first sealing-fin main body portion and second sealing-fin main body portion) separated by a gap portion. This segmentation allows the working fluid to pass through the gap, creating a velocity component that suppresses the circumferential velocity of the swirl flow, thereby reducing self-excited vibration while maintaining turbine efficiency.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The sealing fin includes extending portions that extend in both the axial direction and the circumferential direction, creating a three-dimensional structure. The first extending portion extends toward the upstream side in the axial direction as it approaches the downstream side in the rotation direction, generating a spiral flow that effectively suppresses the swirl flow and self-excited vibration.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Object-affected harmful factors

If sealing fins are designed to suppress swirl flow, then self-excited vibration is reduced, but the structural complexity of the sealing apparatus increases

Engineering Contradiction:

Improveself-excited vibrationVSAvoidsealing fin structure

Core Design Contradiction:

Object-affected harmful factorsVSDevice complexity

Solution Approach 1:

The sealing fin is divided into multiple segments (first sealing-fin main body portion and second sealing-fin main body portion) separated by a gap portion. This segmentation allows the working fluid to pass through the gap, creating a velocity component that suppresses the circumferential velocity of the swirl flow, thereby reducing self-excited vibration while maintaining turbine efficiency.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The sealing fin includes extending portions that extend in both the axial direction and the circumferential direction, creating a three-dimensional structure. The first extending portion extends toward the upstream side in the axial direction as it approaches the downstream side in the rotation direction, generating a spiral flow that effectively suppresses the swirl flow and self-excited vibration.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 described sealing apparatus effectively suppresses self-excited vibrations in rotary machines by generating a spiral flow and turbulence, thereby reducing the circumferential velocity of the swirling flow and minimizing rotor vibrations.

Implementation Method 1

a spiral flow can be generated in the upstream swirl flow, and the circumferential velocity of the upstream swirl flow can be suppressed

Methodology Applied

Scientific EffectSpiral flow: Vortex Ring

Implementation Method 2

a part of the upstream swirl flow flows into the downstream side of the sealing fin in the axial direction of the rotor main body via the gap portion. Thus, the working fluid flowing into the downstream side of the sealing fin in the axial direction of the rotor main body via the gap portion can affect the flow of the downstream swirl flow, and the circumferential velocity of the downstream swirl flow can be suppressed

Methodology Applied

Scientific EffectTurbulence: Turbulence

Data Source

PatentUS10907499B2Rotor-blade-side sealing apparatus, stationary-blade-side sealing apparatus, and rotary machine

Publication Date: 2021.02.02 MITSUBISHI HEAVY IND LTD

AI summary

A rotor-blade-side sealing apparatus is configured to seal leakage of working fluid between rotor blade rings connected to distal end portions of rotor blade main bodies attached so as to extend in a radial direction from a rotor main body configured to rotate about an axis in a casing, and an inner circumferential surface of the casing. The rotor-blade-side sealing apparatus includes a sealing fin protruding in the radial direction from a side of the inner circumferential surface of the casing toward one of the rotor blade rings and extending in a circumferential direction. The sealing fin includes: a first sealing-fin main body portion and a second sealing-fin main body portion separated from each other in the circumferential direction across a gap portion that is a discontinuity along the circumferential direction; and an extending portion extending toward an upstream side in an axial direction of the rotor main body.