Flattened Seal Ring Geometry for Turbine Leakage Control

Solution Overview

Problem

In steam turbines, deformation due to gravity or heat can cause the tip end portion of rotor blades to contact seal fins, increasing steam leakage and deteriorating performance, while increasing the gap size to prevent contact leads to more steam leakage.

Innovation Solution

A method for manufacturing a seal ring with a flattened shape, using a first and second semi-circular member with offset centers, allowing for a circular seal ring assembly that maintains a minimal steam leakage gap.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If the size of the minute gap between the tip end portion of the rotor blade and the tip of each seal fin is decreased, then the amount of leaked steam passing through the gap is reduced, but the deformation in casing may cause the tip end portion of the rotor blade and the tip of each seal fin to contact each other

Engineering Contradiction:

Improvesteam leakageVSAvoidcontact prevention

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The seal fin tip is designed with an asymmetric shape where the diameter in the vertical direction is larger than the diameter in the horizontal direction. This asymmetric geometry allows the seal fin to maintain a minimal gap with the rotor blade tip in the horizontal direction to reduce steam leakage, while the larger vertical diameter provides clearance to prevent contact when casing deformation occurs vertically due to gravity or heat effects.

Inventive Principle:

Principle #4Asymmetry

2Reliability

If the size of the minute gap between the tip end portion of the rotor blade and the tip of each seal fin is increased, then contact between the tip end portion of the rotor blade and the tip of each seal fin is prevented, but the amount of the leaked steam passing through this minute gap increases

Engineering Contradiction:

Improvecontact preventionVSAvoidsteam leakage

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The seal fin tip is designed with an asymmetric shape where the diameter in the vertical direction is larger than the diameter in the horizontal direction. This asymmetric geometry allows the seal fin to maintain a minimal gap with the rotor blade tip in the horizontal direction to reduce steam leakage, while the larger vertical diameter provides clearance to prevent contact when casing deformation occurs vertically due to gravity or heat effects.

Inventive Principle:

Principle #4Asymmetry

3Ease of manufacture

If a perfect circular shape is used for the tip of each seal fin, then manufacturing is simplified, but the seal ring cannot simultaneously achieve minimal steam leakage and prevent contact under casing deformation

Engineering Contradiction:

Improveseal fin shapeVSAvoidsteam leakage

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The seal fin tip is designed with an asymmetric shape where the diameter in the vertical direction is larger than the diameter in the horizontal direction. This asymmetric geometry allows the seal fin to maintain a minimal gap with the rotor blade tip in the horizontal direction to reduce steam leakage, while the larger vertical diameter provides clearance to prevent contact when casing deformation occurs vertically due to gravity or heat effects.

Inventive Principle:

Principle #4Asymmetry

Data Source

PatentUS12590545B2Method for manufacturing seal ring, method for assembling turbine, and turbine

Publication Date: 2026.03.31 MITSUBISHI HEAVY IND LTD

AI summary

A method for manufacturing a seal ring according to at least one embodiment is a method for manufacturing a circular seal ring, including: a step of forming a seal fin by turning an inner peripheral portion of a first member and a second member each having a semi-circular shape in a state where both end portions of each of the first member and the second member are in contact with each other; and a step of turning an outer peripheral portion of the first member and the second member in a state where the both end portions of each of the first member and the second member are spaced apart from each other.