Steam Turbine Inner Casing Support Beam Alignment

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Solution Overview

Problem

In steam turbines, the deformation of the outer casing due to vacuum and rotor loads leads to displacement of the rotor bearing and inner casing, causing misalignment between the rotary and stationary units, which results in steam leakage and performance degradation.

Innovation Solution

The implementation of supporting beams inside the outer casing that extend in the axial direction of the turbine rotor, with beam end portions supported by foot plates on the foundation, allowing the inner casing to be directly supported without relying on the outer casing, thereby isolating it from deformation-induced displacements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the inner casing is supported by the outer casing lower half, then the structure is simplified and ease of manufacture is improved, but the inner casing is displaced due to deformation of the outer casing from vacuum load and rotor load, worsening manufacturing precision and reliability

Engineering Contradiction:

Improveease of assembly and disassemblyVSAvoidalignment between rotary and stationary units

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The support function is segmented into two independent systems: the outer casing supported by foot plates on the foundation, and the inner casing supported by supporting beams on the foundation. This segmentation prevents the transmission of deformation from the outer casing to the inner casing, while maintaining ease of assembly through modular construction.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The foundation acts as an intermediary between the outer casing and the inner casing. By supporting both the outer casing (via foot plates) and the inner casing (via supporting beams) on the foundation, the foundation mediates the support function while isolating the inner casing from deformation-induced displacements of the outer casing.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If the bearing base is supported by the cone on the outer casing, then the device complexity is reduced, but the rotor bearing is displaced by deformation of the outer casing, worsening reliability

Engineering Contradiction:

Improvenumber of support componentsVSAvoidposition stability of rotor bearing

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The foundation serves as an intermediary support for the bearing base, replacing the cone on the outer casing as the support element. This intermediary support on the foundation isolates the rotor bearing from deformation-induced displacements, maintaining position stability while managing device complexity through strategic simplification.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The support function for the bearing base is extracted from the outer casing (by removing dependence on the cone) and transferred to the foundation. This extraction eliminates the harmful coupling between outer casing deformation and rotor bearing position, improving reliability without significantly increasing device complexity.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If the gap between rotary unit and stationary unit is increased to prevent contact, then reliability is improved by preventing contact, but steam leakage increases and turbine performance degrades, worsening productivity

Engineering Contradiction:

Improveprevention of contact between rotary and stationary unitsVSAvoidturbine performance

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The supporting beams provide beforehand cushioning support to the inner casing (stationary unit), compensating for potential displacement due to thermal expansion or other factors. This prior support maintains the gap between the rotary and stationary units at an optimal level, preventing contact while minimizing steam leakage, thus protecting both reliability and productivity.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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

This configuration maintains the alignment between the rotary and stationary units, reducing steam leakage and enhancing turbine performance by preventing deformation-induced misalignment and allowing for efficient thermal expansion absorption.

Implementation Method 1

allowing for efficient thermal expansion absorption

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS10487692B2Steam turbine

Publication Date: 2019.11.26 KK TOSHIBA

AI summary

A steam turbine according to an embodiment includes an outer casing; an inner casing housed in the outer casing; a turbine rotor penetrating the inner casing and the outer casing; and a supporting beam provided inside the outer casing. The supporting beam extends in an axial direction of the turbine rotor and supports the inner casing. The outer casing includes outer casing supporting portions which are provided at both ends of the outer casing in the axial direction and are supported by the foundation. The supporting beam has beam end portions provided at both ends in the axial direction. Each of the outer casing supporting portions includes a supporting surface that supports the corresponding beam end portion.