Steam Turbine Casing Position Adjustment Device

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Solution Overview

Problem

The thermal expansion difference between the rotor and the inner casing in steam turbines leads to inefficiencies due to seal misalignment and leakage, and existing adjustment methods lack accurate control and are difficult to implement in existing turbines, especially concerning thrust load management and space constraints.

Innovation Solution

A casing position adjustment device that uses a low-pressure casing end plate with actuators to adjust the axial position of the casing relative to the rotor, anchored by bolts and equipped with sensors for feedback control, allowing for precise thermal expansion difference management and reduced thrust load on actuators.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a large clearance is designed in advance to accommodate thermal expansion difference, then seal fins can avoid contact with seal dams, but leakage amount increases and turbine efficiency degrades

Engineering Contradiction:

Improveseal alignmentVSAvoidleakage amount

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent introduces a dynamic adjustment mechanism that actively modifies the relative position between the rotor and casing based on real-time thermal expansion measurements. This allows the clearance to be optimized dynamically rather than fixed statically, maintaining minimal clearance under thermal expansion conditions while preventing seal contact and reducing leakage.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the clearance parameter dynamically by adjusting the relative axial position of the rotor and casing. Through controlled displacement of one component relative to the other, the clearance is optimized for different thermal states, preventing both seal contact and excessive leakage.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If passive control with shaft joint is used to absorb thermal expansion, then thermal expansion difference is reduced, but sensory feedback is not performed and control accuracy within target value range is insufficient

Engineering Contradiction:

Improvethermal expansion absorptionVSAvoidcontrol accuracy

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent incorporates sensors that continuously measure the thermal expansion difference between rotor and casing, feeding this information back to a control system. The control system then adjusts the relative position accordingly, achieving precise control within target value ranges through closed-loop feedback rather than passive absorption.

Inventive Principle:

Principle #23Feedback

3Reliability

If actuator is incorporated in casing similar to thrust bearing for active control, then thermal expansion difference can be adjusted, but prompt action cannot be taken in case of trouble and application to existing steam turbine is difficult

Engineering Contradiction:

Improvethermal expansion adjustmentVSAvoidactuator installation complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the adjustment function into a separate, modular device that can be independently installed and operated. This modular approach allows the thermal expansion adjustment mechanism to be added to existing turbines without reconfiguring the entire casing or thrust bearing system, reducing installation complexity and improving maintainability.

Inventive Principle:

Principle #1Segmentation

4Loss of energy

If seal fins are positioned close to rotor side to minimize clearance, then leakage is reduced, but seal fins may be brought into contact with seal dams under thermal expansion

Engineering Contradiction:

Improveleakage amountVSAvoidseal contact risk

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The system dynamically adjusts the relative position between rotor and casing to maintain optimal seal clearance under varying thermal conditions. This prevents seal contact during thermal expansion while minimizing clearance to reduce leakage, achieving both objectives through active position control.

Inventive Principle:

Principle #15Dynamics

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 solution effectively cancels the thermal expansion difference, improving turbine efficiency by maintaining optimal seal alignment and reducing the risk of blade contact and actuator failure, while allowing for compact and reliable operation.

Implementation Method 1

the rotor and a turbine casing (inner casing) are increased in length from the thrust bearing in the rotor axial direction due to a phenomenon called 'thermal expansion'

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS11028731B2Casing position adjustment device

Publication Date: 2021.06.08 MITSUBISHI POWER LTD

AI summary

In a steam turbine including a rotor including a free side end fixed by a journal bearing in a radial direction and a fixed side end fixed by a thrust bearing in an axial direction, and a casing including a fixed side end fixed by the thrust bearing in the axial direction, a casing position adjustment device is configured to adjust an axial position of the casing with respect to the rotor due to thermal expansion. The casing position adjustment device includes: a low-pressure casing end plate, which is an end plate oriented to a free side in the axial direction in a low-pressure casing of the casing, and has a diaphragm deformable in the axial direction; and actuators, which are configured to deform the low-pressure casing end plate so that the low-pressure casing end plate extends toward the free side in the axial direction.