Steam Turbine Casing Heating for Thermal Expansion Control
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Solution Overview
Problem
The steam turbine's performance is compromised due to varying thermal expansion between the rotor and casing, leading to potential contact during startup or excessive clearance during operation, which degrades efficiency.
Innovation Solution
A steam turbine design incorporating a casing support unit with a first heating unit to adjust the thermal expansion of the casing and a second heating unit on flanges to manage the relative position between the rotor and casing, utilizing a control device to switch heating states based on temperature and clearance detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a small clearance is secured between the rotor and casing to reduce steam leakage loss, then the steam turbine performance is improved, but the rotor and casing may come into contact during startup or shutdown due to thermal expansion differences
Solution Approach 1:
The patent applies thermal expansion parameter changes by providing heating units that heat the casing support unit and flanges during startup and shutdown. This controlled thermal expansion creates additional clearance between the rotor and casing, preventing contact while maintaining the small clearance needed for efficient operation during normal conditions
Solution Approach 2:
The heating units are activated in advance during startup and shutdown phases to pre-expand the casing and casing support structure. This preliminary thermal expansion ensures clearance is established before the rotor reaches operating temperature, preventing contact during these critical transition periods
2Reliability
If a large clearance is secured in advance to avoid contact between rotor and casing, then the reliability is improved, but the clearance during rated operation becomes excessive and performance degrades
Solution Approach 1:
The patent implements dynamic clearance management where the heating units are selectively activated only during startup and shutdown phases. During normal rated operation, the heating units remain inactive, maintaining the optimal small clearance for efficient steam flow and minimal energy loss, while providing additional clearance only when needed during transition phases
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 a consistent clearance, optimizing the steam turbine's performance by actively managing thermal expansion and preventing excessive contact or clearance, thus enhancing operational efficiency.
Implementation Method 1
since the magnitude of thermal extension differs between the steam turbine rotor and the steam turbine casing
Implementation Method 2
a second heating unit that is fixed to side surfaces of the flanges of the upper half casing and the lower half casing and that is capable of heating the flanges
Data Source
AI summary
This steam turbine is provided with: a steam turbine rotor which extends in an axial direction; a pair of bearings which support the steam turbine rotor in such a way as to be capable of rotating about the axial direction; a steam turbine casing which encloses the steam turbine rotor between the pair of bearings; a casing support unit which supports the steam turbine casing from below; and a first heating unit which is provided on the casing support unit and which is capable of heating the casing support unit.