Steam Turbine Shell Support Thermal Control
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Solution Overview
Problem
Differential thermal expansion and contraction between the bearing support structure and the shell arm support structure in steam turbines during transient operations lead to radial clearance issues, causing misalignment and potential rubbing between rotor and stator elements, which existing designs struggle to manage effectively without sacrificing performance or leading to wear.
Innovation Solution
A system and method that involve a shell support structure with an interior passageway for flowing a heating or cooling medium, controlled by valves, to match the thermal growth or contraction of the shell support structure with the bearing support structure, using condensate or steam, ensuring controlled thermal expansion and contraction to maintain optimal clearances between the rotor and stator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the bearing support structure and shell arm support structure are exposed to different environmental conditions during transient operations, then the thermal growth rates of these structures differ, but this leads to differential thermal expansion and contraction causing radial clearance issues
Solution Approach 1:
The patent applies parameter changes by introducing a thermal compensation mechanism that actively adjusts the shell support structure's thermal state. A heating/cooling system modifies the temperature parameter of the shell support structure to match the bearing support structure's thermal growth rate, thereby maintaining consistent radial clearances between rotor and stator elements during transient operations
Solution Approach 2:
The patent implements feedback control through thermal sensors that monitor the temperature and thermal growth of both the bearing support structure and shell support structure. The control system uses this feedback information to dynamically adjust the heating or cooling rate of the shell support structure, ensuring its thermal expansion matches that of the bearing support structure, thus preventing radial clearance variations
2Speed
If the bearings heat up rapidly during startup due to oil temperature changes, then the bearing support structure temperature increases quickly, but the shell arm support structure warms up more slowly causing thermal expansion mismatch
Solution Approach 1:
The patent applies preliminary anti-action by implementing a pre-heating system for the shell support structure that activates during startup. This system anticipates the thermal imbalance that would occur naturally and applies counteracting thermal energy to the shell support structure in advance, forcing it to heat at the same rate as the bearing support structure and preventing thermal expansion mismatch before it occurs
Solution Approach 2:
The patent changes the thermal parameter of the shell support structure by introducing controlled heating through embedded heating elements or external heating coils. This actively modifies the temperature parameter to match the bearing support structure's heating rate during startup, ensuring synchronized thermal expansion and preventing radial clearance issues
3Speed
If the bearing support structure cools more rapidly than the shell arm support structure upon shutdown, then thermal contraction rates differ causing changes in radial clearance between rotor and stator
Solution Approach 1:
The patent applies preliminary anti-action during shutdown by implementing a pre-cooling system for the shell support structure. This system anticipates the rapid cooling that will occur in the bearing support structure and applies counteracting thermal energy removal to the shell support structure in advance, forcing it to cool at the same rate and preventing differential thermal contraction that would cause radial clearance instability
Solution Approach 2:
The patent uses feedback control during shutdown by continuously monitoring the temperature differential between the bearing support structure and shell support structure. When the bearing support structure begins to cool rapidly, the control system activates the cooling system for the shell support structure and adjusts its cooling rate based on real-time temperature feedback, ensuring both structures contract at matching rates and maintaining stable radial clearances
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 maintains consistent radial clearances between the rotor and stator during startup and shutdown, reducing wear and maintaining performance by synchronizing thermal expansion and contraction rates, thus preventing misalignment and rubbing.
Implementation Method 1
differential thermal growth of the steam turbine elements, and the support elements... differences in the rate or amount of thermal expansion and contraction of these two elements
Implementation Method 2
the interior passageway is configured to conduct a flow of a heating or cooling medium... selectively supplying a flow of a heating or a cooling medium to an interior passageway of the shell support structure
Data Source
AI summary
Systems and methods for controlling a clearance between a rotor and a stator of a steam turbine during transient operations rely upon heating or cooling a shell support structure of the steam turbine that supports the stator of the steam turbine. Selectively heating or cooling the shell support structure makes it possible for thermal growth/contraction rates and magnitudes of the shell support structure to better match the thermal growth/contraction rates and magnitudes of a bearing support structure of the steam turbine during transient operations. As a result, the clearance between the rotor and the stator of the steam turbine can be maintained.