Steam Turbine Outer Casing Clearance Control via Exhaust Steam
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Solution Overview
Problem
In steam turbines, the gap between the rotor and inner casing, or between the stator vane and rotor, can inadvertently narrow due to operational conditions, affecting performance.
Innovation Solution
A steam turbine design with independently controllable upper and lower valves in the outer casing, allowing for the adjustment of exhaust steam flow to promote deformation and set appropriate clearance between the rotor and inner casing based on temperature thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the steam turbine operates under certain conditions, then the steam flow rate increases, but the gap between the rotor and inner casing inadvertently narrows
Solution Approach 1:
The patent changes the temperature parameter of the outer casing by introducing exhaust steam through upper and lower discharge ports. This thermal parameter change causes the outer casing to expand or contract, thereby adjusting the gap between the rotor and inner casing to maintain appropriate clearance during high steam flow rate operations
Solution Approach 2:
The patent utilizes thermal expansion of the outer casing by heating it with exhaust steam. When exhaust steam is introduced through the discharge ports, the outer casing expands thermally, which increases the gap between the rotor and inner casing, preventing inadvertent narrowing during high productivity operations
2Productivity
If the gap between rotor and inner casing is increased, then the steam flow path is maintained, but the structural compactness is reduced
Solution Approach 1:
The patent makes the outer casing dynamically adjustable by introducing exhaust steam through controllable discharge ports. The gap between the rotor and inner casing can be dynamically increased when needed for steam flow path maintenance, while the structure remains compact when the discharge ports are closed and the outer casing returns to its original state
3Manufacturing precision
If exhaust steam is introduced to deform the outer casing, then the clearance is adjusted, but the system complexity increases
Solution Approach 1:
The patent uses exhaust steam that would otherwise be wasted as a resource to achieve clearance adjustment. The system serves dual purposes: disposing of exhaust steam and adjusting the outer casing deformation to maintain appropriate clearance, thereby reducing the need for additional complex control systems
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
Enables precise control of the clearance between the rotor and inner casing, improving operational efficiency and preventing unintended narrowing of gaps.
Implementation Method 1
By causing more exhaust steam having a high temperature or a low temperature to flow to the upper portion or the lower portion of the outer casing depending on an operation condition the steam turbine, it is possible to promote deformation of the outer casing and set a clearance between the rotor and the inner casing to an appropriate value
Data Source
AI summary
A steam turbine includes an inner casing which has an inner casing body in which a first main flow path to which steam is to be supplied from an inner introduction port is defined, an outer casing which has an outer casing body which defines a second main flow path between the inner casing body and the outer casing body and an upper discharge port and a lower discharge port which are in the outer casing body and through which exhaust steam is to be discharged, an upper valve and a lower valve configured to adjust a flow rate of the exhaust steam which has been discharged, and a control unit which can independently control the upper valve and the lower valve.