Grid Valve Assembly Actuation at High Pressure Differentials
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Solution Overview
Problem
Conventional grid valve assemblies in multi-stage steam turbines face challenges in actuating effectively at high pressure differentials due to increased frictional forces, which conventional actuators cannot overcome, limiting their utility.
Innovation Solution
A grid valve assembly design featuring an annular stationary member and a rotatable member with radially extending openings, where the rotatable member is configured to rotate about the stationary member to control steam flow between stages, and includes features like flanges, lips, and sealing substrates to minimize leakage and friction, allowing for actuation even at high pressure differentials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the pressure differential between upstream and downstream stages is increased, then the energy extraction capability of the steam turbine is improved, but the frictional forces acting on the grid valve assembly increase, making actuation difficult or impossible with conventional actuators
Solution Approach 1:
A bearing assembly is introduced as an intermediary component between the rotatable plate and the stationary plate. The bearing assembly includes a bearing outer race coupled to the stationary plate and a bearing inner race coupled to the rotatable plate, with bearing balls rolling between the races. This intermediary bearing mechanism mediates the interaction between the two plates, enabling smooth rotation of the rotatable plate even under high pressure differentials by replacing sliding friction with rolling friction.
2Device complexity
If the grid valve assembly is designed with conventional sliding contact between plates, then the structure is simple, but the frictional forces prevent effective actuation at high pressure differentials
Solution Approach 1:
The conventional sliding contact mechanical system between the rotatable plate and stationary plate is replaced with a bearing-based rolling contact system. The bearing assembly substitutes the direct sliding friction mechanism with a rolling element bearing mechanism, where bearing balls roll between the inner and outer races, significantly reducing friction and enabling reliable actuation under high pressure differentials.
3Device complexity
If conventional actuators are used to operate the grid valve assembly, then the device complexity is low, but the actuators cannot provide sufficient force to overcome friction at high pressure differentials
Solution Approach 1:
The bearing assembly serves as a mechanical intermediary that reduces the frictional resistance between the rotatable plate and stationary plate. By introducing rolling element bearings, the system reduces the actuating force requirement, allowing conventional actuators to effectively operate the grid valve assembly even under high pressure differentials where sliding friction would otherwise prevent actuation.
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 reliable actuation of the grid valve assembly at high pressure differentials by minimizing net biasing forces and friction, ensuring consistent operation across varying steam pressures.
Implementation Method 1
a bearing assembly disposed between the rotatable member and the stationary member and including a bearing outer race coupled to the stationary member, a bearing inner race coupled to the rotatable member, and a plurality of bearing balls rolling between the bearing inner race and the bearing outer race
Data Source
AI summary
A grid valve assembly for a steam turbine is provided. The grid valve assembly may include an annular stationary member disposed between an upstream stage and a downstream stage of the steam turbine. The annular stationary member may define a plurality of stationary member openings extending radially therethrough from an outer circumferential surface to an inner circumferential surface thereof. The grid valve assembly may also include an annular rotatable member rotatably disposed about the outer circumferential surface of the annular stationary member. The annular rotatable member may define a plurality of rotatable member openings extending radially therethrough.