Shaft Seal Mechanism With Locking Sections For Thin-Plate Seal Pieces
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Solution Overview
Problem
The conventional shaft seal mechanism for steam and gas turbines is prone to deformation and abrasion due to machining and assembly errors, which affect the gap sizes and pressure distribution, leading to improper lifting force and potential contact with the rotating shaft.
Innovation Solution
The proposed shaft seal mechanism incorporates a ring-shaped seal housing with thin-plate seal pieces forming acute angles and stepped sections, along with high-pressure-side and low-pressure-side plates, which lock the seal pieces from the inside in the radial direction, ensuring stable gap sizes and preventing deformation and abrasion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If gap sizes are preset correctly to generate pressure difference and lifting-up force, then fluid leakage is reduced, but machining error or assembling error causes actual gap sizes to be inappropriate, leading to unstable lifting force and potential contact between seal pieces and rotating shaft
Solution Approach 1:
The seal housing is designed with a movable structure that allows dynamic adjustment of the gap sizes between support members and seal pieces. During rotation, the seal housing moves axially to automatically adjust gap sizes, transforming the static gap dimensioning problem into a dynamic self-adjusting system that compensates for manufacturing and assembly errors
Solution Approach 2:
The patent changes the parameter of gap size from a fixed predetermined value to a dynamically variable parameter. By making gap sizes adjustable through the movable seal housing structure, the system can adapt to different operating conditions and compensate for initial manufacturing tolerances, ensuring stable lifting force generation
2Reliability
If actual gap sizes are smaller than appropriate, then pressing force is applied in opposite direction to lifting-up force, but this causes contact between inner-circumferential-side distal end sections and rotating shaft, leading to abrasion
Solution Approach 1:
The movable seal housing structure enables dynamic adjustment of gap sizes to prevent excessive pressing force. During rotation, the axial movement of the seal housing automatically increases the gaps when needed, preventing the seal pieces from being pressed against the rotating shaft and avoiding abrasion
Solution Approach 2:
The patent implements preliminary anti-action by designing the movable seal housing to preemptively adjust gap sizes before excessive pressing force can occur. The structure anticipates potential harmful pressing forces and counteracts them through automatic gap adjustment, preventing contact between seal pieces and the rotating shaft
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 the thin-plate seal pieces in a noncontact state with the rotating shaft, preventing abrasion and ensuring effective fluid leakage reduction, even under pressing forces, thereby enhancing the seal's durability and operational stability.
Implementation Method 1
the thin-plate seal pieces are bent by pressure difference due to relative positional shift in pressure distribution between the top and bottom surfaces of the thin-plate seal pieces
Implementation Method 2
by dynamic pressure effect of the fluid generated by the rotation of the rotating shaft
Data Source
Figure 1
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AI summary
The purpose of the present invention is to provide a shaft seal mechanism that, even if pressing force is applied to thin-plate seal pieces, can suppress deformation due to the pressing force and prevent abrasion due to contact with a rotating shaft in the thin-plate seal pieces. In order to achieve the foregoing, a shaft seal mechanism (11) that blocks a fluid (G) flowing within a ring-shaped space (14) is equipped with: a ring-shaped seal housing (21) disposed on a fixed section (12); a plurality of thin-plate seal pieces (22) that are secured to the seal housing (21), are in sliding contact with a rotating shaft (13), and are layered in a ring shape; a ring-shaped high-pressure-side plate (25) that forms a high-pressure-side gap (δH) between itself and the seal housing (21); a ring-shaped low-pressure-side plate (26) that forms a low-pressure-side gap (δL) between the seal housing (21) and the thin-plate seal pieces (22); stepped sections (31, 32) that are formed on side edge sections (22c, 22d) of the thin-plate seal pieces (22); and locking sections (25b, 26b) that lock the stepped sections (31, 32).