Turbopump Sealing System with Kinematic Joints
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Solution Overview
Problem
Conventional sealing systems for turbopumps face challenges in maintaining dynamic sealing between the rotary shaft and its support, particularly due to the disturbance caused by antirotation pegs, leading to issues like loss of floatability, tilting, premature wear, and instability, especially when the shaft is subjected to high-speed vibrations.
Innovation Solution
A sealing system that incorporates a coupling part between the floating ring and the support, utilizing first and second kinematic joints allowing cylindrical relative movements in transverse directions, decoupling the components' movements and preventing rotation about the longitudinal axis, thus enabling effective dynamic sealing while allowing the ring to follow transverse movements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If antirotation pegs are used to prevent ring rotation, then rotation prevention is achieved, but the ring's floatability is disturbed and stability is reduced
Solution Approach 1:
The antirotation mechanism is segmented into multiple discrete pegs distributed around the ring's circumference, each contributing to the overall antirotation effect while minimizing individual interference with ring floatability. This segmentation allows the ring to maintain stability while preventing rotation.
Solution Approach 2:
The antirotation pegs are strategically positioned at specific locations around the ring where they provide maximum antirotation effect with minimum interference to the ring's floating operation. The local geometry and positioning of pegs are optimized to distinguish between desirable transverse movement following and undesirable rotation.
2Reliability
If the ring is made to follow transverse movements closely, then sealing effectiveness is improved, but contact with the shaft increases causing wear
Solution Approach 1:
The ring is designed to follow transverse movements to an optimal degree that provides sufficient sealing effectiveness without excessive contact with the shaft. The clearance and geometric parameters are tuned to achieve partial following action that balances sealing performance with wear prevention.
Solution Approach 2:
The geometric parameters of the ring, including clearance dimensions, surface finish, and material properties, are optimized to control the degree of contact with the shaft during transverse movements. These parameter changes enable the ring to follow movements effectively while minimizing wear through controlled lubrication and reduced friction.
3Reliability
If the ring is constrained to prevent rotation, then antirotation is achieved, but the ability to float freely is reduced
Solution Approach 1:
The antirotation mechanism employs dynamic pegs that can adapt their engagement with the support structure based on operational conditions. During normal floating operation, the pegs remain disengaged allowing free floatability, while under rotational tendency, the pegs engage to prevent rotation. This dynamic behavior resolves the contradiction between antirotation capability and floatability.
Solution Approach 2:
The antirotation pegs act as intermediary elements between the ring and the support structure, providing rotation prevention only when necessary without continuously constraining the ring's floating motion. The pegs mediate between the conflicting requirements of free floatability and rotation prevention by engaging only during rotational tendencies.
Data Source
AI summary
A sealing system for at least one floatingly mounted ring in a support for a rotary shaft rotatable about an axis directed along a longitudinal direction provides dynamic sealing between the shaft and the support. The system includes a coupling part interposed between the ring and the support, whereby the ring is secured to the support. A first cylindrical type joint directed with respect to a first transverse direction provides a joint between the support and the coupling part. A second cylindrical type joint directed with respect to a second transverse direction perpendicular to the first transverse direction provides a joint between the ring and the coupling part. A turbopump includes such rotary shafts and sealing systems.