Helical Trochoidal Rotor Sealing for Leakage and Wear Control
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Solution Overview
Problem
Rotary machines with trochoidal geometries face challenges in sealing and reducing fluid leakage between the rotor and stator, particularly due to the continuous contact path and potential for wear and thermal expansion issues, which affect their efficiency and durability.
Innovation Solution
The implementation of helical seals mounted on the rotor and stator, designed to match the continuous contact path and offset geometry, reduces leakage by providing a secure and resilient sealing mechanism that accommodates thermal expansion and wear, enhancing the operational efficiency and durability of the machines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If close running clearances are used between rotor and stator, then sealing effectiveness is improved, but wear and thermal expansion issues worsen
Solution Approach 1:
The seal is divided into multiple segments or lips that can independently deflect and adapt to the rotor surface. This segmentation allows the seal to maintain close clearance for effective sealing while the individual segments can accommodate thermal expansion and wear without compromising the overall sealing performance or causing excessive wear on the rotor surface.
Solution Approach 2:
The seal material properties are selected to have low friction coefficients and high thermal stability. The seal design incorporates compliance that allows it to deflect and maintain contact pressure within optimal ranges despite thermal expansion. The geometry parameters of the seal (such as lip angle, thickness, and deflection characteristics) are optimized to balance sealing effectiveness with wear resistance.
2Reliability
If continuous contact path is provided between rotor and stator, then sealing is improved, but friction and wear increase
Solution Approach 1:
The seal utilizes a flexible lip or shell structure that can deflect and conform to the rotor surface. This flexible design maintains continuous contact for effective sealing while the small contact area and flexible nature reduce friction compared to rigid continuous contact. The flexible material allows for smooth sliding motion that minimizes wear.
Solution Approach 2:
The seal geometry parameters are optimized to achieve the right balance between contact area and sealing effectiveness. The lip angle, thickness, and material properties are selected to provide sufficient contact pressure for sealing while minimizing the contact area and friction. The compliance of the seal allows it to adapt to surface irregularities without requiring high contact pressures.
3Loss of substance
If helical seals are mounted on rotor and stator, then leakage is reduced, but device complexity increases
Solution Approach 1:
The seal incorporates helical or curved geometry that matches the trochoidal motion path of the rotor. This curved design allows the seal to maintain continuous contact with the rotor surface throughout the planetary motion, effectively reducing leakage. The helical shape is integrated into the seal structure rather than being a separate component, which helps manage complexity.
Solution Approach 2:
The seal design is intended to be adaptable to different trochoidal machine configurations and sizes. The helical geometry and mounting approach are designed to be universally applicable across various rotor-stator arrangements, reducing the need for custom-designed seals for each application and thereby managing complexity through standardization.
Data Source
AI summary
Sealing in rotary positive displacement machines based on trochoidal geometry that comprise a helical rotor that undergoes planetary motion within a helical stator is described. Seals can be mounted on the rotor, the stator, or both. The rotor can have a hypotrochoidal cross-section, with the corresponding stator cavity profile being the outer envelope of the rotor as it undergoes planetary motion, or the stator cavity can have an epitrochoidal cross-section with the corresponding rotor profile being the inner envelope of the trochoid as it undergoes planetary motion. In some embodiments, the geometry is offset in a manner that provides advantages with respect to sealing in the rotary machine. In multi-stage embodiments, the rotor-stator geometry remains substantially constant or varies along the axis of the rotary machine.