Mechanical Seal Sliding Faces With Variable Land Width
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing sliding parts for mechanical seals face limitations in maintaining sealing function while minimizing positive pressure regions to enhance negative pressure generation and reduce fluid leakage, as the ratio between negative and positive pressure regions is fixed, limiting the sealing performance.
Innovation Solution
Adjusting the ratio of the circumferential length of the land section to the negative pressure generation groove in the radial direction, allowing for a larger land section on the outer diameter side and a smaller one on the inner diameter side, without reducing the negative pressure generation force, to decrease the positive pressure region and improve sealing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the land width is increased to ensure negative pressure generation force, then the sealing property is improved, but the positive pressure region increases which limits further sealing improvement
Solution Approach 1:
The patent applies local quality by making the land width variable in the radial direction rather than uniform. Specifically, the land width is set to be larger on the outer diameter side and smaller on the inner diameter side of the sealing face. This allows the negative pressure generation mechanism to be optimized at different radial positions, maximizing sealing effectiveness while minimizing the overall positive pressure region area.
Solution Approach 2:
The patent introduces dynamic characteristics by making the land width change continuously or stepwise in the radial direction. This dynamic variation allows the sealing structure to adapt to different pressure and flow conditions across the sealing face, optimizing both negative pressure generation and minimizing positive pressure region occupancy.
2Reliability
If the negative pressure region is expanded to improve sealing, then more area is covered with grooves, but the land width must be maintained which limits the expansion
Solution Approach 1:
The patent segments the sealing face into different radial zones with different land width characteristics. By dividing the sealing face into an inner diameter region and an outer diameter region with different land width proportions, the patent enables independent optimization of negative pressure generation in each zone without requiring a completely complex groove pattern across the entire surface.
3Ease of manufacture
If the land width ratio is kept fixed to simplify design, then manufacturing is easier, but sealing performance is limited
Solution Approach 1:
The patent changes the geometric parameter of land width from a fixed value to a variable parameter that changes in the radial direction. This parameter change allows the sealing structure to achieve superior performance by optimizing the land width at different radial positions, while still maintaining manufacturability through systematic design approaches.
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 adjustment enhances the sealing property by increasing negative pressure generation and reducing the region without negative pressure grooves, thereby improving the mechanical seal's performance and preventing fluid leakage while maintaining effective lubrication.
Implementation Method 1
a groove section 23a of a reversed Rayleigh step mechanism 23 that forms a negative pressure generation mechanism is provided on a low pressure side of a sealing face 21-2
Implementation Method 2
pressure gradient of a part 25 (part surrounded by a broken line) of the groove section 23a on the inner peripheral side is reversed to make a negative pressure region
Implementation Method 3
a groove section 22a of a Rayleigh step mechanism 22 that forms a positive pressure generation mechanism is provided on a high pressure side of a sealing face 21-1
Implementation Method 4
the sliding parts that are actuated with fluid lubrication in a rotating state including an initial stage of rotation while leakage is prevented, so that sealing and lubrication can be realized at the same time
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Sliding parts by which a sealing function of sealing faces can be maintained by changing a ratio between a negative pressure region and a positive pressure region in the radial direction of the sealing faces and decreasing the positive pressure region while ensuring negative pressure generation force are provided. Sliding parts of a pair of annular bodies including sealing faces that relatively slide on each other are characterized in that a reversed Rayleigh step mechanism 10 serving as a negative pressure generation mechanism is provided in at least one of the sealing faces, a negative pressure generation groove 10a that forms the reversed Rayleigh step mechanism 10 is provided in an arc shape along the circumferential direction of the sealing face so as to be isolated from a high pressure fluid side and a low pressure fluid side by a land section R, an upstream side end 10b and a downstream side end 10c of the negative pressure generation groove 10a are isolated from each other by the land section R, the downstream side end 10c communicates with the high pressure fluid side via a deep groove 11, and a ratio x = b/a between circumferential length a of the negative pressure generation groove 10a and circumferential length b of the land section R between the upstream side end of the negative pressure generation groove and the deep groove 11 is set to be different in the radial direction.