Reverse Trapezoidal Face Pattern for Bidirectional Mechanical Seal Lift
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Solution Overview
Problem
Existing mechanical seal designs with bidirectional operation face challenges in maintaining lift and preventing face contact during pressure reversals, leading to potential damage and failure, especially in applications where pressure conditions change.
Innovation Solution
A reverse trapezoidal face pattern with a sinusoidal depth profile is implemented on mechanical seals, which provides improved hydrodynamic lift and film stiffness, allowing for stable separation of seal faces and reduced fluid recirculation, thereby maintaining lift in both normal and reversed pressure directions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional bidirectional seal face patterns are used, then the seal can operate in both rotation directions, but film stiffness is insufficient and face contact occurs during pressure reversals
Solution Approach 1:
The seal face pattern uses asymmetric reverse trapezoidal grooves with specific orientation angles (e.g., 15-45 degrees) rather than symmetric patterns. This asymmetric geometry creates directional hydrodynamic lift that maintains film stiffness during pressure reversals while allowing bidirectional rotation, preventing face contact that plagues conventional symmetric bidirectional patterns
Solution Approach 2:
The invention inverts the conventional approach by using reverse trapezoidal grooves where the wider portion faces the direction of fluid supply rather than the discharge direction. This inverted geometry reverses the typical flow pattern and creates positive hydrodynamic lift during pressure reversals, maintaining seal face separation when conventional patterns fail
2Reliability
If shallow grooves are provided on seal faces to generate hydrodynamic lifting forces, then fluid film forms to lubricate and reduce wear, but face contact still occurs during pressure reversals leading to potential damage
Solution Approach 1:
The reverse trapezoidal groove geometry is designed to generate preliminary hydrodynamic lift that counteracts closing forces before face contact can occur during pressure reversals. The asymmetric groove shape creates positive pressure build-up in advance, preventing the harmful face contact that would otherwise occur during transient pressure conditions
Solution Approach 2:
The invention changes the geometric parameters of the groove pattern, specifically using reverse trapezoidal shapes with controlled depth, width, and orientation angles. These parameter changes optimize the hydrodynamic lift generation to maintain adequate film thickness during pressure reversals, preventing face contact while preserving lubrication benefits
3Loss of substance
If the seal faces are provided with grooves or recesses to pump fluid film toward sealed fluid, then leakage is reduced, but film stiffness decreases allowing face contact during pressure reversals
Solution Approach 1:
The reverse trapezoidal groove pattern creates local variations in film thickness and pressure distribution across the seal face. The asymmetric geometry generates localized hydrodynamic lift zones that maintain film stiffness in critical areas during pressure reversals, while still providing adequate pumping action to reduce overall fluid leakage
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
The reverse trapezoidal face pattern enhances film stiffness and lift performance, preventing face contact and damage during pressure reversals, ensuring consistent operation and extended seal life by maintaining a controlled gap under varying pressure conditions.
Implementation Method 1
the seal faces typically separate a small distance wherein a thin film of fluid forms between the seal faces to lubricate the seal faces and reduce wear therebetween
Implementation Method 2
Hydrostatic load support is created through the manipulation of the fluid pressures acting between the seal faces
Implementation Method 3
Hydrodynamic load support is created through the active compression of the fluid between the seal faces due to movement of the fluid from a wide gap to a narrower gap
Data Source
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AI summary
An improved mechanical face seal is provided which includes a pair of relatively rotatable seal rings having opposing seal faces. At least one of the seal faces (72) includes a reverse trapezoidal face pattern (75) having a sine wave depth profile wherein individual face features are circumferentially spaced over the seal face (72). The reverse trapezoidal face pattern (75) serves to generate a hydrodynamic lift which provides a stable separation of the seal faces that permits formation of a fluid film between the seal faces. The individual trapezoidal grooves (76) have a sinusoidal or similarly shaped depth profile wherein the trapezoid shape is arranged with the narrower edge (78) communicating with the high pressure side of the seal, and the wider edge (79) forms a circumferential dam region (81) towards the low pressure side of the seal. Alternatively, the reverse trapezoidal face pattern may also be provided as a primary face pattern on a dry gas seal in combination with a secondary face pattern wherein the faces operate with a controlled gap under normal pressure conditions as well as when the pressure direction across the seal face is reversed.