Partial Impeller Groove Design for Mechanical Seal Erosion Control
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Solution Overview
Problem
Conventional mechanical seals with partial impellers experience erosion at the dam portion of the casing, leading to a reduction in the necessary flow rate of cooling fluid, which can be compromised during operation, resulting in inadequate cooling.
Innovation Solution
The design of the partial impeller's groove shape is optimized by controlling specific ratios such as Lgw/Lgd, Lrw/Ldw, nLgw/2πr, and Lgs/Ldl to prevent erosion and ensure a stable flow rate, with the groove shape and placement defined within specific ranges to maintain effective cooling fluid circulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the partial impeller groove tip portion approximately matches the end portion of the groove of the casing, then the necessary cooling fluid flow rate is obtained, but erosion is generated at the dam portion of the casing leading to flow rate reduction
Solution Approach 1:
The partial impeller groove is designed with a curved cross-sectional shape instead of a straight or angular shape. The groove has a rounded bottom and curved sides, which smooths the fluid flow path and prevents turbulent flow patterns that cause cavitation. This curvature modification eliminates the sharp edges and corners where cavitation bubbles form and collapse, thereby preventing erosion at the dam portion while maintaining adequate cooling fluid flow rate.
Solution Approach 2:
The invention modifies the geometric parameters of the partial impeller groove, specifically the cross-sectional shape parameters. By changing from a rectangular or angular cross-section to a curved cross-section with specific radius of curvature, the flow characteristics are improved. This parameter change reduces flow separation and turbulence intensity, preventing cavitation formation and subsequent erosion while preserving the cooling effectiveness.
2Ease of manufacture
If conventional partial impeller groove shapes are used, then manufacturing is simple, but erosion occurs at the dam portion reducing cooling effectiveness
Solution Approach 1:
The curved cross-sectional shape of the partial impeller groove can be manufactured using standard machining operations such as end milling with a rounded tool or wire EDM. The curvature radius is designed to be practical for manufacturing, balancing the erosion prevention benefit with manufacturing simplicity. This approach maintains ease of manufacture while eliminating the erosion problem associated with angular groove shapes.
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 optimized design secures the necessary flow rate for cooling the sliding seal face while preventing erosion, ensuring the mechanical seal's performance over time by maintaining the flow rate and reducing material degradation.
Implementation Method 1
the sealing fluid pressure drastically changes to above vapor pressure from below vapor pressure at the part of the dam of the casing. Thereby, it was speculated that the cavitations is generated at the part where the fluid becomes above vapor pressure, and the cavitations disappears at the part where the fluid is below vapor pressure.
Data Source
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AI summary
Provided is a mechanical seal that ensures the flow rate of a cooling fluid, which is necessary to cool a slide seal surface, and that can prevent erosion from occurring. In the mechanical seal, the ratio between the depth and the width of each groove of a partial impeller is 2.0-5.0; the ratio of the distance between the grooves of the partial impeller to the width of a weir of a casing is 0.5-3.1; the ratio of the total length of the widths of the grooves of the partial impeller to the total length of the peripheral surface of the partial impeller, in which the grooves are formed, is 0.28-0.8; or the ratio of the length of the projected portion of the tip of each groove of the partial impeller to the width of a cooling liquid discharging groove of the casing is greater than 0 and less than or equal to 0.65.