Optimization Method of Seal Groove Shape Based on Hydrodynamic Pressure Principle

Dynamic pressure seal is widely used in high-speed fluid machinery, and its groove shape is the key factor to determine its steady-state characteristics (such as opening force, film thickness and leakage rate) and dynamic characteristics (such as dynamic stiffness and dynamic damping), and a reasonable groove shape can greatly improve the fluid lubrication performance of the seal end face and ensure the safe and stable long-life operation of dynamic pressure seal. Therefore, the study of groove optimization accounts for a large part of the research on dynamic pressure seals. Groove optimization is mainly divided into amorphous groove research and fixed shape groove research, of which fixed shape optimization research accounts for a large part. This is because it is relatively easy to optimize the study of fixed shape groove patterns, and a large number of studies and experiences have shown that most of the engineering needs can be met by optimizing the widely used fixed shape groove patterns (such as logarithmic spiral grooves, T-shaped grooves, tree grooves, etc.).

In order to improve the fluid lubrication performance of fixed shape dynamic pressure seal, an optimization method of dynamic pressure seal groove type based on the principle of fluid dynamic pressure was proposed: taken the typical parameters of spiral groove sealing performance under constant closure force as the initial value, the number of grooves, groove width ratio, groove dam ratio and spiral angle of dynamic pressure seal spiral groove as the optimization variables, and minimized the ratio of leakage rate to opening force as the optimization objective.

Established a slot optimization model to obtain a series of optimized slot types, and the optimization results showed that the proposed optimization method had good stability for different rotational speeds and optimized number of slots, and the optimized slots were concentrated on two structural parameters A and B, which were 15°, 0.5, 0.55 and 22.5°, 0.55, 0.55 in the order of helix angle β, slot width ratio γ₁ and slot dam ratio γ₂, respectively; further comparison analysis showed that the inner mechanism of the slot optimization process was that by adjusting the helix angle, slot width ratio and slot dam ratio, shifting the peak pressure and homogenizing the circumferential pressure to achieve the goal of reducing the leakage rate by maintaining a high opening force while reducing the fluid transfer in the slot and dam area and lowering the fluid outlet flow rate.

Compared the opening performance of typical spiral groove and A and B groove types, the results showed that in the small film thickness section, the fluid film formation rate was larger, so the typical spiral groove with high film thickness was the preferred groove type, while in the large film thickness section, the B groove with lower leakage rate was the preferred groove type, while the performance of A groove in the full film thickness section was between the two. It was noticeable that differences in performance between the optimized and typical grooves at different rotational speeds were indicative of the important influence of rotational speed on the optimized groove parameters. Obviously, for a given sealing parameter, optimization at the actual working speed could further improve the actual sealing performance. Meanwhile, the sealing performance of a typical spiral groove was not inferior to that of the new groove obtained from optimization, and it was wise to optimize the groove with typical parameters as the initial design for a spiral groove dynamic seal with a given optimization target.