Comprehensive Optimization of Textured Compliant Foil Face Gas Seal Performance

Dry gas seal is widely used in centrifugal compressors, pumps, fans, and other high-speed rotating equipment due to its advantages of low friction, minimal leakage, and extended operational lifespan.However, with the advancement of rotating machinery towards higher-speed conditions, intense shaft vibration can lead to grinding or crushing failures of the dry gas seal's rigid surface. Therefore, developing a novel dry gas seal structure capable of accommodating severe shaft vibration is of significant importance. To address this, foreign scholars have developed a flexible-end compliant foil face gas seal (CFFGS), drawing upon the design principles of foil bearings. Compared to traditional rigid-end dry gas seals, the CFFGS with a flexible surface exhibits clear adaptability and impact resistance. However, it does not demonstrate significant advantages in terms of opening force, gas film stiffness, and leakage rate. Enhancing these aspects while ensuring the adaptive capability of CFFGS has become a crucial focus in its application research. Additionally, incorporating hole textures on the seal end face is recognized as a critical approach to enhancing hydrodynamic lubrication performance. Super-elliptic curves can describe the boundaries of sealed interface-type holes structures, allowing for continuous shape evolution by adjusting the super-elliptic coefficients. Nonetheless, scholarly investigations into seal hole texture predominantly focus on traditional rigid surface hydrodynamic pressure seals, with relatively limited attention given to research on foil seals.

In order to improve the comprehensive performance of CFFGS, a novel super-elliptical hole floating seal dam compliant foil face gas seal (SHFSD-CFFGS) was proposed. By opening super-elliptical hole textures in the foil area, the opening force and the gas film stiffness were improved by the effect of secondary dynamic pressure. Additionally, the compliant foil support was designed at the bottom of the sealing dam to reinforce its adaptability, and the leakage control performance was improved by the double-row inclined super-elliptical hole textures on the surface. Based on the theories of gas lubrication and elastic mechanics, a theoretical model of SHFSD-CFFGS aeroelastic coupling lubricationis established. The study explored the influence of the hole texture shape, inclination, slender ratio, and depth of the floating dam area on the seal performance and conducted an optimization design for the compliant coefficients of the foil and dam area. The results showed that the super-elliptical textured foil face structure reduced the leakage rate while enhancing the foil seal’s opening force and gas film stiffness. Within the scope of parameters research in this paper, when the super-elliptical coefficient n₂ was set to 1, the inner and outer hole inclination angles θ₁ and θ₂ were set to 40°, the super-elliptical texture major axis a₂ was 1.75 mm, the minor axis b₂ was 0.7 mm, the texture depth T_d2 was 6 μm, the compliance coefficient of foil area α₁ was set to 0.005~0.01, and the compliance coefficient of floating seal dam area α₂ varied from 1×10⁻⁵ to 1×10⁻⁴, the SHFSD-CFFGS exhibited superior comprehensive sealing performance.