Leakage suppression mechanism of contact mechanical seals under surface wettability effects based on the MRT-LBM

Contacting mechanical seals are ubiquitous in industrial equipment, for which leakage suppression is critical for safety and efficiency. However, traditional macroscopic perspectives often overlook multiphase flow within micro/nano leakage pathways. In particular, wettability’s regulation of leakage behaviour remains unclear, which hinders effective leakage suppression. To address this, a mesoscopic leakage model accounting for surface wettability and gas phases was constructed in this study. This model utilized a GPU-accelerated multi-relaxation-time lattice Boltzmann method (MRT-LBM) combined with real sealing face topographies obtained via laser scanning. The synergistic mechanisms by which the surface wettability, driving pressure, and medium’s viscosity regulated the leakage behaviour were systematically elucidated. The results indicated that wettability regulated leakage in a non-monotonic manner. Moderate hydrophobicity (contact angle of θ ≈ 112°) achieved optimal suppression by forming a capillary barrier. However, when the contact angle increased beyond the optimal value of approximately 112°, the leakage rate exhibited a slight rebound due to the enhanced gas–liquid interface slip. Furthermore, non-linear coupling between the driving pressure and wettability implied that high driving pressures could breach the microscopic capillary barriers. This phenomenon caused leakage conductance on the hydrophobic surfaces to surge by orders of magnitude, shifting the optimal sealing range toward stronger hydrophobicity. Additionally, the medium’s viscosity exerted a rheological reshaping effect on the leakage channel. High-viscosity media suppressed the interface slip observed in low-viscosity conditions through bulk shear, thereby minimizing the leakage conductance on the superhydrophobic surfaces. Finally, the design criteria for sealing the face wettability were defined. For low-viscosity, high-pressure scenarios, superhydrophobic contact angles above 150° should be avoided, and the contact angle is recommended to be controlled within 110°-130°. For high-viscosity conditions, superhydrophobic surfaces are recommended to achieve zero leakage.