关键词: 机械密封, 汽化, 流体动压, 密封性能, 多目标优化

Abstract: For the issues of liquid film vaporization in the diffuser self-pumping mechanical seals, a fluid film vaporization calculation model was established based on the Mixture two-phase flow model, viscosity-temperature equation, saturation vapor pressure-temperature relationship. The main regions and reasons were investigated for the phase transition of the liquid films between the sealing interfaces under medium and high temperature conditions. Through uniform experimentation and the NSGA-Ⅱ algorithm, the optimal sealing face structural parameters were obtained at a temperature of 393 K. The results show that phase transition mainly occurs on the inner diameter side of the sealing faces and the diffuser grooves. As the temperature of the medium increases, the vapor phase volume fraction increases and the viscosity of the medium decreases, the pumping effect weakens, and both the areas of the high and low pressure regions decrease. Under the premise of ensuring the stable operations of the seals, the optimal solution of the ratio of stiffness to leakage is as 257.17  GN·h/(m·L), and the sealing face structural parameters of helix angle β, sealing dam length wd, spiral groove length wg, spiral groove depth hg and diffuser groove width wk are as 34.4°, 5.2 mm, 8.9 mm, 43.3 μm and 5 mm respectively. These research results provide guidance for the optimization of sealing face structure design, control of liquid film phase transition, and enhancement of the sealing performance of the diffuser self-pumping mechanical seals.

Key words: mechanical seal, vaporization, fluid dynamic pressure, sealing performance, multi-objective optimization