Abstract:

The lubrication film thickness developed between the two faces in a mechanical seal normally ranges in size from 1 to 15 μm.Therefore the influence of the surface tension of sealing medium cannot be ignored.In this paper a study of sealing ability of a laser-textured surface mechanical seal(LST-MS)with hydrophobic surface located at the inner radius was performed.The geometrical models of hydrophobic surface with nano-columns or nano-pores were presented, and their self-sealing ability was theoretically proved.The Reynolds equation for controlling film pressure between the two faces of such a LST-MS was solved by using the finite element method.The effects of surface tension coefficients of the sealing medium on film stiffness, opening force and leakage rate were studied at different rotational speeds and sealing pressures.It was proved theoretically that such a LST-MS could get zero-leakage under specific conditions.The results showed that when the LST-MS operated at the rotational speeds lower than 100 r·min^-1 and low fluid pressure ratios lower than 2, film stiffness and opening force were kept high while leakage was substantially decreased.The film thickness fluctuation would take place due to external perturbation, but leakage would be controlled by using barrier fluids or flushing fluids with high surface tension coefficients.The width ratio of hydrophobic face to seal face was optimized in the range from 0.01 to 0.10.

Key words: FONT-SIZE: 10.5pt, mso-ascii-font-family: Times New Roman, mso-bidi-font-family: Times New Roman, mso-font-kerning: 1.0pt, mso-ansi-language: EN-US, mso-fareast-language: ZH-CN, mso-bidi-language: AR-SA, mso-hansi-font-family: Times New Roman">机械密封；微孔端面；疏水型面；自密封；液体表面张力系数

摘要：

液体润滑机械密封正常运行时，端面间的膜厚一般为1～15 μm，液体表面张力对密封性能的影响不可忽略。本文以激光加工多孔端面机械密封（LST-MS）为研究对象，提出了疏水型面的几何结构模型，从理论上证明了疏水型面的自密封性；采用有限元方法求解雷诺方程，分析了密封介质表面张力系数在不同转速、不同介质压力等操作条件下对端面液膜刚度、开启力和泄漏率的影响规律，指出了润湿性对密封性能影响的重要性，并从理论上证明采用疏水型面的LST-MS完全可以实现零泄漏。结果表明，在转速n≤100 r·min^-1、介质压比P_o≤2的低速、低压工况条件下，采用疏水型面的LST-MS在保持高液膜刚度和开启力的同时，可使泄漏率大幅度降低；在端面发生轴向振动导致液膜厚度较大时，仍然可以使用具有高值表面张力系数的封液或冲洗液控制泄漏率；疏水型面宽度比γ的取值范围为：0.01≤γ≤0.10。

关键词: FONT-SIZE: 10.5pt, mso-ascii-font-family: Times New Roman, mso-bidi-font-family: Times New Roman, mso-font-kerning: 1.0pt, mso-ansi-language: EN-US, mso-fareast-language: ZH-CN, mso-bidi-language: AR-SA, mso-hansi-font-family: Times New Roman">机械密封；微孔端面；疏水型面；自密封；液体表面张力系数