深海装备极端环境下高参数机械密封热动力学特性及失效机理研究

Mechanical seal technology in underwater robot has become one of the essential and key elements in reliable ocean development in which underwater robot is an important equipment. Particularity and complexity of extreme environments in deep ocean increase the performance requirements of mechanical seal. Mechanical seal needs to consider not only the complicated multi-field coupling, but also the special thermodynamic characteristics and sealing performances under the action of deep-ocean currents. However, the traditional design method cannot achieve the desired results. It is urgent to develop the high-performance mechanical seal device for improvement. This project uses the method of combining theoretical analysis, numerical simulation and experimental measurement as the main means to make the development. It considers the thermal-fluid-solid-force coupled effects, fluid flow patterns, microorganism erosion, etc., and build the multi-field coupling unified numerical model of high-performance mechanical seal in deep ocean environment. By the coupling model, the friction behaviors, thermodynamic characteristics and sealing performances in an extremely unstable state are established. From these results, the failure mechanism of high-performance mechanical seal in deep ocean environment is analyzed and revealed, and the effective design method of high-performance mechanical seal during the extremely unstable operation in deep ocean environment based on thermodynamic characteristics is explored. It is important for improving the dynamic design system of mechanical seal, the sealing performance and reliability of underwater robot in deep ocean environment.

水下机器人作为重要的海洋开发装备，其机械密封技术已成为保证海洋开发可靠进行的必备关键要素之一。深海极端环境的特殊性和复杂性提高了对机械密封装置性能的要求，机械密封不仅需要考虑复杂的多场耦合效应，还需考虑深海洋流作用下特有的热动力学瞬态特性和动态密封性能，传统的设计方法已无法达到理想的使用效果，迫切需要高参数机械密封装置来提高其性能。本项目以理论分析、数值模拟和试验研究相结合为主要手段，考虑机械密封热-流-固-力多场耦合效应，结合深海流体流态、微生物侵蚀等影响，建立深海高参数机械密封多场耦合统一数值模型，掌握其极端不稳定条件下摩擦情况、热动力学特性及对密封性能的影响规律，分析并揭示深海高参数机械密封失效机理，探究基于热动力学特性的深海高参数极端不稳定条件下机械密封有效设计方法，对完善机械密封动态设计体系，提高深海高参数机械密封性能和水下机器人装备可靠性具有重要意义。

机械密封作为深海装备不可缺少的密封装置，在其稳定运行中发挥着关键作用。随着深海密封工况的变化以及洋流扰动和微生物侵蚀的作用，机械密封端面性能逐步恶化，因热力学问题而出现泄漏的情况很多。深海环境的特殊性和复杂性不仅需要考虑复杂的耦合效应，还需考虑洋流作用下的热动力学瞬态特性，迫切需要高参数机械密封来提高其性能。. 本项目以机械密封为对象，根据深海高参数密封结构及间隙内液膜的流动理论及特性参数，首先应用数值方法建立了密封体与液膜相互作用的多场耦合模型，研究了稳态下密封端面的热力变形特性及对密封性能的影响规律，探究了不同密封工况下的端面压力和温度分布，分析了端面耦合特性，确定了其对密封性能的影响规律。其次，基于耦合模型研究了洋流扰动下的端面热动力学响应，分析了其对端面特性的影响，揭示了洋流扰动下密封性能的影响规律及失效机理。再次，探究了深海微生物侵蚀的影响因素及研究方法，基于密封环端面特性，初步提出了深海环境微生物腐蚀的防腐设计措施。最后，开展了高参数机械密封试验平台的设计与搭建，进行了不同工况下机械密封端面特性及密封性能的测试研究。结果表明：1）稳态工况下，在耦合效应下密封端面的最大变形发生在静环上，且随着转速、压力的增大，端面温度、接触压力、泄漏量和摩擦扭矩也逐渐增大；2）交变洋流载荷作用下，端面密封特性等呈现出交变的瞬态特征；3）高水深压力可增大端面温升，加剧腐蚀速度和端面磨损，降低摩擦副材料的耐蚀性能和密封稳定性；4）在不同密封工况下，随着转速和压力的增大，端面温升幅度也随之增大，且循环流量的增加，对防止端面液膜汽化或热裂的发生产生了积极效果，但循环流量并非越大越好，应合理选择；5）密封环外周表面织构增强了对流换热效果，提升了密封性能，且端面织构有助于减小端面摩擦和温升。本研究对完善机械密封动态设计体系，提高深海机械密封性能和水下装备运行可靠性具有重要意义和应用价值。