基于主动压力补偿的高压大尺寸主驱动密封与零泄漏特性研究

Sealing and zero leakage characteristics of a high-pressure large-sized main drive based on active pressure compensation

  • 摘要: 竖井全断面掘进机在掘进作业时可能会穿越富水岩层,其主驱动系统将面临突发涌水导致的高围压载荷冲击,对系统密封可靠性提出了严苛要求. 本文提出基于主动压力补偿的新型主驱动密封方法,结合逾渗理论和统计学接触模型提出零泄漏密封评价方式,建立了微观与宏观尺度密封结构模型,开展了不同补偿压力和外部载荷作用下的水介质密封特性试验研究,揭示了外腔压力与补偿压力共同作用下的密封性能演变机制. 结果表明,考虑接触表面微观形貌对密封的影响,实现零泄漏密封需接触面间发生有效接触,接触应力突破逾渗阈值后开始产生密封效果,且密封能力随接触应力的增加而提高;在较高围压下,新型主驱动密封结构表现出较好密封能力,在补偿压力为7 MPa时密封压力最高可达1.95 MPa;同时,分析显示接触面滑移与基体下沉作用对密封效果影响显著,实践中预先进行压力补偿可以有效提高密封性能.

     

    Abstract: The main drive system of a shaft full-section tunnel boring machine (TBM) may face the impact of a high-pressure mud load caused by sudden water gushing, which imposes strict requirements on the reliability of the system seal. To prevent the possible harm caused by high water pressure confining load to the sealing system, this study proposes a new main drive sealing method based on active pressure compensation, designs a sealing device suitable for the main drive sealing runway, proposes a zero leakage sealing evaluation method combined with percolation theory and a statistical contact model, establishes a micro- and macro-scale finite element sealing structure model, investigates the sealing contact and pressure resistance characteristics under different compensatory pressures and external loads, and reveals the evolution mechanism of sealing performance under the combined action of external cavity pressure and compensatory pressure. The results indicated that effective contact between the contact surfaces was necessary for zero-leakage sealing, considering the influence of the microscopic morphology of the contact surface on the seal. The ratio of the contact area of the sealing surface to the total area is called the contact area ratio, while the ratio of the effective connected area on both sides of the contact surface to the total area is called the effective connectivity ratio. The contact area ratio corresponding to an effective connectivity ratio of 0 is called the percolation threshold. When the contact area ratio of the sealing contact stress exceeded the percolation threshold or the effective connectivity ratio dropped to zero, a sealing effect arose. The sealing ability gradually increased with the contact stress, which gradually weakened the influence of the surface topography on the sealing. The deformation of the sealing matrix caused by the external pressure gradually became the dominant factor affecting the sealing performance. When the compensation pressure was 0, the sealing pressure was lower than 0.1 MPa, and the sealing contact surface was matched with a gap. This lowered both friction and wear under the dynamic working states of normal and low pressures and extended the service life of the seal. In practice, the effective and timely removal of impurities entering the interior sealed space was achieved by utilizing the pressure difference between the internal sealing grease and exterior. Under a higher confining pressure, the new main drive seal structure exhibited better sealing ability, and under the pre-compensation mode, the sealing pressure reached 1.95 MPa at a compensation pressure of 7 MPa. Compared to the follow-compensation mode, the pre-compensation pressure effectively improved the sealing performance under low confining pressures. Simultaneously, a comparative analysis between the macro simulation results and pressure resistance test data showed that lower external pressure promoted the sealing contact stress and improved the sealing pressure under low confining pressure, whereas higher external pressure significantly affected the sealing effect of contact surface slip and matrix subsidence. Therefore, the effect of the external pressure on the matrix deformation should be considerably reduced to improve the effective sealing pressure at high confining pressures.

     

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