超临界态二氧化碳梳齿密封泄漏特性数值研究

Numerical Investigation on Flow Characteristics of Supercritical CO₂ Labyrinth Seals

密封技术是一项关系到超临界二氧化碳(Supercritical carbon dioxide, S-CO2)核动力力系统中旋转机械能否高效、安全、可靠运行的关键技术。为尽可能地减小密封泄漏,使用数值计算的手段研究了超临界二氧化碳直通式梳齿密封的泄漏特性。首先,对密封的泄漏量进行无量纲化以便后续描述密封的泄漏特性。随后,研究了密封上下游滞止工况以及密封几何参数对密封泄漏的影响。计算结果显示:温度及压力等热力学参数对密封的无量纲泄漏量影响较小;减小密封间隙,增加密封腔长,减小密封齿宽均会改善密封泄漏性能;齿高对密封泄漏的影响是非线性的,存在最优值,该最优值在齿高比腔长约为0.13时出现;增加齿数同样可以减小密封泄漏量,但这一点无法反映在无量纲化后的泄漏量上。本文的研究表明:本文采用的无量纲泄漏量可以比较准确地反映密封结构和泄漏之间的关系;除了传统的梳齿密封所使用的减小密封泄漏的手段之外,对于结构紧凑的超临界二氧化碳梳齿密封来说,优化密封腔室结构,调整齿高也可以有效降低密封泄漏。

Sealing technology is a key technology related to the efficient, safe, and reliable operation of rotating machinery in supercritical carbon dioxidenuclear power systems. In order to reduce the seal leakage, the characteristics of the supercritical carbon dioxide see-through labyrinth seals are studied numerically. Firstly, a nondimensional leakage rate is used to describe the leakage characteristics of the seal. Then, the influence of the upstream and downstream conditions and the geometrical parameters on the seals’ leakage is studied. The results show that the thermodynamic parameters such as temperature and pressure have little influence on the nondimensional leakage rate. Reducing the sealing clearance, increasing the cavity length and decreasing the tooth width can improve the sealing leakage performance. The effect of tooth height on seal leakage is nonlinear, and there is an optimal value, which appears when the ratio of tooth height to cavity length is about 0.13. Increasing the number of teeth can also reduce the sealing leakage, but this didn’t be reflected in the nondimensional leakage rate. The calculation results show that the dimensionless leakage rate in this paper can accurately reflect the relationship between seal geometry and leakage. In addition to the methods of reducing the seal leakage by the traditional labyrinth seal, for the compact supercritical carbon dioxide labyrinth seal, optimizing the structure of the seal cavity and adjusting the tooth height can also effectively reduce the seal leakage.