Abstract Based on the basic principles of thermodynamics and fluid mechanics, the temperature and pressure model of natural gas hydrate hydraulic lifting pipeline, the hydrate decomposition mass transfer model and the mathematical model of pipeline multiphase flow are established. The relationship between the back pressure of the pipeline outlet, the decomposition surface and the depth of the seawater was analyzed. On this basis, the numerical simulation and experimental verification of natural gas hydrate pipeline transmission were carried out. The effects of pipe diameter, inlet velocity and solid phase parameters on the three-phase flow of natural gas hydrate pipelines were analyzed. The result shows that with the outlet pressure increasing, the position at which the hydrate begins to decompose moves up and the decomposition rate slows down. As the depth of mining increases, the rate of hydrate decomposition slows and the position at which decomposition begins to move up. In deep sea mining below 1500 m, the increase of mining depth has little effect on the decomposition rate of hydrate, and the decomposition starting position is always near 510 m in sea depth. The pipe pressure loss gradient decreases as the pipe diameter increases. After the pipe diameter is larger than 300 mm, the pressure loss gradient decreases slowly, and the pressure loss gradient drops sharply at 450 mm, and eventually stabilizes after 500 mm. When the inlet velocity of the pipe is low, the fluid flow in the pipe is unstable and reflow occurs. The pipe pressure loss gradient first decreases and then increases as the fluid flow rate increases, and there is an optimal flow rate value that minimizes the pressure loss gradient.

中文翻译：

---

天然气水合物管道输送三相流动特性研究

摘要 基于热力学和流体力学的基本原理，建立了天然气水合物水力举升管道的温压模型、水合物分解传质模型和管道多相流数学模型。分析了管道出口背压、分解面与海水深度的关系。在此基础上，对天然气水合物管道输送进行了数值模拟和实验验证。分析了管径、入口流速和固相参数对天然气水合物管道三相流动的影响。结果表明，随着出口压力的增加，水合物开始分解的位置向上移动，分解速度减慢。随着开采深度的增加，水合物分解的速度减慢，分解的位置开始向上移动。在1 500 m以下深海开采中，开采深度的增加对水合物分解速率的影响不大，分解起始位置始终在海深510 m附近。管道压力损失梯度随着管道直径的增加而减小。管径大于300mm后，压力损失梯度缓慢下降，压力损失梯度在450mm处急剧下降，500mm后最终趋于稳定。当管道入口速度低时，管道内流体流动不稳定，发生回流。管道压力损失梯度随着流体流量的增加先减小后增大，