水合物相变的内输多相流流动特性研究

Study on Flow Characteristics of Multiphase Flow in Internal Transport of Hydrate Phase Transition

天然水合物在柔性立管的举升过程中会由于压力的变化发生分解,相变过程由立管底部的固液两相流到立管顶部的气液固三相流。基于计算流体力学(CFD)方法,利用FLUENT软件建立悬链线型柔性立管模型,采用Euler多相流模型,结合UDF添加源项来模拟水合物分解过程,得到了不同影响参数下立管内水合物的流动特性。结果表明:颗粒体积分数和悬挂角的增加会使立管内持气率增加,从而减小水合物运输能耗;入口速度的增大会增加立管出口处的颗粒速度,使管道中的持气率减少,速度的增大使所需泵的能量消耗增加;颗粒体积分数的增加,使立管中持气率增加,所需泵的能耗先减小后增大,即颗粒体积分数存在最优值。在实际工程中可根据需要,通过调整相关参数达到减小能耗的目的。

The natural hydrate will decompose due to the change of pressure during the lifting process of the flexible riser,and the phase change process will flow from the solid-liquid two-phase flow at the bottom of the riser to the gas-liquid-solid three-phase flow at the top of the riser.Based on the computational fluid dynamics(CFD)method,the catenary linear flexible riser model was established by FLUENT,and the Euler multiphase flow model was used to simulate the hydrate decomposition process by combining the UDF source term,and the flow characteristics of hydrate in the riser under different influencing parameters were obtained.The results show that the increase of particle volume fraction and suspension angle can increase the gas holding capacity in the riser,thereby reducing the energy consumption of hydrate transportation.The increase of inlet speed can increase the particle velocity at the outlet of the riser,so that the gas holding rate in the pipeline is reduced,and the increase of speed will increase the energy consumption of the required pump.The increase of particle volume fraction increases the gas holding rate in the riser,and the energy consumption of the required pump first decreases and then increases,there is an optimal value for particle volume fraction.In the actual project,the purpose of reducing energy consumption can be achieved by adjusting the relevant parameters according to needs.