Three-phase flow of submarine gas hydrate pipe transport

LI Li(李立)^{1, 2}, XU Hai-liang(徐海良)^{1, 2}, YANG Fang-qiong(杨放琼)^{1, 2}

(1. State Key Laboratory of High Performance and Complex Manufacturing (Central South University),
Changsha 410083, China;
2. School of Mechanical and Electrical Engineering, Central South University, Changsha 410083, China)

Abstract:In the hydraulic transporting process of cutter-suction mining natural gas hydrate, when the temperature-pressure equilibrium of gas hydrate is broken, gas hydrates dissociate into gas. As a result, solid-liquid two-phase flow (hydrate and water) transforms into gas-solid-liquid three-phase flow (methane, hydrate and water) inside the pipeline. The Euler model and CFD-PBM model were used to simulate gas-solid-liquid three-phase flow. Numerical simulation results show that the gas and solid phase gradually accumulate to the center of the pipe. Flow velocity decreases from center to boundary of the pipe along the radial direction. Comparison of numerical simulation results of two models reveals that the flow state simulated by CFD-PBM model is more uniform than that simulated by Euler model, and the main behavior of the bubble is small bubbles coalescence to large one. Comparison of numerical simulation and experimental investigation shows that the values of flow velocity and gas fraction in CFD-PBM model agree with experimental data better than those in Euler model. The proposed PBM model provides a more accurate and effective way to estimate three-phase flow state of transporting gas hydrate within the submarine pipeline.

Key words:gas hydrate; pipe transport; three-phase flow; Euler model; CFD-PBM model