The Numerical Simulation Study Of Hydrate Slurry Flow In Horizontal Pipes

Natural gas hydrate is recognized as one of the most ideal alternative energy sources in the 21st century.Many countries have increased their investment in natural gas hydrate research,among which,the research on hydrate slurry flow characteristics to improve its transportation safety and economy is a hot spot.However,there are still some deficiencies in the research of gas hydrate slurry flow characteristics in the current public literature:the microscopic behaviors such as collision and aggregation between hydrate particles in the process of hydrate slurry transportation are rarely considered;collision,aggregation and other microscopic behaviors of hydrate particles are rarely considered The crushing mechanism of hydrate particles needs to be improved.Therefore,in this paper,based on the collision,aggregation and fragmentation of hydrate particles,the hydrate slurry flow in the pipeline is simulated,which provides theoretical support for the realization of large-scale exploitation of natural gas hydrate on the seabed and the safety of gas hydrate transportation.In this paper,PBM calculation model is established for the collision,aggregation and crushing behavior of hydrate particles,and UDF embedded in FLUENT is compiled.Aiming at the hydrate slurry flow process in the pipeline,the influence of geometry structure,operation conditions and flowing working fluid on the hydrate slurry flow characteristics in the pipeline is investigated by numerical simulation;the horizontal internally grooved pipe model is established to study the thread spacing,thread height and operation The numerical simulation results of CH₄ hydrate slurry flow in internal screw pipe are compared with those in horizontal straight pipe,which provides theoretical support for strengthening CH₄ hydrate slurry flow.The results show that:with the increase of pipeline length,the pressure drop of hydrate slurry flow process increases,and the local aggregation degree of hydrate particles increases;with the increase of flow velocity,the pressure drop of hydrate slurry flow process increases,and the energy loss increases,but the hydrate particles in the pipeline are easier to disperse.At higher velocity,the average diameter of hydrate particles in the pipeline first increases rapidly and then tends to be stable When the volume fraction of hydrate particles is relatively small,the average diameter of hydrate particles in the pipeline will directly tend to be stable after going through the growth stage,and there will be no obvious fluctuation stage;with the increase of initial diameter of hydrate particles,the average particle size of hydrate particles in the pipeline also increases;when the volume fraction of hydrate particles is 25.04%,the phase of water and hydrate particles will increase In the flow process of CH₄ hydrate slurry in a 4.124m long horizontal straight pipe with an initial velocity of 4m/s,initial hydrate particle size of 5?m and length of 4.124m,the average diameter of hydrate particles at the outlet section of the pipeline first decreases slightly with the increase of pipe diameter.When the pipe diameter increases to 30mm,the average diameter of hydrate particles at the outlet section of the pipeline remains unchanged;with the increase of the volume fraction of hydrate particles,the average diameter of hydrate particles in the pipeline increases Compared with the horizontal straight pipe,the pressure drop of CH₄ hydrate slurry flow in the internal grooved pipe is increased(all higher than 27.65kpa in the horizontal straight pipe),but the hydrate particle volume fraction and hydrate particle size distribution at the outlet section of the pipe are more uniform under the centrifugal force in the inner spiral pipe.The stable value of average diameter of hydrate particles in horizontal rifled pipe is less than that in horizontal straight pipe,which indicates that hydrate slurry transportation in horizontal internally grooved pipe is more difficult to block,which has certain reference significance for practical engineering.