Analysis Of Flow Field Characteristics Of Natural Gas Hydrate

In recent years,the solid fluidization method for the exploitation of natural gas hydrate has been put forward,which is widely concerned because it does not need to establish a closed exploitation environment,has high exploitation efficiency and has a good development prospect.However,the solid fluidization method needs to lift the gas hydrate particles to the sea surface through the riser,which has higher requirements for the transportation system.Therefore,it is necessary to study the flow field in the riser,and provides some basis for the study of riser safety.In this paper,the Euler-Euler model in FLUENT software of ANSYS is used to study and analyze the characteristics of flow field in liquid-solid two-phase flow of natural gas hydrate transported in the vertical riser and the bending and vibration state of the riser in the deep sea.The main works of the dissertation are as follows:(1)Determination of the range of vertical riser hydraulic conveying parameters,including the value range of particle density,particle diameter,pipeline diameter,volume concentration and transportation speed.Then,the force of natural gas hydrate particles in the riser was discussed,the motion equation of particles was established,and the commonly used liquid-solid two-phase flow model was analyzed and compared.Finally,the Euler-Euler model was selected to study and analyze the particle flow in the pipeline.(2)Analysis of internal flow field characteristics of vertical riser.The vertical riser model was established by ICEM and compared with the experiment to verify the correctness of the riser model and the applicability of the Euler-Euler model in FLUENT for liquid-solid twophase flow.Then this paper analyzed the volume fraction,velocity distribution and pressure loss of particles at different heights in the riser,and systematically discussed the influence law of each conveying parameter on the volume fraction distribution and velocity distribution of particles in the riser,and finally analyzed the influence law of conveying parameter on the pressure loss and friction loss per unit length.(3)Analysis of internal flow field characteristics of bending state of the riser.The bending riser model was established to analyze the volume fraction,velocity distribution and pressure loss of particles in the riser along the length of the curved riser,Then this paper systematically discussed the influences of various parameters on the concentration distribution,velocity distribution and secondary flow of particles after passing through the bending riser and the inclined riser.Then this paper analyzed the influence of different conveying parameters on the pressure loss and the force on the bend section of the pipe.(4)Analysis of internal flow field characteristics of vibration state of the riser.The range of vibration parameters of the riser was determined,and the vertical vibration riser model was established to analyze particle volume fraction distribution,velocity distribution,pressure and pressure loss,and riser stress in a single period.The influence of different amplitude and frequency on the distribution of particle volume fraction and velocity in the riser was also discussed.Finally,the pressure loss per unit length of vertical riser under vibration and the relationship between the force per unit length and amplitude and frequency are analyzed.