Research On The Mechanical Behavior Of Solid Particles In Horizontal Axis Rotating Flow Field

Zhou Shouwei,Academician of Chinese Academy of Engineering,first proposed a new idea of "solid-state fluidized mining technology for submarine superficial hydrate accumulation"in the world.There are two key links in the mining process.One is how to efficiently and economically realize the mud and sand separation of seabed hydrate slurry.The second is how to better transport the mixture containing sediment,to avoid sand blocking in the transport process.The hydrocyclone separation of seabed hydrate slurry and the spiral transport of hydrate slurry mixture in pipelines involve the movement of particles in the swirling field.In order to improve the pre-separation efficiency of seabed hydrate slurry and better realize the transport target of high concentration and low energy consumption of the round pipe,the mechanical behavior of single particles with different densities in the swirling flow field was analyzed theoretically and experimentally in this paper.The following research work was carried out:(1)To obtain relevant literature and materials by consulting domestic and foreign academic journals,master and doctoral papers,patents and international frontier information,comprehensive analysed and grasped the research status of particle motion law in the swirling flow field.(2)Calibration of experimental equipment and simulation analysis of swirl field.In order to reduce the errors generated in the experiment,the experimental device was comprehensively calibrated.The software Fluent was used to simulate the flow field simulation analysis on the horizontal axis swirl field used in the experiment,so as to determine the changes of flow field parameters such as velocity and pressure under different rotational speeds.(3)Experimental measurement and mechanical analysis of the single heavy particle in horizontal axial swirl field.The heavy borosilicate spherical particles with a density similar to sediment were used to replace the sediment particles.The motion experiment of borosilicate single particle with different particle sizes were carried in the horizontal axis drum respectively under the pure dry friction,wetting condition and the condition of filled with water.Through the observation of the experimental phenomena and the processing of the experimental results,the movement law of particles and the change of stress state under different conditions were analyzed.(4)Experimental measurement and mechanical study on the motion of the single light particle in horizontal axis forced swirling flow field.The light polypropylene(PP)spherical particles with a density similar to hydrate were used to replace the hydrate particles.The movement experiment of the single PP spherical particles in the horizontal axis forced swirling flow field was carried out.This paper mainly studies the drag force and lift force of PP ball particles in the swirling flow field,and determines a new formula for calculating the drag force with experimental data fitting method,and theoretically derives a new formula for calculating the lift force.Through the above research,the rolling friction coefficient of borosilicate single particles in pure dry friction is obtained.When the borosilicate single particle move in the horizontal axis drum filled with water,with the increase of rotating speed of the drum,the particle movement will present the following states successively:stationary state attached to the wall,vibration state attached to the wall,suspension state,particle rotation state and rotating state along with the wall.as well as the force situation of particles under different states.The force of particles under different conditions was analyzed.It was found that the initial suspension speed,initial rotation speed and initial rotation speed attached to the wall of borosilicate ball particles are proportional to the particle size.In addition,it is found that the PP single particle were basically at a certain point near the X axis when the motion was stable,and the particle almost did the pure rolling motion with the static center of mass.The new empirical formula of drag force coefficient for the PP particles with different particle sizes in the range of different particle Reynolds number is obtained,which is more accurate than the existing empirical formula of drag force coefficient.It is found that the existing formulas for calculating the particle lift have a large error when applied to the swirling flow field.For this reason,the concept of particle swirl field lift Fsm is proposed and defined in this paper.The corresponding formula of lift coefficient is derived theoretically,and the empirical relationship between the lift coefficient of the swirl field and the particle Reynolds number is obtained by fitting the experimental data.