Study On The Distribution Characteristics Of Non-uniform Coarse Particles In The Process Of Pipeline Hydraulic Conveying

Mineral resources are one of the most important material basis for social economic development,and reasonable and effective transportation of mineral resources is an important part of utilizing mineral resources.Hydraulic pipeline transportation is a premiere way of transporting mode because its adaptability to complex terrain condition,lesser damage to ecological environment and lower constructing and operating cost.Due to the stricter requirements of environmental protection and in order to utilizing the mining resources efficiently,many engineering projects require direct transporting of materials which containing coarse particles materials(particle size up to 3mm-5mm).Because the coarse particles materials are very easy to stuck on the bottom of horizontal pipe and the sedimentation of coarse particles materials will disabled the pipeline system.So it is very important to study the characteristics of the hydraulic transportation of coarse particles.In this paper,based on the experiment of the laboratory hydraulic pipeline transportation pipeline,the author using Particle Image Velocimetry(PIV)to study and research the concentration distribution features about uniform and non-uniform coarse particle in pipe section,and then get conclusions as below:(1)Based on the PIV technique,the concentration distribution features of the uniform coarse particles and non-uniform coarse particles in the pipeline section are obtained.As well as the particle trajectories in the pipe section(2)Under the designed condition of experiment in the laboratory,the concentration distribution type of uniform coarse particles was Type ?,which the location of the maximum concentration is not at the bottom of pipeline but above it.The distribution type of non-uniform coarse particle was the same.(3)Comparing the concentration distribution data of uniform coarse particles with different particle size and flow rate,it can found that for the particles with the same size,with the increase of flow rate,the maximum concentration decreases and the relative height of the maximum concentration increases,the concentration distribution of particles in pipe section tends to be more uniform.Under the same flow rate,the larger the particle size is,the closer the location of maximum concentration is to the bottom of the pipeline,and the particle concentration distribution in the pipe section tend to be more uniform.(4)From view of force analysis,considering the effective gravity,fluctuating lift effect,Saffman force,Magnus force,the impact force of uniform coarse particle and the collision force between the particles and the wall,the author analyzed the mechanical mechanism of coarse particle concentration distribution in pipeline section.In this paper,the author introduce a parameter k,which represents the ratio of the comprehensive lift to the effective gravity,and use the k to modify the diffusion equation used in the past.The new diffusion equation can explain two different forms of the vertical concentration distribution of particles,Type I,and Type ?.(5)By comparing the data of concentration distribution of non-uniform particle under different-sized particle proportion with different flow velocity,it shows that the particle concentration distribution type in the pipeline section is Type I and the maximum concentration of 3mm particles mixed with 1mm particles is higher than non-mixed 3mm particles.Under certain particle proportion condition,the maximum concentration of two kinds of particles both increased with the increase of flow velocity,and the maximum concentration of 1mm particles is higher than that of 3mm particles with greater flow velocity.In the same flow velocity of 1.5m/s,the relative height of maximum concentration site of 3mm particles is higher than that of 1mm particles.In the flow velocity of 2.0m/s and 2.5m/s,as particles' quantity ratio increase,the relative height of maximum concentration site of 1mm particles gradually approach to the relative height of maximum concentration site of 3mm particles.The author calculated the impact force of different sized particles in different flow velocity,analyzed and explicated the characteristic of concentration distribution,proved the impact force's influence on the concentration distribution by tracking the movement trajectory and the vertical pulse speed.