Influence Of Different Ratio Of Bending-ring On Gas-solid Two-phase Flow Characteristics

Pneumatic conveying refers to the use of gas with a certain pressure and speed in the pipeline so that the material can be continuously transported according to the planned line.It has the advantages of high economy,safe operation,high transmission efficiency and low environmental pollution,so the technology is widely used in mining,pharmaceutical,chemical and metallurgical industries.However,some problems also arise in the actual production operations,such as: large system energy loss,material blocking the delivery pipe,wear of the pipeline and material crushing.This paper will analyze and study the gas-solid two-phase flow mechanism with different ratios of bending and diameter through experiments and numerical simulations.The main work is as follows:Firstly,the research status on various aspects of pneumatic conveying of experts and scholars at home and abroad were summarized;The development trend of pneumatic conveying technology in recent years was analyzed;The characteristics and deficiencies of the pneumatic conveying of the dilute phase were discussed;The purpose and content of this paper were explained;The research plan of this paper were developed.Secondly,a set of dilute phase pneumatic conveying test equipment consistent with actual conditions was designed and built;The pressure sensors was used to measure the change in system pressure loss as a function of air speed at different ratios of bend to diameter,and then the pressure loss and gas velocity were calculated;By changing the mass flow rate of the particles,the bending ratio of the elbow,the shape of the particles and other process parameters,the effect of different operating conditions on system energy loss and pressure loss were analyzed.The results show that with the increase of the ratio of the bending diameter,the pressure loss and energy loss of the system decrease;With the increase of the mass flow of the particles,the pressure drop increases,the energy and additional pressure loss coefficient decrease;Void-shaped particles has a relatively small loss of pressure and energy to the system.Finally,the CFD-DEM coupled model was used to study the gas-solid two-phase flow characteristics under different ratios of bending to diameter;The mathematical model and physical model of the mechanism of the dilute phase pneumatic conveying were given;Comparing of test and numerical simulation data under the same conditions,it was verified that the CFD-DEM model could predict gas-solid two-phase flow characteristics.The feasibility and numerical simulation of the effects of gas phase,solid-phase flow and bend wear on the gas-solid two-phase flow at different ratios of bending to diameter were analyzed.The results show that the area of high gas velocity and turbulent kinetic energy at the elbow increase with the increase of the ratio of the radius of curvature,and the pressure drop between the internal and external walls decreases;The shape and distribution of particle flow in the lower elbow with different ratios of bending and diameter are not the same,and the collision in the bend pipe is also dominated by particle-particle collisions;With the increase in the ratio of the bending radius,wear area gradually increases,but the maximum wear and tear gradually decreased,the largest wear area is offset toward the bend inlet.