The Study Of Particles Pulsation Properties During Discharging In Silo

Being different from the traditional solid, liquid and gas, particle materials are regarded as fourth form material which aroused great concern and a lot of research. The accumulation、blocking、dense flow and mixing separation of granular materials are the hot point and difficult problems. The storage and transportation of bulk grain is essential in the process of production. It link process equipment and production together to form an organic un ity. Silo as an important equipment of storage materials, not only for the storage, but also has other functions, such as balancing process, homogenizing the materials, storing materials for emergency and so on. For the safe operation of silo, and improving production efficiency, Study about granular flow in silo has important scientific research value.The strong dynamic effects of granular flow in the silo tend to exhibit strong particle pulsation and even cause the vibration of silo, “silo music”. But due to the limitations of experimental methods, the research of dynamic effects caused by the particle pulsation still stays in a simple surface phenomenon, such as noise, the minimum critical height for happening silo music and factors affecting particle pulsation, they could not analyze the profound changes in silo, not at all the motion state and law of all particles. T his paper based on the discrete element method to simulate the discharge experiment of ellipsoidal particles with variable geometry and friction coefficient in the deep silo under gravity, The average velocity fluctuation was used to investigate particles pulsation, normal force was used to express contact force among particles, The pressure of silo wall subjected was used to indicate intensity change of dynamic arch, main conclusions is as follow.(1) The particles velocity began to fluctuate after discharging, and showed two different waveforms during the whole discharging stage: one is large amplitude and periodic fluctuation in early stage which the peaks and valleys are clearly visible; the other one is small amplitude and irregular fluctuation in late stage which the peak values cannot be identified. The stress disappearing phenomenon occurred in the early period of intense fluctuation, and the occurred time is the peak moment of speed fluctuation, and also the time of top particles appeared maximum displacement difference.(2) The main cause of stress disappearance is the weight loss of the top granular layer, the range of stress disappeared can be judged by the force vector of the particle.(3) It is small amplitude and irregular fluctuation in the bottom of storage material, and the waveforms of particles layers nearby are similar in the discharging; the closer to the top of storage material, the smaller of the particles velocities, the larger amplitude of the fluctu ation, and present a stronger cyclical fluctuation, and the wave forms are different in the discharging.(4) Particle fluctuation intensity weak gradually with the increase of the half cone angle, and the higher of the half cone angle, the smaller the occurrence frequency and duration of the stress disappearance phenomenon; Smaller coefficient of friction does not cause this phenomenon.(5) The maximum dynamic pressure is located in 1/3 height of the cylinder above from the joining point of hopper and cylinder.