Study On The Sieving Mechanism Of Tea Plane-Surface Round Sifter

Tea plane-surface round sifter is one of the most important screen machine, which is used in tea screening. It screens the tea according to the size and length. The effect of screening not only has a great impact on the value of the product, but also directly impacts the efficiency of the follow-up operations. But due to the complex and probabilistic nature of the research subject, there still has not had a complete theory to explain the influence posed by the regularity of the sieve bed’s motion on screening effect. Theoretical attempts to explain the factors that affect the clean sifting rate of tea plane-surface round sifter, and analyze the influence of the affecting factors to the clean sifting rate is of important practical significance in that it can provide the theoretical basis for the production practices.This paper analyzed the regularity of motion that single-particle tea sliding on the screen surface by using the knowledge of the theoretical mechanics, and analyzed the various factors that influence the clean sifting rate of tea plane-surface round sifter, and analyzed the value ranges of motion parameters when the clean sifting rate is high. At the same time, this paper numerically simulated the sieving process of tea particle flow based on PFC3D of discrete element method, to verify the correctness of the theory, and investigated the influence of motion parameters to the clean sifting rate.The result shows that tea particle is in a relative screw motion along the screen surface, and the regularity of motion is determined by the radius of gyration, the velocity of rotation, the slope angle of sieve surface and the friction coefficient between particle and sieve surface. The clean sifting rate of tea plane-surface round sifter is affected by the velocity of relative movement, the vector radius of relative movement and the length of relative path. The value of the clean sifting rate could be higher when the radius of gyration makes0.024m-0.04m, and the velocity of rotation makes150r/min-220r/min. For different size of tea particles, the best velocity of rotation is different. The best velocity of rotation for little particles is less than the bigger particles; it can achieve high rate when the radius of gyration takes larger value, no matter what kind of sieve is used, this situation is appropriate for the case of more than one sieve. Through the simulation the sieving process, the paper found that the best velocity of rotation in practical situation is larger than the theoretical value. Furthermore, through analysis of the data retrieved from the simulation process, it successfully obtained the control model of the rotational velocity.