Study On The Numerical Simulation And Improvement Of The Aerodynamic Part Of A Vacuum Cotton-Picking Machine

This paper studies on a lightweight vacuum cotton-picking machine, whose core component is a centrifugal fan. This portable machine can pick the cotton thoroughly, and fewer impurities are picked by using it. But this machine can’t suck the cotton in successfully when the cotton sticks on the cotton boll tightly. Then the operator has to pick it by hand, so that the picking efficiency is influenced. After experiments, we discover that the "sucking force" of the machine is determined by both the vacuum degree and ventilation quantity on the inlet. So sucking power is selected to measure the "sucking force" of the cotton-picking machine.The author first builds the fluid area model, and then computing grids are divided and boundary types are defined on the model with help of GAMBIT, which is a software of simulation pretreatment. The final step is to set up simulation variables and iterate in FLUENT, and different situations are simulated under different ventilation quantities.Secondly the author output the vacuum degree under every corresponding ventilation quantity, then the curve describing the relationship of sucking power and ventilation quantity is drawn and analyzed. In order to certify the reliability of simulation analysis, the curves drawn by simulation data and experiment data are compared and analyzed. At the same time, this paper also analyses the picture of pressure field and velocity field of the centrifugal fan when the cotton-picking machine is operated under a certain ventilation quantity.At last, the paper takes enhancing the sucking power as the main target. The author uses fishbone diagram to find out the reasons which influence the sucking power. After discussing the necessary to research of every former reasons, the factors are determined to be researched to increase the sucking power. Then the author separately changes the following structure parameters:number of blades, outlet installation angle of blades and outlet width of blades. Then the influence of every structure parameter to the aerodynamic characteristics of the machine is simulated and analyzed. While considering enhancing the sucking power and decreasing the flow losses meanwhile, the author selects some positive parameters and groups them. Finally obtains two improvement projects. Next work is to model and simulate separately after the two improvement projects are applied. After comparing and analyzing the simulation result, the author chooses a better improvement project, and proposes a appropriate ventilation quantity. Finally the accuracy of simulation data and the reliability of the improvement project are proved by testing.