Parameter optimization and experiment of funnel-shaped heavy impurity separator in seed cotton cleaning process

Abstract: Seed cotton cleaning is widely used in the cotton processing industry. A funnel-shaped heavy impurity separator can not only remove impurities effectively, such as nails, pebbles and cotton shells, but also can improve cotton grade without causing any damage. However, with the improvement of cotton processing technology, how to improve cleaning efficiency and reduce the loss rate of seed cotton become important. In order to improve the efficiency of a funnel-shaped heavy impurity separator in removing impurities and reducing the loss rate of cotton, in this paper, we took MQZH-10-funnel-shaped separator as the object of the research. There are four main parameters (air velocity in seed cotton inlet, angle of adjustable deflector, air velocity in auxiliary air inlet, angle of adjustable baffle) which affect the loss rate of cotton and the separating rate of impurities in this paper. In order to measure the cleaning efficiency of funnel-shaped heavy impurity separator, in this paper, we set up four indicators (the loss rate of seed cotton, loss rate of nails, loss rate of pebble, loss rate of cotton shell), and analyzed the moving track of the seed cotton and impurities in a simulated way, which was based on the discrete phase model (DPM) of computational fluid dynamics (CFD). The moving track analysis of the DPM model showed that the moving track of seed cotton particles was different from the impurity particles. Most of seed cotton particles followed the airflow, escaping from the cotton outlet because of its lighter quality, and few escaped from the notch. However, due to the heavier weight, the impurity particles produced large inertia so that most of them escaped from the notch, while a small number escaped from the cotton outlet .Then, the quadratic regression orthogonal experimental method with 4 factors and 5 levels for each factor was employed with 36 experiments in total. By quadratic regression orthogonal experimental method, experimental results of the variance analysis showed that the order (from high to low) of these 4 factors which influenced the loss rate of cotton was air velocity in seed cotton inlet > air velocity in auxiliary air inlet > angle of adjustable deflector > angle of adjustable baffle. The order (from high to low) of the impurities separating rate was air velocity in seed cotton inlet > angle of adjustable deflector > air velocity in auxiliary air inlet > angle of adjustable baffle. When the funnel-shaped heavy impurity separator cleaned impurities, the influence of the 4 parameters towards the 4 indicators should be considered to maximize the cleaning efficiency under the premise of low cotton rates. Hence, the comprehensive optimization method towards the above-mentioned 4 parameters was conducted in order to find the best combination of this 4 parameters to satisfy the above 4 indicators. To do this, the "linear effect coefficient method" was used to normalize the target functions and establish the comprehensive target function by the use of linear weighting method. What's more, the evaluation function method was used to converse multi-objective optimization into a single objective nonlinear optimization problem. In the end, multi-objective nonlinear optimization method was used to determine the best parameter combination of the funnel-shaped heavy impurity separator in separating aspect. The optimal parameters were: air velocity in seed cotton inlet, 21m/s, angle of adjustable deflector, 44°, air velocity in auxiliary air inlet, 2m/s, angle of adjustable baffle, 45°. Under these conditions, the loss rate of seed cotton was 0.48%, loss rate of nails was 96.59%, loss rate of pebble was 85.96%, loss rate of cotton shell was 31.57%.