基于CFD离散相模型的气流式皮棉清理机参数优化

Parameters optimization of flow-through air lint cleaner based on CFD discrete phase model

气流式皮棉清理机能有效的清除不孕籽、破籽等杂质,提高皮棉等级,且对皮棉不产生任何损伤。为提高气流式皮棉清理机的除杂效率,降低纤维损耗,对其除杂机理进行了分析。通过建立基于计算流体力学(computational fluid dynamics,CFD)的离散相模型(discrete phase model,DPM)对皮棉纤维轨迹、杂质轨迹分别进行了追踪分析,并对影响落棉率、除杂率的入口速度、出口压力和排杂槽口尺寸3个参数进行了仿真试验。通过正交试验方法,共进行了25组试验。根据正交试验的极差和方差分析,得出了影响气流式皮棉清理机落棉率的参数排序是入口速度>槽口尺寸>出口压力,影响除杂率的参数排序是槽口尺寸>入口速度>出口压力。通过建立综合评分标准,得出了气流式皮棉清理机的最优加工参数为入口速度20 m/s,出口压力-650 Pa,槽口尺寸30 mm,此时落棉率为5%,除杂率为90%。通过现场的加工试验验证,表明仿真分析所得出的优化组合和优劣分析是可行的,可为气流式皮棉清理机的加工工艺改善提供依据。

A flow-through air lint cleaner could effectively remove impurities such as sterile seeds or broken seeds, can improve cotton grade, and does not cause any damage. In order to improve the efficiency of a flow-through air lint cleaner in removing impurity and reduce the loss of cotton, this study was developed about the moving track of the lint fiber and impurity, through the discrete phase model （DPM） based on computational fluid dynamics （CFD）. The moving track analysis of the DPM model showed that the moving track of lint fiber particles were different from the impurity particles. Most of lint fiber particles following the airflow escaped from the cotton outlet because of its lighter quality, and a few escaped from the notch. However, the impurity particles due to the heavier weight produced large inertia, most escaped from the notch, while a small number following the airflow escaped from the cotton outlet. In the DPM model, 600 particles were used to respectively simulate the moving track of lint fiber and impurity. The loss rate of cotton was defined by the ratio of the fiber particle number escaping from the notch and the whole particles number, and the separating rate of impurity was defined by the ratio of the impurity particles number escaping from the notch and the whole particles number. That the loss rate of cotton was lower, and the separating rate of impurity was higher showed that the flow-through air lint cleaner performance was far superior. In this paper, three parameters （inlet airflow velocity, outlet pressure, and the notch size） affecting the loss rate of cotton and the separating rate of impurity were analyzed by the CFD simulation. By an orthogonal test method, a total of 25 experiments were carried out. Experimental results of the range and variance analysis showed that the order from high to low of factors influencing the loss rate of cotton were inlet airflow velocity〉 notch size 〉 outlet pressure, and also the order of the separating rate of impurity was notch size 〉 inlet airflow velocity 〉 outlet pressure. By establishing the integrated grading standard, the 25 experiments were given scores respectively. The optimal parameter combination was that given the highest score and the three parameters was that the inlet airflow velocity was 15 m/s, the outlet pressure was -650 Pa, and the notch size was 30 mm. The loss rate of cotton was 5%, and the separating rate of impurity was 90% with the optimal parameter combination. After an actual test in a factory, the test results showed that the parameter optimization analysis of the flow-through air lint cleaner using a CFD simulation and orthogonal method was likely feasible.