惯性气流式红枣清选系统设计与试验

Design and Experiment of Inertia Pneumatic Type Cleaner System of Jujube Fruit

清选系统是气吸式红枣收获机的重要组成部分,降低清选含杂率、损失率和破损率是实现红枣收获机械化的关键技术。利用枣、杂惯性和流体力学特性差异,设计了一种惯性气流式红枣清选系统,并对其关键部件及结构参数进行设计和分析。采用Fluent软件探明了该清选系统内气流运动形成的“∞”形旋流有利于枣、杂的清选。为获得清选系统最佳工作参数,以气流速度、调节板开度为试验因素,以含杂率、损失率和破损率为评价指标,设计二次正交旋转组合试验。建立试验因素与指标间的回归模型,采用多目标优化算法进行参数优化,确定清选系统最优参数组合:气流速度为32.0 m/s,调节板开度为3.4 cm。在该条件下开展验证试验,得到含杂率、损失率和破损率分别为1.38%、3.37%和0.60%,与优化参数相比分别增加了0.06、0.12、0.03个百分点。该清选系统满足枣、杂清选作业要求。

Xinjiang Uygur Autonomous Region is the major region for high quality dried processing jujube fruit.The period of jujube harvesting was usually after the frost to enhance the quality of jujube fruit.At this time,a large number of mature jujube fruit were fallen off from trees naturally.The method of jujube fruit harvester was usually picked-up from the ground.The jujube harvesting machine of air suction type was the most commonly used one among the jujube harvesters.Its working principle was to suck up the jujube fruit through negative pressure airflow.But when sucking jujube fruit,the impurities materials such as jujube leaf,jujube crane were sucking attached.Thus the cleaning device was employed to remove the impurities materials.Traditional cleaning devices would cause some problems such as high impurity,damage,and lost jujube fruit.Inertial airflow cleaning system was designed that utilized the difference between the mechanical properties and fluid properties of jujube fruit and impurity.The cleaning system was mainly composed of the feeding inlet,guide surface,closed-air aspirator,baffle,filtering impurities device etc.Then the structure size of the cleaning system was designed by combining the principle of cleaning and the principle of conservation of fluid flow rate.In addition,the guide surface shape was analyzed through characteristics of material motion trajectory and numerical analysis.Furthermore,Fluent software was used to simulate the flow field track in the clearing system.This can assess the flow field characteristics intuitively and determine whether swirling flow occurred that available for separating impurities with expectations.To analyze the influence regularity of single test factors on the evaluation index,the factors of airflow velocity and baffle opening size values were selected as the test factors.Meanwhile,the impurity rate,loss rate,and damage rate were chosen as evaluation indexes.The single factor tests were employed to determine the parameter interval.The results showed that airflow velocity and baffle opening size values were 32~38 m/s and-1~4 cm,respectively.Moreover,the central combination experimental method of Design-Expert 10.0.3 software was used to analyze the influence of the interaction factors on the evaluation index.After that,the analysis module were used to determine the optimal parameter values.The results showed that the impurity rate,loss rate,and damage rate were 1.32%,3.25%,and 0.57%,respectively,when the airflow velocity was 32.0 m/s and the baffles opening size was 3.4 cm.Furthermore,the field tests were carried out at the combination of optimal parameters to verify the accuracy of the optimization parameters and the performance of the cleaning system.The verified results showed that the impurity rate,loss rate,and damage rate were 1.38%,3.37%,0.60%,respectively,which were increased by 0.06 percentage points,0.12 percentage points and 0.03 percentage points respectively compared with the optimized parameters.The cleaning system can meet the requirements of jujube mixed cleaning operation and the research result can provide reference for the development of air suction type jujube harvester.