Analysis And Experimental Research On Flow Field In Crushing Chamber Of Straw Fodder Harvester

China is rich in straw resources,but the utilization rate of straw is low.Straw and feed harvester is the main machine to realize the resource utilization of straw.In order to improve the working efficiency and quality of straw and feed harvester,this thesis takes4JS-220 straw and feed harvester as the research object,analyzes the force and movement of straw in the harvest process,and establishes the dynamic equation in the process of straw crushing.According to the analysis results,the key components of the machine were optimized and designed.CFD software was used to simulate the flow field characteristics in the crushing room of the straw forage harvester,and field verification tests were carried out on the machine.The main work and research results are as follows:(1)A new type of flail structure is designed.The new flail is a combination of 2scimitars and a 75° straight knife,which has better pick-up performance and crushing performance;the arrangement of the flail is improved to a double helix,Improve cutting efficiency and reduce machine tool vibration.(2)The CFD software was used to study the pressure distribution law and the air flow characteristics inside the crushing chamber of the machine tool.The simulation results show that the flow velocity of the airflow in the inlet area of the casing is relatively stable.The flow velocity increases under the action of the high-speed rotation of the crushing knife shaft,the flow becomes turbulent,and multiple vortex areas are generated,and the airflow recirculates in some areas of the casing wall.The negative pressure generated at the entrance of the casing is conducive to the straw entering the crushing chamber,and the airflow pressure at the exit of the casing is relatively large,which is conducive to improving the efficiency of straw throwing.(3)Based on the above simulation results,the influence of the speed of the pulverizer shaft,the height of the casing from the ground and the distance from the blade tip to the casing on the characteristics of the flow field in the pulverizing chamber and the performance of the machine were further simulated and analyzed.From the simulation process,it can be concluded that increasing the speed of the crushing knife shaft can significantly improve the fluidity of the airflow in the crushing chamber,and the negative pressure at the entrance of the crushing chamber will increase with the increase of the speed,improving the straw picking performance;Excessive or too small height of the chassis from the ground will affect the picking performance of straw,but the greater the height of the chassis from the ground,the better the fluidity of the airflow in the crushing chamber;increasing the distance between the blade tip and the chassis will increase the airflow Fluidity in the crushing chamber.(4)Field test results show that the qualified rate of straw cut length is 90.30%,which meets the relevant national standards.This research provides a reference for the optimization design of straw forage harvester,and is of great significance for improving the utilization of straw resources.