Flow Field Analysis And Structural Parameter Optimization Of Harvesting Device Of Alfalfa Seed Harvester

Planting area and total output of alfalfa are ranked among the top of the whole world in our country.With the development of graziery,the planting of alfalfa are sustained and rapid growth.But the level of the technology of mechanized harvest of alfalfa seeds is low.This paper is based on 9ZQ-2.7 alfalfa seed harvester.Which is theoretical analysis and experimental study the inside of the harvesting device and CFD simulation and structural optimization design of the harvesting device.The target of the study is to enhance the import speed distribution uniformity.The main contents and conclusions are as follows:Firstly,experimental study on physical and aerodynamic characteristics of alfalfa plants and pods are carried out in the paper.Based on the statistical principle,the basic data of the physical and mechanical properties and aerodynamic characteristics of alfalfa with representative species in the north were established.The conclusion of the height of the alfalfa plant,the height of the pods,the height of the lower part of the pods,the difference of the pods,the diameter of the plant,the diameter of the middle part of the plant,the diameter of the bottom of the plant are 796?1184 mm?741?1123 mm?490?610mm?181?559 mm?1.08?1.52 mm?2.20?3.32 mm?2.46?3.58 mm respectively.The suspension velocity of alfalfa seed and pod was 5.06±0.15 m/s?6.95±0.14 m/s.The suspension velocity of stems was 8.26±0.15 m/s.All of those provide data support for the improvement of the harvesting device.Secondly,the working principle of 9ZQ-2.7 alfalfa seed collecting machine and the structure of harvesting device are systematically studied.According to the structure of the harvesting device,the 3D CAD model was established,and the model was simplified by the pretreatment software.The grid was divided by tetrahedral element.Twenty-five pressure inlet and one pressure outlet were set up.The k-? standard turbulence model is established.The velocity-pressure coupling SIMPLE algorithm is adopted in the study.The pressure at the inlet is 101325 Pa for the standard atmospheric pressure and 101085 Pa at the outlet to simulate the distribution of the airflow field in the harvesting device.Analyze the simulation results:the inlet speed of the original structure is gradually reduced from the left ? to the right ?,while the velocity at the wind regulating plate fluctuates.The speed can reach 15.7 m/s.on the left.On the another side this value is 3.61 m/s.Though those determine the uniformity of the velocity distribution of the original structure.Thirdly,on the basis of the original structure,the simulation analysis and experiment were carried out,and it was found that the velocity distribution uniformity of the inlet was poor.According to the existing problems,the original structure is improved,and 20 kinds of improvement schemes are designed.The simulation scheme is simulated and then the three distributions with good uniformity are selected for experimental verification.The results of the three schemes are compared and analyzed to determine the optimal scheme is "12".The structure of the scheme "12":d1=198 mm,d2=175 mm,a1=15°,a2=20°.