Design And Experiment Of The Cleaning Device For The Combined Harvester Of Ratooning Rice

Ratooning rice is a type of double-harvest rice variety that is bred using the dormant buds that survive on the rice pile after harvesting to make the heading mature again.When harvesting the first season rice,only about 2/3 of the upper part of the rice plant is cut off,leaving 1/3 of the plant and root system to ensure the normal growth of the second season of the rice.In this paper,an improved design was made for the cleaning device of the newly-developed single-axle-flow combined harvester for ratooning rice.The specific research content of this paper includes the following aspects:(1)Crop analysisUsing ‘Zhendao No.18’ as the test object.The head part of the ear was cut to simulate the harvesting characteristics of the regenerated rice.This part of the material was fed into a threshing device of a 4LZ-3.0E single longitudinal axial flow combine harvester.The composition of the rice mixture,the distribution on the vibrating screen and the suspension speed of each component were compared and analyzed.(2)Improved design of cleaning deviceA cleaning device was designed for the effluent of ratooning rice.A six-blade centrifugal fan was designed based on the gas flow required by the material.The vibrating screen adopts the shutter screen instead of the fish scale screen.By increasing the mesh size of the lower braiding sieve,the sieve permeability of the grains can be improved.At the same time,the draft screen is removed and the shutter screen is extended to improve the cleaning area.At the same time,the feeding auger was improved to raise the pushing efficiency under the condition of large feeding quantity.(3)CFD numerical simulation of internal flow channel model of cleaning deviceA three-dimensional flow channel model including a fan was established.The FLUENT software was used to numerically calculate the airflow field.By analyzing the airflow field streamline diagram and wind speed cloud diagram,the distributionlaw of wind speed under different sieve openings was obtained.The simulation results were verified by the hot wire anemometer in the processing plant.The results show that when the opening of the shutter screen is 20 mm,the air guide effect is the best.The wind speed distribution above the screen surface is reasonable,which can meet the cleaning requirements.Comparing the measured data with the calculated results,it can be seen that the wind speed variation law of the two is similar,and the simulation is reliable.However,the calculated results are up to 23.53% higher than the measured wind speed.The reason is that the flow channel model is in the ideal condition of incompressibility and no consideration of gas viscosity.(4)Field cleaning performance testThrough the field cleaning performance test,the cleaning effect of shutter screen and fish scale screen was compared.Furthermore,the effects of sieve opening scale and vibration frequency of cleaning screen on the impurity content and loss rate were analyzed.It shows that there is no obvious difference in the impurity rate of the seeds when using the fish scale screen and the shutter screen.Under most working conditions,both can control the impurity rate within 2%.The overall loss of the grain caused by the fish scale screen is higher.It is not suitable to work under the condition that the vibration frequency is higher than 7Hz,at this time,the grain loss caused is easily higher than 3% which cannot meet the national standard.Considering the economic benefits,shutter screen is more suitable for the cleaning of ratooning rice than fish scale screen in the first season.Under the working condition that the feeding amount is 5.36kg/s and the fan speed is 1050r/min,the best working parameters of the louver screen are the opening of the screen 20 mm and the vibration frequency of 6Hz.