Optimization Design And Experiment Of Precision Pneumatic Hill-Drop Drilling Of Rice

Rice is one of the main food crops in our country.The technology of rice mechanical direct seeding can significantly reduce the consumption of manpower and material resources, as a result of no needs to the process of rice seedling, and can maintain production of rice.At present, China's rice planting area of more than 50% of hybrid rice. Super hybrid rice is a kind of hybrid rice and the tillering ability is stronger than the general hybrid rice. Due to the characteristic of high tillering capacity of super hybrid rice, the sowing quantity is required to be(1~3) seeds for each hill when super hybrid rice seeds are direct seeded to the field by drilling machine, for ensuring high rate of field seed ling emergence and high precision of seeding. Compared to rice mechanistic metering device, rice pneumatic metering device feature were high precision of seed metering, low seed- injuring rate and not demand of seed shape. Rice pneumatic metering device suited direct seed of super hybrid rice seeds.This text was aimed at requirement of practical production of super hybrid rice. Improvement and optimization of rice pneumatic seed metering device developed by South China Agricultural University. With the comb ination of theory and experiment, the precision of seed metering device is used as the performance evaluation index, and the core work unit-rice pneumatic seed metering device is studied. The main research contents include:A method for improving the liquidity of seeds in filling seed room was proposed. A filling seed stratified room was designed, which is between the seed-metering device and seed box. Indic hybrid “Peizataifeng” was taken as research subjects in this article. The impacts of the filling seed stratified room on performance of the pneumatic feed mechanism was studied by single factor experiment and orthogonal experiment. The optimization condition included that the sucking plate rotation speed was 30 r/min, the negative pressure for seeds sucked was 1.6 k Pa and positive pressure for seeds blew was 0.1 k Pa. With the filling seed stratified room, the probability of(1~3) seeds per hill of the metering device was 95.4%; in addition the empty seeds probability was 1.53%, and ?4 seeds probability was 3.07%. Under same conditions, the probability of 1 seeds per hill of the metering device was 17.32%; in addition the 2 seeds probability was 58.72% and 3 seeds probability was 19.36%. The results showed that the filling seed stratified room had a good influence on the precision of the pneumatic seed- metering device, improved the fluidity of seeds and decreased the friction and extrusion force among seeds. Thus the device enhanced adsorption capacity of seed plate act on seed. This study was an important reference basis for the pneumatic metering device on the performance improvements of precision and stability of seeding.The high speed photographic technique was used to observe and st udy the carrying seed area of the rice pneumatic seed metering device. It was found that a kind of "Early dropping seeds" phenomenon which affects the precision and the hole forming of the seed metering. In order to solve the effect of this phenomenon on t he seed metering device, a kind of shield device was proposed.This paper analyzes the causes of "Early dropping seeds" phenomenon from the perspective of theory, and established a mechanical model for “Early dropping seeds" phenomenon. According to the mechanical model and actual size of rice, the size parameters of shield device were determined. Indic hybrid "Peizataifeng" was taken as research subjects in this article. The probability of “Early dropping seeds” phenomenon occurring was studied by contrast experiment. The precision of rice pneumatic seed metering device was studied by multi- factor experiment, under different negative pressure for seeds sucked and rotation rates. The experimental results showed the range and the probability of “Early dropping seeds” phenomenon had been decreased with a shield device, the precision and the hole forming of seed metering had been improved with a shield device. The optimization condition included that the sucking plate rotation speeds were 25r/min~40r/min and the negative pressure for seeds sucked was 1.6k Pa. The probability of(1~3) seeds was 93%~97%.The experimental results show that the device can control the drop range of "Early dropping seeds", and make a part of "Early dropping seeds" fall back to the filling seed room, thus improving the precision of the seed metering device.The dropping trajectory of the rice pneumatic seed metering device was analyzed. The variation law and its influencing factors of the dropping trajectory are studied. And the diameters of hill sowing was measured. By means of the theoretical equation of the mean value of the actual trajectory, the optimization equation is obtained. Indic hybrid “Peizataifeng” was taken as research subject in this article, the dropping trajectories and diameters of hill sowing were analyzed by multi- factor experiment under different rotation rates and positive pressures for blowing seeds. This proposed structure designed parameters of rice pneumatic metering device tube as the basis, provided a reference for the design of rice pneumatic metering device optimal hill sowing condition and metering tube.A pneumatic rice hill-drop drilling machine was designed by using the optimized rice pneumatic seed metering device, and the design of the pipeline was carried out. Indic hybrid “Peizataifeng” was taken as research subject in this article, and carried out experiments in the field. The test results show that when the negative pressure is 2000 Pa and regardless of the high school low speed forward, the qualified rate can be stabilized at 95% or so, and the empty seeds probability is less than 2%. Indic hybrid “wufengyou” was taken as research subject in this field experiment, the test results show that hill-drop drilling machine also had better effect on “wufengyou”. Through laboratory germination rate and field emergence rate compared, analysis of the pneumatic rice hill-drop drilling machine field emergence situation, further validation of the pneumatic rice hill-drop drilling machine application feasibility, for a pneumatic rice hill-drop drilling machine research and application provides the basis.