Abstract:
The rice mechanized planting level is low in China. The ordinary hybrid rice and the super hybrid rice of high yield population structure can be formed with only 3-5 and 1-3 seeds per hill, respectively. The pneumatic rice precision direct seeding technique is a combination of machinery and air flow. To meet the cultivation requirements of different varieties and seeding rate of hybrid rice, a rice pneumatic seeding metering device with adjustable seeding rate was designed in this study. The working principle of seed metering device was analyzed. This seed metering device adopted multiple independent negative pressure flow-path to control the accuracy of seed suction. The influence of independent negative pressure flow-path structure on suction hole negative pressure was analyzed by ANSYS-FLUENT software. The key components of seed metering device with adjustable seeding rate were designed. The method of adjusting seeding rate was explained. The super hybrid rice Y-2 You 900 was selected as the test object. The average size of the seed was 8.90 mm× 2.20 mm×1.84 mm (length × width × thickness), and the weight of 1 000 grains was 23.8 g. The seeds were washed by water to remove impurities and blighted grain. The dry seeds were soaked in clear water for 24 h. Then, they were moistened, filtered out and dried. The average moisture content was 24.3% (wet basis) before the test. The whole factor experiments were carried out under different negative pressures, rotational speeds of the suction plates, and group number of suction holes. The results showed that when the negative pressure was 1.6 kPa, the optimal group number of suction holes was 12, and rotational speed of the sucking plate was 20 r/min, the optimal qualified rate of 1 hole was 82.41%; when the negative pressure was 1.6 kPa, the optimal group number of suction holes was 12, and rotational speed of the sucking plate was 40 r/min, the optimal qualified rate of 2 holes was 96.36%; when the negative pressure was 1.6 kPa, the optimal group number of suction holes was 12, and rotational speed of the sucking plate was 20 r/min, the optimal qualified rate of 3 holes was 92.79% ; when the negative pressure was 1.2 kPa, the optimal group number of suction holes was 16, and rotational speed of the sucking plate was 20 r/min, the optimal qualified rate of 4 holes was 91.93% ; when the negative pressure was 1.6 kPa, the optimal group number of suction holes was 12, and rotational speed of the sucking plate was 30 r/min, the optimal qualified rate of 5 holes was 87.88%. It also showed that a rice pneumatic seeding metering device with adjustable seeding rate could meet the requirements of different seeding rate for hybrid rice in direct seeding. Compared with the original seed metering device, this seeding metering device is more suitable to rice diversity, which provides a certain reference for rice mechanized direct seeding technology.