Design and experiment of the fertilizer centrifugal broadcaster with guiding chute for paddy field

Rice is one of the most significant crops in the world. Enough fertilizer supplied in the different growing period is necessary for the growth and yield of rice. Manual spreading is still the main way of paddy topdressing in China, leading to the inefficient and uneven application. A topdressing machine can be expected to reduce the labor intensity for the high productivity. Among them, the large spreading distance can be required for the mechanical spreading of fertilizer, in order to reduce the running times of the machine in paddy fields. Furthermore, the broken rate is the main influencing factor on the broadcasting distance. In this study, an experimental centrifugal disc fertilizer broadcaster with a guiding chute was designed for the parameter optimization of the machine, in order to increase the spreading range with the less breakage rate of the fertilizer. The broadcaster consisted of a revolving disc with the guiding blades, a feeding part, and a guiding chute. The spreading distance increased to combine the action of centrifugal force and airflow speed. The kinetic analysis of fertilizer grains was carried out to establish a functional relationship between spreading distance and fertilizer particle velocity. The structure and motion parameters of the device were determined, according to the models. The speed of the disc was determined as 850 r/min, the length of the guiding blade as 160 mm, and the distance between the feeding tube and the center of the disc as 90 mm. The fertilizer spreading was simulated using EDEM software. A systematic investigation was conducted to reveal the influence of structural parameters of fertilizer applicator guiding blade and the location of the chute on the initial speed of fertilizer particles. The guiding blade of the disc was determined to be the radial type. The internal airflow field of the fertilizer broadcaster was simulated using FLUENT, in order to clarify the influence of the fertilizer spreader guide tube on the fertilizer particle speed off the guiding chute. The structural parameters of the guide chute were optimized to be 200 mm of the length, 60 mm of the height, and 91.38° of the slope angle of guiding chute. The angle between the feeding tube and guiding chute was 53.75°. The fertilizer particles shared the higher speed at the leaving the guiding chute. The orthogonal experiment of four factors with three levels was conducted to evaluate the effects of blade number, blade form, blade height, and disc-chamber gap on the spreading distance and breakage rate of fertilizer grains. The optimization demonstrated that the distance was 16.95 m, and the fertilizer broken rate was 26.32%, which was 28.2 % lower than that of ordinary fertilizer broadcaster. As such, the fertilizer spreading distance increased by 5 m at the number of blades was 4, the blade type was radial, the height was 15 mm, and the disc-chamber gap was 25 mm. The finding can provide a strong reference for the development of fertilizer application device.