Optimal design and experiment of 3SFBQ-500 type orchard gas explosion subsoiling and fertilizer injection machine

Abstract: At present in the orchard fertilization process, the most widely used method is ditching and fertilizing method. However, orchard ditching and fertilizing technology has a series of problems, such as easy damage to tree roots, high energy consumption and uneven fertilizing. Meanwhile, soil compaction frequently exists in orchard land due to no farming in long years, which is not beneficial for rainwater leakage and nutrient transport in soil, so there is a great need to develop a new kind of fertilization machine. In this context, a 3SFBQ-500 type gas explosion subsoiling and fertilizer injection machine was designed, which used high pressure gas to shock soil body and then injected fertilizer. The drill pipe mechanism with pneumatic chipping hammer excitation and hydraulic assistance was designed to drill the soil, and the maximum drilling depth reached 500 mm. The dynamical model and kinematical equation of soil drilling by pneumatic chipping hammer with hydraulic assistance were established, and force analysis of drill pipe during soil drilling process was performed. The drill bit structure parameters were optimized as taper angle of 60° and pipe radius of 12.5 mm. An economical multi-knob switch control system was made to improve the equipment automation degree and reduce the intensity of labor operations, which could make the machine operations controlled manually and automatically. The working processes of soil drilling, gas explosion subsoiling, liquid fertilizer injection and drill pipe rebound were completed in a key operation. Then the 3D (three-dimensional) model of the whole machine was established using SolidWorks software. On this foundation, the machine prototype was produced. Afterwards, field experiments were carried out, and the results showed that soil fractures were created by gas explosion. Under the condition of 0.8 MPa gas pressure and 300 mm drilling depth, the maximum breadth of fractures was about 3-4 mm, the extension disturbance radius of fractures about 400 mm. In addition, the soil perturbation happened after gas explosion, and the soil perturbation coefficient was 50.11%, which was calculated by gas-splitting soil fracture extension model of Murdoch L C. What was more, the liquid fertilizer was sprayed in deep soil with no stoppage and diffused uniformly in the role of high pressure pump. This new designed machine abandoned the traditional operation mode of first ditching, then fertilization, and then covering the soil, while adopted the new operation mode of gas explosion subsoiling and fertilizer injection. So the tree roots were not easily damaged and the fertilizer was evenly distributed, which was conducive to nutrient absorption of root in growth. The work efficiency was 0.048 hm2/h at least. What's more, with simple operation and stable performance, the new designed machine can meet the agronomic requirements of orchard, garden and city greening fertilization.