Study On Combined Stalk-stubble Breaking And Mulching Machine

Agricultural mechanization is an important component part of agricultural modernization and an important measure for the development of efficient agriculture. The stalk-stubble breaking and mulching process is one of the core techniques for conservation tillage. It is gradually replacing the traditional moldboard plowing technique in the dry farming area of northern China. Comparing with the traditional moldboard plowing technique, the conservation tillage technique of stalk-stubble breaking and mulching can help reduce wind and water erosion of the soil, increase the soil organic matter content, improve the soil structure, increase soil fertility, and improve the ability of soil to retain and store water, achieving the goal of increasing crop yields. At present, two machines, the stalk-breaking machine and the stubble-breaking machine, have been widely adopted in the north of China. Both of the machines are needed to separately perform the stalk-breaking and stubble-breaking operations, thus increasing soil compaction due to needing repeated operations. The combined stalk-stubble breaking and mulching machine we developed can perform the stalk-stubble breaking and mulching at one time, so soil compaction is decreased. Through simple disassembly, this combined machine based on separated structure can be disassembled into a stalk-breaking machine and a stubble-breaking machine to perform the stalk breaking operation or the stubble breaking operation independently. One machine can be used for three purposes.This paper describes the design of the complete machine and key parts and the performance test and production verification results. The machine uses a separated structure, a symmetrical universal gearbox and a both–side counterbalancing transmission device to ensure that either combined operation or independent stalk-breaking operation or stubble-breaking operation can be performed. Two key parameters in the design of the combined machine are the height difference H between the stalk-breaking blade rotor and the stubble-breaking rotor in the vertical direction and the distance L between the two rotors in the longitudinal direction. In this paper, the relations between these two parameters with the turning radiuses of two rotors, stubble height and stubble-breaking depth are analyzed and mathematical expressions are presented. These two parameters are optimized through bench tests and the parameters of the center distance between two blade rotors and the main parameters of the stalk blade rotor and stubble-breaking rotor are determined. The design of the stalk-breaking rotor and stubble-breaking rotor, and reasonable arrangement methods of blades mounted on the discs are described. At present, there is no test method of the combined stalk-stubble breaking and mulching machine, so we established the test method of the combined machine referring to the standards for the machine-building industry of P. R. China, Smashed Straw Machine ( JB/T 6678-2001 ) and Smashed Root-Stubble Machine (JB/T8401.3-2001). The performance test and production verification of the combined machine were conducted.The study and test results reach the following conclusions:The combined stalk-stubble breaking and mulching machine is capable of performing combined operations, involving stalk-stubble breaking and mulching and partially burying the broken stalk and stubble at one time, meeting the agrotechnical requirements of soil water storage and conservation tillage. Performance tests show that the average broken stalk rate is 89.2% and the average broken stubble rate is 92.8%, better than the requirements stipulated in the national related standards. After the stalks and stubbles are broken and mulched on the ground, the soil moisture content within 10 cm depth can increase by about 10%.The height difference H between the stalk-breaking blade rotor and the stubble-breaking rotor in the vertical direction is related to the turning radiuses of two blade rotors, stubble height and stubble-breaking depth, and the distance L between the two blade rotors in the longitudinal direction is related to H, but mainly determined byα, the included angle between the absolute velocity V at the point at which the broken stalks are thrown out of the exit of the crushing chamber and the ground. Two blade rotors can be arranged reasonably by using the given formulas for H,αand L. Theoretic analysis and bench tests show thatαshould be within the range of 45°to 65°. In consideration of both ensuring the operational performance and minimizing the longitudinal distance of the machine, soα= 60°was selected.. Performance tests in the field and large–area production verification demonstrated that the parameters selected in the design meet the agrotechnical requirements. The blades mounting on the stubble-breaking rotor in multi-spiral arrangement significantly improve the stubble-breaking efficiency.In the design of the machine, advanced soil water storage and preservation techniques and combined operation technologies were adopted, and a new structure and a new transmission device were used. The complete machine and the key parts have innovativeness. The combined machine is characterized by high efficiency, low consumption, low cost, easy use, low failure rate and high utilization rate, meeting the agrotechnical requirements of conservation tillage.