Influence of working order on working quality and power consumption of subsoiling and rotary tillage combined machine

Abstract: Subsoiling and rotary tillage combined cultivator is one of the most important tillage machines in China. In our study, discrete element method (DEM) simulation and field tests were conducted to analyze the influence of the sequence of rotary tillage and subsoiling operations on the combined operation process and power consumption, and a subsoiling and rotary tillage combined cultivator was selected as the test machine, which is commonly used in loam soil region in North China Plain. DEM simulation showed that soil movement was different between subsoiling - rotary tillage and rotary tillage - subsoiling operation under the same operating depth. To be specific, the working process of subsoiling - rotary tillage operation is subsoiling loosens the soil, and rotary tillage breaks the loose soil, while the working process of rotary tillage - subsoiling operation is rotary tillage breaks the soil, and subsoiling loosens the soil, which indicated that the rotary tillage - subsoiling operation is more compact. The initial state of the surface soil layer is different under the two operations during the work of the subsoiling and rotary tillage component. And the subsoiling - rotary tillage operation dealt with more deep soil layer than the rotary tillage - subsoiling operation when the working depth increased. The force on the rotor under the two different operations was measured. D1 is the rotary blade behind subsoiler in subsoiling-rotary operation; D2 is the rotary blade adjacent to D1; Under subsoiling - rotary tillage operation, the average horizontal resistance on blade D1 and D2 is 44.6 and 13.3 N, and the average vertical resistance is 29.7 and 16.3 N, respectively. The great difference on the force showed that the force on the rotor is uneven. Under rotary tillage - subsoiling operation, the average horizontal resistance on blade D3 and D4 is 86.7 and 87.6 N, and the average vertical resistance is 55.3 and 56.8 N, respectively. D3 and D4 are the rotary blade at the same location as D1 and D2 in rotary-subsoiling operation. The small difference on the force showed that the force on the rotor was even. Many experiments were conducted to build regression equation by using rotary tillage depth (8-20 cm) and subsoiling depth (25-45 cm) as the influence factors and energy consumption under 2 sequences of two operations as the evaluation indices. The results showed that the energy consumption under subsoiling - rotary tillage operation (13.90 kW) was less than that under the rotary tillage - subsoiling operation (17.98 kW) when the rotary tillage depth was 10 cm and subsoiling depth was 25 cm; the superior surface flatness under subsoiling - rotary tillage operation (15.42 mm) was better than that under the rotary tillage - subsoiling operation (23.87 mm); the vegetation cover rate under subsoiling - rotary tillage operation (84.10%) was also better than that under the rotary tillage - subsoiling operation (78.14%); the soil fluffy degree under subsoiling - rotary tillage operation (11.17%) was similar to that under the rotary tillage - subsoiling operation (10.33%). When the rotary tillage depth was 20 cm and subsoiling depth was 45 cm, the energy consumption under subsoiling - rotary tillage operation was 9.35 kW higher than that under the rotary tillage - subsoiling operation; the superior surface flatness, vegetation cover rate and soil fluffy degree under subsoiling - rotary tillage operation and rotary tillage - subsoiling operation were 2.33 mm, 19.97%, 96.74% and 2.95 mm, 20.24%, 97.28%, respectively, which showed little difference between these 2 operations. According to the results comparison between field tests and simulation analysis, the simulation for the working process of 2 operation sequences, as well as the regression model of the power consumption was able to reflect the practical field operation. The vibration acceleration of the machine under rotary tillage - subsoiling operation was lower than that under the subsoiling - rotary tillage operation, which indicated that the force on the rotor was even under rotary tillage - subsoiling operation. This study can provide a further direction for the optimization of subsoiling and rotary tillage combined cultivator in loam soil region in North China Plain.