Design and experiment of active rotating collective straw-cleaner

Abstract: Straw mulching has been the essential component of conservation tillage to prevent wind-water erosion and degradation of soil, while improving soil fertility and drought resistance. However, a low cleaning rate of straw often occurs in the current passive straw cutting/cleaning for the seed belt in Northeast China. In an active straw cleaner, there is excessive soil disturbance with the mixed burial of straw and soil damage to the moisture, thereby reducing the emergence rate in no-tillage maize seeding. In this study, an active rotating collective straw-cleaner was designed to solve the existing problems in straw mulching for no-tillage agriculture. The straw-cleaner was mainly composed of the spring teeth of straw cleaning, frame of spring teeth, drive motor, adjustment rod of height and inclined angle, adjustment plate of deflection angle, and curtain component. Six spring teeth were included in a straw-cleaner, where the tooth pitch of spring teeth was 60 mm, and the angle to the ground was 45°. The spring teeth were installed on the same rotating plane through the mounting frame. Specifically, the maximum gyration radius of the spring tooth was 200 mm, while the forward inclination angle was 20°, and the adjustment range of the slip angle was 20°-60°. The motor drove the spring tooth during the seeding. The spring tooth first penetrated to the soil from the side of the seeding belt, and then threw the straw to the other side along the tangent direction to the curtain component. A quadratic regression rotation orthogonal test was carried out to determine the optimal parameter combination, where the unit forward speed, the rotate speed, and penetration length of spring tooth were selected as determinants with the cleaning rate of straw as the performance index. A regression model was established for the test indicators and influencing factors of straw cleaning. A soil-bin test showed that the cleaning rate of straw was significantly reduced with the increase of forward speed in the initial stage, but the effect of forward speed on the straw cleaning was weakening with the increase in penetration length of the spring tooth. The forward speed contributed to the further improvement of the cleaning rate till greater than a critical value. The cleaning rate of straw increased first and then decreased as the penetration length of the spring teeth increased. The step distance of a single spring tooth decreased, whereas, the cleaning rate of straw showed a significant increase in the initial stage when the rotate speed of the spring tooth increased. However, the rotate speed of the spring tooth showed a relatively weak effect, even to limit the further improvement of cleaning rate, as the penetration length increased. An optimal combination of parameters was achieved for the best performance of the device in the Design-Expert 10.0.7, where the unit forward speed was 1.4 m/s, the rotate speed was 400 r/min, and the penetration length of the spring tooth was 19 mm. Field experiments demonstrated that the cleaning rate of straw for the 20 cm wide belts was 98.3%, and the working power was 605 W under the optimal combination of parameters, indicating a high agronomic requirement of no-tillage maize seeding in Northeast China. This finding can provide insightful technical support to the straw cleaning device for no-tillage machines.