Design and experiments of the circular arc progressive type harvester for the safflower filaments

A harvesting device has been normally used to cut the safflower filaments. However, there is a large damage to the structure of the filaments during harvesting, such as the high filament crushing rate and low harvesting net rate. It is a high demand to fundamentally reduce the filament crushing rate during this time. In this study, a circular-arc progressive harvesting device was designed to cut the safflower filament, particularly considering the material characteristics and mechanical properties of the safflower. A high harvesting efficiency was achieved to optimize the cutting tool of the filaments, thus reducing the filament breakage rate for the higher filament harvesting net rate. The key factors were then determined to promote the performance of filament harvesting, according to the operational requirements and integrity of safflower filaments. A systematic investigation was also made to optimize the force and cutting speed of the circular-arc progressive cutter. The optimal edge tilt angle and cutter speed were obtained to reduce the harvesting loss for the filament slip cutting. At the same time, a laser alignment sensing device was added as an auxiliary way to precisely position the high-efficiency cutting, especially for the better integrity of the filament cutting and the high net rate of filament harvesting. Furthermore, a wind pressure-fan speed model was established in the first stage, in order to explore the characteristics of the internal airflow and filament movement in the harvesting chamber. Specifically, the fan speed was adjusted concurrently, as the wind pressure changed during harvesting. Then, the flow field was simulated in the filament harvesting chamber under the fan speed using Fluent software, according to the structure and working principle of the negative-pressure collection system. The results show that the airflow field inside the chamber was relatively smooth, where the light filaments were carried over the tool to the collection box. The flow field of filaments was then verified by the internal structure design of the chamber. A secondary orthogonal rotational test was conducted to improve the working performance of the harvesting device, with the edge tilt angle, knife shaft speed, and fan speed as the influencing factors, while the net harvesting rate, breakage rate, and net collection rate as the response indicators. A mathematical model was also established using Design-Expert software. An optimal combination of parameters was obtained as follows: the cutting edge tilt angle of 25°, cutter shaft speed of 644 r/min, and fan speed of 2800 r/min, corresponding to the net extraction rate of 92.1%, breakage rate of 9.6%, and net collection rate of 94.7%. A verification test showed that the net extraction rate was 91.5% and the breakage rate was 9.8%. More importantly, the net harvesting rate was 91.5%, the breakage rate was 9.8%, and the net collection rate was 94.2%, with an error of no more than 5% from the optimized one. The optimal parameter was in the agreement with the actual situation of safflower harvesting, indicating the better integrity of safflower filament after harvesting. The performance experiments in the field demonstrated that the developed harvesting device effectively improved the net harvesting rate and net collection rate with a less breakage rate. This finding can provide the theoretical basis and technical reference for the high quality and low damage of safflower harvesting.