Development and experiments on reel with improved tine trajectory for harvesting oilseed rape

Highlights

• Designed an reel with improved tine trajectory suitable for harvesting rapeseed.

• Simulation analysis proved the improved reel is more favorable for rape harvest.

• Field comparative experiments proved the improved reel has a lower header loss.

Crops with branching characteristics, such as rapeseed, are difficult to harvest owing to their specific plant geometry. To solve this problem, an harvesting reel with improved tine trajectory, considering the reel working process and a function suitable for oilseed rape, is proposed in this study. The improved tine, of which angle can be continuously adjusted to adapt to the plant structure and meet the operating requirements of the reel in the stages of pushing the reel into the crops, feeding plants into the auger, and releasing the reel. The kinematics of the tine trajectory between the new and standard reels were calculated and a simulation comparative analysis was performed, which proved that the new reel satisfies the theoretical requirements. Single-factor field experiments were conducted for the two types of reels. The test results demonstrated that the proposed reel has a lower header loss rate and is significantly affected by the reel speed than the reel height or machine forward speed. According to the multivariate orthogonal results, the combination of optimal parameters with minimum loss rate yielded a reel rotational speed of 1.88 rad s⁻¹, machine speed of 0.6 m s⁻¹, and reel vertical height of 1100 mm. The actual loss rate was found to authentically decrease to 1.04% in the supplementary field test under this condition, which verified that the parameters are reasonable. This study combines experiments and trajectory analysis to explain the advantages of the improved reel and provide a new study direction of reducing rapeseed harvesting losses.

Introduction

Rapeseed is one of the main oil crops in the world. It plays a significant role in food and other industries. The crop has a specific plant geometry with multiple branches that look like a tree (Kumar, Falk, Ratanapariyanuch, & Reaney, 2016; Shim, Sharma, & Upadhyaya, 2017). Additionally, the rapeseed pods mature at different rates and can crack easily, thereby resulting in aggravating losses. These features complicate the harvesting of this crop. Manual harvesting is time-consuming and labour intensive. However, it is difficult to implement and popularise mechanized harvesting owing to its high loss rate. These problems result in a reduction in rapeseed plantation area per year, which pose a significant threat to oil crops (Bruce, Farrent, Morgan, & Child, 2002; Kadkol, Macmillan, Burrow, & Halloran, 1984; Squires, Gruwel, Zhou, Sokhansanj, & Abrams, 2003).

Currently, because there is a lack of research on developing a rape harvester based on rapeseed characteristics, rapeseed is mostly harvested by modifying the harvester for rice and wheat, which does not conform to the rape plant structure. Different from rice or wheat, the structure of rapeseed is large and tall with several branches. Furthermore, mature rape pods are fragile and can be easily cracked owing to external forces, especially by the harvester header, which causes massive pod shattering losses, accounting for more than half of the total loss incurred in this domain (Li, 2005; Stephenson, Stacey, Brüser, & Pullen, 2019; Wu, Liu, & Li., 2005). Many studies have worked toward solving this problem to decrease header loss. For example, designers usually install a vertical cutter on the right side of the harvester header to separate the plants, considering that rapeseed has numerous branches and intersections. Discussions regarding the cutter have dominated the research in this field in recent years. Dong and He (2008) exploited a vertical cutter, transmission way, installation height, and cutting frequency. Moreover, a comparison experiment was conducted on harvesters with two different platform extensions and a standard head. The results proved that replacing the mechanical system with hydraulic system and using double vertical cutter bar instead of a single cutter bar helps in reducing the amount of grain loss (Asoodar, Izadinia, & Desbiolles, 2012). In addition, some researchers used balanced and less vibrant disc cutters instead of reciprocating cutters to reduce the pod drop due to vibration shock (Li, Xie, Liu, & Tang, 2014; Zhang & Huang, 2008) in an attempt to avoid the resonance vibration between the head and cutter bar when harvesting. Li, Li, and Xu (2014) optimised the structure parameters of the head frame. Other aspect studies have also been conducted. Hobson and Bruce (2002) proposed to retrofit a conveyor behind the main cutter to assist the flow of rape stalks into the head auger. Pari, Assire, Alessandro, and Vincenzo (2012) explored the influence of rainfall and temperature on Italian rapeseed harvesting at maturity and experimentally analysed amount of loss in different sections of the harvester during mechanical harvesting.

The harvester reel is located in front of the combine harvester to ensure that the crops stay straight during cutting and the plants are fed into the header. Tined reel is generally a uniform standard part of the harvester whose most commonly applied structural form is of eccentric type. For the reel, Zareei, Pour, Moghaddam, and Sahrayan (2012) performed experiments on factors such as the harvester forward speed, horizontal and vertical distance between the reel and the main cutter, and the impact of reel rotational speed on the header loss to determine the optimum adjustment position of the header component. Furthermore, Moses, Thomas, and Jun (2012) redesigned the kinematics of the tine to improve the pick-up performance in response to the problem of crops being easily stagnated and tangled.

Prior research works thoroughly investigated the cutting knife and the improvements in header parameters. The reel is installed horizontally at the front of the header, and the tine on the reel is the first working part that directly contacts the branches and pods of rape. When the tine excessively collides and contacts rape during the movement, the resulting disturbance and impact force between plants easily make the pod crack rapidly, leading to a large amount of lost rapeseed. However, to the best of our knowledge, not many studies on rape harvester header have factored the morphological and biological characteristics of rapeseed. In this study, we considered the unique plant geometry and features of rapeseed, combining the working process and the function of the reel, to cut down the attack of reel tine on rapeseed and reduce the loss of header by analysing the trajectory of tine suitable for rapeseed harvesting. Based on this, a reel specifically designed for oilseed rape with an improved tine trajectory was developed and the results of tine trajectory and field tests were compared with those of a standard reel.