Assessment of Sieve Slope, Sieve Range and Fan Suction on Cleaning Efficiency and Loss Rate of Peanut Thresher

Peanut (Arachis hypogaea L.) is an annual plant of the legume genus that is cultivated in 109 countries due to its high-quality oil and seed protein. In Iran, this crop is cultivated on an area of 3000 hectares, with an average yield of 4 tons per hectare. Threshing performance significantly affects seed loss and physical damage, including cracking and crushing of seeds during harvest. Therefore, over the last century, extensive research has been conducted on different types of threshing methods, as well as the design and development of various threshing machines.Research on seed crops such as cereals and seeds suggest that factors such as the rotational speed of the thresher, threshing-concave distance, feeding rate, and shape of threshing teeth play a crucial role in determining the threshing efficiency and quality of the threshed seeds. Although limited research has been conducted on peanut threshing, there are currently no combine-machines available for this crop on global markets. Therefore, this study aims to investigate several working parameters of an experimental peanut thresher, including the effect of sieve angle, sieve range of movement, and suction speed on the separation unit.

The relevant experiments were conducted in the Parsabad Moghan region of Ardabil province (latitude 39.65 North, longitude 47.91 East). To conduct the experiments and separate the seeds from the pods, we used a peanut threshing machine cultivar Nc2, which is commonly cultivated under agricultural conditions in Ardabil and Gilan Agricultural Research Centers.To achieve the aims of this research, we investigated several effective parameters in the performance of the machine, including sieve angle, sieve movement range, and fan suction speed, to obtain the best settings for maximum threshing performance and separation efficiency. It is worth noting that the average seed weight per kilogram of peanut plant was between 300-400 grams, and the moisture content of the seeds in the tested cultivar was 45%. Before using the machine, workers must first dig up the plants and place them on the ground in a coupe, after which another worker must feed the plants into the machine through the feeder.

The study found that changes in sieve angle, sieve movement range, and suction speed significantly affect the separation efficiency and peanut loss rate at a 1% significance level. Increasing the sieving angle leads to a higher speed of material movement on the sieve, which results in insufficient time for separating straw from the seed. Similarly, increasing the sieve movement range causes a rapid decrease in cleaning efficiency. To achieve better straw-seed separation, it is necessary to apply impact shocks to the products located on the sieve within a short period. However, as the range of movement increases, the time interval between impact shocks also increases, which disrupts the straw's separation from the seed.The study found that increasing the sieve range and suction speed leads to a higher rate of peanut loss. This is due to the fact that when the suction speed and sieve movement range are increased, the product spends less time on the sieve, which results in insufficient time for proper separation. Additionally, high speed may exceed the limit of peanut seed and cause it to move out of the machine with the straw. Increasing the sieve movement range leads to a more uniform movement of straw and seed on the sieve; however, achieving better separation of straw from the sieve requires dynamic shocks and sudden acceleration, which decreases as the sieve movement range increases. The optimal farm capacity and material capacity were achieved with a 5-degree slope at 0.55 hectares per hour and 509 kilograms per hectare, respectively, using a sieve range of 3.5 centimeters and a fan suction speed of 8 meters per second.

The study concluded that the sieve movement range has the most significant impact on cleaning efficiency, while the sieve angle has the least effect. Similarly, the sieve movement range has the most significant influence on the rate of peanut loss, while the sieve angle has the least effect.