Abstract
Aim of study: Selecting a proper fan for the rice combine harvesters to get a good cleaning performance when harvesting high yield rice. Area of study: Jiangsu Province, China.Material and methods: Three potential multi-duct fans were designed, and the computational fluid dynamics and hot wire anemometer technology were utilized to learn the airflow and pressure variation inside the fan with perforated plates at the outlet ducts as cleaning loads. Then, the fan with the best performance was selected and a multi-duct cleaning test-bed was developed. The variation of the corresponding airflow velocity in the cleaning system was analyzed and the ideal airflow velocity in different section of the sieve was clarified. Finally, a field experiment was carried out.Main results: For a rice combine harvester with a feed rate of 7 kg/s (material other than grain + grain), the requested airflow rates inside the cleaning shoe was about 3.0 m3/s. The ideal airflow velocity in different section of the cleaning shoe was 8-9 m/s at upper duct, 4-6 m/s at the middle section, and 3-4 m/s at the tail section; large improvement in cleaning performance was achieved with the designed fan.Research highlights: The airflow velocity decreased as the cleaning loads at the duct increased. The fan with the averaged airflow velocity ≥7 m/s at the upper duct under different cleaning loads, and the airflow velocity at the lowest duct ≥ 9 m/s, is favorable for forming a blowing airflow in the tail sieve and is good for grain stratification.
Highlights
It is reported that the super rice planting area has risen to 9.067 million ha, accounts for approximately one-third of total crop planting area in China and the average rice yield climbs to 11250 kg/ha per harvesting (Yuan, 2017)
The currently used combine harvesters in China were designed according to rice with a yield ≤ 9000 kg/ha, Zhenwei Liang, Depeng Li, Jun Li and Kunpeng Tian and field experiment results indicated that those combine harvesters have poor cleaning performance when harvesting high yield rice (Li & Li, 2015)
Relevant research on cleaning structural improvement has been carried out: using Particle Image Velocimetry (PIV) system to analyze the airflow distribution in the cleaning system (Kenney et al, 2005); connecting the aerofoil and centrifugal blades together and expecting to suit for the threshed outputs distribution (Tang et al, 2007)
Summary
It is reported that the super rice planting area has risen to 9.067 million ha, accounts for approximately one-third of total crop planting area in China and the average rice yield climbs to 11250 kg/ha per harvesting (Yuan, 2017). The currently used combine harvesters in China were designed according to rice with a yield ≤ 9000 kg/ha, Zhenwei Liang, Depeng Li, Jun Li and Kunpeng Tian and field experiment results indicated that those combine harvesters have poor cleaning performance when harvesting high yield rice (Li & Li, 2015). A conical centrifugal fan was designed to adjust threshed output initial distribution on the sieve surface, and the cleaning performance was improved significantly in the transversal axis-flow combine harvester (Chen et al, 2009). A high power centrifugal fan with six blades was utilized in TC5060 axial-flow combine harvesters (New Holland), and field experiment results indicated that the cleaning system could spread the threshed outputs promptly, and the cleaning performance was improved with a stronger airflow power (Wu, 2014). Some multi-duct fans has been used in some flagship combine harvesters, such as Gleaner S8 combine harvester
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