Design and development of aspirator blower for spice thresher and performance evaluation of the developed thresher on fenugreek crop
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Date
2018-08
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
A thresher is an agricultural machine which separates the seeds and the husk. The power operated threshers are almost a boon to the farmers as the time required for threshing is particularly less when compared with the traditional techniques like animal and human treading, beating on wooden block etc. Everywhere throughout the world, the quickly developing food industry depends to a great extent on spices for taste and flavor creators. India is the largest producer of fenugreek. During 2015-16, its production was 299 million tonnes of seeds out of an area of 211 hectares. Even after lots of development there is no thresher particularly for spices. The design factors and performance parameters of existing thresher were studied and lower concave, sieve and blower assembly were developed according to the physical properties of fenugreek seeds to attain a thresher with higher cleaning efficiency. The cleaning unit of spice thresher was designed and developed and other modifications were done at the Department of Farm Machinery and Power Engineering, GBPUA&T, Pantnagar. The physical properties of fenugreek seed were important factor in deciding the design parameters of thresher and were determined with two levels of moisture contents, varying from 5.16% to 8.33% (w.b.). The length, width and thickness of fenugreek seeds were 3.26 mm, 2.01 mm, 1.53 mm, respectively at 5.16 % moisture content and 4.16 mm, 2.81 mm, 2.33 mm, respectively at 8.33% moisture content. The arithmetic mean diameter increased from 2.26 to 3.06 mm and geometric mean diameter from 2.15 to 2.98 mm as the moisture content increased from 5.16 % to 8.33 %. The surface area and volume were 14.54 mm2 and 3.61 mm3 at 5.16 % moisture content and 27.90 mm2 and 10.19 mm3 at 8.33 % moisture content. The sphericity of fenugreek seeds was 0.66 and 0.74 at 5.16 % and 8.33 % moisture content level, respectively. One thousand seed weight increased linearly from 9.67 g to 12.13 g. the bulk density and true density decreased non- linearly from 0.769 g/cm3 to 0.745 g/ cm3 and 1.316 g/cm3 to 1.294 g/cm3, with increase in moisture content from 5.16 % to 8.33 %. Also, the value of porosity for the seeds increased from 41.60 % to 42.42 %. The static coefficient of friction increased nonlinearly from 0.36 to 0.51 with increase in moisture content. Perimeter and angle of repose increased linearly from 8.95 mm to 10.05 and 38.28 to 41.16, respectively with increase in moisture content. The performance parameters of thresher in terms of sieve loss, cylinder loss, visible seed damage, threshing efficiency, cleaning efficiency, output capacity and power consumption were evaluated for different combinations of four cylinder peripheral speeds (6.27 m/s, 7.5 m/s, 9 m/s and 12.10 m/s) and four concave clearances (8mm, 14mm, 20 mm, 26 mm). The mean values of sieve loss and cylinder loss was 0.13 % and 1.27 %, respectively for different treatments. The visible seed damage was negligible and threshing efficiency was 99.9 % for all combinations of cylinder peripheral speeds and concave clearances. The cleaning efficiency was increased with increase in cylinder peripheral speed and decrease in concave clearance with 95.69 % maximum value at 9 m/s speed and 14 mm concave clearance, when fan having forward inclined blades was used as the blower. After attaching aspirator blower and providing the speed of 9 m/s to threshing cylinder with 14 mm concave clearance, for the samples received during threshing when fan blower was used, the cleaning efficiency increased significantly and the average value was 98.57 % for all the samples. The maximum output capacity was 48.26 kg/h for 12.10 m/s threshing cylinder speed and 8 mm concave- clearance. Maximum power consumption was 1.059 kW for 12.10 m/s speed and 8 mm concave- clearance. The best results were found at 9 m/s peripheral speed and 14 mm concave- clearance with 99.9 % and 98.88 % threshing and cleaning efficiency, respectively and minimum total losses.
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