Development and performance evaluation of spice thresher on mustard (Brassica nigra L.) crop and its vibration analysis
Loading...
Date
2016-08
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Threshing is a process of loosening and separating of seeds from ear-heads by continuous beating or rubbing action. The traditional methods of threshing include more time consumption, labour, intensive losses which are significantly reduced by mechanization. The design factor and performance parameters of existing spice thresher were studied and modifications were made to attain a thresher with higher cleaning efficiency and reduced vibrations. The modifications were made on lower concave, cleaning unit, blower assembly according to the physical properties of mustard seeds. The spice thresher was fabricated with design modifications in Department of Farm Machinery and Power Engineering, GBPUA&T, Pantnagar. The physical properties were important factor in deciding the design parameters for thresher and were determined with two levels of moisture content. The length and width of mustard seeds were 1.485 mm and 1.286 mm for 6.25% moisture content and 1.472 mm and 1.457 mm at 9.04% moisture contents. The arithmetic mean diameter increased from 1.342 mm to 1.393 mm and geometric mean diameter from 1.297 mm to 1.344 mm as the moisture content increased from 6.25% to 9.04%.The surface area and volume were 5.343 mm2 and 1.459 mm3 at 6.25% moisture content and 6.0081 mm2 and 1.640 mm3 at 9.04% moisture content. The sphericity of mustard seed was 0.977 and 0.989 at 6.25% and 9.04% moisture content level, respectively. The performance parameters of thresher in terms of sieve loss, visible seed damage, threshing efficiency, cleaning efficiency, output capacity and power consumption were evaluated for different combinations of four cylinder peripheral speeds 4.5 m/s (287 rpm), 6 m/s (382 rpm), 7.5 m/s (478 rpm), 9 m/s (573 rpm) and four cylinder-concave clearances 5 mm, 7 mm, 9 mm, 11 mm. The maximum and minimum sieve loss was 1.30% and 1.05% with mean value as 1.184% 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 for increase in cylinder peripheral speed and decrease in cylinder-concave clearance with 98.89% maximum value at 9 m/s speed and 5 mm cylinder-concave clearance. The maximum output capacity was 30.843 kg/h for 9 m/s cylinder peripheral speed and 5 mm cylinder-concave clearance. Maximum power consumption was 0.994 kWh at 9 m/s cylinder speed and 5 mm concave clearance. The vibration amplitudes were measured in horizontal and vertical directions at eight functionally critical positions of thresher for four cylinder peripheral speeds 4.5 m/s, 6 m/s, 7.5 m/s and 9 m/s. The maximum vibration amplitude at No-load condition (without crop feeding) was 23.91 m/s2 for 9/s cylinder speed at position on lower frame was reduced to 19.72 m/s2 by constraining the frame to a fixed position. The vibration amplitudes were further minimized significantly by application of isolators at base of threshing shaft bearings, counter shaft bearings and motor for fixed condition of frame at No-load. The maximum vibration with application of 4 mm and 8 mm rubber sheet isolators at no-load with fixed frame was 21.69 m/s2 and 17.63 m/s2, respectively at position on lower frame. The vibration amplitudes increased at four positions with addition of 10 kg dead weight to lower frame. At Noload, the vibration amplitudes were minimum for 8 mm rubber sheet at bearings and motor base with fixed frame so this condition was selected as optimum condition and vibrations were analyzed at this condition with a constant feed rate of 60 kg/h of mustard crop. The maximum and minimum vibrations of thresher were 18.7 m/s2 and 6.3 m/s2 with crop feeding. The optimum speed range for threshing of mustard crop was 5 m/s to 6 m/s according to mathematical analysis using maxima and minima. The six basic natural frequencies and their responses (in terms of deformation) were evaluated using ANSYS and deformation was reduced to zero at lower position of frame as the frame is constraint to a fixed position. The maximum deformation was 0.585 m as the frame is free to move and 0.572 m as frame is constraint to a fixed location.
Description
Keywords
null