تعيين برخي خواص فيزيكي و مكانيكي يونجه آسياب شده

چكيده انگليسي :

Abstract Physical and mechanical properties of alfalfa grind are required for optimum designing of equipmentsthat are being used in transporting processing storage and size reduction of the crop Understanding theenergy requirement for alfalfa size reduction would be important for downstream processing such asdensification This study was conducted to determine the effect of particle size 2 38 3 36 and 4 76 mm and moisture content 8 9 3 and 11 w b on bulk density coefficient of static friction angle of repose coefficient of internal friction cohesion coefficient of wall friction and adhesion on polished steel ofalfalfa grinds Tests were conducted using factorial experiment in completely randomized design Cohesionand coefficient of internal friction with hammer mill screen sizes of 2 38 and 3 36 at moisture content of9 3 w b were determined at two different vertical load ranges Coefficient of internal friction andcohesion and adhesion on polished steel plat were determined using a direct shear tests coefficient of staticfriction was determined using a sloped surface Results showed that the particle size and moisture contenthad significant effect P 0 0001 on all measured physical and mechanical properties With an increase inmoisture content bulk density angle of reposes coefficient of static friction and cohesion increased whereas coefficient of internal friction and adhesion decreased With an increase in particle size the bulkdensity cohesion and adhesion were decreased while the other properties were increased The values ofstrength parameters depended upon the range of normal stresses used in the tests The bulk density ofalfalfa grind varied from 161 6 to 202 2 kg m 3 The coefficient of static friction against three surfaceschanged from 0 34 to 0 87 the highest and lowest values were obtained on rubberand Plexiglas surfacerespectively Larger particle with higher moisture content had the highest angle of repose 54 5 Thealfalfa grind prepared with the 2 38 mm screen size at moisture content of 11 w b and 4 76 mm screensize at moisture content of 8 w b had the highest and lowest cohesion 7 65 and 4 80 kPa respectively Alfalfa bales were chopped using a chopper equipped with a screen size of 20 mm The alfalfa chopswere then divided into three portions The first portion was left un sieved whereas the second and thirdportions were passed through 18 and 15 mm sieve sizes respectively Each portion was ground separately using a hammer mill with four different screen sizes 1 68 2 38 3 36 and 4 76 mm Energy data werecollected using a developed Wattmeter and a data acquisition system Effect of four grind sizes for eachsize of alfalfa chop was considered using a completely randomized design Results showed that the screensize in the hammer mill had significant effect P 0 0001 on each size of alfalfa chop Comparison ofmeans revealed a significant effect P 0 05 on energy consumption for all three sizes of the alfalfa chops The 20 and 15 mm alfalfa chops at 7 0 w b had the highest and lowest specific energy 31 41 and 4 61 kJkg 1 respectively The data of specific energy versus hammer mill screen size was best fitted R2 0 75 with Rittinger model The research results could be used in practical applications such as designing an idealalfalfa size reduction apparatus for energy efficiency and better economics Key words Alfalfa grind cohesion adhesion size reduction specific energy

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تعيين برخي خواص فيزيكي و مكانيكي يونجه آسياب شده

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