طراحي، ساخت و ارزيابي دستگاه قطعه ساز يونجه به منظور دست يابي به دانسيته بهينه در بسته بندي

چكيده انگليسي :

111 Design Fabrication and Evaluation of an Alfalfa Chopping Unit for Optimum Bale Density Formation Ali Taherabadi ali taheri14@yahoo com February 20 2012 Department of Agriculture Machinery Engineering Isfahan University of Technology 84156 83111 Iran Degree M Sc Language Farsi Supervisors A A Masoumi masoumi@cc iut ac ir Abstract In the process of forage balling operation higher density achievement for produced bales always hasbeen considered In this study increase in bale density by size reduction of alfalfa stems was considered Optimum bale density according to previous research was determined based on percent moisture contentand bulk density Alfalfa size reduction as a procedure to decrease maximum compressing force in balingmachines was considered to produce bales with higher densities To achieve this aim a prototype chopperdevice of cylindrical type with two cutter knives was designed fabricated and evaluated The machinewas designed based on engineering considerations as a unit which can be attached to a windrower According to flow rate of materials and inlet width space in windrower three alfalfa chopping unitswould be used Since the power requirement of chopping unit was unknown in this study one prototypeunit was fabricated and evaluated The power and energy consumption and crop losses were determinedon a test rig Experiments were performed using a completely randomized design with three replications The ratio of shedding weight due to cutting by machine to initial weight of samples was measured andreported as crop loss Results showed that with increase in cylinder speed average length of cutting stemswere 35 24 and 15 centimeters for 83 125 and 167 cylinder RPM respectively These results werecomparable to calculations made in design procedure of machine Power consumption was determined bymeasurement of the electrical current consumed by the test rig electric motor for each experiment Theresults showed that with length reduction or with increase in speed of cylinder power and energyconsumption increased but no significant difference was observed Also the results showed that differencebetween the calculated losses in three tests were not significant For determination of machineperformance some mechanical and rheological properties of the alfalfa stems were determined Theconfined compression test was conducted on Hamadani alfalfa variety with 70 centimeter stems heightwith moisture content of 20 percent on a wet basis at four levels of length 25 33 50 and 100 ofprimary length The experiment was conducted in randomized complete design with three replications Inorder to achieve bales with 150 kg m3 of density the stress strain curve for each test was obtained and themaximum of compression force and time relaxation were determined Determination of relaxation timesis one of important parameters in forage balling and compression process Results showed that themaximum of compression force increased as stem length decreased so minimum corresponding value ofsamples in 25 of primary length was obtained According to LSD test the difference in maximumcompression forces were highly significant p 0 01 but relaxation time difference for various treatmentswas not significant Also the results showed that first relaxation times in all the samples were less than 5seconds The Maxwell model relationship between stress and relaxation time of viscoelastic products was fitted on data values with coefficient of determination of 0 99 and the constant parameters wereobtained Keywords compression relaxation time Maxwell model physical properties

طاهرآبادي، علي

طراحي، ساخت و ارزيابي دستگاه قطعه ساز يونجه به منظور دست يابي به دانسيته بهينه در بسته بندي

تراكم سازي , آسايش تنش , مدل ماكسول , خواص فيزيكي