نشریه مهندسی بیوسیستم ایران
سال چهلم شماره 2 (پاییز و زمستان 1388)

To reduce the storing space and handling costs for hay/straw bales, recompressing the original bales after adequate hay drying is recommended. In this project, a recompression machine was designed, constructed and evaluated. Solidwork and Nastran software were employed to model, and to analyze the stresses in the components of the machine, respectively. The components of the machine consisted of baling chamber, ram and discharge chamber, designed as based on some physical and rheological properties of the hay/straw bales. The effect of compression levels (30, 40 and 50% strain) on the recovery length of the recompressed alfalfa/straw bales (in relaxation chamber) were investigated using a factorial experiment of a randomized complete block design. The effect of recompression level and crop type on length recovery of bales (in the relaxation chamber) was significant (P<0.01). The results showed that the recompressed alfalfa/straw bales of 50% reduction in initial length had the highest length recovery in the relaxation chamber. Therefore, to achieve a desired length reduction for hay/straw bales, it is recommended that an additional strain be applied during the recompression process in order to compensate for the expected length recovery.

Using instrumented tractors to monitor and record spatial variations in performance parameters of tractor and implements during field operations, could improve productivity and the tractor efficiency. In the context of precision farming, this information can be used to map spatial variability of the parameters and to find the relations with changes in soil attributes (texture, moisture contents and degree of compactness) within a field. The objective of the research was to evaluate the tractor-implement performance parameters by equipping a Massey-Ferguson (MF-285) tractor with sensors to measure travel and engine speeds, wheel rpm and fuel consumption of the tractor, as well the draft of mounted implements. A Global Positioning System (GPS) receiver was also installed on the tractor. In order to display and collect data from the sensors, a data acquisition system was developed for the purpose. Appropriate methods were adopted to calibrate the sensors. A three-point hitch dynamometer which was developed previously at the Department of Farm Machinery, Isfahan University of Technology was calibrated in the field, employing RNAM method. Comparison of tractor wheel speeds with the fifth wheel revealed that the driven rear wheels and the non-driven front wheels had slip and skid respectively. The results showed that the fifth wheel and the non-driven front wheels are appropriate devices for a close estimation of the tractor travel speed. In a majority of the cases, the GPS accurately receiver indicated the tractor travel speed, however, due to the existence of obstacles on either side of the testing routes and the type of receiver employed, there was some jumping observed the recorded speed values. Therefore, its application in continuous travel speed measurement is somehow doubtful. The engine speed was recorded with an accuracy of 1 rpm using a combination of a toothed wheel and a magnetic proximity pickup. The installed Hall-effect fuel meter indicated the fuel consumption in different engine speeds with an accuracy of 0.1 L min-1. Dynamic (field) calibration of the three-point hitch dynamometer indicated that the RNAM method, for measuring draft of mounted implements, could only provide an estimation of the implement draft. The developed data acquisition system could collect data from the sensors with adequate precision. In addition to displaying the real-time information on its virtual display unit, the data were recorded as a text-file for further analysis. The instrumented tractor is ready for measuring and collecting spatial performance parameters of the tractor-implement. ..

This study was conducted to investigate the effect of soil moisture content in primary tillage and travel speed during disking operation on the performance of an offset disk harrow in a silty clay loam soil. At first, the effect of three soil moisture content ranges of (12-14), (14-16) and (16-18) percent (dry basis) on soil clod size (left from moldboard plowing) was investigated. Then, the performance of disk harrow as a secondary tillage tool was evaluated at three speed ranges of (3-5), (5-7) and (7-9) km/h and three clod size mean weight diameters (31, 41 and 47 mm) resulted from moldboard plowing. The experiment was of a Randomized Complete Block Design, (a factorial experiment) of three replications. The performance parameters evaluated were: draft per unit width, drawbar power requirement, tractor drive wheel slip and degree of soil pulverization. Results indicated that, draft and drawbar power requirements of disk harrow increased significantly with increase in the travel speed. Tractor drive wheel slip was highly influenced by travel speed, clod sizes and as well by their interactions. Soil moisture content was an important factor primarily affecting the size and hardness of soil clods made by plowing operation, and secondly, it played an important role in soil pulverization through disk harrowing. Overall, the optimum soil moisture content for conducting primary tillage using a moldboard plow was determined as about 16 to 18%(dry weight basis), which corresponds to 91% of lower plastic limit of the experimental field. Meanwhile, the optimum speed range for disk harrowing was determined to be 5 to 7 km/h.

Drafts of major primary tillage implements were measured in a clay loam soil using a tension loadcell. Implements consisted of a moldboard, a disk and a chisel plow each equipped with one tillage unit. A photoelectric speed sensor was used for actual forward speed measurements. During the study, the effects of forward speed and tillage depth on draft requirements were investigated. A general regression equation was developed to predict the specific draft of these implements as based on the Standard ASAE, D497.5. Results of statistical analysis indicated a significant increase in draft for all the three implements with an increase in depth of operation. The values of specific draft for the three tested tillage implements were significantly affected by forward speed. Coefficients of specific draft equations were determined through regression analysis. Specific draft equation coefficients (A,B and C) were obtained as: 256.26, 2.28 and12.11 from moldboard plow; 152.28, 3.79 and 9.66 for disk plow; and 26.9, 12.18 and 0.13 for chisel plow respectively. High values of R-square (R2) for specific draft equations in the case of each implement showed that the models are able to present a good prediction of the implement's required draft.

Waterwashing or biodiesel purification is one of the steps in biodiesel fuel processing. Waterwashing of the fuel is an indispensable processing stage, due to the presence of impurities in the fuel. In this research work, some of the effective parameters in biodiesel waterwashing and the optimum conditions which lead to economy in time and cost of waterwashing were investigated. The effective parameters investigated were: temperature, water consumed per batch of fuel, as well as the waterwashing methods namely: mixing, bubble washing, and mist circulation. Test results indicated that temperature affects waterwashing of the fuel most. The minimum time taken for waterwashing, the minimum detergent and moisture remaining in the washed fuel, and the minimum water used up in the process of waterwashing were all obtained when doing the waterwashing at a temperature of 60°C. An increase in the quantity of water used in washing each batch of fueld would result in a decrease of detergent and moisture residue in the fuel, but of course this would be accompanied by a larger quantity of water consumed in the process. Results indicated that mist circulation of waterwashing methods not only takes up less water than the other two methods, but also leaves less such impurities as detergent and catalysts in the final fuel. The amount of soap content after waterwashing through mist circulation method was 0.0283 ppm at 60°C, while they were 0.086 and 0.065 ppm at the same temperature for bubble washing and mixing methods respectively. Waterwashing time taken in mist circulation method was less than that in the other two methods. The average required time for mixing, bubble washing and mist circulation methods at 20°C were 93, 83 and 73 minutes respectively.

Prior to the design and construction of any fruit harvesting machine it is essential to know the physical and mechanical properties of the trees and of its fruits. An example could be cited as the force needed to overcome. The strength with which the fruit is attached to the stem, in trunk shaker harvesting. In this research the acting forces on the fruit during harvest, including tensile strength, bending moment and torsion strength were assessed and analyzed. Experimental measurements were made on some major varieties of Iran’s walnuts (Kaghazi, Khooshei, Soozani and Badami) at Damavand, Kan and Savojbolagh in the countryside vicinity of Tehran. Data were analyzed using a factorial experiment in the form of a completely randomized block design of 15 replications. Analyses showed that the highest mean values of tensile, torsional and bending strengths belonged to Badami (31.12 N), Soozani (9.54 N.cm) and Kaghazi (50.13 N.cm), respectively, while the lowest mean values of strengths belonged to Khooshei with 21.73 N, 7.41 N.cm and 21.42 N.cm. The results finally indicate that the effects of region and interaction between regions as well as variety on bending strength are significant at 5% level. The effect of variety in different varieties of walnut on tensile strength, bending moment, and torsional strength of walnut fruit was significant at 1% level. Considering the results of the conducted experiment, Kooshei variety needs a minimum of forces for harvesting so it could be concluded that mechanical harvesting of this variety as compared to other varieties is preferred, and thus more strongly recommended.

Watermelon is handled and stored in bulk package as some other fruits and vegetables are. Package height must be so appropriately selected that bottom fruit layers will receive no damage or failure. This research was performed to determine and compare the mechanical properties of two varieties in three sizes of watermelon under static load conditions to obtain parameters used in transportation as well as in storage. A statistical factorial experiment in the form of a completely randomized design (2×3×2) of five replications was employed to determine the mechanical properties of watermelon in whole watermelon. Such factors as failure force, failure deformation and fruit rind thickness were among those determined. It is found that the failure force was affected by the direction in which it was exerted. Failure force in the longitudinal direction was less than that in the transverse direction while variation in size of the fruit did not significantly affect either failure force or failure deformation. Results also indicated that failure force and failure deformation were significantly affected by variety. Mean failure forces for Charleston Gray and Crimson Sweet varieties were 1.1 and 1.8 kN, respectively. Investigation of rind thickness in different varieties and sizes of watermelon demonstrated that five millimeter increase in rind thickness can increase failure force up to 70%.

Modeling of drying kinetics of canola was studied at 30 to 100? C in a Lab scale fluidized bed dryer. Drying rate of the crop was assessed, using many conventional moisture ratio models employed in food science. Effective Diffusivity coefficient (Deff) and activation Energy (Ea) of kernel moisture were determined using Fick's Law of Diffusion and Arrhenius Equation. Besides, the effects of temperature changes on drying time were modeled through, regression method. Results indicated that static pressure dropped from 596 to 583 Pa when kernels starting to fluidize. In fluidizing state, canola drying time becomes reduced by 74% through an increase of temperature from 30 to 100? C. In comparison with the other models, Approximate Diffusion model and two term Exponential model are in good agreement with the experimental data respectively with high and low as well as RMSE. Also Newton model was of little with the other models. It bears a single coefficient, and is easy and convenient to be used for an estimation of drying rate of canola in fluidized bed dryer. Temperature changes from 30 to 100? C cause Deff to increase from 3.759×10-11 to 8.457×10-11. In this research, Ea of canola moisture was determined as 11.03 kJ/mol. Selected exponential Regression model is in good agreement with the experimental data and suitable for an estimation of drying time in temperature range of 30 to 100? C.

In this research, moisture sorptions of Sayer date were determined at 20, 30, 40 and 60°C, using the standard static gravimetric method developed by the European Cooperation project Cost 90. Several mathematical models, namely GAB, BET, Iglesias & Chirif and Halsey were employed to fit the experimental data through non-linear regression. Results indicate that equilibrium moisture content increases with water activity. The overall shape of the curves describing the moisture content as function of water activity was typical of sugar-rich material. It was found that the Iglesias & Chirif and GAB models (for all the temperatures) satisfactorily fitted the sorption data. In addition, Isosteric heat of sorption was determined from sorption data, using the Clausius-Clapeyron equation.