نشریه مکانیزاسیون کشاورزی
سال ششم شماره 4 (زمستان 1400)

Due to the reduction of fresh water resources, increasing population growth, increasing industrial activities and changing people's living standards, water consumption increases consequently and water crisis is rapidly growing around the world, especially in Iran. A variety of desalination systems have been developed and used with their common advantages and disadvantages. High energy consumption is a major problem in most of the desalination systems. Linking desalination systems with ultrasound technology is one of the novel technologies to improve the energy consumption of these systems. In this research, fluid-dynamic simulation of ultrasound desalination system was performed by ANSYSCFX software. The results of numerical simulations were validated with the results of experimental tests. Two types of fluids: hot air entering the system and a mixture of vapor and NaCl were defined as the system inputs in the numerical simulation. Investigating the solutes amount in system's output of the ultrasound desalination system was the aim of this research. It was shown that according the numerical results, the amount of these solutes in the output was approximately 2% of the total primary solutes in the water. It was also concluded that in order to increase the efficiency of the system, the hot air amount entering the system should be decreased. In order to validate the inlet and outlet temperature, fluid containing a mixture of vapor and NaCl was used. The difference in results of the numerical simulation and the experimental tests was just 15%, which indicates that the simulation results are trustful.

This study was carried out to evaluate the energy consumption pattern and analysis of economic indices to determine the input sensitivity for wheat the production system in Ardabil, Iran. Data were collected from 100 irrigated wheat farms selected during 2017-2018 using a random sampling method. The sensitivity of the energy inputs was estimated using the marginal physical productivity (MPP) method and partial regression coefficients on wheat yield. The results indicated that the total energy input was 38755.34 MJ ha-1, of which approximately 37.38% and 19.04% were from nitrogen fertilizers and diesel fuel, respectively. Approximately, 39.85% of the total energy inputs consumed in wheat production was direct energy, while the remaining 60.07% was indirect. The econometric assessment results revealed that the energy inputs from machinery had a significant influence on the yield. Sensitivity analysis indicated that the MPP value for energy inputs was between -0.23 and 1.67. Also, the MPP value for was the highest, followed by machinery, diesel fuel, chemical fertilizers and chemical sprays energy inputs, respectively.

 In order to Design, fabrication power transmission to cutter bar by mechanical gearbox mechanism, first, the work done and the combing mechanism of different combines were studied. Then, a new design and idea was made in the workshop and was installed and tested on the cutting shoulder of John Deere 955 combine to test the speed of the saw and the fit of the saw blade. 1000 beats per minute were recorded, which was acceptable in terms of speed and adaptation. In order to achieve different cycles, the power transmission method was used with the help of money and belts, which could be achieved by changing the monetary diameter of different cycles. For better alignment of the saw blade, a connecting rod with the possibility of changing the length was used. By shortening and lengthening the connecting rod, the matching between the saw blade and the saw blade became possible. Then it was tested and evaluated in terms of vibration and emitted sound. According to the obtained results, the new design is acceptable in terms of saw speed and saw blade compliance and is recommended for replacement with previous systems.

Availability of efficient attachments on tillage implements is one of the challenges in variable-rate tilling concept. Reposition of the rotary tiller’s soil hood automatically makes it a practical tool for variable rate plowing. In this study, an electro-hydraulic system using a closed-loop control circuitry and the tractor hydraulic power was utilized to create different roughness by soil hood reposition. The effect of travel speed and soil hood position in creating random roughness (RR) of the resulting soil surface was investigated using a completely randomized design and a 3×4 factorial experiment in 3 replications. The average RR created by the travel speeds of 2.6, 3.5, and 4.8 km/h were 1.32, 1.91, and 2.61 cm, respectively. Similarly, the average of RR created using three soil hood positions of 0, 40, and 80 degrees were 1.43, 1.94, and 2.46 cm, respectively. The analysis of variance showed that the effects of travel speed and soil hood position on random roughness index were significant at the probability level of 1%. Therefore, it can be stated that in the case of real-time control of these two factors and using the RR index as a control feedback signal, a rotary tiller can be implemented to perform variable rate tilling.

The Control valve of the hydraulic pump of MF285 tractor is a sliding type and installed at the pump inlet. This causes the draft control system couldn't react on time to changes in soil conditions and consequently the tractive efficiency decreases. In this research a new control valve was designed and constructed that can be installed at the pump outlet, with electronic control capability and for use in the electro-hydraulic hitch control system. In order to ensure the correct operation of the control valve, the effects of two control valves (electronic and mechanical) under three engine speed(rpm) levels and three oil pressure levels on flow rate of the hydraulic pump were assessed by conducting a completely randomized design. The results showed that the effect of engine speed, oil pressure and their interaction were significant (P<0.01) but the effect of control valve type and its interactions with other treatments were not significant. At all pressure levels, the flow rate increased with increasing engine rpm. Also, a significant linear relationship was observed between the pump flow and engine speed. The results of transient response tests of electro-hydraulic control system to step input in raising and lowering positions showed that the control system followed the system input with a suitable speed. And after reaching the steady state, kept the height of the device in the range of the death zone (± 2 cm).

In the recent years, agricultural products packaging was faced with some challenges. One of these challenges is measuring the oxygen and carbon dioxide amount during the respiration of stored products. Due to the high cost of the sensors and measuring devices of oxygen and carbon dioxide, the researchers have been looking for alternative methods for those measuring. The major aims of this study is to find a mathematical measurement method based on temperature, humidity ratio, and absolute and differential pressure during the respiration of lettuce storage. The present study was conducted at three temperature levels (5, 15, and 25 °C) and three storage time levels (24, 48 and 72 h). Based on the results of the mathematical model, the accuracy of prediction at the storage temperature of 5, 15, and 25°C for oxygen measurement were 96%, 98% and 97% and for carbon dioxide measurement were 95%, 99% and 98%, respectively. The statistical analysis of the variation parameters of carbon dioxide, humidity ratio and absolute and differential pressure with the variation of temperature and storage time of lettuce was significant at 1% levels.