مجله پژوهش های مکانیک ماشین های کشاورزی
سال دوازدهم شماره 4 (زمستان 1402)

Today, despite significant advances in the field of technology and production of advanced equipment, unfortunately, in most countries, the production of agricultural products is insufficient and is decreasing. Therefore, the use of new technologies in order to increase the quality and quantity of agricultural products has a particular importance. For this purpose, in this research, a system equipped with an ultrasonic sensor was used as a warning unit for the non-planting of sugarcane billets in the sugarcane planting machine. By passing the billets at different speeds (2, 2.8, 3.4 and 4.5 m/s) inside the system, the detection accuracy of the ultrasonic sensor was evaluated and the best place to install the sensor on the system was obtained. Data collection was done in a factorial experiment based on a completely randomized design, and data analysis and comparison of the averages were done by SPSS (V16) software. The results of the experiments showed that with increasing distance of the sensor from the billets falling position, the detection accuracy decreases due to increase in the billets speed. In the field tests, the system accuracy in detecting the billets passage in front of the sensor was evaluated. According to the results, a linear regression relationship with R2=0.929 was obtained between the signal announced by the system and the actual number of fallen billets in the furrow. The results indicate that the system is appropriate accuracy for monitoring of fallen billets during planting. In the field evaluation of the warning system's accuracy, the results showed that in the case of non-planted distances more than 0.5 meters, which are practically considered as the points that need to plant again, the system announces and records the position for replant correctly in %95 to %99.8 of times.

Drying dates in the khark stage is a common operation in date-growing areas of the country, such as Jahrom, where the product has completely different quality conditions in terms of texture, color, smell and taste compared to dates. The electrohydrodynamic (EHD) method is a non-thermal drying method at ambient temperature and pressure that can preserves the quality of the dried food product. In this study, a hybrid electrohydrodynamic-convection hot air dryer equipped with an image processing system was used to investigate the changes of size and shape related attributes of thin slices of kharak during the drying process. The aim of this study was to investigate the rate of change in the characteristics related to shape and size including surface area, perimeter, diameter, elongation, and roundness of samples during the drying process by electrohydrodynamic method (EHD in 25 and 35 °C), hot air method (HA at 60 °C), and the hybrid drying method (EHD-HA at 60 °C). The effect of air speed and temperature on the shape and size related attributes was investigated using variance analysis. The results showed that the amount of changes in characteristics related to the shape and size of the product was the highest in the hot air method and less in the EHD method at a temperature of 25° C than the other methods. According to the obtained results, the final product of the EHD method had a higher quality compared to the other methods.

Development of new greenhouses based on new cultivation methods is one of the most important practical solutions to increase food production in the world. But despite the higher production efficiency of the product, their energy consumption is very high. To solve the energy problem in these greenhouses, the use of renewable energy as a permanent energy source has been suggested by scientists in recent years. Meanwhile, photovoltaics has been investigated by many researchers as a permanent and efficient energy source due to its obvious features, suitability and very good compatibility with agricultural environments and also with greenhouse structures. The results have shown that for the development of photovoltaic covers for greenhouses, in addition to proper photovoltaic efficiency, it is necessary to provide transparency required for the growth of plant in the visible range. One of the technologies that, while having transparency, can be used as a transparent photovoltaic cover for greenhouses, is luminescent solar concentrator (LSC). This photovoltaic device has several components, among which the waveguide is one of the most important components, and its optimization through physical parameters such as geometric factor and refractive index can improve LSC performance. Based on this, in this research, taking into account the parameters of a greenhouse cover and a photovoltaic module, two waveguides made of glass and PMMA were investigated in the construction of LSCs to investigate the effect of the geometric factor and the optical refractive index and their effect on the optical efficiency and the PCE of LSCs was investigated. The results showed that by increasing the thickness of the waveguide from 4 to 6 mm, which reduces the amount of its geometric factor, and also the use of PMMA waveguide in comparison with glass, which in addition to having strength and transparency in the visible region, has a higher refractive index (1.46), can increase the PCE and optical efficiency of LSC from 0.33% to 1% and 0.98% to 4.27%, respectively.

Stirred tanks have a wide range of uses in food, chemical, and mineral industries. As a result, accurate knowledge of the hydrodynamic behavior of the fluid in these tanks is essential. One of the issues that arises in stirred tanks when working at high speeds is the vortex inside the tank, which inhibits appropriate mixing. In the current numerical study, by attaching vertical baffles to the inner wall of the tank, the flow field and vortex phenomena were evaluated. Computational Fluid Dynamics (CFD) was employed to explore the influence of wall baffles on variations in radial velocity and turbulent kinetic energy. Based on the numerical results, it was discovered that adding baffles to the tank wall enables the radial flow to be extended, which provides for better mixing inside the stirred tank. Moreover, by adding the baffles, vertical flow is improved, enhancing the agitation inside the tank. According to the results, the turbulent kinetic energy for tanks with and without baffles is 0.00957 m2 / m3 and 0.0112 m2 / s3, respectively, while the energy dissipation rates were 0.955 m2 / m3 and 0.805 m2 / s3, respectively. Increasing velocity in the vicinity of the baffle, results in enhanced agitation, providing the energy demand for better mixing. This prevents continuous swirling motion which can reduce agitation quality.

This paper aims to examine a combined heating, power, and hydrogen system production using biogas energy. Biogas steam and dry reforming method are designed based on equilibrium data with the EES program. The results show that biogas has two principal roles for combustion and reforming processes simultaneously. The heating energy produced from biogas causes the reforming of biogas and improves the system efficiency by 74%. The maximum exergy efficiency and hydrogen production are obtained at 58.34% and 0.11-0.83 kg/s, respectively. The results also show that the combustion chamber has the highest exergy destruction by about 51% when the amount of electric power plant is considered between 5 to 40 MW. A parametric study for optimizing hydrogen production analyzes the key parameters. The optimal scenarios are when CO2/CH4=0.50-0.66, H2O/CH4=2-3.6, and the reforming temperature is 965-1036K. The conversion of methane and carbon dioxide shows the environmental effect of decreasing greenhouse gases. At 965K or higher, methane and carbon dioxide conversion rates reach 97% and 86%, respectively. This paper aims to develop a novel methodology for identifying thermodynamic cycle conditions and reforming processes only by use of biogas as the source of energy.

In order to respond to the huge demand for energy and reduce the consumption of fossil fuels and reduce air pollution, the use of a green, clean and stable biofuel is the only alternative. When a suitable precursor and process is used in the production of biodiesel, its replacement as an alternative fuel becomes more certain. The aim of this study is to evaluate the combined jet plasma-ultrasonic reactor in biodiesel production. The use of plasma jet in the production of biodiesel is known as an advanced molecular decomposition process due to the use of strong electric fields in the transesterification process and has been the focus of researchers in recent years. Four factors: molar ratio of methanol to oil (1:4, 1:6, 1:8), catalyst concentration (0.75, 1, 1.25), time (30, 60 and 90 s) and ultrasonic power (100, 250 and 400 W) was investigated for biodiesel production in this combined system. Response surface methodology (RSM) was used to optimize the methyl ester content. In RSM optimization, the highest yield of biodiesel by the software was 93.82% in ultrasonic power of 395.76 W, molar ratio of 6.75, catalyst concentration of 0.96%w/w and reaction time of 79.58 s. The physical and chemical characteristics of the produced biodiesel were in accordance with the ASTM D6751 standard. In general, the results show that the biodiesel produced through this combined system saves time with the highest conversion efficiency.

This study aimed to investigate the effects of conservation agricultural methods on the amount of soil organic matter, energy indices, and crop yield in white bean (Dorsa variety) cultivation. The experiment was conducted in a randomized complete block design with three replications at the Markazi Agricultural and Natural Resources Research and Education Center in the cropping years of 2017-2018, 2018-2019, and 2019-2020. The experimental treatments were involved: 1- the conventional tillage method (by using moldboard plow+ disc) as a control, 2-Reduced tillage with a chisel-packer plow, and 3-No-tillage method with a direct planting seeder. In each season, the soil organic matter content was measured. The yield and yield components of dry bean seeds were measured at the end of the season by removing the margins. In addition, inputs and outputs energy consumption, gross energy produced per hectare, energy ratio and intensity, and energy productivity were calculated for each treatment. The results showed that the highest and lowest yields were obtained in reduced tillage and no-tillage, respectively, with 2869 and 2076 kg/ha. The three-year average values of soil organic matter in the experimental treatments for each season were 0.430, 0.582, and 0.621%, respectively, with the highest increase seen in reduced tillage treatment. The highest and the lowest energy intensity were obtained for no-tillage and reduced tillage with 38.6 and 27.3 MJ/kg, respectively. One of the reasons for increasing energy consumption and decreasing the yield in the no-tillage method was the high weed population and plentiful consumption of general and specific herbicides. Finally, due to the increase in grain yield, amount of soil organic matter, and improvement of energy indices in dry bean cultivation, the reduced tillage method was evaluated as more suitable than the no-tillage method.

Oat is one of the grains used in the world, and consuming its right amounts could be considered as a part of a gluten-free diet for people suffering from celiac disease. However, this grain has a hull that is not digested by the human digestive system, and hence need to be dehulled. In this research, a laboratory impact oat dehuller was designed, fabricated and evaluated. The dehulling experiments of Hashemi oat variety were performed at 5 levels of rotor speed (1000, 1250, 1500, 1750, and 2000 rpm) and 3 levels of moisture content (6, 9, and 12% w.b.) with three replications. The effect of these variables on groat percentage (GP), dehulling efficiency (DHE), broken groats (%B), unbroken groat yield (%GY), and mill yield (%MY) was studied. The results revealed that with increase in the rotational speed of the rotor at all grain moistures, the %GY first increased and then decreased. The DHE indicated an ascending trend with increasing the rotor speed and grain moisture. The %B increased with increase in the rotational speed and decreased with increase in the grain moisture. The grains that were more resistant to dehulling showed also more resistance to breakage. At each grain moisture content, the rotational speed that led to the highest %GY was considered as the best rotor speed. The %MY had a direct relationship with %GP and DHE, and it showed an ascending trend with increasing the rotor speed and a descending trend with increasing the grain moisture. The best rotor speed and moisture content for dehulling the oat grains were determined to be 1750 rpm and 12% w.b., respectively.

Non-use of non-edible and toxic mushrooms by common people in edible mushrooms is a dangerous challenge that can lead to mushroom poisoning. In this research, it is possible to use the smell machine system based on metal semiconductor sensors as non-destructive tools for non-edible mushrooms. Food was evaluated. PCA principal component analysis, LDA linear discriminant analysis, QDA 2 degree linear discriminant analysis, SVM support vector machine and ANN artificial neural network were the methods used to achieve this goal. The results obtained from the analyzes showed that the best performance of the PCA method was in the separation of 5 samples of edible and non-edible mushrooms with 91% accuracy. The obtained results showed that the QDA analysis method separated the mushroom samples into three different categories with 100% accuracy and better performance than the LDA method. In the meantime, the C-SVM method could only fully and 100% detect A. bisporus among the samples of edible and non-edible mushrooms, and it did not have a good performance in differentiating other samples. The ANN method had a good performance in classifying the samples so that it could classify the samples of A. bisporus, S. comptus and R. delica 100%. According to the results obtained in this research, it can be said that the QDA method was higher than other methods in classifying types of fungi. Considering the proper performance of machine smell in separating edible mushrooms from non-edible mushrooms, it seems that using this technology will be a promising method in different types of mushroom.

Cold plasma is an environment full of active ions and energetic particles applied to the surface of the sample to disinfect materials, make their surface hydrophilic and improve their colour. These particles create micropores on the surface of the sample and can be useful in removing moisture and drying sensitive materials. The laurel tree, with the scientific name Nobilis Laurus, is an evergreen plant that has various medicinal properties and is also used in the food industry. In this study, the effect of DBD cold plasma pretreatment on the drying kinetics of bay leaves in a cabinet dryer was investigated. The experiments were conducted using the response surface method based on the Box-Behnken design. The independent variables were temperature (30, 40 and 50 oC), air velocity (1, 2, 3 m/s), plasma treatment time (0, 10, 20 s) and plasma intensity (23, 29 and 35 kV). Dependent variables included drying time to a moisture content of 10% and minimum achievable moisture content. The results showed the significant influence of temperature, air velocity and plasma treatment time on the dependent variables. Increasing the temperature decreased both the drying time and the minimum achievable moisture content. Plasma intensity had no significant effect on minimum accessible moisture and drying time. The results showed a significant effect of plasma treatment time, such that 20 seconds resulted in a reduction in drying time of about 20% compared to treatment without plasma. This can save a considerable amount of energy in the drying process. The two variables temperature and plasma intensity had a significant effect on the brightness and darkness changes of the leaves after drying, so that the use of plasma pre-treatment reduced the colour change of the samples.