نشریه تحقیقات سامانه ها و مکانیزاسیون کشاورزی
پیاپی 83 (پاییز 1401)

Among different types of biomass, the inherent advantages of microalgae have made them a useful source for biofuel production. The hydrothermal liquefaction process is one of the thermochemical processes that has attracted the attention of researchers due to its advantages such as the production of valuable products and low energy consumption. The aim of this article is to investigate the production of biofuel from spirulina microalgae using the hydrothermal liquefaction process in a subcritical water environment in a laboratory and discontinuous manner. The results of detailed elemental analysis of biofuel showed that the amount of carbon, hydrogen, sulfur and nitrogen of raw biofuel is equal to 68.27, 15.56, 3.08 and 0.38 percent, respectively. In addition, the produced biofuel compounds were analyzed by infrared Fourier transform spectroscopic analysis, the results of which confirm the production of clean fuel compared to fossil fuels.
Gas chromatography-mass spectrometry, Fourier Transform Infrared Spectroscopy and CHN analyzer were used for analyzing the samples. The result showed that the products of hydrothermal process consisted of different range of hydrocarbons almost similar to hydrocarbon chain available in fuel oil (gasoline). Also, carbon, nitrogen and sulfur contents of the oil obtained from hydrothermal liquefaction process, was consistent with those reports provided by other similar studies.This research has proved that hydrothermal liquefaction is a promising process for converting micro algae to bio oil and emphasizing the effect of pretreatment on improving the oil production.

This study evaluated the performance of a thermal dryer with a closed air circulation system equipped with a metal-organic framework (MOF) system. Dryer sections included: product drying chamber, the MOF containing chamber nano-absorbents, measurement and control systems. Dryer yield on mint was compared at three temperature levels (40, 50, and 60 °C). Finally, the energy consumption and drying mint leaves was evaluated. The results showed that the closed air circulation system reduces the dry time by 27% to 50%, the penetration coefficient of mint leaves increased with increasing temperature. Its values in cases of not using and using nano-absorbent plates were determined respectively (4.05690×10-11) and (2.8215×10-10) m2/s. The activation energy in two methods of not using and using the nano-absorbents was 45.72 and 51.96 kJ/mol, respectively, which is consistent with the researchers' results. Also, the coefficient of performance, the rate of moisture evaporation, and the rate of specific moisture evaporation showed the effectiveness of using nano-absorbent in the dryer system and reducing energy consumption. The total color index (ΔE) did not change much with increasing temperature from 40 to 50 °C, but from 50 to 60 °C, the increased total color index. There wasn't a clear difference in total color index between the two methods of using and not using nano-adsorbent.

Determination of sugar concentration of sugar beet in sugar factories is of great importance and is a basis for valuation of the sugar beet as well as assessment of the sugar production process in the factory. In this study with the aim of development of a non-destructive method for measurement of the sugar concentration of sugar beet in terms of Brix, a proximal dielectric sensor was developed and evaluated. This sensor is an open-end coaxial probe consisting of two metallic concentric ring electrodes which is connected to function generator and spectrum analyzer through coaxial cables. One hundred random samples of sugar beet were selected and measured by the dielectric sensor. Dielectric spectra i.e. amplitude as a function of frequency were obtained in the frequency range of 0-150 MHz. The reference Brix was measured with extracting juice from the points of dielectric measurement using a refractometer. The results showed that in the ranges of 30-50 and 120-140 MHz, the dielectric spectra varied noticeably in relation with variations in sugar beet Brix so that the amplitude decreased with increasing the Brix. The partial least square regression (PLSR) method could model the Brix as a function of the dielectric spectra variables with R2= 0.81 and RMSE of 0.72 Brix. The results of the study indicated that the dielectric sensor and measurement method was a simple and reliable method for non-destructive measuring of sugar beet Brix.

Tillers (2WTs) are among the types of small tractors that are usually used in greenhouses, orchards, and  paddy fields; they are most useful  in places where it is difficult to move tractors. The existing tillers have only one clutch for power transmission to the gearbox, and they do not have a clutch to guide and steer. For this reason, they have many problems for turning and steering, especially under the trees and changing the movement direction during work. Therefore, in this research, an attempt was made to solve this problem. Two types of plate (disc) and cone friction clutches, which are the most used in agricultural machines, were thought about.The torque generated on the rotors of a 9-hp tiller was calculated while the tiller was running at gear ratio one. The applied forces from the operator (driver) to the clutch plate (disc) for engaging the clutch was calculated. Having the amount of transmission force, torque and available space to the design of the cone clutch, which can be used on the rotary axles of the tiller, was performed using 3D design software (CATIA). To ensure the resistance of parts against failure and their correct operation, static analysis of selected clutch parts that are exposed to maximum stress was performed in ANSYS software. The results indicated that the clutch parts had appropriate strength and hence, would operate safely. Therefore, it can be concluded that it is possible to use the cone clutch on such tillers.Two types of plate (disc) and cone friction clutches, which are the most used in agricultural machines, were considered.The torque generated on the rotors of a 9-hp tiller was calculated while the tiller was running at gear ratio one. The applied forces from the user (driver) to the clutch plate (disc) for engaging the clutch was calculated. Having the amount of transmission force, torque and available space to the design of the cone clutch, which can be used on the rotary axles of the tiller, was performed using 3D design software (CATIA). To ensure the resistance of parts against failure and their correct operation, static analysis of selected clutch parts that are exposed to maximum stress was performed in ANSYS software. The results indicates that the clutch parts have appropriate strength and hence, would operate safely. Therefore, it can be concluded that it is possible to use the cone clutch on such tillers.

In recent decades, production of crops in plant factory vertical systems attracted lots of attention since it makes possible crop production with optimum consumption of resources, irrespective of climate conditions. In the present study, growth and yield of the lettuce (Lactuca sativa L.) in the plant factory vertical system under artificial light were investigated. To do so, the plants were grown in a hydroponic system using nutrition film Technique (NFT). Completely randomized design was used to study the impact of different light spectra using light emitting diodes (LED), modules including red and blue (RB) lights with different ratios (RB,90:10 – RB, 80:20 – RB, 70:30), red, blue, and far red (RBFr in 3:1:1 ratio), and red and white (RW in 1:1 ratio). Lighting period was set to 18 h at an intensity of 250 μ.mol m-2 s-1. The highest leaf area and plant weight, as the main yield characteristics of lettuce, were detected under RB 80:20 treatments. The plants grown under RBFA showed shade avoidance responses (tall plants with low leaf area), which is not favourable for lettuce production. In conclusion, due to having the best growth and yield under RB 80:20 light spectra, it is introduced as the best light spectrum for production of lettuce plants in plant factory system.

In this research, for cooking of mushrooms, an ohmic heating device was used to evaluate the performance of the ohmic system in three voltage gradients (7.5, 9.25 and 11.5 V/cm), three types of electrodes (steel, brass and aluminum) and three concentrations of the ohmic solution, 20 ml of water and three amounts of salt (1, 2 and 3g). Also, in this process, the input current, electrical conductivity coefficient and system performance coefficient during the mushroom cooking process were calculated and the obtained data were analyzed using statistical software. Results showed that all three factors of voltage gradient, electrode type and solution concentration had a significant effect on the investigated factors and the greatest effect was shown in voltage gradient and then the electrode type and ohmic solution concentration had a significant effect on the input current factors, electrical conductivity coefficient and system performance coefficient. Based on results, it can be stated that the best type of electrode used is aluminum electrode and the best concentration is 3 grams of salt and 20 milliliters of water. The highest values of input current, electrical conductivity coefficient and performance coefficient are obtained in this concentration with this electrode.