نشریه ماشین های کشاورزی
سال سیزدهم شماره 1 (پیاپی 27، بهار 1402)

In this study a mathematical analysis for estimating the performance rate "RP" of wheel type trenching machine was studied. The mathematical analysis quantifies the analysis and resulted in an equation. This mathematical equation was checked under different operating conditions. The practical study of the performance rate showed that the deviation of the theoretical performance rate from the actual performance rate ranged from 5 to 7% for the 60.4 and 90.5 cm trench depth, respectively. The machine field efficiency also ranged between 43 and 50.1% for 90.5 cm and 60.4 cm trench depth respectively.

The present study aimed to examine the application of accurate and principle-based evaluation of a measuring instrument called the Form Tester in determining and detecting the wear phenomenon in the cylinder liner of agricultural tractors. For this purpose, a cylinder liner of the Perkins 4-248 engine (related to the Massey Ferguson 285 tractor) was manufactured by Keyhan Sanat Ghaem Company was used. The geometric parameters that were measured in this research included roundness, straightness, and concentricity of the cylinder liner. The evaluations on roundness and concentricity of cylinder liner were conducted in 12 circular positions with the same longitudinal distances. The straightness was measured in five lines with the same longitudinal distances in 90° around the cylinder liner environment. The results of the measurements were discussed and analyzed to evaluate the engine status along the functional path of the piston within the cylinder liner. The degree of deviation rate of the parameters indicated significant wear within the cylindrical liner. The wear rate in cross-sections at high and low dead points was significantly greater than that of the same cross-section in the vicinity of the midpoint of the piston movement path inside the cylinder, as well as the cross-sections near the high dead point. The results of this research provide feedbacks for engine designers to apply various changes to the engine and for maintenance and repair engineers to ensure the correct implementation as well as preventive and predictive repair and maintenance strategies.

The main purpose of this study was to provide a method for accurately identifying the position of cucumber fruit in digital images of the greenhouse cucumber plant. After balancing the brightness histogram of the desired image, it multiplies the image with a window containing the image of a cucumber fruit, which causes larger coefficients to be obtained in areas with suspected cucumber. By extracting these local maximums, clusters of initial points are obtained as possible windows of cucumber existence. Then, in order to accurately detect the location of the cucumbers, these points and areas around them are referred to a neural network that has been trained using a number of images including cucumber images, non-cucumber images and their optimal responses. The proposed method was implemented in the Simulink toolbox of MATLAB software. The proposed method was then simulated using this network structure and tested on 120 images obtained from a greenhouse by a digital camera. The areas obtained from this network led to the accurate detection of the location of the cucumbers in the image. The proposed method was then simulated and tested on 120 images. The proposed method had a low error and was able to detect high levels of cucumber fruit in the images. This detection took an average of 5.12 seconds for each image. The accuracy of the network in correctly identifying the position of the cucumber fruit in the images was 95.3%. This method had low error and was able to detect a high rate at a good time of cucumber fruits in discover images.

Accurate investigation of kinetics and development of high-precision seed drying models will help better studying the drying process by identifying effective parameters. Present study investigates the application of cold plasma (CP), as a pretreatment process, in air drying of canola seeds. This may bring about some complication into the drying kinetics investigation. Canola seeds with an initial moisture content of 27.5±1% (dry basis) were exposed to CP for 0, 15, 30, and 60 s prior to fluidization by air at temperatures of 40, 50 and 60 °C in a pilot scale fluidized bed heated by a solar panel.  The results showed a decreasing trend in drying time from 40 to 60 oC. The shortest drying time corresponds to samples dried at 60 oC with no CP pretreatment. The longest period however occurred for samples dried at 40 oC with 60 s of CP pretreatment. The greatest effect of CP on reducing the drying time was observed at temperatures of 40 and 50 °C at the CP exposure time of 15 and 60 s, respectively.  A reasonably accurate study of drying kinetics was accomplished using the superposition method. Accordingly, using experimental data, curves correspond to different drying conditions were plotted and in two steps these were shifted to a reference curve to acquire a final drying curve. The curve then was fitted to a second-order equation, and was validated using the experimental data. The correlation coefficients, mean square error and mean absolute error were 0.99, 0.03, and 0.023, respectively.

In this study, an electronic system was built to determine the mass and volume of orange fruits from their dimensions using ultrasonic sensors. The system hardware parts include a metal box, three ultrasonic sensors, a load-cell sensor, an Arduino board, a memory card module, a voltage converter, a keypad, a display and a power adapter. A computer program was written to obtain data from ultrasonic sensors and determine the mass and volume of fruits using regression relationships in Arduino software. 100 samples of orange fruits (Dezful local variety) were picked randomly from a garden and various measurements were done to determine the main physical properties of fruits including three dimensions, mass (M), and volume (V). The system output values for mass and volume of orange fruits with their actual values had no significant difference at 1% probability level. The root mean square error (RMSE) in determining the oranges mass and volume by the system were 9.02 g and 10.90 cm3, respectively. In general, the proposed system performance was acceptable and it can be used for determining the mass and volume of orange fruits.

This study presents the effects of compressed natural gas fuel on a four-cylinder compression ignition engine. Compressed natural gas as the main fuel and diesel fuel as the igniter were used to investigate performance and emissions from the dual fuel engine. According to the engine speed and load, the amount of diesel fuel as igniter was adjusted using mechanical changes in the governor, while no ignition system was used. The engine experimental tests were performed at engine speeds of 1200, 1400, 1600, 1800 and 2000 rpm, using diesel fuel and dual fuel. These data were collected in the Engine Research Center of Tabriz Motorsazan Company and experimental runs were repeated three times. The maximum torque of the engine in diesel mode was 360 N m at 1400 rpm. Compared to the diesel mode, the dual fuel mode showed the maximum torque by 334 N m at 1600 rpm, which is about 26 N m less than that gained from the diesel mode. Considering emissions analysis at 2000 rpm, it is seen that the amount of NOX, HC, CO2 and CO emissions in the dual fuel mode was 20, 53, 16 and 86% more than diesel mode, respectively. However, O2 and soot showed the highest reduction at 2000 rpm for dual fuel mode by 51% and 69% respectively. This study indicated that there was a considerable enhancement in exhausted emissions when the injection of the diesel fuel as igniter was done mechanically. In this regard, control the amount and time of the igniter injection could likely be helped for better control of emissions. Therefore, further research on the modification of the diesel injection system as igniter or CNG injection system is needed towards reducing emissions.

Soil compaction can be naturally occurred or can be machinery-induced. Subsoiling is often applied to loosen soil compaction and decrease soil strength to levels that allow for root development and growth. Variable-depth subsoiling which modifies the physical properties of soil only where the tillage is required for crop growth has the potential to reduce labor, costs and fuel, and energy requirements. Since this study aimed to perform subsoiling operations with variable depth, the variable-depth tillage (VDT) tool was developed. A pneumatic multi-nozzles sensor has been used to simultaneously predict the depth of a soil layer in three depths (15, 30, and 45 cm), and send a signal to control the depth of the VDT tool. Evaluation of the VDT tool system was performed by two methods namely static and dynamic tests. In static evaluation, the system response time was measured to reach 95% of the proposed depths. The dynamic evaluation of the tool was accomplished in two steps in the field. The amount of fuel consumption and the travel distance of the tool tine to reach the desired operation depth were measured and compared with the common subsoiler (when the depth control was OFF). The average fuel consumption by using the variable-depth tillage tool decreased by 17.36% compared to the constant depth. Furthermore, the pneumatic sensor tine penetrated into the soil perfectly and sent the control signal to the control unit of the VDT tool in real-time, and the VDT tool loosened the soil at the exact depths sent by the sensor.