مجله پژوهش های مکانیک ماشین های کشاورزی
سال ششم شماره 1 (بهار و تابستان 1396)

In this study the effect of a hybrid muffler on sound emitted of a small gas generator which has been covered by an acoustic enclosure was investigated. The specifications of a reactive muffler were calculated according to the recommendation of ASHRAE 2.6 committee and appropriate muffler was selected. The selected muffler was added to the muffler installed by manufacturer on generator (GM) and formed hybrid muffler (HM). The sound of generator set was measured for GM and HM modes on four sides of the generator at five different loading conditions (0%, 25%, 50%, 75% and 100% load) using a sound level meter. The results showed that the application of HM could reduce the sound of generator at firing frequency (31.5 Hz) and frequencies greater than 1000 Hz, with the maximum values of 11.7 dB and 26 dB, respectively. The overall A-weighted generator sound was in the range of 73.2-85.8 dB(A) for all loading conditions and sides by using HM. The acoustical performance of HM on the side with the maximum generator sound (in front of the exhaust) increased from 5.1 dB(A) at no load to 10.61 dB(A) at full load conditions. Therefore, the HM usage could be recommended as a useful approach to attenuate the generator sound.

The most important process after almond cracking is the separating almond kernel from its cracked shell. The pneumatic separation of almond cracked shells from it kernels was experimentally investigated in this wok. The influence of air velocity, mixture feed rates, distance between mixture inlet and kernels outlet, angle of mixture supply into tunnel and repeat times of operation on separation efficiency was studied. Experimental measurement indicated that the separation efficiency decreased with increasing feed rate, angle of mixture supply into tunnel and distance between mixture inlet and kernels outlet. The 7.5m.s-1 was suitable air velocity value for separation kernels from cracked shell. For this air velocity separation efficiency obtained 68.4% and separation error determined 0%. By increasing repeated times the separation efficiency growth. The result of these experiments indicated that 6 times repeated operation was suitable for separating process. Mixture of kernels outlet analysis and revealed that doesn’t do will separation of shells by 20-30mm length, and about 50% of this shells observed on kernels outlet.

Separation of fertile and infertile eggs is a major concern of the poultry industry. If this separation is done at the early days of the incubation period, less space will be occupied in the incubator resulting in improved capacity and efficiency. Dielectric constant and loss factor were used in this study to detect infertile Hy-line eggs. In this study, 126 eggs were selected and their dielectric properties were measured on the third day of incubation. On the fifth day, it was detected that there were 112 fertile and 14 infertile eggs. Data were then analyzed by Weka software using artificial neural network (ANN) and support vector machine (SVM) classifiers. Results showed that, on the third day of incubation, SVM and ANN successfully detected infertile and fertile eggs with 100% accuracy. Detecting the fertile egg by using electrical conductivity is a non-destructive method and is also more accurate than image processing, signal processing and PCR methods.

In order to measure the quality of energy, a concept known as “exergy" is defined. In this study, the exergy of a diesel engine using different blends of diesel and biodiesel fuels (B0, B20, B40 and B100) were investigated. In addition, the effect of speeds of 1200, 1600 and 2000 rpm on analysis of the second law of thermodynamics with various fuels were studied. The parameters evaluated in this study include exergy through work and heat transfer, irreversibility, total exergy, the thermomechanical exergy, and burnt fuel exergy. The results showed that exergy parameters for different blends of diesel and biodiesel fuels increased by the end of combustion stroke and then decreased at the beginning of expansion stroke. Total exergy of B0 increased by 3.3, 7 and 16.7% respectively, as compared to B20¡ B40 and B100. The maximum efficiency of the second law of thermodynamics were attained at 2000 rpm as 44.5, 46.38, 47.89 and 48.5% for B0, B20, B40 and B100, respectively.

Utilization of energy in the drying industry makes drying as one of the most energy intensive operations. In this research, energy and exergy analysis of drying of banana was performed by the hybrid dryer. The experiments were carried out in air velocities of 1, 1.5 and 2 m/s and air tempreatures of 60, 70 and 80℃ with thickness of 5 millimeter. Data was analyzed by complete randomized complete block design with factorial experiment. With increasing time of drying, weight of banana, moisture content, energy utilization, heat of evaporation, outlet exergy and exergy efficiency decreased while exergy loss increased. With increasing air temperature and air velocity energy utilization, heat of evaporation, outlet exergy and exergy loss increased while exergy efficiency decreased. The results of energy and exergy analysis showed that the maximum of utilization energy and exergy loss were 0.91 and 0.41 kJ/s, for air temperature of 80℃ and air velocity of 2 m/s, respectively, while, the minimum of utilization energy and exergy loss were 0.10 and 0.02 kJ/s, for air temperature of 60℃ and air velocity of 1 m/s, respectively. In process of drying, the maximum of exergy efficiency was 91% for air temperature of 60℃ and air velocity of 1 m/s, while, the minimum of exergy efficiency was 0.3% for air temperature of 80℃ and air velocity of 2 m/s.

Ergonomic design of workspace with considering the physical and physiological aspects, is expected to result in increasing the driver's satisfaction and decreasing undesired events. Driving the tractor induces vibrations and rotations to the driver's body which can lead to pain in the body joints. Therefore, a self-declaration questionnaire was designed and filled by 1200 tractor drivers. This questioner included three sections of personal and occupational information and the filed operations performed by the driver. After Collecting and classifying the information extracted from the questionnaire was analyzed with independent t and Chi-square tests. It was indicated that drivers had experienced pain in head and neck (39%), knee (37%), hips, arms and hands (29%), shoulders (28%), upper torso (26%), legs and ankles (25%), lower torso and thighs (24%) and in general, approximately 72% of the drivers had at least one or more than one organ feeling pain. Feeling discomfort after doing various agricultural operations caused increases in pain of some of joints related to the type of agricultural operation. Tillage operations showed a direct role in joint problems at a confidence level of 90%. The two-year study showed that the repetition of these disorders during the sequential years, has led to disability or irrecoverable disorders of joints

Machine vision system is one of the emerging technologies for the quality assessment of agricultural products. Quality of agricultural products is a crucial factor in marketability. In this study, a device was fabricated and developed to evaluate the quality of strawberry using machine vision technology. Strawberry is a rich source of anthocyanins in the nature. Because of the beneficial effects of anthocyanins on health, especially due to its antioxidant, anticancer and anti-inflammatory activites, especial attention is paid to strawberry consumption. In the present study, the possibility of using image processing algorithms to determine the maturity of strawberry fruits based on color and its relationship with the features extracted by destructive methods (weight, antioxidants, sugar, chlorophyll and carotenoids) was evaluated. For this purpose, 12 single-channel color spaces were developed and 228 color features were extracted. To determine the most effective features, correlation analyses were performed between destructive and non-destructive properties at 5% confidence level . The results showed the color space R / (R G B) as the most desired space whose features including sweetness and mean resulted in correlation coefficients of 0.93 and 0.91, respectively with anthocyanins. In addition, the maturity of strawberry could be classified during different growth stages using machine vision with an accuracy of 90%.