Design and Construction
M. Rezaei; J. Khodaei; B. Astinchap
Abstract
IntroductionDue to the increasing need for agricultural products, protection of products against pathogens and preventing them from being wasted is important. Studies on droplet charging systems result in the reduction of chemical usage and an increase in the deposition of droplets on the target. Conventional ...
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IntroductionDue to the increasing need for agricultural products, protection of products against pathogens and preventing them from being wasted is important. Studies on droplet charging systems result in the reduction of chemical usage and an increase in the deposition of droplets on the target. Conventional sprayers used in Iran have numerous disadvantages such as drift, environmental pollution, lack of complete and homogeneous coverage of the spraying surface, phytotoxicity, and crop losses. Therefore, evaluation of new spraying methods and using a variety of electrical sprayers as alternatives to conventional spraying is essential. This study aims to design, construct, and optimize the performance of the electrodynamic head of an atomizer motorized knapsack sprayer, and study the effects of the angle of the target position, spraying distance, and wind speed on the performance of the electrodynamic sprayer.Materials and MethodsExperiments were performed in an agricultural machinery workshop at The Department of Biosystems Engineering, the University of Kurdistan, Iran, with an atomizer motorized knapsack sprayer equipped with an electrodynamic head. The effect of some factors including wind speed, spraying angle, and spraying distance on deposition, coverage percentage, and uniformity of spraying were investigated. These effects were investigated to determine the uniformity coefficient of total spraying. Design Expert 8.0.6 Trial software was used to design the experiments based on central composite design and to analyze the data. The investigated factors and levels were: the distance of nozzles from the target (at three levels of 2, 4, and 6 m), the angle of the target position (at three levels of 0, 45, and 90 degrees), and wind speed (at three levels of 2.5, 3, and 3.5 m s-1). Water-sensitive paper cards were used to evaluate the quality of the spraying. The cards were scanned and magnified with an Olympus SZX12 Stereo Microscope equipped with an objective lens of X1 and a total magnification of 7X. The characteristics of droplet size were determined using Mountains Map Trial and Deposit Scan software.Results and DiscussionThe maximum value of the total spraying uniformity coefficient was equal to 1.95 for the spraying angle of 0 degrees, the distance of 6 meters, and the speed of 3.5 meters per second. Meanwhile, the lowest value of the spray uniformity coefficient of 1.18 was obtained for the test conditions of 90 degrees, distance of 2 m, and speed of 2.5 m s-1, respectively. Based on analysis of variance for the two-factor interactions model (P-value less than 0.0001, explanation coefficient 0.9383, absolute explanation coefficient 0.910, standard deviation 0.0590, and coefficient of variation 3.790%). It can be stated that this model is highly accurate in predicting the uniformity of the total spraying, and the linear components of spraying angle and spraying distance, as well as the interaction of spraying angle × spraying distance and spraying distance × wind speed, significantly affect the uniformity of the total spraying (p<0.05). Nevertheless, the linear component of wind speed and the interaction between wind speed and spraying angle had no significant effect on the changes in the uniformity coefficient of the total spray. According to the variance analysis table (F-values), spraying distance has a far greater effect on the spraying uniformity coefficient than the spraying angle.It has been observed that the spraying uniformity coefficient will increase by increasing the spraying distance and decreasing the spraying angle. It can also be stated that the linear components of spraying angle and spraying distance, the interaction component of spraying angle × spraying distance, and the square power of the components of spraying distance and wind speed have a significant effect on surface coverage. The values of R2, Adj-R2, CV, and PRESS for the model adapted to the test data of leaf surface coverage percentage were obtained as 0.9929, 0.9865, 4.87%, and 188.61, respectively.Among the three input variables, the spraying distance has the greatest effect on the coverage of water-sensitive papers. At larger spraying angles, especially 90 degrees, the coverage decreased with the increasing distance. At spray angle of 90 degrees, by increasing the distance from 2 to 4 m, the spray uniformity coefficient increased from 1.18 at a wind speed of 2.5 m s-1 to 1.84 at a wind speed of 3.5 m s-1. However, at smaller spraying angles (for example zero-degree angle), at first, the spraying coverage increases with the increase of the spraying distance from 2 to 3 m and then sharply decreases afterward. According to the contours of spray coverage, in the spray distance range of 4 to 6 m and regardless of wind speed, the spray coverage does not vary with the increase of the spraying angle (p< 0.05). Meanwhile, in the spray distance range of 2 to 4 m, with the increase of the spraying angle, the spraying coverage increases significantly (p<0.05). Overall, increasing the distance between the sprayer and the target decreased the surface coverage on the target, and in electrodynamic spraying, the uniformity of particle deposition on the underside of the target was relatively the same as on the upper side.ConclusionTo improve the performance of the atomizer motorized knapsack sprayer, an electrodynamic spraying head was designed and built, and its performance was optimized using the response surface method (RSM) with a central composite design. During the research process, the influence of the independent parameters such as the distance between the nozzle and the target, the angle of the target position, and the wind speed on the variables including spraying uniformity, the percentage of the spraying coverage, and the percentage of changes in the total spraying coefficient were discussed and investigated. The results of the research led to the determination of the 3.5 m s-1 wind speed, 2.5 m sprayer distance, and 90 degrees spraying angle with 0.792 desirability, which were considered as the optimal performance conditions of the electrodynamic spraying head. The results of laboratory validation for optimal conditions show that the uniformity of total spraying indicated by the total relative span factor (RSFT) and the percentage of spraying coverage (Cov) are equal to 1.65 and 28.27%, respectively.
G. Khoobbakht
Abstract
Introduction The researchers have been currently focused on replacing fossil fuels by biofuels to reduce dependence on fossil fuels. Biofuels provide low greenhouse emissions with the reduction of oil import. The biofuels can play an important role economically becomes more clear when their ...
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Introduction The researchers have been currently focused on replacing fossil fuels by biofuels to reduce dependence on fossil fuels. Biofuels provide low greenhouse emissions with the reduction of oil import. The biofuels can play an important role economically becomes more clear when their relatively developed agricultural sector is taken into account. Bioethanol, biodiesel and to a lesser extent pure vegetable oils are recently considered as most promising biofuels. Since 19 century, ethanol has been used as a fuel for the diesel engines. The cost of bio-diesel for IC engine is slightly greater than that of diesel oil. The specific fuel consumption, a function of the engine speed, is higher in bio-diesel than in diesel oil. The results previously of Bench-test indicated that the average value of SFC for bio-diesel was 17% greater than that of diesel oil. As for the properties of biodiesel, the lower heating value, higher density and higher viscosity play a primary role in engine fuel consumption for biodiesel. Most of the authors, who agreed that fuel consumption increased for biodiesel compared to diesel, contributed to the loss in the heating value of biodiesel. Of course, some authors only explained the increased fuel consumption as the result of the higher density of biodiesel, which causes a higher mass injection for the same volume at the same injection pressure. Materials and Methods The equipment and instruments used in the present research were a diesel engine (OM 314), a dynamometer, a dynamometer control panel and a fuel tank. A four-cylinder direct injection diesel engine, model OM 314, made by Idem Company, Tabriz, Iran, was used to conduct the experiments. The fuel used in the present research was from waste oil. Ethanol was also used to feed the engine. The blends of diesel–ethanol–biodiesel were prepared on a volumetric basis. The experiments were conducted based on the response surface methodology and using Central Composite Rotatable Designs (CCRD). The response surface methodology, as one of the best methods to optimize processes and determine the effect of different variables on the responses, has special popularity among researchers. Applied research design in this study was CCRD that has the most application among other designs of the method. Independent variables were different ratios of ethanol, biodiesel, and diesel, engine load, and engine rotational speed and responses were included engine brake specific fuel consumption. Results and Discussion The P-values for both total and prediction models of specific fuel costs were less than 0.01. This result showed that the models statistically have high abilities to predict the impacts of independent variables on specific fuel costs at 1% probability level. The linear, quadratic and interaction of the overall model had a P-value less than 0.05 that indicated their statistical validity. The specific fuel costs decreased for all blends by increasing the engine load. The reduction of specific fuel costs was more aggressively observed in low loads. With increasing engine rotational speed, the specific fuel costs were increased at low loads and at middle and high loads it was decreased and then increased. The increasing of volume ratio of biodiesel in the blended fuels, specific fuel costs were increased. By increasing the volumetric ratio of ethanol and biodiesel, specific fuel costs were increased due to lower calorific value and the direct relationship of this variable with brake power compared to that of diesel fuel in all test conditions and all fuel blends. By increasing of biodiesel ratio in the blended fuels, the specific fuel costs were increased at the low percentage of ethanol ratio. But by the increase of ethanol ratio the specific fuel consumption firstly was increased and then slightly decreased at high levels of biodiesel. Conclusion The minimum of the specific fuel costs (580 R kW-1h-1) occurred at full load and engine rotational speed of 2139 rpm for pure diesel (B0E0D100). Also, the maximum of specific fuel consumption was obtained by 9951 R kW-1h-1 at 20% engine load and rotational speed of 2800 rpm and for a fuel blend containing 0.8 l biodiesel, 0.4 l ethanol and 1l diesel (B45.2E36.6D18.2).
G. Khoobbakht
Abstract
IntroductionIn recent years, the exergy analysis method has been widely used in the design, simulation and performance assessment of various thermal systems. In this regard, this method may be applied to various types of engines for identifying losses and efficiencies. This analysis is based on the second ...
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IntroductionIn recent years, the exergy analysis method has been widely used in the design, simulation and performance assessment of various thermal systems. In this regard, this method may be applied to various types of engines for identifying losses and efficiencies. This analysis is based on the second law of thermodynamic. Exergy is a potential or quality of energy. It is possible to make sustainable quality assessment of energy. In this study, the second law of thermodynamics is employed to analyze the quantity and quality of exergy in a fourstroke, four-cylinder, diesel engine using diesel fuel and biodiesel fuel.Materials and MethodsFour experiment variables in the present study including the operating parameters, load and speed, and the added volume of biodiesel of diesel fuel were considered as effective factors on the Break exergy efficiency. Designs that can fit model must have at least three different levels in each variable. This is satisfied by Central Composite Rotatable Designs (CCRD). Similar to the case of the energy analysis, the same assumptions were valid for exergy analysis; the whole engine was considered to be a steady-state open system. For exergy analyses, the entire engine was considered to be a control volume and a steady-state open system. Fuel and air enter, and mechanical work, heat loss and exhaust gases leave the control volume at a constant rate. The exergy balance for the control volume can be stated as. where is the exergy transfer rate associated with the heat loss from the control volume to the environment, assumed to be through cooling water; is the exergy work rate, which is equal to the energetic work rate; is the mass flow rate; is specific flow exergy; and is the exergy destruction (irreversibility) rate. Results and Discussionexergy efficiency increased with increasing engine load. This relationship could be attributed to the reason that brake power increased with increasing engine load, and the other side, there was a positive direct relationship between brake power and exergy efficiency, resulting in an increase of exergy efficiency. Although fuel consumption increased along with increasing engine load, increase in the brake power was much greater than increase in the fuel consumption. On the other hand, an increase in the engine load enhanced combustor temperature which was provided an appropriate condition for combustion and caused an increase in cylinder pressure. At all engine operating conditions, with increasing engine speed, the thermal efficiency at first increased, at moderate speed reached to a maximum amount and finally with more increase in engine speed, the thermal efficiency decreased. The initial increase in thermal efficiency could be attributed to the increase in air to fuel ratio and engine torque which caused an increase in the brake power. Decreasing thermal efficiency in high levels of engine speed could be caused by a decrease in volumetric efficiency of the combustion chamber, because of the time limit on filling cylinder. With increasing biodiesel concentration in the fuel blend, exergy efficiency decreased. The reason could be due to the lower calorific value and the higher viscosity of biodiesel compared to diesel fuel.ConclusionAt all engine operating conditions, the exergy efficiency of the engine increased with increasing engine load also with increasing percentages of biodiesel into synthetic fuel, exergy efficiency increased. 43.09% of the fuel exergy was completely destructed and was not convertible to work. The results of optimization indicated that the most exergy efficiency (37.72%) was occurred for the pure diesel at 2036 rpm and 95% load.
G. Khoobbakht
Abstract
Introduction Diesterol is a new specific term which denotes a mixture of fossil diesel fuel (D), vegetable oil methyl ester called biodiesel (B) and plant derived ethanol (E). Recently, much attention has been paid to the development of alternative fuels in order to meet the emission standards and to ...
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Introduction Diesterol is a new specific term which denotes a mixture of fossil diesel fuel (D), vegetable oil methyl ester called biodiesel (B) and plant derived ethanol (E). Recently, much attention has been paid to the development of alternative fuels in order to meet the emission standards and to reduce the dependency on fossil fuel. Biodiesel and ethanol have been considered as major alternative fuels, as they are derived from renewable sources. These fuels are well oxygenated and therefore have a great potential to reduce emissions. Biodiesel is an oxygenated diesel fuel made from vegetable and animal fats by conversion of the triglyceride fats into esters via transesterification. Materials and Methods The engine test bed consisted of a diesel engine, a dynamometer, a gas analyzer and a fuel tank. The control bench also consisted of control units, data logger and a PC. Engine was loaded by a ferromagnetism dynamometer of 400 kW capacity and load was measured with spring balance. The experiments were designed using a statistical tool known as Design of Experiments (DoE) based on central composite rotatable design (CCRD) of response surface methodology (RSM) and the optimum points were found using RSM. Four experimental variables in the present study including the operating parameters, load and speed and the added volume of biodiesel and ethanol in one liter of diesel fuel were considered to be effective factors on the brake power and torque. Designs that can fit as a model must have at least three different levels in each variable. This is satisfied by central composite rotatable designs (CCRD), which have five levels per variable. The most successful and best among the designs is the central composite design which is accomplished by adding two experimental points along each coordinate axis at opposite sides of the origin and at a distance equal to the semi diagonal of the hyper cube of the factorial design and new extreme values (low and high) for each factor added in this design. In the present work, the response surface methodology based on desirability approach is used for the optimization of experiment parameters (load, speed, biodiesel and ethanol volume) for the measured properties of response (brake power and torque). The optimization analysis was carried out using SAS 9.2 software, where each response is transformed into a dimensionless desirability value (d) and it ranges between d = 0, which suggests that the response is completely unacceptable, and d = 1, which suggests that the response is more desirable. Results and Discussion The resultant quadratic models of the response surface methodology were helpful to predict the response parameters including the performance characteristics of engine and further to identify the significant interactions between the input factors on the responses. By increasing the amount of biodiesel, the brake power is reduced compared to diesel fuel. This is due to two factors: the first is concerned with the percentage of biodiesel in the fuel mix because of the low calorific value of biodiesel compared to diesel fuel, calorific value fuel mixture is reduced. On the other hand, due to the high viscosity of biodiesel than diesel fuel combined with an increase in these enhanced features and fuel atomization when spraying will be difficult. It is generally desirable outcome of these two factors have prevented the ignition and brake power somewhat reduced. Increasing the volume percent biodiesel fuel mixture to the engine braking torque is reduced diesel fuel engines in all working conditions. The reason for this decline is the low calorific value of biodiesel compared to diesel fuel. Also, by increasing the concentration of ethanol in the fuel mix engine braking torque is reduced. The reason for this decline in addition to the low calorific value of ethanol compared to diesel fuel may be related to cetane number and low latent heat of vaporization of ethanol. Conclusion The results depicted that low percentages of biodiesel and bioethanol into synthetic fuel also somewhat have same power and torque but increasing biodiesel and ethanol contents into synthetic fuel reduced power and torque. The maximum brake power (79 kW) occurred for the pure diesel fuel (equivalent to D100B0E0) at 2800 rpm and full load (100%) and the most brake power (325 N.m) occurred for the pure diesel fuel (equivalent to D100B0E0) at 1630 rpm and full load (100%).
B. Hosseinzdeh Samani; M. H. Khoshtaghaza; S. Minaei; Z. Hamidi Esfahani; M. Tavakloli Dakhrabadi
Abstract
Introduction: The common method used for juice pasteurization is the thermal method since thermal methods contribute highly to inactivating microbes. However, applying high temperatures would lead to inefficient effects on nutrition and food value. Such effects may include vitamin loss, nutritional flavor ...
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Introduction: The common method used for juice pasteurization is the thermal method since thermal methods contribute highly to inactivating microbes. However, applying high temperatures would lead to inefficient effects on nutrition and food value. Such effects may include vitamin loss, nutritional flavor loss, non-enzyme browning, and protein reshaping (Kuldiloke, 2002). In order to decrease the adverse effects of the thermal pasteurization method, other methods capable of inactivation of microorganisms can be applied. In doing so, non-thermal methods including pasteurization using high hydrostatic pressure processing (HPP), electrical fields, and ultrasound waves are of interest (Chen and Tseng, 1996). The reason for diminishing microbial count in the presence of ultrasonic waves could be due to the burst of very tiny bubbles developed by ultrasounds which expand quickly and burst in a short time. Due to this burst, special temperature and pressure conditions are developed which could initiate or intensify several physical and/or chemical reactions. The aim of this study is to evaluate the non-thermal ultrasonic method and its effective factors on the E.coli bacteria of sour cherry.
Materials and methods: In order to supply uniform ultrasonic waves, a 1000 W electric generator (Model MPI, Switzerland) working at 20±1 kHz frequency was used. The aim of this study is to evaluate the non-thermal ultrasonic method and its effective factors on the E.coli bacteria of sour cherry. For this purpose, a certain amount of sour cherry fruit was purchased from local markets. First, the fruits were washed, cleaned and cored. The prepared fruits were then dewatered using an electric juicer. In order to separate pulp suspensions and tissue components, the extracted juice was poured into a centrifuge with the speed of 6000 rpm for 20 min. For complete separation of the remaining suspended particles, the transparent portion of the extract was passed through a Whatman filter paper using a vacuum pump (Mehmandoost et al., 2011). Afterwards, the samples were poured into a reactor with diameter and height of 80 and 50 mm, respectively. It is necessary to mention that the dimensions of the reactor were optimized during pretests.
Probe design: One of the most common types of horns used for ultrasonic machining technologies is step type horn (Naď, 2010). For obtaining the governing equations on deformation along the step type horn in steady state conditions, Eq. (1) was used. In the solution of the mentioned differential equation, the answers are divided into two subsets and each of the answers is obtained considering the boundary conditions (Hosseinzadeh et al., 2013):
(1) c^2.[(∂S/∂x)/(S(x)).(∂u(x,t))/∂x+(∂^2 u(x,t))/〖∂x〗^2 ]=(∂^2 u(x,t))/〖∂t〗^2
From Eq. (1), it can be concluded that:
(2) u(x,t)=(A cos〖ωx/c〗+B sin〖ωx/c)(C cos〖ωt+D sinωt 〗 〗)
The boundary conditions for Eq. (2) are written as follows:
(3) {■(a) (∂u(x))/∂x=0,x=0@b) (∂u(x))/∂x=0,x=l@c) u(0)=u_in )}
One of the most important parts in probe design is preventing stress concentration in locations in which the area changes. To avoid this problem, the displacement in this section must be equal to zero (Hosseinzadeh et al., 2013). For obtaining the probe length, the displacement equation and the l1 parameter are used:
σ=-E.u_in.ω/c.sin〖(ω.x)/c〗 (4)
In order to determine the maximum axial stress in step type probe, Eq. (3) and (4) are derived and set equal to zero. Therefore, the maximum stress will be equal to:
σ_max=π.E.u_in/l (5)
Optimization and Modeling using Response Surface Method: Response surface methodology (RSM) has an important application in the design, development and formulation of new products, as well as in the improvement of existing product designs. It defines the effect of the independent variables, alone or in combination, on processes. In addition, to analyzing the effects of the independent variables, this experimental methodology generates a mathematical model which describes the chemical or biochemical processes (Anjum et al., 1997, Halim et al., 2009).
In order to obtain the optimum value, Eq. (1) will be used:
(6) Y_i=β_0+∑▒〖β_i X_i+∑▒〖β_ij X_i X_j+〗〗 ∑▒〖β_ij X_i^2 〗+ε
where, β0, βj, βij, βjj are regression coefficients for intercept, linear, interaction and quadratic coefficients, respectively, while Xi and Xj are coded independent variables and ε is the error.
For this purpose, four factors of ultrasonic power (200 to 600 W), wave exposure time (5 to 15 min), probe diameter (20 to 40 mm), and probe penetration depth in sour cherry juice container (0 to 40 mm) were selected. First, the probes with the desired diameters were designed using the related formulas by using CAD-CAM.
Results and Discussion: Surface Method (RSM) indicated that the quadratic model with 0.96 coefficient of friction, standard error of 1545.3, and coefficient of variation of 14% is the best model for estimating the number of E.coli bacteria among the different studied treatments. The results showed that with increasing probe diameter and probe depth, the destructive effects of ultrasonic wave increase. It was also revealed that as the probe diameter and penetration depth increase, the destructive effect of ultrasonic wave is initially increased and then follows by a decreasing trend. With the increasing power of ultrasonic, ultrasonic intensity increases and leads to reducing number of E.coli in sour cherry juice. The increase in time of treatment with ultrasonic causes a decrease in the number of E.coli in sour cherry juice. This is due to the fact that the increase of ultrasonic exposure time leads to the increase of sonic stream in reactor and results in higher contributions of ultrasonic waves to E.coli. Finally, the examined variables were optimized by RSM and the values of ultrasonic power, waves exposing time, probe diameter, and probe penetration depth were obtained as 600 W, 15 min, 35.31 mm, 20.83 mm, respectively. Considering the mentioned values, the amount of E.coli bacteria reduction was estimated to be 1.97 logarithmic period.
Conclusions:
1. Increasing probe diameter and probe depth increasesthe destructive effect of ultrasonic wave.
2. The examined variables were optimized by RSM and the values of ultrasonic power, waves exposure time, probe diameter, and probe penetration depth were obtained as 600W, 15 min, 35.31 mm, 20.83 mm, respectively. Considering the optimum values, the amount of E.coli bacteria reduction was estimated to be 1.97 logarithmic period.
3. With the increasing power of ultrasonic waves, ultrasonic intensity increases and leads to a reduction of the number of E.coli in sour cherry juice.
4. The increase in time of treatment with ultrasonic causesa decrease in the number of E.coli in sour cherry juice.
