نشریه سوخت و احتراق
سال یازدهم شماره 4 (پیاپی 25، زمستان 1397)

In recent years, due to the favorable climate conditions of Iran, rapeseed cultivation has increased significantly. Iran's canola production was 145,900 tons per year in 2010, which reached 174,999 tons per year in 2013. The purpose of this study was to investigate the possibility of biodiesel production from non-edible rapeseed oil using ultrasonic device. In this research, four different factors such as molar ratio, reaction time, pulse and amplitude were considered at three levels. Statistical analysis using Designe Exeprt software, response surface method (RSM) and Box Behnken layout was used to identify the optimal conditions of the process. After analyzing the data and optimizing the biodiesel production process, the biodiesel yield was 89.26% under the optimized conditions, i.e., a methanol-to-oil molar ratio of 4.87:1, pulse of 0.99 s, amplitude 73.5%, and a reaction time of 3.77 min. The biodiesel prepared from None-edible rapeseed oil complies with the criteria dictated by EN 14112 standards. So, the produced biodiesel from none-edible rapeseed can be used as an alternative fuel for a diesel engine.

The usage of biodiesel quality monitoring system (online and batch) is always the basic requirement of its production which requires to research in this area. The purpose of this study is to predict and optimize the palm biodiesel characteristics using its permittivity properties. The parameters of biodiesel permittivity properties (ε’, dielectric constant and ε″, loss factor) at microwave frequencies of (434, 915 and 2450 MHz) were used as input variables. The palm biodiesel characteristics as fatty acid methyl ester (FAME) content and flash point (FP) at three different level of reaction time (3, 9 and 27 min) and catalyst concentration (1, 1.5 and 2 % w/woil) were selected as output parameters for the models. The response surface methodology was developed for prediction and optimization of FAME content and flash point. The optimum condition was obtained using RSM by FAME content of 95.87% and flash point of 162.7 °C with desirability of 0.999.

In diesel engines, a significant part of extracted energy from fuel combustion is lost through exhaust and engine coolant system. The use of biofuels can also affect the heat recovery of the engine. According to the Results of a recent research, the quantity and quality of heat recovered by exhaust gas decreases by increasing the percentage of biodiesel in blend. In the mentioned study, only pure biodiesel fuel and a mixture of 50% biodiesel with conventional diesel have been investigated. While, it is usually recommended to use blends less than 20% biodiesel in standards. In this paper, the potentiality of waste heat recovery of a small power generator has been investigated for B10, B20 and B30 and compared with custom pure diesel fuel. For this purpose, a single module thermoelectric generator (TEG) was used. Results showed that the effect of biodiesel on the waste heat recovery potential of the engine has not a monotonic decreasing trend. As the biodiesel volume increases by up to 20%, the waste heat recovery potentiality increases. Further increasing of biodiesel fraction in blend will reduce the potential of heat recovery. The highest potential for heat recovery was found for blend of B20. Single-module based experiment results showed that the use of the B20 mixture in comparison with conventional diesel fuel can increase the module’s open circuit voltage up to 12% and consequently increase the maximum output power of the module by 25%.

Turbulent mixing in a trapped vortex combustor (TVC) is investigated using large eddy simulation (LES) coupled with filtered mass density function (FMDF). The impact of cavity length-to-depth ratio (L/D) as a crucial geometrical parameter on fuel-air mixing quality is evaluated in non-reacting flow conditions. The vortical structure analysis along with various quantitative measures such as mean cavity and near stoichiometric equivalence ratios, global fuel distribution and mixing efficiency curves are invoked to compare different L/D ratios. The predicted results show that increasing L/D ratio from 0.60 to 0.85 improves mixing quality within the cavity due to expanding the main vortex. Further increment of L/D ratio to 0.93 temporarily impairs the mixing quality, whereas more increasing this ratio to 1.00 leads to resumption of mixing quality improvement. Nevertheless, L/D=0.85 provides the best mixing curves and fuel distribution about mean cavity and near stoichiometric equivalence ratios, and consequently the best mixing quality. These findings are commensurate with expectations based on the vortical flow structures inside the cavity.

Due to excessive consumption of oil resources in developing countries, many efforts have been made to create a suitable alternative fuel for current energy and transportation systems, and biodiesel is one of the best choices. The first target in this study was the simulation of the biodiesel production process from waste cooking oils under different kinetic conditions in the estrification stage using ASPEN PLUS software and then the process was optimized. Due to the fact that the feed used in this process contains more than 1% by weight of fatty acids, the process has two successive steps. In the first and second stages the estrification and transestrification process are carried out, respectively. The goal of the optimization study was to achieve the maximum biodiesel and glycerol sales while the manufacturing cost was minimized. The optimal condition was achieved when the methanol to oil molar ratio of 3 was selected. Also, the temperature of the two reactors had a great influence on the optimality of the process, as both the biodiesel production and the energy consumption of the reactors were notably affected. The total manufacturing cost and profit for this process were calculated to be 16.24 and 12.93 million dollars per year, respectivly.

Today, the use of resistant and high melting point thermocouples is considered as an efficient and inexpensive tool for measuring the temperature of hot gases produced by combustion. Temperature measurement by thermocouples has inherited errors due to the radiation loss and conduction loss. Therefore, it is necessary to correct this error. In this research, the thermocouple is firstly modeled using a numerical method. The validity of the original code is accredited by comparing the results with a similar previous study. Then, the effects of thermocouple diameter and average flow velocity are investigated on the thermocouple error. The error increases about 50% with increasing the thermocouple diameter from 0.5 to 1 mm. Besides, the error decreases about 41% with increasing the average velocity from 1 to 5 m/s. Based on a previous experimental study, the thermocouple modeling results indicate that the maximum errors for thermocouples with diameter of 300 and 500 microns are 30.8% and 39.6% in these conditions, respectively. In the following, a novel comprehensive solution is suggested to calculate the simultaneous distribution of temperature and velocity. Its results confirm that this algorithm has acceptable accuracy for high temperature flow conditions.

 
In this work, HZSM-5 zeolites with aluminum nitrate and aluminum hydroxide and Si/Al ratio 20 were synthesized and the effect of framework aluminum distribution on modification of HZSM-5 with phosphorous were investigated in catalytic cracking of LPG. The prepared catalysts were characterized by X-Ray Diffraction, Field Emission Scanning Electron Microscopy, Nitrogen Adsorption-desorption, X-Ray Fluorescence and NH3-Temperature Programmed Desorption analyses. Aluminum distribution in the framework of HZSM-5 was determined by chemical analysis of X-Ray Fluorescence and reflectance UV-Visible analyses. The highest proportion of single Al atoms was found to be 90.6% for HZAM-5 synthesized with aluminum nitrate and the highest proportion of close Al atoms in the zeolite framework was 47.8% for HZAM-5 synthesized with aluminum hydroxide. The catalytic cracking tests showed that the catalytic stability and the olefin yield in LPG cracking for HZAM-5 synthesized with aluminum nitrate, were greater than those of HZAM-5 synthesized with aluminum hydroxide. After 240 min,the olefin yield just decreased from 49.8% to 41.5% for P/HZSM-5 synthesized with higher single Al atoms. Also, the propylene to ethylene ratio, yield of C5+ heavy products, coke percent and deactivation rate for P/HZSM-5(Nitrate) catalyst were determined to be 0.986, 2%, 6% and 21.31%, respectively.