نشریه سوخت و احتراق
سال دوازدهم شماره 1 (پیاپی 26، بهار 1398)

The tendency toward research on the production and application of renewable energy, such as biodiesel, to reduce greenhouse gases and emissions of fossil fuels, is one of the most important issues in the world policies which has been discussed. Dielectric properties (ε’, dielectric constant and ε", dielectric loss factor) of materials play a major role in the microwave design and process of biodiesel production. The purpose of this research is to investigate and evaluate the biodiesel's dielectric properties in a pilot-scale using microwave technology and the relationship between its various effective parameters. In this study, the effects of reaction time (1, 3 and 9 minutes), catalyst concentration (1, 1.5 and 2% of oil weight) and temperature changes (30, 45 and 60°C) were studied. The probe reflection system was used at a frequency of 2450 MHz to measure the dielectric properties. The results showed that, with increasing reaction time and decreasing temperature, the dielectric constant values increased, and by decreasing catalyst concentration, temperature and reaction time, the dielectric loss factor decreased.

In this paper, numerical simulation of asphalt water slurry gasification process as a heavy fuel oil in a single stage gasifier, using the commercial Ansys fluent software, in a two-dimensional geometry And based on the Eulerian-Lagrangian approach has been done. In this simulation, the distribution of velocity, temperature distribution and molar fraction distribution of synthesis gas species have been calculated. The effect of different devolatalization models, the discrete phase particle size on gasification, and also for the first time, the effect of the use of discrete phase non-spherical particles on gasification parameters has been investigated. The results of this study showed that the water mixture of asphalt can be considered as a suitable feed for gasification. In the study of non-spherical particles it was also found that if the particles with a shape factor of 0.1, which have the greatest difference with spherical particles, are used, the temperature of the chamber slightly increases and the maximum temperature is more distant than the feed intake.

A large amount of oil sludge is produced annually during the operation and process activities on crude oil. The burning of oil sludge can be considered as an approach in order to recover the energy as well as to control and mitigate risks of this hazardous waste. In the present study, the combustion of solid fuel derived from refinery oily-sludge is conducted numerically in a 2-D axisymmetric furnace. Investigating the effect of fuel particle diameter on the combustion process shows that with increasing particle diameter the maximum temperature reduces and the maximum temperature location 
A large amount of oil sludge is produced annually during the operation and process activities on crude oil. The burning of oil sludge can be considered as an approach in order to recover the energy as well as to control and mitigate risks of this hazardous waste. In the present study, the combustion of solid fuel derived from refinery oily-sludge is conducted numerically in a 2-D axisymmetric furnace. Investigating the effect of fuel particle diameter on the combustion process shows that with increasing particle diameter the maximum temperature reduces and the maximum temperature location goes farther from the furnace entrance. In order to investigate the effect of dewatering refinery oily-sludge on combustion properties, a study was conducted on the moisture content of fuel. The results show that an increase of 30% in moisture content in proximate fuel analysis reduces the maximum temperature by about 11%. Also, the effect of the fuel mass flow rate is investigated in the range of 0.15 gr/s to 0.29 gr/s. The results show that reducing the fuel mass load has a slight impact on maximum temperature of gas flow. However, CO and CO2 emissions experience a desirable decline.The study on combustion of solid fuels derived from oil-sludge shows that by making fuel preparation such as reducing the moisture content and using smaller particles, it is possible to exploit the heat value of oil sludge.

In 
degrees as divergence angle on combustion and fuel atomization characteristics, pollutant emissions, and performance in a heavy duty diesel engine have been investigated. Regarding compression ignition combustion simulation, a chemical kinetic mechanism consists of 61 species, and 296 reactions have been used. Results showed that with a decrease in ignition delay duration, most of the fuel burnt in diffusive mode, combustion process weakened, PM increased, and engine performance deteriorated. Also, by retarding the diesel injection timing simultaneous with an increase in in-cylinder pressure and temperature, relative span factor has been decreased. With the reduction of fuel spray width, diesel fuel droplets sprayed in a narrower region, and due to the high density of the spray region, more fuel droplets collide. In the following because of the increase in coagulation volume, PM increased. Furthermore, using group-hole nozzle strategy can improve fuel oxidation process but results in more UHC emission compared with the baseline case which must be considered as a disadvantage of using group hole nozzle concept.

In the present paper, a laminar counter-flow flame has been numerically investigated under the transcritical and supercritical conditions. The Cantera open source code has been used to calculate the flow field and the kinetic combustion solution. Furthermore, the energy equation, the thermodynamics and the transport properties have been modified for real gas solution. The thermodynamics properties, including density, enthalpy, and specific heat at constant pressure, are evaluated based on fundamental thermodynamics theories and the modified SRK equation of state (EOS). Transport properties, including thermal conductivity and dynamic viscosity, are estimated using Chung method. It can be seen that the pseudo-boiling phenomenon has been appeared in transcritical condition with real gas equations. The ideal gas solution is unable to capture this phenomenon. In the mixture fraction field, there is no major difference between the real gas and the ideal gas, which is important for solving the turbulent reacting flow by the flamelet models. However In the physical field, the difference between the real gas condition and the ideal gas is significant in terms of the position and dimensions of the flame for the transcritical state. For supercritical conditions in the physical field similar to mixture fraction field, there is no significant difference in the flame situation.

In this paper, NiMo nanocatalysts supported on waste material red mud with various amounts of boron promoter were synthesized via impregnation method and their catalytic activity were tested in hydrodesulfurization and hydrocracking processes. The prepared nanocatalysts were characterized using XRD, XRF, FESEM, BET and FTIR analysis. The results obtained by the analysis related to activation red mud confirmed that activation process significantly decreases amounts of Ca and Na in the red mud and increases its specific surface area. FESEM images confirmed the formation of nanoparticles with an average particle size of 18.45 nm. Techniques employed in NiMo/B-ARM nanocatalysts characterization revealed that boron addition resulted in uniform dispersion of particles on the support surface, an increase in the active phase and a decrease in the formation of Ni spineless. The catalytic activity of nanocatalysts in the hydrocracking process showed that with the addition of boron, liquid products obtained in the process contained higher amounts of kerosene and gasoline and lower amounts of heavy cuts. In addition, hydrodesulfurization performance measurements showed that NiMo/B-ARM with 0.8 wt.% boron had the best catalytic activity.

The flamelet library in FGM model is constructed based on mixture fraction and progress variable. This library facilitates to model the reactive flow precisely only in the case of two fuel/oxidizer in-flow streams. For the case of more in-flow streams, e.g. Sandia piloted flames fuel jet/ pilot/ air, it is needed to extend dimensions of the FGM library. This extension increase the size of stored data leads to higher computational cost. In this paper, the main motivation is to develop the Ignition Mixing Layer method (IML) to the Variable Ignition Mixing Layer (VIML) as the novel approach to generate the 2D FGM table for multi in-flow streams. Large Eddy Simulations of the Sandia D, E, and F with Reynolds number of 22400, 33600, and 44800 were conducted to validate this method. The LES results show a good agreement on the mean and variance of the mixture fraction and temperature. Therefore, the VIML is a successful model to simulate multi in-flow streams with 2D FGM library.