نشریه سوخت و احتراق
سال شانزدهم شماره 3 (پیاپی 44، پاییز 1402)

The general goal of this research is to find the right fuel composition containing bioethanol, gasoline, acetone and n-butanol in order to increase engine performance and reduce engine pollutants and energy production costs. In this research, in order to use sample fuels, a single cylinder engine was coupled with a 5kWh generator. A TDGC2-5kVA type variable resistor and a 1kW heater were used to load the motor. By measuring the power of the motor, the amperage and voltage of the electricity were measured. It should be noted that the engine test was performed at full load (100% load) and a fixed speed of 1500 rpm as the rated speed of the engine. Based on the obtained results, adding n-butanol from 2 to 5% caused a relative decrease and from 5 to 7% caused a relative increase in braking power. The lowest amount of braking power was obtained in the range of combined additives of bioethanol and n-butanol without acetone. The highest amount of braking power was obtained in the highest percentage of n-butanol, acetone and bioethanol additives in the gasoline fuel sample. In this interval, the thermal efficiency was also higher than the control fuel sample and the special braking fuel consumption was also lower than the control fuel sample. The highest amount of nitrogen monoxide emission was relatively in the sample of fuels containing combined additives of bioethanol and n-butanol. The lowest amount of nitrogen monoxide emission occurred in the fuel sample containing the combination of bioethanol and acetone. By adding n-butanol to fuel samples, the emission of nitrogen oxides increased. The results also showed that the effects of these additives can be highly dependent on engine design, operating conditions, and the specific blend ratios used. This research paves the way for several future research directions in the field of alternative fuel additives and spark ignition engines.

The purpose of this study is to investigate the conditions governing a flameless combustion furnace with natural gas fuel. In this article, by changing the arrangement and distances of the four symmetrical air inlets from the central fuel inlet, The concept of eddy dissipation model with coefficient correction has been used to model combustion with reduced chemical kinetics DRM22. Two symmetrical cross arrangements "X" and "+" configuration, were determined to minimize the dead space in the furnace for air inlets. Lower limit of the air and fuel inlet distance was assumed to be 12 mm and the upper limit of this distance was 36 mm in the simulation. Most of all, by examining the combustion parameters, the proposed geometry was selected for the construction of the furnace. The recirculation factor (Kv) has been increased by 2.6 times compared to the base furnace. Also, the maximum temperature has decreased by 5% and the difference between the maximum and average temperature by 77 Kelvin compared to the basic furnace, and this indicates better temperature uniformity. Also, the maximum heat of reaction of specified point in the furnace has increased by 63% compared to the base furnace and indicates the higher potential of the furnace in heat treatment. It is possible to extend results of this research to natural gas industrial furnaces.

The field has long acknowledged the detrimental effects of entropy waves, including heightened NOx emissions, combustion chamber instability, and noise production. Entropy oscillations, when accelerated, serve as a source of indirect noise, exacerbating the combustion chamber's instability. A computational study delved into the entropy noise within a lean-premixed H2/ ethylene burner to better comprehend these phenomena. Utilizing flamelet and large Eddy Simulation, the study shed light on the behavior of entropy waves and their impact on combustion dynamics. It particularly examined how various thermal and fluid conditions affect entropy noise in both thermally convective and adiabatic combustion chambers, focusing on temperature. In-depth analysis was conducted on elements like the strength of inlet turbulence, stoichiometric ratio, and the preheating level of the unburned mixture. The findings revealed intriguing connections between these factors and the acoustic system response. Notably, an increase in equivalence ratio, and temperature led to a heightened auditory response, suggesting that such conditions foster the generation and spread of entropy noise. Conversely, the study found that high turbulence intensity at the amplifier negatively impacted the transmission of entropy oscillations, thereby reducing the auditory response. This suggests that intense turbulence can interfere with entropy wave propagation, lessening their potential to produce significant acoustic effects.

This investigation explores the mixing dynamics of transcritical and supercritical jets under excitation in cryogenic bi-shear coaxial injector. The study identifies dominant frequencies in the flow field and oscillates the inlet velocity of propellants, LN2 and GN2. Utilizing a 35-degree sector and applying Large Eddy Simulation (LES) alongside the Peng-Robinson equation of state and Chung method, enables the assessment of evaluate the thermodynamic and transport properties in real cryogenic fluids. Results show that oscillations enlarge Kelvin-Helmholtz instability-induced vortex structures, particularly in the supercritical gas jet, enhancing turbulent mixing and, the thermal-shield undergoes localized distortions, improving heat transfer, enhancing mixing, and shortening the jet core.
.

Commercial activated carbon available in Iran has been used for adsorptive desulfurization from model fuel, and in order to increase its adsorption efficiency, surface modification has been done by Fe impregnation on its surface. The Fe loading on activated carbon surface has successfully increased the adsorption efficiency due to the formation of π complex and direct sulfur-metal interaction, and this adsorbent removed 80% of dibenzothiophene from model fuel, in comparison with unmodified activated carbon has 17% more adsorption performance for dibenzothiophene. Also, adsorption capacity of Fe/GAC and GAC adsorbents are 320mg/g adsorbent and 250mg/g adsorbent, respectively.
 
.

In this paper, the numerical simulation of combustion in one of the industrial furnaces of Kermanshah Oil Refining Company has been carried out in order to investigate the cause of high temperature damage to its damper and provide a solution to solve this problem. At first, the current situation has been investigated. For this purpose, the numerical model of furnace and burner has been produced and numerical simulations have been carried out to check the current situation. The agreement between the actual factory data and the numerical simulation data is acceptable. In the next step, by changing the burner and changing the shape of the flame, numerical simulations have been performed in order to solve the problem. The obtained results show that by changing the burner and using 4 smaller burners but with a longer flame, the shape of the flame becomes branched and with the increase of heat transfer caused by this situation, the temperature at the place where the damper is installed decreases by about 170 degrees Celsius. This decrease in temperature can solve the problem of damaging the damper and softening the structure connecting it to the flue.
 
.