نشریه سوخت و احتراق
سال دهم شماره 3 (پیاپی 21، زمستان 1396)

The purpose of the present study is to produce biodiesel from fish waste oil and methanol by combination of mechanical stirrer and microwave as a technique to accelerate this. In this research, a microwave system was used including microwave source, stirrer, spiral tube and decantor. With the help of this system, the effect of molar ratio of alcohol to oil (4 to 1, 6 to 1 and 8 to 1), catalyst concentration (0.5, 1 and 1.5 weight percent of oil), reaction time (5, 15 and 25 min) and microwave time (0.5, 1.5 and 2.5 min) on the conversion of fatty acid to methyl ester. For analyzing the obtained results, the response surface method and Box Behnken layout were used in Design Expert 10.0 software. After analyzing the data and optimizing the biodiesel production reaction, it was found that the highest percentage of biodiesel conversion (92.62%) was found in the catalyst concentration of 1.13%, the reaction time of 24.61, the molar ratio of alcohol to oil of 5.55 and the microwave time of 0.5 minute. The regression model between independent variables and dependent variable (percent conversion) was obtained as a quadratic equation with R2 = 0.9953.

In this research work effect of the different engine loads, engine speeds, EGR rates and biodiesel ratio in biodiesel diesel fuel blend on the emissions and performance parameters of a 4stroke single cylinder diesel engine have been investigated. The RSM method has been used to optimize the EGR rate, biodiesel percent and engine working mode. The highest decrease in NO_xemissions while using the biodiesel and EGR has been 63.76% with B10 fuel blend and 30% EGR rate. The simultaneous usage of EGR and biodiesel reduced CO emission of the engine by 4.04, 12 and 1.73% for low, medium and high engine speed. The biodiesel was decreased the HC emission of the engine and so it compensated the increase of HC due to EGR. The highest reduction in HC emission levels while using EGR and biodiesel simultaneously, has been 54.05%. It is noticeable that the total amount of the smoke emission levels while using EGR and biodiesel did not change considerably. The optimized condition proposed by the RSM method has been 45.3% engine load, 2080 rpm engine speed, 14.97 % EGR rate and 5.43% biodiesel blend with diesel fuel.

The main objective of the present paper is to predict CO emission in a stationary gas turbine combustor. The gas turbine combustor comprises 18 EV burners. To such aim, k-ϵ turbulent model along with finite rate eddy dissipation combustion model and a global two step kinetic mechanism are used to simulate the combustor flow field. Primary investigations show that the global two step mechanism underestimates CO pollutant at the combustor outlet by several orders of magnitude. Therefore, the global mechanism is tuned to capture CO pollutant. To such aim, temperature exponent of the Arrhenius form of reaction rate is tuned as a function of equivalence ratio. Investigations show that the tuned global mechanism using the present methodology accurately predicts CO emission in the stationary gas turbine at various operating conditions. The obtained results show that modifications of the global mechanism have no effect on the overall flame shape and flame lift-off distance.

In this work, adsorption of 4,6-dimethyldibenzotiophene (4,6-DMDBT) on Al2O3 and Ni/Al2O3 adsorbents from model diesel fuel (n-hexane-4,6-DMDBT) was investigated in the batch system. At the first, the best alumina selected between 4 type of commercial alumina by adsorption process in the batch system, and then for enhance the adsorption capacity of alumina its surface modified with different percentage of nickel by wetness impregnation method. All adsorption experiments studied in batch systems and equilibrium data obtain after 24 hours in each system. For determination of adsorption capacity, UV-visible spectroscopy used and for characterization of adsorbents, we used XRD, XRF and nitrogen adsorption-desorption analyses. The results indicated that the highest adsorption capacity obtain when 0.15 gram of nickel load on 1 gram alumina (0.15gr Ni/gr Al2O3). Adsorption equilibrium data fitted with Langmuir, Freundlich and Dubinin-Radushkevich isotherms and Langmuir isotherm best described this adsorption process and predicted maximum adsorption capacity 1.253 and 15.97 mg/g for Al2O3 and Ni/Al2O3 respectively.

Homogeneous charge compression ignition (HCCI) is regarded as the next generation combustion trend in terms of high thermal efficiency and low emissions. It is difficult to control autoignition and combustion because they are controlled primarily by the chemical kinetics of air/fuel mixture. In this study, a homogeneous mixture of natural-gas and air was used in a compression ignition engine to reduce NOx emissions and improve thermal efficiency. In order to control ignition timing and combustion, a small amount of Dimethyl Ether (DME) was mixed with the natural-gas. In this paper, a multi-dimensional computational fluid dynamics (CFD) model coupled with chemical kinetics mechanisms was applied to investigate the effects of various temperatures, pressures, equivalence ratios and fuel compositions on the combustion performance and emission characteristics of an HCCI engine. The mixture could run the engine quietly and smoothly over a wide range of loads. Under the present test conditions, finite amount of DME was necessary in order to achieve ignition of the mixture. In addition, thermal efficiency was higher than that of methane fueled engine, when the DME proportion was optimized. NOx emissions were extremely low, however, the emissions of total unburned hydrocarbon were high.

In this study a new method for computation of reacting flow in porous media is presented, which can be considered as a combination of two existing reduced chemistry approaches i.e. the flamelet and manifold approach, to speed up flame calculations. This method, referred to as the Flamelet-Generated Manifoldý (FGM) method, shares the idea with the flamelet approaches that a multi-dimensional flame may be considered as a set of one-dimensional flames. The thermo-chemical variables are stored in a database, which can be used in subsequent flame simulations. During flame simulation, conservation equations have to be solved for the controlling variables only. Test results of a two-dimensional methane/air flame shows that detailed chemistry computations are reproduced very well by using FGM with only one progress variable, apart from the enthalpy to account for energy losses. Using the FGM method, the computation time has been reduced several times in simulating flames, demonstrating the enormous potential of the method. Submerged flames within a porous medium simulated to show the applicability of presented method in predicting reacting flow in variable enthalpy problems. The predicted solid and gas temperatures are comparable to experiment, demonstrating the ability of the FGM method.

The Alcohol based fuels has attracted the attention of alternative fuel researchers. Fusel oil is an alcohol based fuel collected as a by-product during bioethanol production. The main objective of this study is to determine the optimal blend ratio of fusel oil–gasoline regarding the performance and emissions of spark ignition engine using response surface methodology based on CCD design. In this research work, experimental investigations have been performed with different fusel oil–diesel levels (0%, 5%, 10%, 15% and 20%), different load (0%, 25%, 50%, 75% and 100%) and different engine speed (1400, 1700, 2000, 2300 and 2600 rpm).The multi-objective optimization was performed to maximize the power, torque and minimized BSFC, NOx, UHC and CO emission. The best condition of engine parameters was 11.57% for fusel oil, 40% load and 2264 rpm engine speed. The optimal values were 1.9 kW, 10.9 N.m, 354.5 g/kW h, 0.19, 54.5,2.34 and 87.7(V%) for power, Torque, BSFC, CO, UHC, CO2 and NOx emissions respectively. were prolonged. The results showed that fusel oil usage increased power and torque. It was found that both NOx and UHC emissions decreased.