FUEL AND COMBUSTION
Year:2018 | Volume:10 | Issue:3 |Papers Count:8

The purpose of the present study is to produce biodiesel from fish-waste oil and methanol by combining mechanical stirring and microwave as a technique to accelerate this process. In this research, a microwave system was used including microwave source, stirrer, spiral tube and decanter. With the help of this system, the effects of multiple parameters on the conversion of fatty acid to methyl ester is investigated. These parameters include 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). Analyzing the obtained results is performed using the response surface method and Box Behnken layout in Design Expert 10.0 software. After analyzing the data and optimizing the biodiesel production reaction, the highest percentage of biodiesel conversion (92.62%) was found in the catalyst concentration of 1.13%, the reaction time of 24.61 minutes, 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 work, the effects of various engine loads, engine speeds, EGR rates and biodiesel ratio in biodiesel-diesel fuel blends on the emissions and performance of a 4-stroke 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 NOX emissions while using biodiesel and EGR has been 63.76% with B10 fuel blend and 30% EGR rate. Simultaneously using EGR and biodiesel reduced CO emission by 4.04, 12 and 1.73% for low, medium and high engine speed. Using biodiesel decreased the HC emissions, so it compensated the increase of HC due to EGR. The highest reduction in HC emission levels while simultaneously using EGR and biodiesel 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 comprising 18 EV burners. To such aim, k-e turbulent model along with finite rate Eddy dissipation combustion model and a global two- step kinetic mechanism are used to simulate the reacting flow field in the combustor. Primary investigations show that the global two-step mechanism underestimates CO concentration at the combustor outlet by several orders of magnitude. Therefore, the global mechanism is tuned to better capture CO emission. 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-dimethyldibenzothiophene (4, 6-DMDBT) on Al2O3 and Ni/Al2O3 adsorbents from model diesel fuel (n-hexane-4, 6-DMDBT) is investigated in a batch system. At first, the best alumina is selected from four types of commercial alumina by adsorption process in the batch system, and then to enhance the adsorption capacity of alumina, its surface is modified with different percentages of nickel using wetness impregnation method. All adsorption experiments are studied in batch systems and equilibrium data is obtained after 24 hours in each system. UV-visible spectroscopy is used to determine the adsorption capacity, and XRD, XRF and nitrogen adsorption- desorption analyses is used to characterize the adsorbents. The results indicate that the highest adsorption capacity is obtained when 0.15 gram of nickel is loaded on 1 gram of alumina (0.15 gr Ni/gr Al2O3). Adsorption equilibrium data is fitted with Langmuir, Freundlich and Dubinin- Radushkevich isotherms and Langmuir isotherm is found to best describe the adsorption process and predict maximum adsorption capacity of 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 computing 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 Manifold (FGM), 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 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 that demonstrates the enormous potential of this method. In addition, submerged flames within a porous medium are simulated to show the applicability of the presented method in predicting reacting flow in variable enthalpy problems. The predicted solid and gas temperatures are comparable with experimental values that demonstrates the ability of the FGM method.

The alcohol- based fuels have 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 blending ratio of fusel oil- diesel regarding the performance and emissions of spark ignition engine using response surface methodology based on CCD design. In this research, experimental investigations have been performed with different fusel oil- diesel blends (0%, 5%, 10%, 15% and 20%), different loads (0%, 25%, 50%, 75% and 100%) and different engine speeds (1400, 1700, 2000, 2300 and 2600 rpm). The multi-objective optimization was performed to maximize the power and torque, and minimize BSFC, NOx, UHC and CO emissions. The best combination of engine parameters was found to be 11.57% fusel oil, 40% load and 2264 rpm engine speed. The optimal values were 1.9 kW, 10.9 N.m, 354.5 g/kWh, 0.19, 54.5, 2.34 and 87.7 (V%) for power, torque, BSFC, CO, UHC, CO2 and NOx emissions, respectively. The results showed that fusel oil usage increased power and torque. It was also found that both NOx and UHC emissions decreased.