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Fossil fuel reserves have decreased as a result of the rising demand for oil-based fuels. Biodiesel is one alternative renewable fuel that the government is looking for. Biodiesel has great potential as a fuel substitute for diesel. The raw materials are sustainable and kind to the environment. This study was carried out to ascertain the characteristics of biodiesel that are in accordance with Indonesian national standards for the use of alternative fuels. This was done in light of the ease with which raw materials can be used to make biodiesel. The esterification process is used to make biodiesel, which has several comparisons that are close to Indonesia's national standard, biodiesel purchased from CV. Artha Oil, 0.868 g/ml in density; 2,290 viscosity; acidity of 0.532; and has no water at all. According to SNI 7182:2015, the overall quality requirements for biodiesel have been met. [ABSTRACT FROM AUTHOR]

Blood flow disturbance and wall shear stress parameters have been widely related to the onset and progression of atherosclerosis in the carotid artery. Assessment of these parameters can be performed using computational fluid dynamics (CFD) simulation in three-dimensional models derived from scans of a luminal cast has been used to investigate the blood flow in the carotid artery bifurcation of human beings, which known as the typical location for the formation of recirculation flow and low-oscillatory wall shear stress. This study utilized pulsatile and cyclic velocity profiles at the inlet boundary condition, while the outlet boundary condition is defined to be constant pressure, that is 100 mmHg. Since the blood is a non-Newtonian fluid, the viscosity coefficient of blood is not constant, but rather as a function of the velocity gradient. Therefore, we employ the Carreau model as blood viscosity. The CFD simulation has shown the localization of atherosclerosis is associated with the local hemodynamics parameter, as there are recirculation flow and low wall shear stress present at the carotid bifurcation, particularly at the near bifurcation and carotid sinus. [ABSTRACT FROM AUTHOR]

Swirl vanes as a flame perturbation in a co-flow burner have been popularly used to enhance diffusion flame's physical properties, such as its flammability limit, flame stability, and efficiency. In addition, swirl vanes can enhance the recirculation between fuel and oxidizer, which maximizes the reaction and, thus, increase the combustion efficiency. In this study, the effect of swirl vanes with variations of 4, 6, and 8 blades on the flame visualization and temperature distribution is experimentally observed. The experiment was conducted in a co-flow burner using methane (CH4) with fuel velocity (uf) variations from 1.32 to 15.92 m/s, and the air velocity (ua) was varied from 0.9 to 1.4 m/s. The flame visualization of the diffusion flame at each parameter with three different swirl vanes configuration were analyzed and compared; furthermore, temperature distribution across the flame is also observed for each parameter. The results show that the increment of swirl vanes blades on the co-flow burner installation decreases the diffusion flame's height due to the recirculation from the turbulent flow on the flame structure. Moreover, there is a non-monotonic increment on the flame height with the increasing fuel velocity for all swirl vane blades configurations. Whereas, for the temperature distribution, higher blade amount increase the flame temperature with 397, 407, and 538 oC for swirl blade 4, 6, and 8, respectively. [ABSTRACT FROM AUTHOR]

Understanding the decreasing availability of fossil fuels, coupled with a better awareness of the negative effects of burning fossil fuels, has made room for substitute fuels from sustainable sources. As a sustainable fuel source, biodiesel can be applied directly to diesel engines without modifying the engine. The effect of using biodiesel on diesel engines requires a more in-depth study, especially B20 and B100 fuels derived from Crude Palm oil (CPO) which have different physical and chemical characteristics from other biodiesel. Therefore, this study will determine the effect of biodiesel use on exhaust gas emissions which include emissions of carbon monoxide (CO), hydrocarbon (HC), carbon dioxide (CO2), and smoke opacity. The fuel used was B100 (100% palm oil biodiesel) and B20 fuel (20% palm oil biodiesel+80% diesel) as a comparison. The test was carried out for 300 hours of operation, with a constant load of 4 kW halogen lamps. Based on the study results, overall engine with B100 fuel produces better emissions than engine with B20 fuel. At under no-load conditions for engines with B100 fuel, CO exhaust gas emissions were 16% lower than B20, and HC exhaust gas emission was 41% lower than B20. In contrast, at full load conditions, HC exhaust emission was 34% lower, and CO2 exhaust gas emission was 36% lower, and the opacity of the smoke produced was 11% lower when compared to a B20 engine. [ABSTRACT FROM AUTHOR]