Many countries use liquefied petroleum gas (LPG) for various purposes, such as cooking and heating. As the population and the need for energy grow, demand for LPG steadily increases. This situation causes the rise in LPG imports for countries with an insufficient local supply, including Indonesia. To overcome this problem, the Indonesian Government plans to substitute LPG fuel with dimethyl ether (DME). However, stoves and household burners widely used in Indonesia are designed for LPG. Thus it is necessary to study the fuel flexibility of the burners. Many experimental studies on the substitution of LPG with DME are reported in the literature, but few models have been developed to simulate it. This paper aims to evaluate the performance of reaction mechanisms developed to model DME diffusion flames with various burner temperatures ranging from 300 to 1500 K. It was found that existing models could simulate the chemical structure of the flame but could not predict the formation of enthalpy of combustion reactions.

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There have been many studies on the mechanisms of unsteady aerodynamics, such as leading-edge vortex (LEV) formation, wing-wake interaction, and spanwise flow. Spanwise flow can only be observed on three-dimensional wing models; however other phenomena such as LEV and wing-wake interaction can be captured using two-dimensional airfoil models. This study focuses on two-dimensional elliptical airfoil because this profile can generate counter-rotating vortices used by insects to generate aerodynamic forces. This research aims to analyze the drag production of two-dimensional elliptical airfoils flapping with bumblebee-inspired kinematics in asymmetrical normal-hovering mode at a typical Reynolds number range of . It is found that drag is generated during the downstroke while thrust during the upstroke. It is also found that the creation and shedding of counter-rotating vortices are closely related to the generation of thrust. The results also indicate that asymmetrical strokes can be used in normal hovering to minimize drag or produce thrust.