One of the main issues that has limited the use of hydrogen as an energy vector for a long time is its low energy density per unit of volume. Alternative chemical storage methods have been developed in recent years to overcome the limitations associated with compressed or liquified hydrogen storage. One of these is the Liquid Organic Hydrogen Carrier (LOHC), which utilizes organic hydrocarbons that can capture hydrogen (through an exothermic hydrogenation reaction) and release hydrogen (through an endothermic dehydrogenation reaction). In this paper, a 0D model of an internal combustion engine fueled with a mixture of hydrogen and methane was used to investigate whether the enthalpy of the exhaust gases can balance the heat rate required to self-sustain the dehydrogenation stage. Two LOHC+ compounds were considered, namely, Perhydro-dibenzyltoluene and Perhydro-N-Ethylcarbazole. Four different hydrogen-to-methane ratios were considered, assuming an engine maximum brake power ranging from 500 to 6000 RPM. An energy balance was performed, balancing the dehydrogenation heat rate and the exhaust gas cooling heat rate, in order to establish the minimum temperatures of the exhaust gases required to self-sustain the LOHC+ dehydrogenation. We demonstrated that the minimum exhaust temperatures required to self-sustain the process in different running regimes and at different hydrogen-to-methane ratios are lower than literature and experimental exhaust temperatures.
A suspension of ultrasonically agitated Titanium dioxide micrometer-sized powder has been introduced into a poly(methyl methacrylate) (PMMA) matrix by solvent (CHCl3) mixing under slow mechanical stirring, and the resulting suspension was used to cast free-standing PMMA/TiO2 composite films. Filler contents from 0 wt% to 7.5 wt% were selected, since TiO2 particles could not be previously suspended in chloroform at higher concentrations by ultrasonic agitation. Optical and dielectric properties of composites were determined by ultraviolet (UV)-visible and dielectric spectrometry. In the UV region, 450% improvement of UV absorption was achieved in the TiO2/PMMA composite compared with neat PMMA. The structural properties and hole-free volume of the composites were determined by X-ray diffractometry and positron annihilation lifetime spectroscopy, respectively. The particle size and homogeneous dispersion of the particles in the polymer matrix were related to the hole-free volume of the PMMA.
In this paper, two-dimensional computational fluid dynamics analyses were conducted to examine the rib effect on the performance of the NACA 0018 plain flapped airfoil. A mesh independence study was carried out and the Spalart-Allmaras turbulence model was selected for validation. Four various airfoil models were designed: M1 (airfoil without plain flap and rib structure), M2 (airfoil with rib structure), M3 (airfoil with a plain flap) and M4 (airfoil with a rib structure and plain flap). The performance of designed airfoils was calculated in terms of lift-to-drag (C_L/C_D) ratio. As a result, the plain flap significantly increased the lift coefficient (C_L) and drag coefficient (C_D). While the rib structure enhanced the aerodynamic performance of the non-flapped airfoil when the attack angle was greater than 12°, it increased the performance of the plain flapped airfoil at almost all attack angles. Furthermore, it was seen that the rib structure decreased C_D values of plain flapped airfoil at all attack angles and increased C_L values of plain flapped airfoil when the attack angle was greater than 2°.
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