RESUMEN
To comprehensively control the corner separation and mid-span boundary layer (BL) separation, this study proposed and evaluated two new flow control configurations. One is a slotted configuration composed of blade-end and whole-span slots, and the other is a combined configuration with end-wall BL suction and whole-span slot. Additionally, the adaptability of the combined configuration to the lower blade solidity (c/t) condition was verified. The results indicate that both the slotted configuration and combined configuration can eliminate the mid-span BL separation, but a better reduction in the corner separation can be observed in the combined configuration. The two configurations can remove the concentrated shedding vortex and reduce the passage vortex (PV) for the datum cascade, but the wall vortex (WV) will be generated. By contrast, the combined configuration has weaker WV and PV than the slotted configuration, which contributes to further reducing the corner separation. In the combined configuration with a c/t of 1.66 and 1.36, the total pressure loss is reduced by 38.4% and 42.1%, respectively, on average, while the averaged static pressure rise coefficient is increased by 16.2% and 17.6%, respectively. This is advantageous for enhancing the working stability and pressure diffusion capacity for compressors. Besides this, the combined configuration with lower c/t can achieve a stronger pressure diffusion capacity and smaller loss than the higher c/t datum cascade. Therefore, the combined configuration is advantageous to the improvement of the aero-engine thrust-to-weight ratio through decreasing the compressor single-stage blade number.
RESUMEN
The hydrogen-based direct reduction of iron ores is a disruptive routine used to mitigate the large amount of CO2 emissions produced by the steel industry. The reduction of iron oxides by H2 involves a variety of physicochemical phenomena from macroscopic to atomistic scales. Particularly at the atomistic scale, the underlying mechanisms of the interaction of hydrogen and iron oxides is not yet fully understood. In this study, density functional theory (DFT) was employed to investigate the adsorption behavior of hydrogen atoms and H2 on different crystal FeO surfaces to gain a fundamental understanding of the associated interfacial adsorption mechanisms. It was found that H2 molecules tend to be physically adsorbed on the top site of Fe atoms, while Fe atoms on the FeO surface act as active sites to catalyze H2 dissociation. The dissociated H atoms were found to prefer to be chemically bonded with surface O atoms. These results provide a new insight into the catalytic effect of the studied FeO surfaces, by showing that both Fe (catalytic site) and O (binding site) atoms contribute to the interaction between H2 and FeO surfaces.
RESUMEN
In this research, the feasibility of using nano-montmorillonite (MMT) in asphalt binders was investigated in terms of rheological properties, thermomechanical properties, and chemical structure composition. Different doses of MMT were added to the base asphalt and styrene-butadiene-styrene (SBS) asphalt as test subjects. The effect of nanomaterials on the high-temperature resistance of asphalt binders to permanent deformation was analyzed from dynamic mechanical rheology using the multiple stress creep recovery (MSCR) test. The sessile drop method test based on surface free energy (SFE) theory was employed and thermodynamic parameters such as surface free energy, cohesive work, and adhesion work were calculated to analysis the change in energy of the asphalt binder. In addition, changes in the chemical structure and composition of the asphalt binder were examined by Fourier transform infrared (FTIR) and gel permeation chromatography (GPC) tests. The results showed that MMT can effectively enhance the high-temperature elastic recovery and plastic deformation resistance of the asphalt binder. The intercalation structure produced in the asphalt binder enhanced the overall cohesive power and adhesion to the aggregate. The anchoring effect of the intercalation structure resulted in an increase in the macromolecular weight of the binder was demonstrated, indicating that MMT enhanced the overall intermolecular forces of the binder. In addition, the molecular crystal structure was characterized by characteristic functional groups in the infrared spectra, while demonstrating that no chemical reaction occurs during the modification of the binder by the nanomaterials.