Flutter analysis of compressor blades under travelling wave modes using an efficient fluid–structure interaction method

Flutter is a self-sustained vibration which could create serious damage to compressor blades.Improving the efficiency and accuracy of Fluid-Structure Interaction(FSI)method is crucial to flutter analysis.An efficient FSI method which combines a fast mesh deformation technology and Double-Passage Shape Correction(DPSC)method is proposed to predict blades flutter under traveling wave modes.Firstly,regarding the fluid domain as a pseudo elastic solid,the flow mesh deformation and blade vibration response can be quickly obtained by solving the governing equations of the holistic system composed of blade and pseudo elastic solid.Then,by storing and updating the Fourier coefficients on the circumferential boundary,the phase-lagged boundary condition is introduced into the computational domain.Finally,the aerodynamic stability for the blades of an axial compressor under various Inter-Blade Phase Angle(IBPA)is analyzed.The results show that the proposed method can effectively predict the characteristics of aerodynamic damping,aerodynamic force and blade displacement.And a conceptual model is proposed to describe the motion behavior of the shock wave.Compared with the multi-passage method,the proposed method obtains almost the same unstable IBPA interval and the blade displacement error is less than 3.4%.But the calculation time is significantly shortened especially in small IBPA cases.

Enhanced photocatalytic activity by the construction of a TiO2/carbon nitride nanosheets heterostructure with high surface area via direct interracial assembly

A TiO2 heterostructure modified with carbon nitride nanosheets （CN-NSs） has been synthesized via a direct interfacial assembly strategy. The CN-NSs, which have a unique two-dimensional structure, were favorable for supporting TiOa nanoparticles （NPs）. The uniform dispersion of TiO2 NPs on the surface of the CN-NSs creates sufficient interfacial contact at their nanojunctions, as was confirmed by electron microscopy analyses. In comparison with other reported metal oxide/CN composites, the strong interactions of the ultrathin CN-NSs layers with the TiO2 nanoparticles restrain their re-stacking, which results in a large specific surface area of 234.0 m2.g-1. The results indicate that the optimized TiOJCN-NSs hybrid exhibits remarkably enhanced photocatalytic efficiency for dye degradation （with k of 0.167 min-1 under full spectrum） and Ha production （with apparent quantum yield -- 38.4% for A = 400 ＋ 15 nm monochromatic light）. This can be ascribed to the improved surface area and quantum efficiency of the hybrid, with a controlled ratio that reaches the appropriate balance between producing sufficient nanojunctions and absorbing enough photons. Furthermore, based on the identification of the main active species for photodegradation, and the confirmation of active sites for H2 evolution, the charge transfer pathway across the TiO2/CN-NSs interface under simulated solar light is proposed.

Corrosion–wear behavior of a biocompatible magnesium matrix composite in simulated body fluid

Magnesium matrix composites are a new generation of biocompatible implant materials,but they will inevitably undergo simultaneous wear and corrosion in the human body.In this study,hydroxyapatite(Ca10(PO4)6(OH)2,HA)is used in a magnesium matrix composite to study its effects on the corrosion–wear behavior.Two samples(a magnesium alloy composed of Mg,Zn,and Zr(ZK60)alloy and ZK60/10HA composite)were fabricated using the powder metallurgy(PM)process.Their corrosion–wear behavior was investigated using the sliding wear test in a simulated body fluid(SBF).At all the sliding velocities tested,the corrosion–wear resistance of ZK60/10HA was superior to ZK60.At a sliding velocity of 942.5 mm/min,ZK60/10HA demonstrated a 42%improvement in corrosion–wear resistance compared to ZK60.For ZK60,the main wear mechanism under dry conditions was abrasion,while the wear mechanisms in the SBF were abrasion and corrosion.For ZK60/10HA,the wear mechanisms under dry conditions were abrasion and delamination,while in SBF they were mainly abrasion and corrosion,accompanied by slight delamination.The results indicated that HA particles can be used as an effective corrosion–wear inhibitor in biocompatible magnesium matrix composites.

Removal of trace Cr(VI) from water using chitosan-iron nanowires in porous anodic alumina

Chitosan-iron nanowires in porous anodic alumina （PAA） have been successfully prepared under ambient conditions as an ad- sorbent. The adsorbent was characterized by scanning electron microscopy, X-ray photoelectron spectroscopy and N2-BET surface area. The results showed that PAA can disperse and protect Fe0 nanorods from oxidation. The adsorption characteris- tics of trace Cr（VI） onto adsorbent have been examined at different initial Cr（VI） concentrations with pH 5. Batch adsorption studies show that the removal percentage of adsorbent for the removal of trace Cr（VI） is strongly dependent on the initial Cr（VI） concentrations. Langmuir and Freundlich isotherm models were used to analyze the experiment data. The adsorption of trace Cr（VI） by adsorbent is well modeled by the Langmuir isotherm and the maximum adsorption capacity of Cr（VI） is calcu- lated as 123.95 mg/g which is very closed to the experiment results. Intraparticle diffusion study shows that the intraparticle diffusion of adsorbent is not the sole rate-controlling step. The negative value of Gibbs free energy change,△G0, indicated that the process of Cr（VI） onto adsorbent was spontaneous. This work has demonstrated that chitosan-iron nanowires in porous anodic alumina as an adsorbent has promising potential for heavy metal removal at trace level.