This paper presents experimental and computational studies on the flow behavior of a gas-solid fluidized bed with disparately sized binary particle mixtures. The mixing/segregation behavior and segregation efficiency ...This paper presents experimental and computational studies on the flow behavior of a gas-solid fluidized bed with disparately sized binary particle mixtures. The mixing/segregation behavior and segregation efficiency of the small and large particles are investigated experimentally. Particle composition and operating conditions that influence the fluidization behavior of mixing/segregation are examined. Based on the granular kinetics theory, a multi-fluid CFD model has been developed and verified against the experimental results. The simulation results are in reasonable agreement with experimental data. The results showed that the smaller particles are found near the bed surface while the larger particles tend to settle down to the bed bottom in turbulent fluidized bed. However, complete segregation of the binary particles does not occur in the gas velocity range of 0.695-0.904 m/s. Segregation efficiency increases with increasing gas velocity and mean residence time of the binary particles, but decreases with increasing the small particle concentration. The calculated results also show that the small particles move downward in the wall region and upward in the core. Due to the effect of large particles on the movement of small particles, the small particles present a more turbulent velocity profile in the dense phase than that in the dilute phase.展开更多
In this study, the effects of composition and phase constitution on the mechanical properties and magnetic performance of AlCoCuFeNix(x = 0.5, 0.8, 1.0, 1.5, 2.0, 3.0 in molar ratio) high entropy alloys(HEAs)were inve...In this study, the effects of composition and phase constitution on the mechanical properties and magnetic performance of AlCoCuFeNix(x = 0.5, 0.8, 1.0, 1.5, 2.0, 3.0 in molar ratio) high entropy alloys(HEAs)were investigated. The results show that Ni element could lead to the evolution from face centered cubic(FCC), body centered cubic(BCC) and ordered BCC coexisting phase structure to a single FCC phase. The change of phase constitution enhances the plasticity but reduces the hardness and strength. One of the interesting points is the excellent soft magnetic properties of AlCoCuFeNixHEAs. Soft magnetic performance is dependent on composition and phase transition. AlCoCuFeNi1.5 alloy, achieving a better balance of mechanical and magnetic properties, could be applied as structure materials and soft magnetic materials(SMMs). High Curie temperature(>900 K) and strong phase stability below 1350 K of AlCoCuFeNi0.5 alloy confirm its practicability in a high-temperature environment. Atomic size difference(δ) is utilized as the critical parameter to explain the lattice strain and phase transformation induced by Ni addition.展开更多
基金The authors acknowledge support by the National Natural Science Foundation of China through the programs “Multiple scale analysis and scaling-up of direct coupled dual gas-solid fiuidized reaction systems” （Grant No. 20490202）； “Fundamental Research on the Chemical Engineering of Heavy Oil Staged Separation” （Grant No. 20525621）；“Simulation on transfer and coking processes in disengagers of resid fluid catalytic cracking units” （Grant No. 20406013）；the National Natural Science Foundation for Distinguished Young Scholars of China （Grant No. 20725620）.
文摘This paper presents experimental and computational studies on the flow behavior of a gas-solid fluidized bed with disparately sized binary particle mixtures. The mixing/segregation behavior and segregation efficiency of the small and large particles are investigated experimentally. Particle composition and operating conditions that influence the fluidization behavior of mixing/segregation are examined. Based on the granular kinetics theory, a multi-fluid CFD model has been developed and verified against the experimental results. The simulation results are in reasonable agreement with experimental data. The results showed that the smaller particles are found near the bed surface while the larger particles tend to settle down to the bed bottom in turbulent fluidized bed. However, complete segregation of the binary particles does not occur in the gas velocity range of 0.695-0.904 m/s. Segregation efficiency increases with increasing gas velocity and mean residence time of the binary particles, but decreases with increasing the small particle concentration. The calculated results also show that the small particles move downward in the wall region and upward in the core. Due to the effect of large particles on the movement of small particles, the small particles present a more turbulent velocity profile in the dense phase than that in the dilute phase.
基金supported by the National Natural Science Foundation of China(NSFC,Nos.51501085 and 51461030)
文摘In this study, the effects of composition and phase constitution on the mechanical properties and magnetic performance of AlCoCuFeNix(x = 0.5, 0.8, 1.0, 1.5, 2.0, 3.0 in molar ratio) high entropy alloys(HEAs)were investigated. The results show that Ni element could lead to the evolution from face centered cubic(FCC), body centered cubic(BCC) and ordered BCC coexisting phase structure to a single FCC phase. The change of phase constitution enhances the plasticity but reduces the hardness and strength. One of the interesting points is the excellent soft magnetic properties of AlCoCuFeNixHEAs. Soft magnetic performance is dependent on composition and phase transition. AlCoCuFeNi1.5 alloy, achieving a better balance of mechanical and magnetic properties, could be applied as structure materials and soft magnetic materials(SMMs). High Curie temperature(>900 K) and strong phase stability below 1350 K of AlCoCuFeNi0.5 alloy confirm its practicability in a high-temperature environment. Atomic size difference(δ) is utilized as the critical parameter to explain the lattice strain and phase transformation induced by Ni addition.
