Yuhong Jin

Hydrodynamics of cocurrent downflow circulating fluidized bed (CDCFB)

Abstract This paper presents an experimental study on the hydrodynamics of cocurrent downflow gas—solid suspension in a 140 mm i.d. Circulating Fluidized Bed (CDCFB) reactor. The influence of gas velocity and solid circulating rate on axial pressure drop, radial profiles of solid concentration and particle velocity has been examined. It is shown that solid flow in CDCFB is much more uniform than that in the riser.

Synthesis of plate-like calcium carbonate via carbonation route

A modified carbonation method was developed to synthesize plate-like CaCO3 particles in dilute Ca(OH)2 suspension. The influence of the initial Ca(OH)2 concentration, CO2 and temperature on the morphology of the precipitated CaCO3 particles was discussed. The variation of pH and the electrical conductivity with the carbonation time was investigated. Both of the experimental results and the thermodynamic calculation indicated that a low [Ca2+]/[C]T value, corresponding to a pH or temperature condition, is favorable for the formation of plate-like CaCO3 particles.

Investigation on slip velocity distributions in the riser of dilute circulating fluidized bed

Abstract The local slip velocity between gas and solid in the riser of a dilute circulating fluidized bed was investigated through simultaneous measurements of

INVESTIGATION AND MODELING OF COCURRENT DOWNFLOW CIRCULATING FLUIDIZED BED (DOWNER)

Abstract To simulate the gas and solids flow structure in downflow circulating fluidized beds or downer reactors, a two-dimensional two-phase turbulence hydrodynamic model (κ. — ϵ turbulence model) was developed. The influence of solid particles on the turbulence structure of the gas phase has been considered in deriving the hydrodynamic model. An improved numerical method (based on the SIMPLE method) is used for the flow model calculation. The predicted radial distributions or axial gas and particle velocities are in good agreement with the experimental data determined by LDV measurement. This turbulence hydrodynamic model provides a good description of the gas and solids flow structure in the downer.

Friction and wear behavior of several functional coatings under lubricated and elevated temperature conditions

Surface engineering techniques are routinely used for enhancing the performance of a diverse range of products. They are especially beneficial in tribological applications [1–2]. Mo-sprayed coating, nitrided coating and Cr-plated coating are three kinds of typical piston ring materials in IC engines and their tribological performances exert direct influences upon the power output, fuel economy and exhaust emission of the IC engines [3]. Many investigations have been conducted on the tribological behaviors for Mo-sprayed coating, nitrided coating and Cr-plated coating [4–8]. These investigations have characteristically involved (1) concentration on dry friction and wear behavior for these three coatings and few focus on their lubricated tribological performances; and (2) lower experimental temperatures generally than 200 ◦C though the real temperature for the piston ring can be as high as 320 ◦C. Thus it is of practical significance to study both friction and wear behavior for the Mo-sprayed coating, nitrided coating and Cr-plated coating lubricated with fully formulated engine crankcase oils at higher temperature. In the current study, the friction and wear behavior for the Mo-sprayed coating, nitrided coating and Cr-plated coating under lubricated and sliding contact conditions at a temperature of 320 ◦C were studied. In addition, chemical analyses were conducted on the wear tracks to understand the effect of the coating type on the tribochemical behavior of a friction modifier—molybdenum dialkyldithiocarbamate (MoDTC).

1D ultrafine SnO2 nanorods anchored on 3D graphene aerogels with hierarchical porous structures for high-performance lithium/sodium storage

SnO2 is considered as one of the most promising alternative anode materials for lithium ion batteries (LIBs) and sodium ion batteries (SIBs) due to high specific capacity, low discharge voltage plateau and environmental friendliness. In this work, 1D ultrafine SnO2 nanorods anchored on 3D graphene aerogel (SnO2 NRs/GA) composite is prepared through a simple reduction-induced self-assembly method in the solution of graphene oxide (GO), Vitamin C and SnO2 nanoparticles. Vitamin C plays an important role in the reduction of GO. The structural and morphological characterizations demonstrate that 1D ultrafine SnO2 nanorods are uniformly and tightly anchored on the surface of 3D graphene nanosheet aerogels. The unique 3D network structure as well as the synergistic effect between 3D graphene nanoshhet and 1D SnO2 nanorods endows the as-prepared SnO2 NRs/GA composite with the good electrochemical lithium/sodium storage performance. It delivers the high initial discharge capacity (1713 mA h g-1 at 0.1 A g-1 for LIBs and 539 mA h g-1 at 0.05 A g-1 for SIBs) and good cycle stability (869 mA h g-1 at 0.1 A g-1 after 50 cycles for LIBs and 232 mA h g-1 at 0.05 A g-1 after 100 cycles for SIBs). Moreover, the SnO2 NRs/GA composite exhibits excellent cycle stability for SIBs with a high reversible capacity of 96 mA h g-1 at as high as 1 A g-1 for 500 cycles. This work provides a simple method to fabricate the electro-active materials-graphene aerogel composites for high-performance LIBs and SIBs.

Effect of pressure on the structural properties of Li[Li0.1Ni0.35Mn0.55]O2

Li-rich cathode material Li[Li0.1Ni0.35Mn0.55]O2 was synthesized by a sol-gel method. The morphology and a-NaFeO2 type structure of the material at ambient conditions were characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The high-pressure behavior of the material was studied at pressure up to 19.7 GPa by using angle dispersive synchrotron X-ray powder diffraction (ADXD). The studies affirmed that the a-NaFeO2 type structure existed up to at least 19.7 GPa. Rietveld refinement analysis indicated that the c/a lattice parameter ratio decreased and the Li-O bond length shrunk with the increasing pressure, however, the Li+/Ni2+ ions exchange increased under elevated pressure. The pressure-volume data of the material were fitted to the third-order Birch-Murnaghan equation of state and bulk modulus obtained upon compression from the fitting was 117 (1) GPa.