Using the precipitation method, we propose a new process for the preparation of high specific surface area and large pore volume ZnO nanoparticles in unconfined space with NH 4 HCO 3 and ZnSO 4 •7H 2 O as the reactants. The mixing performance of the reaction system was improved by gas atomization and continuous gas-based impinging streams before the precipitation reaction. By virtue of the gas environment and gas division, the obtained nanoparticles have a very good dispersion performance. Under optimal conditions, the ZnO nanoparticles were synthesized with a surface area of 88.89 m 2 /g, an average diameter of 7 nm, and a pore volume of 0.68 cm 3 /g. The influences of ZnSO 4 concentration, pressure, and gas−liquid ratio on the properties of the synthesized nanoparticles were studied. This study aims to provide a feasible and economical way to produce better properties in nanosized ZnO particles, which are widely applied as a new, multifunctional material.
With ever-tightening emission regulations, particulate filters are critical for internal combustion engines to meet the stringent particulate matter emission standards. A fast way to predict the filter performance, instead of numerically solving the governing differential equations, is needed for filter design and selection, real-time control, malfunction detection, and deposit load sensing. Approximate analytical solutions for wall flow filters, considering asymmetric channels and arbitrary deposit amounts, are derived by a technique of successive approximation. The analytical predictions of filter pressure drop have been validated against both steady state and transient experimental measurements. Moreover, over a broad range of filter operating conditions, the accuracy of the second-order analytical solution is validated by comparisons with the numerical predictions. The derivation also provides analytical expressions for channel and wall velocity profiles along the filter length. This study reveals the necessity of considering the nonlinear term of the governing equations when the actual open widths of inlet and outlet channels are quite different.
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