Laser Doppler velocimetry measurements and computational fluid dynamic (CFD) simulations of turbulent flows with free-surface vortex in an unbaffled dish-bottom stirred tank reactor agitated by a Rushton turbine are presented. Measurements of the three mean and fluctuating components of the velocity vector are made in order to characterise the flow field and to provide data for CFD model validation. An Eulerian-Eulerian multiphase flow model coupled with a volume-of-fluid method for capturing the gas-liquid interface is applied to determine the vortex shape and to compute the flow field. Turbulence is modelled using the standard k−ε, shear-stress transport and the differential Reynolds-stress model with two variants of the pressure-strain correlation. The predicted mean flow field obtained using all four turbulence models are on the whole similar and generally in good agreement with measurements. However, the Reynolds-stress models provide somewhat better predictions of the mean axial velocity. The turbulent kinetic energy is well predicted in the flow below the impeller, near the bottom of the tank; whereas it is underpredicted in the region close to the impeller and near the wall by all turbulence models.
A single-pulse shock
tube study of the pyrolysis of two different
concentrations of Chinese RP-3 jet fuel at 5 bar in the temperature
range of 900–1800 K has been performed in this work. Major
intermediates are obtained and quantified using gas chromatography
analysis. A flame-ionization detector and a thermal conductivity detector
are used for species identification and quantification. Ethylene is
the most abundant product in the pyrolysis process. Other important
intermediates such as methane, ethane, propyne, acetylene, butene,
and benzene are also identified and quantified. Kinetic modeling is
performed using several detailed, semidetailed, and lumped mechanisms.
It is found that the predictions for the major species such as ethylene,
propene, and methane are acceptable. However, current kinetic mechanisms
still need refinement for some important species. Different kinetic
mechanisms exhibit very different performance in the prediction of
certain species during the pyrolysis process. The rate of production
(ROP) is carried out to compare the differences among these mechanisms
and to identify major reaction pathways to the formation and consumption
of the important species, and the results indicate that further studies
on the thermal decomposition of 1,3-butadiene are needed to optimize
kinetic models. The experimental data are expected to contribute to
a database for the validation of mechanisms under pyrolytic conditions
for RP-3 jet fuel and should also be valuable to a better understanding
of the combustion behavior of RP-3 jet fuel.
Metal oxides are widely used in the fields of chemistry, physics and materials. Oxygen vacancy formation energy is a key parameter to describe the chemical, mechanical, and thermodynamic properties of...
Two-dimensional (2D) hybrid organic-inorganic perovskites (HOIPs) have attracted considerable interest for their promising applications for solar cells and optoelectronics. However, the fast and accurate prediction of basic band structure of...
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