The existent gum content of the Fisher–Tropsch
synthetic
crude exceeded the standard seriously, affecting its transportation
and use. To determine the structure of the existent gum extracted
from the Fisher–Tropsch synthetic crude, elemental analysis,
Fourier transform infrared (FT-IR) spectroscopy, nuclear magnetic
resonance (NMR), and X-ray photoelectron spectroscopy (XPS) were employed
to determine the chemical structure of the gum. The Brown–Ladner
method is used to calculate the average structural parameters and
the average molecular formula of the existent gum. The results show
that the existent gum of the Fisher–Tropsch synthetic crude
is composed of heterocyclic aromatic hydrocarbons and short-carbon
paraffins. Compared with petroleum gums and coal tar gums, the existent
gum content of the Fisher–Tropsch synthetic crude has the characteristics
of high aromaticity, short side chains, and nitrogen-containing heterocycles.
After being oxidized, its aromaticity further increases, more closed
loops are formed, and the side chain is further shortened. This is
caused by a complex oxidation reaction during the oxidation process.
Molecular dynamics simulation calculations were performed to reveal
the T-stacked morphology of the existent gum of the Fisher–Tropsch
synthetic crude in a mixed solvent of acetone and toluene.
Recently, the Trailing-Edge Flap with Micro-Tab (TEF with Micro-Tab) has been exploited to enhance the performance of wind turbine blades. Moreover, it can also be used to generate more lift and delay the onset of stall. This study focused mostly on the use of TEF with Micro-Tab in wind turbine blades using NREL’s S-809 as a model airfoil. In particular, the benefits generated by TEF with Micro-Tab may be of great interest in the design of wind turbine blades. In this paper, an attempt was made to evaluate the influence of TEF with Micro-Tab on the performance of NREL’s S-809 airfoils. Firstly, a computational fluid dynamics (CFD) model for the airfoil NREL’s S-809 was established, and validated by comparison with previous studies and wind tunnel experimental data. Secondly, the effects of the flap position (H) and deflection angle (αF) on the flow behaviors were investigated. As a result, the effect of TEF on air-flow behavior was demonstrated by augmenting the pressure coefficient at the lower surface of the airfoil at flap position 80% chord length (C) and αF = 7.5°. Thirdly, the influence of TEF with Micro-Tab on the flow behaviors of the airfoil NREL’s S-809 was studied and discussed. Different Micro-Tab positions and constant TEF were examined. Finally, the effects of TEF with Micro-Tab on the aerodynamic characteristics of the S-809 with TEF were compared. The results showed that an increase in the maximum lift coefficient by 25% and a delay in the air-flow stall were accomplished due to opposite sign vortices, which was better than the standard airfoil and S-809 with TEF. Therefore, it was deduced that the benefits of TEF with Micro-Tab were apparent, especially at the lower surface of the airfoil. This particularly suggests that the developed model could be used as a new trend to modify the designs of wind turbine blades.
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