To study the effect of doping hexagonal boron nitride (h-BN) on the thermal properties and insulation resistance of epoxy resin (EP) and the mechanism of this effect, h-BN/epoxy composites with h-BN content of 0, 10, 20, 30, and 40 phr were prepared. Meanwhile, the corresponding molecular dynamics model of h-BN/epoxy composites was established, and the thermal conductivity, volume resistivity, glass transition temperature, and microstructure parameters of h-BN/epoxy composites were obtained. When the h-BN content is 40 phr, the thermal conductivity of h-BN/epoxy composite is increased by 138% compared to pure EP, and the glass transition temperature is increased by 76 K. At the same time, doping h-BN will reduce the insulation performance of EP. However, the lowest volume resistivity of h-BN/epoxy composite is still 1.43 × 1015 Ω·cm, and the EP composite still has good insulation performance. The fraction free volume and mean square displacement of EP decrease with the doping of h-BN, which indicates that h-BN can hinder the movement of molecular segments of EP, which is the reason for the increase in glass transition temperature.
Experimental overall performances on a double helix screw pump are presented and discussed, focusing on the leakage flow for two different rotational speeds. A comparison between experimental and URANS CFD approaches is performed in order to check the CFD closure models’ validity. Some specific local flow characteristics are extracted from the numerical results which give explanations about leakage backflows inside the screws and local distortion at the pump inlet section.
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