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  • Author: Kai-Teng Wu, x
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Abstract

This study systematically investigates the slip phenomena in the centrifugal air compressor impellers by CFD. Eight impeller blades for different specific speeds, wrap angles and exit blade angles are designed by compressor design software to analyze their flow fields. Except for the above three variables, flow rate and number of blades are the other two. Results show that the deviation angle decreases as the flow rate increases. The specific speed is not an important parameter regarding deviation angle or slip factor for general centrifugal compressor impellers. The slip onset position is closely related to the position of the peak value in the blade loading factor distribution. When no recirculation flow is present at the shroud, the variations of slip factor under various flow rates are mainly determined by difference between maximum blade angle and exit blade angle, Δβmax-2. The solidity should be of little importance to slip factor correlations in centrifugal compressor impellers.

Abstract

Emulsion is an efficient encapsulation tool for enhancing the functional properties of essential oils (EOs). Herein, two two-dimensional cinnamon essential oil emulsions (from micro- to nanoscales) were emulsified by hydroxypropyl methylcellulose, and their antimicrobial and physicochemical properties were investigated. For the models of Escherichia coli CGMCC 1.0907, Salmonella enterica subsp. Enterica serovar Typhi (CICC 10867), Staphylococcus aureus CGMCC 1.0089, and Listeria monocytogene CGMCC 1.9144, the minimum inhibitory concentration (MIC) of the nanoemulsion was 31.25 μL/mL compared to that of the microemulsion (62.5–125 μL/mL) and pure oil (125–250 μL/mL), indicating the superiority of nanoemulsion as an antibacterial agent. The results showed that the highest activity was seen in the gram-positive L. monocytogenes whereas the lowest was in the gram-negative S. enterica. The identified properties of HPMC (hydroxypropyl methylcellulose) provide the potential for emulsifying and enhancing essential oils in light industries, especially for food processing.