Hydrodynamic cavitation,a newly developed process intensification technique,has demonstrated immense potential for intensifying diverse physical and chemical processes.In this study,hydrodynamic cavitation was explore...Hydrodynamic cavitation,a newly developed process intensification technique,has demonstrated immense potential for intensifying diverse physical and chemical processes.In this study,hydrodynamic cavitation was explored as an efficient method for the formation of sub-100 nm oil-in-water(O/W) emulsions with high stability.O/W emulsion with an average droplet size of 27 nm was successfully prepared.The average droplet size of O/W emulsions decreased with the increase of the inlet pressure,number of cavitation passes and surfactant concentration.The formed emulsion exhibited admirable physical stability during 8 months.Moreover,the hydrodynamic cavitation method can be generalized to fabricate large varieties of O/W emulsions,which showed great potential for large-scale formation of O/W emulsions with lower energy consumption.展开更多
The size of the bulk nanobubbles(typically 100 nm-200 nm in diameter)is below the optical resolution of the typical microscopes,which makes it difficult to make a direct observation of them and differentiate between t...The size of the bulk nanobubbles(typically 100 nm-200 nm in diameter)is below the optical resolution of the typical microscopes,which makes it difficult to make a direct observation of them and differentiate between the nanoparticles and the nanobubbles.In this work,a nanoparticle tracking analysis(NTA)system is developed for tracking and sizing the bulk nanobubbles,and more broadly,the Brownian diffusing particles.We demonstrate the capabilities of the NTA in characterizing the nanoparticles through systematic validation of accuracy and resolution.We particularly exhibit its unique advantages in detecting the polydisperse nanoparticle populations.Then the nucleation and the thermodynamic stability of the bulk nanobubbles are systematically studied by the NTA system.The bulk nanobubbles smaller than 600 nm in size are generated via the ultrasonication method.It is shown that both the ultrasonic cavitation treatment time and amplitude,essentially,the energy input,favor the nucleation of the bulk nanobubbles with a more concentrated size distribution,a higher concentration,and a smaller hydrodynamic size.The temperature dependence of the bulk nanobubbles over a wide range from 25°C to 70°C is explored.It is found that the nanobubble first shrinks in size significantly and then the size keeps approximately constant with the increasing temperature,showing a narrow size distribution.The transition temperature is around 45°C.Further,as an open system,the NTA is a potential tool in the study of the dynamic behavior of the bulk nanobubbles in situ,such as the coalescence and the collapse.展开更多
Journal bearings operating in hot environments and at high temperatures experience accelerated degra- dation of lubricating oils. In such situations, dry granular particulates have emerged as potential media for provi...Journal bearings operating in hot environments and at high temperatures experience accelerated degra- dation of lubricating oils. In such situations, dry granular particulates have emerged as potential media for providing lubrication in journal bearings in place of lubricating oils. Granular particulates do not degrade thermally, even at considerably high temperatures. This work explores the static and dynamic perfor- mance characteristics of elliptical-bore journal bearings lubricated with granular particulates. It is found that a bearing lubricated with a larger size （2 μm） particles offers better performance compared with that using smaller size （1μm） particles. Bore ellipticity reduces the load-carrying capacity and increases side leakage and the coefficient of friction; however, rotor stability is marginally improved at low eccentricity ratios （〈0.6）, followed by significant improvement at high eccentricity ratios （〉0.6）.展开更多
文摘Hydrodynamic cavitation,a newly developed process intensification technique,has demonstrated immense potential for intensifying diverse physical and chemical processes.In this study,hydrodynamic cavitation was explored as an efficient method for the formation of sub-100 nm oil-in-water(O/W) emulsions with high stability.O/W emulsion with an average droplet size of 27 nm was successfully prepared.The average droplet size of O/W emulsions decreased with the increase of the inlet pressure,number of cavitation passes and surfactant concentration.The formed emulsion exhibited admirable physical stability during 8 months.Moreover,the hydrodynamic cavitation method can be generalized to fabricate large varieties of O/W emulsions,which showed great potential for large-scale formation of O/W emulsions with lower energy consumption.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11988102,91852202)the Tencent Foundation through the XPLORER PRIZE.
文摘The size of the bulk nanobubbles(typically 100 nm-200 nm in diameter)is below the optical resolution of the typical microscopes,which makes it difficult to make a direct observation of them and differentiate between the nanoparticles and the nanobubbles.In this work,a nanoparticle tracking analysis(NTA)system is developed for tracking and sizing the bulk nanobubbles,and more broadly,the Brownian diffusing particles.We demonstrate the capabilities of the NTA in characterizing the nanoparticles through systematic validation of accuracy and resolution.We particularly exhibit its unique advantages in detecting the polydisperse nanoparticle populations.Then the nucleation and the thermodynamic stability of the bulk nanobubbles are systematically studied by the NTA system.The bulk nanobubbles smaller than 600 nm in size are generated via the ultrasonication method.It is shown that both the ultrasonic cavitation treatment time and amplitude,essentially,the energy input,favor the nucleation of the bulk nanobubbles with a more concentrated size distribution,a higher concentration,and a smaller hydrodynamic size.The temperature dependence of the bulk nanobubbles over a wide range from 25°C to 70°C is explored.It is found that the nanobubble first shrinks in size significantly and then the size keeps approximately constant with the increasing temperature,showing a narrow size distribution.The transition temperature is around 45°C.Further,as an open system,the NTA is a potential tool in the study of the dynamic behavior of the bulk nanobubbles in situ,such as the coalescence and the collapse.
文摘Journal bearings operating in hot environments and at high temperatures experience accelerated degra- dation of lubricating oils. In such situations, dry granular particulates have emerged as potential media for providing lubrication in journal bearings in place of lubricating oils. Granular particulates do not degrade thermally, even at considerably high temperatures. This work explores the static and dynamic perfor- mance characteristics of elliptical-bore journal bearings lubricated with granular particulates. It is found that a bearing lubricated with a larger size （2 μm） particles offers better performance compared with that using smaller size （1μm） particles. Bore ellipticity reduces the load-carrying capacity and increases side leakage and the coefficient of friction; however, rotor stability is marginally improved at low eccentricity ratios （〈0.6）, followed by significant improvement at high eccentricity ratios （〉0.6）.
