Based on the transport phenomena theory, the passive mixing of water and ethanol in different threedimensional microchannels is simulated numerically. The average variance of water volume fraction is used to index the...Based on the transport phenomena theory, the passive mixing of water and ethanol in different threedimensional microchannels is simulated numerically. The average variance of water volume fraction is used to index the mixing efficiency in the cases with different Reynolds number and different fabricated mixers. The results show that the efficiency of liquid mixing is progressively dependent on the convective transport as the Reynolds number increases. The efficiency of serpentine microchannel decreases with the increasing Reynolds number in the laminar regime. Altering the aspect ratio of channel inlet section has no significant effect on the mixing efficiency. Increasing the area of channel inlet section will cause the decrease of the mixing efficiency. The mixing in serpentine channels is the most efficient among three different mixers because of the existence of second flow introduced by its special structure.展开更多
In this paper the mixing of a sample in the curved microchannel with heterogeneous surface potentials is analysed numerically by using the control-volume-based finite difference method. The rigorous models for describ...In this paper the mixing of a sample in the curved microchannel with heterogeneous surface potentials is analysed numerically by using the control-volume-based finite difference method. The rigorous models for describing the wall potential and external potential are solved to get the distribution of wall potential and external potential, then momentum equation is solved to get the fully developed flow field. Finally the mass transport equation is solved to get the concentration field. The results show that the curved microchannel has an optimized capability of sample mixing and transport when the heterogeneous surface is located at the left conjunction between the curved part and straight part. The variation of heterogeneous surface potential ψn has more influence on the capability of sample mixing than on that of sample transport. The ratio of the curved microchanners radius to width has a comparable effect on the capability of sample mixing and transport. The conclusions above are helpful to the optimization of the design of microfluidic devices for the improvement of the efficiency of sample mixing.展开更多
Due to the scale effect, the uniform distribution of reagents in continuous flow reactor becomes bad when the channel is enlarged to tens of millimeters. Microfluidic field strategy was proposed to produce high mixing...Due to the scale effect, the uniform distribution of reagents in continuous flow reactor becomes bad when the channel is enlarged to tens of millimeters. Microfluidic field strategy was proposed to produce high mixing efficiency in large-scale channel. A 3D spiral baffle structure(3SBS) was designed and optimized to form microfluidic field disturbed by continuous secondary flow in millimeter scale Y-shaped tube mixer(YSTM). Enhancement effect of the 3SBS in liquid-liquid homogeneous chemical processes was verified and evaluated through the combination of simulation and experiment. Compared with 1 mm YSTM, 10 mm YSTM with 3SBS increased the treatment capacity by 100 times, shortened the basic complete mixing time by 0.85 times, which proves the potential of microfluidic field strategy in enhancement and scale-up of liquid-liquid homogeneous chemical process.展开更多
为了探索RBCC(Rocket Based Combined Cycle)亚燃模态条件下掺混燃烧性能,对多种工况进行了数值计算。对比分析了各工况下的燃烧室压力、掺混反应效率、总压损失等参数来分析燃烧室内部特性的变化。从数值模拟的研究中可以发现:由于RBC...为了探索RBCC(Rocket Based Combined Cycle)亚燃模态条件下掺混燃烧性能,对多种工况进行了数值计算。对比分析了各工况下的燃烧室压力、掺混反应效率、总压损失等参数来分析燃烧室内部特性的变化。从数值模拟的研究中可以发现:由于RBCC亚燃模态的特点,一次火箭高温羽流,使得喷注的燃料能够有效地雾化蒸发,通过支板的混合增强作用能有效地提高煤油燃料的掺混能力,凹腔又适当的延长了煤油在燃烧室的停留时间,形成有效的火焰稳定区域,两种有效的火焰稳定方式的结合能实现液体燃料稳定有效的燃烧,而且双凹腔前后组合也能提高燃料的掺混燃烧能力。从计算中还可以发现,合理地布置支板与凹腔的相对位置能提高燃料的掺混反应效率,实现燃料的充分燃烧,并对燃烧性能提高有明显的帮助。展开更多
基金Supported by the National Natural Science Foundation of China (No. 20299030).
文摘Based on the transport phenomena theory, the passive mixing of water and ethanol in different threedimensional microchannels is simulated numerically. The average variance of water volume fraction is used to index the mixing efficiency in the cases with different Reynolds number and different fabricated mixers. The results show that the efficiency of liquid mixing is progressively dependent on the convective transport as the Reynolds number increases. The efficiency of serpentine microchannel decreases with the increasing Reynolds number in the laminar regime. Altering the aspect ratio of channel inlet section has no significant effect on the mixing efficiency. Increasing the area of channel inlet section will cause the decrease of the mixing efficiency. The mixing in serpentine channels is the most efficient among three different mixers because of the existence of second flow introduced by its special structure.
基金Project supported by the National Natural Science Foundation （Grant No 10372090） and the Doctoral Program of Higher Education of China （Grant No 20030335001）.
文摘In this paper the mixing of a sample in the curved microchannel with heterogeneous surface potentials is analysed numerically by using the control-volume-based finite difference method. The rigorous models for describing the wall potential and external potential are solved to get the distribution of wall potential and external potential, then momentum equation is solved to get the fully developed flow field. Finally the mass transport equation is solved to get the concentration field. The results show that the curved microchannel has an optimized capability of sample mixing and transport when the heterogeneous surface is located at the left conjunction between the curved part and straight part. The variation of heterogeneous surface potential ψn has more influence on the capability of sample mixing than on that of sample transport. The ratio of the curved microchanners radius to width has a comparable effect on the capability of sample mixing and transport. The conclusions above are helpful to the optimization of the design of microfluidic devices for the improvement of the efficiency of sample mixing.
基金supported by the National Key Research and Development Program of China (2021YFC2101900 and 2019YFA0905000)National Natural Science Foundation of China (21908094, 21776130 and 22078150)+1 种基金Nanjing International Joint Research and Development Project (202002037)Top-notch Academic Programs Project of Jiangsu Higher Education Institutions。
文摘Due to the scale effect, the uniform distribution of reagents in continuous flow reactor becomes bad when the channel is enlarged to tens of millimeters. Microfluidic field strategy was proposed to produce high mixing efficiency in large-scale channel. A 3D spiral baffle structure(3SBS) was designed and optimized to form microfluidic field disturbed by continuous secondary flow in millimeter scale Y-shaped tube mixer(YSTM). Enhancement effect of the 3SBS in liquid-liquid homogeneous chemical processes was verified and evaluated through the combination of simulation and experiment. Compared with 1 mm YSTM, 10 mm YSTM with 3SBS increased the treatment capacity by 100 times, shortened the basic complete mixing time by 0.85 times, which proves the potential of microfluidic field strategy in enhancement and scale-up of liquid-liquid homogeneous chemical process.
文摘为了探索RBCC(Rocket Based Combined Cycle)亚燃模态条件下掺混燃烧性能,对多种工况进行了数值计算。对比分析了各工况下的燃烧室压力、掺混反应效率、总压损失等参数来分析燃烧室内部特性的变化。从数值模拟的研究中可以发现:由于RBCC亚燃模态的特点,一次火箭高温羽流,使得喷注的燃料能够有效地雾化蒸发,通过支板的混合增强作用能有效地提高煤油燃料的掺混能力,凹腔又适当的延长了煤油在燃烧室的停留时间,形成有效的火焰稳定区域,两种有效的火焰稳定方式的结合能实现液体燃料稳定有效的燃烧,而且双凹腔前后组合也能提高燃料的掺混燃烧能力。从计算中还可以发现,合理地布置支板与凹腔的相对位置能提高燃料的掺混反应效率,实现燃料的充分燃烧,并对燃烧性能提高有明显的帮助。
