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30 results on '"Xia, Huanming"'

8. Numerical study on active droplet generation governed by pulsatile continuous‐phase flow.

Author

Zhang, Yanyin, Wang, Jiamin, Wu, Jiawei, and Xia, Huanming

Subjects
PULSATILE flow, MICROFLUIDICS, VISCOSITY
Abstract

Precise control on the droplet generation is an important issue for the application of droplet microfluidics. Passive formation of droplets depends on multiparameters. The droplet size and generation frequency highly correlate to each other, raising the control difficulty. In comparison, the active method through external perturbations is more flexible. In this work, the droplet generation governed by pulsatile continuous‐phase flow is numerically studied. The effects of the pulsation amplitude and frequency, as well as the velocity and viscosity of the discrete fluid are investigated. Different modes of droplet generation (viz., sub‐periodic, period‐1, and period‐n modes) are identified, the underlying mechanisms are interpreted. This method may be applied in various droplet microfluidic/microreactor systems to improve the droplets control and manipulations. [ABSTRACT FROM AUTHOR]

Published
2024
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16. A comparative discussion of different designs of passive micromixers: specific sensitivities of mixing efficiency on Reynolds numbers and fluid properties

Author

Xia Huanming, Wang Zhiping, and Wu Jiawei

Subjects
Engineering, business.industry, Microfluidics, Flow (psychology), Reynolds number, 02 engineering and technology, Mechanics, 010402 general chemistry, 021001 nanoscience & nanotechnology, Condensed Matter Physics, Secondary flow, 01 natural sciences, 0104 chemical sciences, Electronic, Optical and Magnetic Materials, Viscosity, symbols.namesake, Planar, Hardware and Architecture, symbols, Electronic engineering, Electrical and Electronic Engineering, Microreactor, 0210 nano-technology, business, Mixing (physics)
Abstract

Fluid mixing enhancement is an important topic of microfluidics and microreactor technologies. Though many micromixers based on different mechanisms have been reported so far, most investigations were conducted case by case due to the diversity of applications. For a more comprehensive understanding of the problem, this paper presents a comparative discussion of five different passive micromixers, including a planar spiral mixer, a planar split-and-recombine (SAR) mixer, a 3D serpentine mixer, a 3D SAR mixer, and a 3D mixer with divergent geometries. The involved mixing mechanisms include Dean flow/secondary flow, SAR process and viscous interfacial instabilities. From a geometric perspective, this study compares (i) planar and fully 3D structures, (ii) single channels whose cross section preserve connectedness and interconnected multiple sub-channels, (iii) microchannels with and without divergent structures. Key characteristics of the designs are highlighted. The influence of Reynolds number, fluid viscosity and viscosity ratio are also discussed. As the discussed micromixers cover a wide range of fluid mixing conditions, it also serves as a mini-review, providing useful reference on the selection of optimum design for different applications.

Published
2017

20. Passive Micromixer Platform for Size- and Shape-Controllable Preparation of Ultrafine HNS

Author

Zhao, Shuangfei, Chen, Cong, Zhu, Peng, Xia, Huanming, Shi, Jinyu, Yan, Fanyuhui, and Shen, Ruiqi

Abstract

A passive micromixer platform, with the assistance of controllable mixing performance, was used for the preparation and morphology control of ultrafine explosives. This method is characterized by high mixing efficiency, safe and easy processing, low solvent consumption, and fast preparation and screening. The preparation of hexanitrostibene (HNS) in the micromixer platform has obvious advantages over the beaker in terms of particle size and particle size distribution. The particle size of HNS prepared in the platform ranges from 91 to 255 nm, while that of the HNS prepared in a beaker ranges from 106 to 615 nm with the same antisolvent/solvent ratio. The particle size of HNS can be controlled to about 100, 150, and 200 nm, and the crystal shape can be controlled to nanoscale, two-dimensional nanosheet, and short rod crystal. This study demonstrated the feasibility of a safe and efficient way of controlling the particle size and crystal shape of explosives.

Published
2024
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27. Micro‐Segmented Flow Technology Applied for Synthesis and Shape Control of Lead Styphnate Micro‐Particles.

Author

Zhao, Shuangfei, Yan, Fanyuhui, Zhu, Peng, Yang, Yong, Xia, Huanming, Shen, Ruiqi, and Ye, Yinghua

Subjects
LEAD styphnate, X-ray diffraction
Abstract

Abstract: In this study, the technology of micro‐segmented flow was applied for continuous synthesis safely and shape control accurately to lead trinitroresorcinate (LTNR) particles. Besides, a micro chemical reaction and crystallization system were built. Crystal shape control technology of LTNR and micro‐segmented flow technology were first combined using the system. Additionally, the effects of the flowing rate and chemical additives on LTNR micro‐particles preparation were researched for shape control. The LTNR micro‐particles were analyzed by XRD, DSC, laser scanning confocal microscope and laser particle size analyzer. The results shows that the LTNR particles size can be controlled from 20 to 400 μm by the flow rate and the concentration of hexadecyl trimethyl ammonium bromide (CTAB), while the shape of LTNR can be controlled by the concentration of glycerol and CTAB. Besides, there is a good linear relationship between the size and the activation energy. This illustrates that the LTNR particles with smaller size are more stable and have higher heat release. This study demonstrated the power of micro‐segmented flow for generation of LTNR micro‐particles with high quality and for tuning of particle properties. [ABSTRACT FROM AUTHOR]

Published
2018
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28. Numerical analysis and characterization of a Wankel pump as a miniaturized mixer

Author

Xia Huanming, Stephen Wan, and Pankaj Kumar

Subjects
Chemistry, Rotor (electric), business.industry, Mechanical Engineering, Wankel engine, Mechanics, Computational fluid dynamics, Electronic, Optical and Magnetic Materials, Vortex, law.invention, Flow velocity, Mechanics of Materials, Control theory, law, Particle, Streamlines, streaklines, and pathlines, Electrical and Electronic Engineering, business, Mixing (physics)
Abstract

In the present study, particle track simulations of inert particles belonging to two species (binary mixing), carried out using a commercially available CFD code indicate that pumps based on Wankel type geometries (Wankel pumps) are capable of functioning as mixers, as well as pumps; and hence such devices could also drive a semi-batch micro-reactor system. The numerical results reveal that mixing quality improves as the particles loop through the pump cavity and then saturates after a time, and that mixing rate increases with rotor speed. Examination of the structure of the flow-field suggests that the underlying mechanism of mixing is a combination of the stretching (resulting in particle dispersion) and folding of streamlines into Taylor-like vortex pairs, accounting for the vertical symmetry in the particle distributions. Differences in the flow structure, detected by plots of fluid velocity components, could account for differences in particle distributions generated for various rotor speeds.

Published
2015

29. Elastic Magnetic Membrane for Improved Mixing in Microwells

Author

Zhi Chong, Zhuang, Sim, Wee Jun, Ting Yeo, Ze, Ho Li, King, Huan Ng, Sum, Xia, Huanming, Wong, Teck Neng, Hiang Loh, Ngiap, Beng Tor, Shu, Hwa Tan, Say, and Nguyen, Nam-Trung

Abstract

We demonstrate a simple method to fabricate elastic magnetic membrane which could be used to enhance mixing in microwells of a microtitre plate. The magnetic membrane was fabricated using an off-the-shelf flexible magnetic sheet and the elastomer polydimethylsiloxane (PDMS). In order to demonstrate the concept, the membrane was integrated in a single microwell to act as an actuator for improved mixing. A customized electromagnet was used to allow contactless and robust actuation. The membrane can achieve a unidirectional deflection of about 120 µm when a 3 A direct current (DC) is applied. Periodic deflection is achieved by applying a square wave alternating current (AC) of 100 Hz and ±3 A. In the dynamic case, the membrane follows the square wave with the same frequency and provides a peak-to-peak deflection of about 115 µm. The observed oscillation was able to mix the fluorescent dye and an aqueous solution within 18 seconds. The proposed method has the potential to be implemented in microtiter plate arrays to improve mixing.

Published
2014

30. Numerical analysis and characterization of a Wankel pump as a miniaturized mixer.

Author

Stephen Wan, Xia Huanming, and Pankaj Kumar

Subjects
*SURFACE analysis, *MICROFLUIDICS, *PARTICLE tracks (Nuclear physics), *COMPUTATIONAL fluid dynamics, *FLOW velocity
Abstract

In the present study, particle track simulations of inert particles belonging to two species (binary mixing), carried out using a commercially available CFD code indicate that pumps based on Wankel type geometries (Wankel pumps) are capable of functioning as mixers, as well as pumps; and hence such devices could also drive a semi-batch micro-reactor system. The numerical results reveal that mixing quality improves as the particles loop through the pump cavity and then saturates after a time, and that mixing rate increases with rotor speed. Examination of the structure of the flow-field suggests that the underlying mechanism of mixing is a combination of the stretching (resulting in particle dispersion) and folding of streamlines into Taylor-like vortex pairs, accounting for the vertical symmetry in the particle distributions. Differences in the flow structure, detected by plots of fluid velocity components, could account for differences in particle distributions generated for various rotor speeds. [ABSTRACT FROM AUTHOR]

Published
2015
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