平行微通道中两相流的随机模型和检测方法

发布时间：2018-01-30 01:05

本文关键词： 微通道数量放大气液两相流弹状流型光检测随机模型稳定性　出处：《天津大学》2016年博士论文　论文类型：学位论文

【摘要】：反应器微型化是反应工程主要研究方向之一。微反应器实现工业实践采用并行操作的“数量放大”方式,它明显遇到各通道难匹配均匀流体的挑战,尤其是多相体系,结果并没有依通道个数复制而倍增,取而代之的是复杂的流体行为。论文致力于研究非均相微通道的放大操作,推进微流控技术商业化。研究内容如下:第一,通过实验和计算流体力学量化考查了由两条50 mm长,横截面为500μm方形的微通道以气液岔形分布器连接的网络中弹状流型的均匀性,将其定义为各通道生成气泡的齐次程度。实验结果表明,入口气速或液速的增加将会缩短各通道内气泡生成频率和长度的分布,另一方面恶化了通道间的均匀性。通过对压强场计算分析了流体在通道间的补偿作用,低流速下,补偿相对气泡频率来说常出现时滞,恶化了通道内的均匀性,并由快速摄像机记录的照片序列中捕捉到两相交汇处气柱前端的缩退现象,它对生成气泡过程的干扰随流速增加而减小。优化“千足虫”形式百条并行微通道的结构参数,发现明显增加液滴形成时落下台阶的高度能产生均匀尺寸的液滴,即便选择高粘度油相。第二,自搭建针对并行微通道的光检测系统,用于给随机模型和稳定性研究提供合理采样样本。系统能保证长期记录,自编程序快速准确计算,并依经过光纤的次序排列给出所有气液柱的长度、频率和速度的信息。第三,建立随机微分方程形式唯象模型描述由气液岔形分布器连接的两条并行微通道中流体随机分布的规律,并由自搭建光检测系统采样确定参数。随机方程与Fokker Planck方程联立推导出通道中各子流量的均值和方差的解析解。解随时间的变化趋势表明某相流体将会全部流入一条微通道;当考虑通道间相互干扰时,修正后的模型趋势符合实验现象。第四,以气泡生成频率表征通道的性能,考量了入口流量、通道个数和并行方式对分层和分岔不同类型的并行微通道中操作稳定性的影响。光检测系统抽样得时间序列通过计算最大Lyapunov指数证实了并行通道中气泡的混沌行为,混沌程度随通道个数或流量增加而增加。引入分形维数来量化通道的并行方式,建立避免混沌的操作区间关联式。另一方面,从方程角度选择Logistic形式组合方程和已有的种群竞争模型研究多通道中子流量分配稳定性,与实验相符。第五,基于微流控技术在基因水平和细胞水平提出检测低浓度突变型KRAS基因的方法。设计混合实验,PCR混合物中加肽核酸保证仅突变型扩增,测其荧光信号;制造所需的液滴生成芯片,和操纵液滴的包装芯片,皮升级注射芯片。
[Abstract]:Reactor miniaturization is one of the main research directions of reaction engineering. In the industrial practice of microreactor, the "quantity amplification" mode of parallel operation is adopted, which obviously meets the challenge of matching uniform fluid with different channels. Especially for multiphase systems, the results are not multiplied by the number of channels, but are replaced by complex fluid behavior. This paper focuses on the amplification of heterogeneous microchannels. Advance the commercialization of microfluidic technology. The contents of the research are as follows: first, through experiments and computational fluid dynamics quantitative examination from two 50 mm long. A 500 渭 m square microchannel is defined as the homogeneity of bubble formation in a network connected by a gas-liquid fork distributor, which is defined as the homogeneity of bubbles in each channel. The increase of inlet gas velocity or liquid velocity will shorten the distribution of bubble formation frequency and length in each channel, on the other hand, it will worsen the uniformity between channels. The compensation effect of fluid in the channel is analyzed by calculating the pressure field. At low velocity compensation often occurs time delay relative to the bubble frequency which deteriorates the uniformity in the channel and captures the phenomenon of the front end of the gas column at the intersection between the two phases in the image sequence recorded by the fast camera. The interference to the bubble formation process decreases with the increase of flow velocity, and the structural parameters of 100 parallel microchannels in the form of "millipede" are optimized. It is found that increasing the height of drop steps when droplets are formed can produce droplets of uniform size, even if high viscosity oil phase is selected. Secondly, a light detection system for parallel microchannels is built. It can be used to provide reasonable sampling samples for random model and stability research. The system can guarantee long-term record, compile a program to calculate quickly and accurately, and give the length of all gas-liquid columns in the order of passing through the fiber. Thirdly, the formal phenomenological model of stochastic differential equation is established to describe the random distribution of fluid in two parallel microchannels connected by gas-liquid bifurcated distributor. The parameters are determined by the sampling of self-built optical detection system. Stochastic equation and Fokker. The analytical solutions of the mean and variance of each subflow in the channel are derived by the Planck equation. The variation of the solution with time indicates that the flow of a certain phase will flow into a microchannel. When the interference between channels is considered, the modified model trend accords with the experimental phenomenon. 4th, the channel performance is characterized by bubble generation frequency, and the inlet flow rate is considered. The effects of the number of channels and the parallel mode on the operational stability of parallel microchannels of different types of delamination and bifurcation. The parallel channel is verified by calculating the maximum Lyapunov exponent of the time series sampled by the optical detection system. The chaotic behavior of bubbles. The degree of chaos increases with the increase of channel number or flow. Fractal dimension is introduced to quantify the parallel mode of channel, and the operation interval correlation to avoid chaos is established. The stability of multichannel neutron flux distribution is studied by selecting the Logistic form combination equation and the existing population competition model from the angle of equation, which is in agreement with the experimental results. 5th. Based on microfluidic technique, a method for detecting low concentration mutant KRAS gene was proposed at gene level and cell level. The fluorescence signal was measured. Make the required droplet generation chips, and manipulate droplet packaging chips, skin upgrade injection chips.
【学位授予单位】：天津大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TQ021.1

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