Study Of 3D Velocity And Temperature Measurement Of Micro Flow

Miniaturization, such as micro electrical and mechanical systems, microfluidics, mciro total analysis systems, has obtained the economies of materials, energy and reaction time. Meanwhile, more and more researchers have focused on micro flow in order to optimize industry designs and raise production efficiency. It is in urgent need of developping methods, exclusive to the micron-scale flow, of measuring velocity and temperature which are two critical parameters amongst. This thesis aims to simultaneously measure velocity and temperature of the micro flow. An integration was brought up of micro holographic particle tracking velocimetry (MicroHPTV), thermometry based on laser induced fluorescence (LIF) and fluorescent particle off-focus imaging techniques (FPFI). The optical experimental platforms were designed and built, and researches were performed on the followings:1. The principles and experiments of MicroHPTVFirstly, the depth of field of micro imaging systems and its influencing factors were expored. An analogy was drawn between the focusing criterion curves of reconstruction methods based on wavelet and convolution. It turned out that the reconstruction method by employing the focusing criterion of intensity gradiant local variance in the wavelet domain could be utilized to accurately determine z-positions. Secondly, the measurement errors of micro holography and micro HPTV were discussed by means of numerical simulation. Finally, micro holography and this reconstruction methods were applied to measure a dispersed particle field with a large depth of field and a tilted continuum. Lastly, the 3D velocity field inside a micro-channel was acqured with the use of MicroHPTV, and the experimental data conformed well with theoretical predictions.2. Experiemental study of the thermometry based on laser induced phosphorescence (LIP) and LIFThe causes of phosphorescence and fluorescence are similar, and thermometries baed on this two phenomena can be exploited. Firstly, a calibration curve of absolute phosphorescence intensity versus temperature was empoldered by using an industrialized phosphor, ZnS:Eu. Secondly, a solution mixture was prepared of Rhodamine B and Sulforhodamine-101. Two bands were chosen from by analysing the fluorescence spectrum at different temperatures with the utilization of a fluorescence spectrometer. The experimental system of two-color fluorescence thermometry was set up. And a calibration curve of fluorescence ratio versus temperature was thus procured. The temperature can be accordingly measured experimentally in combination of the calibration curve and interpolation methods.3. Simultaneous measurements of 3D velocity and temperatureDue to the small depth of field evoked by micro-objective, fluorescent particles can be imaged with many being defocused, and thus it ought to explore the FPFI characteristics. Both experimental and simulation results showed that the fluorescence ratio would not be affected by defocusing, though absolute intensity would be. Accordingly, it is possible to acquire 3D temperature field, with the combination of the capability of micro holography to determine 3D positions and the sole dependence of fluorescence intensity ratio on temperature, where the fluorescent particles could be located by matching their counterparts on the hologram. Finally, a simultaneous measurement of 3D velocity and temperature of a micro flow was implemented numerically to validate the feasibilty of the integration of MicroHPTV, LIF-based thermometry and FPFI techniques.