Browsing by Subject "Separation"
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Item An Engineered Approach to Specialty Chemicals Purification(2016-08) Morgan, NathanHigh purity is a near-universal requirement throughout the specialty chemicals industry, essential for many of the applications we take for granted in our daily life. The purification process is often a significant portion of the manufacturing cost for many specialty chemicals, including organic semiconductors and pharmaceuticals. Reducing this manufacturing cost is a key step in the effort to efficiently produce the necessary materials for our modern world. This dissertation examines two key purification processes, thermal gradient sublimation and crystallization, in order to offer potential routes for process improvement. Thermal gradient sublimation is examined through the lens of organic semiconductors, which are often purified using this technique at the industrial scale. Interestingly, the sublimation process is limited by vapor phase transport and deposition, not solid phase mechanisms. A model for this process is developed, suggesting potential routes to efficient scale-up and separation improvements. This dissertation also proposes a new method for crystallization control, pressure-swing. In this approach, rapid changes in pressure are used to control solubility during the crystallization process. A model describing the changes in solubility due to these pressure changes is developed, and several process validation experiments are performed using pharmaceutical molecules as model systems. While these tests show an enhanced control of solubility, attempts to replicate experimental results obtained using traditional crystallization control are only partially successful when using the pressure-swing technique.Item Separation control in low pressure turbines using plasma actuators with passing wakes(2013-09) Burman, DebashishA Dielectric Barrier Discharge (DBD) plasma actuator is operated in flow over the suction surface of a Pack-B Low Pressure Turbine (LPT) airfoil at a Reynolds number of 50,000 (based on exit velocity and suction surface length) and inlet free-stream turbulence intensity of 2.5%. Preliminary characterization studies were made of the effect of varying actuator pulsing frequency and duty cycle, actuator edge effects, and orientation of the actuator with the flow. Flow control was demonstrated with the actuator imparting momentum opposite to the stream-wise flow direction, showing that it is possible to use disturbances alone to destabilize the flow and effect transition. No frequencies of strong influence were found over the range tested, indicating that a broad band of effective frequencies exists. Edge effects were found to considerably enhance separation control. Total pressure measurements of the flow without passing wakes were taken using a glass total-pressure tube. Corrections for streamline displacement due to shear and wall effects were made, and comparisons with previous hot-wire measurements were used to validate data. Performance features of conventional two-electrode and a novel three-electrode actuator configuration were compared. Hot-wire anemometry was used to take time-varying ensemble-averaged near-wall velocity measurements of the flow with periodic passing wakes. Corrections were made for near-wall effects, temperature effects, and interference of the electric field. The wakes were generated by a wake generator mechanism located upstream of the airfoil passage. The near-suction-surface total pressure field (flow without wakes) and velocity field (flow with wakes) in the trailing part of the airfoil passage, and the wall-normal gradient of these quantities, were used to demonstrate effective prevention of flow separation using the plasma actuator. Both flows (with and without passing wakes) showed fully attached flow (or very thin separation zones) when the actuator was activated. The flow with passing wakes and the actuator on showed relatively little time variation in the boundary layer, and qualitative similarities to the corresponding flow without passing wakes and with the actuator on were noted.