Browsing by Subject "CFD Simulation"
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Item Experimental Measurement of Multiphase Flow and CFD Erosion Modeling in Electrical Submersible Pumps(2015-01-05) Pirouzpanah, SahandElectrical Submersible Pumps (ESPs) are widely being used in upstream oil production. To better understand the ESP pump?s behavior, two different ESPs, MVP-G470 and ESP-WJE1000, manufactured by Baker Hughes company have been studied experimentally and numerically to determine the pump and flow behavior in different operating conditions and for different working fluids. The MVP-G470 is a multi-vane electrical submersible pump which has been designed to increase the gas handling capacity of typical multiphase ESPs up to 70% gas volume fraction. Homogenized flow and finer bubbles produced by MVP pumps help the ESPs to delay the surging and gas lock condition to higher gas volume fractions and operate effectively. In this work, an experimental study on the performance of a 3-stage MVP along with detail study on the performance of two stages of the pump are performed. Overall pump performance for different operating conditions such as different inlet pressure, inlet gas volume fraction, water flow rate and speeds are performed for a mixture of water and air. Detail study of a stage performance is done on the first and second stage of the pump using conductivity and pressure measurements accompanied by high speed visualization. The data obtained from these measurements is employed to relate stage head degradation to effective parameters on the pump performance. The ESP-WJE1000 is a typical mixed flow ESP pump with a single vane rather than split-vane design used in MVPs. Numerical study on the erosion phenomena in this pump has been performed. The influence of key parameters on erosion in ESPs has been identified and a new model to predict the erosion rate at different pump locations has been introduced.Item Microfluidic Emulsification(2012-02-14) He, PengThis dissertation investigates the emulsification of aqueous liquid in immiscible organic liquid in various microfluidic environments, and addresses both experimental characterization and theoretical interpretation of the dynamics and design guidelines, as well as an application of microfluidic emulsification in fabrication of disk-like colloidal particle suspensions for studying its sedimentation behavior. In an attempt to understand the dynamics of drop formation in flow-focusing microfluidic channels, especially for an explanation of a transition from unique drop size to bimodal oscillating drop sizes as observed in the experiments, numerical simulation is developed to use the volume-of-fraction method to model the drop formation, and the simulation results help to interpret the transition in the theory of saddle-node transition in drop formation, as well as show the importance of selecting proper orifice length in flow-focusing microfluidic channel design. The electric technique for controlling of microfluidic emulsification is explored by a detailed study on low-frequency alternating-current electro-flow-focusing (EFF) emulsification in microfluidic channels. It is found that the droplet size variation is not a monotonic function of the electric field as in the case of direct-current EFF emulsification, which originates from the relaxation oscillation of the flow rate through the Taylor cone, and a power-law droplet size distribution was obtained at the voltage ramping-up stage. This emulsification process was modeled in analog to the charge accumulation and release in a resistor-capacitor electric circuit with an adjustable resistor, and the simulated data exhibit good agreement with the experiments. As an application of the microfluidic emulsification, a method of fabricating disk-like wax colloidal particle suspensions using electrospray is reported. Based on this technique, the first measurement of the hindrance function for sedimentation and creaming of disk-shaped colloids via the analytical centrifugation is reported. Disks align with the external flow right above the volume fraction of a few percent and this effect is extremely sensitive to the aspect ratio of disks. Due to this alignment effect, disk sedimentation/creaming demonstrate distinct trends in dilute and semi-dilute region.