Browsing by Subject "pumping"
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Item Design and Construction of a High Pressure System for Evaluating Multiphase Twin-Screw Pumps(2013-08-26) Hatch, Theodore IsaacTwin-screw pumps are currently sold by manufacturers without adequate data predicting the pump behavior when pumping multiphase mixtures. In light of the fact that pump behavior is known to change significantly under these conditions, a new closed-loop test facility has been designed and constructed to allow for testing of twin-screw pumps at high gas volume fractions. With minimal modification, the test facility can accommodate high pressure flows and oil-based liquids for testing. The closed-loop test facility supplies air and water to the inlet of an MR-200 twin-screw pump of which the performance characteristics are desired. The flow of air and water can be regulated to give the desired inlet pressure, outlet pressure, and gas volume fraction. The resulting mixture is driven to the test pump by its inlet suction. It then passes through the pump to a gravity separator, where it is separated into discrete liquid and gas phases. Inlet pressures up to seventy-five psig can be used, and with minimal modification, up to three-hundred psig. Total flow rates of up to six-hundred-fifty gallons per minute can be accommodated. A two-hundred horsepower electric motor provides the mechanical power for the pump. The test facility includes instrumentation and data acquisition equipment to monitor the pressures and temperatures at various points in the flow loop, as well as the flow rate and motor voltage of the pump. The closed-loop facility is validated by comparing the volumetric efficiency, mechanical efficiency, and pump effectiveness results to a previous open-loop facility that was also used to test the same twin-screw pump. Suggestions are given to replace an air valve to allow for more precise control of the air supply and to add a pulsation dampener that will moderate pressure oscillations. High pressure piping and tubing must be added for testing at higher inlet pressures.Item Rotordynamics of Twin-Screw Pumps(2013-02-26) Aboel Hassan Muhammed, AmeenTwin-screw pumps are positive displacement machines. Two meshing screws connected by timing gears convey the fluid trapped in the screw chambers axially from suction to discharge and force it out against the back pressure. Because of the screw geometry, the circumferential pressure field around the screws is not balanced, resulting in net dynamic and static pressures applied on the rotors. The research work presented here aims at building and verifying a model to predict both: (1) the exciting lateral hydrodynamic forces produced by the unbalanced pressure field, and (2) the rotor response due to those forces. The model rests on the screw pump hydraulic models for predicting the pressure in the screw chambers as a function of the discharge pressure. These models are extended to predict the steady state dynamic pressure field as a function of the rotational angle of the rotor. The dynamic force resulting from the dynamic pressure field is calculated and applied to the rotor as a set of super-synchronous periodic forces. The structural model of the screw, although nonsymmetrical, was found to be accurately represented by an axisymmetric equivalent structure. The rotor response to the dynamic super-synchronous forces is calculated to predict the pump rotordynamic behavior. The work in this dissertation presents: (1) the axisymmetric structural model of the rotors (2) the proposed dynamic pressure model, (3) the screw pump rotor response, (4) the experimental validation of the dynamic pressure model and rotor response. The topic of twin-screw pump rotordynamics is absent from the literature. The original contribution of the work presented in this dissertation to the field of rotordynamics includes: (1) demonstrating the adequacy of an axisymmetric model for modeling the screw section, (2) developing a model for predicting the dynamic pressure field around the screws, (3) characterization of the dynamic forces (synchronous and its harmonics) applied at the screw pump rotors, (4) predicting the dynamic response of twin-screw pump rotors due to hydrodynamic forces, (5) measuring the axial dynamic pressure in two circumferential planes around the screws to verify pressure predictions, (6) measuring the dynamic response of twin-screw pump rotor.