<p> The voltage, current and torque equations of a two phase generalized machine are reviewed and the transformation are derived for the equivalent two phase commutator primitive of the three-phase slip-ring machine. The design of an SCR controlled inverter for speed variation of the two phase machine is presented and a method of comparing theoretical with practical values described.</p> / Thesis / Master of Engineering (MEngr)

<p> Preparations for an investigation of interfacial momentum transfer in two-phase two-component critical flows have been completed.</p> <p> The experiments involve the measurement of flow rates, axial pressure profiles, axial and transverse void fraction profiles, and axial wall shear stress profiles of steady-state gas-liquid critical flow in a vertical diverging nozzle. A photographic study is to be initiated to record the flow structure. The results of these experiments will be used to develop constitutive relations for interfacial momentum transfer.</p> <p> An experimental loop capable of circulating a gas-liquid mixture in a vertical test section was modified to suit the requirements of this investigation. The void fraction profiles are measured with a traversing gamma densitometer using a 20 mCi Co57 source. The wall shear stress profiles are obtained using the electrochemical method to measure the mass transfer coefficients of electrodes mounted flush with the test section wall. The liquid phase is an electrolyte and the gaseous phase can be air, nitrogen or freon. The latter is used to better approximate the densities of a steam-water flow.</p> <p> This report describes the required theory, measurement techniques, design and operation of the loop, and the experimental procedures.</p> / Thesis / Master of Engineering (MEngr)

<p> An investigation of the technique of obtaining the wall shear stress in a two-phase flow, by measuring the mass transfer coefficient at the wall with the electrochemical method, has been completed.</p> <p> The experiments involved the measurement of flow rates, pressure drops, void fractions and mass transfer coefficients, for a cocurrent upwards gas-liquid flow in a vertical tube, 13 mm in diameter. The liquid phase was an electrolyte consisting of 1.0 to 3.0 molar sodium hydroxide, and 0.005 to 0.010 equimolar potassium ferricyanide and potassium ferrocyanide. The gas phase was nitrogen. The flow regimes studied were slug, churn and annular.</p> <p> Emphasis is placed on the measurements obtained with the electrochemical method. Its application, advantages and disadvantages are detailed. A series of single-phase experiments were performed to explore the characteristics of the method and to serve as benchmarks for the two-phase experiments.</p> <p> The space-time-averaged values of the mass transfer coefficient were found to give the wall shear stresses to an accuracy of ±20%. Frequency analysis of the local fluctuating values indicate that measurements of the local mass transfer coefficient can be used for flow regime identification.</p> <p> The theoretical flow regime map of Dukler and Taitel successfully predicted the flow regimes. The correlations of Griffith and Wallis, and Lockhart and Martinelli as modified by Davis, predicted the pressure drops and void fractions to an accuracy ±15% when applied to the appropriate flow regimes. As a further exercise, the force interactions between the phases, referred to as the interfacial shear terms, were calculated from both the measured and predicted void fractions and pressure drops.</p> / Thesis / Master of Engineering (MEngr)

<p> The analysis of stepping motors using linear models has been simplified through identifications of the constants. Though the existing nonlinear models assuming a smooth air-gap machine may, in some cases, yield a fairly close prediction of the characteristics of a stepping motor, the models do not represent the actual motors which are essentially salient-pole motors. A new salient-pole nonlinear model is introduced. The analysis of permanent-magnet stepping motors using the nonlinear models has been simplified by assuming constant current sources. Dynamic behaviors of a permanent -magnet stepping motor are shown by phase-plane plots and step by step transient response plots.</p> <p> Computer control of stepping motors in both open-loop and closed-loop is discussed. The open-loop control has been demonstrated to be successful and a closed-loop control system using light-sensors as feedback has been designed.</p> / Thesis / Master of Engineering (MEngr)

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