The aim of this dissertation is to demonstrate the potential of novel measurement techniques based on the scanning of gamma-ray transmission in the investigation of axially-symmetric flow properties of granular materials in 3D hoppers. Furthermore, the results of the experimental investigations are compared on a strictly quantitative basis with Newtonian Dynamics (i.e. Discrete Element simulations) and Molecular Dynamics (i.e. kinetic gas theory calculations). Measurements were performed using two specially constructed scanner systems of different geometric configuration of gamma-ray sources and detectors(namely parallel and fan beam arrangements respectively). The fan beam scanner has been developed entirely in the Department of Chemical & Process Engineering by the author of this thesis and therefore a significant part of the thesis deals with major points concerning both hardware and software development as well as associated calibration procedures. Gas-phase continuous mono-disperse systems have been studied using (i) the full tomographic imaging technique which is able to produce 3D planar maps of voidage at selected heights of a storage vessel and (ii) the single profile absorptiometric technique capable of producing voidage profiles in both Cartesian and polar coordinates at much faster acquisition rates. Results were compared with earlier Distinct Element numerical simulations showing encouraging agreement in terms of both the absolute values of voidage and their spatial fluctuations as well as the geometric structure of the static and dynamic particle assemblies. Size segregation in air borne binary mixtures have been quantified using the novel dual energy photon technique which is capable of producing solids fraction profiles for each of the individual components of a binary mixture in addition to the voidage profiles. Spatial and temporal data on solids fractions in a binary mixture were analysed using methodology based on statistical mechanics principles which led to the definition of "micro-turbulence" during flow in terms of the self-diffusion velocities of individual solid components. This then allows the calculation of both the self- and mutual-diffusion coefficients used to quantify size segregation. These calculations were also compared with theoretical predictions based on the kinetic gas theory which was found to grossly over-predict the calculated diffusion coefficients in slow-shearing granular flows.

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More-electric aircraft have been the focus of considerable development in recent years. Increased utilisation of electrical systems on-board the latest generation of aircraft has seen an increase in fuel efficiency, through improved electrical derivation from the gas turbine engine and weight savings from the replacement of mechanical and hydraulic transmission systems. The advancement of power electronic and DC breaker devices has led to the reconsideration of DC power distribution systems for standalone networks. Aircraft can benefit from this through the reduced transmission losses, improved controllability and intelligent networking.Through the use of a multiphase synchronous generator, connected to a diode rectifier, a standalone DC network capable of providing power with redundancy can be produced. The aim of this research project is to investigate the effects that phase number, connection topology and winding pitch have on the behaviour of an AC generator connected to a passive diode rectifier. This thesis develops the methodology for determining the number of phases and the topology of the generator. Static and dynamic modelling is conducted through the use of computer finite element modelling and circuit simulation. The dynamic circuit simulation model is configured using parameters obtained from experimental data. The experimental test-rig, which is constructed to be reconfigurable in phase number, connection topology and winding pitch, is used to validate the simulation and provide detailed results on the steady-state operation of the generator-rectifier system. Open-circuit faults are introduced to assess the fault tolerance of the system and the effects of the inherent phase redundancy on the generator performance.

This thesis presents an experimental study and numerical predictions of the separated-reattaching flow around a bluff rectangular section. This laboratory configuration, chosen for its geometric simplicity, exhibits all main features of two-dimensional flow separation with reattachment. Detailed turbulent flow measurements of the mean and fluctuating flow field are reported. The measurement techniques used are: hot-wire anemometry, pulsed-wire anemometry and pulsed-wire surface shear stress probes. The separated shear layer appears to behave like a conventional mixing layer over the first half of the separation bubble, but exhibits a lower growth rate and higher turbulent intensities in the second half. In the reattachment region, the flow is found to be highly turbulent and unsteady. A finite difference method is used, in conjunction with a modified version of the TEACH code, to predict the mean flow field. Two discretization schemes are used: the hybrid-upwind differencing (HD) scheme, and the bounded-skew-hybrid differencing (BSHD) scheme. Laminar flow computations are performed for Reynolds numbers in the range 100 to 325. The HD computations underpredict the separation-bubble length by up to 35% as a result of false diffusion. The BSHD predictions, on the other hand, are in excellent agreement with the experimental results reported in the literature. Turbulent flow computations using the ƙ - ∈ turbulence model and the BSHD scheme result in a reattachment length about 30% shorter than the present measured value. When a curvature correction is incorporated into the model, a reattachment length of 4.3.D, compared to the experimental value of 4.7D, is predicted. The predicted mean flow, turbulent kinetic energy field and pressure distribution are in good agreement with experimental observations. An alternative method of analysis, based on the momentum integral technique, is presented. The method is not applied to the blunt-rectangular plate problem, but its use is illustrated for the simpler case of the flow in a sudden expansion, and promising results are obtained. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

The simulation of solitary wave run up on a slope is evaluated using a volume of fluid method in OpenFOAM. The simulated results are compared to experimental and nonlinear potential flow results for a 1 to 15 run up slope. The breaking region profile is shown to agree well with previous results except a larger jet tip calculated by OpenFOAM. Elevation through the run up of the wave is compared to the same data set. OpenFOAM shows a decreased peak amplitude when compared. A grid study is completed. The dissipation is investigated and a correction is applied to the OpenFOAM results. Corrected data shows a more accurate profile in the breaking region. Results shown indicate that more work is needed to improve two phase modeling within OpenFOAM for application to the case of solitary wave run up on a slope. Simulations are also completed for a vehicle fording case.

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Multiphase interleaving buck converters are widely used in today's industrial point-of-load (POL) converters, especially the microprocessor voltage regulators (VRs). The issue of today's multiphase interleaving buck converters is the conflict between the high efficiency and the fast transient in the phase inductor design. In 2000, P. Wong proposed the multiphase coupledinductor buck converter to solve this issue. With the phase inductors coupled together, the coupled-inductor worked as a nonlinear inductor due to the phase-shifted switching network, and the coupled-inductor has different equivalent inductances during steady-state and transient. One the one hand, the steady state inductance is increased due to coupling and the efficiency of the multiphase coupled-inductor buck converter is increased; on the other hand, the transient inductance is reduced and the transient performance of the multiphase coupled-inductor buck is improved. After that, many researches have investigated the multiphase coupled-inductor buck converters in different aspects. However, there are still many challenges in this area: the comprehensive analysis of the converter, the alternative coupled inductor structures with the good performance, the current sensing of converter and the light-load efficiency improvement. They are investigated in this dissertation. The comprehensive analysis of the multiphase coupled-inductor buck converter is investigated. The n-phase (n>2) coupled-inductor buck converter with the duty cycle D>1/n hasn't been analyzed before. In this dissertation, the multiphase coupled-inductor buck converter is systematically analyzed for any phase number and any duty cycle condition. The asymmetric multiphase coupled-inductor buck converter is also analyzed. The existing coupled-inductor has a long winding path issue. In low-voltage, high-current applications, the short winding path is preferred because the winding loss dominates the inductor total loss and a short winding path can greatly reduce the winding loss. To solve this long winding path issue, several twisted-core coupled-inductors are proposed. The twisted-core coupled-inductor has such a severe 3D fringing effect that the conventional reluctance modeling method gives a poor result, unacceptable from the design point of view. By applying and extending Sullivan's space cutting method to the twisted core coupled inductor, a precise reluctance model of the twisted-core coupled-inductor is proposed. The reluctance model gives designers the intuition of the twisted-core coupled-inductors and facilitates the design of the twisted-core coupled-inductors. The design using this reluctance model shows good correlation between the design requirement and the design result. The developed space cutting method can also be used in other complex magnetic structures with the strong fringing effect. Today, more and more POL converters are integrated and the bottleneck of the integrated POL converters is the large inductor size. Different coupled-inductor structures are proposed to reduce the large inductor size and to improve the power density of the integrated POL converter. The investigation is based on the low temperature co-fire ceramic (LTCC) process. It is found that the side-by-side-winding coupled-inductor structure achieves a smaller footprint and size. With the two-segment B-H curve approximation, the proposed coupled-inductor structure can be easily modeled and designed. The designed coupled-inductor prototype reduces the magnetic size by half. Accordingly, the LTCC integrated coupled-inductor POL converter doubles the power density compared to its non-coupled-inductor POL counterpart and an amazing 500W/in³ power density is achieved. In a multiphase coupled-inductor converter, there are several coupled-inductor setups. For example, for a six-phase coupled-inductor converter, three two-phase coupled inductors, two three-phase coupled-inductors and one six-phase coupled inductors can be used. Different coupled-inductor setups are investigated and it is found that there is a diminishing return effect for both the steady-state efficiency improvement and the transient performance improvement when the coupling phase number increases. The conventional DCR current sensing method is a very popular current sensing method for today's multiphase non-coupled-inductor buck converters. Unfortunately, this current sensing method doesn't work for the multiphase coupled-inductor buck converter. To solve this issue, two novel DCR current sensing methods are proposed for the multiphase coupled-inductor buck converter. Although the multiphase coupled-inductor buck converters have shown a lot of benefits, they have a low efficiency under light-load working in DCM. Since the DCM operation of the multiphase coupled-inductor buck converter has never been investigated, they are analyzed in detail and the reason for the low efficiency is identified. It is found that there are more-than-one DCM modes for the multiphase coupled-inductor buck converter: DCM1, DCM2 …, and DCMn. In the DCM2, DCM3 …, and DCMn modes, the phase-currents reach zero-current more-than-once during one switching period, which causes the low efficiency of the multiphase coupledinductor buck converter in the light load. With the understanding of the low efficiency issue, the burst-in-DCM1-mode control method is proposed to improve the light load efficiency of the multiphase coupled-inductor buck converter. Experimental results prove the proposed solution. / Ph. D.

In multiphase flow, the velocity differences between phases means unless the velocities of individual phases and concentrations are known, the true flow rate is practically impossible to obtain. At present, there is no single multiphase flow meter design capable of providing the required accurate measurements of oil, water, and gas fractions, as well as the phase velocities of wet gas. This research thesis introduces a prototype multi-phase flow metering system, named Uletechement. The main objectives of this research is to provide individual phase velocities of wet gas, and to combine with phase volume fraction measurements to obtain individual phase volume flow rates for gas and liquid Hydrocarbon (HC). The system comprised of a camera, laser source, synchronizer, computer data acquisition system and MATLAB based software, gas liquid chromatograph, seeds and tracer injecting devices. The gas-phase velocity is determined based on Particle Imaging Velocimetry (PIV). An algorithm that correlates the cameradeveloped through this research. The computer acquires two sequential image signals from the camera, and carries out the calculation of cross correlation between the images so that the average particle displacement within each interrogation area can be found. The average gas-phase velocity is subsequently obtained by integrating pixel velocity along the distance between two image frames obtained by a Charged Couple Device (CCD) camera. The product of phase velocity and phase concentration gives the flow rate of gas phase. The HC condensate flow is measured by injecting the fluorescent tracer - Silicone Carbide (SiC) at a known flow rate, which mixes only with the condensate. By sampling and analyzing samples further downstream, the ratio of the fluorescence of the injected and sampled condensates are subsequently determined. And the HC condensate flow rate can then be derived. The proposed method has been tested using a rig at Shell laboratory for the samples with a range of phase fractions and at several different velocities and flow rates. Due to the limitation of the rig, simultaneous measurement of the gaseous and condensate flow rate could not be done. But the experiments for liquid HC and gaseous phase measurements were carried out separately. However, this did not devalue the validation. The test results have been analysed and provided in the thesis, which confirmed the concept of proposed method.

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