This effort explores novel sub-resolution particle center estimation algorithms for Digital Particle Tracking Velocimetry (DPIV). The errors of these new methods were classified through Monte-Carlo simulations. These schemes provide direct measurements of the apparent particle image diameter and the subpixel position. The new methods significantly reduce the bias error due to pixel discretization, thus reducing the total error in the position and sizing measurement compared to the classic three point and least squares Gaussian estimators. In addition, the accuracy of the least-squares fits were essentially independent of the true particle diameter and significantly reduced the particle position error compared with current estimation schemes. The results of the Monte Carlo simulations were validated in a high pressure spray atomization experiment. / Master of Science

A pneumatic particulate collection system harnesses the energy associated with the release of a compressed gas to transport particulate to a collection chamber. In an effort to improve the efficiency of a previously designed collection system, high speed imaging in conjunction with computational fluid dynamics (CFD) was utilized to highlight design deficiencies. Areas of recirculation within the collection device as well as impingement of the sampling surface were observed through the testing and CFD analysis. The basis of the improved collection system was conceived through research of pneumatic transport and the deficiencies found through testing and simulation. An improved rectangular-duct-styled system was designed in three main stages. A variety of filters used to contain the desired particulate were characterized through testing for use in simulations as well as fluids calculations. The improved system was then analyzed utilizing compressible and incompressible flow calculations and design iterations were conducted with CFD to determine the final parameters. The final design was simulated with a multiphase flow model to examine the particulate entrainment performance. The improved collection system efficiently expanded and developed the gas flow prior to the collection area to employ the particulate entrainment process. The final design was constructed with an additive manufacturing process and experimentally tested to validate the simulations and flow calculations. The testing proved that the final design operated purely on particulate entrainment and collected only the top layer of particles as simulated. The improved collection system eliminated all areas of flow recirculation and impingement of the particle bed to provide a more efficient sampling device. / Master of Science

Electric vehicles aim to carry the torch into a sustainable future. An optimized cooling system is crucial to an Electric Drive Unit (EDU). A smartly designed cooling system will deliver high-performance, efficient and long-lasting EDUs at lower costs. One way to achieve that is to have an integrated cooling system. When the electric motor and transmission share a common oil, the oil returning from the transmission side is aerated due to spraying and splashing. This aeration affects the pump performance and may reduce the cooling performance of the oil. Thus, this thesis is initiated to understand the impact of aeration on heat transfer.     Oil aeration is the presence of air in oil. This aeration depends on the air content and bubble sizes mixed in the oil. Typically, there is also some amount of dissolved air in any oil. Depending on the type of aeration, the oil will appear lighter than its usual colour and have a very foamy texture, showing a change in the properties of the fluid, for example density, viscosity and heat transfer.    An experimental setup is built in order to replicate and study the effect of aeration on local heat transfer. A flat channel with rectangular cross-section is designed with three parts – a bottom plate, a flow spacer channel and a top transparent plate. The oil and air are mixed before they enter the channel and then heated using thin film heaters. A groove within the bottom plate houses an insulating material, the thin film heater, a thermocouple touching the heater and a thermochromic liquid crystal sheet facing the fluid mixture. The thermocouple gives temperature readings from a single point between the heater and the insulating material. Meanwhile, the liquid crystal sheets come in different desired temperature ranges and change in colour from red to blue to show the surface temperatures over an area. So, the surface temperature of the mixed fluid flow can be recorded visually over an area with the thin film heater under it to calculate the heat transfer coefficients accordingly.    The drop in Nusselt number and heat transfer rates with increased aeration in the working fluid is the main highlight and result. The size of the air bubbles in the channel also determine how fast the heat transfer rate drops.

An important process-design problem in multicomponent separations is separation sequencing, which is concerned with the selection of the best method and sequence for a separation system. Essentially all of the published work on this subject has been limited to high-recovery or sharp separations, in which each component to be separated appears in one and only one product stream. In industrial practice, however, it is often useful to permit components that are being separated to appear in two or more product streams. This type of separation results in products that have overlapping components and is called nonsharp or sloppy separations. The present work proposes and demonstrates a simple and practical approach to the systematic synthesis of sloppy multicomponent separation sequences. The task of synthesizing sloppy multicomponent separation sequences is inherently more complicated than that of synthesizing sharp separation sequences as identification of infeasible splits and stream splitting, and transformation of infeasible product sets into equivalent feasible product sets are examples of some difficult tasks involved. A successful synthesis strategy calls for the development of an effective and flexible framework for representing the synthesis problem and for analyzing the feasibility of component splits. In this thesis, we propose a "component assignment diagram (CAD)" for problem representation. It is shown that the use of a CAD allows the design engineer to consider many alternative solutions (or sequences) and eliminate all infeasible component splits. Further, a "separation specification table (SST)" is proposed for feasibility analysis. In particular, the use of an SST provides a means to : (i) properly define and specify key and nonkey components; (ii) quickly identify feasible and infeasible splits; (iii) effectively deal with fuel products with unmatched compo- nent specifications; and (iv) systematically consider sloppy separations with multiple split points. One difficult problem arising from the design of multicomponent distillation columns for sloppy separations is to appropriately specify the distributions of non-key components in both overhead and bottoms products. Despite the importance of these specifications, there is very little information available on this subject in the literature. This thesis reports the results from a comparative study of rigorous simulation and shortcut modeling of multicomponent distillation columns for sloppy separations. One objective was to obtain improved quantitative understanding and practical design insights into the characteristics of nonkey distributions through a shortcut modeling based upon the Fenske equation. One method proposed in this work for synthesizing sloppy multicomponent products is a heuristic method that involves a two-phase approach. The first phase is concerned with the feasibility analysis of splits pertinent to a CAD with the aid of an SST. The second phase is to specify systematically a subsequent split by applying heuristics, an activity that involves the sequential application of several "rank-ordered" heuristics. A unifying approach is proposed and demonstrated for the synthesis of sloppy multicomponent product sets. Its objective is to generate equally good initial separation schemes, featuring as many as three characteristically different sequences, including all-sharp, all-sloppy, and both sharp and sloppy (i.e., mixed separation). The proposed methods have been applied to a number of industrial separation problems. The results show that the new methods offer an extremely useful means for design engineers to generate a number of good initial sequences for obtaining sloppy multicomponent product sets prior to the ultimate separator optimization and heat integration. / Ph. D.

One of the fundamental characteristics of the microprocessor application is its property of dynamic load change. Although idle most of the time, it wakes up in nanoseconds to support sudden workload demands, which are becoming increasingly severe in today's multi-core processors with large core count. From the standpoint of its voltage regulator (VR) design, it must have very good efficiency at light loads, while also supporting a very fast transient response. Thus, the variable-frequency constant on-time current-mode (COTCM) control scheme is widely used in the VRs, as it can automatically reduce its switching frequency during light-load conditions. But, from transient point of view, it has some limitations in response to heavy-load demands by microprocessors; this is resolved by adding different nonlinear controls in state-of-the-art control schemes. These nonlinear controls are difficult to optimize for the widely variable transient conditions in processors. Another major issue for this ripple-based COTCM control is that when the combined inductor-current ripple in multiphase operation becomes zero because of the ripple-cancellation effect, COTCM loses its controllability. Therefore, the goal of this research is to discover a new adaptive COT control scheme that is concurrently very efficient at light-load conditions and also provides a fast and optimized transient response without adding any nonlinear control; hence providing a complete solution for today's high-performance microprocessors. Firstly, the overview of state-of-the-art COTCM control is discussed in detail, and its limitations are analyzed. Analysis shows that one issue plaguing the COTCM control is its slow transient response in both single and multiphase operation. In this context, two methods have been proposed to improve the transient performance of conventional COTCM control in single and multiphase operations. These two methods can effectively reduce the output capacitor count in system, but the ripple-cancellation and phase overlapping issues in multiphase operation are yet to be improved. This provides motivation to search for a new COT control technique that can resolve all these problems together. Therefore, a new concept of inverse charge constant on-time (IQCOT) control is proposed to replace the conventional ripple-based COTCM; the goals are to improve noise immunity at the ripple-cancellation point without adding any external ramp into the system, and to improve the load step-up transient performance in multiphase operation by achieving natural and linear pulse overlapping without adding any nonlinear control. Additionally, the transient performance of the proposed IQCOT has been further improved by naturally increasing or decreasing the TON time during the load step-up or step-down transient period without adding any nonlinear control. As this transient property is inherent in proposed IQCOT control, it is adaptive to the widely variable transient requirements of processors, and always produces an optimized transient response. In order to design the proposed control with high bandwidth for supporting fast transient response, an accurate high-frequency small-signal model needs to be derived. Therefore, a high-frequency model for the proposed IQCOT control is derived using the describing function method. The model is also verified by simulation and hardware results in different operating conditions. From the derived model it is found that the quality factor (Q) of one double-pole set varies with changes in duty cycle. To overcome this challenge, an auto-tuning method for Q-value control is also proposed in this dissertation. / Ph. D. / High performance microprocessors are the heart of all the fascinating computing devices in use today- ranging from the large servers in data centers to the small smartphones. To supply power to these high performance microprocessors, obviously high performance voltage regulators will be required and the expectations from these voltage regulators are increasing day by day with the complexities of the modern microprocessors. The main focus of this research work is to investigate the state-of-the-art control methodologies of today’s voltage regulators, along with the study of their limitations for future challenging requirements, and therefore, propose some effective methodologies to overcome these limitations. In this regard, a novel control method, called ‘Inverse Charge Constant On-Time (IQCOT)’ control, has been proposed in this dissertation. The concept and the features of this new proposed control scheme, along with the comparison of its benefits with the conventional control methodologies, have been presented in detail in different chapters of this dissertation.

Flow regime identification in industrial systems that rely on complex multi-phase flows is crucial for their safety, control, diagnostics, and operation. The objective of this investigation was to develop and demonstrate objective and minimally-intrusive flow regime classification methods for gas/water/paper pulp three-phase slurries, based on artificial neural network-assisted recognition of patterns in the statistical characteristics of pressure fluctuations. Experiments were performed in an instrumented three-phase bubble column featuring vertical, upward flow. The hydrodynamics of low consistency (LC) gas-liquid-fiber mixtures, over a wide range of superficial phase velocities, were investigated. Flow regimes were identified, gas holdup (void fraction) was measured, and near-wall pressure fluctuations were recorded using high-sensitivity pressure sensors. Artificial neural networks of various configurations were designed, trained and tested for the classification of flow regimes based on the recorded pressure fluctuation statistics. The feasibility of flow regime identification based on statistical properties of signals recorded by a single sensor was thereby demonstrated. The transportability of the developed method, whereby an artificial neural network trained and tested with a set of data is manipulated and used for the characterization of an unseen and different but plausibly similar data set, was also examined. An artificial neural network-based method was developed that used the power spectral characteristics of the normal pressure fluctuations as input, and its transportability between separate but in principle similar sensors was successfully demonstrated. An artificial neural network-based method was furthermore developed that enhances the transportability of the aforementioned artificial neural networks that were trained for flow pattern recognition. While a redundant system with multiple sensors is an obvious target application, such robustness of algorithms that provides transportability will also contribute to performance with a single sensor, shielding effects of calibration changes or sensor replacements.

This dissertation presents novel Harmonic Rejection (HR) Mixer architectures to obtain a high level of harmonic rejection. This is achieved by reducing the sensitivity to mismatches in devices operating at high frequencies. Consequently, the HR performance for this mixer architecture is primarily determined by resistor and capacitor matching at low intermediate frequencies (IF). Since large resistor areas can be used at relatively less power penalty in the low frequency IF section, superior HR performance is realized. A design fabricated in 110 nm CMOS process, rejects up to the fi rst 14 local oscillator (LO) harmonics and achieves 3rd, 5th and 7th HR ratios in excess of 52, 54 and 55 dB respectively, without any calibration or trimming. This mixer architecture also rejects flicker noise, has improved image rejection (IR) and second-order input-intercept-point (IIP2) performance. By using a clock N times the desired LO frequency, this scheme rejects the (N-1)th LO harmonic only by an amount of 20log(N-1) dB. A new technique is presented that enables better HR for the (N-1)th harmonic while preserving the level of rejection for other harmonics. This mixer fabricated in 55 nm standard CMOS process has a programmable number of 8, 10, 12 or 14 mixer phases and achieves an improvement of 29 dB for the (N-1)th harmonic while achieving 52 dB of rejection for the 3rd harmonic. It also rejects flicker noise and has an IIP2 performance of 68 dBm. The mixers presented in this dissertation set the state-of-the-art in HR performance for single-stage mixers with configurable number of phases without using any calibration or trimming. / text

Made available in DSpace on 2014-12-17T14:08:52Z (GMT). No. of bitstreams: 1 JulioCSN_DISSERT.pdf: 2712130 bytes, checksum: ee800f3d5f68d01d1d955c026ae1891b (MD5) Previous issue date: 2013-02-07 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / The multiphase flow occurrence in the oil and gas industry is common throughout fluid path, production, transportation and refining. The multiphase flow is defined as flow simultaneously composed of two or more phases with different properties and immiscible. An important computational tool for the design, planning and optimization production systems is multiphase flow simulation in pipelines and porous media, usually made by multiphase flow commercial simulators. The main purpose of the multiphase flow simulators is predicting pressure and temperature at any point at the production system. This work proposes the development of a multiphase flow simulator able to predict the dynamic pressure and temperature gradient in vertical, directional and horizontal wells. The prediction of pressure and temperature profiles was made by numerical integration using marching algorithm with empirical correlations and mechanistic model to predict pressure gradient. The development of this tool involved set of routines implemented through software programming Embarcadero C++ Builder? 2010 version, which allowed the creation of executable file compatible with Microsoft Windows? operating systems. The simulator validation was conduct by computational experiments and comparison the results with the PIPESIM?. In general, the developed simulator achieved excellent results compared with those obtained by PIPESIM and can be used as a tool to assist production systems development / Na ind?stria do petr?leo a ocorr?ncia de escoamento multif?sico ? comum em todo o percurso dos fluidos, durante a produ??o, transporte e refino. O escoamento multif?sico ? definido como o escoamento simult?neo composto por duas ou mais fases com propriedades diferentes e imisc?veis. Uma importante ferramenta computacional para o dimensionamento, planejamento e otimiza??o de sistemas de produ??o ? a simula??o de escoamento multif?sico em dutos e meios porosos, normalmente, feita por simuladores comerciais. O objetivo b?sico desses simuladores ? prever a press?o e temperatura em diferentes pontos do sistema de produ??o. Este trabalho prop?e o desenvolvimento de um simulador de escoamento multif?sico em po?os verticais, direcionais e horizontais, capaz de determinar o gradiente din?mico de press?o e temperatura. A determina??o dos perfis de press?o e de temperatura foi feita por meio de integra??o num?rica utilizando o algoritmo de marcha com correla??es emp?ricas e modelo mecanicista para determinar o gradiente de press?o. O desenvolvimento do simulador envolveu o conjunto de rotinas implementadas atrav?s do software de programa??o Embarcadero C++ Builder? vers?o 2010, que permitiu a cria??o de arquivo execut?vel compat?vel com os sistemas operacionais da Microsoft Windows?. A valida??o do simulador foi conduzida por experimentos computacionais e compara??o dos resultados com o simulador de uso comercial PIPESIM?. De modo geral, o simulador desenvolvido alcan?ou excelentes resultados quando comparado com os obtidos pelo PIPESIM, podendo ser utilizado como ferramenta para auxiliar no desenvolvimento de sistemas de produ??o

A system able to simultaneously separate and pump a gas-liquid mixture was developed.<p>It works efficiently and can be used in many applications (nuclear power plants,<p>pulp and paper processing, petroleum extraction, etc.). However, this pump and separator<p>system (PASS) was especially designed to handle air-oil mixture generated in<p>aero-engine lubrication systems. The PASS combines three important functions of the<p>scavenge part of the lubrication system: the deaeration and deoiling of the air-oil mixture<p>generated in the bearing and gearbox sumps and the pumping of the oil towards<p>the tank. These are critical functions for the engine. Indeed, a poor deoiling efficiency<p>leads to a high oil consumption. This reduces the flight endurance, increases the size<p>and weight of the oil tank and has a negative impact on the environment. Poor deaeration<p>and pumping characteristics lead to problems in the cooling and the lubrication of<p>the engine bearings.<p><p>Integrating a PASS into the lubrication system allows considerable improvements<p>(and simplification) to the lubrication system architecture. An important number of<p>components are suppressed: the vent lines, the deoiler, the cyclone deaerator and the<p>scavenge pumps. This reduces the size and the weight of the lubrication system and<p>increases its reliability. Furthermore, an important part of this PhD thesis focuses on<p>reducing the oil consumption in the PASS. This improves the flight endurance, reduces<p>engine maintenance and working costs and is profitable to the environment.<p><p>In addition to the development of an advanced PASS design system, the objective of<p>this thesis was to obtain a good understanding of the separation processes occurring in<p>the PASS and to develop theoretical models able to predict the separation performance<p>for every working condition encountered in a typical aircraft flight. To achieve this<p>goal, three main tasks were performed: the development of different two-phase measurement<p>systems, the experimental tests of four different PASS architectures and the<p>theoretical development (after an extensive literature review) of correlations predicting<p>the performance of the PASS in function of the working conditions. Five specific aspects<p>of the PASS were studied: the inlet flow, the deoiling efficiency, the deaeration efficiency,<p>the pumping efficiency and the pressure drop. Finally, the models that have been developed<p>with the help of the measurement systems and of the experiments have been<p>integrated in a complete model of the lubrication system (under the EcosimPro modelling<p>environment). This helps to predict real in flight PASS working conditions and<p>performance. Indeed, the PASS is very sensitive to the engine working conditions and<p>an optimisation of the prototype size and performance is only feasible with an accurate<p>knowledge of these working conditions and a complete lubrication system model.<p>Finally, with the results of this PhD thesis, a new PASS design, optimised for different<p>aero-engine lubrication systems, is presented. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

This thesis deals with the experimental and numerical analysis of the water hammer phenomenon generated by the discharge of a pressurized liquid into a pipeline kept under vacuum conditions. This flow configuration induces several multiphase phenomena such as cavitation and gas desorption that cannot be ignored in the water hammer behavior.<p><p>The motivation of this research work comes from the liquid propulsion systems used in spacecrafts, which can undergo fluid hammer effects threatening the system integrity. Fluid hammer can be particularly adverse during the priming phase, which involves the fast opening of an isolation valve to fill the system with liquid propellant. Due to the initial vacuum conditions in the pipeline system, the water hammer taking place during priming may involve multiphase phenomena, such as cavitation and desorption of a non-<p>condensable gas, which may affect the pressure surges produced in the lines. Even though this flow behavior is known, only few studies model the spacecraft hardware configuration, and a proper characterization of the two-phase flow is still missing. The creation of a reliable database and the physical understanding of the water hammer behavior in propulsion systems are mandatory to improve the physical models implemented in the numerical codes used to simulate this flow configuration.<p><p>For that purpose, an experimental facility modeling a spacecraft propulsion system has been designed, in which the physical phenomena taking place during priming are generated under controlled conditions in the laboratory using inert fluids. An extended experimental campaign was performed on the installation, aiming at analyzing the effect of various working parameters on the fluid hammer behavior, such as the initial pressure in the line, liquid saturation with the pressurant gas, liquid properties and pipe configuration. The influence of the desorbed gas during water hammer occurrence is found to have a great importance on the whole process, due to the added compressibility and lower speed of sound by an increasing amount of non-condensable gas in the liquid + gas mixture. This results in lower pressure levels and faster pressure peaks attenuation, compared to fluids without desorption. The two-phase flow was characterized by means of flow visualization of the liquid front at the location where the fluid hammer is generated. The front arrival was found to be preceded by a foamy mixture of liquid, vapor and non-condensable gas, and the pressure wave reflected at the tank may induce the liquid column separation at the bottom end. While column separation takes place, the successive pressure peaks are generated by the impact of the column back against the bottom end.<p><p>The resulting experimental database is then confronted to the predictions of the 1D numerical code EcosimPro/ESPSS used to assess the propulsion system designs. Simulations are performed with the flow configuration described before, modeling the experimental facility. The comparison of the numerical results against the experimental data shows that aspects such as speed of sound computation with a dissolved gas and friction modeling need to be improved. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished