This thesis presents the development of a novel hybrid pneumatic-electric actuator which combines the advantages of both pneumatic and electrical actuator. The hybrid actuator consists of a pneumatic cylinder and a DC motor. They are connected in parallel using gears. The components are sized to provide the torque required to rotate a single-link robot arm vertically upwards. On/off solenoid valves are used rather than servo valves to keep the hardware cost low. A mathematical model of the nonlinear actuator dynamics is derived using a combination of physical laws and empirical curve fitting. The dynamics of the mechanical, electrical and pneumatic elements are included. Then a novel discrete-valued model-predictive control plus integral compensator algorithm is created for controlling the position of the pneumatic cylinder using the on/off valves. The control algorithm for the hybrid actuator is completed by using a conventional PD algorithm to control the electric motor. Experiments shows the hybrid actuator outperform pneumatic actuator in every aspect. Conversely, the DC motor added a faster acting and finer quantized force to the pneumatic cylinder force, which greatly improved the dynamic position control performance of the hybrid actuator. In experiments, the mean root-mean-square error and the maximum absolute error improved by 84% and 77%, respectively. / Master of Science in Mechanical Engineering (MSME)

<p> The objective of the present research was to investigate the effects of rotating circular cylinders to control high intensity wind load. This research used computational fluid dynamics (CFD) to simulate high Reynolds number gust-like wind load condition for a transient duration of 12 seconds across a three-dimensional rectangular cylinder with dimension of 240x15x7 meters and aspect ratio (Breadth/Height) of 2.3. An array of 20 circular cylinders was positioned along the leading edges of the rectangular bridge cylinder. The research analyzed turbulent flow characteristics across the top and bottom deck surfaces and the development of wake region during two cases: 1) stationary cylinders and 2) rotated cylinders at 400 RPM or velocity ratio of &lambda; = 1.33. The Strouhal number flow characteristics of 0.08 and 0.17 for aspect ratio of 2 to 3 analyzed in this study were found to be in agreements with published literature.</p>

<p> The thesis aims to create a proof of concept an open source student supported block diagram software, BlocSim. BlocSim demonstrates real time microcontroller-in-the-loop capabilities and block diagram simulation. The BlocSim has a drag and drop interface for ease of use. BlocSim creates journal quality block diagram images and the accompanying latex formatted code. BlocSim stores data in an xml format for future use.</p>

<p> The main focus of this dissertation was the experimental and numerical investigations of laminar flames of heavy liquid and solid hydrocarbons under simple (one-dimensional, steady state flow field using canonical configuration) and complex (two/three-dimensional, transient flow at high Karlovitz number) flow conditions.</p><p> A number of theories that have developed based on simplified assumptions and asymptotic analysis and more important for light fuels such as methane, were examined both experimentally and numerically in two steady state and canonical configuration, namely counter-flow configuration and Bunsen flame configuration. The counter-flow configuration was used to determine laminar flame speeds and extinction strain rates over a wide range of heavy hydrocarbons including normal alkanes (up to carbon number 16), practical gasolines and jet fuels and aromatics (cyclopentadiene). The analytical solution derived from asymptotic analysis provides good agreement for laminar flame speeds for fuel lean conditions. However notable discrepancies have been identified for fuel rich conditions due to lack of consideration of fuel-oxygen differential diffusion especially for heavy fuels for which the molecular weight disparity between oxygen and fuel is large.</p><p> For the Bunsen flame configuration, the area and angle methods were examined to measure laminar flame speeds of methane/air flames (representative of light fuel) and propane/air flames given that propane is the lightest hydrocarbon with distinctly higher molecular weight than oxygen. The results indicated that apart from issues raised from inlet boundary condition, flame extinction induced complex flow distribution at burner edge and flame tip effect, such configuration can&rsquo;t produce quantitative results for fuels heavier than methane due to lack of consideration of flame speed variation to stretch for fuel/air mixtures with non-unity Lewis number.</p><p> Based on the understanding of the propagation of flames of heavy fuels, accurate measurements of laminar flame speeds were carried out using the counter-flow configuration at atmospheric pressure for a variety of complex fuel molecules for which data are non-existing and which are of direct relevance to practical fuels.</p><p> The interaction between a flame and turbulence is a fundamental aspect of combustion. To further illustrate the difference of flame behaviors between light and heavy fuels, the vortex laminar flame interaction was studied numerically in a canonical two-dimensional configuration for methane and <i>n</i>-dodecane flames. The <i>n</i>-dodecane exhibits early decomposition prior entering the flame due to the local temperature rise caused by the vortex, and such phenomenon is not observed in methane/air flames.</p><p> In summary, the main conclusion of this dissertation is that the fuel complexity that has been frequently ignored in flame research needs to be accounted for in simple and complex flows. It was shown that the fuel effects are both of physical and chemical nature.</p>

The flow entering a high-pressure turbine in a gas turbine engine is characterised by a loss of symmetry due to temperature distortions in both radial and circumferential directions, known as hot streaks. In industrial simulations it is common practice to assume uniform inlet temperature conditions to simplify the aerodynamic analysis. However, hot streaks may have significant impact on the turbine aerodynamics with the redistribution of the hot fluid affecting the development of secondary flows with consequent effects on enhanced local heat transfer and aerodynamic losses. The loss of symmetry has also been linked to the excitation of low-order nodal diameter assembly modes of the downstream rotor blades leading to potential blade failure and thus, should be taken into account during the design process. In today’s carbon-constraint environment additional parameters arise as gas turbines are challenged to adapt to variations of the fuel composition driven by the need of efficient and lowCO2 power generation. Introducing syngas, a synthesis gas fuel that is used to power integrated gasification combined cycle (IGCC) power plants, is likely to affect the operating conditions of existing gas turbines leading to the requirement of re-design of components. With particular focus on the turbine hot flow path, the propagation mechanism of hot streaks throughout the turbine will be affected with consequent impact on the turbine aerodynamics and forced response excitation levels originating from the different hot flow patterns. Motivated by the lack of relevant studies, the current work provides a first step towards the evaluation of the effects of syngas on hot streaks aerodynamics and the induced forced response excitation levels. Using full annulus multi-bladerow unsteady 3D CFD simulations and applying combustor representative hot streak profiles in two different gas turbines, a complete analysis of the hot streaks migration is achieved, with respect to a number of geometric parameters such as the hot streaks shape and injection location in both spanwise and circumferential directions, the coolant configurations as well as the combined effects on the secondary flow development. The aerodynamic analysis indicated the propagation of the hot streaks up to the exit of the turbines under investigation with differences in characteristics depending on design parameters. With respect to the effect of fuel composition variations on the blades temperature levels and the flow pattern is observed between the natural gas and syngas turbine with the syngas showing a more concentrated wake shape. In effect of the syngas different flow pattern, differences are observed in the secondary flows with consequent interaction with the hot streaks. Contrast to initial expectations, the forced response analysis iii resulted slightly lower amplitude unsteady force of lower harmonics for syngas compared to natural gas; however, both fuels showed significant levels of the hot streak induced low engine order excitation compared to the burners and stator related blade passing frequency vibration.

Over recent years, with growing concern over climate change, the need for energy which is sustainable, economical and in line with legalisation has led to a substantial surge of interest in organic Rankine cycles (ORC). With the ability to convert low temperature heat sources into power, ORC technology is at the forefront of many sustainable technologies such as biomass, solar, geothermal and waste heat recovery. Despite successful commercialisation for large-scale systems (> 200 kWe), more development is required at the small-scale to realise its potential. For low temperature (< 150 °C), low power applications, volumetric expanders are the preferred choice. However, for a 10 kWe system, a well-designed radial inflow turbine could achieve a higher efficiency, and bridge an observed gap between the output powers of existing volumetric expander systems. This thesis investigates the design and analysis of radial inflow turbines for this application. A thermodynamic ORC model is first developed, which combines cycle analysis with component design. This model is coupled with a multi-objective optimisation, and a novel objective function is developed that considers the trade-off between system performance and system complexity. Following a cycle analysis case study, a radial inflow turbine design method for ORC turbines is developed which extends existing ideal gas design methods to be applicable for real gases. Two candidate turbine designs are developed and are validated using computational fluid dynamics (CFD). For small-scale systems to be economically feasible it is reasonable to assume that the same turbine will be implemented within a number of different systems. This requires off-design models, and the suitability of using non-dimensional performance maps, obtained using similitude theory, has been investigated using further CFD studies. This has led to the development of a modified similitude theory, suitable for subsonic ORC turbines. This modified similitude theory has been implemented within another thermodynamic model, and the results from a case study show how the same turbine can be effectively utilised within a number of different ORC systems. This is done by selecting a working fluid to match the available heat source. Overall, this thesis successfully demonstrates the development of modelling methods for small-scale low temperature ORCs utilising radial inflow turbines. This has considered design and off-design performance models, and ultimately the results demonstrate how the economy of scale of these systems can be improved, aiding in the future commercialisation of the technology.

The construction industry has been challenged by the UK Construction Foresight Panel to apply advanced information and communication technology to improve the performance, in terms of sustainability, of the existing built environment and infrastructure. Traditionally, built-environment maintenance is a capital-cost-driven activity that relies either upon the subjective assessment of a built environment and infrastructure condition (i.e. a stock condition survey) to identify maintenance needs, or upon a reactive response to a component failure. The effectiveness and efficiency of the stock condition survey process to support planned maintenance has previously been questioned and a more sustainable approach, based on an objective assessment of a built environment and infrastructure performance, has been suggested. Previous attempts to develop objective-based (though not performance–based) maintenance models have largely failed, due to the limitations of technology, the daunting task of managing large amounts of data, and the inability of mathematically based models to cope with the complexity of real-life situations. This thesis addresses this challenge by exploring the feasibility of a performance-based assessment methodology to determine the maintenance needs of a buried oil steel-pipeline system and the impact that any changes in condition may have on the performance and integrity of related components in the pipeline system. The thesis also contains an evaluation of the ability and effectiveness of piezoelectric elements in pipeline defect (crack) signature detection to predict changes in component performance with data sets derived experimentally using laboratory bench testing. Vibration sound-emission detection techniques performed on various oil steel-pipeline defects, using non-destructive testing methods, were validated using attenuation and waveform analysis. Defect size and progression (i.e. the pattern characteristics of the defect) were monitored, measured and identified through spectrum analysis of multiple emission signals in combination with a number of frequency bands. Two series of tests were undertaken to evaluate the ability of vibration sound emission characteristics to identify steel pipeline defects, including leakage. Test Series 1 established the frequency (waveforms) of the generation of the acoustic emission signal caused by normal fluid dynamics (water flow) through the experimental steel pipe and the resulting signal propagation characteristics. Test Series 2 detected and monitored changes in the signal characteristics for incipient defects: (a) small-nail damage, (b) medium-sized nail damage, (c) large-nail damage and (d) crack to leakage source [sealed holes as a simulated corrosion to total failure]; oil was the fluid medium. The defect sources and leakage signals were also studied, and compared with theoretical models. The results of the theoretical analysis and the laboratory experiments confirmed the ability of non-destructive testing, based on vibration sound emission techniques, to detect and distinguish between different failure modes. The ability to carry out a basic inspection, analysis and report of a pipeline using an integrated-sensor device offers many potential benefits. The use of an integrated-sensor device is expected to provide valuable pipeline management information. Specifically the ability to detect and locate mechanical damage at the incipient stage and provide an assessment of the overall pipeline operating condition, including changes in performance profile and prediction of an estimated time to failure, has been shown to be feasible as part of a pipeline maintenance and rehabilitation programme.

<p> This thesis focuses upon using a high-order finite-difference method on a structured overset grid to study flow features around a generic simplified car model adjusting mesh refinements, rear slant angles, solvers, and turbulence models. These processes are explored to develop a procedure for simulating more complex and realistic car models. Three different mesh refinements from 17 to 108 million vertices were tested with three different solvers (RANS, URANS, and DES) on an Ahmed body with a subcritical slant angle ascertain the optimum mesh parameters for subsequent simulations. Using a 57 x 10⁶ vertex mesh, multiple rear slant angles near the critical angle (30 degrees) were investigated with RANS and URANS approaches to compare drag, lift, and flow fields with experimental and CFD data found in literature. Similar trends were observed in CFD predictions and experimental data, including flow separation at the critical angle (30 degrees), but all predicted results were within 15% of experimental measurements for both time-averaged and unsteady simulations. At the sub-critical angle (25 degrees), CFD predictions using multiple hybrid RANS/LES approaches were compared against time-averaged and unsteady experimental measurements. These did not disagree with previous results and drag values were over predicted by a maximum of 4%, while lift values were under predicted by a maximum of 15% when compared to experimental results. Subsequent studies investigating elongated mesh refinement areas were inconclusive. The procedures outlined compare reasonably well to experimental data and can be used as a starting point for simulating more realistic models including complex dynamic pitch, heave, and roll simulations involving road vehicles.</p>

<p> According to Wohlers Report 2014, the worldwide 3D printing industry is now expected to grow from $3.07B in revenue in 2013 to $12.8B by 2018, and exceed $21B in worldwide revenue by 2020. With 3D printing rapidly evolving from a prototype commodity to a means to produce full production items, lattice structures are becoming of great interest due to their superior structural characteristics and lightweight nature. Within design, lattice structures have typically been defined by preset beam configurations within a cube. Certain configurations have been proven analytically to be optimal for certain load functions, but never has there been optimization performed to discover or verify the optimal lattice shapes and sizes within a predefined cubic space. By performing optimization on these cubic cells, a design guideline can be created for designers of lattice structures. In this thesis, several lattice configurations are analyzed both from a micro level (single unit cell) as well as a macro level (a simple series of unit cells). Optimization is performed with respect to stiffness and compliance to identify strategic configurations for bending, torsion, compression and tension. Only cubic base cells are analyzed (i.e. no hexagonal). Knowing optimal lattice configurations from a structural standpoint enables designers to further reduce weight and increase structural efficiencies when designing for additive manufacturing. The results of this study yield a well-defined guideline for design engineers to utilize when lattice structures are incorporated in a structural design. With this design guideline information available to design engineers, further utilization of lattice structures can be exploited by efficiently applying strategic unit cell configurations to the overall design.</p>

<p> In first part of the thesis a detailed study of the particulate pollutant distribution by wind flow over a building in an urban area was performed. The accuracy of RANS-RSTM and LES turbulence models for predicted airflow over a square cylinder was first evaluated. These models are then applied for simulating wind flows over the scale-model of the Center of Excellence (CoE) Building. Comparing the simulation results with the experimental data of Kehs et al. (2009) showed that the RSTM predicted the pressure distribution on the building consistent with the measurements, but it could not capture the details of the airflow velocity field around the building. The LES simulation, however, showed good agreement with the PIV data. The LES model was then used for analyzing the particulate pollutants transport and deposition analysis. </p><p> Particle motion was modeled using a one-way coupling, Lagrangian approach. Particular attentions were given to the effect of the turbulent velocity fluctuations on particles dispersion and deposition. Instantaneous turbulent velocity fluctuations were simulated using the Langevin stochastic differential equation. The particle transport model in turbulent flows was validated by comparing the predicted deposition velocity for vertical and horizontal channel flows with the existing experimental data and numerical simulation results. Finally the particulate pollutant dispersion and deposition around the scaled CoE Building were investigated using the LES and unsteady particle tracking approach. </p><p> In addition, the size-concentration distribution of secondary organic aerosols (SOAs), as an indoor air aldehyde pollutant, was numerically modeled. The population balance equation of the SOAs was solved using the method of moments (MOM). To close the model, particle size distribution was assumed to follow a lognormal distribution, which was based on the experimental data of Chen and Hopke (2009). The nucleation of SOAs from the chemical reaction of &agr;-pinene (a common emission from indoor furniture), and ozone in the air, as well as, their Brownian coagulation and the surface growth were considered in the numerical model. The computational model was evaluated by comparison with the experimental data of Chen and Hopke (2009). </p><p> The MOM was used for modeling the distribution of the SOAs in an office space. The concentrations of SOAs in the breathing zone of an occupant in the room were evaluated for two mixed-mode ventilation systems. The simulation results showed that the pollution concentration in the ventilation system with the air outlet placed in the ceiling was smaller than the one in which the air outlet was in the floor behind the manikin model.</p>