Soot particles produced during diesel engine combustion process are of strong interest within the fields of environmental science (global warming, air pollution), air filtration and combustion science (the optimization of the combustion process). Diesel fuel production from renewable resources such as vegetable oils and animal fats offer the potential to reduce fossil carbon emissions and produce alternative ultra-clean fuels for transport and industrial use. It is well known that biodiesel, neat or in blends, can provide reduced particulate matter (PM) mass emissions through either oxygen content or enhanced air due to the higher boiling range of biodiesel. Recent observations have shown an oxidation reactivity variation with soot derived from different fuels. However, the manner in which crystallinity or nanostructure affects soot oxidation rates has not been clarified for diesel fuel soot, whether it is derived from conventional or alternative (e.g. renewable) fuel sources. This study has looked at the comparison of soot nanostructures of particulates produced from three different fuels (an ultra-low sulphur diesel fuel, its B20 blend and pure biodiesel B100) with a diesel engine by means of high resolution transmission electron microscopy (TEM) imaging. TEM studies of soot samples collected on a soot catcher under conditions relevant to different biodiesel blends, revealed a nanostructure that to our knowledge, has not been previously reported for diesel soot particulates. The immersion corrosion tests of biodiesel B100 were conducted at six different temperatures; 25°C, 80°C, 90°C, 100°C, 110°C and 120°C, each for 270 hours. Each sample was weighed at the commencement of the tests and again at the end. Any difference in those weights was used to inform on the corrosion characteristics of the particular fuel on each metal type. Under the experimental conditions, copper and brass were more susceptible to corrosion in biodiesel than aluminium and steel.

Mixed convection heat transfer in enclosures has been studied in order to enhance the associated heat transfer performance through the use of either different convective fluid types, domain configurations, boundary conditions, or combinations thereof. Analysing the enhancement in heat transfer has been accomplished through the isotherm and streamline contours, temperature isosurfaces, flow vectors, mean and root mean square velocity profiles, turbulence kinetic energy profiles and Nusselt number profiles. Firstly, laminar mixed convection in a lid-driven trapezoidal cavity using different nanoparticle types and various parameters other than configuration parameters has been investigated. It was found that any nanofluid types can provide greater heat transfer than water, especially, at high nanoparticle volume fraction and low diameter. Heat convection can be affected by changing either rotational and inclination angles, aspect ratio, or flow direction. Secondly, turbulent mixed convection due to the moving sidewalls of a lid-driven cuboid has been analysed. Remarkable enhancement in heat transfer has been achieved by either increasing the turbulent flow circulation or using nanofluids. Thirdly, turbulent mixed convection in a top wall lid-driven cuboid containing a clockwise- or anticlockwise-rotating cylinder has been studied. Significant enhancement in heat convection was noticed with the use of the rotating cylinder, especially when the direction of rotation can enhance the top wall movement. In addition, the Reynolds number and nanofluids have a positive impact on the heat transfer in the presence of the rotating cylinder. Finally, the study has been extended by artificially roughening the heated wall in order to increase the heat transfer rate. A noteworthy enhancement has been found due to the use of two rib shapes, particularly in combination with the rotating cylinder. Overall, in terms of the comparison between the URANS and LES predictions, even though both methods have performed well, the LES approach is more successful in capturing more detail of the secondary eddies.

Wireless Sensor Networks (WSNs) consist of a number of spatially distributed autonomous sensor nodes that are configured to gather physical or environmental information in an area. A sensor node can be subject to many constraints including limited power, low processing and sensing capabilities, small memory, small bandwidth, and low communication range. In WSNs, when an event occurs, a sudden burst of network traffic will be generated which may lead to congestion and hence to lost or delayed data packets, decreased reliability, and increased power consumption. One approach that controls the congestion in WSNs is the resource control method, in which congested nodes are avoided by sending the packets through alternative paths. To test the existing methods of congestion control e.g. the Hierarchical Tree Alternative Path (HTAP) algorithm and to develop a new method, an experimental facility consisting of 40 nodes (Waspmotes) was deployed. In order to accurately measure end to end delay and to ensure nodes wake up at the same time, the node clocks were synchronized to an accuracy of approximately 40μsec between nodes and to 5ms between nodes and external time, using a method applied experimentally for the first time. The experiments demonstrated that HTAP has better performance (Packet Delivery Ratio - PDR, throughput, and End to End delay) than a network without congestion control. However, in some network topologies where alternative paths do not exist, in the event of congestion, the network performance will be degraded. Therefore, traffic control, which reduces the packet rate, has also been employed to mitigate congestion. The location of the single path affects the network performance with poorer performance when it is close to the sink than to the source. Based on the results, using both resource control and traffic control leads to the best network performance.

Laminated composite materials are used in different applications, for example mechanical, civil and aerospace structures, due to their light weight and excellent mechanical properties. However, fibre breakage and delamination are among the more serious damage that often initiate and propagate due to a number of mechanical and, specifically, dynamic loads during the operational life. Also, these damages destroy design functionality of these structures. To address this issue, damage detection is required in time to provide a good understanding of structure state in advance of any potential failure. There are a number of damage detection approaches reported in the literature and reviewed herein. Some of these are base-line free, whilst others use the intact data as a reference for the detection of damaged sections. However, currently there are a very limited number of experimental studies in the literature that use vibration-based damage detection to detect the delaminated areas, and are almost non-existent for fibre breakage; the majority of simulated studies consider delamination only. Defects in laminated structures are quite complicated and in most cases are hidden. Frequency-based damage detection is considered to be a global approach and is not useful when dealing with complex structures. There has been extensive research to develop the curvature mode shape as a reference for damage detection because it is highly sensitive at show the effects of damage. This sensitivity is tested in this research, as it is extremely difficult to detect damaged sections within composite materials, even with an active approach. Hence, the main objective of this research is to develop the curvature damage index by calculating the irregularity curvature index, and the proposal of a novel index, called the Haar index, to support the damage detection process. Both these indexes are used to detect delamination and fibre breakage on high modulus CFRP plate structures under condition of free vibration. Using these indexes gives an efficient method by which to quantify and localize damaged areas in both theoretical and experimental considerations of different lay-ups. In the modelling section, two finite element software programs, COMSOL Multiphysics 5.1 (Licence No. 7074366) and ABAQUS 6.14-1 (Licence No. 200000000008515), are used. This thesis includes development procedure of the curvature index, calculates the Haar index, gives details of the theoretical and experimental analysis, and reports the consequent results and discussion.

Numerical studies, calibrated and validated using experiments, were carried out to develop a constitutive law for powder compaction. In order to simulate powder compaction at particle level, single particle compression/breakage test is used to characterise the mechanical properties, which include elastic modulus, Poisson’s ratio and yield strength. Finite Element Analysis (FEA) of single particle compression was carried out and validated vs. single particle compression testing and then used to establish a suitable hardening law. The particle size, shape and packing arrangement were obtained using X-ray computed tomography. This information was transferred to FEA. Due to the presence of complex geometrical structures, Meshlab and Solidworks were chosen to deal with the arrangement of particles in the structure. The multi-particle finite element method (MPFEM) was implemented into the finite element software package Abaqus/EXPLCIT v6.14 and used to simulate the powder compaction process. The model input parameters include mechanical properties (of the single particle) and interactions between particles (e.g. friction). The stress-strain curves predicted by MPFEM were validated experimentally using compaction tests performed in a die instrumented with radial stress sensors. The method proposed was used for constitutive model development for powder compaction as an alternative to bulk powder characterisation. The stress-strain curves MPFEM were analysed using the deformation plasticity framework. Contours of constant complementary work in Kirchhoff stress space were established and a model consistent with the behaviour of the materials was identified in order to capture the materials response under conditions experienced in practical die compaction processes.

A numerical study is performed into the effects of the location of exhaust diffusers in relation to the room heat sources on thermal comfort and energy saving. A new concept of the combination of indoor heat sources and the exhaust outlet was also employed in this investigation. The results showed that the indoor thermal environment and energy saving were greatly improved by combining the exhaust outlets with some of the room’s heat sources. For further improvement, this concept was also used along with a novel local exhaust ventilation system in the modelled office room. This system was adopted and developed for use in office spaces, where the exhaust opening was combined with the office workstation into a single unit. The main aim was to help extract the warmed and contaminated air locally before it could disperse across the room. Three different amounts of recirculated air and three different heights of the combined system were analysed. The results showed a significant improvement in energy savings and inhaled air quality in the room using the new ventilation system. It was also found that the performance of this system was greatly influenced by the height factor. In addition, in this research, the LES method was employed to investigate the complex characteristics of airflow and temperature distribution in the office room which used the concept of combining the exhaust outlet with room heat sources. The results revealed that the airflow and temperature distribution were highly unsteady and unstable, particularly in the regions where buoyancy works effectively to cause a high number of perturbations. The developed CFD models were thoroughly validated.

Micro-grid systems are small-scale power supply networks that are designed to provide electricity to a local community from local generators. Micro-grids operate with a common AC or DC bus, and power converters are key components for interfacing the generators and storage devices (and sometimes the loads) to the common bus. The aim of this research study is to investigate and develop high-efficiency power electronic converters for the interconnection of fuel cells and ultra-capacitors to a DC micro-grid for stationary power distribution systems. The converter for the fuel cell and its dynamic control have been designed, simulated, and further improved by introducing a new modified active clamp circuit that enhances performance and increases the efficiency of the converter. This new modification has been designed and verified by PSpice/Simulink approach and implemented using dSPACE. To control the power flow status of the ultra-capacitor, a bidirectional DC–DC converter is required. A number of different alternative DC–DC converter topologies were compared. It was concluded that, the bidirectional voltage–fed topology is better suited for dealing with the fast dynamic response of the ultra-capacitor. However, this topology exhibits a higher circulating power flow and higher conduction losses. Based on this limitation, a modulation scheme that minimises the circulating power flow in the converter was introduced and this was verified by simulations. The hardware for the ultra-capacitor (bi-directional) converter has also been designed and implemented. The test results demonstrate the ability of the converter for fast and bidirectional power flow. The development of simulation models and the control system are experimentally implemented in dSPACE.

Few physical phenomena can be adequately described without reference to their histories. This maxim applies not only to the field of experimental engineering but throughout academic disciplines to geography, biology, human relations and almost every sphere of physical activity. With reference to the field of fluid dynamics the interpretation of this statement means that few real flow situations can be described solely in terms of local values and relationships and that the previous history of the flow must be taken into account. An example of this is the work of Cockrell , Diamond and Jones ( 1 ) *, who showed that for a given diffuser , the performance varied even though the inlet boundary layer thickness parameters were maintained constant , and inferred that the manner in which the boundary layers had been produced has an appreciable effect on diffuser performance. This thesis has three major objectives. The first is to use our knowledge of flow history to provide an explanation of the 'overshoot' phenomenon experienced by the growth of the boundary layer thickness parameters in duct flow. This manifests itself by the manner in which a thickness parameter grows until it reaches a stationary point, whereupon it subsequently decreases. The second objective is to attempt to expand our knowledge of flow history effects by simulating a mean velocity profile at the duct entry and observing the subsequent development in both this and the turbulence parameters of the flow. This second objective has practical applications in the production of atmospheric boundary layers and other shear flows for the purpose of model Figures in brackets refer to reference listing. testing. The third objective is to use the experimental results obtained from duct flow in the auxiliary equation of an integral method of boundary layer calculation. This then should provide a realistic allowance for the flow history effects. Since the lack of any allowance of flow history effects is very often a major failing of the use of integral techniques it is possible in this instance to attempt to assess the overall usefulness of such a method. In addition to these major objectives, appendices are presented on the experimental behaviour of the local relationships, often used in calculation methods, between the turbulent shear stresses and the mean velocity profile. The distributions of these mixing lengths and eddy viscosities are compared with some of the formulations available in the literature. A description of the experimental facilities is given which includes a section on the use of hot wire anemometers for the measurement of turbulence. Some of the likely sources of error encountered here, together with their possible magnitudes, are also presented.

The established identification techniques of Astrom and Bohlin and Box and Jenkins are designed to estimate the parameters of both process and disturbance models from input/output records. The methods require open-loop experimentation on the process with a perturbation on the input from an external source. The resulting output fluctuations are often unacceptable for normal production. especially if the output exhibits drift. It is more desirable to attempt to identify and control simultaneously, avoiding the need for a prior experimental identification mode. This thesis presents some techniques of simultaneous identification and control for single-input, single-output, linear dynamic systems. The methods, based on the Box and Jenkins control scheme, are simple to apply and require a relatively small amount of computation. A particularly valuable technique exploits a separation effect for processes with large time-delays. This method of simultaneous identification and control is applied to an industrial chemical process and provides sufficient information to allow for the design of a control system which substantially reduces the output variations. Other techniques, presented in this thesis, which are not restricted by the magnitude of the process time-delay are not as yet generally applicable to industrial process-control problems.

In considering the experimental evidence for non-Newtonian behaviour, which has often been interpreted in terms of viscoelasticity, deviations from established theories, which assume a Newtonian fluid with viscosity dependent upon temperature and pressure, are sought. It is, therefore, vital to isolate inherent non-Newtonian behaviour from deviations arising from other unrelated processes. Non-Newtonian behaviour which has been detected is of two main types: inlet region effects (which may also arise from incomplete filling) and Hertzian zone effects (which may be attributed, at least in part, to the consequences of viscous heating). The thesis therefore presents a new theoretical analysis of the temperature distribution in the Hertzian zone and an analytical treatment of the effect of inlet starvation upon film thickness in order to aid the recognition of inherent non- Newtonian behaviour in the analysis of experiments. Experiments with markedly non-Newtonian lubricants (a series of silicones of differing chemical structure) are reported and an attempt is made to relate their hydrodynamic performance and degree of non-Newtonian behaviour to their molecular geometry. A four disc machine, employing a low elastic modulus (perspex) central specimen has been developed to examine non-Newtonian behaviour under conditions which reproduce the kinematics of low conformity contacts but which eliminate the influences of pressure and temperature whose unavoidable presence poses the major problem in the interpretation of experiments with conjunctions between metallic specimens. Excellent agreement is found between the experimental results and published non-Newtonian behaviour obtain from oscillatory shear measurements.