This research aims to develop an efficient air conditioning technology that exploits cold energy storage to reduce energy consumption and CO2 emissions and shift the cooling load to off peak times to achieve better national electricity grid stability. The investigation includes the use of commonly used cold storage materials (ice, Phase Change Materials PCM) to enhance the existing air conditioning systems and using cryogenic cold storage namely, liquid nitrogen/air (LN2/Lair) to provide air conditioning for domestic and office buildings. Computational Fluid Dynamic (CFD) modelling of the main two components in the cryogenic cooling system namely, cryogenic heat exchanger and expander were also carried out. An experimental test facility was developed to validate the CFD modelling of the liquid nitrogen evaporation process and assess its potential to provide cooling. Results showed that integrating existing Air Conditioning systems with cold storage tank can lead to energy saving of up to 26% and shifting the cooling load to off peak times, but this energy saving is highly dependent on the storage medium and its storage temperature. Also, using cryogenic fluids (LN2/Lair) to provide air conditioning for domestic and office buildings can recover up to 94% of the energy stored in LAir and up to 78% of the energy stored in LN2, and based on LN2/Lair prices of 3.5 pence per kg the system showed cost saving of the energy consumption of up to 73% when LAir is used and 67% when LN2 is used compared with the conventional system. The CFD modelling of cryogenic heat exchanger showed good agreement with the experimental work with maximum deviation 7.6%.

The research relates to a study on the routing/slotting of CFRP composites of the type used in aerospace applications. Following a literature review, 3 phases of experimental work were undertaken to evaluate the effects of key process variables on the machinability of CFRP. The influence of varying operating parameters, tool material and cutting environment were initially investigated in Phase 1 work. The results showed that use of PCD was critical and highlighted the importance of chilled air in maintaining adequate tool life and acceptable workpiece integrity. Delivery of chilled air through a single-nozzle arrangement generally led to an increase in forces and delamination with the twin-nozzle configuration showing superior workpiece surface roughness. Phase 2 work detailed the effect of workpiece lay-up configuration on cutting forces, temperature and surface integrity following slotting and routing. Plies in the 45 direction generally exhibited the highest level of surface damage following machining. Experiments in Phase 3 showed that relatively small helix angles (± 3) had a negligible effect on tool life, forces and temperature. In addition, cutters with a single relief angle were found to have lower stability in operation compared to tools with a secondary clearance angle, with detrimental effects on surface roughness.

Most industrial wind turbines use gearboxes to increase the speed of rotor to the speed required by the generator. However, gearbox is among the least reliable wind turbine subsystems. In this study, the root failure cause of gearbox components retrieved from the field has been analysed and deduced to be the result of the combined effects of misalignment, coarse non-metallic inclusions, and inadequate or inconsistent lubrication, which has been verified using Finite Element Analysis (FEA) simulations. Subsequently, duplex surface systems were designed as WC/a-C:H coating deposited on surface hardened steel to mitigate or eliminate the life-limiting problems of gearboxes, which exhibited superior properties and performance than single coating systems and carburised samples. In addition to the advanced surface systems, an improved methodology of condition monitoring has been developed to avoid unpredictable gearbox failures. Four wheels made of as-received EN36 and EN40BT steel grades, carburised EN36 and nitrided EN40BT were tested against WC wheel using a rolling-sliding wear tester. The development of wheel damage was found to be closely interrelated with the AE signals. The vibration spectrum significantly changed after severe and visible damage formed on the surface of the tested wheel samples.

Impact of biofuel (2-methlyfuran, 2,5-dimethylfuran and ethanol) on the performance of a gasoline direct injection engine has been investigated. MF demonstrates better knock resistance properties and faster burning rates compared to those of gasoline. MF has much lower fuel consumptions than ethanol, produces much lower hydrocarbon (HC) and PM emissions than those of gasoline. However NOx emissions from MF are significantly higher than those of gasoline when fuel-optimized spark timings are used, which can be addressed by either retarding ignition timing or using exhaust gas recirculation. MF produce much lower aldehyde emissions compared with gasoline, methanol and ethanol. The majority of HC emissions are unburned fuel. Toluene and benzene are detected in the exhaust however their concentrations are relatively low. Under rich combustion and later injection operating conditions, soot only accounts for a small fraction (<30%) of PM. Soot produced from the combustion of DMF and ethanol is more easily oxidized than gasoline soot due to their unique capsule type oxidation mode, smaller primary and agglomerated particles. PM emissions vary significantly to fuel and injection system. Unlike gasoline, PM emissions from ethanol powered the DISI engine are not sensitive to injection system; a low injector pressure and a bad injector condition have very limited negative impacts on PM emissions.

The new biofuel candidate, 2, 5-Dimethylfuran (DMF) has received increasing interest as a potential alternative to fossil fuels, owing to the recent development of its new production technology. However, the effect of DMF properties on the fuel spray and vaporization, subsequent combustion processes and emission formation in the current Gasoline Direct Injection (GDI) engine is still not well understood. To investigate spray and combustion characteristics of DMF and explore possible applications to the IC engines, a three-dimensional Computational Fluid Dynamics (CFD) model has been developed using the KIVA3V code with improved spray models (nozzle flow model, spray atomization and secondary breakup models) and combustion models. This CFD model was validated by the optical diagnostics and then applied to study the in-cylinder mixture preparation and combustion characteristics of DMF in a GDI engine. The mixture preparation analysis shows both insufficient mixing time and significant spray-wall interaction when DMF is used result in relatively poor air/fuel distributions. Compared to the nearly homogeneous mixture with the gasoline fuel spray, a very rich fuel-air mixture of 7.7% and extremely lean mixture of 4.7% of the total charge has been observed in the case of DMF at the end of compression stoke. The analysis of combustion characteristics compared with the case of gasoline show that slightly longer combustion duration of DMF results from its lower laminar flame speed. The higher anti-knocking quality of DMF makes more advanced spark timing possible which brings about higher peak pressure and temperature and higher IMEP.

The performance of hydrostatic type slippers in axial piston pumps has been studied both experimentally and theoretically. The experimental work covers measurements of slipper clearance, slipper pocket pressure and piston spin. These measurements were taken from typical axial piston pumps running under normal operating conditions using a data logging system. The effect of operating conditions was also investigated and the resulting trends are described and discussed. In the theoretical work the behaviour of an idealised slipper was studied under steady state conditions. It was established that a flat slipper of this type does not work on a purely hydrostatic basis. Additional lift can be generated hydrodynamically if the slipper is suitably tilted; however, if the slipper is flat it cannot satisfy moment equilibrium. One mechanism which was found to satisfy load, flow as well as moment equilibrium was the presence of suitable amounts of non-flatness on the slipper loads. A parabolic type of non-flatness was simulated and the relationships between tilt, pocket pressure central clearance and minimum clearance were derived with respect to non-flatness. In conclusion, the theory is applied to the design procedure and a method is presented which enables the optimum non-flatness and minimum clearance to be estimated at particular operating conditions.

This thesis describes the analysis and design of a micro squeeze flow rheometer. The need to analyse the rheology of complex liquids occurs regularly in industry and during research. However, frequently the amount of fluid available is too small, precluding the use of conventional rheometers. Conventional rheometers also tend to have the disadvantage of being too massive, preventing them from operating effectively at high frequencies. The investigation carried out in this thesis has revealed that current microrheometry techniques also have their own disadvantages. The proposed design is a stand-alone device capable of measuring the dynamic properties of nanolitre volumes of viscoelastic fluid at frequencies up to the kHz range, an order of magnitude greater than conventional rheometers. The device uses a single piezoelectric component to both actuate and sense its own position. Thorough analytical analysis of the microrheometer has been carried out. The capillary effects, including contact angle hysteresis, and viscoelasticity associated with the liquid has been combined with the dynamics and electrical response of the rheometer itself to form a complete and consistent model. The validity of the model has been proven through fabrication and testing of the rheometer.

The a1m of this thesis was to design and evaluate implants used m the treatment of intervertebral disc disorders. A new cervical PEEK-on-PEEK disc device, combining a ball-on-socket mechanism with an elastomeric core, was designed. To find a material for the core, quasi-static compression tests were performed; on the basis of which an elastomer MED 4780 was selected for further testing. Finite element analysis (FEA) was used to investigate the maximum stresses in the device during static compression. The results showed that maximum stresses did not exceed PEEK's compressive or fatigue strength. The comparison of the mechanical properties of pedicle screws (cylindrical and dual-core), used as an integral part of the posterior lumbar stabilisation system, was performed. The screws were tested in axial pullout, quasi-static and dynamic bending, as well as subjected to the static bending, using FEA. The results of the pullout tests, performed using three polyurethane foams (0.16, 0.32 and 0.64 g/cm) showed no significant difference between pullout strength values. However, dual-core screws had significantly higher bending strength and a longer fatigue life. The FEA showed lower stress values for the dual-core screw. Furthermore, a critical assessment of explanted screws has shown that fatigue bending was the cause of failure in vivo.

The main aim of this research is to model the internal micro damage accumulated during cold deformation and the degree of reduction of damage that can be achieved by heat treatment of linepipe steel. A set of unified viscoplastic constitutive equations was developed to simulate microstructural evolution and the effect on mechanical properties due to cold deformation followed by annealing. In addition, practical experiments have been performed to validate the constitutive equations. Firstly, the industrial motivation for the project was previewed and damage-modelling techniques were reviewed to identify the research objectives. A group of interrupted uniaxial tensile tests were conducted to study the effect of different annealing times on reducing the degree of damage and improving mechanical properties of a cold formed single phase linepipe steel. From the experimental results, it was observed that healing by subsequent annealing enables a significant improvement in the mechanical properties of the deformed steel that has experienced only light damage, but has no significant effect on heavily damaged steel. Following this, a set of constitutive equations describing accumulation and annihilation of dislocations, grain size evolution, recrystallisation, plasticity induced damage and their effects on viscoplastic flow of materials was developed, for uniaxial stress conditions and by numerical integration experimental results were used to determine material constants for these equations, for the particular steel. Secondly, the constitutive equations were expanded to enable damage nucleation, growth and plastic flow to be predicted for various stress states. The constitutive equations were implemented in a commercial FE solver (ABAQUS) using the VUMAT user-subroutine. The numerical results reproduce the essential features of necking phenomena and provide a physical insight into damage evolution within a tensile testpiece under given necking conditions. Dual phase steel is of greater importance industrially, than a single phase steel, but because of the greater complexity in its microstructure, the development of microstructural constitutive equations for it is very difficult. Thus, in this work, some knowledge of damage initiation in a dual phase steel was obtained by practical investigation of microstructure. It showed that damage is due to ductile cracking characterised by the nucleation of micro-voids near the ferrite-pearlite interface. Using the mesoscopic modelling technique, by simulation, it was possible to determine likely sites for damage initiation.

This PhD project is set out to develop a high precision ceramic fabrication approach suitable for mass production, and to meet the needs of microengine application. A group of new processes have been developed and the results are characterized for fabrication of high precision ceramic oxides and composite microcomponents using soft lithography and colloidal powder processing. The materials chosen in the research are alumina, yttria stabilised zirconia and their composite for their excellent properties at high temperature.