http://bura.brunel.ac.uk/handle/2438/8626 2026-04-07T18:39:36Z 2026-04-07T18:39:36Z Uka, Jetmira http://bura.brunel.ac.uk/handle/2438/32734 2026-01-27T10:46:49Z 2024-01-01T00:00:00Z

Title: Producing a novel alumina reinforced aluminium matrix composite from aluminium machining waste Authors: Uka, Jetmira Abstract: This study explores an innovative approach to producing alumina-reinforced aluminium matrix composites (AMCs) directly utilising aluminium alloy machining waste as the primary raw material. By leveraging the machining waste, this research addresses material sustainability and aligns with circular economy principles, minimising resource wastage and promoting environmental sustainability. The focus is on enhancing the naturally occurring alumina on the swarf surface through specific treatments to improve the composite's overall properties. The research methodology employs a multi-technique analysis to monitor and adjust the processing conditions, ensuring optimal material characteristics. Initially, the aluminium swarf is subjected to high-temperature treatment, followed by Equal Channel Angular Pressing (ECAP) to consolidate the material into a dense, uniform composite. X-ray diffraction (XRD) analysis identifies the phase composition, revealing the transformation of alumina polymorphs under different thermal conditions. Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS) maps the elemental and phase distribution, assessing the interaction between alumina reinforcement and the aluminium matrix. Polarised light observation and Electron Backscatter Diffraction (EBSD) are utilised to evaluate grain refinement, microstructure, and texture, providing insights into the composite's mechanical behaviour. Key findings indicate that heat treating the aluminium swarf at 650 °C for 2 hours results in the formation of gamma alumina only on the surface. Increasing the temperature to 850 °C transitions the alumina to the alpha phase, known for its superior mechanical properties. Four passes of ECAP using route C effectively consolidate the treated swarf into a composite with no visible macro-porosity, although microporosity around the alumina particulates is still observed. This suggests that while 4 passes, ECAP successfully breaks alumina films and welds adjacent swarfs, this number of passes fails to remove microporosity that could influence the composite's mechanical properties. The composite's performance is further evaluated through tensile and hardness tests, confirming the significant impact of processing conditions on the material's mechanical behaviour. The presence of alpha alumina, achieved through precise heat treatment and the composite's consolidation via ECAP, contributes to enhanced tensile strength and hardness compared to composites with gamma alumina or those processed under less rigorous conditions. This research contributes to the field of materials science by providing a novel method for repurposing aluminium machining waste into high-value composite materials. By optimising the processing conditions, particularly the heat treatment temperature and the application of ECAP, it is possible to produce AMCs with improved mechanical properties suitable for various high-performance applications. Moreover, this study highlights the potential of using advanced material characterisation techniques to understand the microstructural evolution of composites, guiding the development of more sustainable and efficient manufacturing processes. In conclusion, this study presents a sustainable approach to manufacturing alumina-reinforced AMCs using aluminium machining waste enhanced by high-temperature treatment and ECAP. The findings underscore the importance of processing conditions in determining the composite's microstructure and mechanical properties, offering insights into developing new materials contributing to the circular economy. Future research could explore the long-term performance of these composites in real-world applications and further refine processing techniques to minimise microporosity and enhance material properties. Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London

2024-01-01T00:00:00Z Alkhrainig, Adel http://bura.brunel.ac.uk/handle/2438/32324 2025-11-11T03:01:02Z 2025-01-01T00:00:00Z

Title: Food waste management and the possibility of conversion of waste to electrical energy in Kuwait Authors: Alkhrainig, Adel Abstract: Food waste management poses a significant environmental challenge in Kuwait, where over 90% of food waste is disposed of in landfills, leading to greenhouse gas emissions, leachate contamination, and inefficient land use. This study investigates anaerobic digestion as a sustainable waste-to-energy strategy, focusing on the influence of inoculum source, substrate composition, and hydrogen addition on biogas production and methane yield. The primary objective is to evaluate how different inoculum types and process enhancements impact methane generation from mono- and co-digestion of locally abundant food waste materials, including date fruit, meat, rice, and Sidr fruit. Anaerobic digestion experiments were conducted using two inoculum sources: wastewater-derived and food waste-derived. When digesting date fruit alone, wastewater inoculum produced 594 litres of biogas per kilogram of volatile solids with 59% methane, compared to 562 litres and 50% methane using food waste inoculum. Co-digestion of date fruit with rice and meat achieved the highest methane yield of 661 litres per kilogram of volatile solids at 66% methane concentration, attributed to enhanced microbial synergy and nutrient balance. In comparison, Sidr fruit codigestion yielded 519 litres per kilogram with 67% methane, demonstrating high methane quality but a lower volumetric yield. This research is also the first to assess hydrogen injection in the anaerobic digestion of date fruit. Hydrogen addition at 0.67 millilitres per minute significantly increased methane production from 283 to 628 litres per kilogram of volatile solids, with methane concentration rising from 50.5% to 60%, highlighting the role of hydrogenotrophic methanogens. Overall, the findings demonstrate that inoculum type, substrate synergy, and hydrogen enrichment are critical parameters in optimising biogas output. This study contributes new insights into anaerobic digestion process design and offers a scalable framework for sustainable energy generation from food waste in Kuwait. Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London

2025-01-01T00:00:00Z Garner, Robert http://bura.brunel.ac.uk/handle/2438/32204 2025-10-22T11:05:40Z 2025-01-01T00:00:00Z

Title: Modelling and design optimisation of renewable energy communities to support the energy transition aspirations of rural and islanded populations Authors: Garner, Robert Abstract: The market for distributed Renewable Energy Systems has increased considerably in recent decades, driven by the necessity for a reduction in global carbon emissions in an effort to combat climate change. While the focus on decarbonising the energy sector in Europe has been successful in recent years, it has disproportionately benefited urban population centres. Those who live in built-up environments will likely have better access to newer, greener technology, with islanded communities often relying on a weaker grid with fossil fuel reliant infrastructure. These communities are therefore at high risk of being left behind in the energy transition towards net-zero emissions. This study presents a novel solution to the problem of decarbonising remote, islanded populations by means of Renewable Energy Communities (RECs). The test location, Formentera, was chosen due to its unique set of challenges and opportunities regarding energy security and access to clean energy. A generalised, modular model was developed in Python, allowing the integration of generation (wind and solar), storage (battery and hydrogen), and real-world data from the test location. The model simulates the dynamic dispatch of the system over hourly increments to evaluate the annual performance. The system is optimised using the Non-dominated Sorting Genetic Algorithm (NSGA-II), which identified an inherent trade-off relationship between cost reduction and decarbonisation of the REC. Results show that the deployment in the case study location can deliver improvements in both cost and emissions relative to a grid-only scenario. A comparison of storage configurations shows a considerable benefit to co-locating batteries and a regenerative hydrogen storage system due to the latter’s ability to act as a seasonal storage buffer. Findings suggest that a ’friendly’ local trading policy outperforms a market-based regime on cost savings, and ensures better energy equity between members. The analysis incorporates Monte Carlo simulations of estimated assumption ranges and a variance-based Sobol sensitivity analysis. These methods reveal the range of variability in the result arising from uncertainty in the input assumptions, including those which most impact performance, thus identifying high-risk areas for project monitoring and intervention. These can not only support the design stage of the REC but also contribute to risk-aware planning and policy development. The model’s development in Python allows for a scalable foundation on which future research can be built, and contribute to the commercialisation of an REC-focused planning tool. The outcome of this work provides a novel, quantitative guide for energy developers, government entities, and network operators on REC development. The model framework can be used to trade-off system cost and emissions reduction, design for and navigate potential future energy policy, assess energy equity, and ensure a clearer route to realising the net-zero aspirations of rural, islanded communities. Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London

2025-01-01T00:00:00Z Rrustemi, Dardan Naim http://bura.brunel.ac.uk/handle/2438/32195 2025-12-14T16:17:37Z 2024-01-01T00:00:00Z

Title: Thermodynamic simulation and exergy analysis of a hydrogen SI engine Authors: Rrustemi, Dardan Naim Abstract: Concerns of limited fossil fuel reserves, environmental pollution from their extraction, processing, and use, and health effects from localised tailpipe emissions are leading to a transition of the transportation sector towards low-carbon and carbon-free alternative fuels for internal combustion engines. As an alternative fuel hydrogen has the potential to significantly reduce tailpipe greenhouse gas emissions, and offers advantages in terms of its combustion properties. To understand hydrogen combustion in an internal combustion engine and the upper limit of efficiency, single- and two-zone combustion models exploiting the second law of thermodynamics are developed to assess the origins of the exergy losses. The single-zone model provides detailed analysis of the boosted operation strategy, showing that thermal efficiency increases significantly for lean-burn hydrogen mixtures. Operating hydrogen engines at high loads presents challenges arising from combustion abnormalities as increasing intake air pressure raises in-cylinder temperature, significantly increasing knock occurrence and nitric oxide emissions. However, low-temperature combustion through lean-burn and water injection has potential to mitigate combustion abnormalities and reduce nitric oxide emissions; the addition of water modulates the rate at which combustion occurs. A newly developed laminar flame speed correlation for hydrogen-air combustion accounts for water addition under engine-relevant conditions. The applicability of this new correlation is demonstrated by incorporating this empirical correlation into a two-zone combustion model to predict engine performance, combustion abnormalities and nitric oxide emissions. The simulation of a water-diluted hydrogen engine indicates that emission control and knock mitigation are achievable, but requires careful optimization to avoid significant reducing thermal efficiency. The simulations allow the production of a hydrogen operational map based on the indicated specific fuel consumption, nitric oxide, thermal efficiency, equivalence ratio, and water addition. A comprehensive exergy analysis of a hydrogen engine evaluates efficiency, irreversibility, and emissions, quantifying losses for each engine condition: intake manifold air pressure, fuel mixture, compression ratio, water addition, and spark timing. This enables a discussion of the compromises for designing and managing hydrogen-fuelled SI engines at various operating conditions, including equivalence ratios, spark timings, compression ratio, and boosted manifold air pressure. Description: This thesis was submitted for the award of Doctor of Philosophy and was awarded by Brunel University London

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