This collection contains the Doctoral and Masters by Research theses produced within the department.
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Aircraft Electrical Propulsion for High-Speed Flight: Rim Driven Fan (RDF) TechnologyThe aim of this programme of studies is to research and develop electrical Rim Driven Fan (RDF) technology for high-speed aircraft propulsion and to provide knowledge to support Society’s efforts to combat climate change using zero-emission technologies. The objectives were to conduct research into the state-of-the-art of aircraft electrical propulsion, to estimate the performance of single and dual stage contra-rotating fans over a range of diameters, to provide a methodology to enable the aerodynamic design and detailed Computational Fluid Dynamic (CFD) analyses of small contra-rotating fans and to create a conceptual design for an RDF device suitable to power an unmanned aircraft. In completing this work, literature reviews were carried out on electrically powered propulsion for aircraft, electrical motor technologies and rim drive technology for aircraft propulsion. Original research was undertaken in the form of aerodynamic analyses, using derived numerical and CFD techniques, to determine the optimum performance of single and dual stage (contrarotating) rim driven fans for high-speed electric aircraft applications. Original research was also undertaken in the form of electrical analyses using Motor-CAD finite element software to analyse the feasibility of novel rim-drive concepts such as slotless stator designs, aluminium windings and iron-less rotors with Halbach magnet arrays in an RDF context. The results of these studies have contributed new knowledge that has been peer-reviewed and internationally published. An original RDF design concept, suitable to power an unmanned aircraft, was devised and a UK patent application filed. The main findings of this work are that RDF technology offers a viable means of high-speed aircraft propulsion with a dual-stage contrarotating, air-cooled fan arrangement. That optimum RDF power density is achieved with slotless windings and iron-less rotors configured with Halbach magnet arrays which reduce their rotating mass. These findings have enabled a feasible novel RDF design to be created which is a significant contribution in the field of electrical aircraft propulsion. The results of this work also contribute the significant new knowledge that dual stage contra-rotating RDF configurations provide the potential for an increase in thrust per frontal area, and higher exhaust-air velocities, when compared with existing hub-driven fan technologies. This work has established a novel fan design technique, that can be used by technologists to analyse and design future electrical fan concepts, and offers a significant contribution towards Society’s efforts to combat climate change with zero-emission technologies. Opportunities for further areas of study in this field are in the analyses of large diameter high thrust versions of RDFs suitable for large manned aircraft and hovercraft applications.
Controller Design Methodology for Sustainable Local Energy SystemsCommercial Buildings and complexes are no longer just national heat and power network energy loads, but they are becoming part of a smarter grid by including their own dedicated local heat and power generation. They do this by utilising both heat and power networks/micro-grids. A building integrated approach of Combined Heat and Power (CHP) generation with photovoltaic power generation (PV) abbreviated as CHPV is emerging as a complementary energy supply solution to conventional (i.e. national grid based) gas and electricity grid supplies in the design of sustainable commercial buildings and communities. The merits for the building user/owner of this approach are: to reduce life time energy running costs; reduce carbon emissions to contribute to UK’s 2020/2030 climate change targets; and provide a more flexible and controllable local energy system to act as a dynamic supply and/or load to the central grid infrastructure. The energy efficiency and carbon dioxide (CO2) reductions achievable by CHP systems are well documented. The merits claimed by these solutions are predicated on the ability of these systems being able to satisfy: perfect matching of heat and power supply and demand; ability at all times to maintain high quality power supply; and to be able to operate with these constraints in a highly dynamic and unpredictable heat and power demand situation. Any circumstance resulting in failure to guarantee power quality or matching of supply and demand will result in a degradation of the achievable energy efficiency and CO2 reduction. CHP based local energy systems cannot rely on large scale diversity of demand to create a relatively easy approach to supply and demand matching (i.e. as in the case of large centralised power grid infrastructures). The diversity of demand in a local energy system is both much greater than the centralised system and is also specific to the local system. It is therefore essential that these systems have robust and high performance control systems to ensure supply and demand matching and high power quality can be achieved at all times. Ideally this same control system should be able to make best use of local energy system energy storage to enable it to be used as a flexible, highly responsive energy supply and/or demand for the centralised infrastructure. In this thesis, a comprehensive literature survey has identified that there is no scientific and rigorous method to assess the controllability or the design of control systems for these local energy systems. Thus, the main challenge of the work described in this thesis is that of a controller design method and modelling approach for CHP based local energy systems. Specifically, the main research challenge for the controller design and modelling methodology was to provide an accurate and stable system performance to deliver a reliable tracking of power drawn/supplied to the centralised infrastructure whilst tracking the require thermal comfort in the local energy systems buildings. In the thesis, the CHPV system has been used as a case study. A CHPV based solution provides all the benefits of CHP combined with the near zero carbon building/local network integrated PV power generation. CHPV needs to be designed to provide energy for the local buildings’ heating, dynamic ventilating system and air-conditioning (HVAC) facilities as well as all electrical power demands. The thesis also presents in addition to the controller design and modelling methodology a novel CHPV system design topology for robust, reliable and high-performance control of building temperatures and energy supply from the local energy system. The advanced control system solution aims to achieve desired building temperatures using thermostatic control whilst simultaneously tracking a specified national grid power demand profile. The theory is innovative as it provides a stability criterion as well as guarantees to track a specified dynamic grid connection demand profile. This research also presents: design a dynamic MATLAB simulation model for a 5-building zone commercial building to show the efficacy of the novel control strategy in terms of: delivering accurate thermal comfort and power supply; reducing the amount of CO2 emissions by the entire energy system; reducing running costs verses national rid/conventional approaches. The model was developed by inspecting the functional needs of 3 local energy system case studies which are also described in the thesis. The CHPV system is combined with supplementary gas boiler for additional heating to guarantee simultaneous tracking of all the zones thermal comfort requirements whilst simultaneously tracking a specified national grid power demand using a Photovoltaics array to supply the system with renewable energy to reduce amount of CO2 emission. The local energy system in this research can operate in any of three modes (Exporting, Importing, Island). The emphasise of the thesis modelling method has been verified to be applicable to a wide range of case studies described in the thesis chapter 3. This modelling framework is the platform for creating a generic controlled design methodology that can be applied to all these case studies and beyond, including Local Energy System (LES) in hotter climates that require a cooling network using absorption chillers. In the thesis in chapter 4 this controller design methodology using the modelling framework is applied to just one case study of Copperas Hill. Local energy systems face two types of challenges: technical and nontechnical (such as energy economics and legislation). This thesis concentrates solely on the main technical challenges of a local energy system that has been identified as a gap in knowledge in the literature survey. The gap identified is the need for a controller design methodology to allow high performance and safe integration of the local energy system with the national grid infrastructure and locally installed renewables. This integration requires the system to be able to operate at high performance and safely in all different modes of operation and manage effectively the multi-vector energy supply system (e.g. simultaneous supply of heat and power from a single system).
A critical evaluation of students' attitudes to electronic learning at the University of ChesterThe research described in this thesis reports the results of a study into the adoption of e-learning strategies based on the use of the World Wide Web (WWW) and Internet. Through an extensive and critical literature review, it exemplifies how higher education uses intranets to deliver learning and support services to their student population. The overall aim of this research was to investigate how e-learning at the University of Chester might more effectively support students' learning needs, thereby improving their experience of e-learning. Students were given a mode of study, either face-to-face (64 subjects) or experimental using online intranet delivery (66 subjects). The course used for this study was a 13 week, Level Two undergraduate computer course taken by non-computing students. Quantitative and qualitative data were collected and analysed. The results reveal significant differences between the performance of the e-learning and face-to-face groups with e-learning students performing poorly when compared to their face-to-face peers. A lack of responsiveness in tutor support and student motivation were established as being major contributing factors as well as differences in the students' individual learning profiles. The research concludes that e-learning, although promoted as being anytime and anywhere is limited in its flexibility and responsiveness in the context in which it was assessed. Most e-learning activities at the University of Chester can be described as 'one size fits all'. They require students to read printed text, carry out further work, research or exercises, and post written comments to a discussion board. There is little evidence that individual student needs and preferences are being considered or supported. With the move towards blended learning in educational institutions, e-learning strategies are being used as a regular part of the curriculum to enhance the student experience. This research provides alternatives for the development and delivery of more individually tailored e-learning courses and provides strategies for supporting students in virtual environments more effectively. The thesis concludes by proposing a new model for e-learning based on these results coupled with a self-critical review and proposals for further research.