With the increasing adoption and usage of hybrid electric vehicle (HEV) technologies, there is a growing recognition that attributes such as dynamics, driveability and refinement can have an adverse affect on customer acceptance. There are a number of new challenges associated with their refinement, in particular their sound quality. These issues include: understanding customers’ perceptions of new sound sources, such as electric motor/generators (M/G) and electronic switching devices; reduced masking from the internal combustion engine (ICE); the effect that a more advanced control strategy can have on vehicle-level sound (both internally and externally); and the effect of new sound character on customer perception. Given these new challenges for the sound quality of HEVs, the best approach for learning about perceptions needed to be determined. Interactive noise, vibration and harshness (NVH) simulation is well suited to further our understanding of these issues. The process for developing models for interactive NVH simulation of conventional vehicles is well established. However, research was necessary to both enhance this process for the creation of HEV models and to create new assessment methods. This report gives a brief overview of a project to deliver this. The key stages were: classification of unique HEV operations; development of a HEV NVH model; validation of the NVH model to determine its suitability for interactive simulation; leading onto recommendations for the use of new HEV sound quality models for assessment. An interactive HEV model has been successfully created and used in a number of newly created HEV sound quality evaluations. Three assessments were created and carried out which addressed new HEV related refinement issues of varying ICE masking, varying control strategy and the effect of added interior synthesized sound on customer perception. Key findings included: preference for reduced internal combustion engine (ICE) sound in the Toyota Prius and significant differences in perception of the same HEV, over the same drive cycle with varying initial battery state-of-charge (SoC). The process developed and carried out and learning achieved has been documented as a selection of flowcharts and can be used by OEMs or sound specialists as a means for improving HEV sound quality.

The first approach utilises a thin film of acrylic that is moulded onto the outside of a polycarbonate substrate. It was found that the gate of the injection mould cavity must be of uniform cross section otherwise local shear heating can occur and melt the acrylic film. The injection gate must also be located entirely on one side of the mould cavity otherwise the film is punctured by the molten polycarbonate and free to float within the cavity. Any mixing of the two materials will lead to opaque components due the difference in the refractive indices. The film was found to improve the UV resistance of any component, acting as a protective buffer for the polycarbonate. A new variety of hardcoat was applied to film-backed samples to impart abrasion resistance and samples were found to outperform commercially available alternatives under recognised laboratory conditions. The film-backed samples also exhibited excellent impact resistance when impacted upon the film-face. However, similar components failed at extremely low energy levels when impacted from the non-film face because flaws in the acrylic film caused cracks to be initiated when the film was placed into tension. The level of adhesion between the film and the polycarbonate has been found to be critical and if the failure mechanism could be guaranteed, then intruder resistant glazing that could be broken from the inside in an emergency becomes a possibility. Such a product would address the identified consumer concern of being trapped in a vehicle. The second approach utilises simultaneous dual injection moulding (2K), which has previously only been used to manufacture coloured components. A successful feasibility study was undertaken to demonstrate the concept of producing transparent components via such a process. This showed that much greater control is required for transparent applications otherwise the skin and core materials mix and opaque components are produced. The generally accepted academic principles associated with the process have been shown to be too simplistic and cannot be relied upon to guarantee good results. The ratio of viscosities of the skin and core materials appear to be more dominant than previously thought and the relative injection speeds of the two materials has a direct influence upon interfacial mixing and haze generation. It was also found that haze could be avoided if the refractive indices of the skin and core material were matched to within ±0.002, but this is impractical. A third area of research examined the feasibility of introducing structured glass fibres weaves into transparent components to improve rigidity. The study resulted in the construction of a transparent glass fibre pre-preg that could be moulded onto the outer surface of polycarbonate components. Flexural tests revealed that a single layer of glass fibre increased the flexural modulus of test samples by a factor of 3, whilst transparency and clarity were retained. Two patents have been filed as a direct result of this work.

Environmental and commercial pressures have forced the aerospace industry to look at alternatives to riveting for the manufacture of aluminium aircraft structures. This resulted, at the end of last century, in an extensive study by Airbus into the possiblities of using CO2 lasers, which led to the process being implemented for a (small) number of stringer-to-skin fuselage panels in the newer Airbus models. Since this initial commercial success, new laser sources have become available that are more suitable for the welding of aluminium than CO2 lasers, in the form of Nd: YAG and Yb-fibre lasers. Both produce a wavelength that is absorbed more efficiently by aluminium alloys than the CO2 laser wavelength, resulting in an improved keyhole stability, as demonstrated in the late nineties for Nd: YAG lasers. In addition, Yb-fibre lasers have become available at output powers higher than available for Nd: YAG lasers, allowing thicker sections of aluminium to be welded in a single pass. However, despite their claimed advantages, no efforts were made to demonstrate the potential of these lasers for (aluminium) aircraft manufacture. For this reason, the author initiated a series of studies in 2001, with the overall aim to develop procedures to laser weld both thin (3.2mm) and thicksection (12.7mm) aerospace aluminium alloys using these fibre-delivered lasers to a weld quality, in particular related to weld metal porosity, suitable for aerospace service. The focus in this research was on weld metal porosity, because this is a particular problem when laser welding aluminium, either in the form of fine (hydrogen) porosity or larger porosity associated with an unstable keyhole behaviour. The benchmark weld metal porosity for this study was obtained from the stringent weld quality classes defined in BS EN 13919-2 and AWS D17.1. The approach to this research was in three parts, with work in the first aimed at demonstrating that a 3kW Nd: YAG laser was capable of producing low-porosity welds in 3.2mm thickness 2024 aluminium alloy, and thus can be considered for replacing the CO2 laser currently used for the stringer-to-skin fuselage application. Prior to the final part of the research, in which a 7kW Yb-fibre laser was used to demonstrate that these benchmark porosity levels could also be achieved in thicker section (aerospace-grade) aluminium, a comparison study was carried out to quantify the difference in welding performance between the Nd: YAG and the Yb-fibre laser. At an output power of 4kW focused in a 0.4mm diameter spot, the Yb-fibre laser was capable of a 30% higher welding speeds in 4mm (5083) aluminium alloy, or a 20% increase in depth of penetration for welding speeds between 1 and 15m/min, compared with the Nd: YAG laser. This improvement in welding performance, together with an output power of 7W, produced full penetration in 12.7mm thickness (aerospace-grade) AI-Zn-Mg-Cu aluminium alloy using the Yb-fibre laser autogenously, or in a hybrid configuration with a MIG arc. Both the autogenous laser and hybrid laser-MIG process were capable of producing welds with a weld metal porosity in line with the BS EN 13919-2 and AWS D17.1 benchmark conditions, at welding speeds of 0.55 and 0.75m/min, respectively. At these production rates, the 248 metres of stringer incorporated in a typical aluminium wing structure can be welded in 7.5 and 5.5 hours, in case of autogenous laser and hybrid laser-MIG, respectively, compared with 37.6 hours currently needed for the riveting process.

With the expected continued increases in air transportation, the mitigation of the consequent delays and environmental effects is becoming more and more important, requiring increasingly sophisticated approaches for airside airport operations. The ground movement problem forms the link between other airside problems at an airport, such as arrival sequencing, departure sequencing, gate/stand allocation and stand holding. The purpose of this thesis is to contribute to airport ground movement research through obtaining a better understanding of the problem and producing new models and algorithms for three sub-problems. Firstly, many stakeholders at an airport can benefit from more accurate taxi time predictions. This thesis focuses upon this aim by analysing the important factors affecting taxi times for arrivals and departures and by comparing different regression models to analyse which one performs the best for this particular task. It was found that incorporating the information of the airport layout could significantly improve the accuracy and that a TSK fuzzy rule-based system outperformed other approaches. Secondly, a fast and flexible decision support system is introduced which can help ground controllers in an airport tower to make better routing and scheduling decisions and can also absorb as much of the waiting time as possible for departures at the gate/stand, to reduce the fuel burn and environmental impact. The results show potential maximum savings in total taxi time of about 30.3%, compared to the actual performance at the airport. Thirdly, a new research direction is explored which analyses the trade-off between taxi time and fuel consumption during taxiing. A sophisticated new model is presented to make such an analysis possible. Furthermore, this research provides the basis for integrating the ground movement problem with other airport operations. Datasets from Zurich Airport, Stockholm-Arlanda Airport, London Heathrow Airport and Hartsfield-Jackson Atlanta International Airport were utilised to test these sub-problems.

Correct assignment of airport resources can greatly affect the quality of service which airlines and airports provide to their customers. Good assignments can help airlines and airports to keep to published schedules, by minimising changes in these schedules and reducing delays. Given the expected increases in civil air traffic, the complexities of resource scheduling and assignment continue to increase. For this reason, as well as the dynamic nature of the problems, scheduling and assignment are becoming increasingly more difficult. The assignment of baggage sorting stations to flights is one of the resource assignment problems at an airport, and like many other real world optimisation problems, it naturally has several objectives, which conflict with each other. A model of the problem is presented, different approaches to obtaining good solutions are looked at and studied to gain an insight into their qualities. Furthermore, algorithms are studied to improve the already good solutions obtained by the approaches considered and their performance is studied where some characteristics of the problem change, such as the number of baggage sorting stations or the topology of the airport. Changes to the flight schedule on the day of operation may invalidate previous assignments of flights to resources. These perturbations may not only affect the disrupted flights but also other flights already assigned. Some existing approaches are looked at, and others are suggested to take account of these potential perturbations at the time the assignments are generated with the aim of mitigating their detrimental effect on the day of operation. The constructive search algorithms and robustness methods are potentially important in a wider variety of problems other than the Airport Baggage Sorting Station Assignment Problem (ABSSAP). By way of illustration, the same techniques are applied to the widely studied Airport Gate Assignment Problem (AGAP).

This thesis explores the institutional and cultural development of the British Interplanetary Society (BIS) and its influence in wider cultures of ‘British outer space’ in the mid-twentieth century. The Society was founded in 1933 in Liverpool by P E Cleator, and having attracted a small group of enthusiastic members before the outbreak of the Second World War, successfully re-grouped after the conflict and grew to become one of the most influential of all the space flight societies by the 1960s. The thesis starts by examining the ways in which the discipline of geography has recently started to re-engage with outer space as a field of enquiry, and suggests that geopolitical and cultural approaches to studying outer space would be a productive academic pursuit. The empirical chapters start by looking at the institutional cultures of the BIS, and explore the relationship between the Society and the production of interplanetary knowledge. The Society’s global connections and internationalist stance are also brought into focus, with contrasting accounts identified before and after the war raising questions about the geopolitics of British outer space. The empirical chapters go on to study how the BIS became connected to the wider world of popular culture in Britain, examining imaginative and amateur representations and performances. This section includes analyses of certain science fiction texts, including the selected novels of Olaf Stapledon, Arthur C Clarke and C S Lewis, and also considers Frank Hampson’s Dan Dare space adventure comics and the long-running television series The Sky at Night, whilst maintaining an empirical connection to the BIS throughout. The thesis closes with a discussion of what it means to bring together materials from both institutional and popular cultures, in the context of the emerging research area of the geographies of outer space.

As the More-Electric Aircraft (MEA) has been identified as a major trend of future aircraft, the on-board Electrical Power System (EPS) will see significant increased numbers of Power Electronic Converters (PECs) and motor drive systems. In order to study the behaviour and performance of the EPS in MEA, extensive simulation studies need to be done during the system design process. This in return, gives the need to have computationally efficient and accurate models to reduce the design period. In this thesis, the Dynamic Phasor (DP) is used for modelling EPS in the MEA. The DP technique is a general averaging method and naturally a frequency-domain analysis tool. Compared with other averaging models, which is only efficient under balanced conditions, the DP model maintains efficiency under both balanced and unbalanced conditions. The DP technique has been widely used in modelling the constant, single frequency EPS. In this thesis, the DP technique is extended to modelling time-varying frequency EPS. The application of DP in modelling a multi-generator, multi-frequency system is for the first time, developed in this thesis. The developed theory allows a wider application of the DPs. The developed DP model covers key elements in MEA electrical power systems, including the synchronous generator, control, transmission lines, uncontrolled rectifiers, PWM converters and 18-pulse autotransformer rectifier units. The DP model library developed based on this thesis allows the flexibility to study various EPS’s by integrating elements from the library. A twin-generator aircraft EPS, which is based on the More Open Electrical Technology (MOET) large aircraft EPS architecture, is used to demonstrate the application of DP models. Comparing the DP model with the ABC model (models in three-phase coordinates) and the DQ0 model (models in a synchronous dq frame), the efficiency and the accuracy of the DP model are demonstrated under both balanced and unbalanced conditions.

Electrical machines for aerospace applications often operate close to the allowable thermal limits due to high power density requirements. The power density of electrical machines is generally dependent on the machine and thermal management design. At flight level, a reduced pressure exists which in turn results in more challenging thermal management. Aerospace electric machine manufacturers are often limited with respect to the implemented cooling mechanisms. That is, natural convection systems are the norm, as fan cooled and fluid cooled machines may suffer from reliability issues. The original contribution of this work, is the design, testing, and implementation of an alternative forced cooling convective system (FCCS) based on piezoelectric fans. This thesis commences by an investigation of the capabilities of MotorCAD (a sophisticated analytical lumped thermal package) and how it can be utilised in a fully integrated way to optimise (for a maximum power density and an overall minimum motor mass) both the electromagnetic and thermal aspects of a typical traditional horizontally-mounted permanent magnet synchronous machine (PMSM) operating at flight level. The resultant analytical temperature values were then compared to actual experimental temperature data. Piezoelectric fans are then investigated as a potential, fault tolerant FCCS that may enhance the overall cooling of a motor. These fans could be implemented in the aerospace industry as they do not suffer from the same reliability issues as traditional FFCS’s. Detailed thermal results indicating the effective piezoelectric fan cooling range together with the overall cooling effectiveness over a traditional vertical straight-finned heat sink (unit – cell) , operating under different operating conditions are also presented. Furthermore, the fin/fan geometry that minimises the thermal resistance whilst minimising the overall cooling mass is presented. Particle Image Velocimetry (PIV) techniques were implemented to further understand the flow fields generated by an oscillating piezoelectric fan. Common parameters governing the fluid flow (vibration amplitude, separation distance, fin spacing and fan orientation) were investigated and the results are herewith presented. Designs of a supporting structure for the proposed FCCS implementation are drawn up and analysed through FEA. A prototype structure was built and its durability tested. Furthermore, the reliability (fault tolerance) of the suggested FCCS was evaluated. The feasibility of implementing this innovative cooling technique was further investigated by performing a study on the weight saving potential of the FCCS over traditional natural convective fins, and the FCCS geometry that minimises the thermal resistance whilst minimising the overall mass is selected. Furthermore, a prototype FCCS was built and tested.

Turbulent boundary-layer control has been investigated experimentally using a low-speed wind tunnel at the University of Nottingham, with an overall aim of achieving skin-friction drag reduction. The important part of this investigation is to understand the mechanism of drag reduction and the associated changes in the structure of the turbulent boundary layer. It was demonstrated with Direct Numerical Simulations (DNSs) nearly a decade ago that by applying a spanwise travelling wave in the near-wall region of a turbulent wall flow can lead to a skin-friction drag reduction on the order of 30%. To date, spanwise travelling waves are predominantly created by a Lorentz force, limiting the study of this technique to water flows and numerical investigations. As an aeronautical application of this innovative flow control technique, an investigation into the use of Dielectric-Barrier-Discharge (DBD) plasma actuators to generate spanwise travelling waves in air has been conducted. DBD plasma actuators have received enormous interest over the past ten years within the flow control community due to their unique properties. DBD plasma actuators are completely electrical and ionize the nearby air to couple momentum to the surrounding flow. Hence, DBD plasma actuators require no moving parts, which makes their design simple and without the need for complicated ducting, holes or cavities. They are fast acting, of low power, low in weight, cheap to manufacture and can be fitted to existing airframes. As the body force that the DBD plasma actuator creates is at the wall, DBD plasma actuators are an ideal candidate for wall-based flow control techniques such as the spanwise travelling wave-technique. In this study, DBD plasma actuators have been found to have the ability to greatly modify the near-wall region of the turbulent boundary layer with a potential to reduce skin-friction drag. The near-wall structures modified by the spanwise travelling waves were studied using the PIV technique, while the associated turbulence statistics were carefully documented using hot-wire anemometry. On initiation of DBD plasma in the turbulent boundary layer, streamwise vortices were generated. Spreading of low-speed fluid by the streamwise vortices that were travelling in the spanwise direction was observed, which seems to have greatly attenuated the turbulence production process. This is very much in line with the finding of DNS studies, where wide low-speed ribbons replaced the low-speed streaks.

The high cost of raw materials, high labour costs and lengthy cycle times have limited the use of conventional ply-based composites in the automotive industry. This thesis seeks to identify the potential of using low cost discontinuous fibre composites (DFCs) for structural applications. Properties of DFCs are governed by the degree of homogeneity of the reinforcement and discontinuities at the fibre ends, which cause stress concentrations; thereby limiting the mechanical performance of the material. This work focuses on material characterisation of laminates moulded from discontinuous carbon fibre preforms manufactured by a robotic spray process. Through the culmination of this work, a suitable design methodology for automotive applications has been identified. Design procedures for aerospace have also been considered. An analytical model has been developed to determine the tensile stiffness and strength of a discontinuous carbon fibre preform composite. The model can be used within automotive and aerospace design methodologies to define material properties, but a number of other factors must be considered. Areal mass of the preform has been identified as the governing factor in achieving target compaction levels. Poor homogeneity in thin parts prevents the ability to achieve high volume fractions, which determines mechanical performance. It has been demonstrated that the matrix has a greater influence on the properties of DFCs when compared to continuous fibre composites. Toughened resins were particularly effective in improving tensile strength of DFCs that exhibited poor homogeneity. Damage tolerance of DFCs has been evaluated through open-hole and compression after impact testing. Higher property retention was observed compared to continuous fibre equivalents. Greater damage tolerance of DFCs could lead to increased weight-saving in structural applications. However, current safety factors based on conventional laminates may be too conservative and could lead to over-engineering thus limiting the potential of the material.