The internal combustion (I.C.) engine remains unrivalled as the primary means of road vehicle propulsion. The frequency of re-fuelling stations, combined with the high energy density of both gasoline and diesel fuel provide users with unrivalled flexibility and vehicle range. However a range of environmental and health concerns exist surrounding I.C. engine emissions; in particular carbon dioxide (CO2), nitrous oxides (NOx), hydrocarbons (HC) and carbon monoxide (CO). There is therefore increasing pressure on vehicle OEMs to reduce vehicle emissions through tightened emission standards and regulations. A significant challenge in meeting these tightened regulations is the reduced efficiency of the I.C. engine during cold-start which reduces from typical values of 40% when fully warm to values as low as 10% when cold. Increased friction in the engine caused by overly viscous lubricants providing sub-optimal lubrication during cold starts is a primary cause of this reduction in efficiency during cold-start. This is despite the advancements in lubricant technology made that has reduced the sensitivity of lubricant viscosity to temperature variation. It is therefore desirable to increase the rate of lubricant heating during engine warm-up so that optimal lubrication conditions are reached sooner and frictional losses are reduced. The reduction in frictional losses therefore reduces fuel consumption and hence emissions. In this thesis, the merits of insulating engine oilways are investigated as a means to reduce thermal losses from the lubricant and thus accelerate warm-up rates using a bespoke oil flow rig and simulation model. Through this work, it has been found that, using insulating inserts, it is possible to reduce the thermal losses from the lubricant to the surrounding wall structure by up to 58%. Such reductions have been achieved by installing an insulating insert into the oilway (also commonly referred to as a gallery in I.C. engines) that combines a low thermal conductivity material but also introduces a contact resistance between the insert and the surrounding metal. It has been found that the contact resistance is a highly significant and beneficial feature and, using special inserts designed to enhance the contact resistance, reductions in thermal losses of up to 40% can be achieved using the contact resistance alone without using low thermal conductivity materials. A computational finite difference model has been developed to simulate heat transfer between flowing engine lubricant and the gallery walls. The model has been correlated with experimental data from the oil flow rig and is capable of simulating the effects of changing the materials properties (density, specific heat capacity and thermal conductivity) of both insulating inserts and the surrounding metal structure. The model is also capable of investigating the effect of changing contact heat transfer coefficients and changing flow geometry and velocity. Through computational experiments with this model, it has been found that the optimum strategy to achieving reduced thermal losses from the lubricant through the gallery walls is to ensure that the thermal conductivity of the insulating insert and that the thermal mass of the surrounding structure are minimised. Computational experiments have also highlighted the need to consider the flow geometry of different regions of the engine with the variation in bore diameter affecting both the heat transfer surface area and the convective heat transfer coefficient through the Reynolds’ effect. It has been found that increasing the lubricant flow velocity for a given bore diameter increases thermal losses to the gallery walls as a result of the Reynolds effect. If the bore diameter is increased, the thermal losses from the lubricant reduce in uninsulated galleries owing to a reduction in the Reynolds number but the reverse happens in insulated galleries owing to the increase in heat transfer area. The change in trend is a result of the interactions between the changing convective heat transfer area, heat transfer coefficient and the temperature differential between the lubricant and gallery wall. In addition, implementation of the insulation into a running engine needs careful consideration to ensure that the insulation does not isolate the lubricant from a potential heat source (such as the cylinder head). The optimum locations will vary between engines but investigations suggest that the return galleries from the head to the sump represent a positive opportunity to reduce thermal losses from the lubricant with a clear reduction in lubricant temperature observed as the lubricant moves down the gallery.

The experience of comfort is an important factor in passengers’ acceptance of transport systems. Comfortable cabin environments can be used as a means to differentiate between aircraft manufacturers and airlines and therefore, may be a key marketing feature. In 2010 and 2011, the European Commission presented its vision for aviation in the year 2050, highlighting the importance of enhancing passengers’ experiences. They also envisaged the use of virtual reality (VR) to provide aircraft passengers with entertainment and a means of ‘escaping from the fast pace of society’. The VR-HYPERSPACE project addressed this vision by examining the use of virtual and mixed reality technologies to enhance passenger comfort on aircraft in the year 2050. This approach to increasing comfort would be comparatively cheaper than changing the physical parameters of an aircraft. This thesis presents a series of studies which investigated the ways in which two virtual environments (VEs) that were developed for the VR-HYPERSPACE project (one depicting a tropical island and one depicting the view outside of a low-flying aircraft, referred to as the ‘invisible aircraft VE’) could influence potential aircraft passengers’ comfort and experiences. The findings from these studies provide insight into the prospect of using VR to enhance passengers’ comfort and experiences in future flight from a user-centred perspective. An initial user study was carried out to gain an understanding of the ways in which the two VEs, with various combinations of motion tracking, affected people’s comfort and experiences. The results of this study showed that the VEs have the potential to enhance people’s experiences, for example, by giving them an enhanced perception of space and time. They also might provide people with unique opportunities if used in flight, for example to augment or escape the flight experience. The study identified that motion tracking enhanced the experience of the invisible aircraft VE but detracted from the relaxing nature of the tropical island VE. The findings of this study were used to select combinations of VEs and motion tracking configurations to be taken forward for further investigation. The initial study also identified that it was difficult to determine the extent to which VEs could enhance comfort when the participants were not exposed to discomfort. Consequently, a new approach to measuring the effect of interventions on discomfort was developed. This involved a workshop and a user study which were carried out to select and test sources of discomfort. Two common sources of discomfort were selected: the sound of a crying baby and restricted legroom. These were used subsequently to induce discomfort in participants in later studies. The final series of studies aimed to determine the extent to which VEs could distract people from sources of discomfort. The findings indicated that passive VEs could be used to either fully distract people from sources of discomfort or minimise their negative responses. However, the VE used was more effective at distracting people from the discomfort associated with restricted legroom than the sound of a crying baby. The findings indicated that VEs become more distracting when they are interesting and that when exposed to stressful stimuli, relaxing distractors may be beneficial. The findings also indicated that VEs can be used to support existing strategies which people might use to overcome sources of discomfort in present-day flight situations. This research considered existing research in both the comfort and the pain domains to develop a novel approach to enhancing passenger comfort through the use of VEs. The research showed that VEs have the potential to distract people from sources of discomfort which are commonly experienced in-flight and to enhance potential passengers’ flight experiences. Further investigation is required to understand whether VEs remain effective distractors over longer periods of time, when subject to multiple sources of discomfort and in real-world contexts.

In the last few years carbon dioxide received increasing attention as a possible replacement for fluorocarbon-based refrigerants used within present automotive A/C system technology. R-134a is harmless to the ozone layer but the greenhouse effect is more than 1300 times higher than that of an equivalent amount of CO2. Alternative refrigerants are natural gasses such as propane and butane, however these gasses are considered explosive. With many objections raised it appears if CO2 will be the future refrigrant for automotive use. One concern with R-744 is its high operating pressure and suction/discharge pressure difference when compared to common refrigeration processes. A major problem with the CO2 cycle is the loss of effciency at high ambient temperatures. With a COP optimized control system for the expansion value based on pressure, temperature and mass flow of the refrigerant, an effective A/C system for CO2 could be deleloped. This resrach offers basic knowledge of refrigerant cycles and gives an overall view of the refrigerant change-over problem. With the results obtained from the experimental work a better understanding of the CO2 cycle and a better understanding towards effective A/C systems have been realized.

No description available.

The internal combustion engine (ICE) has been used in automotive vehicles without any significant improvement in energy efficiency for over a hundred years. There are several possibilities for developing a ‘greener’ and more powerful engine such as the homogeneous charge microwave ignition (HCMI) system. In this thesis, the HCMI system is analysed and investigated through simulation based ‘virtual prototyping’ in combination with an intelligent optimisation and a Computer-Automated Design (CAutoD) framework. The intention is to analyse and develop designs which could be used to transform the existing ICE ignition system to the HCMI system with minimal modifications to the existing engine. With the help of the finite element method (FEM), the microwave induced electromagnetic field in the engine cylinder is first simulated for `virtual prototyping' using a computer model. This then takes the prototyping methodology one step further, by replacing the process of human tuning of the prototypes with a computer-automated search process using computational intelligence. To realise this, an interface between the FEM model and the CAutoD framework is designed using the Application Programming Interface (API) of the FEM simulation software. This connection facilitates a rapid exchange of data between the simulation model and the search algorithm. Thus, rendering it possible to accommodate a wider exploration or a higher simulation resolution for superior and more accurate prototyping. Another contribution of this thesis is the improvement of the search performance, including the combination of deterministic and non-deterministic search algorithm as well as using a new technique to solve optimisation problems without using the frequency as an input variable. The knowledge gained from the analysis of nature-inspired algorithms is used to perform a pre-evaluation and hence to provide a population which guides a non-deterministic search towards potentially optimal directions for the global maximum. A CAutoD system is then developed to optimise digital prototyping on various aspects of the ignition device for the HCMI system. This helps deepen the understanding of relationships between the characteristic outputs of a design, and the input parameters that affect the performance of the device. The CAutoD system is first applied to a basic cylinder model, with one single antenna in the middle, to analyse the single variable changes for the antenna designs. It is discovered that the inner antenna length has a significant impact on the maximum electric field intensity inside the engine cylinder. Then it is applied to the design process involving multiple variable changes for the global optimum electromagnetic performance. The results are presented in multi-dimensional graphs, which illustrate the relevant relationships between the different input variables. For example, it is revealed that the resonance frequency is affected more by the piston position than by the antenna length, which underlines the importance of the correct and exact timing advance and control of the ignition event. Subsequent to the extensive and systematic analysis of different antenna designs and input variables, Computer-Automated Design (CAutoD) has been applied to various designs to expand the understanding and virtual prototyping of the HCMI system. The criterion for the best design is to first provide the highest possible electromagnetic propagation performance within the cylindrical cavity by using the lowest microwave input power. With this, the reection of the microwave energy from the cylinder back to the microwave source, under the geometric conditions of the cylinder and antenna model, will also be minimised. During the search process, the default antenna model was extended with an additional antenna, which leads to a dramatic decrease in the field, once the additional antenna is introduced. This determines, that any antenna at the outer shield of the coaxial cable and inside the cylinder head, interferes with the electromagnetic propagation inside the cavity and lowers the propagation performance. The results show that this field will break down the air-fuel mixture inside the cylinder because the field strength is comparable to that, created by a spark plug. Hence, a HCMI system can be designed to replace a spark ignition system without requiring physical modifications to the engine cylinder.

No description available.

This thesis presents the research carried out to develop and optimise a novel aerodynamic add-on device for commercial vehicles which would reduce overall fuel consumption without any impact of vehicle aerodynamic stability. A prototype of such a device has been manufactured with existing legal and operational restrictions in view. Additionally, effects of such a device on the rollover stability of a commercial vehicle have been investigated and quantified. This has been done by developing a set of analytical methods to first quantify aerodynamic forces in terms of vehicle shape and flow conditions and then to predict the stability of road vehicles, both using mathematical models formulated using available data.

Electrical power demand in aircraft has grown significantly over the last century, and this trend continues with the More Electric Aircraft (MEA) and All Electric Aircraft (AEA) concepts. Higher voltages such as 270VDC are required to deliver additional power to loads and to optimise aircraft mass. Increased voltages inflict more stress on the Electrical Wiring Interconnect System (EWIS) and increase the impact of series arc faults caused by wiring defects. Solid State Power Controllers (SSPCs) are used to provide fast protection in high voltage distribution systems. The aim of this work is the characterisation, modelling, simulation and detection of series arc faults in 28VDC and 270VDC electrical power distribution systems featuring SSPCs. The majority of passive detection schemes in the literature were designed based on empirical data rather than well characterised electric arc parameters, and thus nuisance trips are unavoidable. To address this series arc faults in 28VDC and 270VDC solid state power distribution systems were characterised using the SAE5692 "Loose terminal" method [8], and it was found that 270VDC arc faults cause a minimal ~5.6% reduction in loop current and load voltage compared with ~54% in 28VDC systems. SSPC output voltage transients caused by series arcs were found to be limited by the presence of SSPC snubbers. Increasing the system loop inductance was found to improve series arc stability resulting in fewer arc quench events. Increasing the capacitive load reduces arc stability and causes arcs to quench more readily thus simplifying detection. These results were later used to experimentally validate a novel series arc fault SPICE model based on the static Nottingham V-I model [9] and wider solid state electrical system model. The arc current and SSPC output voltage results were also used to create a prototype passive series arc fault detection system, which has been demonstrated to SAE5692 under laboratory conditions [8]. A novel multilayer PCB current sensor was developed and experimentally validated for this prototype. To further reduce nuisance trips an innovative active arc fault perturbation scheme was simulated and experimentally demonstrated using SSPC modulation to stimulate and detect arc quench. Another novel complementary series arc fault prevention / confirmation scheme was simulated and experimentally validated using SSPC leakage currents. To minimise nuisance trips due to manufacturing and installation errors a unique Built-In Test (BIT) scheme was also developed and experimentally validated using the SSPC to create artificial current and voltage stimuli.

M.Sc. / It is estimated that there are approximately 6.9 million vehicles operating on South African roads, four million (58%) of which represent passenger cars. (Mbendi, 2002a). The number of vehicles operating on national roads increase annually. For motor vehicle engines to perform optimally, among other components, they require engine oil. Nationally in 2002, approximately 40 million litres of motor oil were sold at service station forecourts. For the same period, Gauteng motor oil sales exceeded 17.5 million litres while 76% of these sales occurred in Johannesburg (Maneveld, 2003b). When motor oil is poured into an engine there is always an amount of oil that remains in the container. In this study the author quantifies the amount of unused motor oil that is discarded into the environment via the containers that carry it and makes an assessment of the associated environmental implications. In the South African context, no documented data regarding this problem exists. Chapter one provides the background and motivation to the study, an explicit description of the problem being researched, objectives of the research, the study area and a brief description of the research methodology. This chapter defines the parameters within which the research took place. Chapter two briefly describes the South African oil and lubricants industry. It also focuses on lubricant manufacture, blending, composition, use and properties of lubricants. Chapter three details the research methodology and data collection procedures. This is followed by an analysis of the pilot and main study encompassing statistical interpretation and synthesis. Graphical and photographic illustrations are used. Conclusions were reached on the basis of factual information. Chapter four collates the information from previous chapters, which enables the author to make projections and quantify the amount of unused oil discarded into the environment. An assessment of the associated environmental implications is then determined. In the last chapter, limitations of the study are discussed. This is followed by concluding statements, proposals for further research and recommendations to address the research problem.

M.Tech. (Mechanical Engineering) / This dissertation focuses on understanding the relation between aerodynamic drag and aerodynamic lift in modern passenger cars and explores what effect these forces have on a vehicle. Modern cars are capable of exceptionally high speed and are subjected to large destabilizing lift forces at these speeds. To counteract the effects of positive lift, various aerodynamic devices and body design details are included in the typical car design. These devices often increase the vehicles aerodynamic drag, reducing energy efficiency as speed increases. The problem that this project aims to address is that at typical commuting speeds where lift forces are low these counter lift devices are not required, however because these devices are fixed the losses associated with their increased drag is still incurred. The devices can however not be excluded from the design as they are required on occasions that the vehicle is driven at abnormally high speed and lift forces become large. The losses associated with the increased drag of such devices are incurred over the vehicles full range of speeds even though the devices are only required at higher speed. The objective of this project is to develop an aerodynamic system that allows the vehicle to continuously and autonomously adjust its drag vs. lift properties to an optimal compromise that suits the vehicles instantaneous aerodynamic requirements. The system offers improvements in both handling and breaking performance as well as increased energy efficiency. The feasibility and effectiveness of the developed system is compared against the performance of a standard test vehicle and against the same test vehicle equipped with various traditional fixed aerodynamic devices. The methods used to develop, analyse and compare the various test models include both practical testing of a physical vehicle and computer based simulation using a digitized model of the same vehicle. Practical testing was conducted at Gerotek test facilities in Pretoria, South Africa and includes measuring the flow rate through the engine cooling system to determine the drag contribution of the cooling system to total vehicle drag. Coast-down testing is used to characterise the test vehicles rolling resistance and skid-pan or circuit tests are used to characterise the vehicles handling properties. Acceleration and breaking tests are also performed. Data from these tests are recorded through various on-board data logging units with pitot tube, GPS and accelerometer devices as inputs. A 3D model of the test vehicle is compiled using photogrammetry software to capture the profile and dimensions of the test vehicle into digital form. A 3D CAD model is developed from the vehicle scan and is used for CFD simulations to solve for the vehicles aerodynamic properties and to assist in the design and incorporation of the various adjustable aerodynamic devices required for the project. The data accumulated through computer simulation and practical testing is combined to form a statistical computer model of the standard vehicle. Research is conducted on existing aerodynamic devices common to passenger cars and suitable devices are adapted to three additional computer models: One with an adaptive aerodynamic system and two with fixed aerodynamic configurations of different intensities. The performance and energy efficiency of the four models are analytically simulated and the results are compared directly. The study shows that in terms of sporting performance around a theoretical road circuit, the adaptive model outperforms both the standard vehicle and fixed configuration models by a small degree, +-2.3%. The standard vehicle is found to have a lift coefficient CL=0.43 with a drag coefficient of Cd=0.31. The dynamic model is able to realize combinations of low drag or low lift between the limits of Cd=0.3, CL=0.34 and Cd=0.32, CL=0.03. The variable aerodynamic properties allow for a 5.5% increase in maximum cornering speed and a 20% improvement in acceleration time from standstill to terminal speed. The percentage improved lap time would be greater if the effects of breaking from the higher terminal speed achieved by the dynamic model were ignored for the simulation...