Cavity flow induces strong flow oscillations, which increase noise, drag, vibration, and structural fatigue. This type of flow impacts a wide range of low speed applications, such as aircraft wheel wells, ground transportations, and pipelines. The objective of the current study is to examine the reverse flow interaction inside the cavity, which has a significant impact on the cavity flow oscillations. The study also investigates the impact of steady jets with different-configurations on the time-average field and the oscillations of the cavity separated shear layer. The purpose of the steady jets is suppressing the oscillations of the cavity separated shear layer. The experiments were performed for an open cavity with L/D = 4 at Reθ between 1.28×103 to 4.37×103. The steady jets were applied with different: momentum fluxes (J = 0.11 kg/m.s2,0.44 kg/m.s2 and 0.96 kg/m.s2), slot configurations (sharp edge and coanda), and blowing locations (blowing from the cavity leading and trailing edges). The data were acquired using qualitative (surface oil flow visualisation) and quantitative (hot-wire anemometry, laser Doppler anemometry, particle image velocimetry, and pressure measurements) flow diagnostics techniques. The study found that a low-frequency instability dominates the velocity spectra of the cavity separated shear layer. This instability decreases with increasing Reθ and is related to the reverse flow interaction. This interaction takes place when the reverse flow influences the sensitive separation point of the cavity separated shear layer. As a result, a large amplitude flapping wave is generated and propagates downstream of the cavity separated shear. It was also revealed that increasing J for the leading and trailing edges blowing enhances the reverse flow interaction and increases the broadband level of the unsteady wall pressure spectra. Thus, these types of jet blowing are not suitable for controlling the oscillations of the cavity separated shear layer.

Automotive manufacturers are receiving pressure from customers and regulators to reduce emissions. Reducing the weight of the vehicle through the use of carbon fibre is seen as one of these mechanisms. The challenge is to develop suitable manufacturing processes that can offer appropriate cycle times to meet demand and deliver materials with adequate mechanical properties for structural applications. Compression moulding of discontinuous fibre moulding compounds with local continuous fibre inserts provide better production rates and part complexity compared to the autoclave components and higher performances than injection moulding. However, combining a unidirectional carbon fibre (UD) material with a random short fibre orientation sheet moulding compound (SMC) that flows heterogeneously will lead to degradation in the properties of the continuous reinforcement. This work aims to demonstrate a hybrid of continuous and discontinuous fibre compounds in a single moulding operation with increased stiffness and determine if the surface distortion of the reinforcement can be used to predict local stiffness. A benchmarking study was carried out with UD and the SMC followed by hybridisation. This was non-destructively tested for flexural moduli providing a localised map of stiffness which was compared with a theoretical value. This work demonstrated that simply placing unidirectional (UD) prepreg with the SMC caused significant distortion and migration of the reinforcement in a one-dimensional flow scenario. Resin tended to bleed out of the hybrid reinforcement, causing a resin rich area at the UD ply drop off point. This resin bleed was more prominent at the ends of the UD fibres. The resin system in the UD was staged by partially curing it to a controlled level through the measurement of the storage modulus, and showed that flow could be dramatically reduced. This was determined by rheology and inter-laminar shear tests to measure material degradation from staging to improve flow control. It was found that for flow control of the reinforcement staging beyond gelation was required. The inter-laminar shear strength of UD is significantly higher than the SMC, and found that even with 50% staging properties were still higher. Where there were high levels of flow resistance in compression moulding, staged hybrids resulted in to two moulding defects; a dry region on the SMC under the reinforcement and rippling outside the reinforcement, which reduced the stiffness by nearly 50% in the affected areas. Staging accompanied with charge layout design of the UD to 902/0 showed markedly reduced flow in one, two and three dimensional scenarios, almost completely resisting the flow of the SMC. In the 2D flow scenario where the SMC charge coverage was 60% compared to the manufacturers’ recommended 80%, flow was limited to 3% and the stiffness could be locally predicted to an accuracy of 16%. By controlling the level of staging and careful consideration of the charge design, hybrid components can be manufactured repeatedly with increased accuracy in stiffness prediction and demonstrated an improved flexural strength and modulus increase of >44%, increasing the potential use to a wider range of complex geometry structural applications.

With the growth of electrical power onboard aircraft, the interaction between the electrical systems and the engine will become significant. Moreover, since the drivetrain has a flexible shaft, higher load connections can excite torsional vibrations on the aircraft drivetrain. These vibrations can break the shaft if the torque induced is higher than the designed value, or reduce its lifespan if the excitation is constant. To avoid these problems, the electromechanical interaction between the electrical power system and the drivetrain must be evaluated. Past studies have identified the electromechanical interaction and introduced experimental setups that allow its study. However, strategies to reduce the excitation of the torsional vibrations have not been presented. This thesis aims to analyse the electromechanical interaction in aircraft systems and develop an advanced electrical power management system (PMS) to mitigate its effects. The PMS introduces strategies based on the load timing requirements, which are built on the open loop Posicast compensator. The strategies referred as Single Level Multi-edge Switching Loads (SLME), Multilevel Loading (MLL), and Multi-load Single Level Multi-edge Switching Loads (MSLME) are applied to different loads, such as pulsating loads, ice protection system, and time-critical loads, such as the control surfaces. The Posicast based strategies, eliminate the torsional vibrations after a switching event, by the addition of zeros that cancel the poles of the system. For this reason, the knowledge of the natural frequencies of the mechanical system is necessary. Experimentally, the system parameters are obtained through Fourier analysis of the step response and the strategies are applied. A robust analysis of the strategies allows the establishment of the range of uncertainty on the frequencies that allow the proper operation of the strategies. Simulation and experimental results show that the torsional vibrations can be reduced to values close to zero by the application of the strategy. Therefore, the PMS mitigates the electromechanical interaction between the electrical power system and the aircraft drivetrain.

Advanced Receiver Autonomous Integrity Monitoring (ARAIM) is a new Aircraft Based Augmentation System (ABAS) technique, firstly presented in the two reports of the GNSS Evolutionary Architecture Study (GEAS). The ARAIM technique offers the opportunity to enable GNSS receivers to serve as a primary means of navigation, worldwide, for precision approach down to LPV-200 operation, while at the same time potentially reducing the support which has to be provided by Ground and Satellite Based Augmented Systems (GBAS and SBAS). Previous work analysed ARAIM performance, clearly showing the potential of this new architectures to provide the Required Navigation Performance down to LPV 200 approach procedures. However, almost all of the studies have been performed with respect to fixed points on a grid on the Earth’s surface, with full view of the sky, evaluating ARAIM performance from a geometrical point of view and using nominal performance in simulated scenarios which last several days. Though, the operational configuration was not examined; attitude changes from manoeuvres, obscuration by the aircraft body and shadowing from the surrounding environment could all affect the incoming signal from the GNSS constellations, leading to configurations that could adversely affect the real performance. In this research, ARAIM performances in simulated operational configurations are presented. Four different algorithms were developed that integrate the ARAIM technique for performance prediction analysis. These algorithms could usefully be implemented: • In the design of instrument approach procedures. The algorithms could be used to improve the procedure of the development of new instrument approaches, reducing time, effort and costs. • In the aircraft Flight Management Systems. The algorithms could support the pilots in the pre-flight briefing, highlighting possible integrity outage in advance and allowing them to select a different approach or making them aware of the need to utilise additional positioning systems. Increased awareness and better pre-flight planning could ultimately improve the safety of flights and contribute to the safe introduction of GNSS as a viable positioning method for instrument approach. The results showed that the aircraft attitude and the surrounding environment affect the performance of the ARAIM algorithm; each satellite lost generates a peak in the performance parameters that depends on the total number of satellites in view, their relative geometry and on the number of satellites lost at the same time. The main outcome of this research is the identification that the ideal scenario would be to have a tri-constellation system that provides at the same time high redundancy, reliability and increased safety margin.

Daylight changes from moment to moment, in brightness, colour and direction under changing bright daylight, in-vehicle displays can become unreadable due to washout or glare, causing driver distraction or masking safety critical information. With an increasing number of vehicle systems being controlled through a centralised display, the legibility of automotive displays under ambient lighting conditions has become an important consideration for engineers in terms of perceived quality, safety and driver distraction. Due to the dynamic nature of the sky, testing under natural daylight would not give the control required for meaningful measurements. Therefore, the challenge for the automotive industry is to standardise the simulation of illumination for performing assessments and to make the process controlled, repeatable and comparable to real daylight situations. The main objective of this project is to propose a method for recreating a daylight-comparable lighting environment to enable the evaluation of vehicle interiors under high ambient lighting conditions and to propose best-practice for illumination used in legibility evaluation for design and validation activities. This is achieved with a measurement and simulation approach, to evaluate current procedures and determine the gap between real world, simulation and lab-based assessments, and bring them closer to the real-world. There are two main outputs from this project; a comparative simulation study which verifies digital tools for use by JLR in display design and evaluation activities, and the recommendation to align physical and digital methods to move evaluations earlier in the new product development process. A concept has been included to enable controlled measurements as part of physical evaluations, as are the critical factors required for a repeatable physical environment for physical testing as the basis of continuous improvement of digital simulations.

Vehicle electrification is a technology pathway being adopted by original equipment manufacturers (OEMs) to either reduce or eliminate tailpipe emissions. However, electric vehicles (EV’s) that employ a rechargeable energy storage system (RESS) still face significant barriers within the marketplace when compared to incumbent internal combustion engine (ICE) vehicle technology. One of these barriers is ensuring that the RESS lasts the life of the product or maintains customer satisfactory performance over a warranted life (such as 10 years or 100,000 miles of customer usage). There has been comparably little published research critically examining the effect of vibration on high voltage (HV) batteries within battery electric vehicles (BEV) and hybrid electric vehicles (HEV). Subsequently the effects of vibration on RESS components and subsystems are potentially a major cause of in market durability failures. The following thesis presents the findings from an International Engineering Doctorate (EngD (int.)) investigating factors influencing the vibration durability of HV batteries and components. This research programme has the objective of providing the underpinning knowledge that allows manufacturers to improve the mechanical durability and performance of EV battery assemblies with respect to vibration. This objective has been achieved through several novel studies within three primary areas of investigation. Firstly, the research focused on defining the “in-service” vibration environment of BEV components and assemblies through the analysis of vibration measurements from contemporary BEVs. This study was the first to synthesise a vibration profile that is representative of a durability life of 100,000 miles of UK customer usage from multiple real world BEV measurements. The presented profile can be employed by academics and engineers to underpin future vibration durability assessments of BEV battery components. The second avenue of investigation was to characterise the natural vibration and modal response of EV components and assemblies. This was to determine their susceptibility to vibration excitation, as identified from measurements of the in-service environment. It was also the first of its kind to fully characterise the natural vibration characteristics and mode shapes of lithium-ion pouch cells via modal analysis techniques. The final objective was to determine the durability behaviour of EV components and assemblies, by subjecting them to vibration, via state of the art single and multi-axis test techniques, which were the equivalent of a typical vehicle life (10 years) or customer mileage (100,000 miles). As well as defining the degradation characteristics of a contemporary BEV module and multiple EV cells, the impact of packaging variation and state of charge (SOC) on cell ageing was also determined. In conclusion, this research thesis defines innovative testing techniques and characterisation data, which can be employed by engineers to predict the warranty performance, with respect to the effects of in-service vibration, of future EV battery assemblies.

No description available.

With the increasing development of Additive Manufacturing technologies in the past two decades, the area of lattice structures has received considerable attention due to their inherent advantages in providing lightweight, high stiffness, and strong materials. However, this comes with new challenges such as geometry modelling, optimal selection of unit cell for certain loading condition, and mechanical performance for practical applications. This research provides a systematic investigation of lattice structures from design, testing, to numerical investigation and analytical study, as well as a case study for practical engineering application. A new method to create lattice structures using the traditional CAD package was proposed. It can automatically generate parametric models of complex lattice structures. Three lattice structures with triangular unit cells, cubic unit cells and hexagonal unit cells are shaped by side length, L, strut thickness, t, and height, h (or layer number, n, in h direction). The prototypes manufactured from Nylon and AlSi10Mg show good manufacturability. The experimental tensile curves of the lattice structures reveal distinguished results from the traditional solid materials. The triangular lattice structure was found to be the best in terms of greater effective Young’s modulus (E*) and stiffness-to-mass ratio. The theoretical solution of E*for triangular lattice structure (E*EB) was derived based on Euler-Bernoulli beam theory. The numerical results of E*by using a representative volume element were obtained by Finite Element Analysis (FEA). The effects of L, t and h, on values of E* were investigated independently. The results show that t had the most significant effect. Values of E* obtained by the proposed analytical solution have shown the best agreement with the corresponding FEA results when compared with other existing methods. The experimentally determined values of E* are in excellent agreement with both analytical and numerical solutions. A new single part vehicle suspension with lattice structure was created using Creo®. As the lattice structure suspension is made of scale unit cells shaped by several parameters, it is time-consuming to run simulation with this model. Instead, solid suspension with E* of triangular lattice structure determined by the proposed analytical solution was used in FEA. The optimization method by Design of Experiments (DOE) was used to develop the formulae among design variables (L, t, h and T) and maximum von Mises stress, maximum deformation, stiffness-to-mass ratio and total mass. This method has proven to be an effective way to obtain the mechanical response of large scale lattice structures. The optimum parameters [T, t, L, n] are [2.90, 1.90, 7.82, 1] for the objective of maximum stiffness-to-mass ratio, which is found to be a conservative design. For the objective of minimum total mass, the optimized values are [0.55, 0.76, 4.88, 1], where the design can make full use of structure materials. In the future, these two different lightweight methods should be considered along with other requirements, such as vibration performance and failure behaviour.

As the energy and environment crisis increase severely, developing cleaner and more fuel efficient vehicles have become a research hot spot of automobile industry. In recent years HEV (hybrid electric vehicle) and EV (electric vehicle) are widely considered as two of the most viable solutions to the world’s need for cleaner and more fuel-efficient vehicles. This project aims to further improve the performance and fuel efficiency of EVs/HEVs for real application of urban driving. The thesis can be divided in to two major studies: EMB (Electro-Mechanical Brake) system development and HEV power management, which are two hot topics in the latest researches of EVs/HEVs. The brake system plays an important role in vehicles. As the X-by-wire technology develops, EMB can realize individual control of braking force on each wheel; which makes it very suitable for electrified vehicles. In this thesis a compact design of EMB actuator is proposed. To investigate the control of EMB system, a down scaled EMB test rig has been set up and an EMB motor control system has been developed. In the section of clamping force control of EMB system, in order to achieve fully control of braking force, a low cost sensor less clamping force control method is proposed. It is noted that in real applications of EVs/HEVs the EMB system is normally cooperated with regenerative braking system during braking process, in this thesis the co-operative control of hybrid brake system is investigated as well to improve the braking performance and regenerative braking efficiency. In order to overcome the drawbacks of the conventional gasoline vehicles, HEVs encompass two power sources (internal combustion engine and electric motor) to drive the vehicle. Due to existence of the double power sources, HEVs normally have multiple operation modes. The objective of HEV power management is to find the optimal power distribution on each power source to meet the power requirement with minimum fuel consumption. In this thesis to improve the fuel efficiency and keep the balance of battery SOC (state of charge) simultaneously during urban driving, a revised dynamic programming (DP)-optimized HEV power management control strategy is proposed. The DP algorithm is applied to obtain the optimal engine/motor power distribution and utilized for the design of the fuzzy control strategy. The traditional DP algorithm is modified with the consideration of SOC balance for HEVs. In the analysis of DP simulation results, rules of torque slip behaviors have been found, which are directly utilized in the design of fuzzy control strategy. In order to improve the practicality of the control strategy to meet the diversities of city driving patterns, an urban driving pattern recognition method is presented. To evaluate the control performance, the proposed control strategy is also compared with the conventional rule-based strategy. The simulation results indicate that by adopting the proposed strategy the fuel efficiency of HEV is improved, and the SOC of the battery is kept in balance during different urban driving cycles.

Drivers must communicate with other road users to make their intentions clear, thereby enhancing the quality of the driving experience, improving safety on the roads and avoiding accidents. This interaction can be made either formally using legal signals approved by legislative bodies (e.g. use of indicators), or informally (e.g. hand gestures). However, this informal interaction may not be clearly understood by all drivers, and may lead to stress, strong emotional responses or aggressive driving behaviour. Moreover, a single informal interaction, e.g. flashing the headlights, can have several different meanings such as “Your headlights are on”, “Thank you”, or “I want to overtake you”, depending on the situation. Driver interaction could be enhanced by an electronic driver-to-driver communication device (DDCD), which would allow motorists to exchange messages with each other. The technology associated with connected vehicles could be used for the design of this communication device. For example, wireless devices and sensors already allow vehicles to exchange information with other vehicles (V2V) and road infrastructure (V2I) at any time. This PhD research initially introduces a driver-to-driver communication framework depicting a set of variables or factors that have a decisive effect on the communication process. The framework is also comprised of a task analysis for the DDCD. The framework is later expanded to include a specific set of design recommendations linked back to the variables that affect the communication process. These recommendations are specifically related to the DDCD and are based on a review of the literature and results from empirical studies conducted as part of the PhD. A mixed-methods approach was adopted in this research to elicit opinions and attitudes of drivers, including interviews, observations, a workshop with academic experts and questionnaires. In total, five studies are described in the thesis, with STUDY A being an exploratory investigation on the feasibility of the DDCD. The second and third studies focused specifically on the task of receiving messages, with academic experts (STUDY B) and with regular drivers (STUDY C). A fourth study (STUDY D) involved on-road trials to investigate how drivers would identify a vehicle to send a message to. The final experiment (STUDY E) consisted of an evaluation in a driving simulator of a low-fidelity prototype of the communication device to send messages. The studies were based on a set of driving communication scenarios, which facilitated the exploration of potential issues with the use of a proposed technology before implementation. The scenarios represented different examples of how, why and when drivers might communicate with one another, and were used as the focal point with study participants. The findings from this research indicate that drivers would be willing to use an electronic communication device in situations directly related to the road context in which there is a decisive effect on their safety or that may alter their driving behaviour, such as a problem with their vehicle or a hazard on the road. There are many factors investigated in this research that have a significant effect on drivers’ communication process. These factors include, but are not limited to, time criticality, trust issues in message content, the effect of passengers, sender anonymity and the general purpose of communication. These research findings will significantly contribute to the limited academic research currently available on social and connected vehicles and can also provide invaluable information for the automotive industry.