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The purpose of this study is to present a parametric fuel tank filling model from first principles. The aim is to build a tool that can help with the initial tank layout, to make sure the design does not promote premature shut off. The governing equations of the model are detailed and results for a test case are presented. The model is based on a common set of parameters enabling it to be adapted to a set of design constrains. Additionally, the model is validated by experimental data where available and a sensitivity analysis on critical design parameters that promote premature shut off is performed.

The flow field and body aerodynamic loads on the DrivAer reference model have been extensively investigated since its introduction in 2012. However, there is a relative lack of information relating to the models wake development resulting from the different rear-body configurations, particularly in the far-field. Given current interest in the aerodynamic interaction between two or more vehicles, the results from a preliminary CFD study are presented to address the development of the wake from the Fastback, Notchback, and Estateback DrivAer configurations. The primary focus is on the differences in the far-field wake and simulations are assessed in the range up to three vehicle lengths downstream, at Reynolds and Mach numbers of 5.2×106 and 0.13, respectively. Wake development is modelled using the results from a Reynolds-Averaged Navier-Stokes (RANS) simulation within a computational mesh having nominally 1.0×107 cells.

Cooling drag, typically known as the difference in drag coefficient between open and closed cooling configurations, has traditionally proven to be a difficult flow phenomenon to predict using computational fluid dynamics. It was seen as an academic yardstick before the advent of grille shutter systems. However, their introduction has increased the need to accurately predict the drag of a vehicle in a variety of different cooling configurations during vehicle development. This currently represents one of the greatest predictive challenges to the automotive industry due to being the net effect of many flow field changes around the vehicle. A comprehensive study is presented in the paper to discuss the notion of defining cooling drag as a number and to explore its effect on three automotive models with different cooling drag deltas using the commercial CFD solvers; STARCCM+ and Exa PowerFLOW.

The interactions between automatic controls, physics, and driver is an important step towards highly automated driving. This study investigates the dynamical interactions between human-selected driving modes, vehicle controller and physical plant parameters, to determine how to optimally adapt powertrain control to different human-like driving requirements. A cyber-physical system (CPS) based framework is proposed for co-design optimization of the physical plant parameters and controller variables for an electric powertrain, in view of vehicle’s dynamic performance, ride comfort, and energy efficiency under different driving modes. System structure, performance requirements and constraints, optimization goals and methodology are investigated. Intelligent powertrain control algorithms are synthesized for three driving modes, namely sport, eco, and normal modes, with appropriate protocol selections. The performance exploration methodology is presented.

The quantitative assessment and comparison of different hybrid vehicle options has traditionally been done on the basis of measuring or estimating the vehicle's fuel economy over predefined drive-cycles. In general, little or no consideration has been given to the more subjective and difficult to quantify vehicle requirements, such as trying to understand which derivative will be the most “fun” vehicle to drive. A lack of understanding in this area of vehicle performance sufficiently early within the development life-cycle so as to be in a position to influence the vehicle design, can lead to a compromised powertrain architecture which will ultimately increase the risk of product failure. The work presented within this paper constitutes part of the overall design activities associated with the LIFECar programme. The aim of the LIFECar consortium is to manufacture a lightweight, fuel cell hybrid electric sports vehicle.

In this paper, gear ratios of a two-speed transmission system are optimized for an electric passenger car. Quasi static system models, including the vehicle model, the motor, the battery, the transmission system, and drive cycles are established in MATLAB/Simulink at first. Specifically, since the regenerative braking capability of the motor is affected by the SoC of battery and motors torque limitation in real time, the dynamical variation of the regenerative brake efficiency is considered in this study. To obtain the optimal gear ratios, iterations are carried out through Nelder-Mead algorithm under constraints in MATLAB/Simulink. During the optimization process, the motor efficiency is observed along with the drive cycle, and the gear shift strategy is determined based on the vehicle velocity and acceleration demand. Simulation results show that the electric motor works in a relative high efficiency range during the whole drive cycle.

Simulations are presented which fully couple both the aerodynamics and cooling flow for a model of a fully engineered production saloon car (Jaguar XJ) with a two-tier cooling pack. This allows for the investigation of the overall aerodynamic impact of the under-hood cooling flow, which is difficult to predict experimentally. The simulations use a 100 million-element mesh, surface wrapped and solved to convergence using a commercially available RANS solver (STARCCM+). The methodology employs representative boundary conditions, such as rotating wheels and a moving ground plane. A review is provided of the effect of cooling flows on the vehicle aerodynamics, compared to published data, which suggest cooling flow accounts for 26 drag counts (0.026 Cd). Further, a sensitivity analysis of the pressure drop curves used in the porous media model of the heat exchangers is made, allowing for an initial understanding of the effect on the overall aerodynamics.

The aerodynamic drag of future low emission vehicles will need to be low. Unfortunately, vehicle shapes that result in low drag coefficients - of the order of 0.15 - are often aerodynamically unstable in crosswinds. The addition of wheels, transmission, radiators, suspension, steering, brakes, air ducts and wing mirrors can easily increase this drag coefficient to 0.24 and above and produce an undesirable lift distribution. The Aero-Stable Carbon Car (ASCC) is a research project, in conjunction with industrial partners, to design and build a practical 3 to 4 seat low drag car (CD less than 0.20) with an acceptable lift distribution (front to rear) which is also stable in crosswinds and in yaw through a series of low speed wind tunnel tests performed in the Cranfield College of Aeronautics 8′ × 6′ wind tunnel facility.

A mild hybrid powertrain with crankshaft mounted integrated motor generator (IMG) and torque controlled infinitely variable transmission (IVT) has shown clear potential for fuel economy (FE) enhancement. It also makes significant driveability and performance improvements possible which are a condition for customer satisfaction and subsequent marketability. The hybrid powertrain supervisory control strategy presented here uses the energy recovered during braking events for power assist, hence improving FE and driveability compromises. This is achieved by operating the engine at its best brake specific fuel consumption (BSFC) point during steady state conditions without deteriorating the transient response as a result of the comparatively fast IMG torque response. This paper demonstrates the launch manoeuvre and general driveability improvements achieved in simulation with validated models.

In jet atomization, breakup length is the length of the continuous jet segment, before its breakup to discontinuous droplets. Hydrodynamic instability theory, implemented in CFD codes, is often complemented by semi-empirical correlations for breakup length, which may limit parametric investigations. A basic mechanistic approach to the breakup length prediction, based on a simple momentum balance between the injected jet and the aerodynamic drag force due to the surrounding gas, which complements the classic hydrodynamic instability breakup mechanism, is suggested. This model offers a simple complementing mechanistic model. It is shown that obtained results compare well with published experiments, and with the established empirical correlation of Wu and Faeth (1995). A simplified version of the model, taking into account an inviscid hydrodynamic model is shown to maintain plausibility of breakup length predictions in fuel-injection relevant conditions.

The theory of liquid fuel jet instabilities has been developed under several assumptions, which include the assumption that the jets breakup processes are isothermal. However, liquid fuels are normally injected into an elevated combustion-chamber temperature to maintain a desirable homogeneous combustible mixture - liquid vapour and air. Therefore, a new linear theory model is developed for the instability and breakup of non-isothermal liquid jets, with consideration of a spatially variation of surface tension along the liquid-gas interface. The spatial variation of surface tension is obtained through temperature-dependent surface tension and transient heat-transfer from the combusting gases to the liquid jet. The classical interface hydrodynamic breakup theory and solution of heat-transfer through semi-infinite medium are coupled through the surface tension gradient. The analytical model accounts for the non-isothermal effects on jet breakup.

Considerable engineering effort is now being applied to the design and development of Soapboxes entered in the Goodwood Festival of Speed Gravity Challenge. With average speeds of 18 ms-1 (40 mph) from a standing start along the 0.7 mile course and maximum speeds of around 27 ms-1 (60 mph), the aerodynamic contribution to performance is significant. This paper discusses the aerodynamic considerations given to the design of the leading Soapboxes and to the racing conditions experienced. Analysis and test techniques which may also be employed are also described.

A modern benchmark for passenger cars - DrivAer model - has provided significant contributions to aerodynamics-related topics in automotive engineering, where three categories of passenger cars have been successfully represented. However, a reference model for high-performance car configurations has not been considered appropriately yet. Technical knowledge in motorsport is also restricted due to competitiveness in performance, reputation and commercial gains. The consequence is a shortage of open-access material to be used as technical references for either motorsport community or academic research purposes. In this paper, a parametric assessment of race car aerodynamic devices are presented into four groups of studies. These are: (i) forebody strakes (dive planes), (ii) front bumper splitter, (iii) rear-end spoiler, and (iv) underbody diffuser.

In automotive aerodynamics much use has been made of generic reference models for research and correlation. Research work has been conducted mostly on small-scale versions of the models to investigate flow regimes and aerodynamic force and moment characteristics while correlation tests have made use of full-scale models to compare results between wind tunnels. More recently reference geometries have also been used as test cases in the validation of computational techniques. This paper reviews the design characteristics and use of several key reference models. The advantages and disadvantages of these designs and also the applicability of the results in providing guidelines for the development of production vehicles are discussed. It is advocated that when researchers choose to use simple models, existing reference geometries should be employed.

This paper gives an overview of the development of a number of loss models for the pushing metal V-belt CVT. These were validated using a range of experimental data collected from two test rigs. There are several contributions to the torque losses and new models have been developed that are based upon relative motion between belt components and pulley deflections. Belt slip models will be proposed based upon published theory, expanded to take account of new findings from this work. The paper introduces a number of proposals to improve the efficiency of the transmission based on redesign of the belt geometry and other techniques to reduce frictional losses between components. These proposed efficiency improvements have been modelled and substituted into a complete vehicle simulation to show improvements in vehicle fuel economy over a standard European drive cycle.

The simulation of heat exchanger air flow characteristics in a sub-scale wind tunnel test requires an accurate representation of the full-scale pressure drop across the element. In practice this is normally achieved using laminations of various porous materials and honeycombs on the basis of experience and ad hoc data. In view of this, a series of measurements of the pressure drop, in both the near and far field, across screens with porosity (β) in the range 0.41 ≺ β ≺ 0.76 are reported. The aim being to establish a relationship between the porosity and the pressure drop characteristics of a given material at various angles of inclination to the free-stream flow. Furthermore, the effect of screen depth was investigated using honeycombs. This data will facilitate detailed design and accurate representation of the flow characteristics at sub scale.

A 3D Navier-Stokes CFD model of a wheel located within a wheelhouse cavity has been produced. Both a stationary wheel on a fixed ground and a rotating wheel on a moving ground were considered. Extensive comparisons with the results of a wind tunnel investigation based on the same geometry are presented. These consist of three force coefficients and pressures on the internal faces of the cavity. Comparison with the experimental results gave encouraging agreement. It was found that the rotating wheel produced more drag than the stationary wheel whilst shroud drag decreased when the groundplane was moving compared to when it was stationary.

The effect of local fuel concentration on cyclic variability in combustion and engine performance in a lean burn stratified charge engine has been investigated. The fuel concentration in a plane close to the spark plug was measured for a large number of cycles using laser-induced fluorescence (LIF) and simultaneous measurement of in-cylinder pressure in an one-cylinder optical research engine. It could be shown quantitatively that the fuel concentration in a small region close to the spark plug has a dominating effect on the subsequent pressure development for lean mixtures. Variations in the mixture concentration in the vicinity of the spark plug contribute significantly to cyclic variation in combustion. Measurement of the flame area in the same plane 20 °CA after ignition revealed that the direction of growth of the established flame is not significantly influenced by the stoichiometry.

The rise of autonomous technologies may reflect on new vehicle traffic characteristics, likely reducing vehicle-to-vehicle proximity and emerging platooning formations. Energy consumption, stability, and surface contamination are relevant factors that are sensitive to aerodynamic interference while platooning. From the experimental perspective, most wind tunnels were originally designed to host isolated models, and these constraints often limit the investigation of multiple full-body vehicle formations (e.g. test section length, moving ground dimensions, standard testing points). This paper introduces the ‘MultiWake’ model - a parametric bluff-body device based on a morphing concept, which can emulate the aerodynamic wake characteristics of different vehicle classes.

Transient force and surface pressure data has been measured on a range of simple geometric shapes in order to gain an understanding of the complex time dependent and separated flow around a vehicle when subjected to a crosswind. The experiments were carried out using the Cranfield University model crosswind facility. It is found that the leeward face is the dominant area of transient activity. Maximum and minimum peak yawing moments at gust entry and exit are compared