<p> This thesis focuses upon using a high-order finite-difference method on a structured overset grid to study flow features around a generic simplified car model adjusting mesh refinements, rear slant angles, solvers, and turbulence models. These processes are explored to develop a procedure for simulating more complex and realistic car models. Three different mesh refinements from 17 to 108 million vertices were tested with three different solvers (RANS, URANS, and DES) on an Ahmed body with a subcritical slant angle ascertain the optimum mesh parameters for subsequent simulations. Using a 57 x 10⁶ vertex mesh, multiple rear slant angles near the critical angle (30 degrees) were investigated with RANS and URANS approaches to compare drag, lift, and flow fields with experimental and CFD data found in literature. Similar trends were observed in CFD predictions and experimental data, including flow separation at the critical angle (30 degrees), but all predicted results were within 15% of experimental measurements for both time-averaged and unsteady simulations. At the sub-critical angle (25 degrees), CFD predictions using multiple hybrid RANS/LES approaches were compared against time-averaged and unsteady experimental measurements. These did not disagree with previous results and drag values were over predicted by a maximum of 4%, while lift values were under predicted by a maximum of 15% when compared to experimental results. Subsequent studies investigating elongated mesh refinement areas were inconclusive. The procedures outlined compare reasonably well to experimental data and can be used as a starting point for simulating more realistic models including complex dynamic pitch, heave, and roll simulations involving road vehicles.</p>

<p>The Formula SAE Electric competition is a collegiate autocross event in which teams design, build, and race an open-wheeled electric race car. The main motivation is the efficiency advantage of electric motors over internal combustion motors. This thesis presents the design and evaluation of two generations of Portland State University electric race cars. </p><p> The constraints are the competition rules, finances, human resources, and time required to complete a race car in one year. The design includes the implementation of existing components: battery cells, controllers, electric motors, drivetrains, and tire data for an optimized race car. Also, several circuits were designed and built to meet the rules, including the shutdown, precharge, discharge, brake system plausibility, tractive system active light, and an electric vehicle control unit. </p><p> The car&rsquo;s performance was modeled with calculations and OptimumLap simulation software, then track tested for actual data. Performance data such as torque, power, and temperatures were logged, and the Formula SAE events were tested. The data were compared to the simulations and records from past competitions, and the car was 21% to 30% behind the best times. </p><p> The motor generated 410 Nm of peak torque, as expected, but the maximum power was 51 kW, 15% less than the calculated 60 kW. Compared to the best times of past competitions, the car completed Skid-pad in 6.85 seconds (21% slower), and Acceleration in 5.65 seconds (25% slower). The first generation car was tested for range, and raced 31.4 km on a cold, wet track, so tire forces were decreased 6% to 69% from a dry track. During the 22 km Endurance test with the second generation car, there were problems with imbalanced cell voltages, limiting the test to 4.9 km. Later, there was a catastrophic drivetrain failure, and Endurance testing on a dry track was not completed. </p><p> In dynamic event simulations, a lighter, axial flux permanent magnet synchronous motor with a decreased counter EMF yielded improved times. Reconfiguring the battery pack from 200 <i>V_DC</i> 300 <i>V_DC</i> would provide 50% more peak power. Further testing is required to determine the actual average power use and making design decisions with an improved battery pack. </p>

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This work deals with the problem of determining the tire-road interaction forces for vehicle dynamic simulations. The work is an attempt to develope a numerical scheme that is universally applicable to all possible running conditions. The tire-road contact patch is approximated as a two-dimensional array of nodal points. Properties such as distribution of normal pressure, deflection and stresses over the contact patch are expressed as sets of the respective nodal values rather than analytical functions. Such a representation enables the treatment of any arbitrary, two-dimensional variation of contact patch properties. The representation of non-rectangular contact patch shapes and trapezoidal pressure distributions is also discussed. For steady state running conditions the performance of the scheme is compared with that of an existing analytical model. The applicability of the scheme to transient running conditions is also shown.

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Interest in hybrid electric vehicles (HEVs) and electric vehicles (EVs) has increased rapidly over recent years from both industrial and academic viewpoints due to increasing concerns about environmental pollution and global oil usage. In the automotive sector, huge efforts have been invested in vehicle technology to improve efficiency and reduce carbon emissions with, for example, hybrid and electric vehicles. This thesis focuses on one design area of these vehicles – the transmission – with the aim of investigating the potential benefits of improved transmissions for HEVs and EVs. For HEVs, a novel transmission developed by Nexxtdrive based on a twin epicyclic design is analysed using a matrix method and its performance is compared with the more common single epicyclic arrangement used successfully in the Toyota Prius. Simulation models are then used to compare the performance of a typical HEV passenger car fitted with these two transmissions over standard driving cycles. The conclusion is that the twin epicyclic offers substantial improvements of up to 20% reduction in energy consumption, though the benefits are sensitive to the driving cycle used. For EVs, most designs to date have used a single fixed ratio transmission, and surprisingly little research has explored whether multi-geared transmissions offer any benefits. The research challenge is whether it is possible to optimise the usage of the electric motor in its region of high efficiency by controlling the transmission. Simulation results of two EV examples confirm that energy consumption benefits are indeed achievable – of between 7 and 14% depending on the driving cycle. Overall, the original aspects of this work – the analysis and modelling the twin epicyclic gearbox; the analysis and modelling the twin epicyclic system in a vehicle and a comparison of the results with single epicyclic system; and the analysis and modelling of EVs with and without a transmission system of varying levels of complexity – have shown that there are worthwhile performance benefits from using improved transmission designs for low carbon vehicles.