MODELLING AND SIMULATION
The team started with a conceptual design of a cooling channel with different configurations. Then, Lucid’s engineers carried out a series of design evaluations and sensitivity analysis using a fully- parametric CFD model with modeFrontier. This optimised the design in terms of
temperature reduction, lowering pressure and minimising the channel size. After deciding on an optimum channel solution, the manifold design was further optimised by including a mesh-morphing step in the modeFrontier process integration workflow. ‘The objectives were to keep pressure variations low and reduce velocity variation,’ Moseley added. The use of modeFrontier enabled Lucid engineers to make more power available to the inverter and increase AC from 1,200 to 1,500A. Such increased efficiencies have a knock-on effect for another core design consideration: the miniaturisation of the powertrain. The Lucid Air has an exterior volume similar to the Audi A6, but the interior is more like the space you would find in an Audi A8 L. Moseley explained: ‘For Lucid, one of the guiding design principles is to optimise the space the occupant sits in, where we want to shrink everything back within the powertrain to give space back to the occupant.’ Moseley said: ‘We are using these
as that rotor is spinning, there are also mechanical demands to take into account. Energy is also dissipated, so you have to ensure you can remove heat or counteract its effects in the wider system. So, we have a thermal challenge too. Plus, the material properties of the rotor will change as the temperature changes. Moseley said: ‘All these different
problems are traditionally dealt with by different analysts but, in reality, they are a simultaneous problem and so that requires multiphysics analysis. That’s a big shift in thinking and it’s also a challenge as to how to get the right expertise to solve that complex problem.’ Lucid Motors recently optimised the design of an inverter, an electronic device that converts direct current (DC) stored in the battery into alternating current (AC) before sending that electricity to the three phases of the AC induction motors. Overheating presented the most
critical issue, plus the effects of vibration, humidity and dust, when designing it. A low chip-to-coolant thermal conductivity together with a temperature balance and low pumping pressure had to be achieved to improve the component’s efficiency. So, the Lucid Motors team focused on designing an inverter cooling system to keep the temperature under control.
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techniques to drive the miniaturisation of the powertrain to unlock space to improve the user experience of the vehicle. It’s like a TARDIS experience. On the outside it looks like a normal vehicle but on the inside it is bigger than you would expect.’ ‘We are becoming a more urbanised
world and to try and base our transport system on larger vehicles is impossible. The role of electric powertrains is very important to make the urban space more palatable and the drive experience better,’ Moseley added.
While simulation is useful at many
”We can get a solution that is better in performance than a human could achieve with a purely holistic approach [but] this requires high investment in the right engineers and the right analysis capability”
stages of electric vehicle development, it is particularly beneficial in arriving at an overall vehicle design, where such miniaturisation can be achieved. Walker said: ‘Designers will be thinking about how to size the components on the vehicle to achieve overall performance and range targets. It is not practical to build prototype vehicles to answer questions such as “what size battery do I need”, since the battery is so tightly integrated into the overall vehicle design. The choice has to be right from the outset and simulation is the only way to do this.’ Electric vehicles have certainly changed
the complexity of the design process compared to traditional vehicles, as Merceron explained: ‘Although they no longer have complex internal combustion engines, the architecture of electric drivetrains is much more integrated into the car. Different disciplines must work hand in hand now. For example, modifying the battery pack under the floor could change the vehicle’s crash resistance. So, electrical engineers now have to work much closer to body in white and safety engineers specifications.’
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The electric motor has come of age 200 years after the combustion engine was developed
October/November 2017 Scientific Computing World 27
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Altair Dassault
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