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modelling and engineering Simulation shifts gear


In the drive for efficiency, simulation is the key to powertrain design, as


Warren Clark discovers


T


he pressure on vehicle manufacturers to deliver cheaper and more efficient cars intensifies


year on year. Concerns about global pollution have led to ever-changing rules and regulations to reduce vehicle emissions and improve fuel efficiency. Manufacturers are having to respond rapidly and constantly – and oſten there is significant variation between geographical territories. One significant government move has occurred in traffic-ridden Brazil, which has recently introduced an incentive scheme to encourage innovation in vehicle technology. Te Inovar-Auto scheme offers tax incentives to manufacturers who can demonstrate significantly reduced fuel consumption for vehicles manufactured between 2013 and 2017. ‘As regulations change, the


burden on engine designers is increased,’ says Frederick Ross, director of ground transportation at CD-adapco, whose Star-CCM+ soſtware is used by automotive suppliers worldwide. ‘Example of these changes can be reduced weight, downsizing of engines, reducing frictional losses in the engine. With all these changes, there is also demand for higher output. Designing vehicles with both higher output and lower weight engines is a difficult engineering challenge.’


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Altair OptiStruct is a modern structural analysis solver for powertrain durability and NVH analysis and optimisation A key tool in meeting these


challenges is simulation soſtware, and many different packages are used in powertrain design. Alongside finite element analysis for structural testing, an engineer might also turn to fluid dynamics to check the flow of oil, air or coolant around an engine, or combustion cycle analysis to assess the behaviour of fuel. Te way in which vehicle


manufacturers use simulation soſtware has evolved over time.


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‘Initially, we dealt mainly with stress analysis, for example, the stress on the intake/exhaust valves during operation,’ says Ross. ‘Computational fluid dynamics (CFD) for air flow and coolant flow was added to the mix around 20 years ago, looking at flow into the combustion chamber, plus the path of the coolant flow around the cylinders. Today, we are looking at simulating complete systems of components, including stress, thermal and flow in a


single simulation. Identification of thermal stresses is very important, and simulation helps to identify where potential cracks may occur within the engine structure, and guide the modification of the design accordingly. Oſten the worst thermal stresses occur under non-standard operating conditions, so our simulation tools need to be able to account for the full range of possible use scenarios.’ Te reasons why simulation


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Altair


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