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Large eddy simulation techniques to simulate and c ontrol by design cyclic variability in otto cycle engines

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Improved transport sustainability

The PRISM algorithm was developed to allow reliable chemistry modelling of engine flows with unprecedented gains in computing time.

Climate Change and Environment

Aiming to reduce green house gases and other pollutants emitted by automobiles, the LESSCO2 project focused on unsteady engine operation in Otto cycle internal combustion engines. Effective control of the cyclic variability in these engines can result in improvements in engine efficiency and pollutant emissions. Furthermore, cycle to cycle variations are considered responsible for limiting the operation range of novel concepts, such as Controlled Auto-Ignition (CAI) engines. Due to lack of suitable three-dimensional Computer Fluid Dynamic (CFD) tools unsteady engine phenomena have not been extensively explored. Urged by this the LESSCO2 project developed an innovative engine design tool for unsteady engine operation. The tool enables prediction of the effects of this operation on the energy conversion efficiency and the related pollutant emissions. More specifically, researchers adopted the Large Eddy Simulation (LES) technique to include unsteady effects in the combustion chamber of engines. One of the key project results involved the integration of realistic auto-ignition chemistry into three dimensional CFD simulations. The PRISM algorithm offers 'intelligent' and fast chemistry tabulation by coupling automatic mechanism reduction with solution mapping. The method has been successfully implemented into a simple stochastic reactor model for engine knock simulation using a kinetic mechanism for mixtures of n-heptane and iso-octane. For further information on the project work, click at: http://project.ifp.fr/lessco2

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Climate Change and Environment

2 April 2014