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Posted: Nov 19, 2013
Greener engine designs from advanced predictive tools
(Nanowerk News) The development of combustion engines is under increasingly stringent constraints with regard to fuel efficiency and emissions. Advanced modelling tools developed with EU support will help meet performance objectives starting from the early phases of design.
Several novel engines have the potential to alleviate problems associated with conventional combustion. However, all of these technologies are plagued by cycle-to-cycle or cyclic combustion variability (CCV) that limits their performance. Detailed knowledge of the factors and operating regimes leading to CCV for specific engine types was previously lacking. Scientists working on the EU-funded LESSCCV project decided to fill the gap by exploiting recent advances in complex design tools using computational fluid dynamics (CFD).
The consortium developed multi-scale CFD tools capable of simulating the entire engine, including the combustion chamber, as well as intake and exhaust ducts. The tools couple one-dimensional (1D) CFD codes describing flow in the intake and exhaust lines with 3D CFD codes (large eddy simulations (LESs)). This will account for turbulent interactions and combustion inside the combustion chamber or cylinder.
Tools were applied to the study of CCV in three types of gasoline engine, generating a wealth of complex data for further analysis. Scientists were able to validate the model by comparing outcomes with experimental data and identified the main causes of CCV in each of the engine types. Enhanced understanding of CCV led to the formulation of novel and less computationally-intensive (reduced CCV) models equally capable of predicting behaviours. Case studies on engines and vehicles highlighted ways in which novel designs could reduce CCV and increase efficiency.
Exploitation of LESSCCV tools and results is expected to contribute significantly to short-term goals of more efficient and greener combustion engines for the transport sector. The predictive design tools will not only reduce the environmental impact of transportation but also enhance the competitiveness of EU engine manufacturers.