Overview
This project researched simulation to predict cyclic combustion variability in gasoline engines.
The objective of LESSCCV was to exploit the recent possibilities of engine computational fluid dynamics ('CFD') tools to fundamentally improve the understanding of cyclic combustion variability ('CCV') in gasoline engines under real operating conditions, and to provide adequate modelling. Multi-scale CFD tools, able to study in detail the sources of CCV in full engines, was developed.
This was achieved by coupling 1D-CFD codes, describing the flow in the intake and exhaust lines as well as in the fuel injection system ('FIS'), with 3D-CFD codes using the innovative Large-Eddy Simulation ('LES') technique, which can accurately reproduce the cycle resolved flow inside the combustion chamber.
The resulting multi-scale tools were then be applied to study the sources and effects of CCV in different gasoline engines. Work also concerned studying, in more detail, the effects of local factors, as early flame kernel growth at the spark plug and the interaction between the flow in the FIS and the fuel spray in a vessel, on CCV. The resulting improved understanding of CCV in gasoline engines was capitalised in the form of models able to reproduce the characteristics and effects of CCV in multi-cycle 1D-CFD simulations of operating points subject to cyclic variability.
Finally,the improved three industrial 1D-CFD codes incorporating these models was applied in case studies aimed at demonstrating the benefits to be expected from a better prediction of CCV in terms of CO2 and pollutant emissions under real driving conditions. The LESSCCV partnership brings together major European engine simulation software vendors, research centres and Universities from seven European countries. All internationally recognised for their expertise in engines and simulation.
Funding
Results
Acquirement of knowledge aimed at deepening the understanding of the sources of Cyclic Combustion Variability ('CCV') related to flow phenomena, and of their effects on the operation of advanced spark-ignition ('SI') engines.
The LESSCCV project contributed to a better understanding of combustion in gasoline engines under realistic operating conditions. The improved engine simulation was able to reproduce causes and effects of CCV on a computing time inexpensive manner, thus lessening by design the negative effects related to the occurrence of CCV in spark-ignition engines.
Innovation aspects
LESSCCV used advanced Computational Fluid Dynamics ('CFD') engine simulation to gain a better understanding of Cyclic Combustion Variability ('CCV').
CFD approaches like Large-Eddy Simulation ('LES'), particularly suited for addressing non-cyclic phenomena, allow studying in detail complex phenomena in real configurations. However, the required CPU time is far too large to comply with industrial requirements on return times. Other CFD tools are much less CPU time intensive, and can run as fast as real time, making them suitable in particular for developing control strategies. Yet they cannot predict complex phenomena as CCV.
The originality of the research is the combination of advanced simulation studies based on LES to gain a deeper insight into the complex combination of phenomena, and to capitalise the acquired understanding in the form of phenomenological models. This combination can be used to explore control strategies aimed at reducing the occurrence and negative impact of CCV.
Technical Implications
Large-Eddy Simulation ('LES') can become very important and perhaps lead to the emergence of a numerical engine test bench on the long term beyond 2016, by exploiting the fast development of massively parallel computing power in Europe.
Strategy targets
Innovating for the future (technology and behaviour): A European Transport Research and Innovation Policy