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T. Lauer, N. Pizzirani, S. Murakami:
"Computational study on the combustion concept of a lean burn gas engine";
Talk: Motorische Verbrennung - Engine Combustion Processes, München (invited); 2011-03-24 - 2011-03-25; in: "Motorische Verbrennung 10.Tagung", A. Leipertz (ed.); Schriftenreihe 11.1 (2011), ISBN: 3-931901-72-6; 103 - 114.

A further improvement of the combustion process will be necessary for large gas engines to meet future emission legislations and to achieve highest efficiencies. The numerical simulation is an important tool to investigate a wide range of combustion parameters and to reduce expensive test bench measurements.
In this paper a combination of CFD-simulation, 1D-simulation and the design-of-experiment method was used to identify an optimal piston shape for highest efficiency and with respect to a nitric oxide formation that meets future emission legislation. It could be shown that even with the restriction of low nitric oxide emissions a short combustion duration is the best solution to reach a high combustion efficiency. In combination with the short combustion a late ignition timing was chosen to control the formation of nitric oxides.
The CFD-simulations further showed that the required short combustion can only be realized when there is little interaction between the propagating flame front and the piston surface. Therefore, a piston with a deep concave bowl was introduced. This solution is regarded as the most promising concept to achieve a high efficiency and low nitric oxide formation.