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A. Peter, J. Fruehhaber, S. Schuh, T. Lauer, F. Winter, P. Priesching, M. Wensing:
"Flame quenching during dual-fuel operation investigated in experiments and simulation";
Talk: THIESEL 2018 Conference, Valencia|Spain (invited); 2018-09-11 - 2018-09-14.

Dual-fuel or substitution engines become more important in the field of maritime propulsion due to more stringent emission legislation. A ship propelled with HFO may use natural gas in protected areas. The ignition and combustion process of a premixed natural gas-air environment are curtailed by knocking combustion and flame quenching. Both phenomena are known from SI gas engines. In com-bination with high compression ratios and high loads of heavy IC engines, combustion instabilities cause unacceptable emissions.

One challenge is a too lean natural gas-air atmosphere in the combustion chamber. To avoid flame quenching, a balanced composition of injected diesel amount and natural gas-air mixture for each operation point is necessary. This work introduces a volume balance to characterize the contained en-ergy in a dual-fuel spray plume, based on Schlieren and mass flow rate measurements in a constant volume combustion chamber. Furthermore, the ambient natural gas content in rapid compression machine (RCM) experiments is varied, comparing the heat release rates to assess the rate of fuel conversion. An AVL FIRE® CFD simulation of the RCM with an optimized reaction scheme is used to investigate the ignition process of the initial diesel gas mixture in the spray plume and the combustion in the pre-mixed gas phase, respectively. The insight into the detailed chemistry allows to understand the influence of the gas equivalence ratio of the early flame development.