Numerical Investigation of the Turbulent Flame Propagation in Dual Fuel Engines by Means of Large Eddy Simulation

Jens Frühhaber and Thomas Lauer
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Jens Frühhaber: Institute for Powertrains and Automotive Technology, TU Wien, 1060 Vienna, Austria
Thomas Lauer: Institute for Powertrains and Automotive Technology, TU Wien, 1060 Vienna, Austria

Energies, 2021, vol. 14, issue 16, 1-25

Abstract: Dual fuel combustion depicts a possible alternative to reduce emissions from large engines and is characterized by injecting a small amount of diesel fuel into a lean natural gas–air mixture. Thereby, the presence of autoignition, diffusive and premixed combustion determine the high complexity of this process. In this work, an Extended Coherent Flame Model was adapted to consider the effect of natural gas on the ignition delay time. This model was afterward utilized to simulate 25 consecutive engine cycles employing LES. In this framework, the ensemble-average flow field was compared to a RANS solution to assess the advantages of LES in terms of the prediction of the in-cylinder flow field. A detailed investigation of the heat release characteristic showed that natural gas already highly contributes to the heat release at the beginning of combustion. Furthermore, a methodology to investigate the turbulent combustion regimes was utilized. It could be ascertained that the combustion mainly occurs in the regime of thin reaction zones. Possible triggers of cycle-to-cycle variations were determined in the velocity fluctuations in the cylinder axis direction and the flame formation in the gaps between the spray plume. The findings support the understanding of dual fuel combustion and serve as a basis for developing future combustion models.

Keywords: dual fuel combustion; cycle-to-cycle variations; pilot injection; research engine; spray propagation; turbulent flames (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2021
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