Enhancing Dual Fuel Combustion Simulation: A Novel Geometric Approach for Accurate Flame Entrainment Estimation

Maritime transport plays a key role in the EU economy and stands as one of the most energy-efficient transportation modes. However, it is a significant and growing source of greenhouse gas emissions. In Europe, maritime transport accounts for 3 to 4% of the EU's total 〖CO〗_2 emissions, which was over 124 million tonnes of 〖CO〗_2 in 2021. These emissions are anticipated to rise to 130% of 2008 levels by 2050. To reduce greenhouse gas emissions from maritime transport, the European Union has set targets to reduce emissions by 6% by 2030 and by 80% by 2050. A promising way to achieve these targets is to use renewable fuels in marine engines. Fuels such as hydrogen or methanol can serve as the primary energy source in internal combustion (IC) engines. However, their high autoignition temperatures require an external ignition source to start combustion in compression ignition (CI) engines. The Dual Fuel (DF) approach offers an effective method for incorporating these fuels. Due to the time-consuming and costly nature of marine engine development, simulation plays a vital role in the process. To accurately simulate dual fuel combustion, certain parameters need to be carefully addressed. One crucial parameter to investigate is the estimation of the flame entrainment area, as it directly affects the mass burning rate. In this work, a novel geometric approach is developed to estimate the evolution of the flame entrainment area. This model is integrated into a multi-zone dual fuel combustion model in GT-Power and evaluated against experimental data from a single-cylinder engine (SCE) running on methanol in dual fuel mode, specifically 25 different cases with a bore size of 240 mm (SCE1) and 26 cases with a bore size of 256 mm (SCE2). The results show that using the new flame area model reduces the root mean square error (RMSE) in predicting combustion phasing (CA90) from about 10 crank angle degrees (CAD) to approximately 3.5 CAD for SCE1 and from 18 CAD to 8 CAD for SCE2. Additionally, there is a reduction in RMSE for predicting the indicated mean effective pressure (IMEP), from 2.3 bar to 1.3 bar for SCE1 and from 1.4 bar to 1.0 bar for SCE2. Significant improvements are also observed in the heat release rate curve, specifically in the tail of combustion.