A novel phenomenological model for stratification-controlled low temperature combustion applied to a dual-fuel marine internal combustion engine supplied with natural gas and light fuel oil

As regulations become increasingly stringent, engine manufacturers are exploring innovative solutions to reduce greenhouse gas and pollutant emissions. In the marine sector, the adoption of natural gas partially replacing the light fuel oil (LFO) can be successfully employed in dual-fuel low-temperature combustion (LTC) concepts to achieve this goal. In this combustion modality, the spatial distribution of fuels with varying chemical reactivities is critical for ultra-lean mixtures combustion. Depending on fuels proportion and stratification, combustion evolution can be primarily governed by chemistry, leading to Reactivity Controlled Compression Ignition (RCCI) mode, or by flame propagation, locally initiated by a high reactivity fuel. This study investigates experimentally the combustion characteristics of a medium-bore research engine operated under RCCI mode. Natural gas is introduced into the intake port, while LFO is directly injected into the cylinder. The experimental campaign includes sweeps of engine load, air/fuel ratio, LFO quantity, valve timings, and intake air temperature, with recording and analysis of global engine operating parameters and cylinder pressure traces. A phenomenological model addressing both fuel chemistry and flame propagation is developed and validated. The simulation adopts a multi-zone approach, managing the spatial fuel distribution using an integrated spray jet model, and employing a tabulated method for auto-ignition chemistry to preserve computational efficiency. The proposed numerical approach accurately simulates experimental data with a fixed tuning constant set, giving predictions of global performance and combustion parameters with an average error below 5%. Demonstrating a proper description of engine behavior under varied operating conditions, the model effectively captures the underlying physics of these advanced combustion concepts.