Parametric analysis of flow and combustion phenomena for ammonia-diesel heavy-duty engine considering intake air temperature and swirl ratio number

For an extended period, the combustion performance of ammonia-diesel dual-fuel (ADDF) engines has been limited by the quality of the mixture formation. On this basia, this study investigates the effects of intake air temperature and swirl ratio on ammonia/diesel dual-fuel engine performance using CONVERGE simulations of a Caterpillar 3401 model. The findings reveal that higher intake air temperatures reduce peak cylinder pressure, indicated mean effective pressure (IMEP), and indicated thermal efficiency (ITE) in ADDF mode, yet ADDF still outperforms pure diesel operation. Notably, elevated intake air temperatures decrease equivalent greenhouse gas (GHG) emissions and unburned ammonia in ADDF combustion. Enhanced swirl promotes better fuel-air-ammonia mixing, reducing unburned ammonia. Analysis shows that increased swirl suppresses flame propagation, improving IMEP and ITE in ADDF, but higher swirl ratio causing a decline in both metrics as swirl rises. Critically, under the ammonia energy fraction (AEF) of 40, the combination of an intake air temperature of 310 K and a swirl ratio of 2.0 can achieve the peak indicated thermal efficiency (39.36 %), while the unburned ammonia emissions remain at a relatively low level. Furthermore, ADDF mode consistently reduces NOx emissions relative to pure diesel, reaching 1.88 g/kW·h at the AEF of 40 and swirl ratio of 3. These results underscore the trade-offs between intake air temperature, swirl ratio, and emissions in ADDF engines, offering insights for optimizing dual-fuel combustion strategies.