Exploring the utilization of ammonia in homogeneous charge compression ignition engine

• Increasing the equivalence ratio retards the start of combustion in ammonia HCCI. • Ammonia HCCI combustion exhibits N 2 O and NO trade-off characteristics. • Efficient N 2 O control requires a high in-cylinder temperature of more than 1800 K. • Higher intake charge temperature significantly reduces the ammonia slip. Ammonia (NH 3 ) and Hydrogen (H 2 ) are promising carbon-free alternative fuels for reducing diesel engine emissions. NH 3 is particularly appealing due to its established infrastructure. This study investigates 100% ammonia homogeneous charge compression ignition (AHCCI) using a dual approach. Experiments were conducted at two distinct NH 3 flow rates (1.966 m 3 /hr and 3.013 m 3 /hr), and a multi-zone HCCI modelling approach was used to further understand combustion behaviour. The model focused on varying the intake charge temperature (ICT) and charge equivalence ratio (Phi) to determine combustion characteristics, engine performance, and NH 3 slip. The findings indicate that initiating AHCCI combustion requires a high ICT, around 523 K. Increasing the Phi was found to retard the start of combustion (SOC). At Phi = 0.4, the maximum indicated thermal efficiency (ITE) reached 40.14% with an ICT of 553 K, with NH 3 slip remaining below 4.7%. The operational range for Phi in AHCCI mode was limited to 0.1 to 0.4 under appropriate ICT conditions. To extend this range, an analysis of NH 3 -mixed fuels was conducted, yielding promising results. These findings provide crucial insights into effectively managing ICT requirements to minimize NH 3 slip and NO X emissions, thereby facilitating the implementation of AHCCI combustion in diesel engines.