Comparative evaluation of renewable alcohol fuels as pre-chamber fuel in turbulent jet ignition for near-zero carbon ammonia engines

Ammonia, a carbon-free fuel, shows promise for clean internal combustion engines but faces ignition and combustion challenges. This study examines the use of turbulent jet ignition with renewable alcohol fuels (methanol, ethanol, and n-butanol) in the pre-chamber to improve ammonia combustion in near-zero carbon engines. Methanol was found to significantly reduce combustion duration, shortening it by 22.74 % at a main chamber equivalence ratio (Φm) of 1.0 and a pre-chamber alcohol equivalence ratio (Φp,a) of 0.8, compared to ethanol under the same conditions. At Φm = 0.85, methanol further reduced combustion duration by 28.10 % compared to ethanol. Ethanol proved more effective in reducing ignition delay at lower pre-chamber alcohol levels, showing a 58.47 % reduction at Φp,a of 0.7 when compared to methanol. N-butanol, on the other hand, performed best at higher pre-chamber alcohol levels, achieving the shortest ignition delay and extending the lean combustion limit. During ammonia lean combustion at Φm = 0.65, n-butanol exhibited the shortest ignition delay and reached a lean combustion limit of lambda 2.0 at a total pre-chamber equivalence ratio of 2.6. Overall, methanol shortens combustion duration, ethanol reduces ignition delay at lower pre-chamber alcohol levels, and n-butanol enhances ignition delay and extends the lean combustion limit.