Numerical Investigation of Fuel Injection Strategies for Ammonia-Diesel Dual-Fuel Engine

This study numerically investigates ammonia-diesel dual fuel combustion in a heavy-duty engine. Detailed and reduced reaction mechanisms are validated against experimental data to develop injection timing maps aimed at maximizing indicated thermal efficiency (ITE) while mitigating environmental impacts using stochastic reactor model (SRM). The equivalence ratio, ammonia energy share (AES), injection timing, and engine load are varied to optimize combustion efficiency and minimize emissions. The results demonstrate that advancing injection timing reduces ITE due to heightened in-cylinder temperatures, resulting in increased heat losses through walls and exhaust gases. Maximum chemical efficiency is observed at an equivalence ratio near 0.9 but decreases thereafter, influenced by ammonia’s narrow flammability range. Emission analysis highlights significant reductions in Global Warming Potential (GWP) and Eutrophication Potential (EP) with higher AES, driven by decreased CO₂ and nitrogen oxides (NOx) emissions. Acidification Potential (ACP) initially rises with higher AES due to increased NOx production but diminishes as Pressure Rise Rate (PRR) and Ringing Intensity (RI) increase with higher AES and advancing injection timing. Conversely, Ozone Forming Potential (OFP) diminishes with higher AES due to reduced volatile organic compounds emissions.