Effect of Ignition Timing on Combustion Performance in Ammonia-Hydrogen Blended Fuel Engine

Against the backdrop of energy structure transformation and upgraded environmental protection requirements, ammonia has been significantly attracted for its potential application as a zero-carbon fuel. However, it faces challenges such as difficult ignition, slow combustion rate, and low heating value. Thus, researching efficient combustion strategies suitable for ammonia as a fuel holds great significance. In this study, a two-cylinder diesel engine was modified into an ammonia-hydrogen blended fuel engine, experimental and simulation studies were carried out to investigate the effects of varying ignition timing on the combustion performance employed a passive pre-chamber ammonia-hydrogen fuel engine. The results show that the peak in-cylinder pressure exhibits a "first increase then decrease" trend as the ignition timing is retarded, reaching a maximum value of 7.42 MPa at the ignition timing of -27.5°CA ATDC. When the ignition timing is retarded beyond -15°CA ATDC, a double-peak phenomenon appears in the in-cylinder pressure curve. The peak heat release rate gradually increases with the retardation of ignition timing, but excessively retarded ignition reduces the combustion constant-volume degree. The combustion rate is the fastest when the ignition timing is -20°CA ATDC, with the shortest combustion duration (CA10~CA90) of 22.5°CA, which leads to the highest indicated thermal efficiency of 42.5%.