Investigation on Ammonia–Biodiesel Fueled RCCI Combustion Engine Using a Split Injection Strategy

Advanced combustion concepts in compression ignition are emerging as one of the most promising solutions to reduce nitrogen oxides (NOx) and particle emissions without sacrificing fuel efficiency. Among many advanced combustion concepts, reactive controlled compression ignition (RCCI) can achieve a wider working range. In this study, to implement RCCI operation, ammonia gas is introduced through the manifold as a low-reactive fuel, and biodiesel is injected directly as a high-reactivity fuel with a 40:60 energy ratio. The effect of biodiesel split ratio in a split injection strategy (pre- and main injections) is examined under varied load conditions, and the results are compared with ammonia/biodiesel single injection. Results indicate that the use of the 45% biodiesel split ratio at full load boosts the peak in-cylinder pressure and heat release rate and shifts the peak occurrence toward the top dead center (TDC). An increase in brake thermal efficiency (BTE) to 36.22% and reduced brake specific energy consumption (BSEC) to 8.75 MJ/kWh are 12.33% higher and 19.31% lower than ammonia/biodiesel single injection. Emissions of HC, CO, and smoke opacity were reduced to 50 ppm, 0.098% vol, and 15.6%, which are 34.21, 39.13, and 33.89% lower, while the emission of NOx was increased to 615 ppm, which is 36.06% higher than the single-injection ammonia/biodiesel RCCI combustion.