Synergistic effects of ammonia and duckweed bio‐oil water emulsion in an <scp>RCCI</scp> engine: Experimental and <scp>ANN</scp> ‐based validation

Abstract This research explores reactivity‐controlled compression ignition (RCCI) engine combustion with duckweed bio‐oil (DBO) water emulsions and ammonia combinations to create new sustainable and low‐carbon fuels. Six test fuels, including diesel base, pure duckweed bio‐oil, duckweed bio‐oil with 10% water emulsions, and ammonia energy compositions of 20% (A20), 40% (A40), and 60% (A60) were examined and tested under steady‐state engine conditions. The emulsions were mixed using an on‐the‐fly mixing system to provide homogenization, and ammonia was injected separately with a dedicated port injection system to provide controlled reactivity stratification. The experimental tests indicated that the best combination for engine emissions and performance was with 40% ammonia content, which decreased emissions of hydrocarbons by 18%, carbon monoxide emissions by 9%, carbon dioxide emissions by 6%, and nitrogen oxides emissions by 11% and 19% for smoke emissions with 18% lower emissions than diesel. The improvements were realized through the combined effect caused by duckweed bio‐oil's oxygen content, micro‐explosions during secondary atomization from water emulsions, and ammonia's carbon‐free and hydrogen‐rich combustion properties. Notably, engine BTE and BSEC for this combination were both within 2% of diesel, and this combination is fit for dropping and working properly like normal diesel. The experimental findings were accurately predicted by an Artificial Neural Network that showed very accurate values with R 2 = 0.977–0.994 and RMSE and MPAE &lt;0.04 and 4%, respectively. This research gives emphasis to new duckweed emulsions with ammonia fuels that can provide new solutions for efficiency and other emissions problems in low‐temperature combustion engines for heavy vehicles.