Effects of dimethylformamide (DMF) and diacetone alcohol (DAA) additives on combustion parameters and exhaust emissions in diesel-fuel oil 6 mixtures

This study investigated the effectiveness of solvent use in improving the combustion and emissions of Diesel-Fuel Oil 6 (FO6) mixtures. We operated a direct-injection diesel engine at 3000 rpm over 0%–75% load, using a baseline heavy blend (DF40: diesel with 40% FO6) and DF40 with 10% or 20% (v/v) N, N-dimethylformamide (DMF) or diacetone alcohol (DAA). Adding FO6 increased BSFC by 2.7–9.0% relative to diesel across all tested loads. This confirms that high-viscosity FO6 fractions are bad for fuel economy. Adding solvents mostly canceled out this effect. DF40–DMF20 lowered BSFC by 10.99–17.48% (depending on load), while DF40–DAA20 lowered it by 8.38–15.05%. Dosing the solvent also affected the combustion process. DF40–DMF20 raised the temperature of the exhaust gas by 9.02–12.55% (DAA20: 6.38–11.07%) and, at the same time, made combustion less harsh by lowering the peak pressure rise rate by 18% and the maximum cumulative heat release by 11%. Emission responses were good for particulates and products of incomplete combustion: smoke opacity dropped by 14.7–28% with DMF20 and 10.5–20% with DAA20. DMF20 also lowered HC (2–10.2%) and CO (18.6–31.6%). NOx levels increased slightly (DMF20: 8–14.8%; DAA20: 4.5–8.9%), consistent with improved oxidation and higher local temperatures. In general, solvent-assisted mixing enables efficient use of FO6 without preheating; however, NOx reduction remains necessary. © 2026 The Authors