Effect of pilot fuel properties on engine performance and combustion stability in a tri-fuel engine powered by premixed methane-hydrogen and diesel pilot

The present work investigates the effect of pilot fuel properties on TF combustion using premixed methane-hydrogen-air (CH₄-H₂-air) mixtures ignited by a small amount of diesel pilot. Especially, we are investigating the effect of the cetane number (CN) and aromatic content (AC) on TF combustion in a single-cylinder compression ignition (CI) engine at varying charge air temperatures (T_air = 25 °C, 40 °C, 55 °C) and H₂ volume fractions (M_H2 = 10%, 20%, 40% and 60%) at lean premixed charge mixture conditions (equivalence ratio φ = 0.5). The novelty and main findings of the work consist of the following features: 1) besides the effect of H2 concentration and charge-air temperature, pilot fuel properties also play a crucial role in TF combustion, even a small amount of diesel pilot could dramatically affect the engine performance and combustion stability, 2) the CN and AC are the key factors affect the ignition delay time (IDT) and indicated thermal efficiency (ITE), 3) the in-cylinder pressure oscillation analysis based on a novel Superlets (SL) approach indicates that pilot fuel properties are important to the combustion states and combustion stability.