Ethanol Fuel as Enabler for High-Efficiency and Low-Soot Combustion in Dual-Fuel and Blend Modes

Global climate initiatives and government regulations are driving the demand for zero-carbon tailpipe emission vehicles. To ensure a sustainable transition, rapid action strategies are essential. In this context, renewable fuels can reduce lifecycle CO₂ emissions and enable low-soot and NOx emissions. This study examines the effects of renewable ethanol in dual-fuel (DF) and blend fueling modes in a compression ignition (CI) engine. The novelty of this research lies in comparing different combustion modes using the same engine test rig. The methodology was designed to evaluate the characteristics of various injection modes and identify the inherent features that define their application ranges. The investigation was conducted on a single-cylinder engine equipped with state-of-the-art combustion technology.

The results indicate that the maximum allowable ethanol concentration is 30% in blend mode, due to blend stability and regulatory standards, and 70% in DF mode, due to combustion stability and emission concerns. DF mode produces higher THC and CO emissions compared to blend or conventional diesel combustion (CDC) modes. However, ethanol consistently reduces smoke formation across all engine test conditions and fueling modes. At ultra-low-NOx levels (0.5 g/kWh), smoke emissions remain below 0.5 FSN. At the highest ethanol fraction in DF mode (70%), smoke emissions decrease to very low levels (−0.1 FSN), with improvements in thermal efficiency and CO₂ emissions. DF mode requires specific injection control strategies to mitigate THC and CO emissions. In blend mode, the highest ethanol fraction (30%) results in CO₂ and soot reductions, with CO and THC emissions comparable to CDC.