Investigation of oxygenated fuels and scrubber aftertreatment on combustion and emission characteristics of a compression ignition engine

Abstract

Compression ignition (CI) engines remain the primary power source for heavy-duty applications, including
construction machinery and marine vessels. However, they emit harmful pollutants - particularly soot - which
pose significant environmental and health risks. These impacts are exacerbated in confined environments such
as underground tunnels, where limited oxygen availability promotes the accumulation of exhaust emissions.
This study investigates the combined effects of oxygenated fuels and wet scrubbing on combustion characteristics and soot emissions in a CI engine. Fuel blends of biodiesel and OME3 with conventional diesel were formulated to provide varying levels of fuel-bound oxygen. The results show that increasing oxygen content enhances fuel reactivity, leading to shorter ignition delay and a reduced premixed combustion fraction. This results in a lower peak cylinder pressure across different engine loads. In terms of emissions, oxygenated fuels significantly reduce soot formation. A near-linear decrease in smoke concentration with increasing oxygen content is observed, with OME3 showing a stronger reduction effect than biodiesel. To further reduce emissions, a closed-loop wet scrubber system was integrated downstream of the engine. The system uses fresh water and a multi-nozzle spray configuration to enhance gas-liquid interaction. The system achieves up to 65% smoke removal efficiency at high engine loads, with performance largely governed by operating conditions rather than fuel type. Overall, the combination of oxygenated fuels and wet scrubbing provides a synergistic approach to smoke reduction, offering a promising solution for cleaner operation of diesel engines in confined and oxygen-limited environments.