Evaluating Ammonia and Methanol as Lower-Emission Alternatives to liquefied natural gas for Medium-speed Marine Engines: A Thermodynamic Analysis

Abstract

This work investigates the potential of low-pressure, medium-speed dual-fuel engines for cleaner maritime transportation. The thermodynamic performance of these engines is explored using three alternative fuels: liquefied natural gas (LNG), methanol, and ammonia. A parametric analysis examines the effect of adjustments to key engine parameters (compression ratio, boost pressure, and air–fuel ratio) on performance. Results show an initial improvement in performance with an increase in compression ratio, which reaches a peak and then declines. Similarly, increases in boost pressure and air–fuel ratio lead to linear performance gains. However, insufficient cooling reduces the amount of fuel burned, which hinders performance. Exergy analysis reveals significant exergy destruction within the engine, which ranges from 69.96% (methanol) to 78.48% (LNG). Notably, the combustion process is the leading cause of exergy loss. Among the fuels tested, methanol exhibits the lowest combustion-related exergy destruction (56.41%), followed by ammonia (62.12%) and LNG (73.77%). These findings suggest that methanol is a promising near-term alternative to LNG for marine fuel applications.

Keywords

Ammonia / Methanol / Liquefied natural gas / Thermodynamic / Medium-speed / Dual-fuel / Engine

RIGHTS & PERMISSIONS

Harbin Engineering University and Springer-Verlag GmbH Germany, part of Springer Nature