Dual-Fuel Ammonia Engines to Decarbonise Freight Operations

Abstract

Operators of diesel-powered locomotives face increasing pressure to reduce carbon and exhaust emissions from their operations and transition away from using fossil fuels. Compression ignition diesel engines remain the prime movers of choice for self-powered rolling stock due to their high torque and efficiency. However, the long service life of locomotives, often exceeding 70 years, limits rapid fleet replacement. This study presents a concept for a dual-fuel diesel-ammonia internal combustion engine for locomotives, as part of ongoing research at Brunel University of London. Using data from UK Class 37 locomotives supplied by their owners and operators, representative engine duty cycles were derived from On-Train Monitoring and Recording (OTMR) data for a number of operational routes. Engine data, obtained through load bank testing of a locomotive, was then mapped onto these operational route based engine duty cycles to calculate diesel fuel use and exhaust emissions for each route. Literature based ammonia:diesel fuel ratios, validated through engine testing at Brunel University of London, were then applied to generate a comparative dual-fuel dataset. Preliminary results suggest diesel consumption - and thus carbon emissions - can be reduced by 18–29%. A CAD model was developed to demonstrate integration of ammonia fuel tanks alongside one of the two original diesel fuel tanks. Ongoing work involves using Brunel University of London’s single-cylinder test engine, upgraded for ammonia fueling, to increase ammonia:diesel ratios and assess emissions impacts. The results support the potential of retrofitting existing diesel locomotives with dual-fuel capability as a transitional pathway to lower carbon rail transport.