Study of a CI Engine for off-road in Diesel-Hydrogen Dual Fuel Configuration

Hydrogen as fuel in internal combustion engines is a promising solution for reducing greenhouse gas emissions, as its combustion produces only water vapor. One potential application is in dual fuel (DF) engines, where diesel is used to ignite the mixture, and hydrogen serves as the primary fuel. However, there is limited literature on the use of hydrogen in compression ignition (CI) engines for off-road applications running in dual fuel diesel/hydrogen, which motivates this study. The focus is on a 3-cylinder, 1-liter naturally aspirated (NA) engine with a compression ratio of 17.5:1 equipped with direct injection (DI) for diesel. Retrofitting the engine with 3 port fuel injection (PFI), it was possible to feed the engine with hydrogen by the control system elaborated in the laboratory. The study aims to analyze dual fuel diesel/hydrogen combustion characteristics and the emissions across different engine speeds (from 1600 rpm to 3600 rpm) and loads (30%, 50 % and 70%). The dual fuel operation was done by using 10% of the maximum load provided by diesel, and the overall load is adjusted by increasing the hydrogen amount. Engine load was managed up to a premixed ratio between 39 to 62 % of energy provided by hydrogen, depending on the engine speed. The results indicate that the premixed charge of hydrogen burns differently, driven by diesel fuel. This behavior depends on the effective excess of air in the engine. Comparing the emissions in dual fuel configuration at the same diesel engine power, CO2 and NOx emissions decrease up to 65% and 52%, respectively, at 70% load. On the other hand, particulate matter concentration increases up to 77% at 50% load; it can depend on the worsening of mixing and combustion of the main injection and less production but also less oxidation of the soot.