Performance and emission assessment of biogenic syngas -hydrogen blends for internal combustion engines

Abstract

The growing need for sustainable energy solutions is accelerating the search for alternative fuels for internal combustion engines (ICEs), with hydrogen and pyrolysis-derived gases emerging as promising candidates. This study explores the potential of syngas produced from biogenic waste, enriched with different proportions of hydrogen, as a fuel for ICEs. Experiments were conducted on a turbocharged four-cylinder direct injection (DI) engine adapted for hydrogen operation to evaluate a range of pyrolysis gas-hydrogen blends. To ensure accurate and repeatable testing, a custom-built gas mixer was developed and validated to dynamically control the fuel composition during operation. The investigation focused on combustion behaviour, thermal efficiency, and emissions characteristics for blends containing 30-100% hydrogen by volume in the intake mixture, using lambda sweep and load-cut tests. Results indicate that mixtures with higher hydrogen content have superior thermal efficiency and combustion stability, a phenomenon that can be attributed to the favorable properties of hydrogen, including its high flame speed and wide flammability limits. Results also indicate that reducing the hydrogen fraction prolongs combustion duration and increases cyclic variability, while NOx emissions decrease due to lower peak temperatures. This study highlights key challenges associated with low-calorific fuel blends, particularly regarding ignition stability and limited energy density, for which the engine demonstrated robust adaptability across a wide range of compositions. This flexibility is of critical importance for the practical implementation of decentralized combined heat and power systems, where the composition of fuel may vary.