Enhancing knock limit in hydrogen–gasoline dual fuel engine through methanol addition and injection pressure optimization
S.T.P PURAYIL, SAB AL-OMARI, E. ELNAJJAR
Abstract. Hydrogen-enriched engines have gained considerable attention due to their superior combustion and emission characteristics. However, the unique properties of hydrogen make it more susceptible to combustion knock, particularly at higher hydrogen fractions, thereby limiting its practical application. This study investigates the influence of methanol–gasoline blending and varying fuel injection pressures on engine performance and emission characteristics. Nevertheless, limited research has been conducted on the collective effect of methanol–gasoline blends and injection pressure variation on the knock resistance of hydrogen-enriched spark-ignition engines. Gasoline was blended with methanol at volumetric proportions of 20% and 50% and injected at fuel pressures of 80 and 140 bar. Hydrogen was supplied through the intake manifold in steps of 2 litres per minute (L/min) until combustion knock was detected. Results showed that both increasing the methanol proportion and raising the injection pressure delayed the knock occurrence, with the most significant improvement obtained when these strategies were applied together. While higher methanol proportion and greater injection pressure decreased brake thermal efficiency, cylinder pressure and NOx formation, the introduction of hydrogen counteracted these effects by enhancing engine output. A key finding was that combining a 50% methanol fraction with 140 bar injection pressure pushed the hydrogen knock limit from 14 L/min to 20 L/min. These results demonstrate a practical route to extending hydrogen utilization and supporting cleaner, more efficient engine operation in future low-carbon transportation systems. These results demonstrate a practical route to extending hydrogen utilization and supporting cleaner, more efficient engine operation in future low-carbon transportation systems.
Keywords
Hydrogen, Methanol, Injection Pressure, Knock, SI Engine, Dual Fuel
Published online 6/20/2026, 8 pages
Copyright © 2026 by the author(s)
Published under license by Materials Research Forum LLC., Millersville PA, USA
Citation: S.T.P PURAYIL, SAB AL-OMARI, E. ELNAJJAR, Enhancing knock limit in hydrogen–gasoline dual fuel engine through methanol addition and injection pressure optimization, Materials Research Proceedings, Vol. 67, pp 47-54, 2026
DOI: https://doi.org/10.21741/9781644904176-7
The article was published as article 7 of the book Climate Action and Sustainability
Content from this work may be used under the terms of the Creative Commons Attribution 3.0 license. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
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