Fuel Oil Combustion Pollution and Hydrogen-Water Blending Technologies for Emission Mitigation: Current Advancements and Future Challenges

Abstract

In recent years, researchers have focused on exploring alternative fuel technologies that enhance engine performance and combustion efficiency while reducing nitrogen oxide (NO_x) and particulate matter (PM) emissions. Water-diesel emulsified fuel, which requires no engine modifications, has emerged as a critical pathway for cleaner diesel engine applications. This review systematically examines the combustion characteristics, emission performance, and energy efficiency of emulsified fuels in compression ignition (CI) engines. Studies indicate that compared to conventional pure diesel, emulsified fuels significantly optimize combustion processes through micro-explosion phenomena, shorten ignition delays, and improve combustion efficiency. Notably, NO_x and PM emissions are simultaneously reduced, effectively resolving the traditional trade-off dilemma between pollutant reduction targets. Emulsified fuel exhibits comparable power output and fuel consumption rates to those of pure diesel, while delivering enhanced environmental benefits. Additionally, innovative technologies such as hydrogen nanobubbles further enhance combustion dynamics by improving fuel atomization and radical generation, though challenges persist in stabilizing non-aqueous nanobubbles and scaling up production. Despite ongoing advancements in policy incentives (e.g., green hydrogen subsidies) and combustion mechanism research, industrial adoption of emulsified fuels still faces technical hurdles, including equipment corrosion and issues with long-term storage stability issues. In conclusion, water-based emulsified fuels and hydrogen-water blending technologies provide efficient and low-cost transitional solutions for reducing diesel engine emissions, with their multi-component synergistic optimization mechanisms laying a theoretical and practical foundation for future clean fuel development.

Keywords

Water-diesel emulsified fuel / Hydrogen-water blending / Micro-explosion phenomena / NO_x emissions / PM emissions / Synergistic optimization / Emission mitigation

Author Contributions

H.L.: Writing—Original Draft, Writing—Review & Editing, Visualization, Investigation. X.X.: Writing—Original Draft, Supervision, Formal Analysis. C.T.: Resources, Methodology, Conceptualization.

Ethics Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Funding

This research received no external funding.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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