Microemulsion Fuels in Compression Ignition Engines
Summary
Microemulsion fuels represent a distinctive class of advanced bio-derived fuels engineered to improve the combustion characteristics and emissions profile of compression ignition engines. Formulated by dispersing nanometre-scale droplets of polar components such as ethanol or water in a continuous hydrocarbon phase, these systems harness surfactants or ionic liquids to achieve thermodynamic stability and uniformity. Microemulsions combine the high energy density of diesel with the oxygen-rich nature of polar fuels, leading to enhanced atomisation, accelerated ignition, and more complete combustion. Such benefits translate into reductions in soot, particulate matter and nitrogen oxides, while maintaining or improving brake thermal efficiency. Their tunable droplet size and composition also offer the flexibility to meet stringent fuel standards and to integrate renewable feedstocks such as waste cooking oil or plant-derived fatty acids. Ongoing research has focused on elucidating phase behaviour, optimising surfactant systems, and evaluating long-term storage stability, along with engine bench and field trials to verify performance under realistic operating conditions.
Research from Nature Portfolio
Recent studies have advanced the design of microemulsion fuels through the incorporation of novel ionic liquids derived from renewable sources. In one approach, diquaternary ammonium ionic liquids were synthesised via quaternisation of biobased precursors and employed to solubilise ethanol in blends of diesel and waste cooking oil. Dynamic light scattering revealed droplet sizes in the range of 4.8–11.2 nm with exceptional stability over several months. These formulations delivered cetane indices above 53, heating values close to 38.5 MJ/kg and reduced theoretical air requirements for complete combustion, indicating lower pollutant formation. Another breakthrough involved ionic liquids generated from castor-oil-derived ricinoleic acid, which facilitated ethanol entrapment in diesel at varying ratios. Ternary phase diagrams showed extended microemulsion regions, and stability tests confirmed transparent, homogeneous fuel over one year. These systems maintained densities, viscosities and flash points within diesel specifications while offering enhanced oxygen content and improved cold-flow and sulphur profiles, underscoring their suitability for compression ignition engines.
Microemulsion Fuels in Compression Ignition Engines publication trend
The graph below shows the total number of articles in microemulsion fuels in compression ignition engines across all publications each year (not limited to Nature Index journals).
Technical terms
Microemulsion: A thermodynamically stable, isotropic mixture of oil, water and surfactant with droplet sizes typically below 100 nm.
Surfactant: An amphiphilic molecule that reduces interfacial tension, stabilising droplets of one phase dispersed in another.
Dynamic light scattering (DLS): A technique for measuring the size distribution of particles in suspension by analysing fluctuations in scattered light intensity.
Cetane number: A metric of diesel fuel ignition quality, indicating the delay between fuel injection and combustion onset.
References
- Stable diesel microemulsion using diammonium ionic liquids and their effects on fuel properties, particle size characteristics and combustion calculations. Scientific Reports (2024).
- Formulation of a stable diesel microemulsion using eco-friendly ionic liquids and investigation of particle size and fuel properties as an alternative fuel. Scientific Reports (2024).
- Blends of Salvinia molesta oil microemulsion with diesel in an unmodified diesel engine for the simultaneous reduction of nitrogen oxide and smoke. Heliyon (2024).
- Miscibility Analysis of Ethanol-Diesel Blends with Additives: A Comprehensive Investigation. Engineering Technology & Applied Science Research (2024).
- A comparative study on selected physical properties of diesel–ethanol–dodecanol blends. Combustion Engines (2023).
About these summaries
This Nature Research Intelligence Topic summary is created with the cited references and a large language model. We take care to ground generated text with facts, and have systems in place to gain human feedback on the overall quality of the process in line with our AI principles. We strive to create accurate and useful summaries for people unfamiliar with the research topic and that supports this goal. These pages are a beta release and will be updated as we learn how best to help people gain value from a research topic summary.
Turn complex research questions into confident strategic decisions
When you're under pressure to set direction, justify investment, or understand your competitive position, you need more than raw data — you need trusted insights you can act on.
Benchmark your performance against global peers using robust, methodologically sound analysis.
Combine quantitative metrics with qualitative expert insight to uncover strengths, gaps and emerging opportunities.
Gain tailored, decision-ready recommendations aligned to your strategic priorities.
Talk to us to learn more about our data dashboards and bespoke strategy reports.
Grow research skills, confidence and careers with training built for every stage of the research lifecycle.
Developed with Nature Portfolio journal Editors and internationally renowned experts. Discover three ways to learn:
Self-paced, online courses in convenient bite-sized units, covering key skills across scientific writing, publishing, grant writing, data analysis, and more.
Expert trainer-led workshops with hands-on exercises and real-time feedback across core research skills, delivered via interactive group sessions.
Editor-led workshops combining core principles in writing and publishing, personalised 1:1 feedback from Nature Portfolio Editors and hands-on exercises.
Explore course catalogues and workshop agendas, enquire about the options or request institutional pricing.