Ethanol Fuel Utilization in Internal Combustion Engines

Ethanol has emerged as a versatile renewable fuel for spark-ignition engines owing to its high octane rating, low cost and potential to reduce greenhouse-gas emissions. Its oxygenated nature promotes more complete combustion, leading to lower carbon monoxide and particulate emissions, although oxides of nitrogen may rise under certain conditions. Ethanol’s lower energy density compared with conventional petrol necessitates adjustments in engine calibration or higher volumetric fuel flow to maintain power output. Flex-fuel technology and adaptations to fuel-injection systems have facilitated the use of both anhydrous and hydrous ethanol blends at varying concentrations. Advances in materials and injector design permit reliable operation despite ethanol’s corrosive tendencies and differing spray characteristics. Globally, ethanol utilisation supports the diversification of energy sources, mitigates reliance on crude oil and offers particular appeal in regions with abundant biomass feedstocks. Research continues to refine blend ratios, combustion chamber geometry and injection strategies to optimise performance, emissions and fuel economy across a range of engine architectures.

Research from Nature Portfolio

Recent numerical studies have characterised the spray dynamics of ethanol–biodiesel–diesel mixtures using high-resolution computational fluid dynamics in a constant volume chamber. Investigations under non-evaporative conditions at varying injection pressures and nozzle diameters revealed that hydrous ethanol blends exhibit distinct penetration lengths and spray cone angles compared with pure diesel. Optimisation of nozzle geometry and injection timing was shown to enhance atomisation of ethanol-containing fuels, compensating for lower liquid density and higher volatility. These insights provide a pathway to adjust injection parameters for hybrid diesel–ethanol systems, improving mixture formation and reducing soot formation without extensive hardware modification.

Ethanol Fuel Utilization in Internal Combustion Engines publication trend

The graph below shows the total number of articles in ethanol fuel utilization in internal combustion engines across all publications each year (not limited to Nature Index journals).

Technical terms

Spark-ignition engine: An internal combustion engine in which the air–fuel mixture is ignited by an electric spark, commonly used with petrol or ethanol blends.

Volumetric compression ratio (VCR): The ratio of the total cylinder volume when the piston is at bottom dead centre to the clearance volume at top dead centre; higher VCR can improve thermal efficiency.

Brake thermal efficiency (BTE): The ratio of the useful power output at the engine crankshaft to the chemical energy input of the fuel, indicating combustion effectiveness.

Specific fuel consumption (SFC): The mass or volume of fuel consumed per unit of power output over time, used to assess engine fuel economy.

Hydrous ethanol: Ethanol containing a defined percentage of water (typically 5–10 per cent), which can be used directly in modified engines without full dehydration.

Cycle-to-cycle variation (CCV): Fluctuations in combustion parameters such as peak pressure or heat release between successive engine cycles, affecting performance consistency and noise.

References

1. Numerical analysis of spray characterization of blends of hydrous ethanol with diesel and biodiesel. Scientific Reports (2024).
2. An Assessment of the Performance and Emissions of an Otto Power Generator Group Operating with Wet Ethanol at a High Volumetric Compression Ratio. Energies (2024).
3. Spark Ignition Engine Combustion, Performance and Emission Products from Hydrous Ethanol and Its Blends with Gasoline. Energies (2016).
4. Experimental Investigation of Hydrous Ethanol Gasoline on Engine Noise, Cyclic Variations and Combustion Characteristics. Energies (2022).