Dual Fuel Combustion Characteristics in Diesel Engines

Dual-fuel combustion in diesel engines combines a primary alternative fuel—such as methanol, ethanol or gaseous hydrocarbons—with a small pilot injection of diesel to initiate combustion. This approach seeks to unite the high efficiency and robustness of compression-ignition engines with the lower carbon intensity of non-fossil or lower-carbon fuels. In a typical cycle, the alternative fuel is premixed with air in the intake or directly within the cylinder, while a precise quantity of diesel is injected shortly before top dead centre to serve as an ignition source. The resulting combustion characteristics differ markedly from conventional diesel operation, exhibiting a partially premixed flame front, modified heat-release rates and altered ignition delays. Optimisation of injection timing, fuel mixing strategies and in-cylinder conditions enables reductions in soot and nitrogen oxide emissions, improved thermal efficiency and flexible adaptation for diverse applications, from heavy-duty transport to marine propulsion. Challenges persist in achieving stable ignition at high substitution ratios, controlling pressure-rise rates and ensuring mixture homogeneity. Recent advances in injection technology, residual-gas management and combustion-chamber design have furthered practical realisation of dual-fuel systems, underscoring their global significance in the transition towards sustainable mobility.

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Dual Fuel Combustion Characteristics in Diesel Engines publication trend

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

Technical terms

Dual-fuel combustion: A method in which a primary low-carbon or gaseous fuel is premixed with air and ignition is initiated by a small quantity of diesel pilot fuel.

Pilot injection: A preliminary injection of diesel fuel used to ignite a predominantly premixed alternative-fuel charge under compression ignition conditions.

Ignition delay: The interval between start of fuel injection and onset of rapid heat release during combustion, affecting mixture preparation and emissions.

Premixed combustion: A combustion mode where fuel and air are homogeneously mixed before ignition, leading to a rapid heat-release event.

Negative valve overlap (NVO): An engine strategy in which inlet and exhaust valves remain closed around top dead centre to trap hot residual gases and enhance low-temperature oxidation prior to main combustion.

References

1. Retrofitting a high-speed marine engine to dual-fuel methanol-diesel operation: A comparison of multiple and single point methanol port injection. Fuel Communications (2021).
2. Alcohol flexible HD single cylinder diesel engine tests with separate dual high pressure direct fuel injection. Fuel (2021).
3. Effect of negative valve overlap in a heavy-duty methanol-diesel dual-fuel engine: A pathway to improve efficiency. Fuel (2022).