Application Progress of Zero Carbon and Carbon-neutral Fuel Internal Combustion Engines

With the growing energy demand in transportation, climate change, and energy security issues coming to the fore, the development of renewable fuels is becoming urgent. Hydrogen and ammonia, which are produced from a wide range of sources and do not contain carbon themselves, will play an important role in the future decarbonization process. Various types of alcohols and ethers, which can be obtained from synthesizing the captured CO₂ and H₂ and biofuels from biomaterials, are effective ways to achieve carbon neutrality and have inherent combustion properties similar to those of gasoline or diesel. The applications of various zero carbon and carbon neural fuels in the spark ignition (SI) and compression ignition (CI) internal combustion engines were reviewed and their effects on engine performance and emission characteristics were analyzed. Hydrogen, a zero-carbon fuel, has good combustion characteristics and can be used alone to achieve zero carbon emissions, and can be an additive to promoting the combustion of the main fuel to reduce carbon emissions. Ammonia, another zero-carbon fuel, has excellent anti-knock properties and can be mixed with hydrogen in engines, however, higher nitrogen oxide (NO_x) emissions need to be concerned. Various types of carbon-neutral fuels can be used alone or mixed with hydrogen in engines to attain engine high efficiency and low emissions.