Clean combustion of n-butanol as a next generation biofuel for diesel engines

This work investigates the applicability of n-butanol as a next generation biofuel to replace diesel in compression ignition engines for efficient operation, pollutant mitigation, and CO2 reduction. A high compression ratio (18.2:1) diesel research engine is configured to run on neat n-butanol. Due to the fuel property departure from diesel, n-butanol combustion exhibits striking combustion characteristics. Alternative combustion strategies, including via partially premixed compression ignition and homogeneous charge compression ignition, are enabled efficiently owing to distinctive fuel properties of n-butanol. The compression ignition of the (partially) premixed n-butanol and air mixture is capable of producing diesel-like engine efficiency and significant nitrogen oxide and smoke reductions. As the engine load increases, however, such neat n-butanol combustion exhibits rapid burning and suffers abrupt pressure rise. Thereby the engine load is generally limited below 50% of the baseline capability. A split-combustion strategy, which employs multiple event fuel injections, is found to be effective to modulate the noise of n-butanol clean combustion, thereby enabling neat n-butanol application across the full engine load range.