Investigation of the combustion in both metal and optical diesel engines using high-glycerol ethers/diesel blends

In this article, a glycerol ethers mixture obtained from etherification of glycerol with tert-butyl alcohol and isobutylene has been used in blend (10% and 20% v/v) within a commercial diesel fuel to feed a single-cylinder research engine derived from a Euro5 compliant four-cylinder engine. The engine has been run in three significant operating points in the New European Driving Cycle emission homologation area. The results have shown the possibility to burn the diesel–glycerol ethers mixture blends without significant impact on combustion characteristics and efficiencies while, due to the oxygen content of the glycerol ethers mixture, important benefits are obtained in terms of NOx-particulate matter trade-offs at the exhaust. Moreover, tests have been performed on a diesel engine with optical access through the piston bowl. The injection and combustion processes of the pilot have been investigated by means of the simultaneous use of digital imaging in the visible and infrared ranges in order to have more information on the vapour distribution, the fuel motion before the ignition and the location of hot gas.