The effects of n-pentanol, di-n-butyl ether (DBE) and exhaust gas recirculation on performance and emissions in a compression ignition engine

Abstract

Compression ignition (CI) engines fueled with diesel/n-pentanol (DP) blends produce lower soot and particulate matter (PM) emissions than conventional diesel-fueled engines do. However, the low cetane number (CN) of n-pentanol inevitably results in poor ignitability and poor cold-start performance, which limits its widespread application in CI engines. Di-n-butyl ether (DBE) has a higher CN, which can improve the combustion process. In this study, DBE was added to a DP mixture, and the resulting effects on the combustion and emission performances of an engine at various exhaust gas recirculation (EGR) rates were investigated. Three fuels were tested–diesel fuel (D100), a blended fuel consisting of 20% n-pentanol (v/v) and 80% diesel (D80P20), and a fuel composed of 20% DBE (v/v) and 80% D80P20 (D64P16DB20). The results indicated that when employing the EGR strategy, the peaks of the in-cylinder pressure, maximum pressure rise rate (MPRR), brake thermal efficiency (BTE), and NOX and PM emissions for the test fuels decreased, while the carbon monoxide (CO), total hydrocarbons (THC), and soot emissions increased. Compared with the DP blend, the addition of DBE decreased the ignition delay and increased the BTE. In addition, the soot, CO, and NOX emissions were further decreased, while the THC emission of D64P16DB20 increased. In particular, under medium load, the combination of medium EGR rates (10% and 15%) and the addition of DBE to pure diesel broke the BTE, soot and NOX trade-off relationship.