Assessment of pilot injection strategies and n-pentanol additive effects on engine performance and emissions

Abstract

Biodiesel is a environmentally friendly, biodegradable and renewable alternative fuel, which is widely used around the world. However, the higher viscosity and NOX emissions are its main drawbacks. n-Pentanol has lower viscosity, higher oxygen content and volatility as compared with biodiesel, which is a promising additive for biodiesel/diesel blends. In this work, the influences of pilot injection (PI) strategies included pilot-main interval (PMI) and pilot injection rate (PIR), and n-pentanol additive on emission characteristics and combustion behaviors of a diesel engine at medium load were investigated. The three test fuels including diesel (D100), a mixture of 20% biodiesel and 80% diesel (BD20), and 20% n-pentanol, 16% biodiesel and 64% diesel (BDP20), respectively. The results indicated that, compared with single injection (SI), the peak of main injection heat release rate reduced and brake thermal efficiency (BTE) increased when using PI strategies. Adding n-pentanol to biodiesel/diesel (BD) blends resulted in an increase in maximum in-cylinder pressure, but BTE decreased. After utilizing PI strategies, the NOX emissions decreased significantly, but the soot, CO and THC emissions increased. As the PIR and PMI increased, the accumulation mode particles and total particle mass concentrations increased. Compared with SI, the ratio of sub-25 nm particles of BDP20 decreased with the use of PI strategies. The combination of n-pentanol additive and small PMI strategies could achieve lower total particles number concentration and smaller geometric mean diameter when compared with pure diesel.