In this study, we perform experiments on a common-rail diesel engine to investigate the effect of diesel/n-butanol blends on particulate matter (PM) emission under pilot-main injection strategy. Three different blends (diesel, D80B20, D50B50) are compared under two distinct loads (∼30 %, ∼60 %) and two injection pressures (40 MPa, 60 MPa). Under identical load and injection pressure, the engine fueled with D80B20 has the longest ignition delay and the shortest combustion duration, resulting in the highest HC emissions. The results indicate that the addition of n-butanol can improve the mixing process of fuel and oxidizer and result in a lower mean chamber temperature. The addition of n-butanol can also reduce NOx emission (up to 25 %) because the lower mean chamber temperature caused by the lower heating value of n-butanol tends to reduce NOx emission although there is extra oxygen content in n-butanol. Moreover, the addition of n-butanol can reduce PM emission (up to 69 %) and the engine with D50B50 under low load has the lowest PM emission. We further sample the soot particles from the engine emission. The result of the Raman spectroscopy investigation of soot samples reveals that n-butanol can increase the oxidative reactivity of the particles and the shorter combustion duration of engine can increase the level of disorder of the particles. The result of FTIR spectra shows that the aromatic C[dbnd]C functional group has the highest signal intensity when the engine is fueled with D80B20 and is diffusion combustion dominated. Ministry of Education (MOE) National Research Foundation (NRF) Support from the Ministry of Education of Singapore under research grant R-265-000-681-114 is gratefully acknowledged. This project is also funded by the National Research Foundation (NRF), Prime Ministers’ Office, Singapore under its Campus for Research Excellence and Technological Enterprise (CREATE) programme.
