Experimental investigation into the number, micromorphology, functional group composition, and oxidation activity of particles from diesel engine with biodiesel blend

Abstract

Biodiesel is a promising alternative clean fuel for vehicles. In this paper, comprehensive particulate characteristics, including the particle number (PN), particle mass (PM), particle size distribution, particle micromorphology, chemical functional groups and particle oxidation activity from biodiesel blend B20 (20% biodiesel and 80% diesel by volume), were investigated based on a diesel bus using a heavy chassis dynamometer bench. Results showed that B20 could reduce the PN by 18.8% and the PM by 27.3%. The reduction efficiency of B20 on the accumulation mode particles was higher than that of the nucleation mode ones, which were 43.2 and 7.6%, respectively, thereby causing the proportion of the nucleation mode particles in B20 to increase from 54 to 66% in comparison with that of D100 (pure diesel). In terms of the particle micromorphology, the average fractal dimension of the particles from B20 was higher than that of D100, indicating that the particles from B20 were more compact. The proportion of typical core–shell structure particles in the basic carbon particles of B20 was higher than that of D100, and the coincidence degree between particles was also higher for B20; additionally, B20 preferred to produce basic carbon particles with a regular spherical shape. The graphitization degree of the particles increased with increasing oxidation temperature, but the lattice defect degree decreased. The Raman analysis reflected that the particles of B20 had a higher lattice defect degree but a lower graphitization degree compared with the particles of D100. The ratio of O/C, as well as the sp3/sp2 ratio of the B20 particles, were higher than those of the D100 particles, also indicating that more defects were present in the B20 particles. The particles from B20 exhibited higher oxidation activity in comparison with the particles from D100.