Particulate matter emission characteristics of diesel engines with biodiesel or biodiesel blending: A review

A pursuit of environment conservation as well as a fluctuated rise in diesel price has moved worldwide interests towards biodiesel, a kind of clean and renewable alternative fuel for the diesel engines. However, owing to heterogeneous mixing between the air and fuel, particle matter(PM) emissions have always been a main concern in the development of the diesel engines, especially in the face of continuously updated and progressively stringent PM emission regulation. Therefore, this paper sorts out and analyzes the studies published chiefly in scientific journals about particle matter emissions of the diesel engines used biodiesel or biodiesel/diesel blends as fuels compared with those from the traditional diesel fuels. The paper mainly includes the following sections. The first section deals with the fundamentals of particle matters from the biodiesel combustion including particle composition, physical and chemical properties. In the next, particle formation mechanism as well as PAH formation is introduced briefly. The effects of biodiesel property on particle emission are discussed in the third section. Then, the effects of operating parameters of the engines on PM emissions have been analyzed in the fourth section. After that, the influences of biodiesel blending on diesel particulate filter (DPF) and radiocarbon (¹⁴C) analysis of biodiesel particles have been reviewed. At last, general conclusions are summarized and further research targets are proposed in this paper.