Effects Of Fuel Properties On The Particle Size Distribution Of Diesel Engine's Particulate Emissions

The diesel engine has experienced a rapid development with its advantages of high thermal efficiency, adaptability and large output power. But the rapid development has also brought many problems, such as energy shortage and environmental pollution problems. All along, the engine's nitrogen oxide (NOx) and particulate (PM) emissions are the main obstacles that hinder its development. In order to meet increasingly strict emissions regulations, many new technologies are used to reduce diesel emissions while the formation and evolution process of particles,high-temperature reaction thermodynamics and kinetics and physical and chemical properties are changed, then the particle size is smaller and more hazardous. Introduction of new emission regulations have begun to limit the number levels of diesel particulate emissions.Therefore, the study of diesel particle size distribution of particulate emissions has important practical significance.To reveal the laws of fuel properties on particle size distribution and to determine the impact degree and scope of fuel properties on the particle size, a bag sampling system and a secondary dilution tunnel sampling system were developed. Different characteristics of fuel were made up to be studied in both the traditional single-cylinder diesel engine and high-pressure common rail diesel engine. The results reveals the particulate distribution law of diesel engine's particulate emissions and effects of fuel properties on the particle size distribution under steady and transient conditions. Main contents and conclusions are summarized as follows:1. A single-cylinder diesel engine and a high-pressure common rail diesel engine mesurement and control system were established, the basic law of diesel particle size distribution was studied, the results show that the most particles whose partical size less than 1um of single-cylinder diesel engine particulate emissions were under 500nm while the most particles whose partical size less than 560nm were under 250nm. With the increase of diesel engine load, the particle number concentrations,surface area concentration and volume concentration increases. the proportion of nucleation mode particles(Dp≤50nm)decreased. The impact of speed on the particle size distribution is smaller than that of load, and influenced by many factors. Compared with the tranditional diesel engine, high pressure common rail diesel engine has a high number of small particle size particles and total particles but has a lower proportion of the nuclear particles.2. High cetane number, no sulfur and low aromatic content natural gas liquids (GTL),low sulfur content europe III and europeⅣstandard diesel and a high oxygen content biodiesel (BTL) were matched at different ratio to prepare different physical and chemical properties fuels, on the base of which deep study about the laws of physical and chemical properties of fuel on diesel engine particulate distribution were made.The results show that,(1) Compared with petroleum diesel, biodiesel particulate emissions had smaller particle size and less accumulation mode particles(50nm