Evolution of Risk of Diesel Engine Emissions on Health During Last 4 Decades and Comparison With Other Engine Cycles: An Innovative Survey

Technological evolution has sometimes surprising and unintended consequences. Diesel engine improved drastically over time. Superficially, this translated into transforming dirty, smoky diesel engines into very clean units. However, the particles emitted by the latest engines are a several orders of magnitude smaller and more numerous. They are known as Ultra-fine particles (UFP). When they are formed in the combustion process, their surface adsorbs and traps harmful chemicals that may end up being delivered, aspired and harming humans, animals and plants. Over 40 mutagenic and carcinogenic chemicals are present in diesel exhaust particulates. Existing ceramic type filter for diesel engines, known as diesel particulate filter (DPF), is used to reduce both particulate matter (PM) number and mass concentration. The main disadvantages of DPF are cost, clogging of the filters and mechanical cracking during regeneration which causes them to fail. Alternative to DPF, devices made of metallic materials known as flow through filters (FTF) have become promising PM emission control devices. FTF have low pressure drop and less complex structure compared to DPF, but PM reduction efficiencies much lower than DPF. FTF with corona charging upstream of the filter to charge PM and imposing an electrostatic field onto the FTF to capture the PM is another alternative to DPF. This is known as electrostatic diesel particulate matter filtration system (EDPS). The EDPS has 40% more efficiency than FTF, but 10% less than DPF. This paper presents a thorough literature review on emissions, distribution of particles, their evolution and effects on health in the last 4 decades across spark ignited and compression ignited engines. The paper also discusses the characteristic and evolution of DPF, FTP and EDPS to capture diesel particles.