Impact of alternative fuels and fuel properties on PM emissions

This chapter aims to provide the readers with material required to understand the particulate matter (PM) emissions and its adverse effect on human health, environment, ecosystem and what has been done from an fuels and engines prospective to reduce PM emissions. It also describes the factors that are responsible for PM emissions in aviation industry, such as from airports and aircraft powerplants which inlcudes primary engines and auxiliary power units. With growing concerns on environemntal pollution, International Civil Aviation Organisation (ICAO) imposed restrictions to regulate the PM emissions with Committee on Aviation Environmental Protection -11 regualtory norms (CAEP-11). There is urgency to meet these regulations at all stages of aviation operational cycles. Conventional hydrocarbon based fuels produce more PM emissions than alternative fuels due to presence of high aromatic content in conventional fuels. In particular, the aromatic content in the fuels serve as the major soot precursors; however, a certain minimum aromatic content is required to meet compatibility requirements of aircraft systems such as elastomers, sealing of systems, and so on. To reduce this harmful emission, it is essential to reduce the aromatic content in the fuels as suggested by different research studies. So this chapter in particular addresses the recent developments in a systematic manner from fuel selections, fuel properties, aromatic content, and aromatic species to PM emission reduction.