Natural Gas as a Clean Fuel for Mobility

Abstract

AbstractRegarding the rise of concerns about the emissions of diesel engines, including nitrogen oxides (NOx) and particulate matter (PM), and also the increasing energy demand, the application of alternative fuels in diesel engines has been known as an influential solution. Natural gas is a considerably promising fuel for use as a transportation fuel due to its availability, extensive infrastructure for distribution, low cost, and cleaner combustion. Using natural gas, SI engines can operate at a higher compression ratio than the conventional gasoline-fueled engines, so they present higher thermal efficiency and while they increase NOx emissions, they produce lower levels of greenhouse gas emissions, carbon dioxide, unburned hydrocarbons, and carbon monoxide. CI engines can also use natural gas fuel in dual-fuel mode, where a high-Cetane fuel is injected along with natural gas to provide a source of ignition for the charge. The dual-fuel mode generally maintains the thermal efficiency of the conventional CI engines while it significantly reduces soot emission levels. Also, in these engines, at low and medium loads, NOx emission level decreases, but HC and CO emissions rise compared to those emissions of the conventional CI engines. It is noteworthy that the dual-fuel mode exhibits longer ignition delays and lower CRs in comparison to the conventional diesel mode. In the dual-fuel mode, the engine power is reduced by almost 2.1%, however, this power reduction can be decreased by changing some operating parameters. This chapter focuses on analyzing the advantages, challenges, and different strategies of using NG in SI and CI engines.KeywordsSpark-ignition enginesCompression-ignition enginesDual-fuelNatural gasEmission