Diesel engines are becoming more popular over gasoline engines all around the world, due to the better fuel efficiency, low operating cost, high durability and reliability (Xu et al. 2014; Gunnarsson et al. 2015; Stratakis, G.A. 2004; Shimizu and Satsuma 2006). They are widely used to transport goods, services and people. They are the power source behind commercial transport, being employed in trucks, buses, trains and ships, as well as off-road industrial vehicles such as excavation machinery, and mining equipment. They also play a vital role in power generation and are used for farming, construction and industrial activities (Prasad and Bella 2010; Chatterjee et al. 2010). But the diesel engine is one of the largest contributors to environmental
However, the very short time allowed for chemical oxidation processes, integration in combustion chambers, the lack of homogeneity in the carbureted mixtures, and the heterogeneity and rapid variations in the temperature do not allow for the state of ideal thermodynamic equilibrium to be reached. Thus, the incomplete combustion of a hydrocarbon results in the formation of a wide range of organic and inorganic compounds distributed among the gaseous, semi-volatile and particulate phases (Stratakis 2004; Setiabudi, 2002). The gaseous phase contains CO, CO2, NOx, SOx, NH3, water vapors, volatile organic compounds (VOC), polycyclic aromatic hydrocarbon (PAH), organic/inorganic acids, halogenated organic compounds, dioxins, etc. The semi-volatile phase includes unburned fuel, lubricating oil (collectively soluble organic fraction -SOF) and liquid sulfates primarily, sulfuric acid (H2O associated with the SO3 is included as a component of the liquid particulate). The solid phase have PM or soot consisting of agglomerates of carbon nuclei as well as engine oils, debris, and ash. The present paper is devoted to review exclusively the emission and control of
An estimated amount of 110 million tonnes per year of NOx are emitted into the atmosphere worldwide (Ing. Norbert Metz, 2005). Natural or biogenic sources include lightning, forest fires and agricultural nitrogenous fertilizers (Seinfeld, & Pandis, 1998 ). Anthropogenic sources are vehicles, stationary IC engines, thermal power plants, industrial boilers, incinerators, gas turbines, iron and steel mills, cement and glass industries, petroleum refineries, nitric acid manufacture, etc. (Seinfeld, & Pandis, 1998; Bond et al., 2001). NOx emissions from various sources are shown in Fig. 1. Automobile sources contribute about 30% of the total NOx emitted anthropogenically (Ohara et al., 2007). Thus, in areas of high motor vehicle traffic, such as in large cities, the amount of NOx emitted into the atmosphere can be quite significant. NOx are metastable to their molecular constituents N2 and O2 at ambient conditions. They have a four day residence time in the troposphere, so if all anthropogenic releases ceased, tropospheric NOx concentrations would rapidly decrease to their balanced levels (about 0.1 teragrams) (Getman