6. Strategies to Control Emissions from Off-Road Diesel Engines

With advancement of societies, travel over short distances in traffic snarls or long distances at high power is becoming common. Also, diesel engine is the main workhorse of the fast industrialising globe, for building infrastructure, and improving comfort. The increase in engine population working in different duty cycles, has caused rise in emissions in spaces where large population is concentrated. As emission standards are progressively raised worldwide to combat this problem, advanced and complex diesel engines are designed to meet the specifications; hand in hand, testing diesel engines according to operating cycles defined as functions of the types of duties, has become more and more sophisticated. For on-road operations, the testing cycles of different nations are becoming harmonised to avoid multiplicity of certification tests or of engine calibrations. There are many harmful chemical compounds, mainly in gaseous form in the engine exhaust; those that are in minute traces and can be healed by the nature, are not regulated; on the other hand, nitric oxides (NO_x), carbon monoxide, total hydrocarbons, particulate matter (PM) which are in large concentrations, are regulated tightly. Carbon dioxide as a significant contributor to global warming is regulated indirectly by placing a ceiling on the corporate average consumption of fossil fuels. Diesel is known for NO_x formation in the high temperature zones of diesel spray, and for creation of PM in rich cold regions of the spray. In this chapter, the impact of various parameters of operation and design, is explained in the context of diesel engines, to enable devising control strategies such as turbocharging, intercooling, exhaust gas recirculation, and water injection, or aftertreatment systems like selective catalytic reduction, diesel oxidation catalyst, and diesel particulate filter are discussed in detail.