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Main points: Ci Engine Emission Control, Emissions of Nitrogen Oxides, Engine Design Variables, Injection Timing, Injection Pressure, Boost Pressure, Mixture Formation, Injection Spray Formation, Combustion Chamber Type
Typology: Study notes
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For emission control in the CI engines, usually called as the diesel engines the following are important;
CI engines emits pollutants in solid (soot), liquid (poly aromatic hydrocarbons, fuel and oil components, sulphur acids) as well as those in gaseous (CO, HC, NO (^) x ) state. Emissions of nitrogen oxides and particulate matter from diesel engines are of main concern. Emission regulations do have limits for CO and HC as well from the CI engines, but concentration of their emissions is rather small and these have been relatively easy to control through improved engine and fuel system design. NO (^) x - PM trade off (discussed in Module 2) governs selection and optimization of many engine design variables e.g, injection timing, injection pressure, boost pressure etc as change in some engine variables may although causes reduction in NO (^) x but increases PM and vice versa. Engine design changes to reduce NO (^) x emissions many a times result also in higher brake specific fuel consumption (BSFC). This is important as the emissions of the greenhouse gas, CO 2 are also to be reduced.
The development efforts like for the SI engines have been focused on reduction of engine-out emissions and treatment of the exhaust gases. Improvements in fuel quality also have been made to meet the needs of advanced emission control technology.
In CI engines, mixture formation and combustion is heterogeneous and complex in nature. It is governed by;
The technologies used for control of PM emissions are presented on Fig. 6.2.
