1. 1Korea University of Technology and Education 2 Generation Common Rail VGT Variable Swirl 32Bit Computer Elec. Controlled EGR Flap C P F Electronically Controlled EGR with Water Cooler Lamda Sensor

2.  Clean Air Act  During the 1940s, air pollution was first recognized as a problem in the LA basin in California.  During the 1950s, the smog problem  By the 1960s, emission standards were beginning to be enforced in California.  In 1970, the Clean Air Act was signed in USA. 2Korea University of Technology and Education

3.  HC  Exhaust gases leaving the combustion chamber of an SI engine contain up to 6,000ppm of hydrocarbon components, the equivalent of 1~1.5% of the fuel.  About 40% of this is unburned gasoline fuel components. The other 60% consists of partially reacted components. 3Korea University of Technology and Education

4.  Causes of HC Emissions : Nonstoichiometric Air- Fuel Ratio  Fig. 9-1 shows that HC emission levels are a strong function of AF. 4Korea University of Technology and Education

5.  Causes of HC Emissions : Incomplete Combustion  Even when the fuel and air entering an engine are at the ideal stoichiometric mixture, perfect combustion does not occur.  There are several causes of this.  Incomplete mixing  Flame quenching 5Korea University of Technology and Education

6.  Causes of HC Emissions : Crevice Volume  During the compression stroke and early part of the combustion process, air and fuel are compressed into the crevice volume of the combustion chamber at high pressure.  As much as 3% of the fuel in the chamber can be enforced into this crevice volume.  Later in the cycle during the expansion stroke, pressure in the cylinder is reduced below crevice volume pressure, and reverse blow-by occurs. 6Korea University of Technology and Education

7.  CI Engines  Because they operate with an overall fuel-lean equivalence ratio, CI engines have only about one-fifth the HC emissions of SI engines. 7Korea University of Technology and Education

8.  CO  Carbon monoxide, a colorless, odorless, poisonous gas, is generated in an engine when it is operated with a fuel-rich equivalence ratio.  When there is not enough oxygen to convert all carbon to CO2, some fuel doest not get burned and some carbon ends up as CO.  Typically the exhaust of an SI engine will be about 0.2% to 5% carbon monoxide.  A well design SI engine operating under ideal conditions can have an exhaust mole fraction of CO as low as 10-3. 8Korea University of Technology and Education

9.  Oxides of Nitrogen  Exhaust gases of an engine can have up to 2,000 ppm of oxides of nitrogen.  NOx is a very undesirable emission, and regulations that restrict the allowable amount continue to become more stringent.  NOx is created mostly from nitrogen in the air. O + N2  NO + N N + O2  NO + O N + OH  NO + H 9Korea University of Technology and Education

10.  Factors of NOx formation  Temperature : 2000~3000 K  Oxygen : Fig. 9-1, max NOx is formed at a slightly lean mixture  Time : Fig. 9-4 shows the NOX-vs-time relationship and supports the finding that Nox is reduced in modern engines with fast-burn combustion chambers 10Korea University of Technology and Education

11.  PM(particulates Matter)  The exhaust of CI engines contains solid carbon soot particles that are generated in the fuel-rich zones.  This can be seen in the heavy exhaust smoke emitted when a truck or railroad locomotive accelerates up a hill or from a stop.  Soot particles are clusters of solid carbon spheres.  These spheres have diameters from 10 nm to 80 nm.  Carbon spheres are generated in the combustion chamber in the fuel-rich zones CxHy + z O2  a CO2 + b H2O + c CO + d C(s) 11Korea University of Technology and Education

12.  Carbon Dioxide(CO2)  At moderate levels of concentration, CO2 is not considered an air pollution.  However, it is considered a major greenhouse gas. 12Korea University of Technology and Education

13.  Thermal Converters  Thermal converters are high-temp chambers.  They promote oxidation of the CO and HC.  It is necessary for a thermal converter not only to operate at a high temp, but to be large to provide dwell time to promote the occurrence of these secondary reactions. 13Korea University of Technology and Education

14.  Catalytic Converters  The most effective after-treatment system for reducing engine emissions is the catalytic converter found on most automobiles and other modern engines of medium or large size.  A catalyst is a substance that accelerates a chemical reaction by lowering the energy needed for it to proceed.  The catalyst is not consumed in the reaction and so functions indefinitely unless degraded by heat, age, contaminants, or other factors.  Catalytic converters are chambers mounted in the flow system. 14Korea University of Technology and Education

15.  Catalytic Converters  These chambers contain catalytic materials, which promotes the oxidation of the emissions contained in the exhaust flow.  Catalytic converter are called three-way converters because they promote the reduction of CO, HC, and Nox.  Structure : stainless steel container, porous ceramic honeycomb.  Catalyst : Palladium and platinum for the oxidation of CO and HC, rhodium for the reduction of NOx. CO + ½ O2  CO2 NO + CO  ½ N2 + CO2 15Korea University of Technology and Education

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18. 18Korea University of Technology and Education  Catalytic Converters  Fig.9-10 : efficiency of a catalytic converter is very dependent on temp(400 oC or above).

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20.  Particulate Trap  CI engine systems are equipped with particulate traps to reduce the amounts of particulates.  DPF(Diesel Particulates Filter) 20Korea University of Technology and Education

21.  Ammonia Injection System  Reduce NOx emissions 21Korea University of Technology and Education

22.  EGR  The most effective way of reducing NOx emissions is to hold combustion chamber temp down. 22Korea University of Technology and Education