01 SPECIFICATIONS
OUTLINE OF EXHAUST GAS REGULATION
SPECIFICATIONS OUTLINE OF EXHAUST GAS REGULATION •
Diesel engines discharge the following 3 major materials that have bad effects on the human body and environment. NOx (nitrogen oxides): Respiratory disorder, acid rain HC (Hydrocarbon): Photochemical smog PM (particulate in air such as soot): Carcinogenic, respiratory disorder
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NOx is material which is produced at high temperature from nitrogen (N2) and oxygen (O2) in the air. It is produced in the diesel engine because of excessive air (nitrogen). To reduce NOx, the combustion temperature in the cylinder must be reduced to restrict oxidation of nitrogen. For this purpose, the air from turbocharger (1) has been cooled by air-cooled aftercooler (2) and recirculated (EGR system).
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HC is the main component of the fuel. HC contained in the blowby gas is the main part of the toxic material discharged from the diesel engine, but it has been discharged into the atmosphere.
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PM is produced by incomplete combustion of fuel, similarly to HC. It is particles (solid matter) sticking soot, etc. Generally, if either of NOx and PM is reduced, the other increases. To reduced PM, common rail (3) is employed, and electronically controlled high-pressure fuel injection system is used to spray fuel finely, shorten the injection period, and improve the injection timing.
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Exhaust gas regulations are made and applied in Japan, USA, and EU. The following figure shows the history of the exhaust gas regulation in USA from Tier 1 to Tier4. (History of exhaust gas regulation by EPA (*1) of USA (For engine rated horsepower: 130 to 560 kW)) The horizontal axis is NOx + NMHC (*2) and the vertical axis is PM. Discharge levels of both NOx + NMHC and PM are reduced to almost 1/10 from Tier 3 to Tier 4 Final. This exhaust gas regulation is called “Tier 4 Final Regulation”.
*1: United States Environmental Protection Agency *2: General term for hydrocarbon (HC) which highly causes photochemical reaction.
95LE-7 SERIES
01-9
