Internal Combustion engines generate undesirable emissions during the combustion process. The major causes of these emissions are non-stoichiometric combustion, dissociation of nitrogen and impurities in the fuel and air.Emission control systems are installed in vehicles for the purpose of reducing the discharge of these noxious gases. These systems focus on minimizing crankcase, evaporative, and tailpipe exhaust emissions. There are three basic ways in which vehicles contribute to pollution.
1. Crankcase emissions. The combustion reactions taking place produce certain by products and unburned fuel present constitutes the crankcase emissions. In order to recirculate these gases back into the car’s engine, a PCV (positive crankcase ventilation) system is used. An EGR valve is also provided and its basic function is to recirculate some portion of the exhaust gas and run it through the combustion process again. The result of this is a more complete combustion.
2. Evaporative emissions. The evaporative emissions caused by the vaporization of gasoline comes from two sources, one is the carburetor and other is the fuel tank. The ELCD (Evaporation Loss Control Device) controls evaporative emissions by capturing the vapors and recirculating them. This device consists of an absorbent chamber, a pressure balance valve and a purge control valve. Emissions are limited by sealing the vehicle’s fuel system and keeping the vapors in a canister for reburning.
Layout of Vapor Recovery System
3. Tailpipe exhaust emissions. Unburned hydrocarbons, carbon monoxide, and nitrogen oxides constitute the bulk of tailpipe emissions. Several emissions control systems minimize the creation of these pollutants, including the catalytic converter and special fuel calibration.
The various sensors mounted on the Catalytic Converter are identified below:
