Final answer:
An EGR valve reduces the amount of nitrogen oxides released into the atmosphere by redirecting a portion of the exhaust gases back into the engine's combustion chamber, lowering the temperature and reducing the formation of nitrogen oxides.
Step-by-step explanation:
An EGR valve, which stands for Exhaust Gas Recirculation valve, reduces the amount of nitrogen oxides (NOx) released into the atmosphere by a vehicle's exhaust system. The EGR valve works by redirecting a portion of the exhaust gases back into the engine's combustion chamber, which helps lower the temperature of the combustion process. This decrease in temperature reduces the formation of nitrogen oxides, as they are formed at high temperatures.
The EGR valve is controlled by the vehicle's engine control unit (ECU), which opens and closes the valve depending on various factors such as engine load, speed, and temperature. When the valve opens, a small amount of the exhaust gas is mixed with the incoming air-fuel mixture. This mixture, containing inert gases like carbon dioxide (CO2) and water vapor (H2O), dilutes the oxygen and reduces the temperature of the combustion process. As a result, fewer nitrogen oxides are formed and released into the atmosphere.