What is the device that can reduce nitrogen oxide emissions from the engine?

[SanBrynlee]

The device that can reduce nitrogen oxide emissions from the engine is the Exhaust Gas Recirculation (EGR) system. Exhaust Gas Recirculation is a technology used in small internal combustion engines for automobiles, where a portion of the exhaust gases is redirected back to the intake side to be re-breathed after combustion. There are various forms and control methods for EGR systems. Based on the actuator control form, they can be categorized into mechanically controlled EGR systems and electronically controlled EGR systems. The basic principle of Exhaust Gas Recirculation: Since the specific heat of triatomic gases such as CO2, H2O, and NO2 in engine exhaust is relatively high, when fresh air-fuel mixture is mixed with exhaust gases, the heat capacity increases accordingly. Heating this exhaust-diluted mixture requires more heat to raise the temperature by 1 degree, which means that with the same total heat release from fuel combustion, the maximum combustion temperature is reduced. Additionally, the dilution effect of exhaust gases on the fresh air-fuel mixture lowers the oxygen concentration, thereby inhibiting the formation of nitrogen oxides.