What does EGR on a car mean?
1 Answers
EGR on a car stands for Exhaust Gas Recirculation system, which refers to the process of redirecting a portion of the engine's exhaust gases back to the intake manifold, where they mix with fresh air-fuel mixture and re-enter the cylinders. Since the exhaust gases contain large amounts of polyatomic gases such as CO2, which cannot combust but absorb significant heat due to their high specific heat capacity, the maximum combustion temperature of the mixture in the cylinders is reduced, thereby decreasing the formation of NOx. EGR primarily functions in the following ways: 1. The CO2 and water vapor in EGR significantly increase the specific heat capacity of the working fluid, while the addition of exhaust gases also dilutes the oxygen concentration in the original mixture, slowing down the combustion rate. This results in a decrease in both the peak and average temperatures during combustion, disrupting the favorable conditions for NO formation and greatly reducing NOx emissions. 2. Since gasoline engines typically regulate load through quantity control, applying EGR in gasoline engines can correspondingly increase the intake air volume. An increase in the EGR rate can reduce the throttle loss under medium and low load conditions, thereby lowering the fuel consumption rate of the gasoline engine.
