Exhaust gas recirculation system

The exhaust gas recirculation (EGR) system is a technology used to reduce NOx emissions.
NOx is generated by high combustion temperatures. To prevent the generation of NOx, the exhaust gas recirculation system returns some exhaust gases to the intake side to reduce oxygen levels, which in turn lowers the combustion temperature and suppresses the generation of NOx.
In the case of Kubota engines, two types of EGR systems with different mechanisms are used: internal EGR and external EGR.

[Reference] Nitrogen oxides (NOx), which are a dangerous component of exhaust gas, is generated when nitrogen (N) and oxygen (O) in the air combine due to a rise in combustion temperature.
NOx can be effectively reduced by lowering the combustion temperature.
In principle, because diesel engines do not have throttle valves, and in turn do not suffer throttle loss, exhaust gas recirculation has been used since the mid-1990s mainly for the purpose of reducing NOx. However, because the large amounts of carbon dioxide and water vapor present in exhaust has a higher specific heat capacity than that of air, exhaust gas recirculation also works to provide a slight improvement in fuel consumption rates.