Improvement of Fuel Economy and Transient Control in a Passenger Diesel Engine Using LP(Low Pressure)-EGR

Diesel engines are the most commonly used power train of the freight and public transportations in the world. From the viewpoint of global warming restraint, however, reduction of exhaust emissions from the diesel engine is urgent demand. Stringent emission regulations are being proposed with growing concern on NOx, PM and CO2 emissions. Future emission regulations require advanced emission control technologies, such as SCR(Selective Catalytic Reduction), LNT(Lean NOx Trap) and EGR(Exhaust Gas Recirculation). The EGR is a commonly used technique to reduce emission. In this study, a LP-EGR(Low Pressure Exhaust Gas Recirculation) system was investigated to evaluate its potential on emission reduction and fuel economy improvement, especially for a passenger diesel engine. A 3.0ℓ diesel engine equipped with the LP-EGR system was tested using an in-house control algorithm. Fuel economy improvement was obtained using the LP-EGR system under the steady and transient operating conditions, compared to the conventional HP-EGR(High Pressure Exhaust Gas Recirculation)system. At the middle speed and load conditions, results with the LP-EGR system showed that fuel economy was improved without any deterioration of the NOx and PM emissions.