EGR Systems for Diesel Engines - The Road Ahead

摘要

Advanced EGR systems offer a high potential for the emission reduction on Diesel engines. Based on the challenges and potentials of Low Pressure (LP) EGR systems, a combined High Pressure (HP) and Low Pressure EGR system have been investigated. The application of this highly sophisticated EGR system allows a definition of the mass flow through the turbine independently from the EGR rate and the position of the VTG. This approach helps to run the turbocharger with the highest efficiency. Besides that, EGR path design and cooler integration into both EGR paths is discussed considering the goal of minimizing package and controlling gas temperatures to avoid condensation in front of the compressor. A model based control algorithm, which allows the realization of different EGR split strategies, shows the ability to handle the increased complexity. The application to an exemplary engine concept is shown; boundary conditions for the application of LP-EGR loops are defined. An integrated LP-EGR valve combined with an exhaust throttle is a key part of the control strategy. Combined with an advanced controls approach, this component reduces the complexity of the system and helps to keep the overall costs in an acceptable range.