Switching strategy between HP (high pressure)- and LPEGR (low pressure exhaust gas recirculation) systems for reduced fuel consumption and emissions

EGR (Exhaust gas recirculation) plays a major role in current Diesel internal combustion engines as a cost-effective solution to reduce NOx emissions. EGR systems will suffer a significant evolution with the introduction of NOx after-treatment and the proliferation of more complex EGR architectures such as low pressure EGR or dual EGR. In this paper the combination of HPEGR (high pressure EGR) LPEGR (low pressure EGR) is presented as a method to minimise fuel consumption with reduced NOx emissions. Particularly, the paper proposes to switch between HPEGR and LPEGR architectures depending on the engine operating conditions in order to exploit the potential of both systems. In this sense, given a driving cycle, in the case at hand the NEDC, the proposed strategy seeks the EGR layout to use at each instant of the cycle to minimise the fuel consumption such that NOx emissions are kept below a certain limit. The experimental results obtained show that combining both EGR systems sequentially along the NEDC allows to keep NOx emission below a much lower limit with minimum fuel consumption.