Development of model based EGR mass flow rate estimation algorithm in a diesel engine

Recently, exhaust gas recirculation (EGR) is widely used to reduce NOx emissions in diesel engines. However, an excessive EGR rate in the cylinders leads to increment of particulate matter or misfire. In order to overcome this problem, the EGR mass flow rate should be controlled precisely. To control the EGR mass flow rate accurately, the EGR mass flow rate should be estimated correctly. This paper proposes a method to estimate the EGR mass flow rate based on a mean value engine model (MVEM) including characteristics of air mass flow into intake manifold, EGR mass flow into intake manifold, and air mass flow into cylinders. The MVEM also covers compressor, intercooler, exhaust manifold temperature, and EGR cooler model. The proposed algorithm calculates EGR mass flow rate with sensor outputs from mass-produced engines. The proposed EGR mass flow rate estimation algorithm was validated through simulation results using a 1-D engine model