Adaptive EGR Cooler Pressure Drop Estimation 2008-01-0624

The pre EGR valve pressure is an important measurement for the Diesel engine air handling system. It is commonly used for the EGR flow calculation during engine transient operation. Due to the erosive exhaust gas, an EGR pressure sensor will eventually have gold corrosion resulting in drive-ability issues. Therefore, a software replacement for the EGR pressure sensor is desirable. However, when the EGR valve is on the cold side of the EGR cooler, the accuracy of the EGR pressure estimation deteriorates because of the variability of the pressure drop across the EGR cooler due to EGR cooler fouling. In this paper, an adaptive scheme is developed to improve the accuracy of pre EGR valve pressure estimation in the presence of EGR cooler fouling for diesel engines. The pressure drop across the EGR cooler is shown to be proportional to the velocity pressure of the EGR flow through the cooler. The corresponding resistance coefficient can be calculated through adaptation based on the fact that the pre EGR valve pressure is close to the intake manifold pressure when the EGR valve is wide-open and the EGR flow is low. Experimental data from a chassis dynamometer are used to demonstrate the effectiveness of the adaptive scheme. The accuracy of the pre EGR valve pressure estimation is significantly improved using the developed adaptation algorithm.