Method for measuring recirculated exhaust gas flow in a compression-ignition engine

Abstract

A system and method for measuring the flow rate of recirculated exhaust gas in a compression ignition engine including a plurality of engine sensors having outputs indicative of current engine conditions and a turbocharger. The system includes an exhaust gas recirculation (EGR) valve mounted in the exhaust pipe upstream of the turbocharger for diverting a selectable portion of the exhaust gas for recirculation and combination with the charge air, one or more sensors for sensing current conditions of the recirculated exhaust gas, including temperature and pressure, one or more sensors for sensing current conditions of the intake air, and control logic for determining the flow rate of the recirculated exhaust gas as a function of the sensed conditions. In one embodiment, the system includes an obstruction in the flow path of the recirculated exhaust gas and a differential pressure sensor for determining the pressure differential between a point upstream of the obstruction and a point downstream of the obstruction and control logic for determining the flow rate of the recirculated exhaust gas as a function of the current intake manifold pressure, the recirculated exhaust gas temperature, and the differential pressure drop across the obstruction.