Technical Paper
Comparison of Sensor Sets for Real-Time EGR Flow Estimation
2016-04-05
2016-01-1064
The Exhaust Gas Recirculation (EGR) rate is a critical parameter of turbocharged diesel engines because it determines the trade-off between NOx and particulate matter (PM) emissions. On some heavy duty engines the EGR mass flow is directly measured with a Venturibased sensor and a closed loop control system maintains EGR flow. However, on most light duty diesel engines the EGR mass flow must be estimated. This paper compares two methods for estimating EGR mass flow. The first method, referred to as the Speed Density method, serves as a baseline for comparison and uses sensors for engine speed, intake manifold pressure and temperature, as well as fresh air flow (MAF). The new, second method adds turbo speed to this sensor set, and includes additional engine modelling equations, such as the EGR valve equation and the turbine equation. Special measures are taken to allow the additional equations to execute without issue on production ECMs (Electronics Controls Modules).