An exhaust manifold pressure estimator for a two-stage turbocharged Diesel engine

The exhaust manifold pressure is a crucial variable for turbocharged Diesel engines, affecting the torque production and the emissions through variations in the EGR mass flow and in the residual mass fraction in the cylinder. This variable is therefore considered very relevant for closed-loop EGR and turbocharger control. However, in production applications, the cost of the pressure sensor and the particularly harsh environment where this must work are practical barriers to its actual implementation. Therefore, the need for a rapid, reliable and robust estimation of this variable from low-cost production sensors is strong, above all, in the contest of advanced engine powertrains. This work describes the development of an estimator for the exhaust manifold pressure in a turbocharged Diesel engine with two-stage turbocharger. The approach proposed relies on a feed-forward scheme based on the inversion of a two-stage turbocharger model, which includes the radial turbines, nozzles and valves. Calibration and validation results of the estimator are presented in both steady-state and transient operating conditions.