Methodologies for Air-Fuel ratio and trapped mass estimation in Diesel engines using the in-cylinder pressure measurement

Abstract

Nowadays the increasing automotive market competition together with the worsening of the environmental pollution leaded to the development of complex engine systems. Innovative control strategies are needed to simplify and improve the Engine Management System (EMS), moving towards energy saving engines and complying with the restrictions on emissions standards. In this scenario the application of methodologies based on the in-cylinder pressure measurement finds widespread applications. Indeed, the in-cylinder pressure signal provides direct in-cylinder information with an high dynamical potentiality, that is fundamental for the control and diagnosis of the combustion process. Furthermore, the in-cylinder pressure measurement may also allow reducing the number of existing sensors on-board, thus lowering the equipment costs and the engine wiring complexity.This paper focuses on the detection of the Air-Fuel ratio and the in-cylinder trapped mass after the intake valve closing from the in-cylinder pressure signal. The Air-fuel ratio estimation might allow replacing the lambda sensor, the estimation method is based on a statistical approach. The in-cylinder trapped mass estimation gives the opportunity to by-pass the CO2 measurement for the evaluation of the EGR rate, in this case the Δp method is proposed. The developed techniques were validated vs. experimental data measured at the engine test bench on a Common-Rail turbocharged Diesel engine. The results show a good accuracy in predicting Air-Fuel ratio and in-cylinder trapped mass in a wide engine operating range. Because of both the low computational burden and the good results, these methodologies are suitable to be implemented on-board.