Coordinated EGR-rate model-based controls of turbocharged diesel engines via an intake throttle and an EGR valve

Abstract

This paper demonstrates prerequisites and performance of a model based approach for controlling mass air flow (MAF), and consequently exhaust gas recirculation (EGR) fraction, by coordinating the use of the EGR valve and the intake throttle (THR). The proposed approaches use EGR as the main actuator and the intake throttle to serve as an extension of the EGR valve to control EGR rates when EGR actuator saturates. The idea is to consider the EGR and THR as one union. The effective flow area of both actuators combined regulates the EGR rate via the command calculated by the model-based inverse function with the feedback signals. A new approach to create a reliable volumetric efficiency model is proposed in this paper that the impact of intake manifold temperature and the pressure difference between the intake and exhaust gas pressure are taken into account. The proposed volumetric efficiency model shows better and more robust estimation of in-cylinder flow rates compared to that of the traditional volumetric efficiency map.