Study on Design Method of Combustion Reference Values for Model-Based Control of Advanced Diesel Engine

Abstract

Model-based control systems are drawing attention in relation to implementing advanced combustion technologies with high thermal efficiency and low emissions, such as homogeneous charge compression ignition and premixed charge compression ignition combustion, having low robustness. A model-based control system for engine combustion derives control inputs based on reference values and operating conditions in each cycle. Thus, it can replace the conventional control map, which necessitates a significant number of experiments. However, model-based control for combustion requires reference values, such as heat-release-rate peak timing and value, which represent the combustion state. In addition, because model-based control systems derive control inputs cycle by cycle, the combustion reference for the transient condition is critical for maximizing the benefit of such systems. Therefore, this study describes a design method of the combustion reference values for transient operation. The combustion method targeted in this study is a premixed compression ignition combustion that exhibits two-stage heat releases and can reduce combustion noise. Particularly, a method using predicted future operating conditions considering the driving characteristics is proposed. Designed combustion reference values with the proposed method were evaluated with engine control experiments in a certain part of worldwide harmonized light vehicles test cycle. Results indicate that the rate of achieving the desired two-stage heat releases combustion improved from 57% to 81% and combustion noise reduced. Thus, designing the combustion reference values for transient operation by considering future operating conditions is effective to ensure advanced combustion. In addition, such a method can consider the driving characteristics.