Defining Start and Duration of Combustion in HCCI Engines using Mean-Value Method for Control Applications

In recent years, homogeneous charge compression ignition engines are a promising idea to reduce emissions and fuel consumption of internal combustion engines. Thus many researchers and industries have focused on this topic. Combustion phasing control is the main problem in the mentioned engines’ commercialization. There are some key parameters affecting the combustion characteristics. A single zone thermodynamic model can investigate these effects numerically. In this paper, a single zone thermodynamic model is developed and validated with experimental data. The developed model includes detailed chemical kinetics. This model is used to study the effects of inlet temperature and pressure, equivalence ratio, exhaust gas recirculation rate, inlet air humidity and engine speed on the start of combustion and its duration. The fuel was pure methane and the start of combustion is defined at a crank angle where 5% of the fuel is consumed. As a result, an interpolated relation was introduced to be used in control-oriented models. The third derivation of pressure due to crank angle is either calculated as the most important start of the combustion indicator in control utilization. The results show the proper accuracy of the model and the introduced relations. The effect of inlet air humidity on the start of combustion is negligible.