圧縮過程における混合気の温度変動が予混合圧縮着火燃焼に与える影響の数値解析

概要

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In recent years, the homogeneous charge compression ignition engine is attracting a great interest because it is high efficiency and capable of reducing both nitrogen oxide and particulate matter emissions significantly. However, some problems remain not resolved, such as the difficulty of controlling ignition timing and combustion rate in high load. In order to solve this problem, it is investigated using thermal stratification system. In this study, the auto ignition and combustion process of isooctane-air mixture in an HCCI engine has been simulated by a multi-dimensional CFD computation. The chemical reaction is described by using a 5-step global reaction model for hydrocarbon fuels. The initial conditions of thermal heterogeneity of mixture was given at the intake valve closing time, which generated a statistically reasonable turbulent fluctuations in both velocity and temperature fields. The simulation results show that the temperature fluctuation even occurs in homogeneous mixture by heat transfer during compression. In addition, even if the thermal heterogeneity of mixture is increased, its combustion can't avoid excessive pressure rise rate in high road. In case of higher swirl ratio at the compression start, the pressure rise rate decreases with combustion retard by decreasing in-cylinder temperature.
香川高等専門学校の論文