Evaluation of the Effects of Equivalence Ratio on the Combustion in an HCCI Engine

In this paper, the influence of equivalence ratio on combustion characteristics have been examined by considering 16 different operating conditions. The fuel used in this research is gasoline and the ignition takes place in two stages. The first stage of combustion is due to low temperature reaction heat release (LTRHR), and the second stage is related to the high temperature reaction heat release (HTRHR). The three-dimensional computational fluid dynamics (3D-CFD) with chemical kinetics has been chosen as the numerical method. In all of the studied operating conditions, the 3D-CFD simulations were able to see the combustion properly and the increase of maximum pressure and maximum rate of heat release (ROHR max) with the rise of the equivalence ratio was properly observed. Also, by increasing the equivalence ratio, 3D-CFD model show advanced maximum pressure and ROHRmax but mistakenly predicted the start of LTRHR more delayed, while the HTRHR was properly predicted.