Numerical Study of the Effects of Lambda and Injection Timing on RCCI Combustion Mode

Reactivity Controlled Compression Ignition (RCCI), which is a low temperature combustion mode based on the principle of working with dual fuel, has attracted the attention of researchers in recent years due to its advantages such as high thermal efficiency, low NOx and soot emissions, and controllability of combustion. In this study, the effects of injection timing and lambda on RCCI combustion mode were investigated numerically by validating the experimental data with Converge CFD software. A four-cylinder, four-stroke gasoline direct-injection engine with a compression ratio of 9.2 was used in RCCI combustion mode at an engine speed of 1000 rpm. The maximum cylinder pressure also increased and RCCI combustion was advanced while the injection timing was advanced. The highest peak pressure was obtained at SOI=-50°CA aTDC, and the lowest peak pressure was obtained at SOI=-25°CA aTDC. Similarly, the highest peak HRR value was acquired as 213 J/°CA at SOI=-50°CA aTDC. It has been observed that as the lambda decreases, the maximum cylinder pressure increases, and combustion advances. In addition, the heat release rises with a decrease in lambda value. The maximum heat release rate was acquired as 77.91 J/°CA at λ=1.2. The results show that injection timing and lambda have a great influence on RCCI combustion mode and the combustion phase can be controlled with these parameters.