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RCCI engine is proven to have better combustion control and to produce very low NOx and soot emissions. However, its operations is limited by HRR and PPRR as well as weak combustion efficiency which results in high levels of HC and CO emissions. Engine geometry and operation parameter such as injection strategy and compression ratio can affect the reactivity of fuels in cylinders as well as the gas temperature increase rate which are the important factors in controlling RCCI combustion. Injection strategies such as single and double injections have been previously studied but the effects are still unpredictable and the effects of compression ratio towards combustion characteristic and emissions require further analysis. This work deploys a 3D computational fluid dynamic (CFD) combustion model to study the effects on combustion characteristic and emissions with respect to single injection, double injection strategy and compression ratio.

Application of computational method in studying soot formation and its characteristics has become more preferable in today’s automotive field. Current developments of computer programs with higher precision mathematical models enable simulation results to become closer to the real engine combustion phenomena. In the present study, investigation on soot has been performed using various soot models with different levels of complexity, from simple two-step Hiroyasu-NSC soot model to the detailed-kinetic soot model. Detailed soot models, Particulate Mimic (PM) which is based on methods of moment and Particulate Size Mimic (PSM) which is based on sectional method, are applied in this study. Result of soot mass from Hiroyasu-NSC model provides 120% error compare to experimental result, while both detailed models provide an acceptable error of 7%.

Hydrogen fuel is a potential energy source for vehicles in the future. The emission of this fuel complies with the stringent policies issued by the International Energy Agency (IEA). Researchers have nominated the hydrogen compression ignition engine in an argon atmosphere as one of the ways to enhance power output and volumetric efficiency in the midst of pre-ignition and knock problems. Since this type of research is still in the initial stage, numerical studies have become the best method for researchers to obtain data on hydrogen fuel combustion in an argon-oxygen atmosphere. The purpose of this study was to validate the simulation results with the experimental data, investigate the combustion characteristics of hydrogen fuel in an argon-oxygen atmosphere, and to study the effects of the initial temperature and injection pressure on the combustion process. In this research, CONVERGE CFD software was used for the simulation process.

The ignition delay and combustion characteristics of hydrogen jets in an argon-oxygen atmosphere were investigated to provide fundamental data for operating an argon-circulated hydrogen internal combustion engine. Experiments were conducted in a constant-volume combustion vessel to study the effects of ambient temperature, ambient pressure, oxygen concentration and injection pressure on a pre-burning system. The hydrogen-jet penetration and flame were also investigated based on high-speed shadowgraph images. The experimental results indicated that the ignition delay (τ) increases as the ambient temperature (Ti) decreases, similar to the results obtained in an air atmosphere. The heat-release rate results also exhibited similar trends.