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Working process of diesel engine refers to airflow, turbocharger, fuel injection, combustion, heat transfer and chemical reaction powers etc. Hence, it influences power output, fuel consumption, combustion noise and emissions, moreover directly influences reliability and durability of diesel engine. The working process of 6106 diesel engine is simulated by large universal internal combustion engine working process numerical simulation software GT-Power in this paper, and the effects of compression ratio, fuel supply advance angle and valve timing system on performance of diesel engine are analyzed. When valve-timing system is studied, the influence of intake valve close timing, exhaust valve open timing and valve overlap angle on performance are analyzed. On different operating conditions, the different timing of intake close and exhaust open, valve overlap were computed and analyzed. Finally, at different engine conditions, various optimum results were obtained.

Porous medium (PM) engine was a new type engine based on the technique of combustion in porous medium, which can realize homogeneous and stable combustion. In this paper, the combustion and working processes of a specific PM engine was simulated by a two-zone model considering the influences of the mass distribution, heat transfer from the cylinder wall, mass exchange between zones and the heat transfer in porous medium. Influences of operating parameters, e.g. intake temperature and pressure, compression ratio, the excess air ratio on the performance of the PM engine were discussed. It is found out that the porous medium, acting as a heat recuperator, can significantly enhance the evaporation of liquid fuel and preheat the mixture, which promotes the ignition and combustion in the cylinder; and that the initial PM temperature and the compression ratio are critical factors controlling the compression ignition of the mixture.

Focusing on the dual-mode dual-fuel (DMDF) combustion concept, a combined optimization of the piston bowl geometry with the fuel injection strategy was conducted at low, mid, and high loads. By coupling the KIVA-3V code with the enhanced genetic algorithm (GA), a total of 14 parameters including the piston bowl geometric parameters and the injection parameters were optimized with the objective of meeting Euro VI regulations while improving the fuel efficiency. The optimal piston bowl shape coupled with the corresponding injection strategy was summarized and integrated at various loads. Furthermore, the effects of the key geometric parameters were investigated in terms of organizing the in-cylinder flow, influencing the energy distribution, and affecting the emissions. The results indicate that the behavior of the DMDF combustion mode is further enhanced in the aspects of improving the fuel economy and controlling the emissions after the bowl geometry optimization.

Increasingly strict emission regulations and unfavorable economic climate bring severe challenges to the energy conservation of marine low-speed engine. Besides traditional methods, the energy and exergy analysis could acknowledge the losses of fuel from a global perspective to further improve the engine efficiency. Therefore, the energy and exergy analysis is conducted for a marine low-speed engine based on the experimental data. Energy analysis shows the exhaust gas occupies the largest proportion of all fuel energy waste, and it rises with the increment of engine load. The heat transfer consumes the second largest proportion, while it is negatively correlated to engine load. The energy analysis indicates that the most effective way to improve the engine efficiency is to reduce the energy wasted by exhaust gas and heat transfer. However, the latter exergy analysis demonstrates that there are other effective approaches to improve the engine efficiency.

The potential of diesel/gasoline RCCI combustion coupled with late intake valve closing (LIVC) and double direct injection of diesel for meeting high fuel efficiency with ultra-low emissions was investigated in this study. The study was aiming at high load operation in a heavy-duty diesel engine. Based on the reactivity stratification of RCCI combustion, the employment of double injection of diesel fuel provided concentration stratification of the high-reactivity fuel, which is to further realize effective control of the combustion process. Meanwhile, late intake valve closing (LIVC) strategy is introduced to control the maximum in-cylinder pressure and nitrogen oxides (NOx) emissions.

Due to the latent heat of vaporization, the efficiency of boiling heat transfer is several times and even dozens of times higher than that of the convection heat transfer. With the improvement of power density of the engine, there are more requirements for engine cooling system design. It has been confirmed that the subcooled boiling did exist in the engine cooling. If boiling heat transfer can be reasonablely used, we can achieve the objective of enhancing heat transfer without changing the existing structure. In this paper, in order to quantitatively research the subcooled boiling in the engine, we simulated the subcooled boiling in the analog channel with the Euler multiphase model, found the importance of the turbulent dispersion. In additon, we explored the applicability of existing models to subcooled boiling, and compared the results with the experiment.