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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.

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.

This paper made use of the strengthening heat-transfer character of nanofluids and applied nanofluids to engine cooling system. CFD numerical simulation method was employed to analyze the application value of nanofluids in engine cooling. The simulation results indicated that nanofluids could enhance engine heat dissipating capacity and Cu-water nanofluids had better heat-transfer capability. It was also found that the more concentrated of the nanoparticles, the more enhanced of the engine heat dissipating capacity. When the concentration reached 5%, the heat dissipating capacity would increase by 44.1%. With a remarkable enhancement on heat-transfer capability, the workload of the pump of engine cooling system only increased by 6%, which could be acceptable.

Studies on improving heat load of sliding -contact components system (piston set and cylinder liner) by applying nanofluids have been carried out. Numerical simulation was employed and the piston set-lubricate oil-cylinder liner was considered as a coupled component. The cases of applying either the Cu-oil nanofluid or the Cu-water nanofluid was studied and compared with original case. The numerical results showed that the applying of nanofluids could improve the heat load of piston set-cylinder liner. As to the piston, the heat transfer enhancement by the cu-oil nanofluid is greater than Cu-water nanofluid, and the temperature of the first ring decreases notably. For the cylinder liner, the case of using the Cu-water nanofluid exhibits the better capability of heat transfer enhancing. Besides, the Cu-oil nanofluid also shows the potential in improving lubrication and friction of piston rings-cylinder liner contact