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n this paper, the three-dimensional CFD method is used in numerical simulation of the highly intensified diesel engine intake process. The effect of different intake flow compound modes on the highly intensified diesel engine is studied (Including compounded port with helical and tangential intake port, compounded port with two helical intake ports and compounded port with two tangential intake ports). By contrasting the instantaneous flow field, flow characteristic and inlet ability of the three compound modes, the pattern of influence on the inlet flow characteristics by compound modes is analyzed. The results indicate that the combinations of the intake port greatly affect the swirl rate and the inlet ability. The interference of the two helical intake ports is serious, causing more inlet loss. The two helical intake ports have the weakest inlet ability among the three types of intake ports. However, two helical intake ports can cause higher swirl rate. Two tangential intake ports inlet ability is the most excellent, but its swirl rate is the lowest.

In order to investigate the influence of spray position on fuel air mixing quality, three-dimensional numerical simulation of the working process of a heavy-duty diesel was conducted. To quantitatively study the mechanism of the effect of spray position on fuel air mixing process, the deviation of spray centroid was introduced to describe the spray position change in combustion chamber. The results show that the gas intake swirl can affect the spatial distribution of spray in combustion chamber under three directions in cylindrical coordinate, in which the circumferential distribution is affected most. It then can be concluded that the spray can be limited to the vicinity of the combustion chamber axis. Better spray position, which is more helpful for the process of fuel air mixing and combustion, can be achieved by using optimal swirl, so that the power performance will be improved.

Multi-dimensional simulation was applied for the investigation of the combustion system of a heavy-duty diesel engine. Firstly, the matching of combustion chamber and injection pressure has been determined by simulation. Then through intermediate characteristic parameters which could quantitatively describe the properties of the mixing and combustion, the influence of the matching of chamber caliber ratios and injection pressure on each sub-process in compression and power stroke was analyzed comprehensively. The results showed that, for the model studied in this article, increasing the combustion chamber caliber ratio and injection pressure could help expanding the distribution range of the mixture in cylinder, making the mixture more uniform, increasing the proportion of the dilute mixture, thus effectively improved the power performance.

In this paper an extensive CFD simulation of a four-stroke diesel engine is done. The flow in the intake valve is calculated in the steady state condition and the flow in eight work statuses –four kinds of pressure differences are analyzed, with two kinds of valve rising degree researched .The aim of the work is to characterize the influence of the intake pressure difference of the intake port.As a conclusion we find that as the pressure difference increases, the discharge coefficient decreases. The analysis results of the three dimensional flow field of the intake port show that in the conditions of low pressure difference and big valve rising the vortex will appear. In addition, in different pressure differences, the ratio of the pressure drop in the same region is different.

In this study, mathematical model of fuel droplet evaporation is developed. Basic relationship of gas phase model is proposed by summarizing a large number of droplet evaporation gas phase models. Predictions of gas phase model are compared in forced convection. The results show that: Predictions are strongly dependent on the choice of gas phase models. Predictions of Ranz model and Haywood model are accurate with the experimental results. Evaporation time which is predicted by the gas phase models considering Stefan flow is longer than those without considering Stefan flow. For different gas phase models, droplet evaporation time is directly proportional to environmental pressure and inversely proportional to ambient temperature and Reynolds number.