Study On Parametric Analysis Of Combustion Process And Optimization Of System In Highly Intensified Diesel Engine

As the standard of power and economic performance of diesel grows strictly, it is very essential to optimize the combustion process in a highly intensified diesel engine for better performance. The intake system, as the indispensable part of the diesel, produces important effects on the progress of evaporation, mixture formation, combustion and so on. Investigations of CFD simulation of the influence of the intake system parameters on the performance of a highly intensified diesel engine are important and valuable to improve the overall performance of the diesel engine.In this thesis, profited from the CFD software FIRE, the mathematics models for simulation of in-cylinder process are introduced for researching the combustion of the highly intensified diesel engine. According to the experiment date of combustion pressure in the cylinder and the value of power, the EBU multi-dimensional combustion model parameter A and WAVE droplet breakup model parameter C2,C4,C5 are adjusted and the performance of the highly intensified diesel engine was predicted. Furthermore, the study about the influences of the intake swirl ratio, intake temperature and intake pressure on Performance of highly intensified diesel is carried out. In order to descript the intake process of diesel more accurately and intuitively, the geometry model including the port, valve and cylinder for the simulation was built with three-dimension modeling software, and the computation was carried out by the CFD code FIRE. The study on the influences of the intake port structure on Performance of the diesel is executed by changing the structure of intake port.First, characteristic parameters reflecting air-fuel mixing and combustion behavior qualitatively have been constructed, with which, the impacting theory of the intake swirl ratio, intake temperature and intake pressure to the air flow in cylinder, the formation of mixture, combustion is revealed more accurately. Secondly, the air flow in the intake port and the cylinder during the intake progress is analyzed by building the three-dimension model including the port, valve and cylinder. Finally, the original straight geometry model of intake port is changed into the geometry model of coalition between helical model and tangential model, and the differences about intake swirl, intake air mass flow are displayed.