A Computational Study Of The Influence Of Combustion Chamber On Combustion Process And Power Performance Of A Highly-Intensified Diesel Engine

A requirement of re-designing combustion system is needed to solve the unique fuel-air mixing and combustion problems presented in a highly-intensified diesel engine with high speed, injection pressure and boost pressure. Combustion chamber, injection system and intake system have significant influence on in-cylinder air-flow, fuel-air mixing and combustion process, further, affect engine’s power performance. While combustion chamber is the place where fuel-air is mixed and combusted, a good match between them could greatly improve engine’s performance. A further investigation into the effect of combustion chamber on in-cylinder air-flow, mixing and combustion process is needed to achieve goals of faster mixing and combustion process.A CFD method using FIRE was applied to simulate in-cylinder working process, including making grid of combustion-chamber and selecting computational conditions such as methermatical models, initial and boundary conditions. Compared with the experimental data, the simulated result is validated.Firstly, two kinds of impinge-jet-type combustion-chamber are choosen to compare with the original one, finding co-type combustion-chamber is applicable. Secondly, a parameterization of the ω-type combustion-chamber is conducted, and then five dominant factors are investigated further, finding that piston bowl diameter, re-entrant angle and bowl bottom radius are more important than center-crown. Finally, a further investigation into the effect of spray angle-bowl interactions on indicated power is made to narrow down the area of good match of parameters of combustion system, finding that interaction between piston bowl diameter and spray angle is the most important of all. Further an optimization methodology basing on orthogonal design is proposed that functions both as a design exploration and as an analysis tool to examine the influence of combustion system parameters on power performance. Through diffirent analysis method, three best matches are found, in which the best one can greatly improve the in-cylinder combustion process and power performance, compared with the original,...