Numerical simulation study of the influence of structural parameters of combustion chamber on in-cylinder flow field of diesel engine

Based on the entity model of the type 4B26 diesel engine, calculated by CFD FIRE and combined with the software BOOST for the initial boundary conditions, the influence of combustion chamber structural parameters, such as boss height, surface-volume ratio and diameter-depth ratio of combustion chamber, on in-cylinder flow field of diesel engine was investigated. The results show that the influence of the boss height on flow field in the cylinder and the transient swirl ratio is obvious, and increasing the boss height is beneficial to urge the formation of mixture rapidly. Reducing the surface-volume ratio is beneficial for improving the maximum transient swirl ratio, and the air strength maintains well also, but has little influence to the retention of the swirl intensity. Meanwhile, reducing the diameter-depth ratio does not only improve the air flow movement strengthen in the combustion chamber, but also enhance the maximum transient swirl ratio. Besides, the persistence of swirl flow movement is satisfying.