Numerical Analysis of Airflow Cyclic Variation During Intake And Compression Process in a 4-Stroke Engine

摘要

A degree of turbulence is one of the main factors that used to optimize the combustion efficiency,the specific fuel consumption and emissions in automotive engines.A 3D numerical study was prepared to evaluate how the complex geometry of a dome-roof and a pent-roof engine influences the flow field.A 4-stroke,100cc SI motorcycle engine was used as the model.Engines operating at 1000 rpm and fixed atmospheric conditions were simulated using a commercial computational fluid dynamics(CFD) solver Star CD for cold flow simulations for both induction and compression stroke.Post processing stage was used to observe the cyclic airflows.The simulated results were utilized to compare aerodynamic characteristic in term of swirl and tumble motion.Variations of airflow in the cylinder were viewed through different specific geometry of both combustion chambers.Numerical results show that higher swirl was generated in the dome-roof shape.Results from Star CD simulations were translated into numerical data to compare the value of swirl ratio for both pent-roof and dome-roof engine. Remarkable insights are gained into how the chamber geometry can influence homogeneity of gas mixtures and indirectly affect the efficiency of an engine.