Numerical Estimation of Medium-Speed Engine Swirl Ratio by Cylinder Induction Modeling

A numerical study of airflow at piston engine ports and the cylinder was conducted to obtain the swirl ratio and manifold volumetric efficiency. The mathematical model of the cylinder induction was validated by comparing it with published experimental data. Swirl ratio and manifold volumetric efficiency were analyzed using computational fluid dynamics (CFD) modeling of cylinder induction and compression strokes. The effects of charge pressure, engine speed, and charge air temperature on swirl ratio were studied. It was also found that the swirl ratio slightly increases as inlet air temperature and pressure grow, and it linearly decreases as engine speed rises. Furthermore, it was found that vortex speed is proportional to the power of 0.9 of the engine speed. The reasons for the changing swirl ratio and manifold volumetric efficiency were researched.