Comparison Between Steady and Unsteady CFD Simulations of Two Different Port Designs in a Four Valve HSDI Diesel Engine: Swirl Intensity and Engine Permeability

Swirl control strategies are useful methods for controllingmixture formation in HSDI Diesel engines. Test rigs allowsonly steady state measurements of the Swirl number, and giveonly a rough estimation of the charge motion during the actualcompression stroke within the engine. On the contrary, CFDsimulations are powerful tools to characterize the air flowdrawn into the cylinder, since they allow not only steady stateoperations, but also full dynamic modeling of the intake andcompression strokes. This paper studies an application ofcomputational fluid dynamics for predicting intake swirlintensity in an automotive 4 valve per cylinder D.I. Dieselengine. Two different intake ports are compared and the besttrade off between engine permeability and swirl intensity isassessed. Both steady state and dynamic simulations of theinduction process are carried out, and results demonstrate thatsteady state analysis is a reliable tool for predicting the portpermeability, while the same capability is not proved ininvestigating the organized charge motion within the chamber.