Computational Fluid Dynamics Study of Tumble Generation in Spark-ignited Internal Combustion Engines

An intake port development methodology was developed for a 2.4-liter Chrysler Cirrus engine using computational fluid dynamics (CFD) simulations. A steady-state validation of the CFD computational accuracy was performed experimentally using a particle image velocimetry (PIV) test setup. The obtained experimental velocity fields were compared both qualitatively and quantitatively to 3 hypothesized turbulence models: standard k-epsilon (SKE), realizable k-epsilon (RKE), and k-omega (KO). Results indicated that the SKE model provided the most accurate simulation of the experimentally obtained velocity fields and derived nondimensional tumble numbers (NTN), with results all lying within a 95% confidence interval of accuracy. Compared to the mean experimental results, SKE proved to have a maximum percent difference of 4% and a minimum percent difference of 1%. Additionally, a transient simulation of the intake process was performed to predict how the generated vortices evolve as in a physical engine. Results obtained at bottom dead center of the transient simulation were determined to be extremely similar to the steady-state simulation results at the corresponding maximum valve lifts.