Multidimensional port-and-in-cylinder flow calculations and flow visualization study in an internal combustion engine with different intake configurations

Multidimensional simulations of coupled intake port/valve and in-cylinder flow structures in a pancake-shape combustion chamber engine are reported. The engine calculations include moving piston, moving intake valve, and valve stem. Direct comparisons of three intake configurations for the same cylinder geometry are presented: (1) standard intake valve; (2) intake valve with high-swirl shroud orientation; and (3) intake valve with across-head shroud orientation. In order to verify the calculated results, qualitative flow visualization experiments were carried out for the same intake geometries during the induction process using a transient water analog. During the intake process the results of the multidimensional simulation agreed very well with the qualitative flow visualization experiments. An important finding in this study is that the standard intake valve configuration (no shroud) generates a well-defined tumbling flow structure at BDC which is sustained and amplified by the compression process and, in turn, causes generation of a high turbulence level before TDC. A comparison between tumble ratios at BDC indicated that in-cylinder tumble was highest for the standard valve intake configuration and lowest for the across-head shroud orientation. Both the standard and high swirl shroud orientation produced the same levels of turbulence during late compression with the across-head shroud orientation being about 30% less. Many interesting features of the in-cylinder flow structures as well as differences between tumble, swirl and the local velocity and turbulence at the spark plug location for all three cases are discussed.