Combined CFD - PIV Methodology for the Characterization of Air Flow in a Diesel Engine 2018-01-1769
It is known that in-cylinder airflow structures during intake and compression strokes deeply affects the combustion process in compression ignition (CI) engines. This work presents a methodology for the analysis of the swirling structures by means of the CFD proprietary code Converge 2.3.
The methodology is based on the CFD modelling and the comparison of results with in-cylinder velocity fields measured by particle image velocimetry (PIV). Furthermore, the analysis is extended to the accuracy evaluation of other methods available to define the flow in the cylinder of internal combustion engines, such as experiments in steady flow rigs. These methods, in junction with simple phenomenological models, have been traditionally used to determine some of the fundamental variables that define the in-cylinder flow in ICE engines.
The CFD analysis is focused in the flow structures around top dead centre (TDC) at the end of the compression stroke. The Averaged swirl ratio (SR) and the distance of the vortex core center to the cylinder axis have been analyzed for different operation points and different swirl levels. Furthermore, the importance of the vortex precession effects has been also studied in detail.
Good agreement has been found between the CFD and PIV measurements. Nevertheless, they are significantly lower than those obtained by traditional/simple methods based on Steady Test Rigs.