Abstract
In this study, a 3-dimensional transient simulation with a knock model was performed to predict knock occurrence and autoignition site in a heavy-duty LPG engine. A FAE premixed combustion model was applied to simulate flame propagation. The coefficient of the reduced kinetic model was adjusted to LPG fuel and used to simulate autoignition in the unburned gas region.
Engine experiments using a single-cylinder research engine were performed to calibrate the reduced kinetic model and to verify the results of this modeling. A pressure transducer and head-gasket type ion-probe circuit board were installed in order to detect knock occurrences, flame arrival angles, and autoignition sites.
Knock occurrence and position were compared for different piston bowl shapes.
The simulation results show good agreements with the cylinder pressure, flame arrival angle, knock occurrence, and autoignition site of the engine experiments. It also provides much information about in-cylinder phenomena and some ways to reduce knocking tendency. This knock simulation can be used as a development tool of engine design.