Combustion Modeling Lab at UC Berkeley

Current Research

Piston Crevice Model

Greg Chin (CML)

The piston crevices are largely responsible for the creation of emissions in Spark Ignited (SI) automotive engines. Due to a high surface to volume ratio within the crevices, heat transfer to the engine walls is large resulting in incomplete combustion within the crevices. In order to develop accurate emission models for SI and Homogeneous Charge Compression Ignition (HCCI) engines, the piston crevices must be included in the numerical model. A consistent model is developed for proper treatment of mass transfer between the core fluids and those in the crevices. For HCCI applications, we consider three zones: the piston crevices zone, the quench zone close to the cylinder walls, and the cylinder zone comprising up of the rest of the cylinder. Comparisons of the calculated results are made between the new multi-zone code and those from a 3-D CFD model coupled with multi zones against experimental data. This newly developed model also provides a realistic platform for parametric study of emission issues as well as for the development/validation of reduced chemistry.