A 5-Zone Model to Improve the Diagnosis Capabilities of a Rapid Compression-Expansion Machine (RCEM) in Autoignition Studies

In this work, a 5-zone model has been applied to replicate the in-cylinder conditions evolution of a Rapid Compression-Expansion Machine (RCEM) in order to improve the chemical kinetic analyses by obtaining more accurate simulation results. To do so, CFD simulations under motoring conditions have been performed in order to identify the proper number of zones and their relative volume, walls surface and temperature. Furthermore, experiments have been carried out in an RCEM with different Primary Reference Fuels (PRF) blends under homogeneous conditions to obtain a database of ignition delays and in-cylinder pressure and temperature evolution profiles. Such experiments have been replicated in CHEMKIN by imposing the heat losses and volume profiles of the experimental facility using a 0-D 1-zone model. Then, the 5-zone model has been analogously solved and both results have been compared to the experimental ones. The thermodynamic conditions can be much better replicated using the 5-zone model. Moreover, the ignition delay predictive accuracy has been also improved in the 5-zone model, since slower and more realistic pressure rise rates are reached.