Modeling of Spray/Turbulence Interaction

Research Project, 2015 – 2018

The main focus of this project is to address a shortcoming of current spray models; that being the interaction between a fuel spray and the gas phase turbulence, in order to better predict combustion within Diesel engines by CFD. The VSB2 spray model developed by Dr. Anders Karlsson has been successfully implemented in OpenFOAM and spray simulations have been performed using a tuned standard k-ε turbulence model. Results of vapor and liquid penetration, and the spray shape at various ambient conditions agree well with the experiments carried out in Chalmers high pressure and temperature spray rig. Differences in vapor penetration length are heavily dependent on turbulence modeling, and they are sensitive to actual injection rate and injection velocity, which is often not known. Hence in order to conduct a thorough validation, a large number of the parameters defining the experiments must be collected in detail and that work is carried out within CERC when necessary. Spray ignition and combustion have been simulated using the partially stirred reactor (PaSR) model and the Volume Reactor Fraction Model (VRFM) model. The VRFM describes the turbulence-chemistry interaction and is based on the Eddy Dissipation Concept (EDC). Once tuned, these two approaches give good agreement with experiments carried out in Chalmers high pressure and temperature spray rig and with the “Spray A” results of the Engine Combustion Network (http://www.sandia.gov/ecn/). Furthermore, a very recent visit to Politecnico di Milano in Italy made it possible to begin to implement the Representative Interactive Flamelet (RIF) model in OpenFOAM. That work is ongoing.