Modeling of Spray Formation and Development in OpenFOAM with Application to Diesel and Alcohol Fuels
Legislation with reagards to fuel emissions are becoming more stringent. This creates a need for improved engine concepts and fuels. This work is part of an ongoin project to create a concept for a direct injection dual fuel engine, which uses alcohol as main fuel and diesel as a pilot. The work in this thesis is part of the task to create a CFD model for this engine that can be used for improving the current engine concept.
The first part of this project has been to validate the in-house spray model, VSB2 for usage with alcohol fuels. This was done by comparing simululations made in OpenFOAM with experimental data obtained from the Chalmers HT/HP spray chamber. The simulations showed that the model could capture spray penetration at the simulation conditions accurately. It was also concluded that it was neccessary to fix the turbulent length scale in the injector cell to get an accurate prediction of the liquid penetration.
The second part of this project has been to improve upon the spray model. This has been done by extending the spray break up treament inside VSB2. The model was extended by implenting a mechanism for removing the stable droplets inside each blob and using these to create child parcels, containing only stable droplets. It was shown that this improves the prediction of liquid penetration, especially at lower temperatures.
The Third part of this project, that is still undergoing is to do CFD simulations of a direct injection dual fuel engine. Some preliminary results are shown in this work that show good agreement in the pressure trace. The sprays also ignites in a way that is expected, with the sprays closest to the pilot igniting first. There is still some uncertainty in the results, and further studies and development are needed to produce good results.