Validation of the VSB2 Spray Model for Ethanol under Diesel like Conditions 2017-01-2193
When developing new combustion concepts, CFD simulations is a powerful tool. The modeling of spray formation is a challenging but important part when it comes to CFD modelling of non-premixed combustion. There is a large difference in the accuracy and robustness among different spray models and their implementation in different CFD codes. In the work presented in this paper a spray model, designated as VSB2 has been implemented in OpenFOAM. VSB2 differ from traditional spray models by replacing the Lagrangian parcels with stochastic blobs. The stochastic blobs consists of a droplet size distribution rather than equal sized droplets, as is the case with the traditional parcel. The VSB2 model has previously been thoroughly validated for spray formation and combustion of n-heptane.
The aim of this study was to validate the VSB2 spray model for ethanol spray formation and combustion as a step in modelling dual-fuel combustion with alcohol and diesel. This was done by comparing spray penetration with data obtained from experiments with ethanol in a high-temperature high pressure spray chamber. The spray turbulence interaction is also investigated by the usage of different turbulence models.
The study showed that the VSB2 model can be used to predict the formation of an ethanol spray. It was also concluded that the standard k - ε performed better than the realizable k - ε model, and that it is necessary to fix the turbulent length scale in the injector cell to produce accurate results.