Validation of the VSB2 Spray Model for Ethanol under Diesel like Conditions

Artikel i vetenskaplig tidskrift, 2017

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