Modelling of Multicomponent Fuel Sprays

Sammanfattning: The use of fuel blends (conventional fuels blended with renewable ones) has gained importance in the automotive industry as an option to reduce emissions and dependence on fossil fuels. In order to make the fuel blends commercially viable, computational fluid dynamics (CFD) is used to complement the experiments (done on engines or spray chambers) by providing fundamental insight into spray formation. The work presented in this thesis is focused on modelling and CFD simulation of multicomponent fuel sprays. The spray model used in this work is the stochastic blob and bubble model (VSB2) which is a discrete multicomponent fuel spray model. One of the strengths of the model is that it uses thermodynamic equilibrium to calculate heat and mass transfer to ensure that there is no over- or under-estimation of the temperature or evaporated mass. The VSB2 also uses minimal tuning parameters for modelling. The present work extended the spray model to handle multicomponent fuels. One of the main challenges in modelling multicomponent fuels is to handle differential evaporation correctly. To address this, a non-linear equation solver was implemented . The solver interfaces with the OpenFOAM code containing the spray model. One of the main benefits of the newly implemented solver is that it can be scaled to handle a large number of fuel components with minimal effort. The multicomponent fuel spray model was validated with experimental data for one, two and three fuel components respectively in three separate cases and showedreasonably good agreement. Apart from this, the model was used to study the influence of non-ideal vapor liquid equilibrium (VLE) and showed that it is important to consider non-ideal VLE for fuels with polar molecules. The model was also used to study the influence of resolving the injector orifice and the counterbore of a gasoline direct engine (GDI) injector in two separate studies. The results of all the studies can be found in the appended manuscripts. Having thus established the multicomponent fuel spray model in through this work, in future, it can be combined with detailed chemical mechanisms and combustion models to extend the studies to investigate combustion of multicomponent fuels.