Numerical simulations of n–heptane spray in high pressure and temperature environments

Wojciech Smuga, Lukasz Jan Kapusta, Andrzej Teodorczyk


In this study n-heptane spray in supercritical environments was simulated using commercial CFD (Computational Fluid Dynamic)
software AVL Fire. The numerical results were analyzed in terms of global spray parameter, and spray penetration.
The results obtained were compared with experimental data available at Sandia National Laboratories. N-heptane spray simulations
were performed in the same conditions as in the Sandia experiments. The goal of the study was to assess whether
the Lagrangian approach performs well in engine relevant conditions in terms of spray global parameters. Not included in
this assessment was the influence of supercritical mixing on liquid-gas interphase. The major element was the potential for
practical application of the commercial CFD code in terms of properly representing global spray parameters and thus mixture
formation in supercritical conditions, which is one of the core aspects in whole engine process simulation. The key part of
the study was mesh optimization. Therefore, the influence of mesh density on both the accuracy of calculations and the
calculation time was determined, taking into consideration detailed experimental data as initial conditions for the subsequent
calculations. This served as a basis to select the optimal mesh with regard to both accuracy of the results obtained and time
duration of the calculations. As a determinant of accuracy, the difference within a range of evaporated fuel stream was used.
Using selected mesh the set of numerical calculations were performed and the results were compared with experimental ones
taken from the literature. Several spray parameters were compared: spray tip penetration, temperature of the gaseous phase
and mixture fraction in the gaseous phase. The numerical results were very consistent in respect of spray tip penetration. The
other parameters were influenced by specific features of the Lagrangian approach. Nevertheless the results obtained showed
that the Lagrangian approach may be used for engine relevant conditions.


CFD; n-heptane; spray; injection; supercritical mixing

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