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arXiv · 1801.05094

Real-Gas Effects and Phase Separation in Underexpanded Jets at Engine-Relevant Conditions

Christoph Traxinger·Matthias Banholzer·Michael Pfitzner
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Abstract

A numerical framework implemented in the open-source tool OpenFOAM is presented in this work combining a hybrid, pressure-based solver with a vapor-liquid equilibrium model based on the cubic equation of state. This framework is used in the present work to investigate underexpanded jets at engine-relevant conditions where real-gas effects and mixture induced phase separation are probable to occur. A thorough validation and discussion of the applied vapor-liquid equilibrium model is conducted by means of general thermodynamic relations and measurement data available in the literature. Engine-relevant simulation cases for two different fuels were defined. Analyses of the flow field show that the used fuel has a first order effect on the occurrence of phase separation. In the case of phase separation two different effects could be revealed causing the single-phase instability, namely the strong expansion and the mixing of the fuel with the chamber gas. A comparison of single-phase and two-phase jets disclosed that the phase separation leads to a completely different penetration depth in contrast to single-phase injection and therefore commonly used analytical approaches fail to predict the penetration depth.

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Christoph Traxinger, Matthias Banholzer, Michael Pfitzner. 2018-01-16. Real-Gas Effects and Phase Separation in Underexpanded Jets at Engine-Relevant Conditions. https://doi.org/10.2514/6.2018-1815

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