J. Matheis, S. Hickel (2018)
International Journal of Multiphase Flow 99: 294-311. doi: 10.1016/j.ijmultiphaseflow.2017.11.001

We present and evaluate a two-phase model for Eulerian large-eddy simulations (LES) of liquid-fuel injection and mixing at high pressure. The model is based on cubic equations of state and vapor-liquid equilibrium calculations and can represent the coexistence of supercritical states and multi-component subcritical two-phase states via a homogeneous mixture approach.

Well-resolved LES results for the Spray A benchmark case of the Engine Combustion Network (ECN) and three additional operating conditions are found to agree very well with available experimental data. We also address well-known numerical challenges of trans- and supercritical fluid mixing and compare a fully conservative formulation to a quasi-conservative formulation of the governing equations. Our results prove physical and numerical consistency of both methods on fine grids and demonstrate the effects of energy conservation errors associated with the quasi-conservative formulation on typical LES grids.

Full phase information for LES of Spray A using the FC-EQ approach. Left and right column show contours from blue to red shades of dodecane and nitrogen partial densities, respectively. All cells with 0.1% > VVF > 99.9% are blanked out. The background contour shows the temperature field from dark to light shades.


Comparison of experimental data and predictions by current numerical model. (a) Numerical (solid lines) and experimental (dotted lines) liquid and vapor penetration trajectories. (b) Experimental schlieren image. (c) Numerical schlieren image for FC-EQ LES. See Pickett et al. (2011) and for details on experimental data (Sandia; Injector SN 210677; 0% O2; Injection duration 1.5 ms).