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

Wojciech Smuga, Lukasz Jan Kapusta, Andrzej Teodorczyk

Abstract


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.

Keywords


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

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References


A. Roy, C. Segal, Experimental study of fluid jet mixing at supercritical

conditions, Journal of Propulsion and Power 26 (2010) 1205–1211.

C. Segal, S. Polikhov, Subcritical to supercritical mixing., Physics of

Fluids 20 (2008;20:052101–1 – 052101–7.) 052101–1 – 052101–7.

B. Chehroudi, D. Talley, E. Coy, Visual characteristics and initial growth

rates of round cryogenic jets at subcritical and supercritical pressures.,

Physics of Fluids 14 (2002) 850–861.

V. Zong, N. Yang*, Cryogenic fluid jets and mixing layers in transcritical

and supercritical environments., Combustion Science and Technology

(2006;178:193–227.) 193–227.

R. Rachedi, L. Crook, P. Sojka, An experimental study of swirling supercritical

hydrocarbon fuel jets., Journal of Engineering for Gas Turbines

and Power 132 (2010) 081502–1 – 081502–9.

R. Dahms, J. Manin, L. Pickett, J. Oefelein, Understanding highpressure

gas-liquid interface phenomena in diesel engines., Proceedings

of the Combustion Institute 34 (2013) 1667–1675.

M. Pilch, C. Erdman, Use of breakup time data and velocity history

data to predict the maximum size of stable fragments for accelerationinduced

breakup of a liquid drop., International Journal of Multiphase

Flow 13 (1987) 741–757.

K. Hanjali´c, M. Popovac, M. Hadžiabdi´c, A robust near-wall ellipticrelaxation

eddy-viscosity turbulence model for cfd., International Journal

of Multiphase Flow 25 (2004) 1047–1051.

J. Dukowicz, A particle-fluid numerical model for liquid sprays., Journal

of Computational Physics 35 (1980) 229–253.

G. Stiesch, Modeling engine spray and combustion processes.,

Springer, 2003.

A. Kapusta, ŁJ. Teodorczyk, Numerical simulations of a simultaneous

direct injection of liquid and gaseous fuels into a constant volume

chamber., Journal of Power Technologies 92 (2012) 12–19.

Sandia National Laboratories. Engine Combustion Network - Data

searching utility (2014).


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