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Energies 2017, 10(12), 2116; https://doi.org/10.3390/en10122116

A Modified Version of the RNG kε Turbulence Model for the Scale-Resolving Simulation of Internal Combustion Engines

1
Department of Economics, Engineering, Society and Business Organization, University of Tuscia, 01100 Viterbo, Italy
2
Department of Enterprise Engineering “Mario Lucertini”, University of “Tor Vergata”, 00133 Rome, Italy
3
John A. Paulson School of Engineering and Applied Sciences, Harvard University, 33 Oxford St., Cambridge, MA 02138, USA
*
Author to whom correspondence should be addressed.
Received: 7 November 2017 / Revised: 24 November 2017 / Accepted: 6 December 2017 / Published: 13 December 2017
(This article belongs to the Section Energy Fundamentals and Conversion)
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Abstract

The unsteady and random character of turbulent flow motion is a key aspect of the multidimensional modeling of internal combustion engines (ICEs). A typical example can be found in the prediction of the cycle-to-cycle variability (CCV) in modern, highly downsized gasoline direct injection (GDI) engines, which strongly depends on the accurate simulation of turbulent in-cylinder flow structures. The current standard for turbulence modeling in ICEs is still represented by the unsteady form of Reynold-averaged Navier Stokes equations (URANS), which allows the simulation of full engine cycles at relatively low computational costs. URANS-based methods, however, are only able to return a statistical description of turbulence, as the effects of all scales of motion are entirely modeled. Therefore, during the last decade, scale-resolving methods such as large eddy simulation (LES) or hybrid URANS/LES approaches are gaining increasing attention among the engine-modeling community. In the present paper, we propose a scale-resolving capable modification of the popular RNG k ε URANS model. The modification is based on a detached-eddy simulation (DES) framework and allows one to explicitly set the behavior (URANS, DES or LES) of the model in different zones of the computational domain. The resulting zonal formulation has been tested on two reference test cases, comparing the numerical predictions with the available experimental data sets and with previous computational studies. Overall, the scale-resolved part of the computed flow has been found to be consistent with the expected flow physics, thus confirming the validity of the proposed simulation methodology. View Full-Text
Keywords: internal combustion engines; turbulence modeling; RNG; scale-resolving simulation; cycle-to-cycle variability internal combustion engines; turbulence modeling; RNG; scale-resolving simulation; cycle-to-cycle variability
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Krastev, V.K.; Silvestri, L.; Falcucci, G. A Modified Version of the RNG kε Turbulence Model for the Scale-Resolving Simulation of Internal Combustion Engines. Energies 2017, 10, 2116.

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