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Numerical investigation of cyclic variations in gasoline engines using a hybrid URANS/LES modeling approach

Hasse, C. and Sohm, V. and Durst, B. (2010):
Numerical investigation of cyclic variations in gasoline engines using a hybrid URANS/LES modeling approach.
In: Computers & Fluids, pp. 25-48, 39, (1), DOI: 10.1016/j.compfluid.2009.07.001, [Online-Edition: https://doi.org/10.1016/j.compfluid.2009.07.001],
[Article]

Abstract

Cycle to cycle variations are an important aspect in the development and optimization process of internal combustion engines. In this study the feasibility of using a detached eddy simulation (DES) SST model, which is a hybrid URANS/LES model, to predict cycle to cycle variations is investigated. In the near wall region or in regions where the grid resolution is not sufficiently fine to resolve smaller structures, the two-equation RANS shear-stress transport (SST) model is used. In the other regions with higher grid resolution an LES model is applied. First, the numerical requirements associated with the hybrid URANS/LES and the employed solver are studied in detail. The numerical dissipation of the spatial scheme and the choice of the temporal scheme including the step size are evaluated. In addition, the accuracy of the solver for moving meshes, which are required for engine calculations, is assessed. The modeling constant linking the grid size to the DES filter length scale is determined by calculating a decaying homogeneous isotropic turbulence test case for different grid resolutions. The final applications of the model are two different engine cases with increasing complexity. The first case is the statistically stationary flow through an engine intake port. The time resolved flow structure predicted by the DES SST model is analyzed and the resulting time-averaged velocity fields are compared to experimental data at different locations. The second application is a motored multi-cycle simulation of a series production engine. The instantaneous flow development during the intake and compression stroke of one single cycle is studied and the ensemble-averaged and the instantaneous velocity fields as well as the resolved velocity fluctuations are compared to optical measurements. Special emphasis is placed on the cyclic differences of the velocity fluctuations at the time of ignition in the vicinity of the spark plug and the expected influence on the combustion process. 2009 Elsevier Ltd. All rights reserved.

Item Type: Article
Erschienen: 2010
Creators: Hasse, C. and Sohm, V. and Durst, B.
Title: Numerical investigation of cyclic variations in gasoline engines using a hybrid URANS/LES modeling approach
Language: German
Abstract:

Cycle to cycle variations are an important aspect in the development and optimization process of internal combustion engines. In this study the feasibility of using a detached eddy simulation (DES) SST model, which is a hybrid URANS/LES model, to predict cycle to cycle variations is investigated. In the near wall region or in regions where the grid resolution is not sufficiently fine to resolve smaller structures, the two-equation RANS shear-stress transport (SST) model is used. In the other regions with higher grid resolution an LES model is applied. First, the numerical requirements associated with the hybrid URANS/LES and the employed solver are studied in detail. The numerical dissipation of the spatial scheme and the choice of the temporal scheme including the step size are evaluated. In addition, the accuracy of the solver for moving meshes, which are required for engine calculations, is assessed. The modeling constant linking the grid size to the DES filter length scale is determined by calculating a decaying homogeneous isotropic turbulence test case for different grid resolutions. The final applications of the model are two different engine cases with increasing complexity. The first case is the statistically stationary flow through an engine intake port. The time resolved flow structure predicted by the DES SST model is analyzed and the resulting time-averaged velocity fields are compared to experimental data at different locations. The second application is a motored multi-cycle simulation of a series production engine. The instantaneous flow development during the intake and compression stroke of one single cycle is studied and the ensemble-averaged and the instantaneous velocity fields as well as the resolved velocity fluctuations are compared to optical measurements. Special emphasis is placed on the cyclic differences of the velocity fluctuations at the time of ignition in the vicinity of the spark plug and the expected influence on the combustion process. 2009 Elsevier Ltd. All rights reserved.

Journal or Publication Title: Computers & Fluids
Volume: 39
Number: 1
Uncontrolled Keywords: Combustion pro-cess; Compression stroke; Cycle to cycle variation; Cyclic variations; Detached eddy simulations; Engine intake; Experimental data; Filter length; Gasoline engines; Grid resolution; Grid size; Homogeneous isotropic turbulence; Instantaneous flow; Modeling approach; Moving mesh; Multi-cycle; Near-wall region; Numerical dissipation; Numerical investigations; Optical measurement; Optimization process; Series production; Shear-stress transport; Single cycle; Spatial scheme; Stationary flow; Step size; Temporal scheme; Test case; Time-averaged velocity field; Time-resolved; Two-equation; Velocity field; Velocity fluctuations, Atmospheric temperature; Engines; Flow interactions; Ignition; Internal combustion engines; Optical data processing; Submarine geophysics; Turbulent flow; Velocity, Simulators
Divisions: 16 Department of Mechanical Engineering > Simulation of reactive Thermo-Fluid Systems (STFS)
16 Department of Mechanical Engineering
Date Deposited: 29 Nov 2017 09:43
DOI: 10.1016/j.compfluid.2009.07.001
Official URL: https://doi.org/10.1016/j.compfluid.2009.07.001
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