“…Simulations were conducted with the KIVA-4mpi code [52,53]. For this work it has been extended to compute the combustion process with the DTFM [54] in combination with FGM tabulated chemistry [55,56] as detailed in Section 3.2.…”
This work shows experiments and simulations of the fired operation of a spark ignition engine with port-fueled injection. The test-rig considered is an optically accessible single cylinder engine specifically designed at TU Darmstadt for the detailed investigation of in-cylinder processes and model validation. The engine was operated under lean conditions using isooctane as a substitute for gasoline. Experiments have been conducted to provide a sound database of the combustion process. A planar flame imaging technique has been applied within the swirl and tumble plane to provide statistical information on the combustion process to complement the pressure-based comparison between simulation and experiments. This data is then analyzed and used to assess the Large Eddy Simulation performed within this work. For the simulation, the engine code KIVA has been extended by the dynamically thickened flame model combined with chemistry reduction by means of pressure dependent tabulation. 60 cycles have been simulated to perform a statistical evaluation. Based on a detailed comparison with the experimental data, a systematic study has been conducted to obtain insight into the most crucial modeling uncertainties.
“…Simulations were conducted with the KIVA-4mpi code [52,53]. For this work it has been extended to compute the combustion process with the DTFM [54] in combination with FGM tabulated chemistry [55,56] as detailed in Section 3.2.…”
This work shows experiments and simulations of the fired operation of a spark ignition engine with port-fueled injection. The test-rig considered is an optically accessible single cylinder engine specifically designed at TU Darmstadt for the detailed investigation of in-cylinder processes and model validation. The engine was operated under lean conditions using isooctane as a substitute for gasoline. Experiments have been conducted to provide a sound database of the combustion process. A planar flame imaging technique has been applied within the swirl and tumble plane to provide statistical information on the combustion process to complement the pressure-based comparison between simulation and experiments. This data is then analyzed and used to assess the Large Eddy Simulation performed within this work. For the simulation, the engine code KIVA has been extended by the dynamically thickened flame model combined with chemistry reduction by means of pressure dependent tabulation. 60 cycles have been simulated to perform a statistical evaluation. Based on a detailed comparison with the experimental data, a systematic study has been conducted to obtain insight into the most crucial modeling uncertainties.
“…The equations are solved in two stages allowing an implicit solver for the diffusion, and an explicit quasi-second order upwind scheme for the advection [35]. The code has been validated and compared to experimental data in a previous study [28], where details of the parallel efficiency and the numerical schemes were also provided.…”
Large-eddy simulation of the reacting flow field in a combustion-based mitigation system to reduce the emissions of methane contained in ventilation air methane is presented. The application is based on the preheating and combustion of ventilation air methane. Effects of preheating and methane concentration are examined in five computational cases. The results indicate that the oxidation of the ventilation air methane can take place in a co-annular jet configuration provided that the preheating temperature is as high as 500 K for mixtures containing a low methane concentration of 0.5%. It is found that the oxidation process that eventually leads to reaction and combustion is controlled by the methane concentration and the level of preheating.
“…Similarly to other open-source and commercial CFD solutions aimed at ICE modeling [33][34][35], the OpenFOAM numerical framework is essentially built on top of a second-order, pressure-based finite-volume methodology.…”
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.
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