Porovnání SAS modelu turbulence s SST k-omega v simulaci difuzního spalování

Comparison of SAS Turbulence Model to the SST k-omega in Non-Premixed Combustion Simulation

miscellaneous

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Scale-Adaptive Simulation (SAS) enhances capabilities of Unsteady Reynolds-Averaged Navier-Stokes (URANS) to capture decay of large eddies in unsteady flows. SAS behaves like a LES in unsteady solutions with lower demand for local grid spacing. Its main effect is in restricting turbulent viscosity and consequently increasing velocity fluctuation. Such a effect is significant for predictions of chemical reactions and mixing when eddy dissipation model is incorporated. The reason is that this model is strongly bounded to the turbulence predictions. In the present paper the effect of SAS procedure is compared to the traditional SST k-omega turbulence model on the case of non-premixed swirling staged natural gas combustion in a confined environment of water cooled combustor. The aim is to provide accurate local wall heat flux predictions in industrial combustors at the end. The ability to predict local wall heat fluxes is highly relevant for engineering purposes as these fluxes are often the main results required by designers of fired heaters, boilers and combustion chambers.

Scale-Adaptive Simulation rozšiřuje možnosti Unsteady Reynolds-Averaged Navier-Stokes přístupu k predikci rozkladu velkých vírů v nestacinárním proudění. Chování SAS modelu je podobné s LES při nestacionárním řešení s nižším nárokem na rozměry a velikost výpočetní sítě. Hlavní vlastností modelu je v omezení turbulentní viskozity a následnému navášení fluktuací rychlosti. Tento jev je významný při predikcích chemických reakcí a promíchávání za použití "eddy dissupation" modelu z důvodů jeho úzké vazby na predikci turbulence. V této prácí je porovnáván vliv SAS modelu s modelem turbulence SST k-omega pro simulaci difúzního vířivého spalování se stupňovitým přívodem zemního plynu.

Scale-Adaptive Simulation (SAS) enhances capabilities of Unsteady Reynolds-Averaged Navier-Stokes (URANS) to capture decay of large eddies in unsteady flows. SAS behaves like a LES in unsteady solutions with lower demand for local grid spacing. Its main effect is in restricting turbulent viscosity and consequently increasing velocity fluctuation. Such a effect is significant for predictions of chemical reactions and mixing when eddy dissipation model is incorporated. The reason is that this model is strongly bounded to the turbulence predictions. In the present paper the effect of SAS procedure is compared to the traditional SST k-omega turbulence model on the case of non-premixed swirling staged natural gas combustion in a confined environment of water cooled combustor. The aim is to provide accurate local wall heat flux predictions in industrial combustors at the end. The ability to predict local wall heat fluxes is highly relevant for engineering purposes as these fluxes are often the main results required by designers of fired heaters, boilers and combustion chambers.

CFd, vířivé proudění, spalování, vířič, model turbulence

CFD, Swirl flow, Combustion, Swirler, Turbulence Model

01.09.2013

Lyon, Francie

Proceedings of 14th European Turbulence Conference

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