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Computational Modeling of Turbulent Swirling Diffusion Flames
Vondál, Jiří ; Klemeš,, Jiří (oponent) ; Tuček,, Antonín (oponent) ; Hájek, Jiří (vedoucí práce)
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. The aim of this work is to provide reliable data measured by an innovative method for the case of swirling diffusion natural gas flames and consequently utilize the data for validation of Computational Fluid Dynamic simulations represented by commercial solver ANSYS Fluent® 12.1. The subject is a large-scale combustion chamber with a staged-gas industrial type low-NOx burner at two thermal duties, 745 kW and 1120 kW. Attention is paid to the evaluation of boundary conditions via additional measurement or simulation, such as wall emissivity and wall temperature. Several in-house software codes were created for computational support. Remarkable results were obtained for low firing rate where prediction reached accuracy up to 0.2 % in total extracted heat and better than 16 % in local wall heat flux in individual sections. However, for high firing rate the accuracy significantly decreases. Consequently close attention was paid to the confined swirling flow phenomena downstream of the swirl generator. There were identified several problematic points in the prediction capabilities of utilized computationally capable, industry-standard models.
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