Numerical and experimental study on biased tube temperature problem in tangential firing boiler

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>In this study, a numerical and experimental investigation on the flow field in a 500-MW unit of a tangentially fired boiler has been performed to understand the effect of residual swirl on the temperature distribution and inconsistency of flow velocity in the crossover pass. The k–k<SUB>L</SUB>–ω turbulence model was used in this study to analyse the possible formation of transition flow in the tangential firing boiler. Furthermore, 1D and 3D hybrid modelling were used for the simulation of the convective heat transfer in the boiler tube assembly. The commercially available code ANSYS Fluent and COMSOL were used for the studies, respectively. The numerical results for the velocity profile and residual swirl in the boiler were validated using the experimental results from the cold air velocity test, in which the flow velocity was directly measured in the full-scale boiler. The computational results agreed well with the experimental findings. Furthermore, from a comparison of the simulation and experiment, it was found that the biased gas flow induces non-uniform tube temperatures at the crossover pass area of the tangential firing boiler. These results aid in the detailed study of the residual swirl effects on the temperature or flue gas at various locations of the boiler. This study indicates that a non-uniform tube temperature at the crossover pass is an inherent problem resulting from residual swirl in the tangential firing boiler. Therefore, the pulverised coal burner should be fine-tuned to avoid tube rupture due to local overheating.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A full-scale CFD simulation was performed for a 500-MW unit of a tangentially fired boiler to determine the flow behaviour. </LI> <LI> The CFD model was validated with experimental results from the cold air velocity test. </LI> <LI> Temperatures of the boiler tube were measured directly in commercial tangential firing boilers. </LI> <LI> Biased temperature profile of the steam and tube is attributed to the non-uniform velocity of the flue gas. </LI> </UL> </P>