Investigation of Oxy-Fuel Combustion in a Circulating Fluidized Bed Boiler in Ansys Fluent® Without Incorporation of User Defined Functions
Authors
Jensen, Jakob Bo ; Ranum, Nicolai
Term
4. term
Education
Publication year
2024
Submitted on
2024-05-31
Pages
69
Abstract
Dette projekt undersøger, hvor godt Ansys Fluent kan simulere forbrænding med flerfasestrømning uden at bruge brugerdefinerede funktioner (UDF’er). Flerfasestrømning dækker her blandinger af gas og faste partikler. To metoder til at beskrive partikelbevægelse blev sammenlignet: den diskrete elementmetode (DEM), som sporer individuelle partikler, og den standardbaserede KTGF-model (Kinetic Theory of Granular Flow), som behandler partikler som en granulær strømning. KTGF var lettere at implementere og hurtigere at beregne, mens DEM krævede cirka 20% længere beregningstid. Til kemien blev Eddy-Dissipation valgt frem for den kombinerede Eddy-dissipation/Finite rate, fordi reaktionshastighederne var langsomme; som følge heraf forbrændte de flygtige stoffer (volatiles) ikke i simuleringerne. Fire simuleringer blev sammenlignet med eksperimentelle data: simulering 1 havde en gennemsnitlig afvigelse på 47%, mens simulering 4 havde en afvigelse på 21,6%. Samlet set viser arbejdet, at Fluent kan give rimelige resultater for flerfase-forbrænding uden UDF’er, og at afvigelserne primært skyldes begrænset beregningstid og gitterkvalitet (mesh), ikke fraværet af UDF’er.
This project examines how well Ansys Fluent can simulate combustion with multiphase flow without using User Defined Functions (UDFs). Here, multiphase flow means mixtures of gas and solid particles. Two particle tracking approaches were compared: the Discrete Element Method (DEM), which follows individual particles, and the standard KTGF model (Kinetic Theory of Granular Flow), which treats particles as a granular flow. KTGF was easier to implement and faster to compute, while DEM required about 20% longer computation time. For the combustion chemistry, Eddy-Dissipation was chosen instead of the combined Eddy-dissipation/Finite rate because reaction rates were slow; as a result, the volatiles did not combust in the simulations. Four simulations were compared with experimental data: simulation one showed a mean deviation of 47%, while simulation four had a deviation of 21.6%. Overall, Fluent produced reasonable multiphase-combustion results without UDFs, and the remaining discrepancies are mainly due to limited computation time and mesh (grid) quality rather than the absence of UDFs.
[This summary has been rewritten with the help of AI based on the project's original abstract]
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