A Generic Gas Radiative Property Model Applicable to CFD Simulations of all Combustion Processes
Author
Singh, Shashank
Term
4. term
Education
Publication year
2016
Submitted on
2016-06-09
Pages
146
Abstract
This thesis addresses the need for a generic gas radiative property model that can be applied across combustion processes in CFD. The authors develop a computationally efficient Exponential Wide Band Model (E-EWBM) in C++ to calculate gas-mixture emissivity and validate the code against reference data. The model is compared with established weighted-sum-of-gray-gas models and other EWBM formulations, and is implemented in ANSYS Fluent. Through 12 CFD simulations under air–fuel and oxy-fuel conditions, the work examines how radiation models and global reaction mechanisms affect absorption coefficient, temperature, velocity, and species fields. The results indicate that E-EWBM produces a significant change in the predicted absorption coefficient, while its impact on temperature, axial velocity, and species is limited; by contrast, the choice of reaction mechanism has a pronounced influence. In oxy-fuel cases, a similarly notable effect on the absorption coefficient is observed, supported by a 3D mesh created in ICEM CFD. The study demonstrates the applicability of a generic gas radiation model in CFD and outlines directions for future work.
Dette speciale adresserer behovet for en generisk model for gasstrålings-egenskaber, der kan anvendes på tværs af forbrændingsprocesser i CFD. Forfatterne udvikler en beregningsmæssigt effektiv Exponential Wide Band Model (E-EWBM) i C++ til at beregne emissivitet for gasblandinger og validerer koden mod referencegrundlag. Modellen sammenlignes med etablerede vægtet-sum-af-grå-gas-modeller og andre EWBM-formuleringer og implementeres i ANSYS Fluent. Gennem i alt 12 CFD-simuleringer under luft-brændsel og oxy-fuel betingelser undersøges effekten af strålingsmodeller og globale reaktionsmekanismer på absorptionskoefficient, temperatur, hastighed og artsfraktioner. Resultaterne viser, at E-EWBM giver en markant ændring i beregnet absorptionskoefficient, mens temperatur, aksialhastighed og artsfordelinger påvirkes begrænset af valget af strålingsmodel; derimod har valget af reaktionsmekanisme en tydelig indflydelse. I oxy-fuel tilfælde observeres også en markant effekt på absorptionskoefficienten, understøttet af en 3D-mesh opbygget i ICEM CFD. Arbejdet demonstrerer anvendeligheden af en generisk gasstrålingsmodel i CFD og peger på fremtidige udvidelser.
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