Effects of soot absorption coefficient–Planck function correlation on radiative heat transfer in oxygen-enriched propane turbulent diffusion flame

Author(s):  
J.L. Consalvi ◽  
F. Nmira
Author(s):  
Mannedhar Reddy ◽  
Ashoke De

In the present work, two different turbulent diffusion flames are investigated for soot predictions using the presumed shape multi-environment Eulerian PDF (EPDF) as turbulence-chemistry closure. In this approach, the chemical equation is represented by multiple reactive scalars and finite number of Delta functions are used to describe the shape of joint composition PDF, while the truncated series expansion in spherical harmonics (P1 approximation) is used to solve the radiative heat-transfer equation. The absorption coefficient is modeled using the weighted sum of gray gases model (WSGG) considering four fictitious gases. The soot volume fraction is predicted using acetylene based soot inception model (Moss-Brookes model). The model accounts for inception, surface growth and oxidation processes of soot. An equilibrium based approach is used to determine the OH radical concentration, required for soot oxidation. A single variable PDF in terms of temperature is used to include the turbulence-chemistry effects on soot. An effective absorption coefficient is calculated to include the influence of radiative heat transfer on soot. The combined tool is used to determine the soot formation in two hydrocarbon flames (Delft flame III, pilot stabilized natural gas flame and an unconfined C2H4/air jet flame). The soot formation rate decreases with the inclusion of radiation for both the flames and indicate the need for delineation of radiative heat transfer. The effects of soot-turbulence interaction are consistent with available literature. The effect of collision efficiency on oxidation rate can be clearly explicated from the predictions of C2H4/air flame.


2001 ◽  
Vol 1 (1) ◽  
pp. 64
Author(s):  
Victoria Echaniz ◽  
Eduardo Brizuela

En este trabajo se resuelve por el método de los volúmenes finitos, y aplicando un Esquema de Reacción Reducido y conceptos de Eddy Break Up, la combustión de gas natural en aire en una caldera de vapor. Se presentan resultados de la simulación de una llama de difusión turbulenta, en escala natural y condiciones operacionales, con transmisión de calor por conducción/convección y radiación. Por tratarse de una tarea en progreso y de largo alcance que involucra una caldera en servicio los resultados son preliminares y la comparación con resultados experimentales es limitada. No obstante, los resultados obtenidos son considerados satisfactorios, aunque indican que es necesario continuar refinando los modelos de mezclado y radiación para reproducir mejor las condiciones reales. ABSTRACT Combustion of natural gas in air in a utility boiler is simulated by means of a finite volume approach, using a Reduced Reaction Scheme and Eddy Break Up concepts. Results are presented for a turbulent diffusion flame, under operational conditions and in full size, including heat transfer by conduction/convection and radiation. Preliminary results only are presented and a limited comparison with experimental results is made due to the scope of the task which involves a facility in service. Nevertheless, results are considered satisfactory, although there are indications that it is necessary to continue refining the mixing and radiation models for better matching with operational conditions.


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