scholarly journals The effect of preferential diffusion on soot formation in a laminar ethylene/air diffusion flame

2010 ◽  
Vol 15 (1) ◽  
pp. 125-140 ◽  
Author(s):  
Hongsheng Guo ◽  
Gregory J. Smallwood
2006 ◽  
Vol 145 (1-2) ◽  
pp. 324-338 ◽  
Author(s):  
Hongsheng Guo ◽  
Fengshan Liu ◽  
Gregory J. Smallwood ◽  
Ömer L. Gülder

Author(s):  
Fengshan Liu ◽  
Francesca Migliorini ◽  
Francesco Cignoli ◽  
Silvana De Iuliis ◽  
Giorgio Zizak

Numerical and experimental studies were conducted to investigate the effects of hydrogen and helium addition to fuel on soot formation in atmospheric axisymmetric coflow laminar methane-air diffusion flame. Soot temperature and volume fraction distributions were measured using a two-dimensional two-color technique. Numerically the conservation equations of mass, momentum, energy, and species in the limit of low-Mach number were solved. Detailed gas-phase chemistry and thermal and transport properties were accounted for. Radiative heat transfer by CO, CO2, H2O, and soot was calculated using the discrete-ordinates method with the radiative properties of the mixture obtained from a wide-band model. Soot was modeled using a two-equation semi-empirical model in which the mechanisms for inception and surface growth are assumed to be PAH coagulation and H-abstraction acetylene addition. Both experimental and numerical results show that helium addition is more efficient than hydrogen addition in reducing soot formation in the methane flame. These results are different from the previous investigations in ethylene flames where the hydrogen addition was found to be more effective in reducing soot formation than helium addition due to the additional chemical suppression of hydrogen on soot. It is suggested here that hydrogen chemically enhances soot formation when added to methane.


Author(s):  
Fengshan Liu ◽  
Wenjun Kong

The effect of the central air flow rate on the structure and sooting characteristics of a laminar double coflow methane/air diffusion flame was experimentally observed and recorded by a digital camera. The double diffusion flame was generated using a modified Gu¨lder laminar coflow diffusion flame burner by introducing an air flow in the centre of the fuel pipe. Numerical calculations of the double diffusion flame at different central air flow rates were conducted by solving the elliptic conservation equations of mass, momentum, species, and energy in axisymmetric cylindrical coordinates using a standard control volume method. Detailed multi-component thermal and transport properties and detailed combustion chemistry were employed in the modelling. Soot formation was modeled using a semi-empirical acetylene based model in which two transport equations for soot mass fraction and soot number density per unit mass were solved. Thermal radiation was calculated using the discrete-ordinates method and a 9-band non-grey model for the radiative properties of the CO-CO2-H2O-soot mixture. The numerical model reproduced qualitatively the experimental observations of the effect of central air flow rate on the structure and sooting characteristics.


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