The incineration characteristics of waste refrigerant in a combustor were investigated via analyses of flame propagating speed, flammability limit and risen behavior of outwardly propagating spherical flames of R245fa/CH4/O2/N2 mixtures. The Schlieren image processing and matlab code were used for the analysis of flame propagating speed. The asymptotic analysis of linear model based on correlation of stretch ratio versus flame propagating speed was applied for the calculation of unstretched flame propagating speed.
The calculated unstretched flame propagating speed was sequentially decreased with increasing refrigerant concentration in fuel. The flame propagating speed also dramatically was increased with increasing oxygen concentration in oxidation. Overall flame propagating speed of the R245fa mixtures was faster than that of R134a. As concentration of refrigerant increase, the markstein length which means the instability of flame front became negative and risen behavior by buoyancy on spherical flames was observed. The risen behavior can be classified into typical behavior, transition behavior and buoyancy behavior based on the unstretched flame propagating speed. For the study of the rising behavior through figurative analysis of flames, there was a difference between the side flame radius used to calculate a flame propagating speed and figurative flame radius. These reasons are supported by analysis of deformation and stretch of flame surface by buoyancy. As a result of simulation and correlation for the flame propagating speed versus reactants composition, the uncertainty was increased as the buoyancy effect was increased.
In this study, we have confirmed the combustion properties and flammability limits of R245fa/CH4/O2/N2 mixtures and the physical characteristics of risen spherical flames. For comparition with the global warming potentials of reactants and products, the mixed incineration method of collected waste refrigerant gas and methane like R245fa is expected to contribute to the recycling of energy and the reduction of global warming potentials.