Study on combustion and ignition characteristic of weakly flammable refrigerant R125 using a micro flow reactor with a controlled temperature profile

A mixture refrigerant R410A is being used throughout the world. In order to develop a standard for the safe usage of R410A refrigerant, there is a need to understand the flammability properties of R410A components (R32 and R125). In this study, ignition characteristics of a stoichiometric C2HF5/air (R125) mixture were experimentally and computationally investigated by a micro flow reactor with a controlled temperature profile at atmospheric pressure. The experimental C2HF5 weak flame has two luminous regions in the case of a maximum wall temperature of 1300 K. The HRR profile of C2HF5/air flame has two heat release zones in computation with Linteris mechanism. As a results, the experimental and computational weak flame of a stoichiometric C2HF5/air mixture shows multi-stage oxidation at a maximum wall temperature of 1300 K although agreements between experimental luminosity profile and computational HRR profile are not satisfactory at this stage. Based on the obtained flame structure, a maximum wall temperature of 1300 K is found to be insufficient to attain the complete oxidation of a stoichiometric C2HF5/air mixture. Therefore, an additional computation with the maximum wall temperature of 2000 K was conducted. As a result, there exist three heat release zones in this case. First zone mainly corresponds to fuel decomposition less than 1350 K. Second zone is the region which produces CF4 from CF3. Third zone corresponds to CO oxidation. Reaction path analysis of key species was conducted. This analysis clarified dominant production and consumption reaction of key species, and reactions with heat release by each stage of oxidation process of C2HF5/air mixture.