Effect of flame retardant R134a on the flammability characteristics of R1234yf

The potential alternative 2,3,3,3-tetrafluoropropene (R1234yf) has excellent environmental property but carries a risk of combustion. Therefore, 1,1,1,2-tetrafluoroethane (R134a) was chosen as the matching flame retardant. In this research, the oxidation process of R134a/R1234yf was studied by synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS). The oxidation products were identified for the first time, which included CO, CO2, H2O, C2H2, CH2F2 and CH2O. Then, a new kinetic model for the inhibition of R134a on R1234yf combustion was built, which well reproduced the experimental results. The inhibitory effect of R134a on the flammability of R1234yf was evidenced from the microscopic (the molar distributions of typical species and reactions) and macroscopic (adiabatic combustion temperature and laminar burning velocity) properties between pure R1234yf and R134a/R1234yf mixture. The comparative Rates of Production (ROP) analysis for key species (H2O, CO2, C2H2 and CH2F2) and radicals (H, O, OH and F), alongside sensitivity analysis were performed, which elucidated the microscopic mechanism in the flame retarding process. The results also showed that the laminar burning velocity and adiabatic temperature of pure R1234yf were larger than R134a/R1234yf mixture. This paper can provide a new research idea for the safe application of environmentally friendly refrigerants.