Experimental and mechanism study on the flammability of the mixtures of propylene and ethane

In the background of the global promotion of green and low-carbon transition, more attention should be paid to the combustion characteristics of environmentally friendly but flammable working fluids. This study delves into the flammability of mixtures composed of propylene (R1270) and ethane (R170) with 1,1,2,3,3,3-hexafluoro-1-propene (R1216) and 1,1,1,2-tetrafluoroethane (R134a). The flammability limit ranges of these four mixtures were measured at different concentrations. The flammability inhibition effects of R1216 and R134a on hydrocarbon (HC) working fluid R1270 were then compared and analysed under different temperature conditions. Additionally, the density functional theory (DFT) method was employed to analyse the interaction mechanisms of HCs/R1216 and HCs/R134a. The results show that, firstly, low proportional concentrations of R1216 and R134a widen the flammability limit ranges of mixtures HCs/R1216 and HCs/R134a. Moreover, elevated temperatures not only promote the combustion reactions of HCs but also facilitate the thermal decomposition reactions of R1216 and R134a. However, HCs are more sensitive to temperature changes. Therefore, the flammability limit range of mixtures expands as the temperature rises. Secondly, a combination of theoretical calculations and experiments demonstrates that R134a exhibits better physical flame retardancy than R1216, while the chemical flame retardancy of R1216 is superior to that of R134a. These results provide a valuable reference for the safe application of hydrocarbon working fluids.