Experimental and chemical kinetics study on the flammability limit of CO2/C3H6 mixture working fluid at variable initial temperature

CO2/C3H6 mixture has a wide range of applications in refrigeration systems, heat pumps and Organic Rankine Cycle (ORC) systems, but its flammability safety needs to be considered. An experimental and computational investigation has been conducted on the determination of the flammability limits of CO2/C3H6 and on the understanding of associated limit phenomena in general. We tested the flammable zone of CO2/C3H6 at variable initial temperature. The accuracy of the prediction model of calculation adiabatic flame temperature were verified based on the experimental data. Meanwhile, a high-speed camera was used to record the process of CO2 suppression of flame propagation near flammability limit. Furthermore, based on kinetic numerical calculation, the effect of CO2 chemical and thermal on the flammability limit of C3H6 were analyzed. The results show that the thermal effect of CO2 is greater than that of chemical effect near the flammability limit. The theory of chemical reactivity inhibition reduces the yield and molar ratio of key radicals. The addition of CO2 can inhibit the activity of the dominant chain and increase the activity of the dominant chain termination reaction in the global combustion kinetics. Results of this study provide theoretical guidance for the safe application of CO2/C3H6 mixture.