Experimental and simulation analysis of the explosive behavior and free radical spectroscopic characteristics of R1233zd(E)/R290 mixed gas.

To explore the combustion safety characteristics of environmentally friendly mixed refrigerants, this study systematically investigates the impact and mechanism of R1233zd(E) on the explosion behavior of R290 through a combination of experiments, spectral analysis, and density functional theory calculations. The results indicate that R1233zd(E) has a significant dual effect on the combustion process of R290: when the volume fraction ratio of R1233zd(E)/R290 is ≤ 0.2, it exhibits a slight promoting effect, with the pressure peak and maximum pressure rise rate increasing by 1.86% and 17.16%, respectively, the flame propagation speed increasing by 0.418 m/s, and the CH* peak time advancing by 8.33%. However, when the volume fraction exceeds 1.1, a significant inhibiting effect is observed. At a volume fraction of 1.6, the pressure peak and maximum pressure rise rate decrease by 56.08% and 82.97%, respectively, the time to reach the explosion pressure peak is extended by 155.54%, the flame propagation speed is only 17% of that of pure R290, and the peak times of OH* and H2O* are delayed by 446.15%. Furthermore, as the concentration of R1233zd(E) increases, the intensity peak times of key reactive radicals/molecules CH*, OH*, H2O* and O2* exhibit exponential growth, and when the volume fraction is ≤ 1.1, the transition process from CO to CO₂ is delayed. Simultaneously, theoretical calculations and flameretardant radical spectra indicate that R1233zd(E) preferentially cleaves the C–Cl bond to generate chlorine radicals, which effectively capture reactive radicals, becoming the dominant factor in blocking chain reactions.