Comparative study on ignition characteristics of styrene and ethylbenzene behind reflected shock waves

Experimental and numerical research is performed on the ignition delay times for both styrene and ethylbenzene at reflected pressures of 2, 4, and 10 atm; temperature range of 1165 K ∼ 1670 K, equivalence ratios of 0.5, 1.0, and 1.5; and fuel concentrations of 0.25, 0.5, and 1.0 in a shock tube. The experimental results show that styrene is more reactive at high temperatures, but the oppsite is true at low temperatures. The chemical kinetic mechanisms for styrene and ethylbenzene are modified based on three kinetic models as proposed by MetacYuan et al., Comandini et al., and LLNL. The modified mechanism gives a good prediction to the presented experimental data. The reaction pathway analysis reveals that ethylbenzene is consumed primarily by the unimolecular decomposition of ethylbenzene to benzyl at high temperatures, while H-abstraction reactions are dominated in the consuming routes of ethylbenzene at low temperatures. For styrene, the H-abstraction reaction is dominated in both high and low temperatures. It is found that the reactions relevant to benzyl have significant inhibitor effects on the ignition delay times for the two test fuels using sensitivity analyses. It is concluded that different concentrations of benzyl radicals result in various ignition delay times of styrene and ethylbenzene.