The effect of gas jets on the explosion dynamics of hydrogen-air mixtures

In the real scenarios, explosions generally occur under turbulent environments. In this study, the turbulence is generated by introducing inert gas jets, and the interaction between jet turbulence and inert gas dilution is extremely complicated under different conditions. Therefore, the aim of this study is to investigate the influence of gas jets on explosion behavior of hydrogen-air mixtures with various hydrogen concentrations (from 10% to 70%) at different initial pressures (i.e., 50 kPa, 100 kPa, 150 kPa, 200 kPa), and a series of experiments are conducted in a standard 20 L spherical explosion chamber at environmental temperature 300 K. The effect of gas jets on explosions of hydrogen-air mixtures with various hydrogen concentrations at initial pressure of 100 kPa is first studied, the experimental results illustrate that jet has minor impact on the explosion behavior when hydrogen concentration ranges from 20% to 70%. However, the enhancement effect of gas jets on the reaction process is significant as hydrogen concentration is 10%. Therefore, the impact of various gas jets (i.e., CO₂, and N₂) on explosion behavior at different initial pressure is mainly examined as hydrogen-air mixtures are near the lower explosive limits. It is found that the enhancing effect of gas jets on explosion behavior is profound for hydrogen-air mixtures at higher initial pressure, however, the suppression effect caused by the higher concentration of inert gas could balance the promoting effect by turbulence at lower initial pressure. Moreover, the encouraging effect of CO₂ jet is more apparent than that of N₂ jet when jet duration time is relatively short, because the turbulence intensity induced by CO₂ is greater due to its larger molecular weight.