Influence of hydrogen concentration on the pressure oscillation and flame propagation during vented deflagration of hydrogen-air mixtures.

The vented deflagration of hydrogen-air mixture is studied with the influence of hydrogen concentration. The pressure oscillation and flame propagation mechanism are investigated by analyzing the internal and external pressure histories and flame propagation images. The experimental results present that the pressure oscillation phenomenon has a great effect on the internal pressure peak. All of the internal pressure curves present the remarkable pressure oscillation. The pressure oscillation curve is processed by the fast Fourier transform(FFT) method. The internal pressure peaks of origin curves are higher than the results of the FFT filter curves, especially the fuel-rich conditions. The internal pressure peak of origin curve increases with the increase of the hydrogen concentration(c (H 2)) approximatively, but the filtered internal pressure peak increases first and then decreases as c (H 2). The duration of the external pressure rise is significantly shorter than the internal results. The external pressure curves have one or two pressure peaks. The external pressure histories just have one peak as c (H 2) ranging from 15 vol% to 25 vol%. But the external pressure histories turn out to two peaks as c (H 2) is more than 30 vol%. It can be found that the duration of the internal pressure history increases monotonically with the decrease of c (H 2). The duration of external flame propagation is contrary to the duration of internal pressure history in the change rule. The duration of external flame propagation increases with the increase of c (H 2). The external explosion phenomenon can be found as c (H 2) is higher than 30 vol%. And the backdraft phenomenon in external flame propagation process can be found as c (H 2) is higher than 40 vol%. • The pressure oscillation phenomenon has a significant impact on the internal overpressure peak. • The duration of the external pressure rise is significantly shorter than the internal results. • The external explosion phenomenon can be found as c (H 2) is higher than 30 vol%. • The backdraft phenomenon can be found as c (H 2) is higher than 40 vol%. [ABSTRACT FROM AUTHOR]