Experimental investigation on vented hydrogen explosion in synergetic application of hydrogen concentration and pipe length

Abstract

The combined effect of pipe length and hydrogen concentration may influence the energy output mechanism of vented hydrogen explosions. High-speed photography system and pressure acquisition device were utilized to collect data regarding vented hydrogen explosions under diverse conditions. Experimental results demonstrated that the coupling effects of hydrogen concentration and pipe length exhibited significant correlations in flame propagation and pressure dynamics. When the hydrogen concentration was 30 %, the flame area increased linearly from 952 cm² to 1834 cm² as the pipe length extended from 100 mm to 1000 mm. In contrast, at 50 % hydrogen concentration, the flame area reached its maximum value of 1340 cm² in a 500 mm-long pipe before diminishing with longer duct configurations. Pressure measurements revealed distinct constraint effects: Under 30 % hydrogen concentration, the internal overpressure escalated significantly from 0.54 MPa (100 mm) to 0.68 MPa (1000 mm). Distinctively, a secondary pressure peak emerged in 50 % hydrogen scenarios, indicating potential external explosion hazards. Mechanistic analysis suggested that for hydrogen-rich mixtures (50 %), limiting pipe length to 500 mm effectively controled flame area below 1340 cm². Regarding near-stoichiometric conditions (30 %), maintaining pipe lengths shorter than 100 mm restricted internal overpressure below 0.54 MPa.