Effects of nitrogen addition on vented hydrogen-air deflagration in a vertical duct

In this paper, experiments were performed to investigate the coupling effects of venting and nitrogen addition ratio (x) on flame behavior and pressure evolution during hydrogen -air deflagration within and outside a 1-m-high vertical duct with a vent on its top. Experimental results reveal that x has significant effects on the pressure-time histories in the duct. Helmholtz oscillations of the internal overpressure were observed in all tests, and acoustic type oscillations appears in the tests only for x 1/4 25% and 30%. For a certain x, the maximum overpressure (Pmax) increased with the distance to the vent, i.e., the highest overall explosion overpressure was attained near the duct bottom; however, the difference in Pmax between various measuring points decreases with an increase in x. In all tests, a pressure peak in the duct was observed shortly after external explosion. The maximum internal and external overpressure decreased as x was increased. (c) 2021 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Automated summary

The experiments in this paper investigated the coupling effects of venting and nitrogen addition ratio on flame behavior and pressure evolution during hydrogen-air deflagration in a vertical duct. It was found that the nitrogen addition ratio significantly influenced the pressure-time histories in the duct, and for a certain ratio, the maximum overpressure increased with distance to the vent. Additionally, differences in overpressure between measuring points decreased with an increase in the nitrogen addition ratio.