A series of 11 large scale experiments was performed at the HYKA test site in order to experimentally simulate different flame propagation regimes in a stratified hydrogen-air atmosphere. The total volume of the facility is equal to 220 m3 with an aspect ratio H/D=1.5. Hydrogen concentration was kept constant (7% vol. in air) for all the experiments. Combustion of a stratified hydrogen-air mixture with different steepness of hydrogen concentration gradient (I: 10=>7=>4% H2; II: 12=>7=>2% H2; III: 14=>7=>0% H2) was investigated and then compared to uniform (7% H2) mixture combustion using Background Oriented Schlieren (BOS) method combined with high speed camera, pressure and temperature measurements. The mixture was ignited in the center. Ambient initial conditions were 293 K and 1 bar in the tests. Two tests with water spray suppression system demonstrated not a mitigation efficiency but even promote the combustion process due to the generation of highly turbulent flow. The experimental results demonstrate that the highest hydrogen concentration at the top of the containment plays a governing role in combustion process leading to much higher combustion pressure and temperature compared to the combustion of uniform mixture of the same amount of hydrogen in the volume (equal to 7% H2).

International Seminar on Fire and Explosion Hazards (9; 2019; Saint Petersburg, Russia). Proceedings of the Ninth International Seminar on Fire and Explosion Hazards [Электронный ресурс]: 21-26 April 2019, Saint Petersburg, Russia. Vol. 2 / Peter the Great St. Petersburg Polytechnic University, Autonomous Non-Profit Organization "Fire and Explosion Safety", Gefest Holding Ltd ; [edited by A. Snegirev [et al.]. — Электрон. текстовые дан. (1 файл : 98,7 Мб). — Saint Petersburg, 2019. — Загл. с титул. экрана. — Свободный доступ из сети Интернет (чтение, печать, копирование). — Adobe Acrobat Reader 7.0. — <URL:http://elib.spbstu.ru/dl/2/k19-97.pdf>. — <URL:http://doi.org/10.18720/SPBPU/2/k19-97>.