Experimental Study of Light Gas Dispersion in a Channel

Usage of hydrogen as fuel gives rise to possible accidental risks due to leakage and dispersion. A risk from hydrogen leak is the formation of a large volume of the hydrogen-air mixture, which could be ignited and leading up to a severe explosion. Prevention and control of formation and ignition of combustible hydrogen cloud necessitate sufficient knowledge of mechanisms of the hydrogen leak, dispersion, ignition, and over-pressures generated during combustion. This paper aims to investigate the momentum-controlled jet, the buoyancy-controlled wave and the parameters influencing hydrogen concentration distribution in an elongated space. It demonstrates experimental results and analysis from helium and hydrogen dispersion in a channel. A set of experiments were carried out for the release of helium and hydrogen jets in a 3 m long channel to record their concentrations in the cloud by concentration sensors at different horizontal and vertical positions. Flow visualization technique was applied using shadowgraph to image the mixing process next to the release point and the helium-, hydrogen-air cloud shape at the middle of the channel. Moreover, results were used for comparison of helium and hydrogen concentration gradients. The results of the experiments show that swift mixing occurs at higher flow rates, smaller nozzle sizes, and downward release direction. Higher concentration recorded in the channel with negative inclination. Results also confirmed that hydrogen/helium behavior pattern in the channel accords with mutual intrusion theory about gravity currents.