Large-scale experimental study of open, impinging and confined hydrogen jet fires
Christoph Meraner, Reidar Stølen, Ellen Synnøve Skilbred, Tian Li
Abstract
Hydrogen tanks used in transportation are equipped with thermal pressure relief devices to prevent a tank rapture in case of fire exposure. The opening of the pressure relief valve, in such a scenario, would likely result in an impinging and (semi-) confined hydrogen jet fire. Therefore, twelve large-scale experiments of hydrogen jet fires and one large-scale propane reference experiment have been conducted with various degrees of confinement, orientations of the jet, and distances from the nozzle to the impinging surface. Infrared and visible light videos, temperatures, heat fluxes, and mass flow rate of hydrogen or propane were recorded in each experiment. It was found that the hydrogen flame can be visible under certain conditions. The main difference between an open impinging jet and an enclosed impinging jet fire is the extent of the high-temperature region in the steel target. During the impinging jet fire test, 51% of the exposed target area exceeded 400°C, while 80% of the comparable area exceeded 400°C during the confined jet fire test. A comparison was also made to an enclosed propane jet fire. The temperature distribution during the propane fire was more uniform than during the hydrogen jet fire, and the localized hot spot in the impact region, as seen in the hydrogen jet fires, was not recorded. • The visibility of hydrogen jet fires depends highly on the surrounding condition, ranging from a visible yellow flame to a completely invisible flame. • Hydrogen flames lead to a hotspot close to the jet impingement area. • Increasing confinement does not affect the hotspot temperature but increases the target's high-temperature area. • The temperature at the impingement is highly dependent on the flame length in relation to the target distance. • The heat flux outside the impinging hydrogen flame is low.