Investigation on Cooling Effect of Water Sprays on Tunnel Fires of Hydrogen

As one of the most promising renewable green energies, hydrogen power is a popularly accepted option to drive automobiles. Commercial application of fuel cell vehicles has been started since 2015. More and more hydrogen safety concerns have been considered for years. Tunnels are an important part of traffic infrastructure with a mostly confined feature. A hydrogen leak followed possibly by a hydrogen fire is a potential accident scenario, which can be triggered trivially by a car accident while hydrogen-powered vehicles operate in a tunnel. Water spray is recommended traditionally as a mitigation measure against tunnel fires. The interaction between water spray and hydrogen fire is studied by way of numerical simulations. By using the computer program of Fire Dynamics Simulator (FDS), tunnel fires of released hydrogen in different scales are simulated, coupled with water droplet injections featured in different droplet sizes or varying mass flow rates. The cooling effect of spray on hot gases of hydrogen fires is apparently observed in the simulations. However, in some circumstances, the turbulence intensified by the water injection can prompt hydrogen combustion, which is a negative side effect of the spray.