CFD Study for Mitigation of H2 Explosion Inside Gas Turbine Enclosure

There are several potential sources of risk in the design of a gas turbine burning 100% hydrogen. Risks arise from the criticality of hydrogen characteristics: low ignition energy, wide flammability range, high burning velocity. During the design process, it is required to focus on safety aspects. All credible hazard scenarios in terms of occurrence probability shall be considered to avoid undesired catastrophic consequences. Looking to auxiliary systems, the main source of hazard can be considered the fuel gas supply system that is installed close to the gas turbine inside an enclosed space. Although fuel gas line is properly designed to avoid the possibility of hydrogen leaks inside the enclosure, the occurrence probability of a sudden leakage of tubing rupture is not impossible. The potential consequence of such remote event, combined with the higher flammability range of hydrogen, could lead to an undesired delayed ignition. Depending on several factors such as dispersed flammable mass and presence of obstacles in confined volume, an explosion could follow the ignition. In order to assess the impact of this scenario, a numerical simulation campaign for a LT16 100% H2 gas turbine enclosure was carried out with commercial code FLACS, which is a tool able to simulate a complex phenomenon like an explosion. Different gas dispersion and delayed ignition cases were analyzed to predict the consequences in terms of overpressure inside the enclosure without carrying out complex experimental tests. The present work also investigated the use of relief panels as a mitigation method to reduce the overpressure inside the enclosure. The position, shape and venting area of the panels were evaluated in terms of their effectiveness.