Characterization of high-pressure hydrogen leakages

Reduction of gas turbine (GT) carbon emissions relies on a strategy for fueling the engines with pure or blended hydrogen. The major technical challenges to solve are (i) the adjustments to the engine and in particular the combustion chamber and (ii) a series of issues to solve to guarantee safe operations. In fact, compared to natural gas, hydrogen fueling implies higher risks of explosion in case of leak in the turbine enclosure and a more careful design of the ventilation system. Thus, a deeper comprehension of hydrogen leak scenarios is needed to adjust the safe design strategy of the enclosure. To this aim, a series of numerical investigations was carried out to understand how different methane–hydrogen blends (from pure methane to pure hydrogen) behave when leaking from a pipeline with fuel pressure that span from 1.5 to 4.5 MPa. The different fuel blends' leaks in form of underexpanded jets were studied under different cross-flow ventilation conditions, with ventilation velocity spanning from 0 m/s to 5 m/s. When compared to pure methane, the outcome is a three times longer penetration distance for pure hydrogen axisymmetric flammable clouds, whereas in cross-flow conditions a more complex three-dimensional behavior was found, potentially opening a safety-related concerns discussed in the paper.