Limits for hydrogen leaks that can support stable flames

Quenching and blowoff limits of hydrogen diffusion flames on small burners were observed. Four burner types, with diameters as small as 8 μm, were considered: pinhole burners, curved-wall burners, tube burners, and leaky fittings. In terms of mass flow rate, hydrogen had a lower quenching limit and a higher blowoff limit than either methane or propane. Hydrogen flames at their quenching limits were the weakest flames recorded to date, with mass flow rates and heat release rates as low as 3.9 μg/s and 0.46 W. The quenching limit for a hydrogen flame at a 6 mm leaky compression fitting was found to be 28 μg/s. This limit was independent of supply pressure (up to 131 bar) and about an order of magnitude lower than the corresponding limits for methane and propane.