Four tasks were conducted during this research effort. The intent of Task A was to determine how close an ignition source must be to a hydrogen leak to cause ignition of the leak and to compare that distance to the positions of 4%2hydrogen. This was done by constructing a device to produce a measured 566 liters/min (20 SCFM) leak horizontally through the center of an aluminum clad eight-foot by eight-foot wall. The pure hydrogen leak was allowed to continue until it produced a relatively steady-state plume. The concentration of hydrogen was measured at various locations and compared to a computational fluid dynamics model of the plume. Electric arcs were utilized at various locations to determine those locations that would produce full ignition of the leak. The experimentally determined location, farthest from the wall, at which the leak could be ignited was then compared to the computational and experimentally determined location of 4%2hydrogen-air mixture in the plume. It was found that the maximum horizontal distance, from the horizontal hydrogen leak at Mach=0.10, at which the leak could be ignited was 57 inches which was significantly closer than the location that contained 4%2hydrogen (77 inches). The maximum horizontal distance to ignite a Mach=0.20 leak was 47 inches which was significantly closer than the location that contained 4%2hydrogen (88 inches). It was concluded that ignition tests of hydrogen leaks at higher flow rates should be conducted to determine if the inability to ignite the leak at a location of 6%2hydrogen concentration extends to high flow rates. The intent of Task B was to determine the characteristics of ignition of lean mixtures of hydrogen and air flowing in ducts. Homogeneous mixtures of hydrogen and air were passed down a 6.1 m (20 foot) duct and ignition was attempted at various flow rates (different Reynolds numbers) and with varied electrode gap sizes and spark energies. It was found that the lean limit of combustion is a much stronger function of electrode gap size than of Reynolds number. Data was collected indicating that if electrode gap size was held constant, a higher Reynolds number inhibits ignition for low hydrogen concentrations (less than 8%2 but promotes ignition at higher concentrations. To verify the applicability of the range of gap sizes used a variety of electrical appliances that produce electric arcs were tested. It was found that the electrical appliances tested required hydrogen air mixtures of 6%2to sometimes more than 10%2to allow ignition. It was concluded that it would be useful if a classification service such as Underwriter's Lab developed tests to determine what concentration of hydrogen a given electrical appliance can ignite. The intent of Task C was to determine the grounding needs of electrolyzers or fuel cells for use in residential garages. A survey was conducted, by contacting manufacturers, and it was found that fuel cells should share a common ground with the house circuit. The intent of Task D was to determine hazards produced by electrical shorts in conjunction with portable fuel cells. A survey was conducted, by contacting manufacturers, and it was found that all the manufacturers include short protection on their units.
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