There is limited published research on the effect of water sprays on hydrogen deflagrations and deflagration-to-detonation transition, and more extensive data on water spray effects on hydrocarbon gas explosions. The results show the benefits, where there are benefits, to be highly scenario dependent. For example, Carlson et al. (Atomics International report, 1973) described hydrogen detonation tube testing with and without a 500-micrometer drop diameter water spray. They found the water spray prevented detonations at hydrogen concentrations of 20% to 24%, but not at 28%. Drop size is critical since the benefits of sprays depend on the droplets breaking up and partially vaporizing in advance of the propagating flame front. If the droplets do not break up, they induce turbulence effects that can significantly increase flame speeds and exacerbate hydrogen deflagrations. Both the detonation ability and deflagration scenarios are discussed in Technical Aspects of Hydrogen Control and Combustion in Severe Light-Water Reactor Accidents, National Academy Press, 1987. 

The effects of water deluge nozzle spray on methane and propane deflagrations in vented simulated offshore platform enclosures were investigated in Phase 2 (1998 report) of a European test program called Blast and Fire Engineering for Topside Structures. Comparisons of test results in highly obstructed enclosures with and without the deluge spray showed lower pressures with the deluge spray. However, the sprays did increase the initial flame speeds, which can be either good, if the flame induced velocities are large enough to cause droplet breakup, or bad, if the droplets remain intact. The authors conclude that deluge sprays prevent runaway flame acceleration in situations with inherently high flame speeds but will not be effective in applications where only low flame speeds are generated. Thus, the spray would be expected to be effective for near-stoichiometric H2-air mixtures, but detrimental for concentrations in the range of 8% to perhaps 13%.