For the gelled JP-4 of an oil-in-water emulsion type which includes 96∼99% oil concentration by volume as an internal phase and has the drainage temperature higher than 70°C in confined vessel, the flame spreading aspects with a pool combustion were observed by taking movie, and the measurement of temperatures, on and above the surface of the gel from the time when the flame is coming over to the time when it has passed away, was carried out with thermocouples fixed in place.
While the flame is spreading on the gelled JP-4, an advance liquid flow ahead of the flame can be found in case of the initial gel temperatures lower than the apparent flash points (26∼35°C) measured by means of open cup method. This liquid flow invades on to the surface of the virgin gel, issued from the upstream region covered already with luminous flame, and is not formed by radiative and conductive heat transfer from the flame pillar to the virgin gel surface. In view point that the temperatures of foregoing liquid flow is 10∼20°C at the initial level of gel surface and the flash point of the original JP-4 is -23°C, a large part of the low hydrocarbon fractions seem to have burned in the flame zone before streaming out on the virgin gel surface. The behavior of liquid flow was observed in detail with fine aluminum powders sowed in the vicinity of the ignition position. As the result, it is found that in the foregoing liquid flow there is a strong convection due to temperature gradient. Thus, the covering of the liquid flow on the virgin gel plays a role to reduce the drainage rate of the gel, protecting the gel surface from being exposed in air in the place close to hot flame, and the flame spreading velocity can be suppressed by one-tenth to one-twentieth, compared to that of the original JP-4.