IGNITION PROBLEMS IN SCRAMJET TESTING

Ignition of H-2 in heated air containing H2O, radicals, and dust was i nvestigated for scramjet testing. Using a reduced kinetic model for H- 2-O-2 systems, the effects of H2O and radicals in nozzles are discusse d in relation to engine testing with vitiation heaters. Analysis using linearized rate-equations suggested that the addition of O atoms was 1.5 times more effective than the addition of H atoms for ignition. Th is result can be applied to the problem of premature ignition caused b y residual radicals and to plasma-jet igniters. Thermal and chemical e ffects of dust, inevitable in storage air heaters, were studied next. The effects of heat capacity and size of dust were expressed in terms of an exponential integral function. It was found that the radical ter mination on the surface of dust produces an effect equivalent to heat loss. The inhibition of ignition by dust may result, if the mass fract ion of dust becomes 10(-3).