Two-dimensional UV-laser diagnostic by high-speed imaging for microgravity combustion research at Bremen drop tower

A UV-laser based non-intrusive, highly specially and temporally resolving diagnostics for experiments under microgravity condition has been accomplished at (he drop tower Bremen recently. By means of an UV-excimer laser beam, that is guided from the top of the tower into the falling drop bus, two dimensional measurements of the concentration field of selected species can be conducted with a framing rate of up to 250 pictures/ sec. The data are beeing acquired by a digital high speed camera, that is equipped with a two staged, gated intensifier. The complete picture sequence of 1500 frames (256 x 256 pixel, 8 bit resolution) is stored real time aboard the capsule in a 96MByte RAM image storage unit. For the first time, in situ data of transient combustion phenomena preceding under conditions without thermal bouancy can be obtained by laser-inducedfluorescence LIF and laser-induced-predissociationfluorescence LIPF. In the current project, the gas phase reaction of burning droplets using different hydrocarbon fuels are beeing investigated by OH-LIPF. The structure of the flame has been identified and the limitations of the technique are discussed.