Engineering Research Equipment Grant: UV-Imaging Equipment

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A new excimer-laser based diagnostic method is being developed that should yield instantaneous two-dimensional temperature and density fields in high-temperature media such as occur in open flames or in internal combustion engines. Because the method has excellent time resolution ( 10ns), it is ideal for analysis of turbulent burning. It uses laser induced fluorescence, but with a novel approach that eliminates the problem of collisional- quenching that normally limits LIF to pressures less than 0.01 atmosphere. A powerful narrow-band UV laser excites molecules to predissociating states that are so short-lived that there is no time for quenching collisions. It is proposed to acquire a UV image intensifier and a self scanned array camera to obtain two-dimensional images of the fluorescence. One can then literally take "snapshots" of the density distribution of a single selected quantum state. By comparing the densities of two such states using two camera systems, the temperature distribution can be calculated with a single laser shot. Laser techniques are particularly promising for combined detector/computer technologies for optimization of combustion system, minimizing pollutant emissions or maximizing fuel economy for example. The method proposed here will lead us in that direction by extending LIF to a more useful pressure regime.