Multiline hydroxyl tagging velocimetry measurements in reacting and nonreacting experimental flows

A compact micro-lens optical system is developed that produces a 7A7 multi-line optical grid for Hydroxyl Tagging Velocimetry (HTV) and generates at least 49 resolvable velocity vectors. Single-photon photodissociation of ground-state H2O by a ~193-nm ArF excimer laser awritesa a 7A7 beam molecular grid with very long gridlines of superequilibrium OH and H photoproducts in either room air flowfields or in H2-air flames due to the presence of H2O vapor. The displaced OH tag line positions are revealed through fluorescence by A 2 ? + (v?=0)?X 2 ? i (v?=0) OH excitation using a ~308-nm pulsed frequency-doubled dye laser. Time-of-flight analysis software determines the instantaneous velocity field in either an air nozzle or in a hydrogen/air flame. The OH tag lifetime is measured and compared to theoretical predictions using detailed chemistry. The lifetime of the OH tag is significantly enhanced by the presence of O atoms from 193-nm photodissociation of O2.