Vaporization of Liquid-Air Droplets by High-Power Laser Beams

The interaction between a high-power laser beam and a moving cloud of vaporizing droplets was considered theoretically. The study was performed to assess partially the feasibility of a new concept of generating an ultrahigh-total-enthalpy flow, as was recently proposed by Johnson and von Ohain. The spectral absorption coefficient of liquid air was determined at the fundamental vibration-rotation frequencies of liquid nitrogen and oxygen. A perturbation solution was sought for a small but arbitrary variation in the Velocity of the moving droplets. The first-order correction to the uniform-velocity solution of Glickler has been explicitly carried out in closed form. Results indicate that the concept of vaporizing liquid-air droplets by laser beams is feasible, although the power required, according to our present knowledge of the radiative properties of liquid air, is high. The idea of mixing strongly absorbing to reduce the total power required appears quite attractive.