Investigation of the interaction between a hypersonic air stream and a carbon dioxide aerosol

Abstract

A detailed investigation is made of the interaction between a hypersonic vibrationally excited donor gas and a carbon dioxide aerosol stream with a view to improving the energy characteristics of a gasdynamic CO2 laser. The analysis shows that rapid (within times shorter than the relaxation time of the upper active level) mixing of the evaporating aerosol and the vibrationally excited gas is possible as a result of this interaction. For a planar flow geometry with symmetrical aerosol injection, the transverse dimension of the active medium may be 20 cm for a hypersonic nozzle with a throat cross section ~1 mm high. The conditions under which there were no gas-dynamic perturbations in the mixing zone and the active medium was optically homogeneous were determined. A CO2 aerosol generator was developed with a solid particle size distribution function close to the optimal. An experimental investigation was made of the interaction between the streams using a system with a conical hypersonic nozzle for the air and perpendicular injection of the aerosol. The experimental results broadly agreed with the theoretical predictions. A CO2 laser radiation gain close to the calculated value was obtained in the excited air-carbon dioxide aerosol mixing zone.