Influence of the Mach number of the oxidant flow on the energy and gasdynamic characteristics of a supersonic cw chemical HF laser with a radial-expansion nozzle array

An experimental investigation was made of the energy and gasdynamic characteristics of a supersonic cw chemical HF laser with three radial-expansion nozzle arrays (nozzle-sonic injector configuration) of 35 cm x 10 cm dimensions, but differing in respect of the geometric expansion ratio of the nozzles. The distributions of the Mach number, of the static pressure, and of the total pressure behind a plane shock wave were determined in the flow field of the active medium. An increase in the geometric expansion ratio of the nozzles, subject to a constant pressure at the oxidant exit, i.e. an increase in the Mach number of the oxidant flow did not increase significantly the total pressure in the flowing active medium because of large pressure losses during flow through the nozzles and in the course of mixing with hydrogen jets. An increase in the calculated Mach number of the oxidant flow from 4.2 to 5.4 reduced by 26% the specific output energy of the laser, tracking the concurrent increase of the static pressure in the lasing zone.