Continuous chemical HF laser with a modified radially expanding nozzle unit

Abstract

621.378:535We have determined experimentally the energy and spectral characteristics of a supersonic continuous chemical HF laser (oscillator) with a modified radially expanding nozzle unit operating according to the "nozzle-injector-injector" scheme of mixing reactants based on a new method of obtaining oxidizing gas. The practical realization of measures to decrease the heat loss and the loss of fluorine atoms, as well as the optimization of the mode of operation of the modified laser, permitted a 30% increase in its radiation power compared to the base oscillator equipped with a nozzle unit operating according to the "nozzle-injector" mixing scheme. Ways of further enhancement of the energy characteristics of the HF laser radiation are proposed.Introduction. The experimental study of the small-sized supersonic continuous chemical HF laser with a radially expanding nozzle unit operating according to the "nozzle-injector" scheme of mixing reactants [1] demonstrated a very strong dependence of the energy parameters of this laser on the gas-dynamic characteristics of the active medium. It was shown that the process of laser radiation generation involves only that part of the active medium that has fairly low values of the static pressure and temperature. Obviously, the creation of conditions for involving the entire volume of the active medium in the generation process is promising for further enhancement of HF laser energy parameters. This can be achieved, in particular, by adding an additional quantity of inert diluent to the active medium of the laser.In [2], we proposed a method for such addition. This method was realized in practice in an autonomous HF laser with a modified radially expanding nozzle unit of original design operating according to the "nozzle-injector-injector" scheme of mixing the reactants. The modified nozzle unit is equipped with a special injector for injecting a cold inert diluent at the inlet to the nozzle and thus realizing the above mixing scheme. Such injection permits separated supply of atomic fluorine and inert diluent into the nozzle, as well as two-region mixing of reactants with subsequent low-temperature flow of the oxidizing gas (mixture F+DF+He) in the supersonic parts of the nozzles.We have modified two available models of the laser under consideration. One of them is a small-size laser (the size of the outlet section of the nozzle unit is 18 × 3.9 cm) with a total mass flow of reactants m Σ 30 g ⁄ s. The other model ia a medium-size laser (the outlet section of the nozzle unit is 35 × 10 cm) with a total mass flow of reactants m Σ 140 g ⁄ s.The results of experiments with the small-size laser with a design power N = 5 kW [2, 3] have shown convincingly that the use of the new method of obtaining oxidizing gas makes it possible to enhance considerably the HF laser energy characteristics. For example, if 95% of the inert diluent (helium) is transferred from the first mixing zone (combustion chamber) to the second one (inlet part of the nozzles), then the laser power can increa...