Study On Base-ejecting, Continuous Wave DF/HF Chemical Lasers

Compactification is one of the most important techniques for the practicability of continuous wave (CW) DF/HF chemical lasers. In this paper, a new approach to compactification was emphatically studied, which called the Base-Ejecting, CW DF/HF Chemical Laser (BECL, hereafter). By means of ejecting at base area, BECL is able to achieve two aims simultaneously within a relative small volume, first, the static pressure and temperature at the optical cavity are low enough for lasing effectively, second, the recovery pressure of lased gas is high enough to exhaust directly to ambient atmosphere. Thus, BECL is very helpful to the realization of directly exhausted, CW DF/HF chemical lasers in the future.With the help of one-dimension Steady State Theory and correlative experimental results, both the single-channel and double-channel small-scale devices of BECL gas passage were built up. Making use of the single-channel device, the effects of gasdynamic parameters of working medium and base area on the starting characteristic were studied, and the comparison between two types of base area was made. Employing the double-channel device, the effect of primary flow on the starting status of the device was discussed, and the possibility of phase change was estimated for ejecting flow nitrogen, cavity fuels and secondary diluents. In addition, the optimal length of diffuser throat was experimentally studied for the given device. All of the experiments provide references to the design of ejecting flow and structure for BECL.In order to acquire the mass flow and working schedule of lasing gases for BECL, project of working without diluents was experimentally investigated based on a small-scale DF laser, and the effect of power extraction on the flow of cavity exit was studied experimentally and theoretically. The result shows that, low power DF/HF chemical lasers can run without diluents, but suitable secondary diluent is needed for high power lasers; along with the increase of specific power, stagnation pressure, velocity, Mach number of flow at cavity exit will be increasing, and static pressure, static temperature, stagnation temperature will be decreasing.Based on the works above, a Base-Ejecting, HF chemical laser was designed and manufactured, then starting experiments and lasing experiments with vacuum were conducted. By these experiments, the starting characteristic of the laser was obtained, and output power in the vacuum experiments was improved, at the same time, every part of BECL was demonstrated one after another. Afterwards, the combination of all parts was completed, and some problems encountered in the experiments were successfully resolved. Finally, the upper limit of vacuum pressure for lasing was obtained which is 4 kPa by lasing experiments at different vacuum pressure, and experiments with ejecting flow were carried out which produced an output beam with more than 0.85 watts (about one-eighth of the power in vacuum experiment at the same flow mass) at the background of 50 kPa, thus the"Base-Ejecting"was confirmed for the ability in pressure recovery.The study of BECL is new and important, and it will be beneficial to the compactification of CW DF/HF chemical laser systems. In this paper, algebraic models and systemic experiments were investigated, and the principle of"Base-Ejecting"was deeply analyzed. Finally, the"Base-Ejecting"was confirmed for the ability in pressure recovery, and referenced data were obtained for the design of BECL, these will be very helpful to the further researches, such as optimization design of ejecting flow, structure and mass flow ratio.