Experimental investigation on optimal length of diffuser throat in directly drained CW DF/HF chemical laser

To study the effect of diffuser throat length on the starting characteristic of the directly drained CW DF/HF chemical laser(DDCL), a double-nozzle small-scale model of the DDCL gas channel was built up. A series of experiments without a secondary flow was conducted with diffusers whose throat lengths were different, and the starting and operating pressures were acquired and considered to be the criterion for judging the length of the diffuser throat. The experimental result indicates that the optimal length of the diffuser throat in the given experimental model is 17 times that of the equivalent diameter.