The adoption of three types of nozzle contours, the ramp nozzle, symmetric ramp nozzle, and symmetric swept-ramp nozzle, in chemical oxygen-iodine lasers with supersonic ejector-nozzle banks is examined by simulating the mixing and reacting flow fields numerically. The compressible Navier-Stokes equations with a detailed chemical kinetic model are solved using a full-implicit finite volume method. The numerical results show that streamwise vortices induced downstream of the base region of the nozzle array are enhanced with decreasing the length l
s of diverging region in I
2 nozzle. However, the optimum l
s which results in a high small signal gain coefficient exists for each nozzle contour, since the mixing depends also on the size and location of the streamwise vortex. Therefore, the symmetric swept-ramp nozzle which produces strong streamwise vortices even with rather large l
s is most preferable among the proposed nozzle contours. The pitot pressure in the mixing region obtained in the present calculation is approximately 10kPa which is ten times higher than that of conventional supersonic flow chemical oxygen-iodine lasers.
View full abstract