To pursue the proper design criteria for gas-gas injector

the flow visualization technology with particle image velocimetry(PIV) system was adopted to investigate the mixing mechanism.The coaxial shear and swirl configurations were selected.The results show that the momentum ratio of oxygen to hydrogen prevails in the mixing process of coaxial shear injector

while the swirl numbers dominate the mixing part of coaxial swirl injector.Good mixing was gained at high momentum ratio and high swirl numbers.For the designer

the combination of high annular pressure drop and low center pressure drop is recommended for the coaxial shear injector

and the combination of low annular pressure drop and proper recess length of center post recommended for swirl injector.