The results of a computational and experimental study of the distributed transverse injection of hydrogen and methane jets into a high-speed flow are presented. The effect of jets on the flow structure in a rectangular channel of a variable cross section is determined when the dynamic head coefficient changes in the range 1.27-6. It is shown that the mixing efficiency increases with an increase in the dynamic head and, to a lesser extent, with an increase in the molecular weight of the injected gas.