The paper describes the design and operating principle of a valve designed for testing the prototypes of key elements of a massive gas injection system: a seat and a supersonic nozzle. The calculation results for supersonic nozzle parameters close to optimal for the selected valve design have been presented. The simulation of gas flows through the seat and nozzle was carried out, the parameters of the formed jet at the injection system outlet in the nozzle near field were calculated. The choice of the "stepped" nozzle profile for the first tests was justified. An assessment was made of the requirements for the accuracy of manufacturing prototype nozzles.