This study presents the results of an experimental investigation of hydrogen diffusion combustion in a nozzle assembly with independent coaxial air supply. Two flow configurations were examined. In the first, hydrogen was injected through a cylindrical micro-nozzle and surrounded by air flowing through an annular slit. In the second, hydrogen was supplied through an annular slit, while air was delivered via a central cylindrical micro-nozzle.The paper describes the combustion regimes observed under both configurations and highlights a beneficial effect that enables sustained hydrogen combustion in the presence of a water vapor flow. Particular attention is given to the “flame trapping” phenomenon, in which combustion is confined to a narrow conical region near the nozzle exit, occurring when hydrogen emerging from the annular slit interacts with a supersonic air jet from the coaxial micro-nozzle.
Tambovtsev et al. (2025) studied this question.