On the features of diffusion combustion of hydrogen microjets

This paper presents the results of an experimental investigation of the diffusion combustion scenario of a round hydrogen microjet flowing from a cylindrical thin-walled micronozzle with a diameter of 200 μm when ignited near and at any distance from the nozzle exit. A review of the literature on the research topic is presented and a comparison is performed in dimensionless parameters based on the Reynolds number. It has been established that stabilization of the torch during the expiration of a round microjet of hydrogen is associated with heating of the nozzle by the laminar region of the flame. A hysteresis of the process of diffusion combustion of round hydrogen microjets was discovered depending on the region of ignition of the microjet (laminar or turbulent region of the torch) and on changes in the jet velocity.