Combustion of round hydrogen microjet in a cocurrent air flow with nanopowder

In the present paper we show our recent experimental data on diffusion combustion of a round hydrogen microjet in a cocurrent flow of air mixed with nanoparticles of TiO2. The hydrogen microjet is emanated from a round micronozzle which is surrounded by a coaxial slit to produce the cocurrent flow. Combustion events found in the present conditions are similar to those observed in the previous studies on diffusion combustion of hydrogen microjets at subsonic and supersonic velocities. In a subsonic range, the so-called "bottleneck-flame region" is generated close to the nozzle exit, while in high-speed conditions the flame separates from the nozzle. At increasing velocity of both the hydrogen microjet and the cocurrent flow, the "bottleneck-flame region" is still found and the combustion becomes more intense. The "bottleneck-flame region" is suppressed at the microjet velocity approaching transonic values.