Features of Combustion of a Mixture of a Hydrogen Microjet with Various Gases

The objective of the present study is an experimental investigation of diffusion combustion of round microjets, i.e., mixtures of hydrogen with methane, helium, and nitrogen. It is found that the evolution of burning microjets is associated with generation of a “bottleneck flame region” close to the nozzle exit, as it was observed earlier during hydrogen combustion. Combustion of a mixture of hydrogen and methane with increasing flow velocity occurs with the transformation of the torch. At first, a torch stabilized on the nozzle is observed, then it is divided into a stabilized part in contact with the nozzle and into a raised part of the torch. The combustion process occurs in two areas. A further increase in velocity promotes the breakdown of the raised torch, but maintains combustion in the nozzle area. The results on hydrogen/methane combustion are obtained in a smaller range of the microjet velocity than those of a hydrogen microjet. Somewhat similar data are derived for other gas additives. To make combustion of gas mixtures more stable with increasing microjet velocity, one has to increase the portion of hydrogen in the gas mixture or reduce the fractions of other gas additives.