Investigation of Non-Premixed Hydrogen-Oxygen Impinged Jet Flame Under Steam Dilution

Abstract

Large-scale electric power generation with hydrogen-fired gas turbines is key to the realization of zero-emission society. One challenge of premixed hydrogen combustion is the flashback associated with high burning velocity. On the other hand, non-premixed (diffusion) hydrogen-air combustion produces high level of NOx due to the high flame temperature. In order to reduce NOx, a semi-closed gas turbine cycles employing the hydrogen-oxygen combustion has been proposed. In the present study, we developed a non-premixed hydrogen-oxygen burner with sub-millimeter nozzles to form two oxygen jets impinging on the hydrogen jet at an acute angle. Compared to conventional burners with co-flow jets, forced mixing of hydrogen and oxygen occurs due to the impingement. It is expected that the flame holding as well as the combustion efficiency can be improved. High-speed Schlieren and OH* chemiluminescence images of the hydrogen flame with/without the oxygen jet impingement in a pressure vessel were captured to examine the instantaneous flame structure. Flammability and flame structure have been investigated at various jet velocity and pressure conditions. It was found that without the oxygen jet impingement the flame becomes longer with increasing the hydrogen velocity. Lifted flames were observed at the velocity over 200 m/s. The lift position moves gradually downstream with further increasing the velocity. On the other hand, with increasing the velocity of the oxygen jet impinged to the hydrogen jet, a V-shaped flame front stabilized at the impinging position was observed. It was also found that flame holding is improved at high pressure. Based on the impinged jet flame concept, prototype multi-cluster burners with sub-millimeter nozzle arrays were designed and fabricated using the Inconel alloy 3D printing technology.